Nothing Special   »   [go: up one dir, main page]

US20170130304A1 - Alloy with High Core Hardness Suitable for Rapid Nitriding - Google Patents

Alloy with High Core Hardness Suitable for Rapid Nitriding Download PDF

Info

Publication number
US20170130304A1
US20170130304A1 US14/933,467 US201514933467A US2017130304A1 US 20170130304 A1 US20170130304 A1 US 20170130304A1 US 201514933467 A US201514933467 A US 201514933467A US 2017130304 A1 US2017130304 A1 US 2017130304A1
Authority
US
United States
Prior art keywords
steel
weight
nitriding
alloy
alloy steel
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.)
Abandoned
Application number
US14/933,467
Other languages
English (en)
Inventor
Zachary S. Birky
Robert Meyer
Robert Bierman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Caterpillar Inc
Original Assignee
Caterpillar Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Caterpillar Inc filed Critical Caterpillar Inc
Priority to US14/933,467 priority Critical patent/US20170130304A1/en
Assigned to CATERPILLAR INC. reassignment CATERPILLAR INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: Bierman, Robert, BIRKY, ZACHARY S., MEYER, ROBERT
Priority to US15/292,985 priority patent/US10272960B2/en
Priority to DE102016120608.3A priority patent/DE102016120608A1/de
Publication of US20170130304A1 publication Critical patent/US20170130304A1/en
Abandoned legal-status Critical Current

Links

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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • 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
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat 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
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0257—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment with diffusion of elements, e.g. decarburising, nitriding
    • 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
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
    • 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
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • 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
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • 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
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • 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
    • C22C38/24—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
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • 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
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces

Definitions

  • the disclosure relates to generally to a low alloy steel with high core hardness and, more particularly, to a low alloy steel with high core hardness suitable for rapid nitriding.
  • Nitriding is a highly specialized surface hardening treatment that produces a thin but high hardness case on a wide variety of steels.
  • the significant advantages of nitriding over other surface hardening processes are that the case hardness is developed without quenching and that the attendant distortion problems can be minimized. Finishing operations can be eliminated or held to a minimum.
  • Nitrided surfaces are highly wear resistant and provide anti-galling properties.
  • the nitrided surfaces of steel parts improve the corrosion resistance of the parts.
  • An additional advantage of nitriding is that the surface hardness is resistant to softening by elevated temperatures up to the nitriding temperature.
  • a nitriding process involves the diffusion of nitrogen into the base steel.
  • a typical nitriding temperature is about 525° C.
  • the surface hardening during the nitriding process does not require quenching. Core properties are not affected by the nitriding process provided the prior tempering temperature is higher than the nitriding temperature.
  • AISI 4140 is most commonly used low alloy steel for nitriding applications, which usually has a core hardness of HRC 28-32 when quenched and subsequently tempered at temperatures higher than the nitriding temperature.
  • the AISI 4340 has more alloy elements compared to the AISI 4140.
  • the AISI 4340 can have a core hardness of HRC 39 and is used for steel parts requiring a high hardenability steel.
  • These AISI 4140 and AISI 4340 type steels contain silicon in amounts of about 0.15-0.35% by weight and nickel in amounts of about 1-2% by weight.
  • the Nitralloy N which is a commercially available, is specifically designed for nitriding.
  • the Nitralloy may be quenched and tempered to achieve typical core hardnesses of about HRC 20-25.
  • the advantages of the nitralloy steels are their high response to nitriding and the very high surface hardness equivalent to about HRC 62-65.
  • the Nitralloy requires nickel in amounts of 3-5% by weight.
  • the conventional medium-carbon alloy steels such as AISI 4140, AISI 4340, and Nitralloy type steels are considered as nitriding alloys since they enjoy the benefits of nitriding.
  • these alloys require expensive alloy elements such as nickel and molybdenum.
  • a nitriding alloy steel is disclosed in U.S. Pat. No.
  • the '049 patent is directed to a through hardening nitriding grade alloy steel including aluminum in a range of about 0.07% to 0.30% by weight and vanadium in a range of about 0.03 to 0.20% by weight.
  • the alloy steel in the '049 patent is similar to AISI 4140 with a typical core hardness of HRC about 28-32 when tempered at 530° C. A higher core hardness could be achieved if the tempering temperature were reduced. However, the nitriding temperature would also need to be reduced to be less than the tempering temperature. Lower nitriding temperatures significantly increase the nitriding cycle time and hence the nitriding process costs. In addition, the hardness gradient in a nitrided part as well as the surface hardness depend heavily on the prior hardness. The alloy steel in the '049 patent and AISI 4140 typically have surface hardnesses of about HRC 56-58 after nitriding.
  • the alloy steel disclosed in the '049 patent may not contain large amounts of expensive elements such as nickel and molybdenum, nitriding such an alloy steel takes substantially less time to achieve desired hardened depth that AISI 4140 steel achieves at the comparable nitriding temperature and furnace atmosphere.
  • the alloy steel in the '049 patent does not contain sufficient alloying elements to meet the elevated core hardness desired for some highly loaded components.
  • a through hardening low alloy steel according to the disclosure provides a composition that is economical, adaptable to a variety of quench mediums, maintains high core hardness after tempering and has improved nitriding characteristics.
  • the initial cost of the low alloy steel is reduced due to the reduction of molybdenum, nickel or other strength-improving alloys.
  • the disclosure is directed to an alloy steel suitable for rapid nitriding, having a steel composition including by weight (%): Carbon: from 0.2 to 0.4; Manganese: from 0.50 to 1.60; Silicon: from 0.50 to 2.0; Chromium: from 0.40 to 1.5; Vanadium: from 0.03 to 0.30; Aluminum: from 0.07 to 0.30; and iron and other residual elements: balance.
  • the disclosure is directed to an alloy steel suitable for rapid nitriding, having a steel composition including by weight (%): Carbon: from 0.2 to 0.4; Manganese: from 0.50 to 1.60; Silicon: from 0.50 to 2.0; Chromium: from 0.40 to 1.5; Vanadium: from 0.03 to 0.30; Aluminum: from 0.07 to 0.30; Nickel: 1.0% or less; Molybdenum: 0.1% or less; and iron and other residual elements: balance.
  • the disclosure is directed to a method for manufacturing a steel product made of an alloy steel suitable for rapid nitriding, including: hot deforming the steel alloy to obtain the steel product; heat-treating the hot deformed steel product; tempering the heat-treated steel product; and rapidly nitriding the tempered steel product, where the alloy steel has a steel composition including by weight(%): Carbon: from 0.2 to 0.4; Manganese: from 0.50 to 1.60; Silicon: from 0.50 to 2.0; Chromium: from 0.40 to 1.5; Vanadium: from 0.03 to 0.30; Aluminum: from 0.07 to 0.30; and iron and other residual elements: balance.
  • FIG. 1 shows a table comparing exemplary alloys according to the disclosure with other conventional alloys.
  • FIG. 2 is a schematic diagram of an exemplary disclosed process.
  • FIG. 3 is a schematic diagram of another exemplary disclosed process.
  • a low alloy steel for rapid nitriding treatment is disclosed.
  • the low alloy steel is economically produced without requiring many expensive elements such as molybdenum and nickel.
