US20080190522A1 - Process for Heat Treatment of Steel or Cast Iron Workpieces - Google Patents

Process for Heat Treatment of Steel or Cast Iron Workpieces Download PDF

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Publication number
US20080190522A1
US20080190522A1 US11/659,543 US65954305A US2008190522A1 US 20080190522 A1 US20080190522 A1 US 20080190522A1 US 65954305 A US65954305 A US 65954305A US 2008190522 A1 US2008190522 A1 US 2008190522A1
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United States
Prior art keywords
temperature
workpiece
transformation
bainite
austenite
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
US11/659,543
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English (en)
Inventor
Johann Volkmuth
Martin Goebel
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SKF AB
Original Assignee
SKF AB
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Filing date
Publication date
Application filed by SKF AB filed Critical SKF AB
Assigned to AB SKF reassignment AB SKF ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: GOEBEL, MARTIN, VOLKMUTH, JOHANN
Publication of US20080190522A1 publication Critical patent/US20080190522A1/en
Abandoned legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/84—Controlled slow cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/30—Parts of ball or roller bearings
    • F16C33/58—Raceways; Race rings
    • F16C33/64—Special methods of manufacture
    • 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

Definitions

  • the invention relates to a process for heat treatment of steel or cast iron workpieces.
  • One current heat treatment process which, for purposes of meeting the aforementioned and/or other quality requirements in a manner as good as possible is diversely combined with other heat treatment measures, is bainite hardening.
  • the workpieces are heated to the austenitizing temperature and kept at this temperature for a time. Then quenching to a temperature barely above the martensite start temperature takes place. Afterwards the workpieces are kept constantly at this temperature until the end of transformation and finally cooled to room temperature.
  • EP 0 896 068 B1 furthermore discloses increasing the temperature of the workpieces before the end of transformation of the austenite into bainite in order to accelerate the conversion of the residual austenite.
  • the object of the invention is to make the heat treatment of the steel or cast iron workpieces such that high quality requirements can be achieved at reasonable cost and thus a long service life of the workpieces is enabled.
  • hardness as high as possible and/or a holding time as short as possible will be sufficient for bainite hardening.
  • the workpieces are quenched, after a holding interval at or above the austenitizing temperature, to a temperature above the martensite start temperature, martensite being formed when going below this temperature.
  • the austenite is transformed into bainite.
  • the temperature of the workpieces is lowered during the time interval of transformation and transformation of austenite into bainite is continued.
  • the invention has the advantage that a hardness higher than for isothermal bainite hardening can be achieved. This lengthens the service life of the workpieces which have been treated in this way.
  • the temperature of the workpieces is lowered to values below the temperature which is achieved by quenching at least during a time portion of 20% of the transformation duration.
  • the temperature of the workpieces is lowered preferably depending on the martensite start temperature.
  • the temperature of the workpieces is lowered to values above the martensite start temperature in order to avoid martensite formation. In this way the formation of mixed structures in the workpieces can be avoided.
  • the temperature of the workpieces is lowered according to a given temperature profile.
  • optimum and reproducible results can be achieved.
  • the temperature of the workpieces can be lowered incrementally.
  • This version can be implemented with relatively little cost.
  • One possible implementation consists in exposing the workpieces to media of varied temperature to lower the workpiece temperature, especially to place them in baths kept at varied temperatures.
  • the temperature of the workpieces is continuously lowered.
  • the temperature of the workpieces is lowered according to the behavior of the martensite start temperature.
  • the temperature of the workpieces can be lowered by means of one or more controllable facilities, especially furnaces. Thus almost any temperature profiles can be implemented.
  • the workpieces are heated to a higher temperature after partial transformation of austenite into bainite in order to accelerate transformation.
  • This is a very efficient measure for shortening the time required overall for heat treatment of the workpieces.
  • the time interval of transformation can be dimensioned such that complete transformation of austenite into bainite does not take place and the workpieces are cooled to room temperature following the transformation time interval, held briefly there, and then age-hardened.
  • the heat treatment process as claimed in the invention can be used especially for workpieces which are made from a through-hardening rolling bearing or heat treatable steel.
  • workpieces are rolling bearing components.
  • FIGS. 1 to 5 show schematic time-temperature diagrams to illustrate the different versions of the heat treatment process disclosed herein.
  • the X axis plots the time on a logarithmic scale.
  • the Y axis plots the workpiece temperature.
  • the heat treatment process disclosed herein is carried out with steel or cast iron workpieces.
  • workpieces of through-hardening rolling bearing or heat treatable steels are suitable.
  • One typical representative of a rolling bearing steel which is defined in standard DIN EN ISO 683-17 is a steel labelled 100Cr6. This steel, relative to its mass, contains 0.93 to 1.05% carbon, 1.35 to 1.60% chromium, 0.25 to 0.45% manganese, 0.15 to 0.35% silicon and up to 0.1% molybdenum.
  • the phosphorus content is a maximum 0.025%, and the sulfur content is a maximum 0.015%.
  • small amounts of other elements can be contained, depending on production.
  • the workpieces are subjected to soft machining, by which the workpieces are brought into the desired form and, for example, are made as rolling bearing components.
  • This form can differ from the final form of the workpieces by additions for further mechanical working after heat treatment.
  • FIG. 1 shows a schematic time-temperature diagram for illustration of a first version of the heat treatment process as disclosed herein.
