EP3770291B1 - Steel - Google Patents
Steel Download PDFInfo
- Publication number
- EP3770291B1 EP3770291B1 EP19772012.1A EP19772012A EP3770291B1 EP 3770291 B1 EP3770291 B1 EP 3770291B1 EP 19772012 A EP19772012 A EP 19772012A EP 3770291 B1 EP3770291 B1 EP 3770291B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- steel
- content
- ferrite
- fraction
- bainite
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 229910000831 Steel Inorganic materials 0.000 title claims description 103
- 239000010959 steel Substances 0.000 title claims description 103
- 229910000859 α-Fe Inorganic materials 0.000 claims description 69
- 229910001563 bainite Inorganic materials 0.000 claims description 38
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 13
- 239000012535 impurity Substances 0.000 claims description 6
- 229910052750 molybdenum Inorganic materials 0.000 claims description 6
- 229910052758 niobium Inorganic materials 0.000 claims description 5
- 229910052749 magnesium Inorganic materials 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- 229910052796 boron Inorganic materials 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 229910052714 tellurium Inorganic materials 0.000 claims description 3
- 229910052721 tungsten Inorganic materials 0.000 claims description 3
- 229910052726 zirconium Inorganic materials 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- 229910052745 lead Inorganic materials 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 229910052710 silicon Inorganic materials 0.000 claims description 2
- 229910052797 bismuth Inorganic materials 0.000 claims 2
- 229910052760 oxygen Inorganic materials 0.000 claims 1
- 229910052698 phosphorus Inorganic materials 0.000 claims 1
- 229910052717 sulfur Inorganic materials 0.000 claims 1
- 230000000694 effects Effects 0.000 description 50
- 238000012360 testing method Methods 0.000 description 30
- 238000005266 casting Methods 0.000 description 28
- 238000001816 cooling Methods 0.000 description 28
- 238000005096 rolling process Methods 0.000 description 21
- 238000005255 carburizing Methods 0.000 description 14
- 229910001562 pearlite Inorganic materials 0.000 description 14
- 238000010438 heat treatment Methods 0.000 description 13
- 238000004519 manufacturing process Methods 0.000 description 13
- 239000013078 crystal Substances 0.000 description 12
- 238000005259 measurement Methods 0.000 description 11
- 238000000034 method Methods 0.000 description 11
- 239000000126 substance Substances 0.000 description 10
- 150000001875 compounds Chemical class 0.000 description 8
- 238000007670 refining Methods 0.000 description 8
- 238000012937 correction Methods 0.000 description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- 238000005204 segregation Methods 0.000 description 7
- 229920006395 saturated elastomer Polymers 0.000 description 6
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 5
- 229910001566 austenite Inorganic materials 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 238000005275 alloying Methods 0.000 description 3
- 238000005452 bending Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 238000003754 machining Methods 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 230000000087 stabilizing effect Effects 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000005242 forging Methods 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910052765 Lutetium Inorganic materials 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000005256 carbonitriding Methods 0.000 description 1
- 238000010273 cold forging Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000013256 coordination polymer Substances 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/06—Surface hardening
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
- C21D1/76—Adjusting the composition of the atmosphere
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/007—Heat treatment of ferrous alloys containing Co
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/02—Pretreatment of the material to be coated
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/20—Carburising
- C23C8/22—Carburising of ferrous surfaces
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/28—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases more than one element being applied in one step
- C23C8/30—Carbo-nitriding
- C23C8/32—Carbo-nitriding of ferrous surfaces
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/80—After-treatment
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
- C21D1/58—Oils
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2261/00—Machining or cutting being involved
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
Definitions
- the present invention relates to steel.
- gears for use in automobiles, construction machinery, industrial machinery, and the like are generally used after receiving carburizing hardening after machining.
- quietness during operation has been more strongly demanded than before, and thus an increase in the dimensional accuracy of gears, especially the dimensional accuracy of teeth, has been demanded.
- the dimensional accuracy of gear teeth is attributable to deformation associated with heat treatment during carburizing hardening (hereinafter referred to as thermal strain). Since this thermal strain varies and is not uniform for each gear tooth, a symmetrical shape is lost in the same gear, and thus vibrations are created during use, thus losing quietness. Accordingly, demands exist for stabilizing thermal strain on gear teeth so as to provide a symmetrical shape.
- Patent Document 1 discloses a technology for providing steel having excellent cold forgeability and temper softening resistance. However, Patent Document 1 does not provide a technology for stabilizing thermal strain on gear teeth during carburizing hardening, which is an object of the present invention.
- Patent Document 2 discloses a technology for providing a hot-rolled steel bar or wire rod composed of a ferrite-pearlite structure, ferrite-pearlite-bainite structure, or ferrite-bainite structure, wherein the standard deviation of ferrite fractions at the time when randomly selected 15 viewing fields of a transverse cross-section are observed and measured with the area per one viewing field being 62500 ⁇ m 2 is 0.10 or less; and when a region from the surface to one-fifth of the radius and a region from the center to one-fifth of the radius in the transverse cross-section are observed, in each of the regions, the amount of Al precipitating as AlN is 0.005% or less, and the density in terms of the number of AlN having a diameter of 100 nm or larger is 5/100 ⁇ m 2 or less.
- Patent Document 2 uses a pearlite structure to reduce the standard deviation of ferrite fractions. That is to say, according to the technology of Patent Document 2, it is not possible to sufficiently reduce the standard deviation of ferrite fractions while controlling the structures so as not to substantially include pearlite.
- An object of the present invention is to provide steel that stabilizes thermal strain on gear teeth during carburizing hardening.
- thermal strain on the teeth of a gear manufactured by carburizing hardening can be stabilized.
- Figure 1 is a schematic cross-sectional view of steel for explaining the positions for measuring the average ferrite fraction and the standard deviation of the ferrite fraction.
- the present inventors have conducted diligent research on a method for stabilizing thermal strain on the teeth of a gear after carburizing hardening. As a result, it was found that the thermal strain is stabilized by increasing the uniformity of structures in a region of steel that becomes teeth after machining. Accordingly, concerning a method for making uniform the structures of a region corresponding to the gear teeth in steel, the inventors further investigated the effect of changing the chemical components of steel and the manufacturing method. As a result, it was found that by configuring the steel components to be in predetermined ranges and then controlling the casting method and the post-rolling cooling rate, the structures of a region corresponding to the gear teeth in steel can be uniform.
- the cross-sectional area of casting, the casting rate, and the average cooling rate of the surface from the beginning of casting to the correction point are controlled in a combined manner. This makes it possible to homogenize the cast structures of a region in a bloom that eventually becomes gear teeth. Moreover, concerning the control of the post-rolling cooling rate, the cooling rate of the steel surface is controlled. This makes it possible to homogenize the structures of a region in steel that corresponds to the gear teeth.
- the C content affects the hardness of the non-carburized portion of a gear. In order to ensure a required hardness, the C content is 0.17% or more. On the other hand, when the C content is excessive, the hardness of the non-carburized portion after carburization is high, resulting in poor impact strength, and thus the C content is 0.21 % or less.
- the preferable lower limit of the C content is 0.175%, 0.18%, 0.185%, or 0.19%.
- the preferable upper limit of the C content is 0.205%, 0.200%, 0.195%, or 0.19%.
- Si is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel.
- the Si content needs to be within the range of 0.40 to 0.60%.
- the preferable lower limit of the Si content is 0.42%, 0.45%, 0.48%, or 0.50%.
- the preferable upper limit of the Si content is 0.58%, 0.55%, 0.53%, or 0.51%.
- Mn is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel.
- the Mn content needs to be 0.25% or more.
- the Mn content is 0.50% or less.
- the preferable lower limit of the Mn content is 0.27%, 0.30%, 0.32%, or 0.35%.
- the preferable upper limit of the Mn content is 0.48%, 0.45%, 0.42%, or 0.40%.
- Cr is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel.
- the Cr content needs to be within the range of 1.35 to 1.55%.
- the preferable lower limit of the Cr content is 1.37%, 1.40%, 1.42%, or 1.45%.
- the preferable upper limit of the Cr content is 1.53%, 1.50%, 1.49%, or 1.47%.
- Mo is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel.
- Mo When Mo is contained in steel together with Nb, which will be described below, Mo suppresses pearlite transformation by increasing the hardenability of steel, and also suppresses coarse austenite crystal grains during the heating of steel. This makes it possible to suitably control hardenability, and obtain the desired bainite structure by suppressing martensite transformation.
- the Mo content is excessive, the amount of ferrite in steel is insufficient, and the amounts of bainite and the like are increased, resulting in poor workability. In order to obtain the above-described effect, the Mo content needs to be within the range of 0.20 to 0.40%.
- the preferable lower limit of the Mo content is 0.22%, 0.25%, 0.28%, or 0.30%.
- the preferable upper limit of the Mo content is 0.38%, 0.35%, 0.32%, or 0.30%.
- S forms MnS in steel, thereby increasing the machinability of steel.
- a S content comparable to that of commonly used steel for machine structural use is needed.
- the S content needs to be within the range of 0.010 to 0.05%.
- the preferable lower limit of the S content is 0.012%, 0.014%, 0.020%, or 0.022%.
- the preferable upper limit of the S content is 0.035%, 0.030%, 0.028%, or 0.025%.
- N has a crystal grain refining effect by forming compounds with Al, Ti, V, Cr, and the like, and thus needs to be contained in an amount of 0.005% or more.
- N exceeds 0.020%, compounds are coarse, and the crystal grain refining effect cannot be obtained.
- the N content needs to be within the range of 0.005 to 0.020%.
- the preferable lower limit of the N content is 0.0055%, 0.0060%, 0.007%, or 0.010%.
- the preferable upper limit of the N content is 0.018%, 0.015%, 0.012%, or 0.010%.
- Al is an element effective for the deoxidation of steel, and is an element that binds to N to form nitride and refine crystal grains.
- the preferable lower limit of the Al content is 0.004%, 0.007%, 0.010%, or 0.020%.
- the preferable upper limit of the Al content is 0.080%, 0.050%, 0.040%, or 0.030%.