  • the low alloy steel contains medium-carbons and strong nitride-forming elements such as aluminum.
  • Nitriding is a surface-hardening heat treatment that introduces nitrogen into the surface of the low alloy steel.
  • the aluminum forms AlN particles that strain the ferrite lattice, impede dislocation movement, and thereby strengthen the low alloy steel.
  • the low alloy steel contains silicon in an amount of 0.5% or higher by weight.
  • a combination of nitride-forming elements and silicon according to the disclosure provides the low alloy steel with desired core hardness without additions of significant amounts of expensive alloy elements such as Ni, Mo and Ti.
  • a low alloy steel according to various implementations of the disclosure may have a chemical composition as listed in Table I:
  • carbon (C) contributes to the attainable hardness level as well as the depth of hardening of steel.
  • a desired amount of carbon in the steel assures resistance to quench cracking and an adequate response to nitriding.
  • the amount of carbon is at least 0.20% or higher by weight.
  • an excessive amount of carbon e.g., higher than 0.40% by weight in the steel
  • the amount of carbon is in a range of from 0.20% to 0.40% by weight.
  • the amount of carbon may be in a range of from 0.24% to 0.34% by weight.
  • a steel article formed with an alloy steel according to the disclosure may be quenchable in water, oil, gas or the like, whichever is more convenient.
  • Manganese (Mn) contributes to deep hardenability and is therefore present in most hardenable alloy steel grades.
  • the amount of manganese is at least 0.5% or higher by weight to assure adequate core hardness.
  • an excessive amount of manganese e.g., higher than 1.60% by weight in the steel
  • the amount of manganese is in a range of from 0.5% to 1.6% by weight.
  • a lower amount of manganese of 1.5% or lower by weight may be considered.
  • a narrower range of manganese from 1.00% to 1.30% by weight may be contemplated as well.
  • Chromium (Cr) contributes to hardenability of steel and is a nitride former thereby enhancing nitride response.
  • the amount of chromium is 0.40% or higher by weight.
  • the maximum amount of chromium is limited to 1.5% by weight. In some aspect, a narrower range of chromium from 0.9% to 1.2% by weight may be contemplated as well.
  • Aluminum (Al) contributes to hardenability and is a good nitrider former. If the amount of aluminum in the steel is too small, not only is there little observable improvement in either hardenability or nitride response but also the benefits are inconsistent. In an aspect of the disclosure, the amount of aluminum is 0.07% or higher by weight. It has also been found that while increasing the amount of aluminum is beneficial to nitrideability, the tendency for case embrittlement also increases. In one aspect, an upper amount of aluminum may be 2.0% by weight. In some aspect, the amount of aluminum in the steel may be 1.0% or less. A smaller amount of aluminum, 0.3% or less by weight, may be contemplated as well.
  • Vanadium (V) is also an element present in the steel.
  • an amount of at least 0.03% by weight is present to realize a consistently measurable enhancement of case and core hardness.
  • An upper limit of vanadium may be 2% by weight.
  • Vanadium is an expensive element.
  • the amount of vanadium may be in a range of from 0.03% to 0.30% by weight. A range of from 0.05% to 0.10% by weight may be contemplated to make the best economic use of this element.
  • an amount of vanadium of 0.1% or higher and 0.2% or less by weight may also be contemplated in the presence of a desired amount of silicon in the steel.
  • Silicon is an element that enhances core hardness of the steel.
  • the amount of silicon is present in an amount of 0.5% or higher by weight.
  • An excessive addition however, adversely affects not only the toughness and the hardness of the steel, but also other mechanical properties such as cold-forging properties and machinability. Therefore, the limits of silicon are 2.0% or lower by weight. In some aspect, a narrower range of from 0.6% to 2.0% by weight may be contemplated. In various aspects, a range of from 1.0% to 2.0% by weight may be considered as well. It has been found that the unique combination of aluminum, vanadium and silicon within the ranges according to the disclosure greatly contributes to high core hardness and good nitride response.
  • Nickel (Ni) and molybdenum (Mo) are expensive elements. From the economic standpoint, it would be desirable to reduce the amounts of nickel and molybdenum. According to an aspect of the disclosure, an amount of nickel and/or molybdenum is 1% or less by weight. In some aspect, the total amount of nickel and molybdenum may be 1% or less by weight. In the presence of a desired amount of silicon according to the disclosure, each of nickel and molybdenum may be further reduced 0.1% or less by weight. In various aspects, each of nickel and molybdenum may be reduced 0.01% or less by weight.
  • Titanium (Ti) and niobium (Nb) are sometimes added to prevent grain coarsening before and after forging.
  • titanium and niobium form carbonitrides with nitrogen and carbon in the steel, and are effective in enhancing the core hardness and the surface hardness as well.
  • an excessively high content of titanium increases carbide-based precipitates to deteriorate the toughness of the steel.
  • titanium is an expensive element.
  • the upper limit of titanium is 0.05% by weight.
  • the amount of titanium may be 0.01% or less by weight.
  • the total amount of titanium and niobium may be 0.01% or less by weight.
  • Sulphur (S) in small amounts may be beneficial in that it promotes machining
  • the amount of sulphur may be set to not more than 0.01% by weight. In some aspect, to avoid loss of ductility, the amount of sulphur may be 0.005% or less by weight.
  • Phosphorus (P) is an element present in the steel as an impurity. A small amount of phosphorus can cause deterioration in toughness or corrosion resistance of the steel. According to an aspect of the disclosure, the amount of phosphorus is 0.03% or less by weight. However it would be desirable that the amount of phosphorus is 0.01% or less.