  • the workpieces are first heated proceeding from room temperature to the austenitizing temperature and kept at this temperature for a time. After austenitizing, the workpieces are quenched and thus cooled to a temperature barely above the martensite start temperature. Martensite formation is not desirable within the framework of the heat treatment process, so that falling below the martensite start temperature is avoided as long as this can be combined with the intended process progression. Quenching can advantageously take place by immersion of the workpieces in a salt bath. Salt baths have the advantage that they can easily capture the energy being released by exothermal reactions. In this way the material temperature can be kept within very narrow limits.
  • bainite transformation After quenching, gradual conversion of the austenites into bainite takes place. This conversion is also called bainite transformation, bainite hardening or austempering. As is indicated by the broken line, bainite transformation according to the prior art is carried out at a constant temperature.
  • the workpiece temperature is lowered during bainite transformation. This is enabled in that the martensite starting structure which should always be at least maintained likewise decreases during bainite transformation.
  • a hardness of roughly 59 to 64 HRC can be achieved which is greater than is the case for conventional isothermal bainite transformation.
  • the workpiece temperature preferably during at least a time portion of 20% of the transformation interval intended for bainite transformation is lowered to values which are below the workpiece temperature achieved by quenching. Especially good results can be achieved for a time portion of at least 80% of the transformation interval.
  • the temperature is lowered incrementally. This means that the workpiece temperature is kept for a time at a constant temperature and then quickly lowered to barely above the current value of the martensite start temperature. Then a constant segment and a renewed drop etc. follow.
  • This behavior of the workpiece temperature can be achieved, for example, by several salt baths which are kept at different temperatures and into which the workpieces are placed in succession.
  • the versions of the heat treatment process described below differ from the above described first version with respect to the behavior of the workpiece temperature during bainite transformation, and in the case of the version shown in FIG. 5 also after bainite transformation. Otherwise what was said about the first version applies to the other versions analogously.
  • FIG. 2 shows a schematic time-temperature diagram for illustration of a second version of the heat treatment process disclosed herein.
  • this second version during bainite transformation immediately after quenching of the workpieces, there is a holding phase with a constant workpiece temperature which is followed by a phase with a continuously decreasing workpiece temperature. Finally, a holding phase with a constant workpiece temperature follows. Outside the time interval intended for bainite transformation, the behavior of the workpiece temperature corresponds to the behavior described for the first version.
  • the workpieces are in turn quenched again in a salt bath and left for a time in the salt bath. Then the workpieces are each moved for a time into media kept at different temperatures, for example tempering furnaces or salt baths which are controlled such that the workpiece temperature is lowered or kept in the desired manner.
  • media kept at different temperatures for example tempering furnaces or salt baths which are controlled such that the workpiece temperature is lowered or kept in the desired manner.
  • FIG. 3 shows a schematic time-temperature diagram for illustration of a third version of the heat treatment process disclosed herein.
  • the workpiece temperature during the bainite transformation is continuously lowered following a short holding phase after the quenching process. Temperature lowering takes place in a manner corresponding to the decrease in the martensite start temperature.
  • the workpiece temperature during the time interval intended for bainite transformation this yields a behavior essentially parallel to the martensite start temperature.
  • the workpieces after quenching can be placed in a long tempering furnace or temperature-controlled furnace in which the desired temperature profile can be established and controlled.
  • FIG. 4 shows a schematic time-temperature diagram to illustrate one development of the third version of the heat treatment process.
  • the workpiece temperature during bainite transformation is first lowered in a manner analogous to FIG. 3 .
  • the workpiece temperature is distinctly raised and kept constant for a time.
  • the temperature value reached thereby is preferably higher than the workpiece temperature at the start of bainite transformation.
  • the workpiece temperature is lowered to room temperature.
  • the first and the second version of the heat treatment process disclosed herein can also be developed accordingly.
  • FIG. 5 shows a schematic time-temperature diagram to illustrate one development of a second version of the heat treatment process as disclosed herein.
  • the workpiece temperature is lowered to room temperature after the first holding phase and the first lowering phase which are carried out in the second version during the time interval intended for bainite transformation.
  • a short holding time at room temperature is followed by short-time or standard age-hardening.
  • the workpieces are preferably heated to a temperature which is between the workpiece temperature at the start of bainite transformation and the workpiece temperature immediately before interruption of the bainite transformation and is then cooled again to room temperature.
  • the time required overall for heat treatment is shortened compared to the second version of the heat treatment process as disclosed and shown in FIG. 2 .
  • martensite occurs as a structural component.
  • FIG. 5 The development shown in FIG. 5 can be transferred analogously to the first and third version of the heat treatment process as disclosed.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Articles (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
US11/659,543 2004-08-06 2005-07-30 Process for Heat Treatment of Steel or Cast Iron Workpieces Abandoned US20080190522A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE102004038159A DE102004038159B3 (de) 2004-08-06 2004-08-06 Verfahren zur Wärmebehandlung von Werkstücken aus Stahl oder Gusseisen
DE102004038159.3 2004-08-06
PCT/EP2005/008291 WO2006015749A1 (de) 2004-08-06 2005-07-30 Verfahren zur wärmebehandlung von werkstücken aus stahl oder gusseisen

