US20100314006A1 - Steel for induction hardening with excellent cold workability, rolling member made of the same, and motion guide device using rolling member - Google Patents

Steel for induction hardening with excellent cold workability, rolling member made of the same, and motion guide device using rolling member Download PDF

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US20100314006A1
US20100314006A1 US12/744,818 US74481808A US2010314006A1 US 20100314006 A1 US20100314006 A1 US 20100314006A1 US 74481808 A US74481808 A US 74481808A US 2010314006 A1 US2010314006 A1 US 2010314006A1
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steel
induction hardening
less
rolling
hardness
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US12/744,818
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Inventor
Kazuya Hashimoto
Genjiro Ise
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Sanyo Special Steel Co Ltd
THK Co Ltd
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Sanyo Special Steel Co Ltd
THK Co Ltd
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Assigned to SANYO SPECIAL STEEL CO., LTD., THK CO., LTD reassignment SANYO SPECIAL STEEL CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HASHIMOTO, KAZUYA, ISE, GENJIRO
Publication of US20100314006A1 publication Critical patent/US20100314006A1/en
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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
    • C21D1/06—Surface hardening
    • C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation
    • C21D1/10—Surface hardening by direct application of electrical or wave energy; by particle radiation by electric induction
    • 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
    • C21D9/36—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for balls; for rollers
    • 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
    • C21D9/38—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for roll bodies
    • 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
    • C22C38/02—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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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
    • C21D2211/001—Austenite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the present invention relates to steel for induction hardening by which lowering of a fatigue life hardly occurs under lubrication failure, and further to a motion guide device including, as apart thereof, a rolling member made of the steel for induction hardening.
  • FIG. 1 is a partially outer perspective sectional view for explaining a schematic configuration of a motion guide device, and shows a linear motion guide device, incorporated into a machine tool, for guiding a table for supporting a workpiece, for example.
  • This motion guide device is constructed from a track rail (bearing ring) 1 and a slide board (slide member) 3 .
  • Ball rolling surfaces 1 a are formed along a longitudinal direction on the track rail 1 .
  • the slide board 3 fits this track rail 1 via a number of balls 2 as rolling members (or rolling material), and includes an endless circulation passage for the balls 2 therein.
  • the slide board 3 reciprocally moves on the track rail 1 with circulation of the balls 2 .
  • the slide board 3 may be caused to reciprocally move on the track rail 1 as a stationary side.
  • the slide board 3 described above is constructed from a substantially saddle-shaped block 5 and a pair of end plates 6 .
  • the substantially saddle-shaped block 5 has amount surface 5 a for mounting a table (not shown in the drawing) or the like.
  • the pair of end plates 6 is fixed on both front and back end surfaces of this block 5 .
  • the endless circulation passage described above is constructed from a loaded ball rolling surface 5 b , a ball return groove 5 c and a direction changing passage (not shown in the drawing).
  • the loaded ball rolling surface 5 b and ball return groove 5 c are formed in this block 5 so as to correspond to the ball rolling surface 1 a of the track rail 1 .
  • the direction changing passage is formed in both of the end plates 6 to communicate the loaded rolling surface 5 b with the ball return groove 5 c.
  • each ball 2 is in contact with the track rail 1 substantially at a point, and each ball 2 is in contact with the slide board 3 substantially at a point. Since this contact portion repeatedly moves on the same track, a rolling load is applied to the track rail 1 and the slide board 3 .
  • a film thickness of lubricating oil is structurally thin in the contact portion between each ball 2 ad the track rail 1 and the contact portion between each ball 2 and the slide board 3 . For this reason, rolling/sliding contact of metal occurs, and a surface area of the track rail 1 and the slide board 3 is damaged, whereby a case where a fatigue life is markedly lowered also occurs.
  • Patent Literature 1 an invention to improve a fatigue life by increasing the amount of residual austenite has been proposed (for example, see Patent Literature 1 described below).