  • the remainder of the low alloy steel composition is essentially iron except for nonessential or residual amounts of elements such as impurities which may be present in small amounts within commercially recognized allowable amounts.
  • FIG. 1 shows a table to compare exemplary alloy compositions according to the disclosure with conventional alloys, AISI 4140, AISI 4340, Nitralloy and '049 patent alloy.
  • conventional nitrided alloys which contain relatively large amounts of molybdenum and/or nickel, lower contents of alloy elements improve the tempering resistance and reduce sensitivity to temper embrittlement.
  • the higher the alloy contents of the nitriding steel the greater the surface hardness that can be achieved.
  • the compressive residual stress in the nitrided surface layer also increases, which leads to higher strength.
  • a low alloy steel according to the disclosure has lower contents of expensive elements compared to the conventional alloys but provide comparably high core hardness with good nitride characteristics.
  • Manufactured articles such as shafts, couplings and gears, having a composition according to the disclosure, may be advantageously initially formed to a desired shape by forging or rolling.
  • the formed articles may be hardened by heating to a temperature about 870° C. (1600° F.) for a period of about one hour and then quenched in either water or oil to complete phase transformation.
  • the formed articles may be quenched by high pressure gas quenching, which is typically coupled to vacuum heat treating processes. After tempering to precipitate and agglomerate the strengthening particles and thereby provide desired properties, the articles are then nitrided.
  • the amount of chromium and molybdenum carbides increases as well. This reduces the precipitation of nitrides and results in a lower increase in hardness.
  • the manufacturing processes can be reduced, and at the same time, by increasing the silicon content, desired core hardness and/or good response to nitriding are achieved as well.
  • Steels having compositions according to the disclosure may be supplied as pipes, hot-rolled plate, rolled round bars, forgings, round bars, square bars, flat bars, plates and the likes.
  • a low alloy steel according to the disclosure may be obtained by melting, forming and heat treating.
  • FIG. 2 is a schematic diagram of an exemplary manufacturing process 100 according to the disclosure.
  • a low alloy steel according to the disclosure is alloyed 110 .
  • a melted steel may be cast.
  • the steel is hot deformed by forging or hot-rolling 120 .
  • the steel may be initially heated to a temperature in a range of about 1100 to 1250° C.
  • the steel may then be hot forged into a desired shape, and control cooled from the forging temperature to achieve a desired microstructure.
  • the forged product may be air cooled using fans or other means of circulating the cooling air.
  • FIG. 3 is a schematic diagram of another exemplary manufacturing process 200 according to the disclosure.
  • the steel is hot deformed by forging or hot-rolling 220 and rough machined 230 .
  • the steel is quenched and tempered to specific core hardness 240 , and then finish machined to form a steel part 250 .
  • the steel part is rapidly nitrided 260 .
  • the steel part may be lapped or lightly ground as necessary 270 .
  • the exemplary manufacturing process 200 may provide the steel with maximum machinability.
  • Nitriding is a thermo-chemical process by which the surface of a steel part is enriched with nitrogen to form alloy nitrides which improve the wear resistance and form a surface nitride layer which can improve the corrosion resistance of the steel part.
  • nitriding increases surface hardness, wear resistance, resistance to certain types of corrosion, and compressive surface stresses, which improve the fatigue resistance of the steel part. Accordingly, nitrided steel articles are often used for gears, couplings, shafts, and other applications that require resistance to wear due to high stress loading and abrasive environments.
  • Nitriding a steel may be carried out in an atmosphere containing partially dissociated ammonia gas at a temperature in a range of 400 to 600° C.
  • the process from the commencement to the completion of nitriding usually takes 20-40+ hours.
  • nitriding time can be significantly reduced for articles having a steel composition according to the disclosure.
  • the nitriding time can be reduced on the order of 40% thereby effecting significant cost savings.
  • a time taken from the commencement of nitriding to the completion may be 15 hrs or less. Having reduced amounts of molybdenum, nickel and/or titanium and increased amounts of silicon, a steel composition according to the disclosure is suitable for rapid nitriding and provides the steel with desired core hardness.
  • Parts made of the steels according to the disclosure may be used for the production of internal combustion engines such as crankshafts, piston pins, cam timing gears, connecting rods and the likes. Additionally, a steel according to the disclosure may be used in a track pin and/or in a track pin joint assembly of a track chain that can be used as part of a tracked undercarriage of a track-type tractor, tracked loader, or any other tracked machine known in the art.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Heat Treatment Of Articles (AREA)
US14/933,467 2015-11-05 2015-11-05 Alloy with High Core Hardness Suitable for Rapid Nitriding Abandoned US20170130304A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US14/933,467 US20170130304A1 (en) 2015-11-05 2015-11-05 Alloy with High Core Hardness Suitable for Rapid Nitriding
US15/292,985 US10272960B2 (en) 2015-11-05 2016-10-13 Nitrided track pin for track chain assembly of machine
DE102016120608.3A DE102016120608A1 (de) 2015-11-05 2016-10-27 Legierung mit hoher Kernhärte, geeignet zum Schnell-Nitrieren

