WO2012105405A1 - 窒化用鋼および窒化部品 - Google Patents
窒化用鋼および窒化部品 Download PDFInfo
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- WO2012105405A1 WO2012105405A1 PCT/JP2012/051650 JP2012051650W WO2012105405A1 WO 2012105405 A1 WO2012105405 A1 WO 2012105405A1 JP 2012051650 W JP2012051650 W JP 2012051650W WO 2012105405 A1 WO2012105405 A1 WO 2012105405A1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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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
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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
- 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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/24—Nitriding
- C23C8/26—Nitriding of ferrous surfaces
Definitions
- the present invention relates to a nitriding steel and a nitrided component (hereinafter referred to as “nitrided component”). Specifically, it is easy to cut before nitriding, has high bending fatigue strength and surface fatigue strength after nitriding, and can also suppress expansion (heat treatment deformation) due to nitriding, and can be used as a material for nitride parts such as automotive ring gears.
- the present invention relates to a suitable nitriding steel and nitrided parts thereof.
- Parts used in automobile transmissions are usually subjected to surface hardening treatment such as carburizing quenching, induction quenching and nitriding from the viewpoint of improving bending fatigue strength and surface fatigue strength.
- “carburizing and quenching” is a treatment in which low carbon steel is generally used, C is intruded and diffused in a high temperature austenite region of Ac 3 points or higher, and then quenched.
- C is intruded and diffused in a high temperature austenite region of Ac 3 points or higher, and then quenched.
- the heat treatment deformation becomes large because the treatment involves transformation. Therefore, when high part accuracy is required, finishing such as grinding and honing after carburizing and quenching is required.
- a so-called “carburized abnormal layer” such as a grain boundary oxide layer or an incompletely hardened layer formed on the surface layer becomes a fracture starting point such as bending fatigue, and there is a problem that the fatigue strength is lowered.
- “Induction hardening” is a process of quenching by rapid heating and cooling in a high temperature austenite region of Ac 3 points or higher. Although there is an advantage that adjustment of the depth of the hardened layer is relatively easy, it is not a surface hardening treatment in which C enters and diffuses like carburization. For this reason, in order to obtain the required surface hardness, hardened layer depth, and core hardness, it is common to use medium carbon steel having a higher C content than carburizing steel. However, since the medium carbon steel has a higher material hardness than the low carbon steel, there is a problem that machinability is lowered. There is also a problem that it is necessary to produce a high-frequency heating coil for each component.
- Nonriding is a process for obtaining a high surface hardness and an appropriate hardened layer depth by invading and diffusing N at a temperature of 450 to 650 ° C. below Ac 1 point. Since the treatment temperature is lower than that of carburizing and induction hardening, nitriding has an advantage that deformation of the heat treatment is small even when oil-cooled, for example.
- “soft nitriding” is a process for obtaining high surface hardness by invading and diffusing N and C at a temperature of about 500 to 600 ° C., which is less than Ac 1 point.
- the processing time is as short as several hours as compared with the case where only N penetrates and diffuses, the processing is suitable for mass production.
- nitriding is a treatment that does not perform quenching treatment from a high temperature austenite region, strengthening with martensitic transformation cannot be utilized. Therefore, it is necessary to increase the hardness before nitriding in order to ensure the desired strength of the nitrided part. However, if the hardness is increased by containing a large amount of alloy elements, cutting becomes difficult.
- SACM645 Aluminum chromium molybdenum steel (SACM645) specified in JIS G 4053 (2008), which is a typical nitriding steel, has high surface hardness because Cr, Al, etc. generate nitrides near the surface. be able to. However, since the hardened layer is shallow, high surface fatigue strength cannot be ensured. On the other hand, if the surface hardness is too high, the aggression on the mating gear becomes high.
- Mo is an element that combines with C in steel at a nitriding temperature to form carbides and improves the core hardness after nitriding.
- Mo is an expensive element, it is economically undesirable to use a large amount.
- nitriding is less heat treatment deformation than carburizing and induction hardening
- a large amount of alloy nitride is formed by nitriding when an alloying element is included in the nitrided part to ensure a desired strength.
- the surface of the nitrided part expands. For this reason, even with nitriding, the heat treatment deformation becomes large.
- ring gears for automobiles are machined into a thin final shape and nitridized after gear cutting, even a slight heat treatment deformation causes a problem.
- Patent Document 1 As materials for nitride parts, for example, techniques of Patent Document 1 and Patent Document 2 have been proposed.
- Patent Document 1 in mass%, C: 0.10 to 0.40%, Si: 0.50% or less, Mn: 0.30 to 1.50%, Cr: 0.30 to 2.00 %, V: more than 0.15 to 0.50%, Al: 0.02 to 0.50%, if necessary, Ni: 2.00% or less, Mo: 0.50% or less, S: 0.20% or less, Bi: 0.30% or less, Se: 0.30% or less, Ca: 0.10% or less, Te: 0.30% or less, Nb: 0.50% or less, and Ti: 1 type or 2 or more types of 1.00% or less are contained, the balance is made of Fe and impurity elements, and the ferrite hardness is made of ferrite pearlite structure of HV190 or more. “Nitride component material” and “nitride component manufacturing method” using the material are disclosed. There.
- Patent Document 2 by mass%, C: 0.10 to 0.40%, Si: 0.50% or less, Mn: 0.30 to less than 1.50%, Cr: 0.30 to 2.00% Al: 0.02 to 0.50%, if necessary, Ni: 2.00% or less, Mo: 0.50% or less, S: 0.20% or less, Bi: 0.30 %, Se: 0.30% or less, Ca: 0.10% or less, Te: 0.30% or less, Nb: 0.50% or less, Ti: 1.00% or less, and V: 0.50% or less
- a material for nitrided parts excellent in broachability characterized by comprising one or more of the above, the balance being Fe and impurity elements, and a bainite structure having a hardness of HV210 or more, and A “nitriding component manufacturing method” using the material is disclosed.