  • this invention allows the fatigue life at incorporation of foreign objects to be improved, but lowering of the fatigue life due to rolling/sliding contact cannot be improved stably.
  • Patent Literature 1 described below an invention is disclosed in which a fatigue life is improved when incorporation of foreign objects is reduced by reducing the amount of residual austenite (for example, see Patent Literature 2 described below).
  • Patent Literature 2 an invention is disclosed in which a fatigue life is improved when incorporation of foreign objects is reduced by reducing the amount of residual austenite (for example, see Patent Literature 2 described below).
  • this invention cannot stably improve the fatigue life at incorporation of foreign objects as Patent Literature 1 described below.
  • Patent Literature 1 Japanese Patent Application Publication No. 11-209844
  • Patent Literature 2 Japanese Patent Application Publication No. 2001-165161
  • Patent Literature 3 Japanese Patent Application Publication No. 2004-183016
  • Patent Literature 1 is a prior application of the invention of applicants of the present application.
  • Si is to be contained with 0.4% or more and hardness after induction hardening is required to be 61 HRC or more in order to suppress lowering of fatigue strength (or fatigue life) due to rolling/sliding contact of metal.
  • an additive amount of Si is increased, cold workability is marred.
  • the amount of C is reduced, hardness after induction hardening cannot be obtained sufficiently.
  • the steel for induction hardening according to the present invention is directed to steel for induction hardening containing: with percent by mass, C: 0.7 to 0.9%; Si: 0.4 to 1.0%; Mn: 0.5 to 1.25%; P: 0.030% or less; S: 0.030% or less; Cr: 0.4% or less; Al: 0.05% or less; Ti: 0.003% or less; and O: 0.0020% or less, wherein [Mn] ⁇ 0.5+0.35/[Si] is met, and the steel further contains Fe (iron) and unavoidable impurity and the steel has annealing hardness of 93 HRB or less, and wherein an induction hardening layer after induction hardening has residual austenite of 20 to 40% and hardness of 61 HRC or more.
  • chemical composition of steel has C in the range of 0.7 to 0.9% and Si in the range of 0.4 to 1.0%, and annealing hardness is 93 HRB or less.
  • an induction hardening layer by subjecting a product processed by cold working to induction hardening has residual austenite of 20 to 40% and high hardness of 61 HRC or more. It has excellent toughness.
  • a crack is hardly generated from a damaged portion caused by incorporation of foreign objects in the product and rolling/sliding contact. If a crack is generated, the generated crack hardly propagates, and flaking is hardly generated.
  • the induction hardening layer is high hardness of 61 HRC or more, it is preferable to be used as a track rail of a motion guide device. Since steel having both high toughness and high hardness can be obtained, it becomes excellent steel for induction hardening. Further, since this steel for induction hardening used for resistance to a foreign object environment and resistance to rolling/sliding contact does not need a carburizing process, it is possible to obtain steel with higher (that is, desirable) hardness and higher toughness at low cost. This is preferable for practice, in particular.
  • a member made of the steel for induction hardening has high hardness and high toughness, and can be utilized for a long usable life even under a foreign object environment and rolling/sliding contact.
  • the steel for induction hardening is inexpensive and has excellent machinability and cold workability.
  • the rolling member according to the present invention is a rolling member wherein an induction hardening layer having residual austenite of 20 to 40% and hardness of 61 HRC or more is formed by subjecting the steel for induction hardening as described above to cold working to form a shape of the rolling member and then subjecting the shape of the rolling member to induction hardening and tempering.
  • a motion guide device using the rolling member described above for a part of members of the motion guide device, for example, a track rail or a slide board.
  • the steel whose chemical composition has the amount of C in the range of 0.7 to 0.9% and the amount of Si in the range of 0.4 to 1.0%, and which has an induction hardening layer with high hardness of 61 HRC or more after cold working and has the amount of residual austenite of 20 to 40% is utilized for any one or both of the track rail and the slide board of the motion guide device, whereby a crack originating from a damaged portion caused by incorporation of foreign objects into lubricating oil to be used and rolling/sliding contact is hardly generated in the track rail of the motion guide device. As a result, a usable life of the motion guide device can be improved.
