WO2022044392A1 - Sliding member and method for producing same - Google Patents

Sliding member and method for producing same Download PDF

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Publication number
WO2022044392A1
WO2022044392A1 PCT/JP2021/009318 JP2021009318W WO2022044392A1 WO 2022044392 A1 WO2022044392 A1 WO 2022044392A1 JP 2021009318 W JP2021009318 W JP 2021009318W WO 2022044392 A1 WO2022044392 A1 WO 2022044392A1
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Prior art keywords
layer
sliding member
carburized
member according
nitriding
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PCT/JP2021/009318
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French (fr)
Japanese (ja)
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久光 波東
圭吾 中村
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株式会社日立製作所
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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
    • 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

Definitions

  • the present invention relates to a sliding member and a method for manufacturing the same.
  • sliding members In recent years, the usage environment of sliding members has been getting harsher. For example, in the aerospace field, high-speed rotation and use in high-temperature and low-temperature environments are required for weight reduction and performance improvement. In the consumer field, performance improvement by ultra-high speed rotation is required for vacuum cleaners, and in the machine tool field, high surface pressure that can withstand heavy cutting is required. Further, in the electric power field, high surface pressure is required to improve power generation efficiency in air volume power generation, and in the construction machinery field, low friction is required to improve the efficiency and operation response of hydraulic pump parts. In the automobile field, various sliding members are used, and there are all needs for high speed rotation, high surface pressure and low friction.
  • Damage near the surface of the member to be slid is mainly controlled by the following three types of damage.
  • the maximum shear stress of Hertz is generated at a deeper position as the acting load is larger, but considering the surface pressure range used in the current industrial field, it is the maximum at a depth of several tens of ⁇ m to several hundreds of ⁇ m from the surface. Become. Hardening at depths from tens of ⁇ m to hundreds of ⁇ m from the surface is important to increase durability against internal damage caused by the maximum shear stress of Hertz, and it is generally possible to harden from the surface to deep regions. Carburizing and induction hardening have been applied.
  • martensite produced by carburizing or induction hardening has higher frictional resistance and lower tempering softening resistance than the compound layer (nitriding layer) generated by nitriding described below.
  • the tempering and softening of the sliding portion due to the frictional heat generation of the sliding portion is suppressed as the frictional resistance is lower.
  • the compound layer produced by nitriding Fe 2-3 N ⁇ phase and Fe 4 N ⁇ ' is similar to the above reduction in frictional resistance. Phase) etc. are applied.
  • Patent Document 1 as a method of carburizing and nitriding a steel member, a Cr-containing steel member is carburized so as to have a carburizing concentration of 1.0% or more, and then only the carbide-forming layer on the surface layer of the steel member is subjected to carburizing treatment.
  • a method of subjecting a carburizing treatment and then quenching the steel member is disclosed.
  • the surface portion where high durability is required has low frictional resistance and is less likely to be tempered and softened.
  • the inside thereof has a hardened layer of several hundred ⁇ m or more.
  • the outermost surface of the layer, which has low friction and is less likely to be tempered and softened, and the hardened layer inside it are not completely separated layers, but are inclined layers in which the components of both are continuously changed. Is desirable.
  • the soaking treatment described in Patent Document 1 has a soaking concentration of about 0.3%. Further, in Patent Document 1, as an effect, in order to compensate for the decrease in hardenability due to the decrease in the amount of solid solution Cr in the surface layer portion as well as the increase in hardness, the hardness of the deep layer portion is obtained by subjecting only the surface layer portion to a nitriding treatment. Although it is described that the hardenability of the surface layer portion is improved while preventing the deterioration, there is room for improvement in terms of friction reduction on the outermost surface, temper softening resistance, peeling resistance and the like.
  • An object of the present invention is to provide a sliding member having a structure for suppressing internal damage, surface damage and softening damage in the vicinity of a surface, having low friction, and having high durability against high surface pressure.
  • the sliding member of the present invention has a structure in which a surface layer is formed on the outer surface region of the base material, and the surface layer is a nitride layer containing iron nitride having a nitrogen concentration of 5.9 to 11.1% on a mass basis. It contains a carburized layer located between the nitrided layer and the center of the base metal, and at least a part of the carburized layer is a martensite layer, and between the nitrided layer and the martensite layer, both are included.
  • a sloping layer is formed in which the concentrations of nitrogen and carbon, which are the components of the above, are continuously changing.
  • the method for manufacturing a sliding member of the present invention is a method for manufacturing a sliding member by forming a surface layer including a nitrided layer and a carburized layer in an outer surface region of the base material, and the base material is predetermined by high-frequency induction heating.
  • the nitriding layer includes a high-frequency treatment step of heating to the temperature of the above, a nitriding treatment step of supplying a nitriding gas to form a nitriding layer, and a carburizing step.
  • the carburized layer contains% iron nitride and is located between the nitrided layer and the center of the base metal, and at least a part of the carburized layer is a martenesite layer, between the nitrided layer and the martensite layer. Is formed with a sloping layer in which the concentrations of both components, nitrogen and carbon, are continuously changing.
  • a sliding member having a structure for suppressing internal damage, surface damage and softening damage in the vicinity of the surface, having low friction, and having high durability against high surface pressure.
  • FIG. 1 It is a transmission electron microscope image which shows the cross section of the test piece of Example 1.
  • FIG. 1 is a graph which shows the result of having analyzed the cross-sectional structure shown in FIG. 1 by the electron beam microanalyzer. It is an image which shows the result of phase identification of the cross-sectional structure shown in FIG. 1 by electron backscatter diffraction. It is a graph which shows the measurement result of the cross-sectional hardness of the test piece of Example 1.
  • FIG. It is a schematic diagram which shows the main part of the reciprocating sliding wear tester. It is a schematic diagram which shows the main part of the rolling fatigue tester. It is a flow figure which shows the manufacturing method of the sliding member of Example 1.
  • the present invention relates to a surface treatment technique for sliding members.
  • first processing method In the first step, the surface of the steel material is carburized at a temperature of about 900 ° C. to 1000 ° C. and cooled without quenching.
  • second step nitriding is performed to form a compound layer at a temperature of about 500 ° C to 580 ° C, and quenching is performed. In this case, since the quenching temperature is lower than the A1 transformation point, the carburized layer is not quenched and the hardness of the carburized layer becomes low.
  • the surface of the steel material is carburized at a temperature of about 900 ° C. to 1000 ° C. and quenched.
  • the carburized layer hardens due to quenching.
  • nitriding is performed to form a compound layer at a temperature of about 500 ° C to 580 ° C.
  • the carburized layer cured in the first step is tempered and softened.
  • the surface of the steel material is carburized at a temperature of about 900 ° C to 1000 ° C.
  • nitriding is performed to form a compound layer by cooling from a carburizing temperature of about 900 ° C. to 1000 ° C. to a nitriding temperature of about 500 ° C. to 580 ° C.
  • quenching is performed by heating to about the A1 transformation point or higher (for example, 830 ° C to 850 ° C). In this case, since the heating in the third step requires time for heating the furnace, nitrogen is released from the compound layer formed in the second step, and the compound layer disappears.
  • a nitride layer is formed on the outermost surface of the surface layer in the outer surface region of the base material.
  • the nitrided layer includes an ⁇ phase (Fe 2-3 N), a ⁇ 'phase (Fe 4 N), or a composite layer of an ⁇ phase and a ⁇ 'phase. These phases have the characteristics of low friction and high temper softening resistance.
  • a carburized layer is formed between the nitrided layer and the center of the base metal. At least a part of the carburized layer is a martensite layer (martensite structure).
  • the martensite layer is a hardened layer produced by carburizing and quenching and can withstand high surface pressure.
  • the martensite layer extends over several hundred ⁇ m.
  • an inclined layer is formed in which the concentrations of nitrogen and carbon, which are the components of both, are continuously changed.
  • the inclined layer has a structure having excellent peel resistance and high temper softening resistance.
  • the first method for constructing the above structure is to heat a carburized steel or a bearing steel carburized in carbon steel or the like by high frequency induction heating or energization heating in an atmosphere of nitride gas to a temperature equal to or higher than the A1 transformation point, for example. , 750 ° C to 850 ° C for several minutes or less, held for about 1 minute, a compound layer is formed on the outermost surface, and quenching is performed.
  • the A1 transformation point referred to here means the A1 transformation point of the carburized layer (the same applies hereinafter).
  • Nitrogen gas may be filled before heating or after being heated to about 750 ° C to 850 ° C.
  • nitriding at about 750 ° C. to 850 ° C. is not performed with a high nitriding potential, the diffusion of nitrogen becomes predominant, a compound layer having a high nitrogen concentration is not formed on the surface, and only an immersion layer having a low nitrogen concentration is formed. Not done.
  • ammonia which is a nitriding gas, in the range of 1 ⁇ 10 4 Pa to atmospheric pressure, and the concentration of ammonia is as high as 20% to 100%.
  • the temperature, ammonia pressure, and ammonia concentration have a range because there are suitable conditions for obtaining a compound layer in each combination of conditions.
  • the second method for constructing the above structure is to heat the carburized steel or the bearing steel carburized in carbon steel or the like by high frequency induction heating or energization heating in the atmosphere of nitride gas at 600 ° C. or higher and lower than the A1 transformation point. Heat to a temperature of several minutes or less, hold for about 1 to 30 minutes, form a compound layer on the outermost surface, and raise the temperature above the A1 transformation point, for example, about 800 ° C to 850 ° C, by high-frequency induction heating or energization heating. It has a step of heating in 1 minute or less and promptly quenching.
  • Nitrogen gas may be filled before heating or after being heated to a temperature of 600 ° C. or higher and lower than the A1 transformation point.
  • the temperature above the A1 transformation point for example, heating from 800 ° C. to 850 ° C. is not rapidly performed, the nitrogen in the compound layer is decomposed and released into the atmosphere. It is desirable to heat it in 1 minute or less because it may diffuse into the base material and deteriorate the properties of the compound layer or the compound layer may disappear.
  • nitriding at a temperature of 600 ° C. or higher and lower than the A1 transformation point is not carried out at a high nitriding potential, the diffusion of nitrogen becomes dominant, a compound layer having a high nitrogen concentration is not formed, and only an immersion layer having a low nitrogen concentration is formed. Not done.
  • nitriding at a high nitriding potential it is desirable to carry out nitriding of ammonia, which is a nitriding gas, in the range of 0.1 ⁇ 10 4 Pa to atmospheric pressure, and the concentration of ammonia is as high as 10% to 100%.
  • the temperature, ammonia pressure, and ammonia concentration have a range because there are suitable conditions for obtaining a compound layer in each combination of conditions.
  • the quenching process be performed at a temperature equal to or higher than the A1 transformation point of the carburized layer.
  • the quenching process be performed by heating to a temperature equal to or higher than the A1 transformation point.
  • the quenching step is performed by heating to a temperature equal to or higher than the A1 transformation point, it is desirable that the heating is performed at a heating rate that suppresses the decomposition of nitrogen in the nitrided layer.
  • the rate of temperature rise is preferably 100 ° C./min or higher.
  • test piece in this example was performed as follows.
  • a round bar test piece of chrome molybdenum steel SCM435 was used as a base material. This round bar test piece has a carbon concentration of about 0.35% and dimensions of 10 mm in diameter ⁇ 10 mm in length.
  • This round bar test piece is heated to 950 ° C in about 1 minute by high frequency induction heating, and the temperature is maintained. That is, the rate of temperature rise is 100 ° C./min or higher.
  • acetylene which is a carburized gas
  • a carburized layer was formed by vacuum carburizing.
  • the material on which the carburized layer is formed in this way may be referred to as a "carburized material”, and the material subjected to the carburized treatment as a pretreatment in this way may be referred to as a "base material".
  • the base metal does not need to be carburized to its center.
  • the carburized layer changed from the martensite layer to a depth of 1.0 mm or more from the outermost surface of the test piece. This provides durability against internal damage due to the maximum shear stress in Hertz.
  • FIG. 1 shows a transmission electron microscope image (TEM image) of the cross-sectional structure of the test piece obtained by the above treatment.
  • the cross section of the test piece has the following three layers. That is, the compound layer 1 (nitriding layer), the inclined layer 2, and the carburized layer 3.
  • the compound layer 1, the inclined layer 2, and the carburized layer 3 are laminated in order from the outermost surface on the outer surface region of the base metal, and these three layers form the surface layer.
  • FIG. 2 shows the results of analysis of the cross-sectional structure shown in FIG. 1 by an electron beam microanalyzer.
  • the two graphs shown in FIG. 2 show the concentration distribution of nitrogen and carbon.
  • an ⁇ phase (Fe 2-3 N) with a nitrogen concentration of about 8% is formed in the range from the outermost surface to a depth of about 7 ⁇ m, and the inner thickness is about about 7
  • a ⁇ 'phase (Fe 4 N) having a nitrogen concentration of about 5.9% is formed in the region of 1 ⁇ m.
  • the ⁇ phase and the ⁇ 'phase are the compound layer 1.
  • the nitrogen concentration is 11.1% in the case of Fe 2N and 7.7% in the case of Fe 3N .
  • the carbon concentration gradually increases in the range from about 8 ⁇ m to about 21 ⁇ m in depth.
  • the carbon concentration is almost constant (about 0.8%) inside the depth of about 25 ⁇ m.
  • the range from a depth of about 8 ⁇ m to about 21 ⁇ m is called the inclined layer 2, and the region deeper than that is called the carburized layer 3.
  • the surface layer contains a nitrided layer (compound layer 1) containing iron nitride having a nitrogen concentration of 5.9 to 11.1%, and is carburized located between the nitrided layer and the central portion of the base metal.
  • layer 3 the central portion of the base metal refers to the inner region of the test piece covered with the surface layer.
  • At least a part of the carburized layer 3 is a martensite layer.
  • the inclined layer 2 is a region formed between the nitrided layer and the martensite layer in which the concentrations of nitrogen and carbon, which are components of both (nitrided layer and martensite layer), are continuously changed. be. More specifically, the inclined layer 2 has a structure in which the nitrogen concentration decreases toward the center of the base metal and the carbon concentration increases toward the center of the base metal.
  • FIG. 3 shows the results of phase identification of the cross-sectional structure shown in FIG. 1 by electron backscatter diffraction.
  • an ⁇ phase (Fe 2-3 N), a ⁇ 'phase (Fe 4 N), and an ⁇ phase (ferrite) are formed from the outermost surface toward the inside.
  • FIG. 4 is a graph showing the measurement result of the cross-sectional hardness.
  • the horizontal axis is the distance (depth) from the outermost surface, and the vertical axis is the Vickers hardness Hv0.2 (hardness).
  • the hardness of the carburized layer is about 800 Hv near the surface, and the effective curing depth of 550 Hv or more is about 1 mm.
  • FIG. 7 collectively shows the processing process of the test piece in this embodiment, that is, the manufacturing method of the sliding member.
  • high frequency induction heating capable of heating a material such as a steel material to a predetermined temperature in a very short time is applied.
  • a vacuum carburizing treatment S120
  • a carburizing gas such as acetylene is supplied to increase the carbon concentration on the surface of the material.
  • a nitriding treatment S130
  • a nitriding gas such as ammonia is supplied to form a compound layer.
  • quenching (S140) and tempering (S150) are performed.
  • the round bar test piece was treated in the same manner as in Example 1 to form a carburized layer.
  • Example 1 In this example as well, the same structure and hardness as in Example 1 were confirmed.
  • FIG. 8 collectively shows the processing process of the test piece in this embodiment, that is, the manufacturing method of the sliding member.
  • high frequency induction heating capable of heating a material such as a steel material to a predetermined temperature in a very short time is applied.
  • a vacuum carburizing treatment S220
  • a carburizing gas such as acetylene is supplied to increase the carbon concentration on the surface of the material.
  • a nitriding treatment S230
  • a nitriding gas such as ammonia is supplied to form a compound layer.
  • induction hardening (S240) and tempering S250 are performed.
  • a round bar test piece of bearing steel SUJ2 was used as a base material.
  • This round bar test piece has a carbon concentration of about 1% and has dimensions of 10 mm in diameter ⁇ 10 mm in length.
  • this base material will be referred to as "bearing steel material”.
  • This round bar test piece was supplied with 100% ammonia gas, which is a nitride gas, to a pressure of 9 ⁇ 10 4 Pa, heated to 850 ° C. in about 1 minute by high frequency heating, and held for 1 minute to form a compound layer. did.
  • This process can be called a high frequency nitriding process.
  • the temperature rising rate in this case is 100 ° C./min or more. It can also be said that the nitriding treatment step is performed by using high frequency induction heating.
  • Example 1 In this example as well, the same structure and hardness as in Example 1 were confirmed.
  • a round bar test piece of bearing steel SUJ2 was used as a base material. This round bar test piece has a carbon concentration of about 1% and has dimensions of 10 mm in diameter ⁇ 10 mm in length.
  • This round bar test piece was supplied with 100% ammonia gas, which is a nitride gas, to a pressure of 6 ⁇ 10 4 Pa, heated to 630 ° C. in about 1 minute by high frequency heating, and held for 3 minutes to form a compound layer. did. Then, ammonia was exhausted, replaced with an inert gas, and then quenched by high-frequency heating. As a result, the carburized layer was organized into martensite. Tempering was carried out at 180 ° C. for 30 minutes.
  • ammonia gas which is a nitride gas
  • Example 1 In this example as well, the same structure and hardness as in Example 1 were confirmed.
  • the conventional method refers to a method of performing carburizing, nitriding or carburizing nitriding without using high frequency heating.
  • Example 2 The same round bar test piece as in Example 1 is heated to 950 ° C in about 60 minutes in a vacuum carburizing furnace, and the temperature is maintained. After reaching 950 ° C, acetylene, which is a carburized gas, is supplied, and the carburized layer is quenched by vacuum carburizing for about 5 hours so that the carbon concentration is 0.8% and the effective effect depth is 1 mm. Was formed.
  • Example 2 The same round bar test piece as in Example 1 is heated to 570 ° C in about 60 minutes in a nitriding furnace, and the temperature is maintained. After reaching 570 ° C., ammonia as a nitriding gas was supplied, and nitriding treatment was performed for about 3 hours so that the nitrogen concentration became about 8% to form a nitrided layer.
  • a round bar test piece similar to that in Example 1 is heated to 950 ° C. in about 60 minutes in a vacuum carburizing furnace, and the temperature is maintained. After reaching 950 ° C., acetylene, which is a carburizing gas, was supplied and vacuum carburized for about 5 hours so that the carbon concentration was 0.8% and the effective effect depth was 1 mm to form a carburized layer. .. Then, a mixed gas in which 5 mol% of ammonia, which is a nitride gas, was mixed with nitrogen was cooled to 850 ° C. in 1 hour while maintaining a pressure of 1 ⁇ 10 3 Pa to form a carburized nitrided layer. After that, quenching was performed.
  • the friction coefficient and seizure load were measured using a reciprocating sliding wear tester.
  • FIG. 5 is a schematic diagram showing a main part of the reciprocating sliding wear tester.
  • the friction test piece 4 and the friction test mating material 5 are installed and fixed in the testing machine.
  • Lubricating oil 6 is applied onto the friction test mating material 5, the friction test mating material 5 is raised, and the friction test mating material 5 is brought into contact with the friction test piece 4.
  • the friction test mating material 5 is heated to 80 ° C. with a heater to maintain the temperature. After the temperature reaches 80 ° C. and stabilizes, sliding 7 is started. Then, the load 8 is increased in 0.1 kN increments every 2 minutes, and the test is continued until seizure occurs. Friction resistance was measured during the test, and seizure was determined when the frictional resistance increased sharply.
  • Table 1 shows the test results of frictional resistance and seizure load.
  • FIG. 6 is a schematic diagram showing a main part of a rolling fatigue tester.
  • the rolling test piece 9 and the rolling test partner material 10 are installed in the testing machine and fixed.
  • the lubricating oil 6 is heated to 60 ° C. and poured over the contact portion between the rolling test piece 9 and the rolling test mating material 10.
  • the rolling test mating material 10 is rotated at 1000 RPM by a motor, the rolling test piece 9 is rotated at 800 RPM by another motor, and a load 8 is applied to the contact surface so that the surface pressure of the contact portion becomes 3 GPa. Add.
  • the rolling fatigue test is continued. Then, the test is stopped when significant pitching damage occurs in the contact portion, and the life is judged.
  • the determination of significant pitching damage is detected by a vibration sensor attached in the vicinity of the rolling test piece 9.
  • Table 2 shows the results of the rolling fatigue test.
  • the rolling fatigue life is shown as a ratio with the life of conventional nitriding as 1.
  • conventional carburizing is 5 times and conventional carburizing nitriding is 7 times.
  • Examples 1 and 2 are test pieces obtained by molding a material containing carbon (C) having a content of 0.2 to 0.6% and unavoidable impurities and the balance being iron (Fe) by powder metallurgy. When the same treatment as in the above was performed and the effect was confirmed, it was confirmed that the same effect as in Examples 1 and 2 was obtained.
  • C carbon
  • Fe iron
  • the base metal was formed by powder metallurgy.
  • the carbon concentration of the carburized layer of the carburized material is preferably 0.5% or more, and more preferably 0.7% or more.
  • the carbon concentration is preferably 2.0% or less, and more preferably 1.5% or less.
  • the nitrogen concentration of the nitrided layer is preferably 0.5% or more , and the upper limit value is preferably 11.1% or less, which corresponds to the case of Fe 2N.
  • the lower limit is more preferably 0.7% or more.

Abstract

A sliding member which has a configuration wherein a surface layer is formed in the outer surface region of a base material; the surface layer comprises a nitrided layer that contains iron nitride having a nitrogen concentration of from 5.9% to 11.1% on a mass basis, while comprising a carburization layer that is positioned between the nitrided layer and the central part of the base material; at least a part of the carburization layer is a martensite layer; and a gradient layer, in which the concentrations of nitrogen and carbon are continuously changed, is formed between the nitrided layer and the martensite layer, said nitrogen and carbon being components of the nitrided layer and the martensite layer. Consequently, the present invention is able to provide a sliding member which has a configuration that suppresses internal damage in the vicinity of the surface, surface damage and softening damage, while having low friction and high durability in terms of high contact pressure.

Description

摺動部材及びその製造方法Sliding member and its manufacturing method
　本発明は、摺動部材及びその製造方法に関する。 The present invention relates to a sliding member and a method for manufacturing the same.
　近年、摺動部材の使用環境は、過酷化の一途をたどっている。例えば、航空・宇宙分野では、軽量化、性能向上のために高速回転化、高温及び低温の環境での使用が求められている。民生分野では掃除機などで超高速回転化による性能向上が、工作機械分野では重切削に耐える高面圧化が求められている。また、電力分野では風量発電などで発電効率向上のための高面圧化が、建機分野では油圧ポンプ部品の効率及び動作レスポンスの向上のために低摩擦化が求められている。自動車分野では、多様な摺動部材が使用されており、高速回転、高面圧及び低摩擦の全てのニーズがある。 In recent years, the usage environment of sliding members has been getting harsher. For example, in the aerospace field, high-speed rotation and use in high-temperature and low-temperature environments are required for weight reduction and performance improvement. In the consumer field, performance improvement by ultra-high speed rotation is required for vacuum cleaners, and in the machine tool field, high surface pressure that can withstand heavy cutting is required. Further, in the electric power field, high surface pressure is required to improve power generation efficiency in air volume power generation, and in the construction machinery field, low friction is required to improve the efficiency and operation response of hydraulic pump parts. In the automobile field, various sliding members are used, and there are all needs for high speed rotation, high surface pressure and low friction.
　摺動を受ける部材の表面近傍の損傷は、主に、次に述べる３つの損傷形態に支配される。 Damage near the surface of the member to be slid is mainly controlled by the following three types of damage.
　（１）ヘルツの最大せん断応力起因の内部せん断損傷（以下「内部損傷」という。）
　（２）摺動部の摩擦抵抗に起因する表面のせん断応力起因のせん断損傷（以下「表面損傷」という。）
　（３）摺動部の摩擦発熱に伴う摺動部の焼戻し軟化による焼戻し軟化損傷（以下「軟化損傷」という。）
　これらの損傷形態の防止又は軽減ができれば、高耐久な摺動部材の提供が可能となる。 (1) Internal shear damage caused by the maximum shear stress in Hertz (hereinafter referred to as "internal damage")
(2) Shear damage due to surface shear stress due to frictional resistance of sliding parts (hereinafter referred to as "surface damage")
(3) Tempering softening damage due to tempering softening of the sliding part due to frictional heat generation of the sliding part (hereinafter referred to as "softening damage")
If these damage forms can be prevented or reduced, it is possible to provide a highly durable sliding member.
　ヘルツの最大せん断応力は、作用荷重が大きいほど深い位置で発生するが、現在の工業分野で使用される面圧範囲で考えると、表面から数十μｍから数百μｍまでの深さで最大となる。ヘルツの最大せん断応力起因の内部損傷に対する耐久性を高めるには、表面から数十μｍから数百μｍまでの深さにおける硬化が重要であり、一般的には表面から深い領域まで硬化が可能な浸炭及び高周波焼入れが適用されている。 The maximum shear stress of Hertz is generated at a deeper position as the acting load is larger, but considering the surface pressure range used in the current industrial field, it is the maximum at a depth of several tens of μm to several hundreds of μm from the surface. Become. Hardening at depths from tens of μm to hundreds of μm from the surface is important to increase durability against internal damage caused by the maximum shear stress of Hertz, and it is generally possible to harden from the surface to deep regions. Carburizing and induction hardening have been applied.
　浸炭や高周波焼入れでできるマルテンサイトは、次に述べる、窒化により生成される化合物層（窒化層）などに比べ摩擦抵抗が高いこと、焼戻し軟化抵抗が低いことが知られている。 It is known that martensite produced by carburizing or induction hardening has higher frictional resistance and lower tempering softening resistance than the compound layer (nitriding layer) generated by nitriding described below.
　摺動部の摩擦抵抗に起因する表面のせん断応力は、摩擦抵抗が低いほど軽減されるため、窒化により生成される化合物層（Ｆｅ２～３Ｎのε相及びＦｅ４Ｎのγ’相）などが適用されている。 Since the surface shear stress caused by the frictional resistance of the sliding portion is reduced as the frictional resistance is lower, the compound layer produced by nitridation (Fe 2-3 N ε phase and Fe 4 N γ'phase). Etc. have been applied.
　摺動部の摩擦発熱に伴う摺動部の焼戻し軟化は、摩擦抵抗が低いほど抑制される。また、材質的に焼戻し軟化が起きにくい材料ほど抑制されるため、上記の摩擦抵抗の低減と同様に、窒化により生成される化合物層（Ｆｅ２～３Ｎのε相及びＦｅ４Ｎのγ’相）などが適用されている。 The tempering and softening of the sliding portion due to the frictional heat generation of the sliding portion is suppressed as the frictional resistance is lower. In addition, since the material that is less likely to be tempered and softened is suppressed, the compound layer produced by nitriding (Fe 2-3 N ε phase and Fe 4 N γ') is similar to the above reduction in frictional resistance. Phase) etc. are applied.
　特許文献１には、鋼部材の浸炭窒化方法として、Ｃｒ含有の鋼部材を１．０％以上の浸炭濃度となるように浸炭処理し、次にその鋼部材の表層部の炭化物生成層のみに浸窒処理を施し、その後上記鋼部材を焼入れ処理する方法が開示されている。特許文献１には、浸炭濃度は最大３．０％程度とすることが望ましいこと、浸窒処理は０．３～０．４の浸窒濃度となるように行なうことが望ましいこと、浸窒濃度つまりＮポテンシャル＝０．３％という説明、実施例において浸窒処理を８２０～８８０℃で行うこと、実施例の０．１％Ｎ有効浸窒深さが０．０７～０．０９ｍｍであることも開示されている。 In Patent Document 1, as a method of carburizing and nitriding a steel member, a Cr-containing steel member is carburized so as to have a carburizing concentration of 1.0% or more, and then only the carbide-forming layer on the surface layer of the steel member is subjected to carburizing treatment. A method of subjecting a carburizing treatment and then quenching the steel member is disclosed. According to Patent Document 1, it is desirable that the carburization concentration be about 3.0% at the maximum, and that the soaking treatment should be performed so that the soaking concentration is 0.3 to 0.4. That is, the explanation that N potential = 0.3%, the infiltration treatment is performed at 820 to 880 ° C. in the examples, and the 0.1% N effective infiltration depth in the examples is 0.07 to 0.09 mm. Is also disclosed.
特開昭６３－２１０２８７号公報Japanese Unexamined Patent Publication No. 63-210287
　高い耐久性が求められる表面部は、表面損傷及び軟化損傷の観点から、摩擦抵抗が小さく、かつ、焼戻し軟化が起こりにくいことが望ましい。また、その内部は、内部損傷の観点から、数百μｍ以上の硬化層を有することが望ましい。さらには、最外表面が低摩擦で焼戻し軟化が起きにくい層と、その内部の硬化層との間は、完全に分離した層ではなく、両者の成分が連続的に変化する傾斜層であることが望ましい。 From the viewpoint of surface damage and softening damage, it is desirable that the surface portion where high durability is required has low frictional resistance and is less likely to be tempered and softened. Further, from the viewpoint of internal damage, it is desirable that the inside thereof has a hardened layer of several hundred μm or more. Furthermore, the outermost surface of the layer, which has low friction and is less likely to be tempered and softened, and the hardened layer inside it are not completely separated layers, but are inclined layers in which the components of both are continuously changed. Is desirable.
　このような望ましい表面部の形成は、一般に用いられる炉加熱による表面処理技術では困難であった。 The formation of such a desirable surface portion was difficult with the commonly used surface treatment technique by heating in a furnace.
　特許文献１に記載の浸窒処理は、浸窒濃度が０．３％程度のものである。また、特許文献１には、効果として、高硬度化とともに、表層部の固溶Ｃｒ量の減少により焼入れ性が低下するのを補うため表層部のみに浸窒処理を施すことにより深層部の硬度低下を防止しつつ表層部の焼入れ性を向上させることが記載されているが、最外表面における摩擦低減、焼戻し軟化抵抗、耐剥離性等の観点において改善の余地がある。 The soaking treatment described in Patent Document 1 has a soaking concentration of about 0.3%. Further, in Patent Document 1, as an effect, in order to compensate for the decrease in hardenability due to the decrease in the amount of solid solution Cr in the surface layer portion as well as the increase in hardness, the hardness of the deep layer portion is obtained by subjecting only the surface layer portion to a nitriding treatment. Although it is described that the hardenability of the surface layer portion is improved while preventing the deterioration, there is room for improvement in terms of friction reduction on the outermost surface, temper softening resistance, peeling resistance and the like.
　本発明は、表面近傍における内部損傷、表面損傷及び軟化損傷を抑制する構成を有し、低摩擦で、かつ、高面圧に対する耐久性の高い摺動部材を提供することを目的とする。 An object of the present invention is to provide a sliding member having a structure for suppressing internal damage, surface damage and softening damage in the vicinity of a surface, having low friction, and having high durability against high surface pressure.
　本発明の摺動部材は、母材の外面領域に表面層を形成した構成を有し、表面層は、窒素濃度が質量基準で５．９～１１．１％の窒化鉄を含む窒化層を含み、かつ、窒化層と母材の中心部との間に位置する浸炭層を含み、浸炭層の少なくとも一部は、マルテンサイト層であり、窒化層とマルテンサイト層との間には、両者の成分である窒素と炭素との濃度が連続的に変化している傾斜層が形成されている。 The sliding member of the present invention has a structure in which a surface layer is formed on the outer surface region of the base material, and the surface layer is a nitride layer containing iron nitride having a nitrogen concentration of 5.9 to 11.1% on a mass basis. It contains a carburized layer located between the nitrided layer and the center of the base metal, and at least a part of the carburized layer is a martensite layer, and between the nitrided layer and the martensite layer, both are included. A sloping layer is formed in which the concentrations of nitrogen and carbon, which are the components of the above, are continuously changing.
　本発明の摺動部材の製造方法は、母材の外面領域に窒化層及び浸炭層を含む表面層を形成することにより摺動部材を製造する方法であって、母材を高周波誘導加熱により所定の温度まで加熱する高周波処理工程と、窒化ガスを供給して窒化層を形成する窒化処理工程と、焼入れ工程と、を含み、窒化層は、窒素濃度が質量基準で５．９～１１．１％の窒化鉄を含み、浸炭層は、窒化層と母材の中心部との間に位置し、浸炭層の少なくとも一部は、マルテンサイト層であり、窒化層とマルテンサイト層との間には、両者の成分である窒素と炭素との濃度が連続的に変化している傾斜層が形成されている。 The method for manufacturing a sliding member of the present invention is a method for manufacturing a sliding member by forming a surface layer including a nitrided layer and a carburized layer in an outer surface region of the base material, and the base material is predetermined by high-frequency induction heating. The nitriding layer includes a high-frequency treatment step of heating to the temperature of the above, a nitriding treatment step of supplying a nitriding gas to form a nitriding layer, and a carburizing step. The carburized layer contains% iron nitride and is located between the nitrided layer and the center of the base metal, and at least a part of the carburized layer is a martenesite layer, between the nitrided layer and the martensite layer. Is formed with a sloping layer in which the concentrations of both components, nitrogen and carbon, are continuously changing.
　本発明によれば、表面近傍における内部損傷、表面損傷及び軟化損傷を抑制する構成を有し、低摩擦で、かつ、高面圧に対する耐久性の高い摺動部材を提供することができる。 According to the present invention, it is possible to provide a sliding member having a structure for suppressing internal damage, surface damage and softening damage in the vicinity of the surface, having low friction, and having high durability against high surface pressure.
実施例１の試験片の断面を示す透過型電子顕微鏡画像である。It is a transmission electron microscope image which shows the cross section of the test piece of Example 1. FIG. 図１に示す断面組織を電子線マイクロアナライザにより分析した結果を示すグラフである。It is a graph which shows the result of having analyzed the cross-sectional structure shown in FIG. 1 by the electron beam microanalyzer. 図１に示す断面組織を電子線後方散乱回折により相同定をした結果を示す画像である。It is an image which shows the result of phase identification of the cross-sectional structure shown in FIG. 1 by electron backscatter diffraction. 実施例１の試験片の断面硬度の測定結果を示すグラフである。It is a graph which shows the measurement result of the cross-sectional hardness of the test piece of Example 1. FIG. 往復摺動摩耗試験機の要部を示す模式図である。It is a schematic diagram which shows the main part of the reciprocating sliding wear tester. 転がり疲労試験機の要部を示す模式図である。It is a schematic diagram which shows the main part of the rolling fatigue tester. 実施例１の摺動部材の製造方法を示すフロー図である。It is a flow figure which shows the manufacturing method of the sliding member of Example 1. FIG. 実施例２の摺動部材の製造方法を示すフロー図である。It is a flow chart which shows the manufacturing method of the sliding member of Example 2.
　本発明は、摺動部材の表面処理技術に関する。 The present invention relates to a surface treatment technique for sliding members.
　はじめに、浸炭処理及び窒化処理に関する従来の処理方法の問題点について、例を挙げて説明する。 First, the problems of the conventional treatment methods related to carburizing treatment and nitriding treatment will be explained with examples.
　（第１の処理方法）
　第１の工程で鋼材表面に９００℃～１０００℃程度の温度で浸炭を行い、焼入れせずに冷却する。第２の工程で５００℃から５８０℃程度の温度で化合物層を形成する窒化を行い、焼入れする。この場合、焼入れ温度がＡ１変態点より低いため、浸炭層が焼入れされず、浸炭層の硬度が低くなってしまう。 (First processing method)
In the first step, the surface of the steel material is carburized at a temperature of about 900 ° C. to 1000 ° C. and cooled without quenching. In the second step, nitriding is performed to form a compound layer at a temperature of about 500 ° C to 580 ° C, and quenching is performed. In this case, since the quenching temperature is lower than the A1 transformation point, the carburized layer is not quenched and the hardness of the carburized layer becomes low.
　（第２の処理方法）
　第１の工程で鋼材表面に９００℃～１０００℃程度の温度で浸炭を行い、焼入れを行う。焼入れを行うため、浸炭層は硬化する。第２の工程で５００℃から５８０℃程度の温度で化合物層を形成する窒化を行う。この場合、第１の工程で硬化した浸炭層が焼戻され、軟化してしまう。 (Second processing method)
In the first step, the surface of the steel material is carburized at a temperature of about 900 ° C. to 1000 ° C. and quenched. The carburized layer hardens due to quenching. In the second step, nitriding is performed to form a compound layer at a temperature of about 500 ° C to 580 ° C. In this case, the carburized layer cured in the first step is tempered and softened.
　（第３の処理方法）
　第１の工程で鋼材表面に９００℃～１０００℃程度の温度で浸炭を行う。第２の工程で浸炭温度９００℃～１０００℃程度から窒化温度５００℃から５８０℃程度まで冷却し化合物層を形成する窒化を行う。第３の工程で窒化後にＡ１変態点以上（例えば８３０℃～８５０℃）程度に加熱し焼入れを行う。この場合、炉加熱のため、第３の工程の加熱に時間を要するため、第２の工程で形成した化合物層から窒素が抜けてしまい、化合物層が消失してしまう。 (Third processing method)
In the first step, the surface of the steel material is carburized at a temperature of about 900 ° C to 1000 ° C. In the second step, nitriding is performed to form a compound layer by cooling from a carburizing temperature of about 900 ° C. to 1000 ° C. to a nitriding temperature of about 500 ° C. to 580 ° C. In the third step, after nitriding, quenching is performed by heating to about the A1 transformation point or higher (for example, 830 ° C to 850 ° C). In this case, since the heating in the third step requires time for heating the furnace, nitrogen is released from the compound layer formed in the second step, and the compound layer disappears.
　つぎに、本発明の実施形態に係る摺動部材の組織形態について説明する。 Next, the organizational form of the sliding member according to the embodiment of the present invention will be described.
　前記摺動部材においては、母材の外面領域に表面層の最外表面に窒化層が形成されている。窒化層は、ε相（Ｆｅ２～３Ｎ）、γ’相（Ｆｅ４Ｎ）、又はε相とγ’相との複合層を含む。これらの相は、低摩擦でかつ焼戻し軟化抵抗の高いという特性を有する。 In the sliding member, a nitride layer is formed on the outermost surface of the surface layer in the outer surface region of the base material. The nitrided layer includes an ε phase (Fe 2-3 N), a γ'phase (Fe 4 N), or a composite layer of an ε phase and a γ'phase. These phases have the characteristics of low friction and high temper softening resistance.
　窒化層と母材の中心部との間には、浸炭層が形成されている。浸炭層の少なくとも一部は、マルテンサイト層（マルテンサイト組織）である。 A carburized layer is formed between the nitrided layer and the center of the base metal. At least a part of the carburized layer is a martensite layer (martensite structure).
　マルテンサイト層は、浸炭焼入れにより生成された硬化層であり、高面圧に耐え得る。
マルテンサイト層は、数百μｍ以上に及んでいる。 The martensite layer is a hardened layer produced by carburizing and quenching and can withstand high surface pressure.
The martensite layer extends over several hundred μm.
　また、窒化層と前記マルテンサイト層との間には、両者の成分である窒素と炭素との濃度が連続的に変化している傾斜層が形成されている。傾斜層は、耐剥離性に優れ、焼戻し軟化抵抗も高い組織を有する。 Further, between the nitrided layer and the martensite layer, an inclined layer is formed in which the concentrations of nitrogen and carbon, which are the components of both, are continuously changed. The inclined layer has a structure having excellent peel resistance and high temper softening resistance.
　上記の組織を構成するための第一の方法は、炭素鋼などに浸炭した浸炭鋼または軸受け鋼を、窒化ガスの雰囲気下で、高周波誘導加熱又は通電加熱で、Ａ１変態点以上の温度、例えば、７５０℃～８５０℃程度に数分以下で加熱し、１分程度保持し、最外表面に化合物層を形成し、焼入れを行う工程を有する。なお、ここでいうＡ１変態点は、浸炭層のＡ１変態点を意味する（以下同じ。）。 The first method for constructing the above structure is to heat a carburized steel or a bearing steel carburized in carbon steel or the like by high frequency induction heating or energization heating in an atmosphere of nitride gas to a temperature equal to or higher than the A1 transformation point, for example. , 750 ° C to 850 ° C for several minutes or less, held for about 1 minute, a compound layer is formed on the outermost surface, and quenching is performed. The A1 transformation point referred to here means the A1 transformation point of the carburized layer (the same applies hereinafter).
　化合物層を形成する間に、一部の窒素は、炭素鋼などに浸炭した浸炭鋼または軸受け鋼内部に拡散し、窒素および炭素の両成分が連続的に変化する傾斜層も形成される。また、焼入れを行うことで、数百μｍ以上の深さまでマルテンサイト変態を起こし、硬化する。 During the formation of the compound layer, some nitrogen diffuses into the carburized steel or the bearing steel that has been carburized in carbon steel or the like, and an inclined layer in which both nitrogen and carbon components change continuously is also formed. Further, by quenching, martensitic transformation occurs to a depth of several hundred μm or more, and the material is cured.
　窒素ガスは、加熱前から充填しても、７５０℃～８５０℃程度に加熱されてから充填してもよい。ここで、７５０℃～８５０℃程度の窒化は、高窒化ポテンシャルで実施しないと、窒素の拡散が優勢となり、表面に窒素濃度の高い化合物層が生成されず、窒素濃度の低い浸窒層しか形成されない。高窒化ポテンシャルでの窒化は、窒化ガスであるアンモニアを１×１０４Ｐａから大気圧の範囲で、かつ、アンモニアの濃度が２０％から１００％の高濃度で行うことが望ましい。温度、アンモニア圧力およびアンモニア濃度が幅を持つのは、各条件の組合せで化合物層を得るための好適な条件が存在するためである。 Nitrogen gas may be filled before heating or after being heated to about 750 ° C to 850 ° C. Here, if nitriding at about 750 ° C. to 850 ° C. is not performed with a high nitriding potential, the diffusion of nitrogen becomes predominant, a compound layer having a high nitrogen concentration is not formed on the surface, and only an immersion layer having a low nitrogen concentration is formed. Not done. For nitriding at a high nitriding potential, it is desirable to carry out nitriding of ammonia, which is a nitriding gas, in the range of 1 × 10 4 Pa to atmospheric pressure, and the concentration of ammonia is as high as 20% to 100%. The temperature, ammonia pressure, and ammonia concentration have a range because there are suitable conditions for obtaining a compound layer in each combination of conditions.
　上記の組織を構成するための第二の方法は、炭素鋼などに浸炭した浸炭鋼または軸受け鋼を、窒化ガスの雰囲気下で、高周波誘導加熱又は通電加熱で、６００℃以上Ａ１変態点未満の温度に数分以下で加熱し、１分から３０分程度保持し、最外表面に化合物層を形成し、Ａ１変態点以上の温度、例えば８００℃から８５０℃程度に、高周波誘導加熱又は通電加熱で、１分以下で加熱し、速やかに焼入れを行う工程を有する。 The second method for constructing the above structure is to heat the carburized steel or the bearing steel carburized in carbon steel or the like by high frequency induction heating or energization heating in the atmosphere of nitride gas at 600 ° C. or higher and lower than the A1 transformation point. Heat to a temperature of several minutes or less, hold for about 1 to 30 minutes, form a compound layer on the outermost surface, and raise the temperature above the A1 transformation point, for example, about 800 ° C to 850 ° C, by high-frequency induction heating or energization heating. It has a step of heating in 1 minute or less and promptly quenching.
　化合物層を形成する間、および、Ａ１変態点以上の温度、例えば８００℃から８５０℃程度に加熱する間に、一部の窒素は、炭素鋼などに浸炭した浸炭鋼または軸受け鋼の内部に拡散し、傾斜層も形成される。また、焼入れを行うことで、数百μｍ以上の深さまでマルテンサイト変態を起こし、硬化する。 During the formation of the compound layer and during heating to a temperature above the A1 transformation point, for example, about 800 ° C. to 850 ° C., some nitrogen diffuses into the carburized steel or the bearing steel carburized in carbon steel or the like. However, a sloping layer is also formed. Further, by quenching, martensitic transformation occurs to a depth of several hundred μm or more, and the material is cured.
　窒素ガスは、加熱前から充填しても、６００℃以上Ａ１変態点未満の温度に加熱されてから充填してもよい。ここで、化合物層を形成した後においては、Ａ１変態点以上の温度、例えば８００℃から８５０℃程度への加熱は、急速に行わないと、化合物層の窒素が分解して雰囲気中に放出されたり、母材の内部に拡散したりして、化合物層の性質を低下させたり、化合物層が消失したりするため、１分以下で加熱することが望ましい。 Nitrogen gas may be filled before heating or after being heated to a temperature of 600 ° C. or higher and lower than the A1 transformation point. Here, after the compound layer is formed, if the temperature above the A1 transformation point, for example, heating from 800 ° C. to 850 ° C. is not rapidly performed, the nitrogen in the compound layer is decomposed and released into the atmosphere. It is desirable to heat it in 1 minute or less because it may diffuse into the base material and deteriorate the properties of the compound layer or the compound layer may disappear.
　また、６００℃以上Ａ１変態点未満の温度における窒化は、高窒化ポテンシャルで実施しないと、窒素の拡散が優勢となり、窒素濃度の高い化合物層が生成されず、窒素濃度の低い浸窒層しか形成されない。高窒化ポテンシャルでの窒化は、窒化ガスであるアンモニアを０．１×１０４Ｐａから大気圧の範囲で、かつ、アンモニアの濃度が１０％から１００％の高濃度で行うことが望ましい。温度、アンモニア圧力およびアンモニア濃度が幅を持つのは、各条件の組合せで化合物層を得るための好適な条件が存在するためである。 Further, if nitriding at a temperature of 600 ° C. or higher and lower than the A1 transformation point is not carried out at a high nitriding potential, the diffusion of nitrogen becomes dominant, a compound layer having a high nitrogen concentration is not formed, and only an immersion layer having a low nitrogen concentration is formed. Not done. For nitriding at a high nitriding potential, it is desirable to carry out nitriding of ammonia, which is a nitriding gas, in the range of 0.1 × 10 4 Pa to atmospheric pressure, and the concentration of ammonia is as high as 10% to 100%. The temperature, ammonia pressure, and ammonia concentration have a range because there are suitable conditions for obtaining a compound layer in each combination of conditions.
　まとめると、焼入れ工程は、浸炭層のＡ１変態点以上の温度で行うことが望ましい。 In summary, it is desirable that the quenching process be performed at a temperature equal to or higher than the A1 transformation point of the carburized layer.
　窒化処理工程をＡ１変態点未満の温度で行った場合は、焼入れ工程は、Ａ１変態点以上の温度に加熱して行うことが望ましい。 When the nitriding process is performed at a temperature lower than the A1 transformation point, it is desirable that the quenching process be performed by heating to a temperature equal to or higher than the A1 transformation point.
　焼入れ工程をＡ１変態点以上の温度に加熱をして行う場合には、当該加熱は、窒化層における窒素の分解を抑制する昇温速度で行うことが望ましい。この場合の昇温速度は、１００℃／分以上であることが望ましい。 When the quenching step is performed by heating to a temperature equal to or higher than the A1 transformation point, it is desirable that the heating is performed at a heating rate that suppresses the decomposition of nitrogen in the nitrided layer. In this case, the rate of temperature rise is preferably 100 ° C./min or higher.
　以下、実施例について詳細に説明する。なお、実質的に同一又は類似の構成には同一の符号を付し、説明が重複する場合には、その説明を省略する場合がある。また、本明細書においては、試験片等の固体材料に含まれる炭素、窒素等の濃度については、質量基準で表している。 Hereinafter, examples will be described in detail. It should be noted that substantially the same or similar configurations are designated by the same reference numerals, and if the explanations are duplicated, the explanations may be omitted. Further, in the present specification, the concentrations of carbon, nitrogen, etc. contained in solid materials such as test pieces are expressed on a mass basis.
　本実施例における試験片の処理は、次のようにして行った。 The processing of the test piece in this example was performed as follows.
　クロムモリブデン鋼ＳＣＭ４３５の丸棒試験片を母材として用いた。この丸棒試験片は、炭素濃度が約０．３５％であり、寸法は直径１０ｍｍ×長さ１０ｍｍである。 A round bar test piece of chrome molybdenum steel SCM435 was used as a base material. This round bar test piece has a carbon concentration of about 0.35% and dimensions of 10 mm in diameter × 10 mm in length.
　この丸棒試験片を高周波誘導加熱により約１分で９５０℃まで加熱し、その温度を保持する。すなわち、昇温速度は、１００℃／分以上である。９５０℃に到達した後、浸炭ガスであるアセチレンを供給し、炭素濃度が０．８％、有効効果深さ（ビッカース硬さで５５０Ｈｖ以上となる表面からの硬化深さ）が１ｍｍとなるように真空浸炭処理を施して浸炭層を形成した。なお、このように浸炭層を形成した材料を「浸炭材」と呼ぶことにし、このように前処理として浸炭処理を施した材料を「母材」と呼んでもよい。このように、母材は、その中心部まで浸炭されている必要はない。 This round bar test piece is heated to 950 ° C in about 1 minute by high frequency induction heating, and the temperature is maintained. That is, the rate of temperature rise is 100 ° C./min or higher. After reaching 950 ° C, acetylene, which is a carburized gas, is supplied so that the carbon concentration is 0.8% and the effective effect depth (hardening depth from the surface where the Vickers hardness is 550 Hv or more) is 1 mm. A carburized layer was formed by vacuum carburizing. The material on which the carburized layer is formed in this way may be referred to as a "carburized material", and the material subjected to the carburized treatment as a pretreatment in this way may be referred to as a "base material". Thus, the base metal does not need to be carburized to its center.
　つぎに、高周波誘導加熱およびアセチレン供給を停止し、不活性ガスで強制冷却しながら８５０℃まで約１分で降温し、真空排気した後、窒化ガスである１００％アンモニアガスを供給して９×１０４Ｐａに約３０秒で復圧し、１分間保持して化合物層を形成した。
その後、アンモニアを排気し、不活性ガスで置換した後に、焼入れを行った。これにより、浸炭層をマルテンサイト組織化した。焼戻しは、１８０℃で３０分実施した。 Next, stop the high-frequency induction heating and acetylene supply, lower the temperature to 850 ° C in about 1 minute while forcibly cooling with an inert gas, evacuate, and then supply 100% ammonia gas, which is a nitride gas, 9 ×. The pressure was restored to 104 Pa in about 30 seconds and held for 1 minute to form a compound layer.
Then, ammonia was exhausted, replaced with an inert gas, and then quenched. As a result, the carburized layer was organized into martensite. Tempering was carried out at 180 ° C. for 30 minutes.
　この結果、浸炭層は、試験片の最外表面からの深さが１．０ｍｍ以上の範囲までマルテンサイト層と変化した。これにより、ヘルツの最大せん断応力に起因する内部損傷に対する耐久性が得られる。 As a result, the carburized layer changed from the martensite layer to a depth of 1.0 mm or more from the outermost surface of the test piece. This provides durability against internal damage due to the maximum shear stress in Hertz.
　図１は、上記の処理により得られた試験片の断面組織の透過型電子顕微鏡画像（ＴＥＭ画像）を示したものである。 FIG. 1 shows a transmission electron microscope image (TEM image) of the cross-sectional structure of the test piece obtained by the above treatment.
　本図から、試験片の断面には、次の三つの層が存在することがわかる。すなわち、化合物層１（窒化層）、傾斜層２及び浸炭層３である。 From this figure, it can be seen that the cross section of the test piece has the following three layers. That is, the compound layer 1 (nitriding layer), the inclined layer 2, and the carburized layer 3.
　言い換えると、母材の外面領域には、最外表面から順に、化合物層１、傾斜層２、浸炭層３が積層され、これらの三つの層が表面層を形成している。 In other words, the compound layer 1, the inclined layer 2, and the carburized layer 3 are laminated in order from the outermost surface on the outer surface region of the base metal, and these three layers form the surface layer.
　当該三つの層のそれぞれをこのように呼ぶ理由は、次のとおりである。 The reason for calling each of the three layers in this way is as follows.
　図２は、図１に示す断面組織を電子線マイクロアナライザにより分析した結果を示したものである。 FIG. 2 shows the results of analysis of the cross-sectional structure shown in FIG. 1 by an electron beam microanalyzer.
　図２に示す二つのグラフは、窒素及び炭素の濃度分布を示したものである。 The two graphs shown in FIG. 2 show the concentration distribution of nitrogen and carbon.
　本図の窒素の濃度分布のグラフから、最外表面から深さ約７μｍまでの範囲に、窒素濃度が約８％のε相（Ｆｅ２～３Ｎ）が形成され、その内側の厚さ約１μｍの領域に、窒素濃度が約５．９％のγ’相（Ｆｅ４Ｎ）が形成されていることがわかる。ε相及びγ’相が化合物層１である。なお、窒素濃度は、Ｆｅ２Ｎの場合は１１．１％、Ｆｅ３Ｎの場合は７．７％となる。 From the graph of nitrogen concentration distribution in this figure, an ε phase (Fe 2-3 N) with a nitrogen concentration of about 8% is formed in the range from the outermost surface to a depth of about 7 μm, and the inner thickness is about about 7 It can be seen that a γ'phase (Fe 4 N) having a nitrogen concentration of about 5.9% is formed in the region of 1 μm. The ε phase and the γ'phase are the compound layer 1. The nitrogen concentration is 11.1% in the case of Fe 2N and 7.7% in the case of Fe 3N .
　化合物層１の内側においては、厚さ約１μｍの領域で急峻な窒素濃度の低下が見られる。そして、深さ約９μｍから内部に向かって、窒素濃度が緩やかに低下する領域がある。 Inside the compound layer 1, a steep decrease in nitrogen concentration is observed in a region having a thickness of about 1 μm. Then, there is a region where the nitrogen concentration gradually decreases from a depth of about 9 μm toward the inside.
　一方、炭素の濃度分布のグラフから、深さ約８μｍから約２１μｍまでの範囲においては、炭素濃度が徐々に増加していることがわかる。そして、深さ約２５μｍより内側においては、炭素濃度がほぼ一定値（約０．８％）となっている。 On the other hand, from the graph of carbon concentration distribution, it can be seen that the carbon concentration gradually increases in the range from about 8 μm to about 21 μm in depth. The carbon concentration is almost constant (about 0.8%) inside the depth of about 25 μm.
　本図の左側の画像に示された状態も加味して、深さ約８μｍから約２１μｍまでの範囲を傾斜層２と呼び、それよりも深い領域を浸炭層３と呼ぶことにする。 Taking into account the state shown in the image on the left side of this figure, the range from a depth of about 8 μm to about 21 μm is called the inclined layer 2, and the region deeper than that is called the carburized layer 3.
　まとめると、表面層は、窒素濃度が５．９～１１．１％の窒化鉄を含む窒化層（化合物層１）を含み、かつ、窒化層と母材の中心部との間に位置する浸炭層３を含む。ここで、母材の中心部とは、試験片のうち、表面層に覆われた内側の領域をいう。なお、浸炭層３の少なくとも一部は、マルテンサイト層である。 In summary, the surface layer contains a nitrided layer (compound layer 1) containing iron nitride having a nitrogen concentration of 5.9 to 11.1%, and is carburized located between the nitrided layer and the central portion of the base metal. Includes layer 3. Here, the central portion of the base metal refers to the inner region of the test piece covered with the surface layer. At least a part of the carburized layer 3 is a martensite layer.
　また、傾斜層２は、窒化層とマルテンサイト層との間に形成された、両者（窒化層及びマルテンサイト層）の成分である窒素と炭素との濃度が連続的に変化している領域である。更に具体的には、傾斜層２は、窒素濃度が母材の中心部に向かうに従って減少し、かつ、炭素濃度が母材の中心部に向かうに従って増加する構成を有する。 Further, the inclined layer 2 is a region formed between the nitrided layer and the martensite layer in which the concentrations of nitrogen and carbon, which are components of both (nitrided layer and martensite layer), are continuously changed. be. More specifically, the inclined layer 2 has a structure in which the nitrogen concentration decreases toward the center of the base metal and the carbon concentration increases toward the center of the base metal.
　図３は、図１に示す断面組織を電子線後方散乱回折により相同定をした結果を示したものである。 FIG. 3 shows the results of phase identification of the cross-sectional structure shown in FIG. 1 by electron backscatter diffraction.
　本図に示すように、最外表面から内部に向かって、ε相（Ｆｅ２～３Ｎ）、γ’相（Ｆｅ４Ｎ）、α相（フェライト）が形成されている。 As shown in this figure, an ε phase (Fe 2-3 N), a γ'phase (Fe 4 N), and an α phase (ferrite) are formed from the outermost surface toward the inside.
　図４は、断面硬度の測定結果を示すグラフである。横軸に最外表面からの距離（深さ）、縦軸にビッカース硬さＨｖ０．２（硬度）をとっている。 FIG. 4 is a graph showing the measurement result of the cross-sectional hardness. The horizontal axis is the distance (depth) from the outermost surface, and the vertical axis is the Vickers hardness Hv0.2 (hardness).
　上述のとおり、化合物層１及び傾斜層２の厚さは、合計でも３０μｍ弱であるため、硬度は、大部分浸炭層３の硬度を測定していることになる。浸炭層の硬度は、表面近くで約８００Ｈｖであり、５５０Ｈｖ以上の有効硬化深さは、約１ｍｍである。 As described above, since the total thickness of the compound layer 1 and the inclined layer 2 is a little less than 30 μm, the hardness is mostly measured for the hardness of the carburized layer 3. The hardness of the carburized layer is about 800 Hv near the surface, and the effective curing depth of 550 Hv or more is about 1 mm.
　図７は、本実施例における試験片の処理工程、すなわち摺動部材の製造方法をまとめて示したものである。 FIG. 7 collectively shows the processing process of the test piece in this embodiment, that is, the manufacturing method of the sliding member.
　本図に示すように、摺動部材の製造方法は、鋼材等の材料を所定の温度まで非常に短い時間で加熱することができる高周波誘導加熱（Ｓ１１０）を施す。そして、アセチレン等の浸炭ガスを供給して材料の表面の炭素濃度を増加させる真空浸炭処理（Ｓ１２０）を施す。つぎに、アンモニア等の窒化ガスを供給して化合物層を形成する窒化処理（Ｓ１３０）を施す。その後、焼入れ（Ｓ１４０）及び焼戻し（Ｓ１５０）を行う。 As shown in this figure, as a method for manufacturing a sliding member, high frequency induction heating (S110) capable of heating a material such as a steel material to a predetermined temperature in a very short time is applied. Then, a vacuum carburizing treatment (S120) is performed in which a carburizing gas such as acetylene is supplied to increase the carbon concentration on the surface of the material. Next, a nitriding treatment (S130) is performed in which a nitriding gas such as ammonia is supplied to form a compound layer. After that, quenching (S140) and tempering (S150) are performed.
　本実施例においては、実施例１と同様にして、丸棒試験片の処理を行い、浸炭層を形成した。 In this example, the round bar test piece was treated in the same manner as in Example 1 to form a carburized layer.
　その後、高周波誘導加熱およびアセチレン供給を停止し、不活性ガスで強制冷却しながら６３０℃まで約５分で降温し、真空排気した後、窒化ガスである１００％アンモニアガスを供給して６×１０４Ｐａに約３０秒で復圧し、３分間保持して化合物層を形成した。
その後、アンモニアを排気し、不活性ガスで置換した後に、高周波加熱（高周波誘導加熱）による焼入れを行い、９００℃まで加熱した。これにより、浸炭層をマルテンサイト組織化した。焼戻しは、１８０℃で３０分実施した。 After that, the high-frequency induction heating and acetylene supply were stopped, the temperature was lowered to 630 ° C. in about 5 minutes while forcibly cooling with an inert gas, and after vacuum exhausting, 100% ammonia gas, which is a nitride gas, was supplied to 6 × 10. The pressure was restored to 4 Pa in about 30 seconds and held for 3 minutes to form a compound layer.
Then, after exhausting the ammonia and replacing it with an inert gas, it was quenched by high frequency heating (high frequency induction heating) and heated to 900 ° C. As a result, the carburized layer was organized into martensite. Tempering was carried out at 180 ° C. for 30 minutes.
　本実施例においても、実施例１と同等の組織および硬度を確認した。 In this example as well, the same structure and hardness as in Example 1 were confirmed.
　図８は、本実施例における試験片の処理工程、すなわち摺動部材の製造方法をまとめて示したものである。 FIG. 8 collectively shows the processing process of the test piece in this embodiment, that is, the manufacturing method of the sliding member.
　本図に示すように、摺動部材の製造方法は、鋼材等の材料を所定の温度まで非常に短い時間で加熱することができる高周波誘導加熱（Ｓ２１０）を施す。そして、アセチレン等の浸炭ガスを供給して材料の表面の炭素濃度を増加させる真空浸炭処理（Ｓ２２０）を施す。つぎに、アンモニア等の窒化ガスを供給して化合物層を形成する窒化処理（Ｓ２３０）を施す。その後、高周波焼入れ（Ｓ２４０）及び焼戻し（Ｓ２５０）を行う。 As shown in this figure, as a method for manufacturing a sliding member, high frequency induction heating (S210) capable of heating a material such as a steel material to a predetermined temperature in a very short time is applied. Then, a vacuum carburizing treatment (S220) is performed in which a carburizing gas such as acetylene is supplied to increase the carbon concentration on the surface of the material. Next, a nitriding treatment (S230) is performed in which a nitriding gas such as ammonia is supplied to form a compound layer. Then, induction hardening (S240) and tempering (S250) are performed.
　軸受け鋼ＳＵＪ２の丸棒試験片を母材として用いた。この丸棒試験片は、炭素濃度が約１％であり、寸法は直径１０ｍｍ×長さ１０ｍｍである。ここで、この母材を「軸受鋼材」と呼ぶことにする。 A round bar test piece of bearing steel SUJ2 was used as a base material. This round bar test piece has a carbon concentration of about 1% and has dimensions of 10 mm in diameter × 10 mm in length. Here, this base material will be referred to as "bearing steel material".
　この丸棒試験片を、窒化ガスである１００％アンモニアガスを供給して圧力９×１０４Ｐａとし、高周波加熱により８５０℃まで約１分で昇温し、１分間保持して化合物層を形成した。この処理は、高周波窒化処理と呼ぶことができる。この場合の昇温速度は、１００℃／分以上である。また、窒化処理工程は、高周波誘導加熱を用いて行う、ということもできる。 This round bar test piece was supplied with 100% ammonia gas, which is a nitride gas, to a pressure of 9 × 10 4 Pa, heated to 850 ° C. in about 1 minute by high frequency heating, and held for 1 minute to form a compound layer. did. This process can be called a high frequency nitriding process. The temperature rising rate in this case is 100 ° C./min or more. It can also be said that the nitriding treatment step is performed by using high frequency induction heating.
　その後、アンモニアを排気し、不活性ガスで置換した後に、焼入れを行った。これにより、浸炭層をマルテンサイト組織化した。焼戻しは、１８０℃で３０分実施した。 After that, ammonia was exhausted, replaced with an inert gas, and then quenched. As a result, the carburized layer was organized into martensite. Tempering was carried out at 180 ° C. for 30 minutes.
　本実施例においても、実施例１と同等の組織および硬度を確認した。 In this example as well, the same structure and hardness as in Example 1 were confirmed.
　軸受け鋼ＳＵＪ２の丸棒試験片を母材として用いた。この丸棒試験片は、炭素濃度が約１％であり、寸法は直径１０ｍｍ×長さ１０ｍｍである。 A round bar test piece of bearing steel SUJ2 was used as a base material. This round bar test piece has a carbon concentration of about 1% and has dimensions of 10 mm in diameter × 10 mm in length.
　この丸棒試験片を、窒化ガスである１００％アンモニアガスを供給して圧力６×１０４Ｐａとし、高周波加熱により６３０℃まで約１分で昇温し、３分間保持して化合物層を形成した。その後、アンモニアを排気し、不活性ガスで置換した後に、高周波加熱による焼入れを行った。これにより、浸炭層をマルテンサイト組織化した。焼戻しは、１８０℃で３０分実施した。 This round bar test piece was supplied with 100% ammonia gas, which is a nitride gas, to a pressure of 6 × 10 4 Pa, heated to 630 ° C. in about 1 minute by high frequency heating, and held for 3 minutes to form a compound layer. did. Then, ammonia was exhausted, replaced with an inert gas, and then quenched by high-frequency heating. As a result, the carburized layer was organized into martensite. Tempering was carried out at 180 ° C. for 30 minutes.
　本実施例においても、実施例１と同等の組織および硬度を確認した。 In this example as well, the same structure and hardness as in Example 1 were confirmed.
　（往復摺動摩耗試験）
　本発明の効果を確認するため、従来法により作製した試験片と実施例１～４の試験片とについて、摩擦係数及び焼付き荷重の測定を行った。ここで、従来法とは、高周波加熱を用いないで、浸炭、窒化又は浸炭窒化の処理を施す方法をいう。 (Reciprocating sliding wear test)
In order to confirm the effect of the present invention, the friction coefficient and the seizure load were measured for the test pieces prepared by the conventional method and the test pieces of Examples 1 to 4. Here, the conventional method refers to a method of performing carburizing, nitriding or carburizing nitriding without using high frequency heating.
　従来法の浸炭（従来浸炭）は、次のようにして行った。 The conventional method of carburizing (conventional carburizing) was performed as follows.
　実施例１と同様の丸棒試験片を、真空浸炭炉において約６０分で９５０℃まで加熱し、その温度を保持する。９５０℃に到達した後、浸炭ガスであるアセチレンを供給し、炭素濃度が０．８％、有効効果深さが１ｍｍとなるように約５時間の真空浸炭処理を施して焼入れを行い、浸炭層を形成した。 The same round bar test piece as in Example 1 is heated to 950 ° C in about 60 minutes in a vacuum carburizing furnace, and the temperature is maintained. After reaching 950 ° C, acetylene, which is a carburized gas, is supplied, and the carburized layer is quenched by vacuum carburizing for about 5 hours so that the carbon concentration is 0.8% and the effective effect depth is 1 mm. Was formed.
　従来法の窒化（従来窒化）は、次のようにして行った。 The conventional method of nitriding (conventional nitriding) was performed as follows.
　実施例１と同様の丸棒試験片を、窒化炉において約６０分で５７０℃まで加熱し、その温度を保持する。５７０℃に到達した後、窒化ガスであるアンモニアを供給し、窒素濃度が約８％となるように約３時間の窒化処理を施して、窒化層を形成した。 The same round bar test piece as in Example 1 is heated to 570 ° C in about 60 minutes in a nitriding furnace, and the temperature is maintained. After reaching 570 ° C., ammonia as a nitriding gas was supplied, and nitriding treatment was performed for about 3 hours so that the nitrogen concentration became about 8% to form a nitrided layer.
　従来法の浸炭窒化（従来浸炭窒化）は、次のようにして行った。 The conventional method of carburizing nitriding (conventional carburizing nitriding) was performed as follows.
　実施例１と同様の丸棒試験片を、真空浸炭炉において約６０分で９５０℃まで加熱し、その温度を保持する。９５０℃に到達した後、浸炭ガスであるアセチレンを供給し、炭素濃度が０．８％、有効効果深さが１ｍｍとなるように約５時間の真空浸炭処理を施して、浸炭層を形成した。その後、窒素に、窒化ガスであるアンモニアを５ｍｏｌ％混合した混合ガスを１×１０３Ｐａの圧力を維持しながら、８５０℃まで１時間で冷却し、浸炭窒化層を形成した。その後、焼入れを行った。 A round bar test piece similar to that in Example 1 is heated to 950 ° C. in about 60 minutes in a vacuum carburizing furnace, and the temperature is maintained. After reaching 950 ° C., acetylene, which is a carburizing gas, was supplied and vacuum carburized for about 5 hours so that the carbon concentration was 0.8% and the effective effect depth was 1 mm to form a carburized layer. .. Then, a mixed gas in which 5 mol% of ammonia, which is a nitride gas, was mixed with nitrogen was cooled to 850 ° C. in 1 hour while maintaining a pressure of 1 × 10 3 Pa to form a carburized nitrided layer. After that, quenching was performed.
　摩擦係数及び焼付き荷重の測定は、往復摺動摩耗試験機を用いて実施した。 The friction coefficient and seizure load were measured using a reciprocating sliding wear tester.
　図５は、往復摺動摩耗試験機の要部を示す模式図である。 FIG. 5 is a schematic diagram showing a main part of the reciprocating sliding wear tester.
　本図に示すように、摩擦試験片４及び摩擦試験相手材５を試験機に設置し、固定する。
摩擦試験相手材５の上に潤滑油６を塗布し、摩擦試験相手材５を上昇させ、摩擦試験片４と接触させる。この状態で、摩擦試験相手材５を８０℃にヒータで加熱し、その温度を保持する。温度が８０℃に到達し、安定した後、摺動７を開始する。そして、荷重８を０．１ｋＮきざみで２分毎に上昇させ、焼付きが生じるまで試験を継続する。試験中は摩擦抵抗を測定し、摩擦抵抗の急増をもって焼付きとした。 As shown in this figure, the friction test piece 4 and the friction test mating material 5 are installed and fixed in the testing machine.
Lubricating oil 6 is applied onto the friction test mating material 5, the friction test mating material 5 is raised, and the friction test mating material 5 is brought into contact with the friction test piece 4. In this state, the friction test mating material 5 is heated to 80 ° C. with a heater to maintain the temperature. After the temperature reaches 80 ° C. and stabilizes, sliding 7 is started. Then, the load 8 is increased in 0.1 kN increments every 2 minutes, and the test is continued until seizure occurs. Friction resistance was measured during the test, and seizure was determined when the frictional resistance increased sharply.
　表１は、摩擦抵抗及び焼付き荷重の試験結果を示したものである。 Table 1 shows the test results of frictional resistance and seizure load.
　本表から、摩擦係数は、実施例１～４のいずれも、従来法で最も低い、従来法の窒化と同等であることがわかる。焼付き荷重は、実施例１～４のいずれも、従来法を大きく上回ることがわかる。 From this table, it can be seen that the coefficient of friction is equivalent to that of the conventional method, which is the lowest in all of Examples 1 to 4. It can be seen that the seizure load greatly exceeds that of the conventional method in all of Examples 1 to 4.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　（転がり疲労試験）
　さらに、転がり疲労寿命についても、実施例１～４と従来法とを比較した。 (Rolling fatigue test)
Further, regarding the rolling fatigue life, Examples 1 to 4 were compared with the conventional method.
　図６は、転がり疲労試験機の要部を示す模式図である。 FIG. 6 is a schematic diagram showing a main part of a rolling fatigue tester.
　本図に示すように、転がり試験片９及び転がり試験相手材１０を試験機に設置し、固定する。潤滑油６は、６０℃に加熱し、転がり試験片９と転がり試験相手材１０との接触部にかけ流す。この状態で、転がり試験相手材１０をモータにより１０００ＲＰＭで回転させ、転がり試験片９を別のモータにより８００ＲＰＭで回転させるとともに、接触面に荷重８を接触部の面圧が３ＧＰａとなるように負荷を加える。この状態で転がり疲労試験を継続する。そして、接触部に有意なピッチング損傷が発生した時点で試験を停止し、寿命と判断する。有意なピッチング損傷の判定は、転がり試験片９の近傍に取り付けた振動センサで検知する。 As shown in this figure, the rolling test piece 9 and the rolling test partner material 10 are installed in the testing machine and fixed. The lubricating oil 6 is heated to 60 ° C. and poured over the contact portion between the rolling test piece 9 and the rolling test mating material 10. In this state, the rolling test mating material 10 is rotated at 1000 RPM by a motor, the rolling test piece 9 is rotated at 800 RPM by another motor, and a load 8 is applied to the contact surface so that the surface pressure of the contact portion becomes 3 GPa. Add. In this state, the rolling fatigue test is continued. Then, the test is stopped when significant pitching damage occurs in the contact portion, and the life is judged. The determination of significant pitching damage is detected by a vibration sensor attached in the vicinity of the rolling test piece 9.
　表２は、転がり疲労試験の結果を示したものである。 Table 2 shows the results of the rolling fatigue test.
　本表においては、転がり疲労寿命は、従来窒化の寿命を１として比で示している。 In this table, the rolling fatigue life is shown as a ratio with the life of conventional nitriding as 1.