- the ferrite hardness before nitriding treatment is Vickers hardness (hereinafter, “Vickers hardness” is referred to as “HV”).
- Vickers hardness is referred to as “HV”.
- HV Vickers hardness
- the bainite hardness before nitriding treatment is as high as 218 or more in terms of Vickers hardness, as shown in the examples, and the coverage is high when the cutting speed is high. It is hard to say that machinability is good.
- An object of the present invention is to provide a nitriding steel and a nitrided part suitable for use as a material for a nitrided part, which have high bending fatigue strength and surface fatigue strength after nitriding and can also suppress expansion (heat treatment deformation) due to nitriding. .
- the present invention has been completed based on the above knowledge, and the gist thereof is in the nitriding steel shown in the following (1) and (2) and the nitrided part shown in (3).
- Fn1 0.61Mn + 1.11Cr + 0.35Mo + 0.47V (1)
- the element symbol in the formula (1) represents the content in mass% of the element.
- nitriding includes not only the process of invading and diffusing only N but also “soft nitriding” which is the process of invading and diffusing N and C. That is, “nitriding” in the present invention includes not only “2411 nitriding” defined in JIS B 6905 (1995) but also “2421 soft nitriding”.
- impurities in “Fe and impurities” as the balance refers to those mixed from ore, scrap, or production environment as raw materials when industrially producing steel materials.
- “Surface hardness” refers to any 10 points at a depth of 0.03 mm from the surface of the test piece in accordance with “Vickers hardness test-test method” described in JIS Z 2244 (2009).
- the Vickers hardness at is an arithmetic average value of values measured by a Vickers hardness tester with a test force of 0.98 N.
- Effective hardened layer depth was determined using a distribution map of Vickers hardness (that is, a transition curve of Vickers hardness) measured at a predetermined interval from the surface of the test piece with a test force of 1.96 N. , Refers to the distance from the surface to a position where the Vickers hardness is 420.
- the steel for nitriding of the present invention is easy to cut before nitriding and has a small expansion due to nitriding. Moreover, the nitrided parts made of this steel have high bending fatigue strength and surface fatigue strength despite the fact that the content of Mo, which is an expensive element, is less than 0.05% by mass. Yes.
- the unit of the dimension in the figure is “mm”. It is a figure which shows the rough shape as cut out from the steel bar of the Ono-type rotary bending fatigue test piece with a notch used in the Example. The unit of the dimension in the figure is “mm”. It is a figure which shows the rough shape as cut out from the bar steel of the roller pitching small roller test piece used in the Example. The unit of the dimension in the figure is “mm”. It is a figure which shows the rough shape as cut out from the steel bar of the roller pitching large roller test piece used in the Example. In FIG.
- FIG. 4 is a diagram showing a heat pattern of “gas soft nitriding” performed on the test pieces shown in FIGS. 1 to 3 made of steels 1 to 12 and subsequent cooling in Examples.
- FIG. 4 is a diagram showing a heat pattern of “carburization quenching-tempering” performed on the test pieces shown in FIGS. In an Example, it is a figure which shows the heat pattern of the "carburization hardening-tempering" performed to the test piece shown in FIG. 4 which uses the steel 13 as a raw material.
- FIG. 11 shows the state before “gas soft nitriding” or “carburizing”, and (b) shows the state after “gas soft nitriding” and oil cooling or after “carburizing quenching-tempering”. Shows the state.
- Si 0.10 to 0.30% Si has a deoxidizing action. In order to obtain this effect, a Si content of 0.10% or more is necessary. However, if the Si content increases and exceeds 0.30%, the hardness before nitriding increases and the machinability decreases. Therefore, the Si content is set to 0.10 to 0.30%.
- the Si content is preferably 0.12% or more, and more preferably 0.25% or less.
- Mn 0.4 to 1.0%
- Mn has an effect of ensuring bending fatigue strength and surface fatigue strength of nitrided parts, and a deoxidizing action. In order to obtain these effects, a Mn content of 0.4% or more is necessary. However, if the Mn content increases and exceeds 1.0%, the hardness before nitriding becomes too high, and the machinability deteriorates. Therefore, the Mn content is set to 0.4 to 1.0%. In order to ensure the strength of the nitrided part more stably, the Mn content is preferably 0.5% or more. When the machinability is more important, the Mn content is preferably 0.6% or less.
- S 0.005 to 0.030%
- S combines with Mn to form MnS and has the effect of improving machinability.
- the S content is set to 0.005 to 0.030%.
- the S content is preferably set to 0.010% or more.
- the S content is preferably 0.025% or less.
- Cr 1.0 to 1.5% Cr increases the surface hardness and the core hardness in nitriding, and has the effect of ensuring the bending fatigue strength and surface fatigue strength of the component. However, if the Cr content is less than 1.0%, the above effect cannot be obtained. On the other hand, if the Cr content increases and exceeds 1.5%, the hardness before nitriding increases and the machinability decreases. Therefore, the Cr content is set to 1.0 to 1.5%. In order to increase the surface hardness and core hardness in nitriding more stably, the Cr content is preferably 1.1% or more. When the machinability is more important, the Cr content is preferably 1.4% or less.
- Mo 0.05% or less (including 0%) Mo may not be contained.
- Mo When Mo is contained, Mo combines with C in the steel at the nitriding temperature to form a carbide, so that the core hardness after nitriding is improved.
- the Mo content when the Mo content increases and exceeds 0.05%, not only the raw material cost increases, but also the hardness before nitriding increases and the machinability decreases. Therefore, the Mo content is set to 0.05% or less.