  • the steel for induction hardening according to the present invention since the amount of residual austenite in an induction hardening layer becomes 20 to 40%, it has excellent toughness. Even though foreign objects such as grit, dust and chip are incorporated into members of a product when the product is made, damage is hardly caused. Thus, a crack originated by the damage is hardly generated. Even though a crack is generated, the generated crack hardly propagates, and flaking is hardly generated. It is possible to improve a usable life of the product member made of this steel. Moreover, in the steel for induction hardening according to the present invention, since the degree of hardness of the induction hardening layer is high, 61 HRC or more, it is preferable for a track shaft of a motion guide device.
  • this steel for induction hardening merely contains, as chemical composition, expensive Ni or Mo at the unavoidable impurity level. Since it does not need a carburized hardening process, it is inexpensive. It has an effect that induction hardened steel for resistance to a foreign object environment, which is excellent in cold workability and machinability, can be obtained.
  • the rolling member according to the present invention has residual austenite of 20 to 40% by subjecting the steel for induction hardening according to the present invention described above to cold working to a shape of a rolling member and then subjecting it to induction hardening and tempering.
  • it has an effect that it is preferable in view of a fatigue life and it is formed in an induction hardening layer with hardness of 61 HRC or more.
  • the motion guide device according to the present invention is a motion guide device in which the rolling member according to the present invention described above is utilized as a part.
  • this motion guide device has high hardness of 61 HRC or more, a residual austenite layer of 20 to 40% and high toughness. Even though it is utilized under a foreign object environment, a crack is hardly generated from a damaged portion caused by the foreign objects. Even though a crack is generated, the crack hardly propagates, and flaking is hardly generated.
  • rolling/sliding contact hardly occurs even under lubrication failure, and damage is hardly caused. Thus, a crack originated by the damage is hardly generated.
  • the motion guide device according to the present invention does not contain expensive material or material that inhibits workability, it has an effect to be excellent in a long usable life and cost performance.
  • FIG. 1 is a schematic view of a motion guide device.
  • each of steel for induction hardening, a rolling member (or rolling material) using the steel for induction hardening and a motion guide device including the obtained rolling member as a member will be described specifically with reference to Tables and Drawing.
  • the “lubrication failure” in this specification means a state in which foreign objects incorporate into lubricating oil and concentration of stress on its dent as a major factor leads to flaking, and a state in which a film thickness of the lubricating oil is thin because surface roughness is large, the degree of viscosity of the lubricating oil is low, and/or the amount of lubricating oil is lacking, or because of combination thereof, whereby rolling/sliding contact of metal occurs mainly.
  • a motion guide device is defined as a collective term of a linear motion guide device shown in FIG. 1 and ones in which a track shaft and a slide member are assembled mutually movably via a ball spline, a ball screw, or a rolling member such as a ball or a roller (not shown in the drawing).
  • steel for induction hardening has chemical composition containing, by percent by mass, C: 0.7 to 0.9%, Si: 0.4 to 1.0%, Mn: 0.5 to 1.25%, P: 0.030% or less, S: 0.030% or less, Cr: 0.4% or less, Al: 0.05% or less, Ti: 0.003% or less and O: 0 . 0020 % or less; and meeting [Mn] ⁇ 0 . 5 + 0 . 35 /[Si], wherein the remnant is made of Fe and unavoidable impurity.
  • the steel for induction hardening composed of this composition is steel in which an induction hardening layer after induction hardening has residual austenite of 20 to 40% and hardness of 61 HRC or more.
  • C is an Element Required to Form Carbide by Means of induction hardening and to make hardness after tempering of the induction hardening layer be 61 HRC or more.
  • C is an element particularly effective for generating residual austenite of 20 to 40% in the induction hardening layer.
  • C is regulated to less than 0.6%, desired hardness cannot be obtained in the induction hardening layer.