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US14/933,467 US20170130304A1 (en) 2015-11-05 2015-11-05 Alloy with High Core Hardness Suitable for Rapid Nitriding

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US15/292,985 Continuation-In-Part US10272960B2 (en) 2015-11-05 2016-10-13 Nitrided track pin for track chain assembly of machine

Publications (1)

Publication Number Publication Date
US20170130304A1 true US20170130304A1 (en) 2017-05-11

Family

ID=58585161

Family Applications (1)

Application Number Title Priority Date Filing Date
US14/933,467 Abandoned US20170130304A1 (en) 2015-11-05 2015-11-05 Alloy with High Core Hardness Suitable for Rapid Nitriding

Country Status (2)

Country Link
US (1) US20170130304A1 (de)
DE (1) DE102016120608A1 (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109790591A (zh) * 2016-10-13 2019-05-21 卡特彼勒公司 一种用于机器履带链组件的氮化履带销
CN109913737A (zh) * 2019-05-05 2019-06-21 宁波浩渤涂覆科技有限公司 高强度螺栓及其制备方法
WO2020157665A1 (en) * 2019-01-29 2020-08-06 Tata Steel Limited A high strength-high ductile steel and a method of manufacturing thereof
WO2022076159A1 (en) 2020-10-06 2022-04-14 Caterpillar Inc. Ferritic nitro-carburized track pin for track chain assembly of machine