- the Mo content is preferably set to 0.03% or less.
- Al 0.010% or more and less than 0.10%
- Al has a deoxidizing action. Further, Al combines with N that penetrates and diffuses from the surface during nitriding to form AlN, and has the effect of improving the surface hardness. In order to obtain these effects, it is necessary to contain 0.010% or more of Al.
- the Al content increases to 0.10% or more, not only the hard Al 2 O 3 is formed and the machinability is lowered, but also the hardened layer by nitriding becomes shallow and bending fatigue strength or The problem that surface fatigue strength falls arises. Therefore, the Al content is set to 0.010% or more and less than 0.10%.
- the minimum with preferable Al content is 0.020%, and a preferable upper limit is 0.070%.
- V 0.10 to 0.25%
- V like Mo, combines with C in steel at the nitriding temperature to form carbides, and has the effect of improving the core hardness after nitriding.
- V also has a function of improving the surface hardness by combining with N and / or C entering and diffusing from the surface during nitriding to form nitride and / or carbonitride.
- it is necessary to contain 0.10% or more of V.
- the content of V is set to 0.10 to 0.25%.
- the V content is preferably 0.15% or more, and preferably 0.20% or less.
- Fn1 2.30 or less
- An alloy element having a strong affinity for nitrogen combines with nitrogen during nitriding to generate alloy nitride in the surface layer portion. Since the alloy nitride distorts the crystal lattice, the surface of the part expands to cause heat treatment deformation. In particular, since Mn, Cr, Mo, and V tend to precipitate alloy nitrides on the surface layer portion, expansion (heat treatment deformation) due to nitriding may not be suppressed even if the content of these elements is in the above-described range. is there.
- the amount of Mn, Cr, Mo, and V is within the above-described range, and the above Fn1 is 2.30 or less.
- Fn1 is preferably 1.50 or more and preferably 2.20 or less.
- One of the nitriding steels of the present invention includes the above elements, the balance being Fe and impurities, and P, N, Ti and O in the impurities are each P: 0.030% or less, N: 0.008 % Or less, Ti: 0.005% or less, and O: 0.0030% or less.
- P 0.030% or less
- P is an impurity contained in the steel and segregates at the grain boundaries to embrittle the steel.
- the content of P in the impurities is set to 0.030% or less.
- content of P in an impurity shall be 0.020% or less.
- N in steel is easy to form carbonitride by combining with elements such as C and V, and when carbonitride such as VCN is formed before nitriding, the hardness becomes high,
- N is an undesirable element because machinability is reduced.
- the carbonitride has a high solid solution temperature, it becomes difficult for V to be dissolved in the matrix by hot forging and subsequent heating in the normalization.
- the content of N in the impurities is set to 0.008% or less.
- the preferable content of N in the impurities is 0.006% or less.
- Ti 0.005% or less Ti has a high affinity with N, and is easily combined with N in steel to produce TiN which is a hard nitride.
- the content of Ti in the impurities is set to 0.005% or less.
- the preferable content of Ti in the impurities is 0.003% or less.
- O forms oxide inclusions that cause fatigue failure starting from inclusions, and decreases bending fatigue strength and surface fatigue strength.
- the content of O in the impurities is set to 0.0030% or less.
- the preferable content of O in the impurities is 0.0020% or less.
- impurities refer to those mixed from ore, scrap, or the production environment as raw materials when industrially producing steel materials.
- Another one of the nitriding steels according to the present invention contains one or more elements of Cu and Ni instead of a part of Fe.
- Cu 0.30% or less Cu has an action of improving the core hardness, so that Cu may be contained in order to obtain this effect.
- an upper limit is set for the Cu content in the case of inclusion, and it is set to 0.30% or less.
- the content of Cu is preferably 0.20% or less.
- the content of Cu when contained is preferably 0.10% or more, and more preferably 0.15% or more.
- Ni 0.25% or less Since Ni has an action of improving the core hardness, Ni may be included to obtain this effect. However, if the Ni content increases, the machinability decreases. Therefore, an upper limit is set for the Ni content in the case of inclusion, and the content is made 0.25% or less. When Ni is contained, the content of Ni is preferably 0.20% or less.
- the Ni content when contained is preferably 0.05% or more, and more preferably 0.10% or more.
- the above Cu and Ni can be contained in only one of them or in a composite of two.
- the total content of these elements may be 0.55% or less, but is preferably 0.50% or less.
- Nitrided parts that is, parts subjected to nitridation, have low surface hardness, but bending fatigue strength, surface fatigue strength, and wear resistance are reduced. If the HV is 650 or more, the nitrided part can have a desired strength. On the other hand, when the surface hardness increases, particularly when the HV exceeds 900, the aggression against the mating gear increases. Therefore, the nitrided part has a surface hardness of 650 to 900 in HV. In addition, the preferable minimum of surface hardness is 700 in HV, and a preferable upper limit is 800 in HV.
- the upper limit of the core hardness is not particularly required, but the upper limit of the core hardness that can be reached when the nitriding steel of the present invention is nitrided without quenching is about 250 in HV.
- the upper limit of the effective hardened layer depth does not need to be specified in particular, but in order to increase the effective hardened layer depth, it is necessary to lengthen the nitriding treatment time, resulting in an increase in cost. Therefore, the effective hardened layer depth is preferably 0.50 mm or less, and more preferably 0.45 mm or less.
- (E) Manufacturing method of nitrided part
- the nitrided part of the present invention is processed and heat-treated using steel having the chemical composition described in the above section (A) under the following conditions, for example, to perform nitriding treatment. Can be manufactured.