- Nb is an element that produces fine compounds with C and N in steel and provides a crystal grain refining effect. Also, Nb when contained in steel together with Mo exerts the above-described synergistic effect (the effect of suppressing pearlite transformation and martensite transformation). When the Nb content is less than 0.001%, this effect is insufficient. When the Nb content exceeds 0.030%, carbonitride is coarse, and this effect cannot be sufficiently obtained. For the above reason, the Nb content needs to be 0.001 to 0.030%. The preferable lower limit of the Nb content is 0.005%, 0.010%, 0.012%, or 0.015%. The preferable upper limit of the Nb content is 0.028%, 0.025%, 0.022%, or 0.020%.
- the O content forms oxide in steel and acts as an inclusion to reduce fatigue strength, and thus the O content is limited to 0.005% or less.
- the preferable upper limit of the O content is 0.003%, 0.002%, 0.0015%, or 0.001%. Since a smaller O content is more preferable, the lower limit of the O content is 0%. However, removing O more than necessary results in increased manufacturing costs. Accordingly, the lower limit of the O content may be 0.0001 %, 0.0002%, 0.0005%, or 0.0008%.
- the P content is limited to 0.03% or less.
- the preferable upper limit of the P content is 0.025%, 0.023%, 0.020%, or 0.015%. Since a smaller P content is more preferable, the lower limit of the P content is 0%. However, removing P more than necessary results in increased manufacturing costs. Accordingly, the substantial lower limit of the P content is usually about 0.004% or more.
- the lower limit of the P content may be 0.005%, 0.007%, 0.010%, or 0.012%.
- Steel according to the present invention may further contain one or two or more selected from the group consisting of Ni, Cu, Co, W, V, Ti, and B in place of a part of Fe in order to increase hardenability or the crystal grain refining effect.
- the lower limit when these elements are not contained is 0%.
- Ni is an element effective for imparting necessary hardenability to steel.
- the Ni content is preferably 0.01% or more.
- the Ni content exceeds 3.0%, the amount of residual austenite after hardening is large, resulting in poor hardness.
- the Ni content is 3.0% or less and more preferably 0.01 to 3.0%.
- the upper limit of the Ni content is more preferably 2.0% and even more preferably 1.8%.
- a more preferable lower limit of the Ni content is 0.1% and more preferably 0.3%.
- the Cu is an element effective for increasing the hardenability of steel.
- the Cu content is preferably 0.01% or more.
- the Cu content exceeds 1.0%, hot ductility is impaired. Accordingly, the Cu content is 1.0% or less and more preferably 0.01 to 1.0%.
- a more preferable lower limit of the Cu content is 0.05% and even more preferably 0.1%.
- Co is an element effective for increasing the hardenability of steel.
- the Co content is preferably 0.01% or more.
- the Co content exceeds 3.0%, the effect is saturated. Accordingly, the Co content is 3.0% or less and more preferably 0.01 to 3.0%.
- a more preferable lower limit of the Co content is 0.05% and even more preferably 0.1%.
- W is an element effective for increasing the hardenability of steel.
- the W content is preferably 0.01% or more.
- the W content exceeds 1.0%, the effect is saturated. Accordingly, the W content is 1.0% or less and more preferably 0.01 to 1.0%.
- a more preferable lower limit of the W content is 0.05% and even more preferably 0.1 %.
- V is an element that produces fine compounds with C and N in steel and provides a crystal grain refining effect.
- the V content is preferably 0.01 % or more.
- the V content exceeds 0.3%, compounds are coarse, and the crystal grain refining effect cannot be obtained. Accordingly, the V content is 0.3% or less and more preferably 0.01 to 0.3%.
- a more preferable lower limit of the V content is 0.1% and even more preferably 0.15%.
- Ti is an element that produces fine compounds with C and N in steel and provides a crystal grain refining effect.
- the Ti content is preferably 0.001% or more.
- the Ti content exceeds 0.3%, the effect is saturated.
- the Ti content is 0.3% or less and more preferably 0.001 to 0.3%.
- a more preferable upper limit of the Ti content is 0.25% and even more preferably 0.2%.
- B functions to suppress the grain boundary segregation of P.
- B also has the effect of increasing grain boundary strength and intragranular strength and the effect of increasing hardenability, and these effects increase the fatigue strength of steel.
- the B content is preferably 0.0001% or more.
- the B content exceeds 0.005%, the effect is saturated.
- the B content is 0.005% or less and preferably 0.0001 to 0.005%.
- a more preferable upper limit of the B content is 0.0045% and even more preferably 0.004%.
- the chemical composition of steel according to the present invention may further contain one or two or more selected from the group consisting of Pb, Bi, Ca, Mg, Zr, Te, and rare earth elements (REMs) in place of a part of Fe.
- Pb Pb
- Bi Bi
- Ca Ca
- Mg Mg
- Zr Te
- REMs rare earth elements
- Pb is an element that increases machinability by being molten and embrittled during cutting.
- the Pb content is preferably 0.01% or more.
- a more preferable lower limit of the Pb content is 0.05% and even more preferably 0.1 %.
- the preferable upper limit of Pb is 0.4% and even more preferably 0.3%.
- Bi is an element that increases machinability due to finely dispersed sulfide.
- the Bi content is preferably 0.0001 % or more.
- the Bi content is 0.5% and more preferably 0.0001 to 0.5%.
- a more preferable lower limit is 0.0001 % and even more preferably 0.001%.
- the preferable upper limit of Bi is 0.4% and even more preferably 0.3%.
- the Ca is an element effective for the deoxidation of steel and reduces the Al 2 O 3 content in oxide.
- the Ca content is preferably 0.0001 % or more.
- the Ca content exceeds 0.01 %, a large amount of Cacontaining coarse oxide appears and causes a shortened rolling fatigue life.
- the Ca content needs to be within the range of 0.0001 to 0.01%.
- the preferable lower limit of the Ca content is 0.0003% and more preferably 0.0005%.
- the preferable upper limit of the Ca content is 0.008% and more preferably 0.006%.
- Mg is a deoxidizing element and produces oxide in steel. Moreover, Mgbased oxide formed by Mg likely becomes a nucleus for crystallization and/or precipitation of MnS. Also, the sulfide of Mg makes MnS spherical by becoming a complex sulfide of Mn and Mg. Thus, Mg is an element effective for controlling the dispersion of MnS and improving machinability. In order to obtain this effect, the Mg content is preferably 0.0001% or more. However, when the Mg content exceeds 0.01%, a large amount of MgS is produced, and the machinability of steel decreases.
- the Mg content needs to be 0.01% or less.
- the preferable upper limit of the Mg content is 0.008% and more preferably 0.006%.
- the preferable lower limit of the Mg content is 0.0005% and more preferably 0.001%.
- Zr is a deoxidizing element and forms oxide. Moreover, Zr-based oxide formed by Zr likely becomes a nucleus for crystallization and/or precipitation of MnS. Thus, Zr is an element effective for controlling the dispersion of MnS and improving machinability.
- the Zr content is preferably 0.0001% or more. However, when the amount of Zr exceeds 0.05%, the effect is saturated. Thus, in order to obtain the above-described effect by containing Zr, the Zr content is 0.05% or less and more preferably 0.0001 to 0.05%.
- the preferable upper limit of the Zr content is 0.04% and more preferably 0.03%.
- the preferable lower limit of the Zr content is 0.0005% and more preferably 0.001%.
- Te promotes the spheroidization of MnS and thus improves the machinability of steel.
- the Te content is preferably 0.0001% or more.
- the Te content is 0.1% or less and more preferably 0.0001 to 0.1%.
- the preferable upper limit of the Te content is 0.08% and more preferably 0.06%.
- the preferable lower limit of the Te content is 0.0005% and more preferably 0.001%.
- Rare earth element 0 to 0.005%
- Rare earth elements are elements that promote the production of MnS by producing sulfide in steel and this sulfide becoming a precipitation nucleus for MnS, and improve the machinability of steel.
- the total amount of rare earth elements is preferably 0.0001 % or more.
- the total amount of rare earth elements exceeds 0.005%, sulfide is coarse, reducing the fatigue strength of steel. Accordingly, the total amount of rare earth elements is 0.005% or less and more preferably 0.0001 to 0.005%.
- the preferable upper limit of the total amount of rare earth elements is 0.004% and more preferably 0.003%.
- the preferable lower limit of the total amount of rare earth elements is 0.0005% and more preferably 0.001%.
- the rare earth element as used herein is a collective term referring to 17 elements including 15 elements from lanthanum (La) with atomic number 57 to lutetium (Lu) with atomic number 71 in addition to yttrium (Y) and scandium (Sc) in the periodic table.
- the amount of rare earth elements means the total amount of one or two or more of these elements.
- Steel according to the present invention contains the above-described alloying components, and the balance includes Fe and impurities. Elements other than the above-described alloying components are allowable in steel as impurities from raw materials and manufacturing equipment as long as the amounts thereof do not affect the properties of steel.
- the region of steel corresponding to the gear teeth is a region including a part from the tooth tip to the tooth root of a gear after forging or cutting, and is a region satisfying 0.7R ⁇ r ⁇ 0.9R in rolled steel, wherein r is the distance from the center of the cross-section of steel that is perpendicular to the length direction, and R is a circle equivalent radius in the cross-section of steel that is perpendicular to the length direction of steel.
- the uniform structures suitable for improvement of thermal strain are structures including ferrite and bainite, and that the structure fractions are in suitable ranges.
- the thermal strain was stabilized when, in the 0.7R ⁇ r ⁇ 0.9R region, the average value of the ferrite fraction (average fraction) in terms of area ratio is in the range of 40 to 70%, the total of the average fractions of structures other than ferrite and bainite is 0% or more and 3% or less on average, the balance includes bainite, and the standard deviation of the average ferrite fraction in the 0.7R ⁇ r ⁇ 0.9R range is 4% or less, as determined by the measurement method described below.
- a fraction with respect to a metal structure means the average value of a structure fraction (unit: area%) in the cross-section of steel determined by the means described below.
- the "fraction” does not mean an average value in the entirety of a cross-section but means the fraction in each measured visual field, as will be described below.
- the preferable lower limit of the ferrite fraction is 42% and more preferably 45%.
- the preferable upper limit of the ferrite fraction is 68% and more preferably 65%.
- a lower standard deviation of the ferrite fraction in the 0.7R ⁇ r ⁇ 0.9R range is more preferable, and thus the lower limit is 0%.
