CN1989264A - 490 mpa grade high tensile steel for welded structure exhibiting excellent high temperature strength and method for production thereof - Google Patents
490 mpa grade high tensile steel for welded structure exhibiting excellent high temperature strength and method for production thereof Download PDFInfo
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- CN1989264A CN1989264A CNA2005800242067A CN200580024206A CN1989264A CN 1989264 A CN1989264 A CN 1989264A CN A2005800242067 A CNA2005800242067 A CN A2005800242067A CN 200580024206 A CN200580024206 A CN 200580024206A CN 1989264 A CN1989264 A CN 1989264A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 93
- 239000010959 steel Substances 0.000 title claims abstract description 93
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 12
- 230000001747 exhibiting effect Effects 0.000 title abstract 2
- 239000000203 mixture Substances 0.000 claims abstract description 21
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 19
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 12
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 8
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 8
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 6
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 6
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 5
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 5
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 3
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 3
- 238000003466 welding Methods 0.000 claims description 34
- 238000005096 rolling process Methods 0.000 claims description 19
- 238000001816 cooling Methods 0.000 claims description 16
- 229910001566 austenite Inorganic materials 0.000 claims description 14
- 238000010276 construction Methods 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- 238000009825 accumulation Methods 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 abstract description 3
- 229910052698 phosphorus Inorganic materials 0.000 abstract description 3
- 229910052717 sulfur Inorganic materials 0.000 abstract description 3
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 2
- 229910052761 rare earth metal Inorganic materials 0.000 abstract 1
- 230000035945 sensitivity Effects 0.000 abstract 1
- 239000000126 substance Substances 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 24
- 230000000052 comparative effect Effects 0.000 description 10
- 230000006866 deterioration Effects 0.000 description 10
- 239000002245 particle Substances 0.000 description 8
- 239000011248 coating agent Substances 0.000 description 7
- 238000000576 coating method Methods 0.000 description 7
- 239000013078 crystal Substances 0.000 description 7
- 239000002184 metal Substances 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000010953 base metal Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 150000001875 compounds Chemical class 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 208000037656 Respiratory Sounds Diseases 0.000 description 3
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910000532 Deoxidized steel Inorganic materials 0.000 description 2
- 229910000746 Structural steel Inorganic materials 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000009970 fire resistant effect Effects 0.000 description 2
- 238000005098 hot rolling Methods 0.000 description 2
- 230000008520 organization Effects 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000012797 qualification Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 230000035939 shock Effects 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000010561 standard procedure Methods 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000000875 corresponding effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000000881 depressing effect Effects 0.000 description 1
- 230000004069 differentiation Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 239000013081 microcrystal Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910001568 polygonal ferrite Inorganic materials 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 230000001373 regressive effect Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000005382 thermal cycling Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
-
- 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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Metal Rolling (AREA)
Abstract
A 490 MPa grade high tensile steel for a welded structure exhibiting excellent high temperature strength, characterized in that it has a chemical composition that C: not less than 0.005 and less than 0.040 %, Si: 0.5 % or less, Mn: not less than 0.1 and less than 0.5 %, P: 0.02 % or less, S: 0.01 % or less, Mo: 0.3 to 1.5 %, Nb: 0.03 to 0.15 %, Al: 0.06 % or less, N: 0.006 % or less, optionally Cu, Ni, Cr, V, Ti, Ca, REM and Mg may be contained, provided that a weld crack sensitivity composition P<SUB>CM</SUB>, which is defined by the formula: P<SUB>CM</SUB> = C + Si/30 + Mn/20 + Cu/20 + Ni/60 + Cr/20 + Mo/15 + V/10 + 5B, is 0.15 % or less, substantially no B is contained, and the balance: Fe and inevitable impurities, and has a microstructure mainly comprising a mixed structure of ferrite and bainite, wherein bainite accounts for 20 to 90 % of the mixed structure; and a method for producing the above high tensile steel. The above high tensile steel for a welded structure is excellent in the high temperature strength in a temperature range of 600 to 800 DEG C.
Description
Technical field
The present invention relates to be used to build, the general welding structural body of building, ocean structure body, shipbuilding, various storage tank containers etc., in 600 ℃-800 ℃ temperature range in short period of about 1 hour the welded construction of hot strength excellence with high-strength steel and manufacture method thereof.The present invention is an object with slab (Plate Steel) mainly, but also comprises steel pipe and shaped steel etc.
Background technology
The intensity of general steel for welded structures material reduces from about 350 ℃ of beginning intensity, and its permissible temperature is about 500 ℃.Therefore, the occasion that these steel is used for buildingss such as mansion and office building, house, sky parking, in order to ensure the security in fire, the subsidiary obligation that the abundant fireproof coating of enforcement is arranged, in the various decrees relevant with building, the steel temperature can not reach more than 350 ℃ during the regulation fire.This is because the proof stress of above-mentioned steel (yield strength) becomes about 2/3 of normal temperature about 350 ℃, be lower than necessary strength.Practical situation are that such fireproof coating brings very big influence to construction cost.
