US3661656A - Case-hardened steel product and process for its manufacture - Google Patents

Case-hardened steel product and process for its manufacture Download PDF

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US3661656A
US3661656A US829949A US3661656DA US3661656A US 3661656 A US3661656 A US 3661656A US 829949 A US829949 A US 829949A US 3661656D A US3661656D A US 3661656DA US 3661656 A US3661656 A US 3661656A
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steel
steel product
carburized
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Martin Holger Jarleborg
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Fagersta Bruks AB
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    • 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
    • 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
    • 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

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  • This invention is concerned with the use of an alloyed steel for the manufacture of case-hardened products or articles such as rods, bars, tubes, gear wheels, detachable rock drill bits and the like-which must have a hard, wear-resistant surface and a tough core portion.
  • the products are made of a manganese steel having a low content of carbon but having a surface of high carbon content producedby carburization.
  • the essential feature of the products or articles according to the invention consists in that they are made of a killed steel comprising, in addition to iron and ordinary impurities,
  • Nb being replaceable wholly or partially by Ta N up to 0.03 preferably 0.005-0.02 T Zr up to 0.2
  • the carburized surface layer has the same composition as the core portion.
  • the non-carburized steel has a very fine grain structure and extraordinarily good strength properties.
  • the yield point and strength may be made to vary within wide limits, according to needs.
  • the yield point will be within the range of from 60 to 100 kg/sq.mm.
  • the material is very tough, and its impact transition temperature is below -40 C even at maximum strength.
  • the steel is to contain 2.2-6.0 percent of manganese, preferably 2.5-5.0 percent. For some purposes a manganese content of 3.0-5.0 percent is preferred.
  • the silicon content of the steel is to be within the range of from 0.5 to 2.0 percent. With a Si content below the 0.5 percent limit, the carburization would proceed slowly or would be non-uniform.
  • the siliconcontent-which is preferably within the range of 0.7-1.5 percent is of importance for the carburization treatment because silicon increases the activity of carbon so that the product can thus be given a uniformly carburized surface layer within a relatively short time.
  • residual austenite which is normally obtained in carburizing operations, especially if the manganese content is high, will disappear when silicon is present within the ranges stated above.
  • the steel is to contain 0.0l-0.5 percent, preferably 0.02-0.2 percent of niobium (tantalum) and/or vanadium. Normally it should contain max. 0.3 percent niobium (tantalum) for reasons of solubility, and it should preferably not contain more than 0.3 percent vanadium, chiefly for reasons of economy.
  • the steel lends itself extremely well to shaping operations and can easily be subjected to cutting tool working operations.
  • the diagram of the accompanying drawing illustrates the machinability of a steel No. 2736 in a milling test, as compared to a conventional steel No. 2541 subjected to the same milling test.
  • Steel No. 2736 contains 0.032 C, 1.15 Si, 3.85 Mn, 0.070 AL, 0.13 Nb and 0.015 N and has been heat-treated to a yield point of 76 kg/sq.mm, a tensile strength of 93 kg/sq.mm and a Brinell hardness of 330.
  • 2541 contains about the following proportions ofC, Si, Mn, Cr, Ni and Mo: C 0.35 Si 0.25 Mn 0.7%; Cr 1.4 Ni 1.4 M 0.2 and this steel has been heat-treated to a Brinell hardness of 270.
  • the volume of cuttings in cubic centimeters (ordinate) is plotted against the cutting rate in meters per minute (abscissa), the milling having been performed with a high-speed steel (cutting depth 1 mm, feed 0.1 mm, criterion VB,,,,,, 0.7 mm).
  • Shaping of the steel may be effected in many different ways.
  • a blank may be produced by casting, rolling, forging etc.
  • the blank is then given the desired shape by machining or hot or cold pressing.
  • the object or body thus obtained is then subjected to surface carburization in those portions where surface hardness is desired. interior as well as exterior portions of the body configuration may be carburized.
  • the carburizing operation is carried out in some known per se manner such as for instance by powder-carburization, cyanide-carburization or gas-carburization.
  • the thickness of .the carburized surface layer may vary from 0.1 to about 2.5 mm according to the dimensions of the product. Normally carburizing depths near or at the lower end of this range are chosen for articles of small dimensions whereas carburizing depths in the vicinity of the upper end of said range are chosen for machine parts of large dimensions.
  • the carbon content in the carburized portion will amount to 0.5-1.5 percent, preferably 0.7-1.2 percent.
  • the treatment of the steel product was effected at 900 C for 6 hours, to give a carburized layer which had a thickness of 1 mm and a carbon content of about 0.9 percent.
  • hardening is effected immediately after the carburization and from a temperature slightly lower than that at which carburization was carried out.
  • the product may be allowed to cool after the carburization treatment, whereupon it is re-heated to the hardening-temperature and hardened.
  • the hardening may be effected in water, oil, air, salt bath or the like.
  • the treatment of the product usually comprises also a low-temperature tempering, as a final step. After completion of the heat treatment the product generally has a surface hardness of 55- 65 Re.
  • One example of a product or article according to this invention is a detachable bit for a rock drill.
  • a blank is shaped to the desired bit shape in the manner stated above, whereupon the surface layer is carburized on the interior and/or exterior faces.
  • hard metal pieces are soldered onto the bit, this step involving a heat treatment as required.
  • the bit is as a rule heated partially to a temperature of about l,000-1 ,200 C.
  • a convenient way of proceeding consists in first heating the entire bit to a lower temperature such as for instance 800-900 C and then continuing to heat the foremost portion of the bit body-where grooves, recesses or holes have been provided for the hard metal pieces-up to the soldering temperature. Other methods of heat treatment may also be employed.
  • a'product or article according to this invention is a gear-wheel which has been given its desired shape in the manner stated above.
  • the cogs are carburized in their surface portions, whereupon the gearwheel is heat-treated by hardening and tempering to a desired degree of hardness.
  • the starting material is a steel that lends itself very easily to allkinds of working operations, thus reducing the costs of operation to a minimum.
  • the product Due to its carburized surface, the product shows high resistance to wear, and high fatigue strength.
  • the core portion of the material retains its toughness also after the carburization has been effected.
  • the product Due to its hard surface layer and tough core, the product has a high degree of resistance to shocks and impacts, the material providing a shock absorbing effect.
  • the steel product according to claim 1 being of detachable rock drill bit having at least one carburized surface layer.
  • composition consists of C 0.01-0.03 i. Mn 2.5-5.0 5; Si 0l7-l.5 i; Al (acid-soluble) 0.0l-0.l is;