  • C is regulated to less than 0.7%, a usable life of the motion guide device made of this steel becomes shorter under an environment in which rolling/sliding contact occurs.
  • C exceeds 0.9%, machinability and cold workability are deteriorated, and a hardening crack is further generated at induction hardening. Accordingly, C is regulated to 0.7 to 0.9%.
  • Si is an element to be added as a deoxidizing agent.
  • Si is less than 0.4%, a usable life of the motion guide device made of this steel becomes shorter under an environment in which rolling/sliding contact occurs.
  • it exceeds 1.0% machinability and cold workability are deteriorated, and the usable life becomes shorter under the environment in which rolling/sliding contact occurs. Accordingly, Si is regulated to 0.4 to 1.0%.
  • Mn is an element having a great effect to improve induction hardenability, and is an element effective for generating more residual austenite in an induction hardening layer.
  • Mn is regulated to less than 0.5%, it is impossible to ensure sufficient hardenability after induction hardening.
  • it exceeds 1.25% its machinability or cold workability is deteriorated. Accordingly, Mn is regulated to 0.5 to 1.25%, and preferably to 0.75 to 1.25%.
  • [Mn] ⁇ 0.5+0.35/[Si] is regulated by taking into consideration the fact that workability is deteriorated in the case where the amount of Si required to obtain a rolling fatigue life is ensured. Therefore, by limiting it by means of a relationship between the amount of Mn and the amount of Si, good workability can be obtained. Accordingly, [Mn] ⁇ 0.5+0.35/[Si] is met (or satisfied).
  • Cr is an element having an effect to improve induction hardenability and toughness of steel.
  • Cr is a carbide forming element and stabilizes carbide, hardness after softening annealing is not lowered. Accordingly, Cr is regulated to 0.4% or less, and preferably to 0.35% or less.
  • Al is an element to be added as a deoxidizing agent. However, in the case where Al is more than 0.05%, Al oxide is increased, whereby fatigue strength of the steel is lowered and workability is lowered. Accordingly, Al is regulated to 0.05% or less.
  • Ti is an element effective for preventing grain coarsening. However, in the case where Ti is rich, workability is lowered. Accordingly, Ti is regulated to 0.003% or less.
  • P 0.030% or less
  • P is an Element Having an Effect to Improve Corrosion resistance.
  • P is added so as to exceed 0.030%, it is segregated to grain boundary to promote intergranular embrittlement, and impact strength and bending strength are thus lowered. Accordingly, P is regulated to 0.030% or less.
  • MnS bonds to MN to Become Mns, Thereby Preventing Hot shortness.
  • MnS forms a nonmetallic inclusion to cause a fatigue life to be lowered.
  • S exceeds 0.03%, lowering of the fatigue life tends to occur. Accordingly, S is regulated to 0.03% or less.
  • MnS has an effect to improve machinability, it is desired that it is regulated to 0.010% or more.
  • O forms oxide together with other metallic element, and segregates in grain boundary to become a factor of hot shortness. In the case where O exceeds 0.0020%, a fatigue life may be lowered. Accordingly, O is regulated to 0.0020% or less, and preferably to 0.0015% or less.
  • N may further be contained in addition to the elements described above.
  • N heightens strength by partial solution to the steel.
  • N is contained too much, it encourages low-temperature brittleness markedly. Accordingly, it is desired that N is regulated to proper quantity when to be added appropriately, and its range is set to 0.01% or less.
  • residual austenite of an induction hardening layer is less than 20%, a fatigue life may be lowered when incorporation of foreign objects into a steel part occurs under a foreign object environment, and a life improvement effect cannot be obtained sufficiently.
  • the residual austenite has an effect to improve toughness as has already been known.
  • it has an effect that rolling/sliding contact hardly occurs and lowering of the fatigue life hardly occurs even though incorporation of foreign objects such as grit, dust and chip into a track rail of the motion guide device occurs under an environment in which the foreign objects exist, for example.
  • a lower limit of the amount of residual austenite in the induction hardening layer is regulated to 20% or more, and particularly to 25% or more.