Publications (1)

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US20080190522A1 true US20080190522A1 (en) 2008-08-14

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US11/659,543 Abandoned US20080190522A1 (en) 2004-08-06 2005-07-30 Process for Heat Treatment of Steel or Cast Iron Workpieces

Country Status (6)

Country Link
US (1) US20080190522A1 (enExample)
EP (1) EP1786935B1 (enExample)
JP (1) JP5622138B2 (enExample)
AT (1) ATE533865T1 (enExample)
DE (1) DE102004038159B3 (enExample)
WO (1) WO2006015749A1 (enExample)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090314396A1 (en) * 2008-06-18 2009-12-24 Philip Nash Method for efficient heat treatment of steel
WO2012161635A1 (en) * 2011-05-25 2012-11-29 Aktiebolaget Skf Method for heat treating a steel component
US20160348204A1 (en) * 2015-05-25 2016-12-01 Aktiebolaget Skf Method for improving the structure of a steel component after heating and stell component obtained by the method

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006059050A1 (de) * 2006-12-14 2008-06-19 Schaeffler Kg Verfahren zur Wärmebehandlung von Wälzlagerbauteilen aus durchgehärtetem, bainitischem Wälzlagerstahl
DE102012202902A1 (de) * 2012-02-27 2013-08-29 Aktiebolaget Skf Verfahren zur Herstellung einer Elektromotoranordnung und Elektromotoranordnung eines Elektrofahrzeugs
DE102016223680A1 (de) * 2016-11-29 2018-05-30 Schaeffler Technologies AG & Co. KG Verfahren zur Herstellung eines Wälzlagerbauteils
DE102018212009A1 (de) * 2018-07-18 2020-01-23 Volkswagen Aktiengesellschaft Hochfestes Lenkritzel

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1924099A (en) * 1931-11-20 1933-08-29 United States Steel Corp Thermally hardening steel
US2779698A (en) * 1955-11-04 1957-01-29 United States Steel Corp Method of improving machinability of steel
US6149743A (en) * 1997-08-01 2000-11-21 Ovako Steel Ab Method of complete bainite hardening
US6203634B1 (en) * 1998-10-28 2001-03-20 Skf Gmbh Method for heat-treating steel or cast iron components
US6387195B1 (en) * 2000-11-03 2002-05-14 Brush Wellman, Inc. Rapid quench of large selection precipitation hardenable alloys
US6843867B1 (en) * 1999-12-31 2005-01-18 Robert Bosch Gmbh Method of austempering steel parts

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DE1433715A1 (de) * 1964-01-17 1968-12-12 Breitenbach Gmbh Ed Verfahren zur Waermebehandlung von schweren Werkstuecken aus Schmiede- oder Gussstahl
DE2501175C3 (de) * 1975-01-14 1982-02-11 Bochumer Eisenhütte Heintzmann GmbH & Co, 4630 Bochum Vorrichtung zur Wärmebehandlung von Profilstahlabschnitten für den untertägigen Streckenausbau
JPS6052515A (ja) * 1983-09-01 1985-03-25 Hitachi Metals Ltd 強靭ねずみ鋳鉄の製造法
JPS6052511A (ja) * 1983-09-01 1985-03-25 Hitachi Metals Ltd バ−ミキユラ黒鉛鋳鉄の製造法
JPS60221525A (ja) * 1984-04-18 1985-11-06 Kubota Ltd 高強度ダクタイル鋳鉄管の製造法
JPS61149428A (ja) * 1984-12-24 1986-07-08 Hitachi Metals Ltd 球状黒鉛鋳鉄
JPS61217529A (ja) * 1985-03-22 1986-09-27 Nippon Steel Corp 延性のすぐれた高強度鋼板の製造方法
JPS62182224A (ja) * 1986-02-05 1987-08-10 Nippon Steel Corp 延性の良好な高強度鋼板の製造方法
JPH02277715A (ja) * 1989-04-19 1990-11-14 Aisin Takaoka Ltd 片状黒鉛鋳鉄の熱処理法
DE19911287C1 (de) * 1999-03-13 2000-08-31 Thyssenkrupp Stahl Ag Verfahren zum Erzeugen eines Warmbandes
DE10048234A1 (de) * 2000-09-29 2001-10-11 Daimler Chrysler Ag Verfahren zur Herstellung eines Nockens

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1924099A (en) * 1931-11-20 1933-08-29 United States Steel Corp Thermally hardening steel
US2779698A (en) * 1955-11-04 1957-01-29 United States Steel Corp Method of improving machinability of steel
US6149743A (en) * 1997-08-01 2000-11-21 Ovako Steel Ab Method of complete bainite hardening
US6203634B1 (en) * 1998-10-28 2001-03-20 Skf Gmbh Method for heat-treating steel or cast iron components
US6843867B1 (en) * 1999-12-31 2005-01-18 Robert Bosch Gmbh Method of austempering steel parts
US6387195B1 (en) * 2000-11-03 2002-05-14 Brush Wellman, Inc. Rapid quench of large selection precipitation hardenable alloys

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090314396A1 (en) * 2008-06-18 2009-12-24 Philip Nash Method for efficient heat treatment of steel
US8066828B2 (en) * 2008-06-18 2011-11-29 Tata Consultancy Services, Ltd. Method for efficient heat treatment of steel
WO2012161635A1 (en) * 2011-05-25 2012-11-29 Aktiebolaget Skf Method for heat treating a steel component
US20140209214A1 (en) * 2011-05-25 2014-07-31 Aktiebolaget Skf Method and steel component
EP2714944A4 (en) * 2011-05-25 2015-11-04 Skf Ab Method for heat treating a steel component
US10202678B2 (en) * 2011-05-25 2019-02-12 Aktiebolaget Skf Method and steel component
EP3604562A1 (en) * 2011-05-25 2020-02-05 Aktiebolaget SKF Method and steel component
US20160348204A1 (en) * 2015-05-25 2016-12-01 Aktiebolaget Skf Method for improving the structure of a steel component after heating and stell component obtained by the method

Also Published As

Publication number Publication date
ATE533865T1 (de) 2011-12-15
EP1786935B1 (de) 2011-11-16
EP1786935A1 (de) 2007-05-23
JP2008509280A (ja) 2008-03-27
JP5622138B2 (ja) 2014-11-12
WO2006015749A1 (de) 2006-02-16
DE102004038159B3 (de) 2006-05-18

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AS Assignment

Owner name: AB SKF, SWEDEN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:VOLKMUTH, JOHANN;GOEBEL, MARTIN;REEL/FRAME:020148/0556

Effective date: 20070222

STCB Information on status: application discontinuation

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