In order to solve such problem, once developed " fire-resistant steel " (reference example such as spy open flat 2-77523 communique, the spy opens flat 10-68044 communique) of the proof stress when possessing high temperature.Above-mentioned fire-resistant steel is respectively the steel more than 2/3 that the proof stress under 600 ℃, 700 ℃ can be kept standard minimal elastic ultimate stress (yield strength) at normal temperatures.But, all just be illustrated in the proof stress under the specified temp, do not mention fully about the proof stress under the temperature higher than it.Particularly the temperature above 700 ℃ partly enters the humidity province of beginning phase transformation sometimes according to the difference of composition of steel, worries that therefore proof stress (yield strength) sharply descends, and can reflect that designing such stable practical steel makes extremely difficult.
Previous present inventors had once invented steel and the manufacture method (for example opening the 2004-43961 communique with reference to the spy) thereof that can guarantee the hot strength under 700～800 ℃.Owing in composition of steel, must add boron (B), so organizational controls is easy, particularly can reach the low yielding ratio as building structural steel.But such just as is generally known, B makes hardening capacity increase etc., merits and demerits half and half.For example when little heat input welded, welded heat affecting zone significantly hardened, so poor toughness, when weld heat input is excessive, separate out on the contrary, can not effectively utilize the hardening capacity of B at austenite grain boundary, tissue becomes thick, and therefore poor toughness exists the range limited problem of weld heat input.
But, as building structural steel, require to have low yielding ratio from the viewpoint of shock resistance, also the regulation yield ratio is below 80% in " building structure rolling stock " standard of JIS.The previous invention of present inventors is the invention of paying attention to this requirement.But Japan puts down into the corrected building standard method of carrying out in June, 12, is revised as performance provision by former use regulation, has comprised new technology, the material content of practicability in early days.About steel for building, can use following steel by 37 of building standard methods, promptly this article is the 1st: steel that allow to use as the building structure purposes in the JIS material, the 2nd: various performance evaluations as required the performance of steel and the steel of assert through the Minister of Land, Infrastructure and Transport.Therefore, present inventors are not subjected to the constraint of the regulation of the yield ratio in the JIS steel for building, discuss the much less yet excellent steel of hot strength, weldability, the welding zone toughness in wide heat input scope with great concentration, thereby have finished the present application.
Summary of the invention
As described above, utilize the occasion of steel in buildings, therefore common steel can not utilize when having lining or reducing fireproof coating because hot strength (proof stress=yielding stress) is lower, must impose the fireproof coating of high price.In addition, even steel newly developed, it has been the limit that its refractory temperature reaches 600～700 ℃ assurance, wishes that therefore exploitation is at 700～800 ℃ of use of no fireproof coating ground and steel that can omit the fireproof coating operation thus down.
The objective of the invention is to, the welded construction of hot strength excellence of temperature range that is provided at 600 ℃-800 ℃ is with high-strength steel and the industrial manufacture method that can stably supply with this steel.
The present invention achieves the goal by composition of steel and microstructure etc. is limited to suitable scope in order to solve above-mentioned problem, and its main idea is as follows.
(1) a kind of welded construction of hot strength excellence 490MPa grade high-strength steel, it is characterized in that, composition of steel by quality % contain more than the C:0.005% less than 0.040%, below the Si:0.5%, Mn:0.1%～less than 0.5%, below the P:0.02%, below the S:0.01%, Mo:0.3～1.5%, Nb:0.03～0.15%, below the Al:0.06%, below the N:0.006%, and be defined as P
CMThe welding crack sensibility of=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B is formed P
CMBe below 0.15%, do not contain B in fact, its surplus is made up of iron and unavoidable impurities, and microstructure is mixed structure's main body of ferrite and bainite, and the branch rate of its bainite is 20～90%.
(2) according to the welded construction of above-mentioned (1) described hot strength excellence 490MPa grade high-strength steel, it is characterized in that above-mentioned steel further contains any more than a kind or 2 kinds among Cu:0.05～1.0%, Ni:0.05～1.0%, Cr:0.05～1.0%, V:0.01～0.1%, Ti:0.005～0.025%, Ca:0.0005～0.004%, REM:0.0005～0.004%, Mg:0.0001～0.006% by quality %.
(3) according to the welded construction of above-mentioned (1) or (2) described hot strength excellence 490MPa grade high-strength steel, it is characterized in that the leveled circular of the original austenite grains in the cross section parallel with rolling direction of 1/4 thickness position of plate thickness quite footpath is below the 120 μ m.