- the preferable upper limit of the standard deviation of the ferrite fraction in the 0.7R ⁇ r ⁇ 0.9R range is 3.5% and more preferably 3%.
- "bainite” means, among the structures obtained by heating steel to form an austenite single phase structure and then cooling it to room temperature by continuous cooling, a structure excluding a ferrite structure, a pearlite structure, and a martensite structure, and means a collective term referring to an upper bainite structure, a lower bainite structure, or a mixed structure of an upper bainite structure and a lower bainite structure.
- pearlite is contained in the structures of steel according to the present invention because it deteriorates carburizing hardenability.
- steel composed of mixed structures of ferrite, pearlite, and bainite is carburizing-hardened, the austenite crystal grain structure in a region corresponding to the teeth becomes non-uniform during heating. Accordingly, deformation after carburizing hardening, i.e., thermal strain, is increased.
- the area ratio of pearlite needs to be limited as much as possible.
- the total of structures other than ferrite and bainite is specified to be 0% or more and 3% or less.
- steel according to the present invention is steel having a ferrite-bainite structure.
- the points where the circumferences having 0.7R + 0.25 mm, 0.8R, and 0.9R - 0.25 mm intersect straight lines radially dividing, from the center of the cross-section of steel, the cross-section into eight equal parts (central angle 45°) were regarded as measurement points, and rectangular regions having 0.5 mm ⁇ 1 mm 0.5 mm 2 were regarded as measurement regions such that the respective measurement points were at the centers of the rectangles. There are 24 measurement regions.
- the ferrite fraction and the standard deviation of the ferrite fraction in the 0.7R ⁇ r ⁇ 0.9R range were determined by observation using an optical microscope with respect to a sample obtained by mirror-polishing the cross-section of steel and corroding it with nital.
- each measurement region of the nitalcorroded sample was visually observed, and in each measurement region, the 0.5 mm 2 area in an image captured at 100 observation magnification (captured at 400 observation magnification when the boundary of structures is unclear) was binarized using image processing software Winroof 2015 so as to have ferrite and bainite as bright regions to derive the area ratios of the bright regions, and thereby the ferrite fraction and the bainite fraction of each measurement region were obtained.
- the area obtained by excluding the area of non-metallic structures such as MnS from the test area was regarded as an evaluated area, and the respective proportions of the areas of the ferrite structure and the bainite structure relative to the evaluated area were regarded as the area ratios of the ferrite structure and the bainite structure.
- the average value of the ferrite fraction of the 24 measurement regions was regarded as the ferrite fraction, and the average value of the bainite fraction of the 24 measurement regions was regarded as the bainite fraction.
- the area ratio of structures other than ferrite and bainite were determined by 100 - (Ferrite fraction + Bainite fraction).
- the standard deviation of the ferrite fraction in the 24 measurement points was regarded as the standard deviation of the ferrite fraction of the 0.7R ⁇ r ⁇ 0.9R range.
- V is the casting rate, and the unit is m/min
- A is the casting size (the cross-sectional area of the bloom), and the unit is mm 2
- C is the average cooling rate of the bloom from immediately after casting to the bending correction point.
- the average cooling rate of the bloom is a value obtained by dividing the temperature difference between the casting temperature of molten steel and the surface temperature of the bloom at the bending correction point by the time required to reach the correction point from immediately below the mold.
- the unit is °C/min.
- the bending correction point is a position where the shape of the bloom is corrected from a curved shape to a straight shape in curved continuous casting.
- the range of V ⁇ A 0.5 /C needs to be controlled to 6.0 to 20.0.
- the preferable lower limit is 6.2 or more and more preferably 6.5 or more.
- the preferable upper limit is 19.0 or less and more preferably 18.0 or less. It is impossible to actually measure the internal temperature during casting, but the use of this formula enables the internal temperature to be estimated in consideration of the items that can be actually measured and the casting size, thereby enabling cast control of a region corresponding to the gear teeth during casting.
- post-rolling cooling it is important to control the average cooling rate when the surface temperature of steel during cooling is between 800°C and 300°C.
- a uniform structure can be obtained by controlling the average cooling rate to 0.1 to 1.0°C/sec when the surface temperature of steel is between 800°C and 300°C, and, moreover, the ferrite fraction can be within a predetermined range. When the average cooling rate exceeds this range, a uniform structure cannot be obtained, and thermal strain is increased.
- the preferable lower limit of the post-rolling cooling rate is 0.15°C/sec or faster and more preferably 0.2°C/sec or faster.
- the preferable upper limit of the post-rolling cooling rate is 0.9°C/sec or slower and more preferably 0.8°C/sec or slower.
- Molten steel is cast using a curved continuous casting machine (a casting step).
- the mold size, the casting rate, and the cooling rate during casting are controlled as described above, and are desirably in the following ranges from the viewpoint of productivity.
- the mold size is 30000 mm 2 or more and 400000 mm 2 or less, the casting rate is 0.2 m/min or faster and 3.0 m/min or slower, and the cooling rate from casting to the correction point is 4.0°C/min or faster and 100°C/min or slower.
- the bloom obtained by the casting step is subjected to bloom rolling to obtain a billet (a bloom-rolling step).
- the heating temperature during bloom rolling is desirably 1100°C or higher.
- a more preferable heating temperature is 1200°C or higher.
- an excessively high heating temperature results in coarse crystal grains, and thus the upper limit of the heating temperature is desirably 1280°C.
- the bloom-rolling reduction of area is desirably 30% or more and more preferably 40% or more.
- bar rolling or wire rod rolling is performed.
- the heating temperature of bar rolling or wire rod rolling is desirably 1100°C or higher.
- a more preferable heating temperature is 1150°C or higher.
- an excessively high heating temperature results in coarse crystal grains, and thus the upper limit of the heating temperature is desirably 1250°C.
- the post-rolling cooling rate is controlled such that the average cooling rate when the surface temperature of steel is between 800°C and 300°C is 0.1 to 1.0°C/sec.
- a carburized gear is obtained by performing machining on the above steel to form a gear shape and then performing carburizing hardening and tempering.
- a method for forming a gear shape hot forging, cold forging, cutting, or grindstone processing may be performed. Also, in order to increase workability, normalizing and annealing may be performed. Moreover, these may be combined.
- carburizing hardening any carburizing method such as gas carburizing and vacuum carburizing can be used. Moreover, carbonitriding may be performed. Any type of gear may be created, such as spur gears, helical gears, bevel gears, external teeth, and internal teeth.
- Test Nos.1 to 19 of the inventive examples had good thermal strain.
- Test Nos. 20 to 23, 33, and 34 of the comparative examples good thermal strain was not obtained because the chemical component ranges were outside the scope of the present invention.
- any one or more of the ferrite fraction, the fractions of structures other than ferrite and bainite, and the variation in ferrite fraction were outside the scope of the invention, and thus it was not possible to suppress the variation in helix deviation.
- molten steels having the chemical components shown in Steel Nos. 1, 3, and 24 of Table 1 were cast under the conditions shown in Production Conditions 1 to 12 of Table 2 to obtain blooms. Thereafter, the blooms were heated to 1250°C and bloom-rolled to obtain billets having 162 mm per side. These billets were heated to 1200°C, bar-rolled to have a shape (a post-rolling diameter) shown in Production Conditions 1 to 12 of Table 2, and cooled under the cooling conditions shown in the same table to obtain steels 1, 24 to 32, 35, and 36.
- Test Nos. 1, 24 to 32, 35, and 36 of Table 3 Test No. 32 is a test example corresponding to Production No. 1 of PCT International Publication No. WO 2014/171472 .
- Test Nos. 1 and 24 to 28 of the inventive examples had good thermal strain.
- the production conditions were not desirable in Test Nos. 29 to 32, 35, and 36 of the comparative examples, good thermal strain was not obtained.
- Test No. 35 the variation in ferrite fraction was excessive. This is presumably because the post-rolling cooling rate was too fast, and thus it was not possible to achieve structural uniformity. Accordingly, in Test No. 35, it was not possible to suppress the variation in helix deviation.
- Test No. 36 the fraction of a structure other than ferrite and bainite was excessive.
- the structure other than ferrite and bainite was pearlite. This is presumably because V ⁇ A 0.5 /C was too small, thus it was not possible to eliminate segregation, and moreover the post-rolling cooling rate was too small. Accordingly, in Test No. 36, it was not possible to suppress the variation in helix deviation.
- Test No. 36 the variation in ferrite fraction was suppressed despite V ⁇ A 0.5 /C being too small. This is considered to be because the structure included pearlite. However, pearlite also causes an increased variation in helix deviation, and thus it cannot be said that the steel of Test No. 36 is steel that stabilizes thermal strain.
- Blank columns indicate elements which are not positively included.
- Underlins indicate values outside of the scope of the present invention. Blank columns indicate elements which are not positively included. Underlines indicate values outside of the desireble manufacturing conditions.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Articles (AREA)
Description
- The present invention relates to steel.
- In order to simultaneously achieve precise dimensional accuracy and strength, gears for use in automobiles, construction machinery, industrial machinery, and the like are generally used after receiving carburizing hardening after machining. In recent years, quietness during operation has been more strongly demanded than before, and thus an increase in the dimensional accuracy of gears, especially the dimensional accuracy of teeth, has been demanded. The dimensional accuracy of gear teeth is attributable to deformation associated with heat treatment during carburizing hardening (hereinafter referred to as thermal strain). Since this thermal strain varies and is not uniform for each gear tooth, a symmetrical shape is lost in the same gear, and thus vibrations are created during use, thus losing quietness. Accordingly, demands exist for stabilizing thermal strain on gear teeth so as to provide a symmetrical shape.
- Concerning conventional technical development of steel for carburized gears, Patent Document 1 discloses a technology for providing steel having excellent cold forgeability and temper softening resistance. However, Patent Document 1 does not provide a technology for stabilizing thermal strain on gear teeth during carburizing hardening, which is an object of the present invention.