　従来窒化に比べ、従来浸炭が５倍、従来浸炭窒化が７倍である。 Compared to conventional nitriding, conventional carburizing is 5 times and conventional carburizing nitriding is 7 times.
　これに対して、実施例１～４はいずれも、１０倍以上であり、有意なピッチング損傷が確認されなかった。 On the other hand, in Examples 1 to 4, the number was 10 times or more, and no significant pitching damage was confirmed.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　（連続耐久試験）
　本発明の効果を確認するため、従来法である浸炭を施した減速機用の遊星歯車と、実施例１の処理を施した遊星歯車と、を同じ減速機の一段目に組み込み、５００時間の連続耐久試験を実施した。 (Continuous durability test)
In order to confirm the effect of the present invention, a planetary gear for a speed reducer subjected to carburization, which is a conventional method, and a planetary gear subjected to the treatment of Example 1 are incorporated in the first stage of the same speed reducer for 500 hours. A continuous durability test was conducted.
　試験終了後に減速機を分解し、各々の歯車の表面観察を実施した結果、従来法である浸炭を施した歯車は、表面にマイクロピッチングが多数認められたが、実施例１の処理を施した歯車には、マイクロピッチングがほとんど認められなかった。このことから、本発明の効果が確認された。 After the test was completed, the speed reducer was disassembled and the surface of each gear was observed. As a result, a large amount of micro-pitching was observed on the surface of the carburized gear, which was the conventional method, but the treatment of Example 1 was performed. Little micropitching was observed on the gears. From this, the effect of the present invention was confirmed.
　含有量０．２～０．６％の炭素（Ｃ）と、不可避の不純物と、を含み、残部が鉄（Ｆｅ）である材料を、粉末冶金により成形した試験片について、実施例１及び２と同様の処理を施して、効果を確認したところ、実施例１及び２と同等の効果が得られることが確認された。 Examples 1 and 2 are test pieces obtained by molding a material containing carbon (C) having a content of 0.2 to 0.6% and unavoidable impurities and the balance being iron (Fe) by powder metallurgy. When the same treatment as in the above was performed and the effect was confirmed, it was confirmed that the same effect as in Examples 1 and 2 was obtained.
　すなわち、本実施例においては、母材を粉末冶金により形成した。 That is, in this embodiment, the base metal was formed by powder metallurgy.
　浸炭鋼や軸受け鋼と同等の炭素濃度を有する合金を金属三次元プリンタで造形した。すなわち、母材を金属三次元プリンタにより形成した。その後、実施例１及び２と同様の処理を施して、効果を確認したところ、実施例１及び２と同等の効果が得られることが確認された。 An alloy with a carbon concentration equivalent to that of carburized steel or bearing steel was molded with a metal three-dimensional printer. That is, the base material was formed by a metal three-dimensional printer. Then, when the same treatment as in Examples 1 and 2 was performed and the effect was confirmed, it was confirmed that the same effect as in Examples 1 and 2 was obtained.
　なお、浸炭材の浸炭層の炭素濃度は、０．５％以上が望ましく、０．７％以上が更に望ましい。また、当該炭素濃度は、２．０％以下が望ましく、１．５％以下が更に望ましい。 The carbon concentration of the carburized layer of the carburized material is preferably 0.5% or more, and more preferably 0.7% or more. The carbon concentration is preferably 2.0% or less, and more preferably 1.5% or less.
　また、窒化層の窒素濃度は、０．５％以上が望ましく、上限値としてはＦｅ２Ｎの場合に相当する１１．１％以下が望ましい。下限値としては、０．７％以上が更に望ましい。 Further, the nitrogen concentration of the nitrided layer is preferably 0.5% or more , and the upper limit value is preferably 11.1% or less, which corresponds to the case of Fe 2N. The lower limit is more preferably 0.7% or more.
　１：化合物層、２：傾斜層、３：浸炭層、４：摩擦試験片、５：摩擦試験相手材、６：潤滑油、７：摺動、８：荷重、９：転がり試験片、１０：転がり試験相手材。 1: Compound layer 2: Inclined layer 3: Carburized layer 4: Friction test piece 5: Friction test mating material, 6: Lubricating oil, 7: Sliding, 8: Load, 9: Rolling test piece, 10: Rolling test partner material.

Claims (13)

  1. 　母材の外面領域に表面層を形成した構成を有し、
    　前記表面層は、窒素濃度が質量基準で５．９～１１．１％の窒化鉄を含む窒化層を含み、かつ、前記窒化層と前記母材の中心部との間に位置する浸炭層を含み、
    　前記浸炭層の少なくとも一部は、マルテンサイト層であり、
    　前記窒化層と前記マルテンサイト層との間には、両者の成分である窒素と炭素との濃度が連続的に変化している傾斜層が形成されている、摺動部材。     It has a structure in which a surface layer is formed in the outer surface region of the base material.
    The surface layer includes a nitride layer containing iron nitride having a nitrogen concentration of 5.9 to 11.1% on a mass basis, and is a carburized layer located between the nitride layer and the central portion of the base metal. Including,
    At least a part of the carburized layer is a martensite layer.
    A sliding member in which an inclined layer in which the concentrations of nitrogen and carbon, which are components of both, are continuously changed is formed between the nitrided layer and the martensite layer.
  2. 　前記窒化層は、ε相（Ｆｅ２～３Ｎ）、γ’相（Ｆｅ４Ｎ）、又は前記ε相と前記γ’相との複合層を含む、請求項１記載の摺動部材。 The sliding member according to claim 1, wherein the nitrided layer includes an ε phase (Fe 2 to 3 N), a γ'phase (Fe 4 N), or a composite layer of the ε phase and the γ'phase.
  3. 　前記母材は、浸炭材又は軸受鋼材である、請求項１記載の摺動部材。 The sliding member according to claim 1, wherein the base material is a carburized material or a bearing steel material.
  4. 　前記傾斜層は、前記窒素の前記濃度が前記母材の前記中心部に向かうに従って減少し、かつ、前記炭素の前記濃度が前記母材の前記中心部に向かうに従って増加する構成を有する、請求項１記載の摺動部材。 The inclined layer has a configuration in which the concentration of the nitrogen decreases toward the center of the base material and increases toward the center of the base material of the carbon. 1. The sliding member according to 1.
  5. 　前記浸炭層は、前記表面層の最外表面からの深さが１．０ｍｍ以上の範囲まで前記マルテンサイト層で構成されている、請求項１記載の摺動部材。 The sliding member according to claim 1, wherein the carburized layer is composed of the martensite layer up to a depth of 1.0 mm or more from the outermost surface of the surface layer.
  6. 　母材の外面領域に窒化層及び浸炭層を含む表面層を形成することにより摺動部材を製造する方法であって、
    　前記母材を高周波誘導加熱により所定の温度まで加熱する高周波処理工程と、
    　窒化ガスを供給して前記窒化層を形成する窒化処理工程と、
    　焼入れ工程と、を含み、
    　前記窒化層は、窒素濃度が質量基準で５．９～１１．１％の窒化鉄を含み、
    　前記浸炭層は、前記窒化層と前記母材の中心部との間に位置し、
    　前記浸炭層の少なくとも一部は、マルテンサイト層であり、
    　前記窒化層と前記マルテンサイト層との間には、両者の成分である窒素と炭素との濃度が連続的に変化している傾斜層が形成されている、摺動部材の製造方法。     A method for manufacturing a sliding member by forming a surface layer including a nitrided layer and a carburized layer in the outer surface region of the base metal.
    A high-frequency treatment step of heating the base material to a predetermined temperature by high-frequency induction heating,
    A nitriding process of supplying a nitriding gas to form the nitriding layer,
    Including the quenching process,
    The nitrided layer contains iron nitride having a nitrogen concentration of 5.9 to 11.1% on a mass basis.
    The carburized layer is located between the nitrided layer and the central portion of the base metal, and is located between the nitrided layer and the central portion of the base metal.
    At least a part of the carburized layer is a martensite layer.
    A method for manufacturing a sliding member, wherein an inclined layer in which the concentrations of nitrogen and carbon, which are components of both, are continuously changed is formed between the nitrided layer and the martensite layer.
  7. 　前記窒化処理工程は、前記高周波誘導加熱を用いて行う、請求項６記載の摺動部材の製造方法。 The method for manufacturing a sliding member according to claim 6, wherein the nitriding treatment step is performed by using the high frequency induction heating.
  8. 　前記焼入れ工程は、前記浸炭層のＡ１変態点以上の温度で行う、請求項６記載の摺動部材の製造方法。 The method for manufacturing a sliding member according to claim 6, wherein the quenching step is performed at a temperature equal to or higher than the A1 transformation point of the carburized layer.
  9. 　前記窒化処理工程を前記Ａ１変態点未満の温度で行った場合は、前記焼入れ工程は、前記Ａ１変態点以上の温度に加熱して行う、請求項８記載の摺動部材の製造方法。 The method for manufacturing a sliding member according to claim 8, wherein when the nitriding treatment step is performed at a temperature lower than the A1 transformation point, the quenching step is performed by heating to a temperature equal to or higher than the A1 transformation point.
  10. 　前記焼入れ工程を前記Ａ１変態点以上の温度に加熱をして行う場合には、当該加熱は、前記窒化層における窒素の分解を抑制する昇温速度で行う、請求項９記載の摺動部材の製造方法。 The sliding member according to claim 9, wherein when the quenching step is performed by heating to a temperature equal to or higher than the A1 transformation point, the heating is performed at a heating rate that suppresses the decomposition of nitrogen in the nitrided layer. Production method.
  11. 　前記昇温速度は、１００℃／分以上である、請求項１０記載の摺動部材の製造方法。 The method for manufacturing a sliding member according to claim 10, wherein the temperature rising rate is 100 ° C./min or more.
  12. 前記母材を粉末冶金により形成する工程を更に含む、請求項６記載の摺動部材の製造方法。 The method for manufacturing a sliding member according to claim 6, further comprising a step of forming the base metal by powder metallurgy.
  13. 　前記母材を金属三次元プリンタにより形成する工程を更に含む、請求項６記載の摺動部材の製造方法。 The method for manufacturing a sliding member according to claim 6, further comprising a step of forming the base material by a metal three-dimensional printer.
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WO2017154964A1 (en) * 2016-03-08 2017-09-14 アイシン・エィ・ダブリュ株式会社 Steel component, gear component, and method for manufacturing steel component
JP2019196540A (en) * 2018-05-11 2019-11-14 山陽特殊製鋼株式会社 Steel for shaft bearing excellent in rolling fatigue life under hydrogen intrusion environment

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