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

The product comprises a tough core and at least one hard, carburized surface layer, the core containing 0.01-0.04% C, 2.26.0% Mn, 0.5-2.0% Si, up to 0.2% acid-soluble Al, 0.01-0.5% Nb and/or V, with Nb being replaceable by Ta, up to 0.03% N, up to 0.2% Zr, the balance being iron and impurities, the surface layer having a higher carbon content than the core but otherwise the same composition. The product is manufactured by shaping a blank of the aforesaid core composition, the shaping operation being followed by surface carburization and hardening.

Description

O Unlted States Patent 1151 3,661,656 Jarleborg 1 1 May 9, 1972 [54] CASE-HARDENED STEEL PRODUCT [56] References Cited AND PROCESS FOR ITS UNITED STATES PATENTS MANUFACTURE 1,990,647 2/1935 Harris.... ..148/31.5 [721 Invent Jarlebmg, Hedkamvagen 2 219 780 10/1940 Jominy ..14s/3 1.5
Sweden [73] Assignee: Fagersta Bruks Aktiebolag, Fagersta, U' Examiner-Richard Dean Sweden Att0rneyH0lman & Stem [22] Filed: June 3, 1969 57 ABSTRACT [21] PP N 829,949 The product comprises a tough core and at least one hard, carburized surface layer, the core containing OBI-0.04% C, Foreign Appncation priority Data 2.2-6.070 Mn, (LS-2.0% Si, up KC? 0.2% acid-soluble A1, 0.010.5% Nb and/or V, w1th Nb bemg replaceable by Ta, up June 14, 1968 Sweden ..8093/68 to 003% N, up to 02% Zr, the balance being iron and imPurities, the surface layer having a higher carbon content than the 52 us. (:1 ..148/12.1, 148 124, 148/165, core but otherwise the same composition, The product is 148/19, 148/315, 148/36, 148/39, 148/144 manufactured by shaping a blank of the aforesaid core com- [51] Int. Cl. ..C21d 1/78 position, the Shaping operation being f ll d by Surface 58 Field of Search ..148/16.5, 19, 134, 137, 143, b i ti and hardening m/mi/ CASE-HARDENED STEEL PRODUCT AND PROCESS FOR ITS MANUFACTURE This invention is concerned with the use of an alloyed steel for the manufacture of case-hardened products or articlessuch as rods, bars, tubes, gear wheels, detachable rock drill bits and the like-which must have a hard, wear-resistant surface and a tough core portion. The products are made of a manganese steel having a low content of carbon but having a surface of high carbon content producedby carburization. The essential feature of the products or articles according to the invention consists in that they are made of a killed steel comprising, in addition to iron and ordinary impurities,
C 0.0l-0.04 preferably 0.01- .03 Mn 2.2-6.0 preferably 2.5-5.0 Si 0.5-2.0 preferably 0.7-1.5 a1. (acid-soluble) up to 0.2 preferably 0.0l-0.1 Nb and/or V 0.0l-0.5 preferably 0.02-0.2
but Nb being replaceable wholly or partially by Ta N up to 0.03 preferably 0.005-0.02 T Zr up to 0.2
and having a hard surface which is rich in carbon and is obtained in that the products or articles after having been shaped are subjected wholly or partially to carburization of'their surface portion, followed by hardening. Thus, except for its carbon content, the carburized surface layer has the same composition as the core portion.
The non-carburized steel has a very fine grain structure and extraordinarily good strength properties. By variation of the manganese content of the steelthe yield point and strength may be made to vary within wide limits, according to needs. The yield point will be within the range of from 60 to 100 kg/sq.mm. The material is very tough, and its impact transition temperature is below -40 C even at maximum strength. As stated above, the steel is to contain 2.2-6.0 percent of manganese, preferably 2.5-5.0 percent. For some purposes a manganese content of 3.0-5.0 percent is preferred.
