WO2013060866A1 - Composant porteur - Google Patents

Composant porteur Download PDF

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Publication number
WO2013060866A1
WO2013060866A1 PCT/EP2012/071293 EP2012071293W WO2013060866A1 WO 2013060866 A1 WO2013060866 A1 WO 2013060866A1 EP 2012071293 W EP2012071293 W EP 2012071293W WO 2013060866 A1 WO2013060866 A1 WO 2013060866A1
Authority
WO
WIPO (PCT)
Prior art keywords
bearing component
vanadium
bainite
still
steel
Prior art date
Application number
PCT/EP2012/071293
Other languages
English (en)
Inventor
Mohamed Sherif
John Beswick
Original Assignee
Aktiebolaget Skf
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 Aktiebolaget Skf filed Critical Aktiebolaget Skf
Publication of WO2013060866A1 publication Critical patent/WO2013060866A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/40—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races
    • 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
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
    • 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
    • F16C33/62—Selection of substances
    • 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
    • C21D2211/004—Dispersions; Precipitations
    • 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
    • F16C2204/00—Metallic materials; Alloys
    • F16C2204/60—Ferrous alloys, e.g. steel alloys
    • F16C2204/66—High carbon steel, i.e. carbon content above 0.8 wt%, e.g. through-hardenable steel