- the nitrided part of the present invention may be manufactured by cutting with hot forging and performing nitriding treatment. However, if normalization is performed as necessary, the crystal grains can be made finer. can do. In this case, the normalizing treatment is preferably performed at a temperature of 850 to 970 ° C.
- the lower limit of the cooling rate is preferably 0.5 ° C./second, and the upper limit is 5 ° C./second. It is preferable.
- the nitriding treatment method for obtaining the nitrided part of the present invention is not particularly defined, and gas nitriding treatment, salt bath nitriding treatment, ion nitriding treatment, etc. can be used.
- the nitriding treatment temperature is preferably 500 to 650 ° C. If the soft-nitriding, for example a combination of RX gas in addition to NH 3, NH 3 and RX gas 1: processing may be performed in one of an atmosphere.
- the treatment time varies depending on the treatment temperature, the desired surface hardness, core hardness and effective hardened layer depth can be obtained in 9 hours when the soft nitriding treatment is performed at 560 ° C.
- the cooling after the nitriding treatment may be performed by an appropriate method such as in-furnace cooling or oil cooling.
- Steels 1 to 13 having the chemical composition shown in Table 1 were melted by a vacuum melting furnace, an atmospheric melting furnace or a converter to produce an ingot or slab.
- steels 1 to 9 steel 11 and steel 12 were melted in a 180 kg vacuum melting furnace and then ingoted to produce ingots.
- Steel 13 was melted by a 70-ton converter and then continuously cast to produce a slab.
- Steels 1 to 5 in Table 1 are steels according to examples of the present invention whose chemical compositions are within the range defined by the present invention, while Steels 6 to 13 are those from which the chemical composition is defined by the present invention. It is steel of the comparative example which has come off.
- Steel 13 is steel corresponding to SCr420H defined in JIS G 4052 (2008).
- the steel 1-12 ingots were homogenized by holding at 1250 ° C. for 5 hours, then heated to 1200 ° C. and hot forged to have diameters of 25 mm, 35 mm, and 60 mm, respectively. Steel bars with a length of 1000 mm were produced.
- the steel 13 slab was heated at 1250 ° C. for 3 hours to be rolled into a steel slab, then heated to 1200 ° C. to perform hot forging, and the diameters were 25 mm and 35 mm, respectively. , 60 mm and 140 mm, both of which were 1000 mm long steel bars.
- steels 3 to 13 having a diameter of 25 mm, a diameter of 35 mm, and a diameter of 60 mm were subjected to “normalization” in which they were kept at 920 ° C. for 1 hour and then air-cooled.
- the steel bar 140 having a diameter of 140 mm was subjected to “normalization” in which it was kept at 900 ° C. for 4 hours and then allowed to cool.
- a steel bar having a diameter of 25 mm is cut so-called “crossing”, that is, perpendicular to the axial direction (length direction), and embedded in the resin so that the cut surface becomes the test surface.
- the sample was polished so that the cut surface had a mirror finish, and used as a Vickers hardness test piece and a microstructure observation sample as hot forged or after normalization.
- a turning test piece having a diameter of 50 mm and a length of 490 mm was taken from a steel bar having a diameter of 60 mm.
- the test piece for measuring the amount of expansion shown in FIG. 1 and the Ono-type rotary bending fatigue test piece with a rough notch shown in FIG. 2 were cut out in parallel to the axial direction.
- a coarse roller pitching small roller test piece shown in FIG. 3 was cut out in parallel with the axial direction from the center of a steel bar having a diameter of 35 mm.
- FIG. 4 a coarse roller pitching large roller test piece shown in FIG. 4 was cut out in parallel with the axial direction from the center of a steel bar having a diameter of 140 mm.
- FIG. 4 (a) is a front view when a coarse roller pitching large roller test piece is halved by the center line, and (b) is a cross-sectional view at the center line.
- the unit of the dimension in each of the above cut-out test pieces shown in FIGS. 1 to 4 is “mm”.
- the three types of finishing symbols in the figure are “triangular symbols” indicating the surface roughness described in the explanatory table 1 of JIS B 0601 (1982).
- G attached to the finish symbol means an abbreviation of a processing method indicating “grinding” defined in JIS B 0122 (1978).
- the heat pattern shown in FIG. 5 was applied to the Ono-type rotating bending fatigue test piece with a rough shape of steel 1 to 12 and the coarse roller pitching small roller test piece.
- “Gas soft nitriding” and “oil cooling” (hereinafter referred to as “gas soft nitriding / oil cooling”) were performed. Note that “120 ° C. oil cooling” indicates that the oil was cooled in oil at an oil temperature of 120 ° C.
- the ono-type rotating bending fatigue test piece with a rough notch of steel 13 and the roller-pitting small roller test piece with a rough shape were subjected to “carburization quenching and tempering” by the heat pattern shown in FIG. Note that “Cp” in FIG. 6 represents a carbon potential.
- “120 ° C. oil quenching” indicates that it was put into an oil having an oil temperature of 120 ° C. and quenching, and “AC” represents air cooling.
- test piece for measuring the amount of expansion of the steel 13 was indented with a Vickers hardness tester at a total of 32 locations as described later, and then subjected to “carburization quenching and tempering” with the heat pattern shown in FIG. .
- FIG. 10 (a) is a front view when a roller pitching large roller test piece is halved by a center line, and (b) is a cross-sectional view at the center line.
- the unit of dimensions in each of the above-mentioned test pieces shown in FIGS. 8 to 10 is “mm”.
- the two types of finishing symbols in the above figures are “triangular symbols” indicating the surface roughness described in the explanatory table 1 of JIS B 0601 (1982), respectively, as in FIGS.
- G attached to the finish symbol means an abbreviation of a processing method indicating “grinding” defined in JIS B 0122 (1978).
- ⁇ is a “waveform symbol”, which means that it is a dough, that is, it remains the above-mentioned “gas soft nitriding / oil cooling” or “carburization quenching-tempering” surface.
- ⁇ 1 Vickers hardness test as hot forged or after normalization
- R R / 2 part
- ⁇ 2 Microstructure observation as hot forged or after normalization
- Microstructure observation sample as hot forged or after normalization is corroded with nital, and the magnification is set to 400 times with an optical microscope. Two parts were observed.
- the microstructure was either bainite, a two-phase mixed structure composed of ferrite and bainite, a two-phase mixed structure composed of ferrite and pearlite, or a three-phase mixed structure composed of ferrite, pearlite and bainite.
- the chip when turning is also evaluated, and when the chip is divided into small pieces and there is no problem such as ⁇ wrapping '' around the material under test, the chip is treated with a good chip treatment. A case where a problem of wrapping around the material occurred was defined as “poor chip disposal”.
- FIG. 11 (a) the reference surface of the expansion specimen shown in FIG. A total of 32 locations of position numbers 1A to 16A having a depth of 50 ⁇ m and intervals of 200 ⁇ m, and 16 locations of position numbers 1B to 16B having a distance of 200 ⁇ m at a position 200 ⁇ m deeper than the position numbers.
- An indentation was provided at a location with a test force of 0.98 N using a Vickers hardness tester.
- FIG. 11 only the position numbers “1 to 16” are displayed, and the symbols “A” and “B” indicating the depth position are omitted.
- test pieces provided with the indentations of steels 1 to 12 were subjected to “gas soft nitriding / oil cooling” according to the heat pattern shown in FIG. “Carburization quenching and tempering” by the heat pattern shown in FIG. 6 was performed.
- the position number nA and the position number nB (where n represents an integer of 1 to 16) for each test piece.
- the distance d (n) between the 16 indentations provided was measured.
- the distance d (n) between the indentations was measured after lightly buffing the investigation surface.
- the amount of expansion is [ ⁇ (D (1) + d (2) +... + D (16) ⁇ ⁇ 16 ⁇ 200] / 16 Calculated by
- ⁇ 5 Measurement of surface hardness, core hardness and effective hardened layer depth after “gas soft nitriding / oil cooling” or “carburizing quenching-tempering” “gas soft nitriding / oil cooling” or “carburizing firing”
- the roller pitching small roller test piece before the finishing process after “entry-tempering” the part having a diameter of 26 mm is crossed and embedded in the resin so that the cut surface becomes the test surface. It grind
- HV at any 10 points at a depth of 0.03 mm from the surface of the test piece is The test force was set to 0.98 N and measured with a Vickers hardness tester, and the value was arithmetically averaged to obtain “surface hardness”.
- HV at any 10 points at a depth of 2 mm from the surface of the test piece was measured with a Vickers hardness tester with a test force of 1.96 N. The values were arithmetically averaged to obtain “core hardness”.
- the test force is set to 1.96 N with a Vickers hardness tester, and HV is measured at a predetermined interval. An HV distribution map was prepared. And the distance from the surface to the position which becomes 420 by HV was made into the "effective hardened layer depth.”
- Bending fatigue strength is superior when it has a rotational bending fatigue strength equal to or greater than that of test number 13 "carburized and tempered” using steel 13 corresponding to SCr420H specified in JIS G 4052 (2008). It was.
- ⁇ 7 Roller Pitching Test Using a finished roller pitching small roller test piece and roller pitching large roller test piece, a roller pitching test was performed under the following test conditions, and pitching with a major axis of 1 mm or more occurred. When the lifetime was measured. The above test was performed 3 times, and the average life of 3 times was defined as “pitching life”. The maximum number of repetitions evaluated was 1 ⁇ 10 7 times.
- ⁇ Slip rate 40% ⁇ Surface pressure: 1600 MPa, -Number of rotations of small roller test piece: 1000 rpm, ⁇ Lubrication: Lubricating oil for automatic transmission with an oil temperature of 100 ° C. was jetted at a rate of 2 liters / minute to the contact portion between the roller pitching small roller test piece and the roller pitching large roller test piece.
- slip rate is a value calculated by the following formula, where “V1” is the tangential speed of the roller pitching small roller test piece surface and “V2” is the tangential speed of the roller pitching large roller test piece surface. Point to. ⁇ (V2-V1) / V1 ⁇ ⁇ 100.
- Table 2 summarizes the results of each investigation conducted using test specimens collected from the hot forged state or test specimens collected after “normalization”.
- “B”, “F”, and “P” in the “Microstructure” column of Table 2 mean bainite, ferrite, and pearlite, respectively.
- “ ⁇ ” and “ ⁇ ” in the “Chip Disposability” column indicate that the chip was divided into small pieces, and there was no problem such as “wrapping” around the material under test, and “Chip Disposability” was good. In addition, it indicates that the problem that the chips are wound around the material to be tested for a long time is “chip processing property is poor”.
- Table 3 summarizes the results of tests conducted using test pieces that were finished after “gas soft nitriding / oil cooling” or “carburization quenching-tempering”.
- the expansion amount due to nitriding is as large as 2.6 ⁇ m.
- test number 10 since the content of Ti, N and O of the steel 10 used is larger than the value specified in the present invention, the bending fatigue strength is 420 MPa, the pitching life is 5.8 ⁇ 10 6 times, It is inferior compared with the case of test number 13 using steel 13. Moreover, since content of N is higher than the value prescribed
- test number 11 since the V content of the steel 11 used is less than the value specified in the present invention, the rotational bending fatigue strength and the pitching life are 400 MPa and 6.1 ⁇ 10 6 times, respectively. It is inferior to the case of test number 13 using 13.
- the nitriding steel of the present invention is easy to cut before nitriding, and the nitriding part made from this nitriding steel has an Mo content of 0.05% by mass as an expensive element. In spite of the following, it has high bending fatigue strength and surface fatigue strength. For this reason, the steel for nitriding of the present invention is suitable for use as a material for nitrided parts that require high bending fatigue strength and surface fatigue strength. Furthermore, since the nitriding steel of the present invention has a small expansion amount due to nitriding, it is optimal as a material for thin nitrided parts such as automobile ring gears.
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Abstract
Description
Fn1=0.61Mn+1.11Cr+0.35Mo+0.47V・・・(1)
ただし、(1)式中の元素記号は、その元素の質量%での含有量を表す。
C:0.07~0.14%
Cは、窒化部品の強度確保のために必須の元素であり、0.07%以上の含有量が必要である。しかしながら、Cの含有量が多くなって0.14%を超えると、窒化前の硬さが高くなって被削性の低下をきたす。このため、Cの含有量を0.07~0.14%とした。窒化部品の強度をより安定して確保するためには、Cの含有量は0.09%以上とすることが好ましい。また、被削性がより重視されるときには、Cの含有量は0.12%以下とすることが好ましい。
Siは、脱酸作用を有する。この効果を得るには、0.10%以上のSi含有量が必要である。しかしながら、Siの含有量が多くなって0.30%を超えると、窒化前の硬さが高くなって被削性が低下する。したがって、Siの含有量を0.10~0.30%とした。Siの含有量は0.12%以上とすることが好ましく、また0.25%以下とすることが好ましい。
Mnは、窒化部品の曲げ疲労強度および面疲労強度を確保する作用、ならびに脱酸作用を有する。これらの効果を得るには、0.4%以上のMn含有量が必要である。しかしながら、Mnの含有量が多くなって1.0%を超えると、窒化前の硬さが高くなりすぎて被削性が低下する。このため、Mnの含有量を0.4~1.0%とした。窒化部品の強度をより安定して確保するためには、Mnの含有量は0.5%以上とすることが好ましい。また、被削性がより重視されるときには、Mnの含有量は0.6%以下とすることが好ましい。
Sは、Mnと結合してMnSを形成し、被削性を向上させる作用がある。しかしながら、Sの含有量が0.005%未満では、前記の効果が得がたい。一方、Sの含有量が0.030%を超えると、粗大なMnSを形成して、熱間鍛造性および曲げ疲労強度が低下する。そのため、Sの含有量を0.005~0.030%とした。より安定して被削性を確保するためには、Sの含有量は0.010%以上とすることが好ましい。また、熱間鍛造性および曲げ疲労強度がより重視される場合には、Sの含有量は0.025%以下とすることが好ましい。
Crは、窒化での表面硬さおよび芯部硬さを高め、部品の曲げ疲労強度および面疲労強度を確保する作用を有する。しかしながら、Crの含有量が1.0%未満では前記の効果を得ることができない。一方、Crの含有量が多くなって1.5%を超えると、窒化前の硬さが高くなって被削性が低下する。したがって、Crの含有量を1.0~1.5%とした。窒化での表面硬さおよび芯部硬さをより安定して高めるためには、Crの含有量は1.1%以上とすることが好ましい。また、被削性がより重視されるときには、Crの含有量は1.4%以下とすることが好ましい。
Moは含有していなくともよい。Moを含有すると、Moが窒化温度で鋼中のCと結合して炭化物を形成するので、窒化後の芯部硬さが向上する。しかしながら、Moの含有量が多くなって0.05%を超えると、原料コストが高くなるだけでなく、窒化前の硬さが高くなって被削性が低下する。そのため、Moの含有量を0.05%以下とした。なお、被削性が重視される場合は、Moの含有量を0.03%以下とすることが好ましい。
Alは、脱酸作用を有する。またAlは、窒化時に表面から侵入・拡散するNと結合してAlNを形成し、表面硬さを向上させる作用を有する。これらの効果を得るには、Alを0.010%以上含有させる必要がある。しかしながら、Alの含有量が多くなって0.10%以上になると、硬質のAl2O3を形成して被削性が低下するばかりか、窒化での硬化層が浅くなって曲げ疲労強度や面疲労強度が低下する問題が生じる。そのため、Alの含有量を0.010%以上0.10%未満とした。Al含有量の好ましい下限は0.020%であり、また好ましい上限は0.070%である。
Vは、Moと同じく、窒化温度で鋼中のCと結合して炭化物を形成し、窒化後の芯部硬さを向上させる作用を有する。またVは、窒化時に表面から侵入・拡散するNおよび/またはCと結合して窒化物および/または炭窒化物を形成し、表面硬さを向上させる作用も有する。これらの効果を得るには0.10%以上のVを含有する必要がある。しかしながら、Vの含有量が多くなって0.25%を超えると、窒化前の硬さが高くなりすぎて被削性が低下するばかりか、熱間鍛造およびその後の焼準でマトリックス中にVが固溶しなくなるため、前記の効果が飽和する。そのため、Vの含有量を0.10~0.25%とした。Vの含有量は0.15%以上とすることが好ましく、また0.20%以下とすることが好ましい。
窒素と親和力が強い合金元素は、窒化時に窒素と結合して表層部に合金窒化物を生成する。合金窒化物は結晶格子をひずませるため、部品表面が膨張して熱処理変形を生じる。特に、Mn、Cr、MoおよびVは表層部に合金窒化物を析出しやすいので、これらの元素の含有量がたとえ上述した範囲にあっても、窒化による膨張(熱処理変形)を抑制できない場合がある。しかしながら、式中の元素記号をその元素の質量%での含有量として、
Fn1=0.61Mn+1.11Cr+0.35Mo+0.47V・・・(1)
の(1)式で表されるFn1が2.30以下であれば、窒化での過剰な合金窒化物の析出が抑制されるため、窒化での膨張量が小さくなって熱処理変形を抑制することができる。
Pは、鋼に含有される不純物であり、結晶粒界に偏析して鋼を脆化させ、特に、その含有量が0.030%を超えると、脆化の程度が著しくなる場合がある。したがって、本発明においては、不純物中のPの含有量を0.030%以下とした。なお、不純物中のPの含有量は0.020%以下とすることが好ましい。
鋼中のNは、CおよびVなどの元素と結合して炭窒化物を形成しやすく、窒化前にVCNなどの炭窒化物を形成すると硬さが高くなって、被削性が低下するため、本発明においてはNは好ましくない元素である。また、この炭窒化物は固溶温度が高いため、熱間鍛造およびその後の焼準での加熱でVがマトリックスに固溶しにくくなり、鋼中のN含有量が高いと窒化による前記Vの効果が十分に得られない。そのため、本発明においては、不純物中のNの含有量を0.008%以下とした。なお、不純物中のNの好ましい含有量は0.006%以下である。
Tiは、Nとの親和性が高く、鋼中のNと結び付いて硬質の窒化物であるTiNを生成しやすい。Tiの含有量が0.005%を超える場合には、生成した粗大なTiNが曲げ疲労強度および面疲労強度を低下させてしまう。したがって、本発明においては、不純物中のTiの含有量を0.005%以下とした。なお、不純物中のTiの好ましい含有量は0.003%以下である。
Oは、介在物起点の疲労破壊の原因となる酸化物系の介在物を形成して、曲げ疲労強度および面疲労強度を低下させてしまう。特に、Oの含有量が0.0030%を超えると、上記疲労強度の低下が著しくなる。そのため、本発明においては、不純物中のOの含有量を0.0030%以下とした。なお、不純物中のOの好ましい含有量は0.0020%以下である。
Cuは、芯部硬さを向上させる作用を有するので、この効果を得るためにCuを含有させてもよい。しかしながら、Cuの含有量が多くなると、被削性が低下する。したがって、含有させる場合のCuの含有量に上限を設け、0.30%以下とした。含有させる場合のCuの含有量は0.20%以下であることが好ましい。
Niは、芯部硬さを向上させる作用を有するので、この効果を得るためにNiを含有させてもよい。しかしながら、Niの含有量が多くなると、被削性が低下する。したがって、含有させる場合のNiの含有量に上限を設け、0.25%以下とした。含有させる場合のNiの含有量は0.20%以下であることが好ましい。
窒化部品、すなわち、窒化を施された部品は、その表面硬さが低いと、曲げ疲労強度、面疲労強度および耐摩耗性が低下してしまうが、表面硬さがHVで650以上であれば、窒化部品に所望の強度を具備させることができる。一方、表面硬さが高くなって、特に、HVで900を超えると、相手ギヤに対する攻撃性が高くなってしまう。したがって、窒化部品は、表面硬さがHVで650~900であることとした。なお、表面硬さの好ましい下限はHVで700であり、また、好ましい上限はHVで800である。
窒化部品の芯部硬さが低いと、負荷が加わった際に内部で塑性変形が生じ、内部で発生した亀裂によりピッチングが発生し、面疲労強度が低下してしまう。窒化部品で内部の塑性変形を抑制するには、HVで150以上の芯部硬さが必要である。そのため、本発明の窒化部品の芯部硬さはHVで150以上とした。芯部硬さの好ましい下限はHVで170である。
窒化部品の有効硬化層深さが浅いと、内部起点の破壊を引き起こし、曲げ疲労強度および面疲労強度を低下させてしまう。内部起点の破壊を抑制するためには、有効硬化層深さを0.15mm以上とする必要がある。そのため、本発明の窒化部品の有効硬化層深さは、0.15mm以上とした。有効硬化層深さの好ましい下限は0.20mmである。
本発明の窒化部品は、前記(A)項に記載の化学組成を有する鋼を用いて、例えば次のような条件で加工および熱処理し、窒化処理を行うことで製造することができる。
前記(A)項に記載の化学組成を有する鋼の鋼片、棒鋼等を切断した後、1000~1270℃に加熱して粗形状に熱間鍛造する。
本発明の窒化部品は、熱間鍛造のまま切削加工し、窒化処理を施して製造してもよいが、必要に応じて焼準を行えば結晶粒をより微細にすることができる。この場合、焼準処理は850~970℃の温度で行うことが好ましい。
焼準後の粗形品を、旋盤などで切削加工した後、ブローチ盤、ギヤシェイパーなどの加工機械によって窒化部品の形状に加工する。
本発明の窒化部品を得るための窒化処理方法は、特に規定されるものではなく、ガス窒化処理、塩浴窒化処理、イオン窒化処理等を用いることができる。窒化処理の処理温度は500~650℃が好ましい。軟窒化処理の場合には、例えばNH3に加えてRXガスを併用し、NH3とRXガスが1:1の雰囲気において処理を行えばよい。
熱間鍛造ままの、または焼準後の、ビッカース硬さ試験片の中心部1点とR/2部(「R」は棒鋼の半径を表す。)4点の計5点のHVを、JIS Z 2244(2009)に記載の「ビッカース硬さ試験-試験方法」に準拠して、試験力を9.8Nとしてビッカース硬さ試験機で測定し、5点の算術平均値を熱間鍛造ままの、または焼準後の、HVとした。
熱間鍛造ままの、または焼準後の、ミクロ組織観察試料をナイタルで腐食し、倍率を400倍として光学顕微鏡でR/2部を観察した。
旋削試験片を用いて、
・工具:超硬工具(材種記号:CA5525)、
・周速:360m/分、
・送り:0.4mm/rev、
・切込:1mm、
・潤滑剤:水溶性潤滑剤、
の条件で旋削試験を行った。なお、旋削加工時の切削抵抗を測定して、切削抵抗が750N以下である場合に、被削性が良好であると評価した。
まず、図11の(a)に示すように、図1に示す膨張量試験片の基準表面からの深さが50μmで各間隔が200μmである位置番号1A~16Aの16箇所および、上記各位置番号からさらに200μm深い位置で各間隔が200μmである位置番号1B~16Bの16箇所の総計32箇所に、ビッカース硬さ試験機を用いて、0.98Nの試験力で圧痕を設けた。なお、図11では位置番号である「1~16」のみを表示し、深さ位置を示す「A」と「B」の記号は省略した。
[{(d(1)+d(2)+・・・+d(16)}-16×200]/16
によって算出した。
「ガス軟窒化・油冷」または「浸炭焼入-焼戻し」後に仕上加工した試験前のローラーピッチング小ローラー試験片を用いて、その直径26mmの部分を横断し、切断面が被検面になるように樹脂に埋め込んだ後、前記面が鏡面仕上になるように研磨し、ビッカース硬さ試験機を使用して表面硬さ、芯部硬さおよび有効硬化層深さを調査した。
仕上加工した小野式回転曲げ疲労試験片を用いて、下記の試験条件によって小野式回転曲げ疲労試験を実施し、繰返し数が107回において破断しない最大の強度で「回転曲げ疲労強度」を評価した。
・雰囲気:大気中、
・回転数:3000rpm。
仕上加工したローラーピッチング小ローラー試験片およびローラーピッチング大ローラー試験片を用いて、下記の試験条件でローラーピッチング試験を実施し、長径が1mm以上の大きさのピッチングが発生したときの寿命を測定した。上記の試験を3回行なって、3回の平均寿命を「ピッチング寿命」とした。なお、評価した繰返し数は最大で1×107回とした。
・面圧:1600MPa、
・小ローラー試験片の回転数:1000rpm、
・潤滑:油温100℃のオートマチックトランスミッション用潤滑油を、2リットル/分の割合で、ローラーピッチング小ローラー試験片とローラーピッチング大ローラー試験片の接触部に噴出させて実施。
{(V2-V1)/V1}×100。
Claims (3)
- 質量%で、C:0.07~0.14%、Si:0.10~0.30%、Mn:0.4~1.0%、S:0.005~0.030%、Cr:1.0~1.5%、Mo:0.05%以下(0%を含む)、Al:0.010%以上0.10%未満およびV:0.10~0.25%を含有するとともに、下記の(1)式で表されるFn1が2.30以下であり、残部はFeおよび不純物からなり、不純物中のP、N、TiおよびOがそれぞれ、P:0.030%以下、N:0.008%以下、Ti:0.005%以下およびO:0.0030%以下である化学組成を有することを特徴とする窒化用鋼。
Fn1=0.61Mn+1.11Cr+0.35Mo+0.47V・・・(1)
ただし、(1)式中の元素記号は、その元素の質量%での含有量を表す。 - Feの一部に代えて、質量%で、Cu:0.30%以下、Ni:0.25%以下のうちの1種以上を含有することを特徴とする請求項1に記載の窒化用鋼。
- 請求項1または2に記載の化学組成を有し、表面硬さがビッカース硬さで650~900、芯部硬さがビッカース硬さで150以上、有効硬化層深さが0.15mm以上であることを特徴とする窒化部品。
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KR1020137022889A KR20130121966A (ko) | 2011-02-01 | 2012-01-26 | 질화용 강 및 질화 부품 |
CN201280007367.5A CN103348031B (zh) | 2011-02-01 | 2012-01-26 | 氮化用钢以及氮化部件 |
US13/982,594 US20140034194A1 (en) | 2011-02-01 | 2012-01-26 | Steel for nitriding and nitrided component |
US15/623,434 US10370747B2 (en) | 2011-02-01 | 2017-06-15 | Nitrided component |
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US15/623,434 Division US10370747B2 (en) | 2011-02-01 | 2017-06-15 | Nitrided component |
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BR112016025118B1 (pt) * | 2014-04-30 | 2021-02-17 | Jfe Steel Corporation | chapa de aço de alta resistência e método para fabricação da mesma |
JP6551224B2 (ja) * | 2015-12-25 | 2019-07-31 | 日本製鉄株式会社 | 鋼管の製造方法 |
CN106222570B (zh) * | 2016-08-16 | 2018-03-20 | 武汉钢铁有限公司 | 一种耐锈蚀性能优良的渗氮钢用基板及生产方法 |
US11453105B2 (en) | 2016-09-13 | 2022-09-27 | Milwaukee Electric Tool Corporation | Powered ratcheting torque wrench |
US10625405B2 (en) | 2016-09-13 | 2020-04-21 | Milwaukee Electric Tool Corporation | Powered ratcheting torque wrench |
CN109371332A (zh) * | 2018-02-02 | 2019-02-22 | 宝钢特钢长材有限公司 | 一种16MnCrS5齿轮钢及其生产方法 |
US20210340661A1 (en) * | 2018-06-11 | 2021-11-04 | John Eric Chapman | Hybrid Washer and Method of Manufacture |
JP7230651B2 (ja) * | 2019-04-05 | 2023-03-01 | 日本製鉄株式会社 | 窒化用鋼板 |
EP4151761A4 (en) * | 2020-05-15 | 2023-10-11 | JFE Steel Corporation | STEEL AND STEEL COMPONENT |
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US20140034194A1 (en) | 2014-02-06 |
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KR20130121966A (ko) | 2013-11-06 |
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CN103348031B (zh) | 2019-01-04 |
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