WO2017170540A1 - Composant carbonitruré ayant une excellente résistance à la fatigue de surface et une excellente résistance à la fatigue en flexion, et procédé pour le fabriquer - Google Patents

Composant carbonitruré ayant une excellente résistance à la fatigue de surface et une excellente résistance à la fatigue en flexion, et procédé pour le fabriquer Download PDF

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WO2017170540A1
WO2017170540A1 PCT/JP2017/012621 JP2017012621W WO2017170540A1 WO 2017170540 A1 WO2017170540 A1 WO 2017170540A1 JP 2017012621 W JP2017012621 W JP 2017012621W WO 2017170540 A1 WO2017170540 A1 WO 2017170540A1
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fatigue strength
residual stress
amount
compressive residual
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PCT/JP2017/012621
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Japanese (ja)
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亮廣 松ヶ迫
武浩 酒道
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株式会社神戸製鋼所
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C1/00—Methods for use of abrasive blasting for producing particular effects; Use of auxiliary equipment in connection with such methods
    • B24C1/10—Methods for use of abrasive blasting for producing particular effects; Use of auxiliary equipment in connection with such methods for compacting surfaces, e.g. shot-peening
    • 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
    • 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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
    • C21D7/04—Modifying the physical properties of iron or steel by deformation by cold working of the surface
    • C21D7/06—Modifying the physical properties of iron or steel by deformation by cold working of the surface by shot-peening or the like
    • 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
    • C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
    • 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
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • 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
    • Y02P10/20—Recycling

Definitions

  • the present disclosure relates to a carbonitrided component having excellent surface fatigue strength and bending fatigue strength, and a method for manufacturing the same.
  • AT automatic transmissions
  • a planetary gear mechanism In order to meet the needs of higher engine output, smaller parts and lighter parts, ATs are being multi-staged. However, if the load torque is the same with the unit size unchanged, the tooth width will be reduced and the gears will be reduced. The load on is increased. Therefore, it is strongly desired to provide a gear excellent in fatigue strength (both surface fatigue strength and bending fatigue strength).
  • Patent Document 1 discloses a carburized part in which fatigue strength (bending fatigue strength) in the “low to medium cycle range” is significantly improved and a method for manufacturing the same.
  • Patent Document 2 discloses a carburized part or a carbonitrided part having excellent surface fatigue strength.
  • Patent Document 1 does not consider the surface fatigue strength, and the surface roughness Rz [maximum height roughness Rz defined in JIS B 0601 (2001)] of the carburized part in the example is about 6 to 11 ⁇ m. And very big.
  • Patent Document 2 the value of internal compressive residual stress is insufficient, and the surface fatigue strength is not sufficiently strengthened.
  • Patent Documents 1 and 2 it is not possible to realize a component excellent in surface fatigue strength and bending fatigue strength that can sufficiently meet recent demands for downsizing and high stress load.
  • Embodiments of the present invention have been made in view of the above circumstances, and an object of the present invention is to provide a carbonitrided component excellent in both surface fatigue strength and bending fatigue strength, and a method for manufacturing the same.
  • a carbonitriding component excellent in surface fatigue strength and bending fatigue strength according to an embodiment of the present invention that has solved the above problems is a carbonitriding component having a carbonitriding layer on the surface of a steel material, and the steel material has a mass %, C: 0.15 to 0.25%, Si: 0.4 to 1%, Mn: 0.30 to 0.6%, P: more than 0%, 0.02% or less, S: 0% More than 0.02%, Cr: 1.2 to 2%, Mo: 0.3 to 0.5%, N: more than 0%, 0.015% or less, the balance from iron and inevitable impurities
  • the carbonitrided layer has a hardness of 850 HV or more at a depth of 25 ⁇ m from the surface, an absolute value of a compressive residual stress value of 200 MPa or more at a depth of 200 ⁇ m from the surface, and a depth of 200 ⁇ m from the surface.
  • the absolute value of the maximum compressive residual stress value is 850 MPa or more, and JIS
  • the steel material is further in mass%, V: more than 0%, 0.5% or less, Ti: more than 0%, 0.5% or less, Nb: more than 0%, 0.5 % Or less, and Al: at least one element selected from the group consisting of more than 0% and 0.5% or less.