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020009551A1 (en) * 1999-06-01 2002-01-24 Jong Ho Ko Process for heat treatment nitriding in the presence of titanium and products produced thereby
JP2011068979A (ja) * 2009-08-24 2011-04-07 Jfe Steel Corp 部分焼戻し軟化鋼板およびその鋼板を用いたプレス成形部品

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4853049A (en) 1984-02-13 1989-08-01 Caterpillar Inc. Nitriding grade alloy steel article

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020009551A1 (en) * 1999-06-01 2002-01-24 Jong Ho Ko Process for heat treatment nitriding in the presence of titanium and products produced thereby
JP2011068979A (ja) * 2009-08-24 2011-04-07 Jfe Steel Corp 部分焼戻し軟化鋼板およびその鋼板を用いたプレス成形部品

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
English Abstract and English Machine Translation of Kimura et al. (JP 2011-067979) (April, 7, 2011). *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109790591A (zh) * 2016-10-13 2019-05-21 卡特彼勒公司 一种用于机器履带链组件的氮化履带销
WO2020157665A1 (en) * 2019-01-29 2020-08-06 Tata Steel Limited A high strength-high ductile steel and a method of manufacturing thereof
CN109913737A (zh) * 2019-05-05 2019-06-21 宁波浩渤涂覆科技有限公司 高强度螺栓及其制备方法
WO2022076159A1 (en) 2020-10-06 2022-04-14 Caterpillar Inc. Ferritic nitro-carburized track pin for track chain assembly of machine

Also Published As

Publication number Publication date
DE102016120608A1 (de) 2017-05-11

Similar Documents

Publication Publication Date Title
US8961710B2 (en) Carburized component and manufacturing method
JP3995904B2 (ja) 加工性および強度に優れた等速ジョイント用内輪の製造方法
US20130186522A1 (en) Carburizing steel having excellent cold forgeability and method of manufacturing the same
US20140283954A1 (en) Bainitic microalloy steel with enhanced nitriding characteristics
CN105002507A (zh) 一种17CrNiMo6材料齿轮加工工艺方法
US20180223411A1 (en) Rapid Nitriding Through Nitriding Potential Control
US20170130304A1 (en) Alloy with High Core Hardness Suitable for Rapid Nitriding
JPH0892690A (ja) 耐疲労特性に優れた浸炭部品およびその製造方法
JPS6043431B2 (ja) 軽荷重用窒化機械部品の製造法
JP2018141218A (ja) 部品およびその製造方法
US20160047020A1 (en) A Bearing Steel Composition
JP2007146232A (ja) 鋼製軟窒化機械部品の製造方法
JP4737601B2 (ja) 高温窒化処理用鋼
JPS5916949A (ja) 軟窒化用鋼
JPH0565592A (ja) 高疲労強度構造用鋼およびその鋼部材
JP4536327B2 (ja) 短時間での浸炭性に優れたＮｂ含有肌焼鋼
JP4175933B2 (ja) 短時間の窒化処理で高い表面硬さと深い硬化深さの得られる窒化鋼部品及びその製造方法
JP5734050B2 (ja) 転動疲労特性、高周波焼入性に優れる中炭素鋼
JP7310723B2 (ja) 鋼部品およびその製造方法
JPH09227992A (ja) 軟窒化用構造用鋼
JP2002194492A (ja) 高硬度部品
JP2001081531A (ja) 耐へたり性と耐衝撃疲労性に優れた強靭窒化用鋼
JPH1060586A (ja) 浸炭窒化軸受用鋼
JPH01177338A (ja) 窒化用非調質鋼
JP2023163968A (ja) 棒鋼及び浸炭焼入れ部品

Legal Events

Date Code Title Description
AS Assignment

Owner name: CATERPILLAR INC., ILLINOIS

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BIRKY, ZACHARY S.;MEYER, ROBERT;BIERMAN, ROBERT;SIGNING DATES FROM 20151104 TO 20151105;REEL/FRAME:036970/0878

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION