JP2017088958A - Rolling slide member and manufacturing method therefor, rolling shaft bearing - Google Patents

Abstract

A rolling/sliding member that can be manufactured at low cost and that can ensure a long rolling contact fatigue life even in a use environment of 200 to 300° C., a method for manufacturing the same, and a rolling bearing are provided. SOLUTION: C 0.15 to 0.45% by mass, Si 0.5% by mass or less, Mn 0.4 to 1.5% by mass, Cr 0.3 to 2.0% by mass, and Mo 0.1 to 0.35% by mass and V 0.2 to 0.4 mass % and Al 0.005 to 0.1 mass % are subjected to carbonitriding quenching treatment and tempering treatment at 200 to 300°C. As a result, the surface layer of the steel material is made into a carbonitrided layer, and Cr compounds, Mo compounds, V compounds, Cr--Mo--V compounds and nitrides precipitate in the range of up to 50 μm from the surface of the polished rolling and sliding surface. A rolling/sliding member having a particle area ratio of 5 to 15% and a Vickers hardness of at least 680 at a depth of 50 µm from the surface is obtained. [Selection drawing] Fig. 2

Description

  The present invention relates to a rolling sliding member, a manufacturing method thereof, and a rolling bearing provided with the rolling sliding member.

  Rolling sliding members such as inner and outer rings of rolling bearings and rolling elements used in transportation equipment, industrial machinery, etc., are rolling contact surfaces that make a relative or rolling contact with the mating member. have. In addition, along with high performance and miniaturization of transportation equipment, industrial machinery, etc., bearings are often used in harsh environments such as high speed conditions and high surface pressure conditions. In such an environment, the operating temperature of the bearing becomes high. Therefore, the bearing is required to have a long rolling fatigue life even under high temperature conditions (for example, about 300 ° C.).

  Further, as a steel material used for the rolling sliding member, by using a steel material having a silicon content of 0.5 to 2.0 mass% and a molybdenum content of 0.3 to 2.5 mass%, 150 It has been proposed to ensure a rolling fatigue life in a temperature range of ˜250 ° C. (Patent Document 1).

JP 2003-306743 A

  However, since the steel material described in Patent Document 1 contains silicon, it is difficult to process, and the manufacturing cost of the rolling sliding member may increase.

  The present invention has been made in view of such a situation, and can be manufactured at a low cost, and can be secured at a rolling fatigue life that can ensure a long rolling fatigue life even under a use environment of 200 to 300 ° C. It aims at providing a moving member, its manufacturing method, and a rolling bearing.

  The rolling sliding member of the present invention is a rolling sliding member having a polished rolling sliding surface that makes a rolling contact or a sliding contact or a contact including both contacts relative to a counterpart member, 0.15-0.45 mass%, manganese 0.4-1.5 mass%, silicon 0.5 mass% or less, chromium 0.3-2.0 mass%, molybdenum 0.1-0 The surface layer of a steel material containing .35% by mass, vanadium 0.2 to 0.4% by mass, and aluminum 0.005 to 0.1% by mass is made of a base material that is a carbonitriding layer, The surface layer in the range from the surface of the moving surface to 50 μm is a precipitate particle having a particle size of 0.01 to 0.1 μm made of a chromium compound, a precipitate particle having a particle size of 0.01 to 0.1 μm made of a molybdenum compound, Particle size 0.01 to 0.1 μm made of vanadium compound Including precipitate particles, precipitate particles having a particle size of 0.01 to 0.1 μm made of a chromium-molybdenum-vanadium composite compound, and precipitate particles having a particle size of 0.01 to 0.1 μm made of iron nitride, from the surface An area ratio of the precipitate particles at a depth of 50 μm is 5 to 15%, and a Vickers hardness at a depth of 50 μm from the surface is at least 680.