  • the steel material further includes, in mass%, Cu: more than 0%, 0.3% or less, Ni: more than 0%, 0.3% or less, and B: more than 0%,. It contains at least one element selected from the group consisting of 01% or less.
  • a carbonitriding component manufacturing method that has solved the above problems is a method for manufacturing the carbonitriding component according to any one of the above, and after the steel material is carbonitriding
  • the gist is that the processing is performed in the order of shot peening using shot grains having a particle diameter of more than 300 ⁇ m, polishing, and shot peening using shot grains having a particle diameter of 300 ⁇ m or less.
  • FIG. 1A is a diagram showing the shape of a small roller among the roller pitching test pieces used in this example.
  • FIG. 1B is a diagram showing the shape of a large roller among the roller pitching test pieces used in this example.
  • FIG. 2 is a diagram showing the shape of a four-point bending test piece used in this example.
  • the Si, Cr, and Mo components are optimized to increase the temper softening resistance.
  • the surface hardness specifically, the hardness at a depth of 25 ⁇ m from the surface
  • the absolute value of the internal compressive residual stress is increased to 200 MPa or more to suppress breakage at the internal origin.
  • the absolute value of the surface compressive residual stress (specifically, the maximum compressive residual stress value from the surface to the 200 ⁇ m depth position) is increased to 850 MPa or more to suppress the fracture at the surface starting point.
  • the surface roughness (ten-point average roughness Rz in the embodiment of the present invention) is reduced to 2.5 ⁇ m or less to suppress the breakage at the surface starting point.
  • the part in order to obtain a part that satisfies all the requirements (i) to (v), the part was manufactured as follows. First, carbon steel was subjected to carbonitriding treatment to the steel material whose components were appropriately controlled as in (i) above, to ensure the surface hardness of (ii) above and to increase the softening resistance at the time of temperature rise.
  • a method of performing a polishing process during two-stage shot peening using shot grains having different particle diameters is effective. It has been found. Specifically, first, shot peening is performed with shot grains having a large particle diameter (projection material) to secure the internal compressive residual stress of (iii), and then polishing is performed to obtain the surface roughness (v) ( Rz) is reduced. Thereafter, it was found that if shot peening was performed with small-sized shot grains to ensure the surface compressive residual stress of (iv) above, a desired part could be obtained, and an embodiment of the present invention was completed.
  • Patent Document 1 described above also describes that it is preferable to perform two-stage shot peening, but it is disclosed that the polishing process is performed between the first stage and the second stage as in the embodiment of the present invention. It has not been. So far, there is a technique for performing shot peening twice as in Patent Document 1, but generally, shot peening is continuously performed from the viewpoint of productivity and the like, and as in the embodiment of the present invention, A polishing process is not interposed. As proved in the column of Examples described later, it is confirmed that when the polishing treatment is not performed, Rz defined in the embodiment of the present invention is not obtained and becomes high, and the surface fatigue strength is lowered.
  • a carbonitriding component has a carbonitriding layer on the surface of a steel material, and the steel material is C: 0.15 to 0.25%, Si: 0.4 to 1%, Mn: 0.30 to 0.6%, P: more than 0%, 0.02% or less, more than 0%, S: 0.02% or less, Cr: 1.2 to 2% , Mo: 0.3 to 0.5%, N: more than 0%, 0.015% or less, the balance is made of iron and inevitable impurities, and the carbonitrided layer has a depth of 25 ⁇ m from the surface.
  • the hardness is 850 HV or more
  • the absolute value of the compressive residual stress value at the 200 ⁇ m depth position from the surface is 200 MPa or more
  • the absolute value of the maximum compressive residual stress value from the surface to the 200 ⁇ m depth position is 850 MPa or more.
  • the ten-point average roughness Rz specified by B0601 (1994) is 2.5 ⁇ m or less. There is a feature in the point.
  • the hardness at a depth of 25 ⁇ m from the surface is simply the surface hardness
  • the absolute value of the compressive residual stress at the depth of 200 ⁇ m from the surface is simply the internal compressive residual stress value
  • the position of the depth of 200 ⁇ m from the surface is simply abbreviated as the surface compressive residual stress value.
  • the component according to the embodiment of the present invention is premised on having a carbonitriding layer on the surface. Thereby, surface hardness can be raised to 850 HV or more. On the other hand, it is demonstrated in the column of the example described later that the desired surface hardness cannot be obtained by a normal carburizing treatment.
  • the surface hardness is set to 850 HV or more in terms of Vickers hardness.
  • 850 HV or more is 875 HV or more, More preferably, it is 900 HV or more.
  • the upper limit is not particularly limited from the above viewpoint, but it is preferably 1100 HV or less in consideration of applying residual stress in shot peening.
  • the absolute value of the compressive residual stress value at 200 ⁇ m depth from the surface is 200 MPa or more
  • the application of internal compressive residual stress is useful for suppressing fracture at the internal starting point. That is, when the load increases due to surface fatigue, spalling failure that breaks at the internal origin may occur, but spalling failure can be suppressed by increasing the internal compressive residual stress value.
  • the absolute value (internal compressive residual stress value) of the compressive residual stress value at a depth of 200 ⁇ m from the surface is set to 200 MPa or more. Preferably it is 210 MPa or more, More preferably, it is 220 MPa or more. In order to give a high compressive residual stress to the inside, it is effective to perform shot peening using shot grains having a particle size of more than 300 ⁇ m and a large particle size, as will be described later.
  • the absolute value of the maximum compressive residual stress value from the surface to the 200 ⁇ m depth position is 850 MPa or more
  • the application of surface compressive residual stress is effective in improving bending fatigue strength and surface fatigue strength (pitting).
  • the absolute value of the maximum compressive residual stress value (surface compressive residual stress value) from the surface to the 200 ⁇ m depth position is set to 850 MPa or more.
  • it is 875 MPa or more, More preferably, it is 900 MPa or more.
  • the “maximum compressive residual stress value from the surface to a 200 ⁇ m depth position” is the maximum value of the compressive residual stress value up to the depth position, and the maximum value is obtained from the surface, generally less than 50 ⁇ m. Position.
  • it is effective to perform shot peening using shot grains having a grain size of 300 ⁇ m or less and a small grain size.
  • Rz is set to 2.5 ⁇ m or less.
  • Rz is set to 2.5 ⁇ m or less.
  • Rz is 2.3 micrometers or less, More preferably, it is 2.0 micrometers or less.
  • the lower limit is not particularly limited from the above viewpoint, but is preferably 0.5 ⁇ m or more in consideration of processing costs and the like. In order to reduce Rz, as described later, it is effective to perform a polishing process during shot peening.
  • C 0.15-0.25%
  • the C content is 0.15% or more.
  • the C content is preferably 0.16% or more, and more preferably 0.17% or more. However, if the amount of C becomes excessive, machinability and toughness deteriorate, so the amount of C is made 0.25% or less.
  • the C content is preferably 0.24% or less, and more preferably 0.23% or less.
  • Si 0.4 to 1% Si is useful as an element for improving temper softening resistance. Specifically, in a gear or the like, the temperature of the contact portion rises during driving and the hardness decreases, but by adding Si, softening at the time of temperature rise is suppressed and the surface hardness can be maintained. As a result, the surface fatigue strength such as pitting and the wear resistance are improved.
  • the Si amount is set to 0.4% or more.
  • the amount of Si is preferably 0.45% or more, and more preferably 0.50% or more. However, if the Si amount becomes excessive, the machinability deteriorates, so the Si amount is set to 1% or less.
  • the amount of Si is preferably 0.8% or less, and more preferably 0.7% or less.
  • Mn 0.30 to 0.6% Mn is a hardenability improving element, and when the amount of Mn is less than 0.30%, FeS is formed and productivity is lowered. Therefore, the amount of Mn is set to 0.30% or more.
  • the amount of Mn is preferably 0.33% or more, and more preferably 0.35% or more. However, if the amount of Mn becomes excessive, the machinability decreases, so the amount of Mn is set to 0.6% or less.