Definitions

  • the present invention relates generally to the field of metallurgy and to a bearing component such as a rolling element or ring formed from a bearing steel.
  • the bearing steel has a microstructure comprising a very fine bainitic matrix and vanadium carbide precipitates.
  • Rolling element bearings are devices that permit constrained relative motion between two parts.
  • Rolling element bearings comprise inner and outer raceways and a plurality of rolling elements
  • a number of surface or case hardening processes are known for improving rolling contact fatigue performance.
  • Through-hardened components differ from case-hardened components in that the hardness is uniform or substantially uniform throughout the component.
  • the martensite through-hardening process involves
  • the steel may then be low- temperature tempered to stabilize the microstructure.
  • the bainite through-hardening process involves austenitising the steel prior to quenching above the martensite start temperature. Following quenching, an isothermal bainite transformation is performed. Bainite through-hardening is sometimes preferred in steels instead of martensite through- hardening. This is because a bainitic structure may possess superior mechanical properties, for example toughness and crack propagation resistance.
  • WO 01/79568 describes a method for the production of a part for a rolling bearing. Summary
  • the present invention provides a bearing component formed from a steel composition comprising:
  • the bearing component is formed from the alloy as herein described and preferably comprises lower bainite as the main phase (typically at least 60% bainite, more typically at least 80% bainite) .
  • the plates of bainite are very fine.
  • the material preferably has a microstructure comprising plates of bainite (preferably lower bainite) of less than 100 nm thickness, typically from 10 to 50 nm, more typically from 20 to 40 nm.
  • the plates of bainite are advantageously interspersed with retained austenite thin films.
  • the bainite typically forms at least 60% of the microstructure, more typically at least 80% (by volume) .
  • the steel preferably also contains vanadium carbide
  • the microstructure will comprises at least 3% carbides, more typically at least 5% (by volume) .
  • microstructure and resulting mechanical properties lead to improved rolling contact fatigue performance in the bearing component.
  • the steel composition preferably comprises from 0.9 - 1.7 wt . % carbon, more preferably from 0.9 to 1.6 wt . % carbon, still more preferably from 1.0 to 1.5 wt . % carbon. In combination with the other alloying elements, this results in the desired fine (lower) bainite microstructure. Carbon acts to lower the bainite start transformation temperature. Carbon also forms desirable carbide precipitates with vanadium, which improves the mechanical properties.
  • the steel composition preferably comprises 1.2 - 1.8 wt . % silicon, more preferably from 1.3 - 1.7 wt . % silicon, still more preferably from 1.4 - 1.6 wt . % silicon. In combination with the other alloying elements, this results in the desired microstructure . Silicon helps to suppress the precipitation of cementite. However, too high a silicon content may result in undesirable surface oxides and a poor surface finish. For this reason, the maximum silicon content is 2 wt.%, more preferably 1.9 wt . % .
  • the steel composition preferably comprises 1.2 - 1.8 wt.% manganese, more preferably from 1.3 - 1.7 wt.% manganese, still more preferably from 1.4 - 1.6 wt.% manganese.
  • Manganese acts to increase the stability of austenite relative to ferrite. Manganese may also increase the hardenability .
  • the steel composition preferably comprises from 0.15 - 0.35 wt.% molybdenum, more preferably from 0.2 - 0.3 wt.% molybdenum.
  • Molybdenum acts to avoid austenite grain boundary embrittlement owing to impurities such as, for example, phosphorus. Molybdenum also acts to increase hardenability and reduce the bainite start temperature
  • the steel composition preferably comprises 1.5 to 2.5 wt.% chromium, more preferably from 1.7 - 2.3 wt.% chromium, still more preferably from 1.8 - 2.0 wt.% chromium.
  • Chromium acts to increase hardenability and reduce the bainite start temperature.
  • the steel composition preferably comprises from 0.3 - 1.2 wt.% cobalt, more preferably from 0.5 - 1.0 wt.% cobalt, still more preferably 0.6 - 0.9 wt.% cobalt.
  • Cobalt has been found to improve the corrosion resistance of the bearing component. This is very important for bearing components for wind turbines or marine pods, for example. Such bearings may become contaminated by sea water, which can drastically reduce the service life of the bearing.
  • Cobalt also acts to accelerate the transformation to
  • the steel composition preferably comprises from 1.1 - 1.7 wt . % aluminium, more preferably from 1.2 - 1.5 wt . %
  • the steel composition preferably comprises from 0.2 - 4.0 wt . % vanadium, more preferably from 0.2 - 3.0 wt . % vanadium, still more preferably 0.3 - 1.0 wt . % vanadium. Vanadium combines with carbon to form vanadium carbide precipitates. The vanadium carbide precipitates increase the yield
  • Vanadium carbonitride precipitates may also be present.
  • the steel composition may optionally include one or more of the following elements
  • the steel composition preferably comprises little or no sulphur, for example from 0 - 0.015 wt . % sulphur.
  • the steel composition preferably comprises little or no phosphorous, for example from 0 - 0.02 wt . % phosphorous.
  • the sum of arsenic, tin and antimony is preferably no more than 0.075 wt . % .
  • the steel composition preferably comprises ⁇ 15 ppm oxygen. Oxygen may be present as an impurity.
  • the steel composition preferably comprises ⁇ 30 ppm
  • Titanium may be present as an impurity.
  • the steel composition preferably comprises ⁇ 50 ppm calcium. Calcium may be present as an impurity but may also be added intentionally in very small amounts.
  • the steel composition may also contain very small amounts of nitrogen .
  • the steel composition may be made by the following route, provided by way of example.
  • the steel can be cast into moulds followed by high temperature soaking and then hot rolling. This results in the vanadium being dissolved in the austenite phase. Slow cooling precipitates out vanadium carbide and possibly also vanadium carbonitride, while the austenite mostly transforms to pearlite.
  • austenitising results in austenite being formed together with retained vanadium carbide precipitates (and possibly also vanadium carbonitride precipitates) .
  • the step of austenitising is suitably performed at a temperature of less than 1050 ° C - preferably at a temperature of less than 950 ° C - to prevent excessive austenite grain growth and to prevent the dissolution of the retained vanadium carbide precipitates (and any vanadium carbonitride precipitates) .
  • the material may subsequently undergo austempering/bainite through-hardening to transform the austenite to bainite
  • the microstructure of the steel composition preferably comprises a very fine bainitic matrix and vanadium carbide precipitates.
  • the material preferably has a microstructure comprising plates of bainite (preferably lower bainite) of less than 100 nm thickness, typically from 10 to 50 nm, more typically from 20 to 40 nm.
  • the plates of bainite are advantageously interspersed with retained austenite thin films.
  • vanadium carbonitride precipitates may also be present .
  • the steel for use in the bearing component according to the present invention may contain unavoidable impurities, although, in total, these are unlikely to exceed 0.5 wt . % of the composition.
  • the alloys Preferably, contain unavoidable impurities in an amount of not more than 0.3 wt . % of the composition, more preferably not more than 0.1 wt . % of the composition.
  • the phosphorous and sulphur contents are preferably kept to a minimum.
  • the alloys according to the present invention may consist essentially of the recited elements. It will therefore be appreciated that in addition to those elements which are mandatory other non-specified elements may be present in the composition provided that the essential characteristics of the composition are not materially affected by their presence .
  • the bearing component according to the present invention is formed from a steel that transforms to bainite at a
  • the transformation time for bainite formation to cease is typically from 3 hours to 80 days, more typically from 6 hours to 60 days.
  • the transformation time depends on the transformation temperature: the time is longer for lower temperatures.
  • the amount of bainite that is formed depends on the transformation temperature: more bainite is formed at lower temperatures.
  • the amount of retained austenite increases for higher transformation temperatures.
  • the microstructure of the as-transformed (bainitically heat treated) steel is different from ordinary bainitic bearing steel structures in two respects.
  • An appreciably amount of vanadium carbide precipitation takes place during the hot-rolling schedule of the steel during manufacture.
  • a typical heating temperature is 1150°C, at which a portion of the vanadium becomes soluble in the austenitic phase.
  • the "in solid solution” vanadium then precipitates during hot-rolling, thereby strengthening the steel structure.
  • the steel is then allowed to cool slowly from a temperature of around 900°C to room temperature in order to: prevent the vanadium precipitates coarsening or undergoing dissolution if the hot-rolled material is exposed to temperatures higher than 900°C; allow further precipitation of vanadium precipitates; and prevent the formation of bainite and/or martensite.
  • the vanadium carbide precipitates are not dissolved and are retained to improve both strength and hardness.
  • the matrix austenitic phase has a chemical composition which still allows it to subsequently transform into very fine nano-structured bainite upon isothermal holding at the appropriate temperature.
  • the process for the manufacture of the steel for the bearing component avoids rapid cooling so that residual stresses can be avoided in large component pieces.
  • the bearing component may be part of a rolling element bearing, for example the bearing inner or outer ring, or the ball or roller element.
  • the bearing component could also be part of a linear bearing such as ball and roller screws.
  • the present invention also provides a bearing comprising a bearing component as herein described.
  • An example of a suitable bainitic steel composition for use in the present invention includes (the balance being Fe and any unavoidable impurities) :
  • Figure 1 contains a plot showing the carbon and vanadium composition ranges within which partial austenitisation to yield austenite and vanadium carbide is possible at 920°C and 1 atm, highlighted.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
  • Rolling Contact Bearings (AREA)