  The rolling sliding member of the present invention comprises a base material in which the surface layer of the steel material having the above composition is a carbonitriding layer, and the surface layer in the range from the surface of the rolling sliding surface to 50 μm is composed of a chromium compound. Precipitate particles having a diameter of 0.01 to 0.1 μm, precipitate particles having a particle diameter of 0.01 to 0.1 μm made of a molybdenum compound, precipitate particles having a particle diameter of 0.01 to 0.1 μm made of a vanadium compound, chromium -Including precipitate particles having a particle size of 0.01 to 0.1 µm made of molybdenum-vanadium composite compound and precipitate particles having a particle size of 0.01 to 0.1 µm made of iron nitride, and having a depth of 50 µm from the surface The area ratio of the precipitate particles at the position is 5 to 15%, and the Vickers hardness at the position of a depth of 50 μm from the surface is at least 680. Therefore, the rolling sliding member of the present invention can ensure sufficient hardness to obtain a long rolling fatigue life even in a use environment of 200 to 300 ° C. Moreover, the steel material which has the said composition is low-cost, and is excellent in workability. Therefore, the rolling sliding member of the present invention can be manufactured at low cost, and a long rolling fatigue life can be ensured even under a use environment of 200 to 300 ° C.

  In the rolling sliding member of the present invention, the carbon content in the surface layer is preferably 0.7 to 1.2% by mass. Moreover, in the rolling sliding member of this invention, it is preferable that the nitrogen content in the said surface layer is 0.15-0.6 mass%. In this case, a longer rolling fatigue life can be obtained in a use environment of 200 to 300 ° C.

The method of manufacturing a rolling sliding member according to the present invention is a method of manufacturing a rolling sliding member having a polished rolling sliding surface that makes a rolling contact, a sliding contact, or a contact including both contacts relative to a mating member. A method,
Carbon 0.15-0.45 mass%, manganese 0.4-1.5 mass%, silicon 0.5 mass% or less, chromium 0.3-2.0 mass%, molybdenum 0.1 Carbon potential of 1.1 to 0.35 mass%, a shape material formed from a steel material containing vanadium 0.2 to 0.4 mass% and aluminum 0.005 to 0.1 mass%. A carbonitriding and quenching step of performing quenching after heating and holding at 860 to 900 ° C. in a carbonitriding atmosphere having an ammonia concentration of 1 to 5% by volume and
It includes a tempering step of tempering the shaped material after the carbonitriding and quenching step at 200 to 300 ° C.

  The rolling sliding member manufacturing method of the present invention is a carbon nitride atmosphere having a carbon potential of 1.1 to 1.25 and an ammonia concentration of 1 to 5% by volume with respect to a shaped material formed of a steel material having the above composition. In order to perform the carbonitriding quenching process in which quenching is performed after heating and maintaining at 860 to 900 ° C. and the tempering process in which tempering is performed at 200 to 300 ° C., a rolling sliding member having the above-described excellent effects is obtained. Can do.

  A rolling bearing according to the present invention includes an inner ring having a raceway portion on an outer peripheral surface, an outer ring having a raceway portion on an inner peripheral surface, and a plurality of rolling elements disposed between both raceway portions of the inner and outer rings. In the rolling bearing, at least one of the inner ring, the outer ring, and the rolling element is the above-described rolling sliding member. Therefore, since the rolling bearing of the present invention includes the above-described rolling sliding member, the above-described excellent effects can be obtained.

  According to the rolling sliding member, the manufacturing method thereof, and the rolling bearing provided with the rolling sliding member of the present invention, a long rolling fatigue life can be ensured.

It is principal part sectional drawing which shows the ball bearing which is an example of the rolling bearing which concerns on one Embodiment of this invention. It is process drawing which shows each process of the manufacturing method of the outer ring which is a rolling sliding member which concerns on one Embodiment of this invention. It is process drawing which shows each process of the modification of the manufacturing method of the outer ring which is a rolling sliding member which concerns on one Embodiment of this invention. 3 is a diagram showing heat treatment conditions in Example 1. FIG. It is a diagram which shows the heat processing conditions in Example 2. FIG. 6 is a diagram showing heat treatment conditions in Example 3. FIG. It is a diagram which shows the heat processing conditions in Example 4. FIG. It is a diagram which shows the heat processing conditions in Example 5. FIG. It is a diagram which shows the heat processing conditions in Example 6. FIG. It is a diagram which shows the heat processing conditions in Example 7. FIG. It is a diagram which shows the heat processing conditions in the comparative example 1. It is a diagram which shows the heat processing conditions in the comparative example 2. It is a diagram which shows the heat processing conditions in the comparative example 3. It is a diagram which shows the heat processing conditions in the comparative example 4. It is a diagram which shows the heat processing conditions in the comparative example 5. In Experiment 2, it is a graph which shows the result of having investigated the relationship between tempering temperature and Vickers hardness.

[Rolling bearings]
Hereinafter, a rolling bearing and a rolling sliding member according to an embodiment of the present invention will be described with reference to the accompanying drawings. Hereinafter, a ball bearing will be described as an example of a rolling bearing. FIG. 1 is a cross-sectional view of a main part showing a ball bearing which is an example of a rolling bearing according to an embodiment of the present invention.

  A ball bearing 1 shown in FIG. 1 includes an outer ring 10, an inner ring 20 arranged concentrically with the outer ring 10 on the inner peripheral side of the outer ring 10, and a plurality of rolling elements (balls) arranged between the outer inner rings 10 and 20. 30) and a holder 40 for holding the plurality of balls 30.

  In the ball bearing 1 shown in FIG. 1, each of the outer inner rings 10 and 20 and the ball 30 is a rolling sliding member according to an embodiment of the present invention described later. In the present invention, at least one of the outer inner rings 10 and 20 and the balls 30 may be a rolling sliding member according to an embodiment of the present invention described later.

[Rolling sliding member]
An outer ring raceway portion 11 a on which a plurality of balls 30 roll is formed on the inner peripheral surface of the outer ring 10 as a rolling sliding member according to the present embodiment. The outer ring raceway portion 11a is a rolling sliding surface that makes a rolling contact, a sliding contact, or a contact including both contacts relative to the ball 30 as a counterpart member. Note that the outer ring raceway portion 11a, the end surface 11b, the shoulder surface 11c, and the outer peripheral surface 11d of the outer ring 10 are polished portions subjected to polishing finishing.
Further, an inner ring raceway portion 21a on which the plurality of balls 30 roll is formed on the outer peripheral surface of the inner ring 20 as the rolling sliding member according to the present embodiment, facing the outer ring raceway portion 11a. The inner ring raceway portion 21a is a rolling sliding surface that makes rolling contact, sliding contact, or contact including both contacts relative to the ball 30 that is the counterpart member. The raceway portion 21a, the end surface 21b, the shoulder surface 21c, and the inner peripheral surface 21d of the inner ring 20 are polished portions that have been polished.
The surface of the ball 30 as a rolling sliding member according to the present embodiment is a rolling sliding that makes a rolling contact, a sliding contact, or a contact including both contacts relative to each of the outer and inner rings 10 and 20 that are counterpart members. Surface.

  In the present embodiment, the outer ring 10 is made of a base material 10a in which the surface layer of the steel material 10a1 is a carbonitriding layer 10a2. The inner ring 20 is made of a base material 20a whose surface layer of the steel material 20a1 is a carbonitriding layer 20a2. Although not shown, the balls 30 are also made of a base material whose surface layer is a carbonitriding layer.

  In the present specification, the “carbonitriding layer” refers to a layer having a carbon content of 0.7 to 1.2% by mass and a nitrogen content of 0.15 to 0.6% by mass. The carbonitriding layers in the carbonitriding layers 10a2 and 20a2 and the balls 30 can be formed by subjecting a steel material having the above composition to a carbonitriding process described later.

  The steel materials are carbon 0.15-0.45 mass%, manganese 0.4-1.5 mass%, silicon 0.5 mass% or less, and chromium 0.3-2.0 mass%, respectively. And 0.1 to 0.35% by mass of molybdenum, 0.2 to 0.4% by mass of vanadium, and 0.005 to 0.1% by mass of aluminum. The balance of the steel material is iron and inevitable impurities. The inevitable impurities mean substances that are mixed in from raw materials and the like when manufacturing steel materials, and are allowed within a range that does not impair the object of the present invention. Examples of the inevitable impurities include copper, nickel, aluminum, phosphorus, sulfur, nitrogen, oxygen and the like. Since the outer and inner rings 10 and 20 and the balls 30 are made of steel having the above composition, they can be easily processed at a low cost during manufacture.

  Carbon is an element for ensuring the hardenability of the steel material during the production of the rolling sliding member, ensuring sufficient hardness, and obtaining internal hardness for ensuring strength. The content of carbon contained in the steel material is 0.15% by mass or more, preferably 0.18% by mass or more, more preferably 0.2% by mass from the viewpoint of sufficiently leaving undissolved carbide in the steel material. % Or more, more preferably 0.3% by mass or more, still more preferably 0.35% by mass or more, and still more preferably 0.38% by mass or more, and a viewpoint of sufficiently obtaining workability before carbonitriding and quenching. To 0.45% by mass or less, preferably 0.42% by mass or less.

  Silicon is an element necessary for deoxidation during refining of steel. The content of silicon contained in the steel material is 0.5% by mass or less, preferably 0.35 from the viewpoint of ensuring sufficient workability and reducing material cost and processing cost before carbonitriding and quenching. It is below mass%.

  Manganese is an element for enhancing the hardenability of the steel material during the production of the rolling sliding member and ensuring sufficient hardness. The content of manganese contained in the steel material is 0.4% by mass or more, preferably 0.45% by mass or more, from the viewpoint of increasing the hardenability of the steel material and ensuring sufficient hardness, and an excess of the base material. From the viewpoint of suppressing an increase in hardness and suppressing a decrease in tool life at the time of cutting during the production of a rolling sliding member, it is 1.5% by mass or less, preferably 1.3% by mass or less, more preferably 1 It is at most mass%, more preferably at most 0.75 mass%.

  Chromium is an element for improving the hardenability of the steel material during the production of the rolling sliding member and improving the hardness by forming fine precipitates during the carbonitriding and quenching process by the combined addition of vanadium and molybdenum. . The content of chromium contained in the steel material is from the viewpoint of enhancing the hardenability of the steel material during the production of the rolling rail member and improving the hardness by forming fine precipitates during the carbonitriding and quenching treatment. 3% by mass or more, preferably 0.5% by mass or more, and from the viewpoint of suppressing the formation of coarse precipitates as a starting point of fatigue fracture and reducing the material cost and processing cost, preferably 2% by mass or less, preferably It is 1.8 mass% or less.

  Molybdenum is an element for improving the hardenability of the steel material in the same manner as chromium and for improving the hardness by forming fine precipitates during carbonitriding and quenching treatment by the combined addition of vanadium and chromium. Molybdenum has a strong affinity for carbon. Before carbonitriding and quenching, a large amount of molybdenum is precipitated in the steel as insoluble carbides. The undissolved carbide serves as a precipitation nucleus during carbonitriding and quenching. Therefore, molybdenum exhibits the effect of increasing the amount of precipitates after carbonitriding and quenching. The content of molybdenum contained in the steel material is 0.1% by mass or more, preferably 0.2% by mass or more, from the viewpoint of improving hardness, and suppresses the formation of coarse precipitates that become the starting point of fatigue fracture. In addition, from the viewpoint of reducing material cost and processing cost, it is 0.35 mass% or less, preferably 0.3 mass% or less.

  Vanadium, like chromium and molybdenum, is an element for improving the hardenability of the steel material and forming fine precipitates during the carbonitriding and quenching treatment by the combined addition of chromium and molybdenum to improve the hardness. Vanadium has a strong affinity for carbon. The content of vanadium contained in the steel material is 0.2% by mass or more, preferably 0.21% by mass or more, more preferably 0.22% by mass or more from the viewpoint of improving hardness, and a sufficient amount From the viewpoints of suppressing the formation of coarse precipitates that inhibit solid solution of carbon and reducing the material cost and processing cost, it is 0.4% by mass or less, preferably 0.38% by mass or less, more preferably 0.8% by mass. It is 36 mass% or less.