  • the amount of Mn is preferably 0.5% or less, and more preferably 0.45% or less.
  • P more than 0% and 0.02% or less
  • P is an element inevitably contained as an impurity in the manufacturing process, etc., segregating at the grain boundary, workability, fatigue characteristics (surface fatigue strength and bending fatigue strength), etc. Reduce. Therefore, the P content is 0.02% or less.
  • extremely reducing the amount of P causes an increase in steelmaking costs.
  • S more than 0% and 0.02% or less S is an element that is inevitably contained as an impurity in the production process, etc., as in the case of P, and precipitates as MnS to exhibit fatigue properties (surface fatigue strength and bending fatigue strength). Reduce impact characteristics. Therefore, the S content is 0.02% or less. The smaller the amount of S, the better. It is preferably 0.015% or less, and more preferably 0.010% or less. However, extremely reducing the amount of S causes an increase in steelmaking costs.
  • Cr acts as a hardenability improving element like Mn, and is also useful as a temper softening resistance improving element like Si.
  • the Cr content is set to 1.2% or more.
  • the amount of Cr is preferably 1.25% or more, and more preferably 1.30% or more. However, if the amount of Cr becomes excessive, the cost increases and the machinability decreases, so the Cr amount is set to 2% or less.
  • the amount of Cr is preferably 1.8% or less, and more preferably 1.5% or less.
  • Mo 0.3 to 0.5% Mo is useful as a hardenability improving element and a temper softening resistance element like Cr. In order to effectively exhibit these actions, the Mo amount is set to 0.3% or more.
  • the Mo amount is preferably 0.32% or more, and more preferably 0.35% or more. However, if the amount of Mo becomes excessive, the cost increases and the machinability decreases, so the amount of Mo is set to 0.5% or less.
  • the Mo amount is preferably 0.48% or less, and more preferably 0.45% or less.
  • N more than 0% and 0.015% or less N is an element that is inevitably contained as an impurity in the manufacturing process and the like, and lowers workability by strain aging. Therefore, the N content is 0.015% or less.
  • extremely reducing the amount of N causes an increase in steelmaking costs.
  • the steel material constituting the carbonitriding component according to the embodiment of the present invention satisfies the above components, and the balance is iron and unavoidable impurities.
  • the steel material can further contain the following selective components as required.
  • V more than 0%, 0.5% or less
  • Ti more than 0%, 0.5% or less
  • Nb more than 0%, 0.5% or less
  • Al more than 0%, 0.5% or less
  • At least one element selected from the group These elements are elements that improve toughness and improve fatigue strength (surface fatigue strength and bending fatigue strength) by grain refinement after carbonitriding.
  • the V amount 0.05% or more
  • the Nb amount 0.05% or more
  • Al 0.01% or more.
  • the above-mentioned action is saturated, but also coarse precipitates are formed and the strength is lowered.
  • V amount 0.5% or less, Ti amount: 0.5% or less, Nb amount: 0.5% or less, and Al amount: 0.5% or less. More preferably, the V amount is 0.45% or less, the Ti amount is 0.45% or less, the Nb amount is 0.45% or less, and the Al amount is 0.45% or less. 4% or less, Ti content: 0.4% or less, Nb content: 0.4% or less, Al content: 0.4% or less. These elements may be added alone or in combination of two or more.
  • Cu more than 0%, 0.3% or less
  • Ni more than 0%, 0.3% or less
  • B more than 0%, 0.01% or less.
  • the amount of Cu is 0.25% or less
  • the amount of Ni is 0.25% or less
  • the amount of B is 0.008% or less
  • the amount of Cu is 0.2% or less
  • the amount of Ni is 0.00. 2% or less
  • shot peening primary shot peening
  • polishing shot having a grain size of 300 ⁇ m or less. It has a gist in that it is processed in the order of shot peening (secondary shot peening) using grains.
  • carbon steel is carbonitrided with the above composition.