  • an upper limit of the residual austenite in the induction hardening layer is regulated to 40% or less, and particularly to 35% or less.
  • the steel By regulating surface hardness of induction hardened steel to 61 HRC or more, the steel has high hardness while having high toughness. A member made of this steel can be utilized for a long usable life even under a foreign object environment and even though rolling/sliding contact occurs.
  • a rolling member according to the present embodiment is one formed by using the steel for induction hardening according to the present embodiment described above to be subjected to cold working.
  • this formed rolling member is subjected to induction hardening to heat and harden a surface by means of high-frequency heating at 950 to 1,050° C. for 6 to 8 seconds, and is then subjected to low-temperature tempering at tempering temperature of 130 to 180° C., preferably at 150° C. and in tempering time for 60 to 180 minutes, preferably for about 80 minutes.
  • an induction hardening layer having residual austenite of 20 to 40% and hardness of 61 HRC or more has been formed.
  • surface heating temperature by the high-frequency heating exceeds 1,050° C.
  • a hardening crack is readily generated.
  • the surface heating temperature is less than 950° C., it may be impossible to ensure the residual austenite of 20% or more.
  • the motion guide device is one in which the rolling member according to the present embodiment described above is utilized for the track rail 1 and the slide board 3 provided on the track rail 1 of the linear motion guide device 7 shown in FIG. 1 .
  • the motion guide device that is, the linear motion guide device 7 has high hardness and high toughness, and is made of induction hardened steel for resistance to a foreign object environment and resistance to rolling/sliding contact in which it can be utilized with a long usable life even under a foreign object environment.
  • Apart of members thereof, particularly the track rail 1 or the slide board 3 provided on the track rail 1 are configured by the steel for induction hardening according to the present embodiment. Therefore, even though this linear motion guide device 7 is utilized under the foreign object environment, a crack is hardly generated from a damaged portion caused by the foreign objects or a damaged portion caused by rolling/sliding contact. Further, even though a crack is generated, the generated crack hardly propagates, and flaking is hardly generated. Moreover, since this linear motion guide device 7 does not contain expensive Ni or Mo as materials with a possible contained amount, it becomes the linear motion guide device 7 excellent in cost performance with a long usable life.
  • a round bar obtained by forging the steel in each of Examples and Comparative Examples shown in Table 1 to ⁇ 65 mm was subjected to normalizing at 870° C., and disk-shaped flat plates each having a thickness of 10 mm were cut out of them after subjecting them to spheroidizing annealing at 740° C.
  • This disk-shaped flat plate with a thickness of 10 mm was subjected to high-frequency heating to keep surface temperature at 1,000° C. for 7 seconds; then subjected to polymer hardening; and tempering at 150° C. was further carried out for 80 minutes.
  • this hardened and tempered disk-shaped flat plate was subjected to grinding and polishing processing, and its surface is let into a mirrored state to be created in each test piece. Further, the degree of surface hardness of each of these test pieces was measured by means of a Rockwell hardness tester.
  • the thrust type Rolling Contact Fatigue Test under foreign object environment is a method of carrying out Rolling Contact Fatigue Test by means of a Mori thrust type rolling fatigue tester by putting foreign objects into lubricating oil. This test was carried out on conditions described below, and a rolling contact fatigue life of resistance to a foreign object environment was evaluated by L 50 (50% cumulative probability of fracture). In this evaluation, evaluation of each of Inventive Examples of the present application and Comparative Examples was indicated using a ratio when L 50 of Comparative Example No. 6 was set to one, and shown in Table 2.
  • Lubricant spindle oil (#60)
  • Foreign object input of powder of high-speed tool steel (SKH51) with hardness of 760 to 800 HV and particle size of 105 to 150 ⁇ m into the lubricant at the rate of one g/liter.
  • SBH51 high-speed tool steel
  • Each round bar forged to ⁇ 32 mm was subjected to normalizing at 870° C., and a cylinder whose rolling portion was ⁇ 26 mm were cut out of them after subjecting them to spheroidizing annealing at 740° C.
  • the cylinder was subjected to induction hardening at surface heating temperature of 1,000° C. for 7 seconds; then subjected to polymer hardening; and tempering at 150° C. was further carried out for 90 minutes. It was subjected to grinding and polishing processing, and its surface is let into a mirrored state to be created in a test piece.
  • the roller pitting test is a method of carrying out a rolling/sliding contact test under high surface pressure. The test was carried out for the test piece described above on conditions described below, and a fatigue life under a rolling/sliding contact condition was evaluated by L 50 (50% cumulative probability of fracture).
  • the amount of residual austenite of an induction hardened surface was measured with respect to a test piece manufactured in the similar manner to that of the test piece using Thrust Type Rolling Contact Fatigue Test under foreign object environment.
  • a measuring method was an X-ray diffraction method, and test results represented by a volume ratio (%) were shown in Table 2.
  • Annealing hardness was measured as the degree of hardness of a test surface of a test piece by means of a Rockwell hardness tester after subjecting it to spheroidizing annealing at 740° C. when the test piece for the thrust type rolling contact fatigue test under foreign object environment was manufactured. The measured results were shown in Table 2.
  • the L 50 usable life under the foreign object environment fell in the range of 2.1 to 2.7 in Examples 1 to 8 according to the present invention when Comparative Example 6 is set to one as reference.
  • the L 50 usable life that is a fatigue life under a rolling/sliding contact environment by the roller pitting test fell in the range of 2.1 to 3.0 in Examples 1 to 8 according to the present invention when Comparative Example 6 is similarly set to one as reference, and they were higher than Comparative Examples mutually.
  • the annealing hardness after being subjected to spheroidizing annealing described above fell in the range of 91 to 93 HRB in Examples 1 to 8 according to the present invention, and all of them were 93 HRB or less.
  • Comparative Examples 1 to 6 were 94 to 98 HRB and higher than Examples 1 to 8, and therefore, it can be seen that the steel according to the present invention has excellent cold workability.

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US12/744,818 2007-11-26 2008-11-25 Steel for induction hardening with excellent cold workability, rolling member made of the same, and motion guide device using rolling member Abandoned US20100314006A1 (en)

Applications Claiming Priority (3)

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JP2007-304012 2007-11-26
JP2007304012A JP5260032B2 (ja) 2007-11-26 2007-11-26 冷間加工性に優れた高周波焼入用鋼、該鋼からなる転動部材および転動部材を用いた直線運動装置
PCT/JP2008/003468 WO2009069283A1 (ja) 2007-11-26 2008-11-25 冷間加工性に優れた高周波焼入用鋼、該鋼からなる転動部材および転動部材を用いた運動案内装置

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KR (1) KR20100092458A (ko)
CN (1) CN101874124A (ko)
DE (1) DE112008003146T5 (ko)
WO (1) WO2009069283A1 (ko)

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US20160108491A1 (en) * 2012-10-29 2016-04-21 Nsk Ltd. Rolling bearing
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US20160108491A1 (en) * 2012-10-29 2016-04-21 Nsk Ltd. Rolling bearing
US9394583B2 (en) * 2012-10-29 2016-07-19 Nsk Ltd. Rolling bearing
CN103741033A (zh) * 2013-12-26 2014-04-23 马钢(集团)控股有限公司 一种提高塑性的铁路货车用高碳车轮钢及其车轮制备方法
USD875150S1 (en) * 2017-05-31 2020-02-11 Thk Co., Ltd. End plate for motion guide device
USD916939S1 (en) * 2017-05-31 2021-04-20 Thk Co., Ltd. End plate for motion guide device

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JP5260032B2 (ja) 2013-08-14
KR20100092458A (ko) 2010-08-20
JP2009127091A (ja) 2009-06-11
WO2009069283A1 (ja) 2009-06-04
CN101874124A (zh) 2010-10-27

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