The silicon content of the steel is to be within the range of from 0.5 to 2.0 percent. With a Si content below the 0.5 percent limit, the carburization would proceed slowly or would be non-uniform. The siliconcontent-which is preferably within the range of 0.7-1.5 percent is of importance for the carburization treatment because silicon increases the activity of carbon so that the product can thus be given a uniformly carburized surface layer within a relatively short time. Moreover, residual austenite which is normally obtained in carburizing operations, especially if the manganese content is high, will disappear when silicon is present within the ranges stated above.
Furthermore the steel is to contain 0.0l-0.5 percent, preferably 0.02-0.2 percent of niobium (tantalum) and/or vanadium. Normally it should contain max. 0.3 percent niobium (tantalum) for reasons of solubility, and it should preferably not contain more than 0.3 percent vanadium, chiefly for reasons of economy.
The steel lends itself extremely well to shaping operations and can easily be subjected to cutting tool working operations. The diagram of the accompanying drawing illustrates the machinability of a steel No. 2736 in a milling test, as compared to a conventional steel No. 2541 subjected to the same milling test. Steel No. 2736 contains 0.032 C, 1.15 Si, 3.85 Mn, 0.070 AL, 0.13 Nb and 0.015 N and has been heat-treated to a yield point of 76 kg/sq.mm, a tensile strength of 93 kg/sq.mm and a Brinell hardness of 330. The conventional steel No. 2541 contains about the following proportions ofC, Si, Mn, Cr, Ni and Mo: C 0.35 Si 0.25 Mn 0.7%; Cr 1.4 Ni 1.4 M 0.2 and this steel has been heat-treated to a Brinell hardness of 270. lnthe diagram, the volume of cuttings in cubic centimeters (ordinate) is plotted against the cutting rate in meters per minute (abscissa), the milling having been performed with a high-speed steel (cutting depth 1 mm, feed 0.1 mm, criterion VB,,,,, 0.7 mm).
Shaping of the steel may be effected in many different ways. A blank may be produced by casting, rolling, forging etc. The blank is then given the desired shape by machining or hot or cold pressing.
The object or body thus obtained is then subjected to surface carburization in those portions where surface hardness is desired. interior as well as exterior portions of the body configuration may be carburized. The carburizing operation is carried out in some known per se manner such as for instance by powder-carburization, cyanide-carburization or gas-carburization. The thickness of .the carburized surface layer may vary from 0.1 to about 2.5 mm according to the dimensions of the product. Normally carburizing depths near or at the lower end of this range are chosen for articles of small dimensions whereas carburizing depths in the vicinity of the upper end of said range are chosen for machine parts of large dimensions.
The carbon content in the carburized portion will amount to 0.5-1.5 percent, preferably 0.7-1.2 percent. By way of example, it may be mentioned that in one case the treatment of the steel product was effected at 900 C for 6 hours, to give a carburized layer which had a thickness of 1 mm and a carbon content of about 0.9 percent.
In the simplest case, hardening is effected immediately after the carburization and from a temperature slightly lower than that at which carburization was carried out. Alternatively, the product may be allowed to cool after the carburization treatment, whereupon it is re-heated to the hardening-temperature and hardened. The hardening may be effected in water, oil, air, salt bath or the like. The treatment of the product usually comprises also a low-temperature tempering, as a final step. After completion of the heat treatment the product generally has a surface hardness of 55- 65 Re.
One example of a product or article according to this invention is a detachable bit for a rock drill. When such a bit is to be manufactured, a blank is shaped to the desired bit shape in the manner stated above, whereupon the surface layer is carburized on the interior and/or exterior faces. Then, hard metal pieces are soldered onto the bit, this step involving a heat treatment as required. In a hard soldering operation, the bit is as a rule heated partially to a temperature of about l,000-1 ,200 C. Also, a convenient way of proceeding consists in first heating the entire bit to a lower temperature such as for instance 800-900 C and then continuing to heat the foremost portion of the bit body-where grooves, recesses or holes have been provided for the hard metal pieces-up to the soldering temperature. Other methods of heat treatment may also be employed.