  • carbon potential for example, after carburizing under conditions of 900 to 980 ° C., carbon potential of 0.7 to 0.9 mass%, 100 to 500 minutes, 800 to 900 ° C., Nitriding was performed under conditions of carbon potential 0.7 to 0.9 mass%, ammonia 3 to 8 vol%, 100 to 500 minutes, and then oil-cooled at 60 to 100 ° C, 100 to 200 ° C, 60 to 180. It is preferable to perform carbonitriding under the condition of a minute tempering treatment.
  • shot peening using large grain size shot grains (primary shot grains) having a grain size of more than 300 ⁇ m is performed.
  • shot peening using large grain size shot grains (primary shot grains) having a grain size of more than 300 ⁇ m is performed.
  • a high residual stress is applied to the inside (at a depth of 200 ⁇ m from the surface).
  • the surface roughness Rz is large.
  • the particle size of the primary shot grains to be used is not particularly limited as long as it is in the above range, and is preferably 400 ⁇ m or more and 1200 ⁇ m or less, for example.
  • polish In the embodiment of the present invention, it is important to perform the polishing treatment before the next secondary shot peening, whereby the surface is removed by about 20 to 50 ⁇ m, and the surface roughness Rz after the polishing is the embodiment of the present invention. And the surface fatigue strength is improved.
  • the polishing may be mechanical polishing using a grindstone, sandpaper or the like. Further, electrolytic polishing or chemical polishing may be used.
  • shot peening using small grain size shot grains (secondary shot grains) having a grain size of 300 ⁇ m or less is performed.
  • the surface roughness Rz does not change much and remains reduced to the desired level, and a high maximum compressive residual stress is applied to the surface.
  • the particle size of the secondary shot particles to be used is not particularly limited as long as it is in the above range, and is preferably 20 ⁇ m or more and 200 ⁇ m or less, for example.
  • the hardness of the shot grains may be the same as in the examples described later, but in consideration of the residual stress application efficiency and the like, the secondary shot grains are preferably harder than the primary shot grains.
  • Steel type A in Table 1 is an SCr420H equivalent steel of conventional steel, and is a steel type that has a small amount of Si, Cr, Mo, and a large amount of Mn compared to the embodiment of the present invention.
  • roller pitching test pieces having the shapes shown in FIGS. 1A and 1B and 4-point bending test pieces having the shapes shown in FIG. 2 were prepared as follows.
  • test pieces thus obtained were subjected to heat treatment (carburizing treatment or carbonitriding treatment) and processing (primary shot peening, polishing, secondary shot peening) as shown in Table 2.
  • heat treatment carburizing treatment or carbonitriding treatment
  • processing primary shot peening, polishing, secondary shot peening
  • Carburization was carried out under the conditions of 950 ° C., carbon potential 0.8 mass%, 140 minutes, then held at 845 ° C., carbon potential 0.8 mass%, 30 minutes, then oil cooled at 80 ° C., 160 A tempering treatment at 120 ° C. for 120 minutes was performed.
  • Carburizing and nitriding Carburizing was performed under conditions of 940 ° C., carbon potential of 0.85 mass%, 300 minutes, and then nitriding was performed under conditions of 840 ° C., carbon potential of 0.85 mass%, ammonia 5 volume%, and 240 minutes. Then, oil cooling was performed at 80 ° C., and tempering treatment was performed at 160 ° C. for 120 minutes.
  • Primary shot peening Primary (large particle size) shot peening was performed using a projection material having a particle size of 1000 ⁇ m and an average hardness of 800 HV so that the arc height was 0.2 mmC and the coverage was 300% or more.
  • polishing For the small roller for roller pitching test, the surface of the test piece was polished by 50 ⁇ m by polishing using a grindstone, and finished to a diameter of 26.0 mm.
  • Secondary shot peening Secondary (fine particle) shot peening was performed using a projection material having a particle size of 300 ⁇ m and an average hardness of 800 HV so that the arc height was 0.2 mmA and the coverage was 300% or more.
  • the surface hardness, compressive residual stress, surface fatigue strength, and bending fatigue strength of each test piece subjected to the above treatment were measured by the following methods.