(4) a kind of welded construction of hot strength excellence manufacture method of 490MPa grade high-strength steel, it is characterized in that, after will comprising the temperature range of the steel billet of above-mentioned (1) or (2) described composition of steel or strand reheat to 1100～1250 ℃, to be defined as more than 30% at the accumulation draught below 1100 ℃, be rolled in the temperature more than 850 ℃, naturally cooling then, perhaps quicken to be cooled to temperature below 650 ℃ from the temperature more than 800 ℃ till.
Embodiment
Below, detailed protocol of the present invention is described.
About hot strength,, when high temperature, promote in the separating out of stable carbonitride by the compound interpolation of Mo and Nb, owing to making dislocation desity, the bainiteization of microstructure increases, and, because replying dislocation, the effect of solid solution Mo and Nb postpones, these are effective to embodying hot strength.Particularly in order to embody the intensity under 700～800 ℃ of these high temperature as target of the present invention, infer by knowledge opinion in the past, must add a large amount of Mo, but this runs counter to guaranteeing weldability and welding zone flexible viewpoint as the excellence of steel for welded structures, has both with hot strength to be difficulty very.
According to discovering of present inventors, suitableization by alloying element and organizational controls, the particularly thermostability by obtaining high temperature parent phase tissue down and suitable coherence precipitating reinforcing effect and postpone dislocation answer effect can obtain weldability, welding zone toughness and the hot strength of excellence simultaneously.
At first, describe according to the reason of the scope qualification composition of steel of claim for the present invention.
C: be the element that steel characteristics is had remarkable influence effect, must be controlled at narrow scope, limited range is more than 0.005%, less than 0.040%.Undercapacity when C quantity not sufficient 0.005% is when C amount is 0.040% when above, in the present invention more than the Mo addition, make weldability, welding zone toughness deterioration, the speed of cooling excessive occasion of while after rolling end of a period, the generation branch rate of bainite increases, and the danger that intensity surpasses improves.In addition, for when being equivalent to the heat of fire, on thermodynamics, stably keep bainite and ferritic mixing parent phase tissue and keep and the coherency of the composite carbon nitrogenize precipitate of Mo, Nb, V, Ti, guarantee strengthening effect, also need to make C less than 0.040%.
Si: the element that is in the deoxidized steel to be contained, owing to have substitutional solution strengthening effect, therefore effective to improving normal temperature strength of parent down, but do not have the particularly effect of hot strength of improvement above 600 ℃.In addition, when adding morely, weldability, welding zone toughness deterioration, so the upper limit is defined as 0.5%.The deoxidation of steel only adopts Ti, Al also to be fine, and from the viewpoint of welding zone toughness and hardening capacity etc., Si is low more preferred more, not necessarily must add.
Mn: be guaranteeing indispensable element on intensity and the toughness, effective as the Mn of substitutional solution strengthening element to improving normal temperature intensity down, but to particularly surpassing 600 ℃ hot strength the too big effect of improving.Therefore, in the steel of the Mo that contains more amount resemble the present invention, from improving weldability, promptly lowering P
CMViewpoint set out, need be less than 0.5%.Suppressing lowly by the upper limit with Mn, also is favourable from the aspect of the center segregation of continuous casting steel billet.Moreover, about lower limit,, need to add more than 0.1% from the intensity of mother metal, the angle of toughness adjustment.
P and S: in steel of the present invention, be impurity, low more preferred more.The P segregation encourages intercrystalline failure in crystal boundary, and it is the sulfide of representative that S forms with MnS, make the toughness deterioration of mother metal and welding zone, so the upper limit separate provision of P and S is 0.02%, 0.01%.
Mo: in steel of the present invention, from the viewpoint that embodies and keep hot strength be with Nb side by side must indispensable element.Single viewpoint from hot strength, add more morely favourable more, if but also consider strength of parent, weldability, welding zone toughness, then should limit.In the present invention who suppresses C low, if P described later
CMScope in (below 0.16%), then Mo allows till 1.5%.Its lower limit is even for the compound interpolation of Nb or further add and described laterly also stably guarantee hot strength to improving the effective V of hot strength, Ti, need to add more than 0.3%.
Nb: be must be with the element of the compound interpolation of Mo.At first, as the general effect of Nb, Nb be make that austenitic recrystallization temperature raises, useful element aspect the controlled rolling effect when bringing into play hot rolling to greatest extent.The austenitic grain refining of the heating when in addition, also helping reheat before rolling.And, owing to precipitation strength with suppress dislocation and reply and have the effect that improves hot strength, by with the compound interpolation of Mo, help further to improve hot strength.When less than 0.03%, the precipitation-hardening under 700 ℃ and 800 ℃ and to suppress the regressive effect of dislocation little surpassing at 0.15% o'clock, reduces with respect to addition hardened degree, and is not only undesirable economically, and also deterioration of the toughness of welding zone.For these reasons, Nb is defined as 0.03～0.15% scope.
Al: the element that generally is in the deoxidized steel to be contained, but deoxidation only adopts Si or Ti just enough, and in the present invention, its lower limit does not limit (comprising 0%).But when the Al amount increased, the not only cleanliness factor variation of steel, and the toughness of welding zone is deterioration also, so the upper limit is defined as 0.06%.
N: be the element that contains in steel as unavoidable impurities, in the occasion of adding Nb and Ti described later, it combines, forms carbonitride with Nb, and intensity is increased, and forms TiN, improves the performance of steel.Therefore N amount needs are minimum is 0.001%.But the increase of N amount is harmful to welding zone toughness, weldability, is limited to 0.006% on it in the present invention.Moreover this upper limit might not be the meaning of the boundary on the characteristic, is the numerical value that limits in the scope that present inventors confirm.
Secondly, Cu, Ni, Cr, V, Ti and the Ca that can contain as required, interpolation reason and the addition scope thereof of REM, Mg are described.
Further adding the main purpose of these elements in basal component, is in order to improve characteristics such as intensity, toughness under the situation of the advantageous feature of not damaging steel of the present invention.Therefore, these elements are its addition elements of confined character naturally and understandably.
Cu: can not cause significant detrimentally affect, and the intensity of mother metal, toughness are improved to weldability, welding zone toughness.In order to make these effects obtain performance, must add more than 0.05% at least.On the other hand, surplus is added not only weldability deterioration, and also can increase the danger that the Cu crackle takes place during hot rolling, so the upper limit is defined as 1.0%.Moreover known Cu crackle itself can add an amount of Ni according to Cu content to be avoided, and weldability also with other alloying element amount headed by the C amount has relation, so the upper limit not necessarily has the meaning of boundary.
Ni: show with the roughly same effect of Cu, particularly raising to have very big effect to base metal tenacity.In order to obtain these effects effectively, must add more than 0.05% at least.On the other hand, superfluous interpolation, even if Ni also makes the weldability deterioration, Ni is the element than higher price simultaneously, therefore also can damage economy, so in the present invention, considers that also with 490MPa level steel be target, is decided to be the upper limit with 1.0%.
Cr: can add as required for strength of parent is improved.In order to sneak into difference clearly and to obtain effect effectively, need to add minimum more than 0.05% with trace from the doped element of waste material etc.Too much interpolation, the same with other element, make weldability and welding zone toughness deterioration, so the upper limit is defined as 1.0%.
Above-mentioned Cu, Ni, Cr, not only the mechanical characteristics to mother metal is effective, and is also effective to weathering resistance, under such purpose, preferably adds on one's own initiative in can not damaging weldability, welding zone flexible scope significantly.
V: be also to comprise improving hot strength, having and the roughly same effect of Nb and the element of effect, but compare that its effect is little with Nb.In addition, also include P in from V
CMKnow in the formula, hardening capacity, weldability are also impacted.Therefore, in order to obtain the additive effect of V conscientiously, when undergage is decided to be 0.01%,, the upper limit is defined as 0.1% in order to get rid of detrimentally affect.
Ti: the same with Nb, V etc. effective to improving hot strength.In addition, particularly, preferably add to mother metal and the strict occasion of welding zone flexible.Its reason is, at Al amount (for example below 0.003%) after a little while, Ti combines, forms with Ti with O
2O
3Be the precipitate of principal constituent, become the ferritic nuclear of generation intragranular phase transformation, welding zone toughness is improved.In addition, Ti combine, form TiN with N and in slab fine separating out, thickization of the austenite crystal when suppressing heating, effective to the miniaturization of rolling structure.In addition, the fine TiN that exists in the steel plate makes welded heat affecting zone organize grain refining when welding.In order to obtain these effects, it is 0.005% that Ti needs minimum.But, form TiC in the time of too much, make low-temperature flexibility, weldability deterioration, so be limited to 0.025% on it.
Ca, REM: S combines with impurity, has the effect that improves toughness, suppresses the crackle that is caused by diffusible hydrogen of welding zone, but forms thick inclusion too much the time, and toughness is caused detrimentally affect, therefore they all is limited to 0.0005～0.004% scope.Because two kinds of elements have roughly the same effect,, add the either party at least and get final product therefore in order to obtain above-mentioned effect.
Mg: in welded heat affecting zone, have and suppress that austenite crystal is grown up, the effect of crystal grain thinning, the highly malleablized that can seek the welding zone.In order to obtain such effect, need Mg 〉=0.0001%.On the other hand, when addition increases, diminish with addition corresponding effects surplus, and lose economy, so the upper limit is defined as 0.006%.
Moreover in the present invention, B has a mind to add, if surpass the level that contains as the pollutent in the steel making working procedure, it is necessary in fact not containing B.The interpolation of B trace can significantly improve hardening capacity, therefore is being used for the occasion of high-strength steel, is being favourable aspect control tissue, the raising intensity, but is also having the danger of weldability of making and welding zone toughness deterioration simultaneously.The present invention except hot properties, also be purpose as the use properties of steel for welded structures with further raising, taboo has a mind to add B, in fact regulation does not contain B.
When even each composition with steel limits like that according to above-mentioned, composition is integral body when also improper, can not obtain the excellent specific property as feature of the present invention.Particularly, seek to make weldability, welding zone toughness to improve greatly, therefore with P from the previous patent of present inventors (Japanese patent application 2004-43961 number)
CMValue be defined as below 0.15%.At this, so-called P
CM, be the index of expression welding crack sensibility, define by following formula.
P
CM＝C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B
Usually, P
CMLow more, weldability is excellent more, if be below 0.22%, does not need preheating (in order to prevent welding cold cracking) when then we can say welding.For high-strength steel, wherein for the hot strength excellence resemble the present invention and the high-strength steel that do not contain the element B that significantly improves hardening capacity in fact, P
CMBe to be extremely low value below 0.15%.
In addition, in the present invention, also limit microstructure.Weldability and welding zone toughness can be guaranteed when only limiting composition of steel, but hot properties can not be satisfied, especially as the fundamental characteristics (particularly intensity) of 490MPa level steel as the excellence of steel for welded structures.Therefore, as the microstructure that is suitable for the object of the invention, be mixed structure's main body of ferrite and bainite, the branch rate of bainite wherein is limited to 20～90%.This is based on when bainite branch rate is low, be difficult to guarantee the normal temperature strength and the hot strength of 490MPa level, when bainite divides rate too high, the danger of strength range that surpasses the 490MPa level steel of defined such as JIS increases these present inventors' experimental result, for clear and definite feature of the present invention limits, might not have the meaning of boundary.
Moreover these microstructures are microstructures of representing thickness of slab cross-wise direction 1/4 thickness position.In addition, as the appellation of " bainite " of organization name, be that those skilled in the art are widely used, from various form of changing etc., measuring when dividing rate, on the specific point in this zone, have the indefinite possibility of generation.This occasion, the method that the another kind tissue " ferrite " on the also useful organizational composition is judged.The ferrite branch rate of this occasion is 10～80%.At this alleged ferrite is Polygons or the quasi-polygonal ferrite (not comprising acicular ferrite) that does not contain cementite.
Austenite particle diameter before the phase transformation after rolling, the toughness (high malleableize) for the steel of controlling the higher Mo of the such interpolation of the present invention needs to limit aptly.This austenite crystal is tiny more, and final phase-change organization is also fine more, and toughness is improved.In order to obtain, this austenite particle diameter of thickness of slab cross-wise direction 1/4 thickness position of the final rolling direction of steel plate is defined as below the 120 μ m by the leveled circular equivalent diameter no less than the toughness of common low Mo steel.Different according to thickness of slab with composition of steel, even also there are the 120 μ m of surpassing also can obtain sufficient flexible situation, but, might not be the implication of boundary therefore owing to guaranteeing that as stablizing effectively the flexible particle diameter limits.Moreover it is quite a few that the differentiation of austenite particle diameter may not be easy to situation.In such occasion, use with thickness of slab 1/4 thickness position as the center, with the notched shock test sheet of the vertical direction of the final rolling direction of steel plate sampling, the 2mmV type notched specimen of for example JIS Z 2202 etc., surface of fracture unit in the time of will making its brittle rupture under fully low temperature is defined as interchangeable effective size of microcrystal of reading to the austenite particle diameter, measure its leveled circular equivalent diameter, needing too in this occasion is below the 120 μ m.
By above-mentioned such tissue that limits (tissue, tissue branchs rate, original austenite particle diameter etc.) with the various characteristics of the excellence of the target of the present invention headed by the hot properties, can be by limiting manufacture method and acquisition easily like that according to following.
Have the steel billet of composition of steel of regulation or the reheat of strand, be limited to 1100～1250 ℃ temperature range.Lower limit is because be the 1st purpose to guarantee hot properties, for the V, the Ti that make Mo, Nb and add as required form solid solution condition for 1100 ℃.For this purpose, the reheat temperature is high more preferred more, but thickization of austenite crystal of heating is not preferred from the viewpoint of base metal tenacity, so the upper limit is defined as 1250 ℃.
The qualification of rolling condition is in order directly the austenite particle diameter before the rolling back phase transformation to be become thinner crystal grain according to above-mentioned such control, mainly in order to ensure toughness.Need make at the accumulation draught below 1100 ℃ when for this reason, rolling is more than 30%.Rolling finishing temperature, the lower limit temperature as the V, the Ti that are used for when the depressing of cold zone Mo, Nb or add as required separate out with the carbide form is limited to more than 850 ℃.
Cooling after rolling also should limit from the viewpoint of organizational controls.Though also depend on composition of steel, in the occasion of steel thinner thickness, even the speed of cooling of employing naturally cooling degree also can access the tissue of regulation, but when steel thickness was thicker, when adopting naturally cooling, speed of cooling was slack-off, needed to quicken cooling sometimes.The acceleration of this occasion cooling, the most general in the Plate Steel manufacturing is water-cooled, but not necessarily must water-cooled.In addition, quickening cooling purpose is to improve the cooling rate of phase change zone for organizational controls, therefore need quicken to be cooled to temperature below 650 ℃ from the temperature more than 800 ℃.
Moreover, in the present invention, so-called hot strength, with 600～800 ℃ is target, its quantitative target is, the ratio p (=high temperature yield stress/normal temperature yielding stress) of the yielding stress during high temperature and normal temperature yielding stress, the steel temperature T (℃) be that 600 ℃～800 ℃ scope is p 〉=-0.0033 * T+2.80.
Embodiment
Adopt converter-continuous casting-slab operation to make the steel plate (thickness 12～80mm) of various composition of steel, estimate its mechanical properties and weldability, welding zone toughness, investigated the simulated HAZ toughness that is equivalent to little heat input welding and ultra-large linear energy input welding that has or not and utilize the welding analog thermal cycling to obtain based on the root crack in the oblique Y type groove welding crack test of JIS standard.Table 1 express respectively comparative example and example of the present invention composition of steel, create conditions, the investigation result of tissue and various characteristics.
Example of the present invention all satisfies limited range of the present invention, comprises that the various characteristics of hot strength, simulated HAZ toughness is also extremely good.In contrast to this, comparative example because composition of steel, create conditions, tissue etc. at least a more than broken away from limited range of the present invention, it is poor therefore to know with the present invention's example specific characteristic.That is, comparative example 19 is because the C amount is low, so bainite divides rate low, and normal temperature strength, hot strength (ratio) are also all lower.Comparative example 20 is owing to carbon amount height, so bainite divides the rate height, the normal temperature strength height.In addition, base metal tenacity, simulated HAZ toughness are also poor.Comparative example 21 is because the Mo amount is low, to quicken cooling beginning temperature also low, so bainite divides rate also low and hot strength (ratio) is low.Comparative example 22 is because the Nb amount is low, Heating temperature, rolling finishing temperature are also low, and quickens cooling and stop the temperature height, so normal temperature strength, hot strength (ratio) are low.Therefore comparative example 23 is adopting acceleration refrigerative occasion owing to added B, and bainite divides the rate height, and base metal tenacity is poor.In addition, simulated HAZ toughness is also poor.Comparative example 24 is because high, the P of Mn amount
CMAlso high, and also low at the accumulation draught below 1100 ℃, so bainite branch rate increases, and becomes superfluous as its strength of parent of 490MPa level steel, base metal tenacity, simulated HAZ toughness are also poor.
In addition, though the root crack in the oblique Y type groove welding crack test is the P of comparative example 24
CMBe higher than limited range of the present invention, but be about 0.185%, root crack does not all take place in which kind of situation.
Table 1
| Distinguish | Steel | Normal temperature yielding stress (MPa) | Normal temperature tensile stress (MPa) | The ratio of yielding stress and normal temperature yielding stress, p | vTrs (℃) | Bainite divides rate (%) in the mother metal tissue | Original austenite particle diameter (μ m) | Simulated HAZ toughness vE 0(J) | Root crack | |||
| 600℃ | 700℃ | 800℃ | Thermal process 1 | Thermal process 2 | ||||||||
| Example of the present invention | 1 | 476 | 541 | 0.87 | 0.61 | 0.25 | -45 | 54 | 50 | 89 | 69 | Flawless |
| 2 | 451 | 537 | 0.85 | 0.57 | 0.24 | -31 | 52 | 71 | 82 | 62 | Flawless | |
| 3 | 438 | 534 | 0.86 | 0.57 | 0.25 | -36 | 61 | 63 | 97 | 84 | Flawless | |
| 4 | 442 | 533 | 0.87 | 0.55 | 0.25 | -40 | 29 | 47 | 87 | 64 | Flawless | |
| 5 | 407 | 509 | 0.87 | 0.55 | 0.25 | -35 | 37 | 74 | 83 | 67 | Flawless | |
| 6 | 421 | 547 | 0.90 | 0.58 | 0.24 | -31 | 65 | 83 | 79 | 65 | Flawless | |
| 7 | 425 | 545 | 0.88 | 0.57 | 0.22 | -34 | 57 | 109 | 78 | 69 | Flawless | |
| 8 | 433 | 548 | 0.86 | 0.54 | 0.27 | -37 | 60 | 68 | 80 | 88 | Flawless | |
| 9 | 419 | 530 | 0.86 | 0.59 | 0.25 | -30 | 42 | 55 | 82 | 65 | Flawless | |
| 10 | 410 | 516 | 0.85 | 0.59 | 0.24 | -32 | 48 | 61 | 96 | 63 | Flawless | |
| 11 | 431 | 553 | 0.85 | 0.58 | 0.24 | -30 | 51 | 97 | 88 | 69 | Flawless | |
| 12 | 424 | 523 | 0.85 | 0.59 | 0.22 | -28 | 45 | 60 | 90 | 83 | Flawless | |
| 13 | 451 | 564 | 0.85 | 0.58 | 0.25 | -35 | 64 | 64 | 79 | 86 | Flawless | |
| 14 | 462 | 570 | 0.84 | 0.58 | 0.24 | -32 | 67 | 52 | 86 | 71 | Flawless | |
| 15 | 433 | 528 | 0.86 | 0.59 | 0.25 | -38 | 59 | 67 | 82 | 68 | Flawless | |
| 16 | 415 | 532 | 0.86 | 0.62 | 0.24 | -35 | 65 | 55 | 83 | 74 | Flawless | |
| 17 | 442 | 526 | 0.84 | 0.62 | 0.24 | -32 | 62 | 58 | 91 | 67 | Flawless | |
| 18 | 480 | 571 | 0.85 | 0.61 | 0.23 | -37 | 76 | 46 | 88 | 65 | Flawless | |
| Comparative example | 19 | 322 | 478 | 0.69 | 0.46 | 0.14 | -47 | 16 | 59 | 78 | 96 | Flawless |
| 20 | 517 | 631 | 0.81 | 0.52 | 0.17 | -3 | 96 | 62 | 31 | 22 | Flawless | |
| 21 | 392 | 501 | 0.72 | 0.44 | 0.15 | -49 | 18 | 51 | 80 | 56 | Flawless | |
| 22 | 358 | 484 | 0.78 | 0.45 | 0.14 | -21 | 47 | 70 | 83 | 61 | Flawless | |
| 23 | 465 | 566 | 0.86 | 0.57 | 0.23 | -3 | 95 | 68 | 13 | 16 | Flawless | |
| 24 | 481 | 628 | 0.83 | 0.55 | 0.22 | -1 | 93 | 132 | 38 | 19 | Flawless |
The tension test sheet: when thickness of slab 40mm is following be JIS Z 2201 1A number (total thickness),
Thickness of slab is No. 22014, JIS Z (1/4 thickness) when surpassing 50mm; With the vertical direction of rolling direction
Charpy impact test sheet: JIS Z 2202 2mmV type breach, rolling direction
The high temperature tension test sheet: pole (Φ 8mm or Φ 10mm), 1/4 thickness position, with the vertical direction of rolling direction
Be 8 seconds thermal process 1:1400 ℃ * 1 second, 800 ℃ → 500 ℃ cooling time
Be 330 seconds thermal process 2:1400 ℃ * 30 seconds, 800 ℃ → 500 ℃ cooling time
Utilizability on the industry
The steel that employing is made based on composition of steel of the present invention and manufacture method, microscopic structure also satisfies limited range of the present invention, elevated temperature strength much less, weldability and weld zone toughness are also all excellent, this is by the embodiment real example. Namely show, can have considerably beyond existing assurance until the steel for welded structures of the hot properties of the refractory steel of the hot properties about 600 ℃ industrial stably a large amount of production, for example, as building occupancy, can expect applicable building and complete significantly expansion without fireproof coating.
Claims (4)
1. the welded construction of a hot strength excellence is with 490MPa grade high-strength steel, it is characterized in that, composition of steel by quality % contain more than the C:0.005% less than 0.040%, below the Si:0.5%, Mn:0.1%～less than 0.5%, below the P:0.02%, below the S:0.01%, Mo:0.3～1.5%, Nb:0.03～0.15%, below the Al:0.06%, below the N:0.006%, and be defined as P
CMThe welding crack sensibility of=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B is formed P
CMBe below 0.15%, do not contain B in fact, its surplus is made up of iron and unavoidable impurities, and microstructure is mixed structure's main body of ferrite and bainite, and the branch rate of its bainite is 20～90%.
2. the welded construction of hot strength excellence according to claim 1 490MPa grade high-strength steel, it is characterized in that above-mentioned steel further contains any more than a kind or 2 kinds among Cu:0.05～1.0%, Ni:0.05～1.0%, Cr:0.05～1.0%, V:0.01～0.1%, Ti:0.005～0.025%, Ca:0.0005～0.004%, REM:0.0005～0.004%, Mg:0.0001～0.006% by quality %.