Another example of a'product or article according to this invention is a gear-wheel which has been given its desired shape in the manner stated above. When the wheel body has been subjected to a machining or other finishing operation the cogs are carburized in their surface portions, whereupon the gearwheel is heat-treated by hardening and tempering to a desired degree of hardness.
The products or articles of this invention have great advantages as regards their properties and the ease with which they can be manufactured on an industrial scale. In particular, the following points should be noted:
1. The starting material is a steel that lends itself very easily to allkinds of working operations, thus reducing the costs of operation to a minimum.
2. Due to its carburized surface, the product shows high resistance to wear, and high fatigue strength.
3. The core portion of the material retains its toughness also after the carburization has been effected.
4. Due to its hard surface layer and tough core, the product has a high degree of resistance to shocks and impacts, the material providing a shock absorbing effect.
5. Due to the toughness of the starting material, the extent to which heat treatments (such as performed in soldering operations) will cause changes in the dimensions of the product is minimized; this in turn results in a more favorable stress distribution in the soldering joint.
consisting of:
0.0l-0.04 1b, Mn 2.2-6.0 96; Si 0.5-2.0 '5; Al (acid-soluble) up to 0.2
at least one element selected from the group v consisting of Nb or V in an amount of from and Nb being replaceable wholly or partially by T N up to 0.03 56; and Zr up to 0.2 k;
the balance being iron and ordinary impurities; and at least one hard, carburized surface layer having a higher'carbon content than said core but having otherwise, except for said surface layer carbon content, the same composition as said core. 2. The steel product according to claim 1 being of detachable rock drill bit having at least one carburized surface layer.
3. The steel product according 'to claim 1 being a gearwheel having cogs wherein the surface layers are carburized.
4. A process for producing a case-hardened steel product made of a killed, manganese-alloyed steel blank consisting of:
C 0.01-0.04 Mn 2.2-6.0 Si 0.5-2.0 Al (acid-soluble) up to 0.2 Kw;
at least ,one element selected from the group consisting of Nb or V in an amount of from the balance being iron and ordinary impurities;
comprising shaping the steel blank to the desired configuration of the product; carburizing at least one of the surface layers of the shaped steel blank; and then hardening to form the desired steel product. i
5. The process according to claim 4 wherein said hardening is followed by-a tempering step.
6. The process according to claim 4 wherein said shaping step is a machining operation.
7. The process according to claim 4 wherein said shaping step is a pressing operation.
8. The steel product according to claim 1 wherein the composition consists of C 0.01-0.03 i. Mn 2.5-5.0 5; Si 0l7-l.5 i; Al (acid-soluble) 0.0l-0.l is;
at least one element selected from the group consisting of Nb or V in an amount of from'0.02-0.2 and Nb being wholly or partially replaceable by Ta;
N 0.005-002 and Zr up to 0.2 the balance being iron and ordinary impuri- C 0.01-0.03 Mn 2.5-5.0 9%; Si 0.7-1.5 Al (acid-soluble) 0.0l0.l
at least one element selected from the group consisting of Nb or V in an amount of from 0.02-0.2 and Nb being wholly or partially replaceable by Ta;
N 0.005-0.02 and Zr up to 0.2 the balance being iron and ordinary impurities. 12. The process according to claim 11 wherein said hardening is followed by a tempering step.
* l l l