- Patent Document 2 discloses a technology for providing a hot-rolled steel bar or wire rod composed of a ferrite-pearlite structure, ferrite-pearlite-bainite structure, or ferrite-bainite structure, wherein the standard deviation of ferrite fractions at the time when randomly selected 15 viewing fields of a transverse cross-section are observed and measured with the area per one viewing field being 62500 µm2 is 0.10 or less; and when a region from the surface to one-fifth of the radius and a region from the center to one-fifth of the radius in the transverse cross-section are observed, in each of the regions, the amount of Al precipitating as AlN is 0.005% or less, and the density in terms of the number of AlN having a diameter of 100 nm or larger is 5/100 µm2 or less. However, in reference to the Examples disclosed in Patent Document 2, it is presumed that the technology of Patent Document 2 uses a pearlite structure to reduce the standard deviation of ferrite fractions. That is to say, according to the technology of Patent Document 2, it is not possible to sufficiently reduce the standard deviation of ferrite fractions while controlling the structures so as not to substantially include pearlite.
-
- Patent Document 1:
PCT International Publication No. WO 2014/171472 - Patent Document 2:
PCT International Publication No. WO 2011/055651 - An object of the present invention is to provide steel that stabilizes thermal strain on gear teeth during carburizing hardening.
- The present invention is as described in the appended claims.
- By using steel of the present invention, thermal strain on the teeth of a gear manufactured by carburizing hardening can be stabilized.
- [
Figure 1] Figure 1 is a schematic cross-sectional view of steel for explaining the positions for measuring the average ferrite fraction and the standard deviation of the ferrite fraction. - Below, the present invention is described in detail.
- First, the circumstances of arriving at the present invention are described.
- The present inventors have conducted diligent research on a method for stabilizing thermal strain on the teeth of a gear after carburizing hardening. As a result, it was found that the thermal strain is stabilized by increasing the uniformity of structures in a region of steel that becomes teeth after machining. Accordingly, concerning a method for making uniform the structures of a region corresponding to the gear teeth in steel, the inventors further investigated the effect of changing the chemical components of steel and the manufacturing method. As a result, it was found that by configuring the steel components to be in predetermined ranges and then controlling the casting method and the post-rolling cooling rate, the structures of a region corresponding to the gear teeth in steel can be uniform. Concerning the control of the casting method, the cross-sectional area of casting, the casting rate, and the average cooling rate of the surface from the beginning of casting to the correction point are controlled in a combined manner. This makes it possible to homogenize the cast structures of a region in a bloom that eventually becomes gear teeth. Moreover, concerning the control of the post-rolling cooling rate, the cooling rate of the steel surface is controlled. This makes it possible to homogenize the structures of a region in steel that corresponds to the gear teeth.
- Next, the reason for limiting the chemical components of steel according to the present invention is described. Below, "% by mass" which is a unit relating to the amount of an alloying element is simply referred to as "%".
- The C content affects the hardness of the non-carburized portion of a gear. In order to ensure a required hardness, the C content is 0.17% or more. On the other hand, when the C content is excessive, the hardness of the non-carburized portion after carburization is high, resulting in poor impact strength, and thus the C content is 0.21 % or less. The preferable lower limit of the C content is 0.175%, 0.18%, 0.185%, or 0.19%. The preferable upper limit of the C content is 0.205%, 0.200%, 0.195%, or 0.19%.
- Si is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel. When the Si content is excessive, the amount of ferrite in steel is insufficient, and the amounts of bainite and the like are increased, resulting in poor workability. In order to obtain the above-described effect, the Si content needs to be within the range of 0.40 to 0.60%. The preferable lower limit of the Si content is 0.42%, 0.45%, 0.48%, or 0.50%. The preferable upper limit of the Si content is 0.58%, 0.55%, 0.53%, or 0.51%.
- Mn is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel. In order to obtain the above-described effect, the Mn content needs to be 0.25% or more. When the Mn content is excessive, the amount of ferrite in steel is insufficient, and the amounts of bainite and the like are increased, resulting in poor workability. Accordingly, the Mn content is 0.50% or less. The preferable lower limit of the Mn content is 0.27%, 0.30%, 0.32%, or 0.35%. The preferable upper limit of the Mn content is 0.48%, 0.45%, 0.42%, or 0.40%.
- Cr is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel. When the Cr content is excessive, the amount of ferrite in steel is insufficient, and the amounts of bainite and the like are increased, resulting in poor workability. In order to obtain the above-described effect, the Cr content needs to be within the range of 1.35 to 1.55%. The preferable lower limit of the Cr content is 1.37%, 1.40%, 1.42%, or 1.45%. The preferable upper limit of the Cr content is 1.53%, 1.50%, 1.49%, or 1.47%.
- Mo is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel. When Mo is contained in steel together with Nb, which will be described below, Mo suppresses pearlite transformation by increasing the hardenability of steel, and also suppresses coarse austenite crystal grains during the heating of steel. This makes it possible to suitably control hardenability, and obtain the desired bainite structure by suppressing martensite transformation. When the Mo content is excessive, the amount of ferrite in steel is insufficient, and the amounts of bainite and the like are increased, resulting in poor workability. In order to obtain the above-described effect, the Mo content needs to be within the range of 0.20 to 0.40%. The preferable lower limit of the Mo content is 0.22%, 0.25%, 0.28%, or 0.30%. The preferable upper limit of the Mo content is 0.38%, 0.35%, 0.32%, or 0.30%.
- S forms MnS in steel, thereby increasing the machinability of steel. In order to obtain a level of machinability that enables components to be cut, a S content comparable to that of commonly used steel for machine structural use is needed. For the above reason, the S content needs to be within the range of 0.010 to 0.05%. The preferable lower limit of the S content is 0.012%, 0.014%, 0.020%, or 0.022%. The preferable upper limit of the S content is 0.035%, 0.030%, 0.028%, or 0.025%.
- N has a crystal grain refining effect by forming compounds with Al, Ti, V, Cr, and the like, and thus needs to be contained in an amount of 0.005% or more. However, when N exceeds 0.020%, compounds are coarse, and the crystal grain refining effect cannot be obtained. For the above reason, the N content needs to be within the range of 0.005 to 0.020%. The preferable lower limit of the N content is 0.0055%, 0.0060%, 0.007%, or 0.010%. The preferable upper limit of the N content is 0.018%, 0.015%, 0.012%, or 0.010%.
- Al is an element effective for the deoxidation of steel, and is an element that binds to N to form nitride and refine crystal grains. When the Al content is less than 0.001%, this effect is insufficient. On the other hand, when the Al content exceeds 0.100%, nitride is coarse and causes embrittlement. The preferable lower limit of the Al content is 0.004%, 0.007%, 0.010%, or 0.020%. The preferable upper limit of the Al content is 0.080%, 0.050%, 0.040%, or 0.030%.
- Nb is an element that produces fine compounds with C and N in steel and provides a crystal grain refining effect. Also, Nb when contained in steel together with Mo exerts the above-described synergistic effect (the effect of suppressing pearlite transformation and martensite transformation). When the Nb content is less than 0.001%, this effect is insufficient. When the Nb content exceeds 0.030%, carbonitride is coarse, and this effect cannot be sufficiently obtained. For the above reason, the Nb content needs to be 0.001 to 0.030%. The preferable lower limit of the Nb content is 0.005%, 0.010%, 0.012%, or 0.015%. The preferable upper limit of the Nb content is 0.028%, 0.025%, 0.022%, or 0.020%.
- O forms oxide in steel and acts as an inclusion to reduce fatigue strength, and thus the O content is limited to 0.005% or less. The preferable upper limit of the O content is 0.003%, 0.002%, 0.0015%, or 0.001%. Since a smaller O content is more preferable, the lower limit of the O content is 0%. However, removing O more than necessary results in increased manufacturing costs. Accordingly, the lower limit of the O content may be 0.0001 %, 0.0002%, 0.0005%, or 0.0008%.
- P segregates at austenite grain boundaries during heating before hardening, thereby reducing fatigue strength. Accordingly, the P content is limited to 0.03% or less. The preferable upper limit of the P content is 0.025%, 0.023%, 0.020%, or 0.015%. Since a smaller P content is more preferable, the lower limit of the P content is 0%. However, removing P more than necessary results in increased manufacturing costs. Accordingly, the substantial lower limit of the P content is usually about 0.004% or more. The lower limit of the P content may be 0.005%, 0.007%, 0.010%, or 0.012%.
- Steel according to the present invention may further contain one or two or more selected from the group consisting of Ni, Cu, Co, W, V, Ti, and B in place of a part of Fe in order to increase hardenability or the crystal grain refining effect. The lower limit when these elements are not contained is 0%.
- Ni is an element effective for imparting necessary hardenability to steel. In order to obtain this effect, the Ni content is preferably 0.01% or more. When the Ni content exceeds 3.0%, the amount of residual austenite after hardening is large, resulting in poor hardness. For the above reason, the Ni content is 3.0% or less and more preferably 0.01 to 3.0%. The upper limit of the Ni content is more preferably 2.0% and even more preferably 1.8%. A more preferable lower limit of the Ni content is 0.1% and more preferably 0.3%.
- Cu is an element effective for increasing the hardenability of steel. In order to obtain this effect, the Cu content is preferably 0.01% or more. When the Cu content exceeds 1.0%, hot ductility is impaired. Accordingly, the Cu content is 1.0% or less and more preferably 0.01 to 1.0%. When obtaining the above-described effect by containing Cu, a more preferable lower limit of the Cu content is 0.05% and even more preferably 0.1%.
- Co is an element effective for increasing the hardenability of steel. In order to obtain this effect, the Co content is preferably 0.01% or more. When the Co content exceeds 3.0%, the effect is saturated. Accordingly, the Co content is 3.0% or less and more preferably 0.01 to 3.0%. When obtaining the above-described effect by containing Co, a more preferable lower limit of the Co content is 0.05% and even more preferably 0.1%.
- W is an element effective for increasing the hardenability of steel. In order to obtain this effect, the W content is preferably 0.01% or more. When the W content exceeds 1.0%, the effect is saturated. Accordingly, the W content is 1.0% or less and more preferably 0.01 to 1.0%. When obtaining the above-described effect by containing W, a more preferable lower limit of the W content is 0.05% and even more preferably 0.1 %.
- V is an element that produces fine compounds with C and N in steel and provides a crystal grain refining effect. In order to obtain this effect, the V content is preferably 0.01 % or more. When the V content exceeds 0.3%, compounds are coarse, and the crystal grain refining effect cannot be obtained. Accordingly, the V content is 0.3% or less and more preferably 0.01 to 0.3%. When obtaining the above-described effect by containing V, a more preferable lower limit of the V content is 0.1% and even more preferably 0.15%.
- Ti is an element that produces fine compounds with C and N in steel and provides a crystal grain refining effect. In order to obtain this effect, the Ti content is preferably 0.001% or more. When the Ti content exceeds 0.3%, the effect is saturated. For the above reason, the Ti content is 0.3% or less and more preferably 0.001 to 0.3%. A more preferable upper limit of the Ti content is 0.25% and even more preferably 0.2%.
- B functions to suppress the grain boundary segregation of P. B also has the effect of increasing grain boundary strength and intragranular strength and the effect of increasing hardenability, and these effects increase the fatigue strength of steel. In order to obtain this effect, the B content is preferably 0.0001% or more. When the B content exceeds 0.005%, the effect is saturated. For the above reason, the B content is 0.005% or less and preferably 0.0001 to 0.005%. A more preferable upper limit of the B content is 0.0045% and even more preferably 0.004%.
- The chemical composition of steel according to the present invention may further contain one or two or more selected from the group consisting of Pb, Bi, Ca, Mg, Zr, Te, and rare earth elements (REMs) in place of a part of Fe. The lower limit when these elements are not contained is 0%.
- Pb is an element that increases machinability by being molten and embrittled during cutting. In order to obtain this effect, the Pb content is preferably 0.01% or more. On the other hand, Pb when excessively contained impairs productivity. Accordingly, the Pb content is 0.5% or less and more preferably 0.01 to 0.5%. When obtaining the above-described effect by containing Pb, a more preferable lower limit of the Pb content is 0.05% and even more preferably 0.1 %. The preferable upper limit of Pb is 0.4% and even more preferably 0.3%.
- Bi is an element that increases machinability due to finely dispersed sulfide. In order to obtain this effect, the Bi content is preferably 0.0001 % or more. On the other hand, when Bi is excessively contained, the hot workability of steel deteriorates, making hot rolling difficult, and thus the Bi content is 0.5% and more preferably 0.0001 to 0.5%. When obtaining the above-described effect by containing Bi, a more preferable lower limit is 0.0001 % and even more preferably 0.001%. The preferable upper limit of Bi is 0.4% and even more preferably 0.3%.
- Ca is an element effective for the deoxidation of steel and reduces the Al2O3 content in oxide. In order to obtain this effect, the Ca content is preferably 0.0001 % or more. When the Ca content exceeds 0.01 %, a large amount of Cacontaining coarse oxide appears and causes a shortened rolling fatigue life. For the above reason, the Ca content needs to be within the range of 0.0001 to 0.01%. The preferable lower limit of the Ca content is 0.0003% and more preferably 0.0005%. The preferable upper limit of the Ca content is 0.008% and more preferably 0.006%.
- Mg is a deoxidizing element and produces oxide in steel. Moreover, Mgbased oxide formed by Mg likely becomes a nucleus for crystallization and/or precipitation of MnS. Also, the sulfide of Mg makes MnS spherical by becoming a complex sulfide of Mn and Mg. Thus, Mg is an element effective for controlling the dispersion of MnS and improving machinability. In order to obtain this effect, the Mg content is preferably 0.0001% or more. However, when the Mg content exceeds 0.01%, a large amount of MgS is produced, and the machinability of steel decreases. Thus, in order to obtain the above-described effect by containing Mg, the Mg content needs to be 0.01% or less. The preferable upper limit of the Mg content is 0.008% and more preferably 0.006%. The preferable lower limit of the Mg content is 0.0005% and more preferably 0.001%.
- Zr is a deoxidizing element and forms oxide. Moreover, Zr-based oxide formed by Zr likely becomes a nucleus for crystallization and/or precipitation of MnS. Thus, Zr is an element effective for controlling the dispersion of MnS and improving machinability. In order to obtain this effect, the Zr content is preferably 0.0001% or more. However, when the amount of Zr exceeds 0.05%, the effect is saturated. Thus, in order to obtain the above-described effect by containing Zr, the Zr content is 0.05% or less and more preferably 0.0001 to 0.05%. The preferable upper limit of the Zr content is 0.04% and more preferably 0.03%. The preferable lower limit of the Zr content is 0.0005% and more preferably 0.001%.
- Te promotes the spheroidization of MnS and thus improves the machinability of steel. In order to obtain this effect, the Te content is preferably 0.0001% or more. When the Te content exceeds 0.1%, the effect is saturated. Accordingly, the Te content is 0.1% or less and more preferably 0.0001 to 0.1%. The preferable upper limit of the Te content is 0.08% and more preferably 0.06%. The preferable lower limit of the Te content is 0.0005% and more preferably 0.001%.
- Rare earth elements are elements that promote the production of MnS by producing sulfide in steel and this sulfide becoming a precipitation nucleus for MnS, and improve the machinability of steel. In order to obtain this effect, the total amount of rare earth elements is preferably 0.0001 % or more. However, when the total amount of rare earth elements exceeds 0.005%, sulfide is coarse, reducing the fatigue strength of steel. Accordingly, the total amount of rare earth elements is 0.005% or less and more preferably 0.0001 to 0.005%. The preferable upper limit of the total amount of rare earth elements is 0.004% and more preferably 0.003%. The preferable lower limit of the total amount of rare earth elements is 0.0005% and more preferably 0.001%.
- The rare earth element as used herein is a collective term referring to 17 elements including 15 elements from lanthanum (La) with atomic number 57 to lutetium (Lu) with atomic number 71 in addition to yttrium (Y) and scandium (Sc) in the periodic table. The amount of rare earth elements means the total amount of one or two or more of these elements.
- Steel according to the present invention contains the above-described alloying components, and the balance includes Fe and impurities. Elements other than the above-described alloying components are allowable in steel as impurities from raw materials and manufacturing equipment as long as the amounts thereof do not affect the properties of steel.
- Next, the uniformity of the structures of steel is described.
- As described above, in order to improve the thermal strain on gear teeth, the uniformity of the structures of a region in steel that corresponds to the gear teeth needs to be increased. Here, the region of steel corresponding to the gear teeth is a region including a part from the tooth tip to the tooth root of a gear after forging or cutting, and is a region satisfying 0.7R ≤ r ≤ 0.9R in rolled steel, wherein r is the distance from the center of the cross-section of steel that is perpendicular to the length direction, and R is a circle equivalent radius in the cross-section of steel that is perpendicular to the length direction of steel.
- As a result of investigations by the inventors, it became clear that the uniform structures suitable for improvement of thermal strain are structures including ferrite and bainite, and that the structure fractions are in suitable ranges. According to the investigations of the relationship between structure fractions and thermal strain, the thermal strain was stabilized when, in the 0.7R ≤ r ≤ 0.9R region, the average value of the ferrite fraction (average fraction) in terms of area ratio is in the range of 40 to 70%, the total of the average fractions of structures other than ferrite and bainite is 0% or more and 3% or less on average, the balance includes bainite, and the standard deviation of the average ferrite fraction in the 0.7R ≤ r ≤ 0.9R range is 4% or less, as determined by the measurement method described below. When the structure fractions exceeded the above ranges, the thermal strain was increased. Below, what is simply referred to as a "fraction" with respect to a metal structure means the average value of a structure fraction (unit: area%) in the cross-section of steel determined by the means described below. However, in the "standard deviation of a fraction", the "fraction" does not mean an average value in the entirety of a cross-section but means the fraction in each measured visual field, as will be described below.
- The preferable lower limit of the ferrite fraction is 42% and more preferably 45%. The preferable upper limit of the ferrite fraction is 68% and more preferably 65%. A lower standard deviation of the ferrite fraction in the 0.7R ≤ r ≤ 0.9R range is more preferable, and thus the lower limit is 0%. The preferable upper limit of the standard deviation of the ferrite fraction in the 0.7R ≤ r ≤ 0.9R range is 3.5% and more preferably 3%.
- In steel according to the present invention, "bainite" means, among the structures obtained by heating steel to form an austenite single phase structure and then cooling it to room temperature by continuous cooling, a structure excluding a ferrite structure, a pearlite structure, and a martensite structure, and means a collective term referring to an upper bainite structure, a lower bainite structure, or a mixed structure of an upper bainite structure and a lower bainite structure.
- It is not preferable that pearlite is contained in the structures of steel according to the present invention because it deteriorates carburizing hardenability. For example, when steel composed of mixed structures of ferrite, pearlite, and bainite is carburizing-hardened, the austenite crystal grain structure in a region corresponding to the teeth becomes non-uniform during heating. Accordingly, deformation after carburizing hardening, i.e., thermal strain, is increased. Thus, the area ratio of pearlite needs to be limited as much as possible. In this regard, the total of structures other than ferrite and bainite is specified to be 0% or more and 3% or less. Generally, a structure wherein the total of structures other than ferrite and bainite is 0% or more and 3% or less is referred to as a "ferrite-bainite structure". In other words, steel according to the present invention is steel having a ferrite-bainite structure.
- Next, the method for measuring a structure fraction is described.
- As shown in
FIG. 1 , the points where the circumferences having 0.7R + 0.25 mm, 0.8R, and 0.9R - 0.25 mm intersect straight lines radially dividing, from the center of the cross-section of steel, the cross-section into eight equal parts (central angle 45°) were regarded as measurement points, and rectangular regions having 0.5 mm × 1 mm = 0.5 mm2 were regarded as measurement regions such that the respective measurement points were at the centers of the rectangles. There are 24 measurement regions. The ferrite fraction and the standard deviation of the ferrite fraction in the 0.7R ≤ r ≤ 0.9R range were determined by observation using an optical microscope with respect to a sample obtained by mirror-polishing the cross-section of steel and corroding it with nital. Since MnS and the like may exist as structures other than ferrite and bainite, each measurement region of the nitalcorroded sample was visually observed, and in each measurement region, the 0.5 mm2 area in an image captured at 100 observation magnification (captured at 400 observation magnification when the boundary of structures is unclear) was binarized using image processing software Winroof 2015 so as to have ferrite and bainite as bright regions to derive the area ratios of the bright regions, and thereby the ferrite fraction and the bainite fraction of each measurement region were obtained. When determining the area ratios, the area obtained by excluding the area of non-metallic structures such as MnS from the test area was regarded as an evaluated area, and the respective proportions of the areas of the ferrite structure and the bainite structure relative to the evaluated area were regarded as the area ratios of the ferrite structure and the bainite structure. The average value of the ferrite fraction of the 24 measurement regions was regarded as the ferrite fraction, and the average value of the bainite fraction of the 24 measurement regions was regarded as the bainite fraction. The area ratio of structures other than ferrite and bainite were determined by 100 - (Ferrite fraction + Bainite fraction). The standard deviation of the ferrite fraction in the 24 measurement points was regarded as the standard deviation of the ferrite fraction of the 0.7R ≤ r ≤ 0.9R range. - Next, the cross-sectional area and the casting rate during casting, the cooling rate from casting to the correction point, and the post-rolling cooling rate are described.