  Aluminum is an element for performing deoxidation in the smelting process at the time of manufacturing steel materials. The content of aluminum contained in the steel material is 0.005% by mass or more, preferably 0.01% by mass or more, and the rolling fatigue of the rolling sliding member is suppressed by suppressing the remaining coarse oxide in the base material. From the viewpoint of suppressing the decrease in the life, it is 0.1% by mass or less, preferably 0.05% by mass or less.

  The surface layers in the range from the surfaces (rolling sliding surfaces) of the raceway portions 11a and 21a of the outer and inner rings 10 and 20 and the balls 30 to 50 μm are precipitate particles made of a chromium compound and having a particle size of 0.01 to 0.1 μm. Precipitate particles made of molybdenum compound with a particle size of 0.01 to 0.1 μm, precipitate particles made of vanadium compound with a particle size of 0.01 to 0.1 μm, and particles made of chromium-molybdenum-vanadium composite compound. It includes precipitate particles having a particle diameter of 0.01 to 0.1 μm and comprising precipitate particles having a diameter of 01 to 0.1 μm and iron nitride. In the present specification, the “surface layer in the range from the surface to 50 μm” means the layer in the range between the surface of the rolling sliding surface and the depth of 50 μm from the surface of the rolling sliding surface. Say.

  In this specification, the “chromium compound” is a general term for chromium carbide, chromium nitride, and chromium carbonitride. The “molybdenum compound” is a general term for molybdenum carbide, molybdenum nitride, and molybdenum carbonitride. The “vanadium compound” is a general term for vanadium carbide, vanadium nitride, and vanadium carbonitride. The “chromium-molybdenum-vanadium composite compound” means a carbide containing at least two selected from the group consisting of chromium, molybdenum and vanadium, a nitride containing at least two, and a carbonitriding containing at least two. A general term for things.

  The particle diameter of the precipitate particles is 0.01 μm or more, preferably 0.02 μm or more from the viewpoint of sufficiently carrying out precipitation strengthening, and preferably 0.1 μm or less, preferably from the viewpoint of dispersion strengthening by the Orowan mechanism. 0.08 μm or less.

  From the viewpoint of dispersion strengthening by the Orowan mechanism, the area ratio of the precipitate particles is 50 μm deep from the surfaces (rolling sliding surfaces) of the raceways 11a and 21a of the outer inner rings 10 and 20 and the balls 30. It is 5% or more, preferably 7% or more, and from the viewpoint of ensuring a sufficient solid solution amount of carbon and ensuring sufficient hardness, it is 15% or less, preferably 13% or less. In the present specification, the “area ratio of precipitate particles” means from precipitate particles having a particle size of 0.01 to 0.1 μm made of a chromium compound in a surface layer in a range from the surface to 50 μm, and a molybdenum compound. A precipitate particle having a particle size of 0.01 to 0.1 μm, a precipitate particle having a particle size of 0.01 to 0.1 μm made of a vanadium compound, and a particle size of 0.01 to 0.1 μm made of a chromium-molybdenum-vanadium composite compound. It refers to the area ratio of a combination of 0.1 [mu] m precipitate particles and precipitate particles made of iron nitride and having a particle size of 0.01 to 0.1 [mu] m.

  The Vickers hardness (hereinafter also referred to as “surface Vickers hardness”) at a depth of 50 μm from the surface of each of the raceway portions 11a, 21a and the balls 30 of the outer inner rings 10, 20 is 200 to 300 ° C. in the use environment. From the viewpoint of securing a sufficient rolling fatigue life of 680 or more. In addition, the Vickers hardness in the position of the depth of 50 micrometers from each surface of the track | orbit parts 11a and 21a and the ball | bowl 30 of the outer inner rings 10 and 20 is 740 or less normally. As described above, the outer inner rings 10 and 20 and the balls 30 have a Vickers hardness of at least 680 at a depth of 50 μm from the surface. Therefore, even in a use environment of 200 to 300 ° C., long rolling A fatigue life can be secured. The surface Vickers hardness is determined by applying a Vickers indenter at a depth of 50 μm from the surface of the rolling sliding surface after cutting the rolling sliding member from the surface of the rolling sliding surface in the depth direction. It is a measured value.

  The carbon content in the surface layer in the range from the surfaces of the raceway portions 11a, 21a and balls 30 of the outer inner rings 10, 20 to the ball 30 to 10 μm ensures a sufficient amount of solid solution and amount of precipitates in the matrix and high surface hardness. From the standpoint of ensuring, it is preferably 0.7% by mass or more, more preferably 0.8% by mass or more, and coarse precipitates of carbides in the surface layer (for example, precipitates having a particle size exceeding 0.1 μm). From the viewpoint of further improving the life by reducing the abundance of this, it is preferably 1.2% by mass or less, more preferably 1.1% by mass or less.

  The nitrogen content in the surface layer in the range from the surfaces of the raceway portions 11a, 21a and the balls 30 of the outer inner rings 10, 20 to 10 μm is preferably from the viewpoint of securing a sufficient amount of precipitates and ensuring high surface hardness. Is 0.15% by mass or more, more preferably 0.2% by mass or more, from the viewpoint of suppressing the generation of excessive retained austenite in the surface layer, and extending the life by setting the surface Vickers hardness to at least 680, Preferably it is 0.6 mass% or less, More preferably, it is 0.55 mass% or less.

[Production method of rolling sliding member]
The rolling sliding member according to the present embodiment includes a carbonitriding process in which carbonitriding is performed on a shaped material formed from a steel material having the above composition, and a shaped material after the carbonitriding process is performed at 200 to 300 ° C. And a tempering step in which tempering is performed.
Hereinafter, a method for manufacturing the outer ring will be described as an example of a method for manufacturing the rolling sliding member. FIG. 2 is a process diagram showing each process of the manufacturing method of the outer ring which is a rolling sliding member according to the embodiment of the present invention.

  First, the shaped member 14 of the outer ring 10 having portions corresponding to the outer ring raceway portion 11a, the end surface 11b, the shoulder surface 11c, and the outer peripheral surface 11d formed of the steel material is obtained ["Pre-processing step", FIG. 2 (a). reference〕.

Next, the obtained shaped material 14 is set in a carbonitriding furnace, and the shaped material 14 is subjected to a carbonitriding and quenching process [“carbonitriding and quenching step”, FIG. 2 (b)]. By such carbonitriding and quenching treatment, a carbonitriding layer (not shown) can be formed, sufficient surface hardness can be ensured, and temper softening resistance can be improved.
The carbonitriding and quenching treatment is performed for 4 hours or more at a carbonitriding temperature of 860 to 900 ° C. in an atmosphere (carbonitriding atmosphere) having a carbon potential of 1.1 to 1.25 and an ammonia concentration of 1 to 5% by volume. It can be performed by heating, quenching, or the like.
The carbon potential of the carbonitriding atmosphere is 1.1 or more from the viewpoint of securing a sufficient surface hardness, and 1.25 or less from the viewpoint of suppressing the formation of coarse carbides.
The ammonia concentration in the carbonitriding atmosphere is 1% by volume or more from the viewpoint of ensuring sufficient surface hardness and improving the temper softening resistance of the steel material, and is controlled to prevent excessive nitrogen penetration into the steel material. From the viewpoint of securing the amount of carbon, it is 5% by volume or less.
The carbonitriding temperature is 860 ° C. or more from the viewpoint of obtaining a sufficient diffusion rate of carbon and nitrogen, and from the viewpoint of extending the life of the carbonitriding furnace while reducing the amount of carbonitriding gas used in the carbonitriding atmosphere. 900 ° C. or lower.
The carbonitriding time is usually 4 hours or longer from the viewpoint of obtaining a carburizing depth sufficient for strengthening the surface layer.
The rapid cooling is performed by, for example, oil cooling in a cooling oil bath.