Claims (11)

  1. 2. The steel product according to claim 1 being of detachable rock drill bit having at least one carburized surface layer.
  2. 3. The steel product according to claim 1 being a gear-wheel having cogs wherein the surface layers are carburized.
  3. 4. A process for producing a case-hardened steel product made of a killed, manganese-alloyed steel blank consisting of: C 0.01-0.04 %; Mn 2.2-6.0 %; Si 0.5-2.0 %; Al (acid-soluble) up to 0.2 %; at least one element selected from the group consisting of Nb or V in an amount of from 0.01-0.5 %; and Nb being replaceable wholly or partially by Ta; N up to 0.03 %; and Zr up to 0.2 %; the balance being iron and ordinary impurities; comprising shaping the steel blank to the desired configuration of the product; carburizing at least onE of the surface layers of the shaped steel blank; and then hardening to form the desired steel product.
  4. 5. The process according to claim 4 wherein said hardening is followed by a tempering step.
  5. 6. The process according to claim 4 wherein said shaping step is a machining operation.
  6. 7. The process according to claim 4 wherein said shaping step is a pressing operation.
  7. 8. The steel product according to claim 1 wherein the composition consists of C 0.01-0.03 %; Mn 2.5-5.0 %; Si 0.7-1.5 %; A1 (acid-soluble) 0.01-0.1 %; at least one element selected from the group consisting of Nb or V in an amount of from 0.02-0.2 % and Nb being wholly or partially replaceable by Ta; N 0.005-0.02 %; and Zr up to 0.2 %; the balance being iron and ordinary impurities.
  8. 9. The steel product according to claim 8 being a detachable rock drill bit having at least one carburized surface layer.
  9. 10. The steel product according to claim 8 being a gear-wheel having cogs wherein the surface layers are carburized.
  10. 11. The process according to claim 4 wherein the composition consists of: C 0.01-0.03 %; Mn 2.5-5.0 %; Si 0.7-1.5 %; A1 (acid-soluble) 0.01-0.1 %; at least one element selected from the group consisting of Nb or V in an amount of from 0.02-0.2 % and Nb being wholly or partially replaceable by Ta; N 0.005-0.02 %; and Zr up to 0.2 %; the balance being iron and ordinary impurities.
  11. 12. The process according to claim 11 wherein said hardening is followed by a tempering step.
US829949A 1968-06-14 1969-06-03 Case-hardened steel product and process for its manufacture Expired - Lifetime US3661656A (en)

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3914135A (en) * 1972-03-15 1975-10-21 Nippon Kokan Kk Method of improving steel properties by using controlled cooling rates
US4042273A (en) * 1975-05-20 1977-08-16 Fried. Krupp Huttenwerke Ag Rail wheel
US4131491A (en) * 1977-12-22 1978-12-26 Fmc Corporation Torsion bar and method of forming the same
US4204437A (en) * 1978-04-03 1980-05-27 Smith International, Inc. Friction bearing rock bit and segment, and method for making them
US4249621A (en) * 1979-03-22 1981-02-10 Smith International, Inc. Friction bearing rock bit and segment
US4261769A (en) * 1978-09-26 1981-04-14 Usui Kokusai Sangyo Kabushiki Kaisha High pressure fuel injection tubing material
US4415378A (en) * 1982-04-22 1983-11-15 Dana Corporation Case hardening method for steel parts
US4773947A (en) * 1983-08-02 1988-09-27 Nissan Motor Co., Ltd. Manufacturing process for high temperature carburized case harden steel
US4819471A (en) * 1986-10-31 1989-04-11 Westinghouse Electric Corp. Pilger die for tubing production
US5653822A (en) * 1995-07-05 1997-08-05 Ford Motor Company Coating method of gas carburizing highly alloyed steels
US5729822A (en) * 1996-05-24 1998-03-17 Stackpole Limited Gears
US6375762B1 (en) * 1995-06-30 2002-04-23 Carl Aug. Picard Gmbh & Co. Kg Base material for producing blades for circular saws, cutting-off wheels, mill saws as well as cutting and scraping devices
US20060201718A1 (en) * 2003-01-31 2006-09-14 Smith International, Inc. High-strength/high toughness alloy steel drill bit blank

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1990647A (en) * 1932-06-27 1935-02-12 Smith Corp A O Copper-containing steel
US2219780A (en) * 1938-01-06 1940-10-29 Gen Motors Corp Alloy steel

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR768468A (en) * 1933-02-11 1934-08-07 & Commerciale Des Aciers Soc I High manganese steel construction components, and process for their manufacture

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1990647A (en) * 1932-06-27 1935-02-12 Smith Corp A O Copper-containing steel
US2219780A (en) * 1938-01-06 1940-10-29 Gen Motors Corp Alloy steel

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3914135A (en) * 1972-03-15 1975-10-21 Nippon Kokan Kk Method of improving steel properties by using controlled cooling rates
US4042273A (en) * 1975-05-20 1977-08-16 Fried. Krupp Huttenwerke Ag Rail wheel
US4131491A (en) * 1977-12-22 1978-12-26 Fmc Corporation Torsion bar and method of forming the same
US4204437A (en) * 1978-04-03 1980-05-27 Smith International, Inc. Friction bearing rock bit and segment, and method for making them
US4261769A (en) * 1978-09-26 1981-04-14 Usui Kokusai Sangyo Kabushiki Kaisha High pressure fuel injection tubing material
US4249621A (en) * 1979-03-22 1981-02-10 Smith International, Inc. Friction bearing rock bit and segment
US4415378A (en) * 1982-04-22 1983-11-15 Dana Corporation Case hardening method for steel parts
US4773947A (en) * 1983-08-02 1988-09-27 Nissan Motor Co., Ltd. Manufacturing process for high temperature carburized case harden steel
US4819471A (en) * 1986-10-31 1989-04-11 Westinghouse Electric Corp. Pilger die for tubing production
US6375762B1 (en) * 1995-06-30 2002-04-23 Carl Aug. Picard Gmbh & Co. Kg Base material for producing blades for circular saws, cutting-off wheels, mill saws as well as cutting and scraping devices
US5653822A (en) * 1995-07-05 1997-08-05 Ford Motor Company Coating method of gas carburizing highly alloyed steels
US5729822A (en) * 1996-05-24 1998-03-17 Stackpole Limited Gears
US20060201718A1 (en) * 2003-01-31 2006-09-14 Smith International, Inc. High-strength/high toughness alloy steel drill bit blank
US7395884B2 (en) * 2003-01-31 2008-07-08 Smith International, Inc. High-strength/high toughness alloy steel drill bit blank

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FI50144B (en) 1975-09-01
FR2010925A1 (en) 1970-02-20
DE1929289B1 (en) 1970-10-22
AT297075B (en) 1972-03-10
FI50144C (en) 1975-12-10
GB1207643A (en) 1970-10-07
NL6908991A (en) 1969-12-16
SE334750B (en) 1971-05-03
NO125000B (en) 1972-07-03

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