  • the surface Vickers hardness was measured based on “Vickers hardness test-test method” in JIS Z 2244 (2003) using the small roller for roller pitching test subjected to the above treatment. Specifically, the test portion of the small roller is cut by a plane perpendicular to the axial direction of the small roller, the cut surface is mirror-polished, and the test force is 1 at a depth of 25 ⁇ m from the surface of the test portion. .961N was measured at 10 points, and the arithmetic average value was defined as the surface Vickers hardness.
  • the compression residual stress in each depth position was measured by X-ray using the small roller for roller pitching test which performed said process. Specifically, using a Position-Sensitive Proportional Counter (PSPC) micro-part X-ray stress measurement apparatus, electrolysis is performed from the test part surface of the small roller to positions of 0 ⁇ m (surface), 10 ⁇ m, 25 ⁇ m, 50 ⁇ m, 100 ⁇ m, and 200 ⁇ m, respectively. The residual stress was measured after polishing.
  • the measurement conditions of the PSPC minute part X-ray stress measurement apparatus are collimator diameter: ⁇ 1 mm, measurement site: axial center position, measurement direction: circumferential direction.
  • the surface fatigue strength was measured by performing a roller pitching test with an “RP-201 type” roller pitching tester (manufactured by Komatsu Engineering Co., Ltd.). Specifically, the roller pitching test was performed using the small roller and the large roller for the roller pitching test, which were subjected to the above treatment, under the conditions of an oil for automatic as a lubricating oil, an oil temperature of 120 ° C., and a slip ratio of ⁇ 40%. An S-repetition number N diagram was prepared, and the pitching strength (surface fatigue strength) was evaluated by the strength of 10 million times (meaning the maximum stress that does not break when tested 10 million times).
  • the strength exceeding 4.0 GPa is not measured in consideration of the load on the testing machine.
  • the surface fatigue strength obtained in this way is 3.6 GPa or more [about 1.7 times higher than steel type A in Table 1 (SCR420H equivalent steel of conventional steel)]. The fatigue strength was evaluated as excellent.
  • No. in Table 3 Nos. 2 to 11 and 18 are examples manufactured using the steel types shown in Table 1 that satisfy the requirements of the embodiment of the present invention under the conditions of the embodiment of the present invention, and are excellent in both surface fatigue strength and bending fatigue strength. .
  • No. No. 12 is an example using the steel type L of Table 1 with a small amount of C and Si and no Mo, and the surface fatigue strength was lowered.
  • No. No. 13 is an example using the steel type M of Table 1 with a small amount of Mn, a large amount of S, and no Mo, and since no cracks occurred during the test, no measurement was performed (each of the values in Table 3). Items"-").
  • No. 14 is an example using the steel type N of Table 1 with a large amount of P, and the surface fatigue strength and the bending fatigue strength decreased.
  • No. 15 is an example using the steel type O of Table 1 with a small amount of Cr, and the surface fatigue strength was lowered.
  • No. 16 is an example using the steel type P of Table 1 with a small amount of Mo, and the surface fatigue strength decreased.
  • No. No. 17 is an example using the steel type Q in Table 1 with a large amount of N, and cracking occurred during the test, and thus no measurement was performed (each item in Table 3 is “ ⁇ ”).
  • No. Nos. 19 to 23 are examples in which the steel type R in Table 1 that satisfies the requirements of the embodiment of the present invention was used, but was manufactured under conditions that did not satisfy the requirements of the embodiment of the present invention.
  • No. 19 is an example in which carburizing was performed instead of carbonitriding, and the surface hardness decreased.
  • No. No. 20 is an example in which the first shot peening was not performed, and the internal compressive residual stress was lowered, and thus the surface fatigue strength was lowered.
  • No. No. 21 is an example in which the second shot peening was not performed, and since the surface compressive residual stress was reduced, both the surface fatigue strength and the bending fatigue strength were reduced.
  • No. No. 22 was an example in which shot peening was not performed at all, and both the internal compressive residual stress and the surface compressive residual stress were reduced, and both the surface fatigue strength and the bending fatigue strength were reduced.
  • No. No. 23 is an example in which the second shot peening was performed without polishing after the first shot peening, and the surface roughness Rz increased and the surface fatigue strength decreased.