3. the welded construction of hot strength excellence according to claim 1 and 2 490MPa grade high-strength steel, it is characterized in that the leveled circular of the original austenite grains in the cross section parallel with rolling direction of 1/4 thickness position of plate thickness quite footpath is below the 120 μ m.
4. the welded construction of a hot strength excellence is with the manufacture method of 490MPa grade high-strength steel, it is characterized in that, after will comprising the temperature range of the steel billet of claim 1 or 2 described composition of steel or strand reheat to 1100～1250 ℃, to be defined as more than 30% at the accumulation draught below 1100 ℃, be rolled in the temperature more than 850 ℃, naturally cooling then, perhaps quicken to be cooled to temperature below 650 ℃ from the temperature more than 800 ℃ till.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004213511A JP4864297B2 (en) | 2004-07-21 | 2004-07-21 | 490 MPa class high strength steel for welded structure excellent in high temperature strength and method for producing the same |
| JP213511/2004 | 2004-07-21 |
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| Publication Number | Publication Date |
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| CN1989264A true CN1989264A (en) | 2007-06-27 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNA2005800242067A Pending CN1989264A (en) | 2004-07-21 | 2005-07-08 | 490 mpa grade high tensile steel for welded structure exhibiting excellent high temperature strength and method for production thereof |
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| Country | Link |
|---|---|
| US (1) | US20060016526A1 (en) |
| EP (1) | EP1790749A1 (en) |
| JP (1) | JP4864297B2 (en) |
| CN (1) | CN1989264A (en) |
| TW (1) | TWI297732B (en) |
| WO (1) | WO2006009091A1 (en) |
Cited By (3)
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| CN101775561A (en) * | 2010-03-19 | 2010-07-14 | 江苏省沙钢钢铁研究院有限公司 | Low-yield-ratio high-strength thick plate and preparation process thereof |
| CN101857939A (en) * | 2010-06-13 | 2010-10-13 | 攀钢集团钢铁钒钛股份有限公司 | Low-alloy structural strip steel with high strength and high toughness and production method thereof |
| CN101613840B (en) * | 2008-06-23 | 2011-03-30 | 宝山钢铁股份有限公司 | Super-thick steel plate with obdurability matching and excellent high-temperature performance and manufacturing method thereof |
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| JP2760191B2 (en) * | 1991-12-20 | 1998-05-28 | 住友金属工業株式会社 | Manufacturing method of high weathering steel for steel building with excellent high temperature strength characteristics |
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| JP4348102B2 (en) * | 2002-05-20 | 2009-10-21 | 新日本製鐵株式会社 | 490 MPa class high strength steel excellent in high temperature strength and manufacturing method thereof |
| CN101082105A (en) * | 2002-03-29 | 2007-12-05 | 新日本制铁株式会社 | High tensile steel excellent in high temperature strength and method for production thereof |
| JP7056044B2 (en) * | 2017-09-11 | 2022-04-19 | コニカミノルタ株式会社 | Paper processing equipment, image forming system and program |
-
2004
- 2004-07-21 JP JP2004213511A patent/JP4864297B2/en not_active Expired - Fee Related
-
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- 2005-07-08 CN CNA2005800242067A patent/CN1989264A/en active Pending
- 2005-07-08 WO PCT/JP2005/013101 patent/WO2006009091A1/en active Application Filing
- 2005-07-08 EP EP05760159A patent/EP1790749A1/en not_active Withdrawn
- 2005-07-20 TW TW094124502A patent/TWI297732B/en not_active IP Right Cessation
- 2005-08-29 US US11/215,413 patent/US20060016526A1/en not_active Abandoned
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| CN101613840B (en) * | 2008-06-23 | 2011-03-30 | 宝山钢铁股份有限公司 | Super-thick steel plate with obdurability matching and excellent high-temperature performance and manufacturing method thereof |
| CN101775561A (en) * | 2010-03-19 | 2010-07-14 | 江苏省沙钢钢铁研究院有限公司 | Low-yield-ratio high-strength thick plate and preparation process thereof |
| CN101857939A (en) * | 2010-06-13 | 2010-10-13 | 攀钢集团钢铁钒钛股份有限公司 | Low-alloy structural strip steel with high strength and high toughness and production method thereof |
Also Published As
| Publication number | Publication date |
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| TWI297732B (en) | 2008-06-11 |
| JP2006028628A (en) | 2006-02-02 |
| EP1790749A1 (en) | 2007-05-30 |
| WO2006009091A1 (en) | 2006-01-26 |
| US20060016526A1 (en) | 2006-01-26 |
| TW200606260A (en) | 2006-02-16 |
| JP4864297B2 (en) | 2012-02-01 |
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