- In order for the inventors to improve thermal strain on gear teeth, it is necessary to strictly specify the ranges of Si, Cr, Mn, and Mo components of steel as described above, and control the casting method and the cooling method during rolling. Concerning the casting method, it is important to control the temperature change of a region corresponding to the gear teeth during casting. When the casting size changes, the temperature and the cooling rate of this region change even at the same casting rate and the same cooling rate. Thus, as a result of investigating the casting size and the temperature change inside a bloom, it became clear that the extent of segregation in a region corresponding to the gear teeth can be controlled by controlling V×A0.5/C, where V is the casting rate, and the unit is m/min; A is the casting size (the cross-sectional area of the bloom), and the unit is mm2; and C is the average cooling rate of the bloom from immediately after casting to the bending correction point. The average cooling rate of the bloom is a value obtained by dividing the temperature difference between the casting temperature of molten steel and the surface temperature of the bloom at the bending correction point by the time required to reach the correction point from immediately below the mold. The unit is °C/min. The bending correction point is a position where the shape of the bloom is corrected from a curved shape to a straight shape in curved continuous casting.
- In order to suitably control the degree of segregation in a region corresponding to the gear teeth, the range of V×A0.5/C needs to be controlled to 6.0 to 20.0. The preferable lower limit is 6.2 or more and more preferably 6.5 or more. The preferable upper limit is 19.0 or less and more preferably 18.0 or less. It is impossible to actually measure the internal temperature during casting, but the use of this formula enables the internal temperature to be estimated in consideration of the items that can be actually measured and the casting size, thereby enabling cast control of a region corresponding to the gear teeth during casting.
- As for post-rolling cooling, it is important to control the average cooling rate when the surface temperature of steel during cooling is between 800°C and 300°C. A uniform structure can be obtained by controlling the average cooling rate to 0.1 to 1.0°C/sec when the surface temperature of steel is between 800°C and 300°C, and, moreover, the ferrite fraction can be within a predetermined range. When the average cooling rate exceeds this range, a uniform structure cannot be obtained, and thermal strain is increased. The preferable lower limit of the post-rolling cooling rate is 0.15°C/sec or faster and more preferably 0.2°C/sec or faster. The preferable upper limit of the post-rolling cooling rate is 0.9°C/sec or slower and more preferably 0.8°C/sec or slower.
- Preferable manufacturing conditions for steel according to the present invention are described.
- Molten steel, the chemical components of which have been adjusted in a refining step, is cast using a curved continuous casting machine (a casting step). The mold size, the casting rate, and the cooling rate during casting are controlled as described above, and are desirably in the following ranges from the viewpoint of productivity. The mold size is 30000 mm2 or more and 400000 mm2 or less, the casting rate is 0.2 m/min or faster and 3.0 m/min or slower, and the cooling rate from casting to the correction point is 4.0°C/min or faster and 100°C/min or slower.
- The bloom obtained by the casting step is subjected to bloom rolling to obtain a billet (a bloom-rolling step). In order to securely dissolve the Nb compound, the heating temperature during bloom rolling is desirably 1100°C or higher. A more preferable heating temperature is 1200°C or higher. On the other hand, an excessively high heating temperature results in coarse crystal grains, and thus the upper limit of the heating temperature is desirably 1280°C. The bloom-rolling reduction of area is desirably 30% or more and more preferably 40% or more.
- In order to configure the above billet to be steel for a carburized gear (a steel bar or a wire rod having a circular cross-section), bar rolling or wire rod rolling is performed. In order to securely dissolve the Nb compound, the heating temperature of bar rolling or wire rod rolling is desirably 1100°C or higher. A more preferable heating temperature is 1150°C or higher. On the other hand, an excessively high heating temperature results in coarse crystal grains, and thus the upper limit of the heating temperature is desirably 1250°C. As described above, the post-rolling cooling rate is controlled such that the average cooling rate when the surface temperature of steel is between 800°C and 300°C is 0.1 to 1.0°C/sec.
- A carburized gear is obtained by performing machining on the above steel to form a gear shape and then performing carburizing hardening and tempering. Here, as a method for forming a gear shape, hot forging, cold forging, cutting, or grindstone processing may be performed. Also, in order to increase workability, normalizing and annealing may be performed. Moreover, these may be combined. As for carburizing hardening, any carburizing method such as gas carburizing and vacuum carburizing can be used. Moreover, carbonitriding may be performed. Any type of gear may be created, such as spur gears, helical gears, bevel gears, external teeth, and internal teeth.
- Below, the present invention is further described by way of Examples.
- Concerning molten steel having the chemical components of steel numbers 1 to 23, 25, and 26 shown in Table 1, casting was performed under the conditions shown in No. 1 of Table 2 to obtain blooms. The balance of the chemical components disclosed in Table 1 was iron and impurities, and the blank indicates that the component was intentionally not contained. Thereafter, the blooms were heated to 1250°C and bloom-rolled to obtain billets having 162 mm per side. These billets were heated to 1200°C and bar-rolled to regulate the diameter thereof to 40 mm, and then cooled under the conditions shown in No. 1 of Table 2 to obtain steels 1 to 23, 33, and 34. Concerning these steels, the structure fractions such as a ferrite fraction and the standard deviation of the ferrite fraction (variation (%) in ferrite fraction) were determined by the above-described methods. The results are shown in Table 3.
- Then, in order to evaluate the thermal strain of a gear, a 30 mm wide spur gear having a module of 2, a number of teeth of 16, an inner diameter of ϕ18 mm was created by cutting. After the gear was retained in an atmosphere wherein gas carburizing was 925°C and carbon potential CP was 0.8 for 2 hours, oil hardening was performed at 130°C. Thereafter, tempering was performed at 150°C. Thereafter, the shape measurement in the helix direction at 90° pitch for four teeth per gear was performed on five gears by a gear shape measuring machine, and the difference between the maximum value and the minimum value of the helix deviation thus obtained was regarded as a variation in helix deviation. A variation in helix deviation of 15 µm or less was determined as good thermal strain. The results are shown in Test Nos. 1 to 23, 33, and 34 of Table 3.
- Test Nos.1 to 19 of the inventive examples had good thermal strain. As for Test Nos. 20 to 23, 33, and 34 of the comparative examples, good thermal strain was not obtained because the chemical component ranges were outside the scope of the present invention.
- Specifically, in Test No. 20, the ferrite fraction was insufficient, and the variation in ferrite fraction was excessive. This is presumably because the amount of Si was excessive.
- In Test No. 21, the ferrite fraction was insufficient, and the variation in ferrite fraction was excessive. This is presumably because the amount of Mn was excessive.
- In Test No. 22, the ferrite fraction was insufficient, and the variation in ferrite fraction was excessive. This is presumably because the amount of Cr was excessive.
- In Test No. 23, the ferrite fraction was insufficient, and the variation in ferrite fraction was excessive. This is presumably because the amount of Mo was excessive.
- In Test No. 33, the ferrite fraction was insufficient, and moreover the fractions of structures other than ferrite and bainite were excessive. This is presumably because one of Nb and Mo was not contained in steel, and thus the pearlite production suppressing effect of Nb and Mo was not obtained.
- In Test No. 34, the fractions of structures other than ferrite and bainite were excessive. This is presumably because one of Nb and Mo was not contained in steel, and thus the pearlite production suppressing effect of Nb and Mo was not obtained.
- In Test Nos. 20 to 23, 33, and 34 described above, any one or more of the ferrite fraction, the fractions of structures other than ferrite and bainite, and the variation in ferrite fraction were outside the scope of the invention, and thus it was not possible to suppress the variation in helix deviation.
- Next, molten steels having the chemical components shown in Steel Nos. 1, 3, and 24 of Table 1 were cast under the conditions shown in Production Conditions 1 to 12 of Table 2 to obtain blooms. Thereafter, the blooms were heated to 1250°C and bloom-rolled to obtain billets having 162 mm per side. These billets were heated to 1200°C, bar-rolled to have a shape (a post-rolling diameter) shown in Production Conditions 1 to 12 of Table 2, and cooled under the cooling conditions shown in the same table to obtain steels 1, 24 to 32, 35, and 36. Concerning these steels, the structure fractions such as a ferrite fraction, the standard deviation of the ferrite fraction (variation (%) in ferrite fraction), and the variation in helix deviation were evaluated by the above-described methods. The results are shown in Test Nos. 1, 24 to 32, 35, and 36 of Table 3. Test No. 32 is a test example corresponding to Production No. 1 of
PCT International Publication No. WO 2014/171472 . - Test Nos. 1 and 24 to 28 of the inventive examples had good thermal strain. On the other hand, since the production conditions were not desirable in Test Nos. 29 to 32, 35, and 36 of the comparative examples, good thermal strain was not obtained.
- Specifically, in Test No. 29, the variation in ferrite fraction was excessive. This is presumably because V×A0.5/C was too large, and thus it was not possible to eliminate segregation. Accordingly, in Test No. 29, it was not possible to suppress the variation in helix deviation.
- In Test No. 30, the variation in ferrite fraction was excessive. This is presumably because V×A0.5/C was too small, and thus it was not possible to eliminate segregation. Accordingly, in Test No. 30, it was not possible to suppress the variation in helix deviation.
- In Test No. 31, the ferrite fraction was insufficient. This is presumably because the post-rolling cooling rate was too fast, and thus the structure thereof was mostly bainite. Accordingly, in Test No. 31, it was not possible to suppress the variation in helix deviation.
- In Test No. 32, the variation in ferrite fraction was excessive. This is presumably because V×A0.5/C was too large, and thus it was not possible to eliminate segregation. Accordingly, in Test No. 32, it was not possible to suppress the variation in helix deviation.
- In Test No. 35, the variation in ferrite fraction was excessive. This is presumably because the post-rolling cooling rate was too fast, and thus it was not possible to achieve structural uniformity. Accordingly, in Test No. 35, it was not possible to suppress the variation in helix deviation.
- In Test No. 36, the fraction of a structure other than ferrite and bainite was excessive. The structure other than ferrite and bainite was pearlite. This is presumably because V×A0.5/C was too small, thus it was not possible to eliminate segregation, and moreover the post-rolling cooling rate was too small. Accordingly, in Test No. 36, it was not possible to suppress the variation in helix deviation. In Test No. 36, the variation in ferrite fraction was suppressed despite V×A0.5/C being too small. This is considered to be because the structure included pearlite. However, pearlite also causes an increased variation in helix deviation, and thus it cannot be said that the steel of Test No. 36 is steel that stabilizes thermal strain.
[Table 1A] Steel No. Chemical composition (mass%) Balance is Fe and impurities C Si Mn Cr Mo S N Al Nb O P 1 0.20 0.51 0.43 1.47 0.32 0.015 0.013 0.032 0.013 0.001 0.015 2 0.17 0.59 0.25 1.35 0.40 0.018 0.011 0.022 0.025 0.001 0.019 3 0.21 0.45 0.50 1.54 0.21 0.010 0.012 0.035 0.002 0.001 0.014 4 0.19 0.51 0.44 1.40 0.38 0.013 0.019 0.001 0.029 0.002 0.010 5 0.20 0.40 0.39 1.41 0.30 0.015 0.015 0.027 0.018 0.001 0.023 6 0.21 0.55 0.41 1.39 0.25 0.014 0.013 0.021 0.022 0.001 0.008 7 0.18 0.41 0.40 1.47 0.29 0.013 0.013 0.039 0.017 0.001 0.012 8 0.19 0.43 0.43 1.42 0.33 0.032 0.010 0.035 0.025 0.001 0.014 9 0.20 0.57 0.48 1.51 0.25 0.019 0.015 0.033 0.008 0.001 0.015 10 0.17 0.50 0.45 1.39 0.21 0.011 0.012 0.028 0.014 0.001 0.012 11 0.19 0.46 0.38 1.44 0.39 0.015 0.005 0.099 0.025 0.001 0.014 12 0.20 0.51 0.40 1.41 0.33 0.014 0.011 0.025 0.024 0.001 0.017 13 0.20 0.44 0.44 1.37 0.31 0.014 0.013 0.029 0.022 0.001 0.011 14 0.19 0.48 0.36 1.43 0.32 0.016 0.012 0.027 0.017 0.001 0.013 15 0.18 0.47 0.41 1.41 0.30 0.013 0.009 0.031 0.011 0.001 0.015 16 0.21 0.56 0.40 1.48 0.25 0.014 0.016 0.030 0.022 0.001 0.014 17 0.18 0.45 0.42 1.41 0.29 0.015 0.015 0.035 0.019 0.001 0.011 18 0.18 0.55 0.49 1.44 0.27 0.014 0.013 0.031 0.016 0.001 0.010 19 0.18 0.52 0.42 1.38 0.28 0.015 0.010 0.025 0.022 0.001 0.015 20 0.19 0.62 0.49 1.52 0.38 0.014 0.011 0.030 0.011 0.001 0.014 21 0.19 0.55 0.55 1.51 0.33 0.013 0.013 0.027 0.012 0.001 0.015 22 0.21 0.42 0.27 1.60 0.21 0.014 0.011 0.025 0.004 0.001 0.017 23 0.18 0.47 0.45 1.51 0.48 0.013 0.011 0.028 0.018 0.001 0.012 24 0.18 0.50 0.44 1.45 0.35 0.015 0.013 0.034 0.020 0.001 0.016 25 0.20 0.41 0.45 1.46 0.38 0.011 0.011 0.031 - 0.001 0.012 26 0.21 0.42 0.49 1.52 - 0.015 0.016 0.024 0.035 0.001 0.011 Underlins indicate values outside of the scope of the present invention. Blank columns indicate elements which are not positively included. [Table 1B] Steel No. Chemical composition (mass%) Balance is Fe and impurities Ni Cu Co W V Ti B Pb Bi Ca Mg Zr Te REM 1 2 3 4 5 0.50 6 0.21 7 0.21 8 0.29 9 0.15 10 0.05 11 0.02 0.0021 12 0.05 13 0.022 14 0.0025 15 0.0028 16 0.0010 17 0.0015 18 0.0035 19 0.29 0.0022 20 21 22 23 24 0.0009 25 26 Underlins indicate values outside of the scope of the present invention. Blank columns indicate elements which are not positively included.
Claims (3)
- A steel comprising in % by mass:C: 0.17 to 0.21%,Si: 0.40 to 0.60%,Mn: 0.25 to 0.50%,Cr: 1.35 to 1.55%,Mo: 0.20 to 0.40%,S: 0.010 to 0.05%,N: 0.005 to 0.020%,Al: 0.001% to 0.100%,Nb: 0.001 to 0.030%Ni: 0 to 3.0%,Cu: 0 to 1.0%,Co: 0 to 3.0%,W: 0 to 1.0%,V: 0 to 0.3%,Ti: 0 to 0.3%,B: 0 to 0.005%O: 0.005% or less,P: 0.03% or less,Pb: 0 to 0.5%,Bi: 0 to 0.5%,Ca: 0 to 0.01%,Mg: 0 to 0.01%,Zr: 0 to 0.05%,Te: 0 to 0.1%,rare earth element: 0 to 0.005%, anda balance being Fe and impurities, whereinin a region where a distance r from the center of a cross-section perpendicular to a length direction satisfies the following expression, structures comprise ferrite and bainite, an average fraction of the ferrite is in a range of 40 to 70% in terms of area ratio, a total average fraction of the structures other than the ferrite and the bainite is 0% ormore and 3% or less on average, and a balance includes bainite;a standard deviation of a ferrite fraction in the region is 4% or less:0.7R ≤ r ≤ 0.9Rwhere R represents a circle equivalent radius of the steel,the steel is in the form of a steel bar or a wire rod having a circular cross-section, andthe average fraction of the ferrite, and the standard deviation of the ferrite fraction are determined as set out in the specification.
- The steel according to claim 1, which comprises in % by mass one or two or more of:Ni: 0.01 to 3.0%,Cu: 0.01 to 1.0%,Co: 0.01 to 3.0%,W: 0.01 to 1.0%,V: 0.01 to 0.3%,Ti: 0.001 to 0.3%, andB: 0.0001 to 0.005%.
- The steel according to claim 1 or claim 2, which comprises in % by mass one or two or more of:Pb: 0.01 to 0.5%,Bi: 0.0001 to 0.5%,Ca: 0.0001 to 0.01%,Mg: 0.0001 to 0.01%,Zr: 0.0001 to 0.05%,Te: 0.0001 to 0.1%, andrare earth element: 0.0001 to 0.005%.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2018056867 | 2018-03-23 | ||
PCT/JP2019/011847 WO2019182054A1 (en) | 2018-03-23 | 2019-03-20 | Steel material |
Publications (3)
Publication Number | Publication Date |
---|---|
EP3770291A1 EP3770291A1 (en) | 2021-01-27 |
EP3770291A4 EP3770291A4 (en) | 2021-12-22 |
EP3770291B1 true EP3770291B1 (en) | 2024-01-17 |
Family
ID=67986215
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19772012.1A Active EP3770291B1 (en) | 2018-03-23 | 2019-03-20 | Steel |
Country Status (6)
Country | Link |
---|---|
US (1) | US20200407815A1 (en) |
EP (1) | EP3770291B1 (en) |
JP (1) | JP6919762B2 (en) |
KR (1) | KR102463278B1 (en) |
CN (1) | CN111868281B (en) |
WO (1) | WO2019182054A1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2022071420A1 (en) * | 2020-09-30 | 2022-04-07 | 日本製鉄株式会社 | Steel material |
DE112021005117T5 (en) * | 2020-09-30 | 2023-07-20 | Nippon Steel Corporation | steel material |
CN116904851A (en) * | 2023-06-30 | 2023-10-20 | 鞍钢股份有限公司 | CrMnTi series gear steel and production method thereof |
Family Cites Families (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100268536B1 (en) * | 1996-11-25 | 2000-10-16 | 고지마 마타오 | Steel having excellent machinability and machined component |
JP4050829B2 (en) * | 1998-07-30 | 2008-02-20 | 新日本製鐵株式会社 | Carburized material with excellent rolling fatigue characteristics |
JP2006097066A (en) * | 2004-09-29 | 2006-04-13 | Jfe Bars & Shapes Corp | Case hardening steel |
JP4528363B1 (en) * | 2009-04-06 | 2010-08-18 | 新日本製鐵株式会社 | Case-hardened steel with excellent cold workability, machinability, and fatigue characteristics after carburizing and quenching, and method for producing the same |
WO2011055651A1 (en) | 2009-11-05 | 2011-05-12 | 住友金属工業株式会社 | Hot-rolled steel bar or wire rod |
JP5397247B2 (en) * | 2010-02-02 | 2014-01-22 | 新日鐵住金株式会社 | Hot rolled steel bar or wire rod |
EP2662462A1 (en) * | 2012-05-07 | 2013-11-13 | Valls Besitz GmbH | Low temperature hardenable steels with excellent machinability |
JP6073167B2 (en) * | 2013-03-25 | 2017-02-01 | 株式会社神戸製鋼所 | Case-hardening steel with excellent surface fatigue strength and cold forgeability |
JPWO2014171472A1 (en) | 2013-04-18 | 2017-02-23 | 新日鐵住金株式会社 | Case-hardening steel and case-hardening steel parts |
KR102006093B1 (en) * | 2015-03-31 | 2019-07-31 | 닛폰세이테츠 가부시키가이샤 | Progressive steel parts |
JP6713394B2 (en) | 2016-09-30 | 2020-06-24 | 株式会社Nttドコモ | Control device, base station device, communication system, and communication method |
-
2019
- 2019-03-20 WO PCT/JP2019/011847 patent/WO2019182054A1/en active Application Filing
- 2019-03-20 US US16/976,379 patent/US20200407815A1/en not_active Abandoned
- 2019-03-20 KR KR1020207026131A patent/KR102463278B1/en active IP Right Grant
- 2019-03-20 EP EP19772012.1A patent/EP3770291B1/en active Active
- 2019-03-20 JP JP2020507893A patent/JP6919762B2/en active Active
- 2019-03-20 CN CN201980019373.4A patent/CN111868281B/en active Active
Also Published As
Publication number | Publication date |
---|---|
KR102463278B1 (en) | 2022-11-07 |
EP3770291A4 (en) | 2021-12-22 |
CN111868281B (en) | 2022-05-10 |
JPWO2019182054A1 (en) | 2020-12-17 |
EP3770291A1 (en) | 2021-01-27 |
CN111868281A (en) | 2020-10-30 |
KR20200118854A (en) | 2020-10-16 |
US20200407815A1 (en) | 2020-12-31 |
WO2019182054A1 (en) | 2019-09-26 |
JP6919762B2 (en) | 2021-08-18 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP2003222B1 (en) | A quenched and tempered steel for spring-use | |
KR100968938B1 (en) | High strength spring steel and high strength spring heat-treated steel wire | |
KR101826458B1 (en) | Bearing component | |
WO2013151009A1 (en) | Steel wire rod or steel bar having excellent cold forgeability | |
EP2418296A1 (en) | Steel for case hardening which has excellent cold workability and machinability and which exhibits excellent fatigue characteristics after carburizing and quenching, and process for production of same | |
JP5736936B2 (en) | Hot rolled steel bar or wire, and method for producing cold forging steel wire | |
EP3305930A1 (en) | Steel sheet and method for producing same | |
US9187797B2 (en) | Steel part for machine structural use and manufacturing method thereof | |
EP3342892A1 (en) | Mechanical structure steel for cold-working and manufacturing method therefor | |
EP3770291B1 (en) | Steel | |
US8926767B2 (en) | Steel part for machine structural use and manufacturing method thereof | |
JP2010163671A (en) | Steel for soft nitriding | |
JP2010150566A (en) | Steel for vacuum carburizing or vacuum carbo-nitriding | |
EP3173500B1 (en) | Hot-working tool material, method for manufacturing hot-working tool, and hot-working tool | |
EP3211106B1 (en) | Steel wire rod for bearings having excellent drawability and coil formability after drawing | |
JP4464862B2 (en) | Case-hardening steel with excellent grain coarsening resistance and cold workability that can be omitted for soft annealing. | |
EP3483293B1 (en) | Rolled wire rod | |
EP3279361B1 (en) | Hot rolled bar or hot rolled wire rod, component, and manufacturing method of hot rolled bar or hot rolled wire rod | |
JP4464861B2 (en) | Case hardening steel with excellent grain coarsening resistance and cold workability | |
JP7200646B2 (en) | CARBURIZED PARTS, MATERIALS FOR CARBURIZED PARTS, AND PRODUCTION METHOD THEREOF | |
JP7545949B2 (en) | Steel material, steel part, and manufacturing method of steel part | |
KR20220087978A (en) | Wire rod for graphitization heat treatment and graphite steel with excellent cuttability and soft magnetism |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE INTERNATIONAL PUBLICATION HAS BEEN MADE |
|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE |
|
17P | Request for examination filed |
Effective date: 20200925 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
AX | Request for extension of the european patent |
Extension state: BA ME |
|
DAV | Request for validation of the european patent (deleted) | ||
DAX | Request for extension of the european patent (deleted) | ||
A4 | Supplementary search report drawn up and despatched |
Effective date: 20211119 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: EXAMINATION IS IN PROGRESS |
|
17Q | First examination report despatched |
Effective date: 20230310 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R079 Ref document number: 602019045252 Country of ref document: DE Free format text: PREVIOUS MAIN CLASS: C22C0038000000 Ipc: C21D0009320000 Ref legal event code: R079 Ipc: C21D0009320000 |
|
RIC1 | Information provided on ipc code assigned before grant |
Ipc: C21D 1/58 20060101ALN20230613BHEP Ipc: C22C 38/48 20060101ALI20230613BHEP Ipc: C22C 38/32 20060101ALI20230613BHEP Ipc: C22C 38/30 20060101ALI20230613BHEP Ipc: C22C 38/28 20060101ALI20230613BHEP Ipc: C22C 38/26 20060101ALI20230613BHEP Ipc: C22C 38/24 20060101ALI20230613BHEP Ipc: C22C 38/20 20060101ALI20230613BHEP Ipc: C22C 38/04 20060101ALI20230613BHEP Ipc: C22C 38/00 20060101ALI20230613BHEP Ipc: C22C 38/02 20060101ALI20230613BHEP Ipc: C21D 9/00 20060101ALI20230613BHEP Ipc: C21D 1/76 20060101ALI20230613BHEP Ipc: C21D 1/26 20060101ALI20230613BHEP Ipc: C21D 1/18 20060101ALI20230613BHEP Ipc: C22C 38/60 20060101ALI20230613BHEP Ipc: B22D 11/00 20060101ALI20230613BHEP Ipc: B22D 11/20 20060101ALI20230613BHEP Ipc: B22D 11/22 20060101ALI20230613BHEP Ipc: C21D 1/06 20060101ALI20230613BHEP Ipc: C21D 8/06 20060101ALI20230613BHEP Ipc: C21D 9/32 20060101AFI20230613BHEP |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: GRANT OF PATENT IS INTENDED |
|
RIC1 | Information provided on ipc code assigned before grant |
Ipc: C21D 1/58 20060101ALN20230710BHEP Ipc: C22C 38/48 20060101ALI20230710BHEP Ipc: C22C 38/32 20060101ALI20230710BHEP Ipc: C22C 38/30 20060101ALI20230710BHEP Ipc: C22C 38/28 20060101ALI20230710BHEP Ipc: C22C 38/26 20060101ALI20230710BHEP Ipc: C22C 38/24 20060101ALI20230710BHEP Ipc: C22C 38/20 20060101ALI20230710BHEP Ipc: C22C 38/04 20060101ALI20230710BHEP Ipc: C22C 38/00 20060101ALI20230710BHEP Ipc: C22C 38/02 20060101ALI20230710BHEP Ipc: C21D 9/00 20060101ALI20230710BHEP Ipc: C21D 1/76 20060101ALI20230710BHEP Ipc: C21D 1/26 20060101ALI20230710BHEP Ipc: C21D 1/18 20060101ALI20230710BHEP Ipc: C22C 38/60 20060101ALI20230710BHEP Ipc: B22D 11/00 20060101ALI20230710BHEP Ipc: B22D 11/20 20060101ALI20230710BHEP Ipc: B22D 11/22 20060101ALI20230710BHEP Ipc: C21D 1/06 20060101ALI20230710BHEP Ipc: C21D 8/06 20060101ALI20230710BHEP Ipc: C21D 9/32 20060101AFI20230710BHEP |
|
INTG | Intention to grant announced |
Effective date: 20230811 |
|
RIC1 | Information provided on ipc code assigned before grant |
Ipc: C21D 1/58 20060101ALN20230803BHEP Ipc: C22C 38/48 20060101ALI20230803BHEP Ipc: C22C 38/32 20060101ALI20230803BHEP Ipc: C22C 38/30 20060101ALI20230803BHEP Ipc: C22C 38/28 20060101ALI20230803BHEP Ipc: C22C 38/26 20060101ALI20230803BHEP Ipc: C22C 38/24 20060101ALI20230803BHEP Ipc: C22C 38/20 20060101ALI20230803BHEP Ipc: C22C 38/04 20060101ALI20230803BHEP Ipc: C22C 38/00 20060101ALI20230803BHEP Ipc: C22C 38/02 20060101ALI20230803BHEP Ipc: C21D 9/00 20060101ALI20230803BHEP Ipc: C21D 1/76 20060101ALI20230803BHEP Ipc: C21D 1/26 20060101ALI20230803BHEP Ipc: C21D 1/18 20060101ALI20230803BHEP Ipc: C22C 38/60 20060101ALI20230803BHEP Ipc: B22D 11/00 20060101ALI20230803BHEP Ipc: B22D 11/20 20060101ALI20230803BHEP Ipc: B22D 11/22 20060101ALI20230803BHEP Ipc: C21D 1/06 20060101ALI20230803BHEP Ipc: C21D 8/06 20060101ALI20230803BHEP Ipc: C21D 9/32 20060101AFI20230803BHEP |
|
RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: NEISHI, YUTAKA Inventor name: KOYAMA, TATSUYA |
|
GRAS | Grant fee paid |
Free format text: ORIGINAL CODE: EPIDOSNIGR3 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE PATENT HAS BEEN GRANTED |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: FG4D |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: EP |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R096 Ref document number: 602019045252 Country of ref document: DE |
|
REG | Reference to a national code |
Ref country code: IE Ref legal event code: FG4D |
|
REG | Reference to a national code |
Ref country code: SE Ref legal event code: TRGR |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20240325 Year of fee payment: 6 |
|
REG | Reference to a national code |
Ref country code: LT Ref legal event code: MG9D |
|
REG | Reference to a national code |
Ref country code: NL Ref legal event code: MP Effective date: 20240117 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: SE Payment date: 20240314 Year of fee payment: 6 |
|
REG | Reference to a national code |
Ref country code: AT Ref legal event code: MK05 Ref document number: 1650561 Country of ref document: AT Kind code of ref document: T Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: NL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: NL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240517 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240418 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: HR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: RS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240417 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: ES Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: AT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: RS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240417 Ref country code: NO Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240417 Ref country code: LT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: IS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240517 Ref country code: HR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: GR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240418 Ref country code: FI Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: ES Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: BG Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: AT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: PL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: PT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240517 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: PT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240517 Ref country code: PL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: LV Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SM Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: EE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: CZ Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SM Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: SK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: RO Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: EE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: DK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 Ref country code: CZ Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20240117 |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: PL |