  • a carbonitriding component having a carbonitriding layer on the surface of a steel material The steel material is mass%, C: 0.15-0.25%, Si: 0.4-1%, Mn: 0.30 to 0.6%, P: more than 0%, 0.020% or less, S: more than 0%, 0.02% or less, Cr: 1.2-2%, Mo: 0.3 to 0.5%, N: more than 0% and 0.015% or less, with the balance consisting of iron and inevitable impurities,
  • the carbonitriding layer is Hardness at a depth of 25 ⁇ m from the surface is 850 HV or more, The absolute value of the compressive residual stress value at a depth of 200 ⁇ m from the surface is 200 MPa or more, The absolute value of the maximum compressive residual stress value from the surface to the 200 ⁇ m depth position is 850 MPa or more,
  • the steel material is further in mass%, V: more than 0%, 0.5% or less, Ti: more than 0%, 0.5% or less,
  • the steel material is further in mass%, Cu: more than 0%, 0.3% or less,
  • the carbonitrided part according to aspect 1 or 2 comprising at least one element selected from the group consisting of Ni: more than 0% and not more than 0.3%, and B: more than 0% and not more than 0.01%.

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  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
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  • Heat Treatment Of Articles (AREA)
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Abstract

Un mode de réalisation de la présente invention concerne un composant carbonitruré qui comporte une couche carbonitrurée sur la surface d'un matériau d'acier, le matériau d'acier contenant un ingrédient prédéterminé, et la couche carbonitrurée ayant une dureté de 850 HV ou plus à une profondeur de 25 µm depuis sa surface, la valeur absolue de la contrainte résiduelle de compression de cette dernière à une profondeur de 200 µm depuis sa surface étant supérieure ou égale à 200 MPa, la valeur absolue de la contrainte résiduelle de compression maximale à une profondeur de 200 µm depuis sa surface étant supérieure ou égale à 850 MPa et la rugosité moyenne sur dix points Rz spécifiée par la norme JIS B0601 (1994) de cette dernière étant inférieure ou égale à 2,5 µm.
PCT/JP2017/012621 2016-03-30 2017-03-28 Composant carbonitruré ayant une excellente résistance à la fatigue de surface et une excellente résistance à la fatigue en flexion, et procédé pour le fabriquer WO2017170540A1 (fr)

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WO2019097275A1 (fr) * 2017-11-15 2019-05-23 Arcelormittal Procédé de traitement d'une piece de coupe et équipement associé
JP7264117B2 (ja) * 2019-06-27 2023-04-25 Ｊｆｅスチール株式会社 鋼部品およびその製造方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002121644A (ja) * 2000-10-16 2002-04-26 Nippon Steel Corp 歯元疲労寿命及び接触疲労寿命強度に優れた歯車
JP2002327237A (ja) * 2001-04-27 2002-11-15 Nippon Steel Corp 歯元寿命及び接触疲労寿命強度に優れた歯車とその製造方法
JP2007262470A (ja) * 2006-03-28 2007-10-11 Aichi Steel Works Ltd ベルト式ｃｖｔ用プーリー
JP2009249700A (ja) * 2008-04-08 2009-10-29 Kobe Steel Ltd 曲げ疲労強度に優れた鋼部品、及びその製造方法
JP2012017499A (ja) * 2010-07-08 2012-01-26 Jfe Bars & Shapes Corp 疲労強度に優れた歯車およびその製造方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002121644A (ja) * 2000-10-16 2002-04-26 Nippon Steel Corp 歯元疲労寿命及び接触疲労寿命強度に優れた歯車
JP2002327237A (ja) * 2001-04-27 2002-11-15 Nippon Steel Corp 歯元寿命及び接触疲労寿命強度に優れた歯車とその製造方法
JP2007262470A (ja) * 2006-03-28 2007-10-11 Aichi Steel Works Ltd ベルト式ｃｖｔ用プーリー
JP2009249700A (ja) * 2008-04-08 2009-10-29 Kobe Steel Ltd 曲げ疲労強度に優れた鋼部品、及びその製造方法
JP2012017499A (ja) * 2010-07-08 2012-01-26 Jfe Bars & Shapes Corp 疲労強度に優れた歯車およびその製造方法

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