Abstract

La présente invention concerne un composant porteur formé d'une composition d'acier comprenant du carbone, du silicium, du manganèse, du molybdène, du chrome, du cobalt, de l'aluminium, du vanadium, éventuellement au moins un des éléments suivants parmi soufre, phosphore, arsenic, étain, le solde étant constitué de fer, ainsi que des impuretés inévitables.
PCT/EP2012/071293 2011-10-28 2012-10-26 Composant porteur WO2013060866A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP2011069059 2011-10-28
EPPCT/EP2011/069059 2011-10-28

Publications (1)

Publication Number Publication Date
WO2013060866A1 true WO2013060866A1 (fr) 2013-05-02

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PCT/EP2012/071293 WO2013060866A1 (fr) 2011-10-28 2012-10-26 Composant porteur

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015113574A1 (fr) * 2014-01-29 2015-08-06 Aktiebolaget Skf Alliage d'acier

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001079568A1 (fr) 2000-04-13 2001-10-25 Skf Engineering And Research Centre B.V. Procede de production d'une piece de roulement a rouleaux
WO2009118166A1 (fr) * 2008-03-25 2009-10-01 Aktiebolaget Skf Composant de palier
WO2010013054A2 (fr) * 2008-07-31 2010-02-04 The Secretary Of State For Defence Acier bainitique et ses procédés de fabrication

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001079568A1 (fr) 2000-04-13 2001-10-25 Skf Engineering And Research Centre B.V. Procede de production d'une piece de roulement a rouleaux
WO2009118166A1 (fr) * 2008-03-25 2009-10-01 Aktiebolaget Skf Composant de palier
WO2010013054A2 (fr) * 2008-07-31 2010-02-04 The Secretary Of State For Defence Acier bainitique et ses procédés de fabrication

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015113574A1 (fr) * 2014-01-29 2015-08-06 Aktiebolaget Skf Alliage d'acier

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