Then, after heating to 200-300 degreeC tempering temperature with respect to the shaping | molding material 14 after a carbonitriding and quenching process, the tempering process which air-cools is given, and an intermediate material is obtained ["tempering process", FIG.2 (c). ].
The temperature at the time of tempering is 200 ° C. or higher, preferably 250 ° C. or higher, from the viewpoint of sufficiently ensuring the dimensional stability in a use environment of 200 to 300 ° C. From the viewpoint of securing the dynamic fatigue life, it is 300 ° C. or lower.
The tempering time is 0.5 hour or more, preferably 1 hour or more from the viewpoint of stabilizing the quality of the rolling sliding member by suppressing the occurrence of temperature unevenness. In the present specification, the “tempering time” refers to the time from the start of heating until the work reaches a predetermined temperature until the air cooling is started.

  The intermediate material after the tempering step is subjected to polishing finishing processing on the portions forming the outer ring raceway portion 11a, the end surface 11b, and the outer peripheral surface 11d to obtain a rolling sliding member (outer ring 10) ["finishing processing", FIG. 2 (d)].

When the surface hardness of the rolling sliding member is further improved, as shown in FIG. 3, subzero is applied between the carbonitriding and quenching step [FIG. 3 (b)] and the tempering step [FIG. 3 (d)]. Processing [“sub-zero processing step”, FIG. 3 (c)] may be performed. In this case, the pre-processing [FIG. 3A], the carbonitriding and quenching step and the tempering step can be performed in the same manner as the method shown in FIG.
In the sub-zero treatment step, sub-zero treatment is performed to cool the outer ring shaped material 14 after the carbonitriding and quenching treatment to a predetermined temperature of less than 0 ° C.
The cooling temperature in the sub-zero treatment is preferably −100 ° C. or higher from the viewpoint of reducing costs, and preferably −50 ° C. or lower from the viewpoint of changing the retained austenite to a predetermined martensite.
The cooling time in the sub-zero treatment is preferably 0.5 hours or more from the viewpoint of suppressing the occurrence of temperature unevenness and stabilizing the quality of the rolling sliding member.

  Next, the effects of the rolling sliding member and the manufacturing method thereof according to an embodiment of the present invention will be verified by examples and the like.

Examples 1-7 and Comparative Examples 1-5
As steel materials, carbon 0.15-0.45 mass%, manganese 0.4-1.5 mass%, silicon 0.5 mass% or less, chromium 0.3-2.0 mass%, molybdenum 0 0.1 to 0.35% by mass, vanadium 0.2 to 0.4% by mass and aluminum 0.005 to 0.1% by mass, with the balance being iron and inevitable impurities. Steel was used.

  The steel material shown in Table 1 was processed into a predetermined shape to obtain a shaped material having an outer diameter of 40 mm and a thickness of 16.3 mm. Next, the obtained shaped material was subjected to a heat treatment and then polished to obtain test pieces of Examples 1 to 7 and Comparative Examples 1 to 5. The heat treatment conditions in Examples 1 to 7 and Comparative Examples 1 to 5 are shown in FIGS.

The heat treatment condition shown in FIG. 4 is that the raw material is heated in a carbonitriding furnace in a carbonitriding atmosphere with a carbon potential of 1.25 and an ammonia concentration of 2% by volume at 860 ° C. for 6 hours and up to 80 ° C. The conditions are such that oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is heated at 300 ° C. for 2 hours and then air-cooled (tempered) (Example 1).
The heat treatment condition shown in FIG. 5 is that the raw material is heated in a carbonitriding furnace in a carbonitriding atmosphere having a carbon potential of 1.2 and an ammonia concentration of 1% by volume at 860 ° C. for 6 hours and up to 80 ° C. The conditions are such that oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is heated at 300 ° C. for 2 hours and then air-cooled (tempered) (Example 2).
The heat treatment condition shown in FIG. 6 is that the raw material is heated in a carbonitriding furnace in a carbonitriding atmosphere having a carbon potential of 1.1 and an ammonia concentration of 4% by volume at 860 ° C. for 6 hours and up to 80 ° C. The conditions are such that oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is heated at 300 ° C. for 2 hours and then air-cooled (tempered) (Example 3).
The heat treatment conditions shown in FIG. 7 are as follows. The raw material was heated in a carbonitriding furnace in a carbonitriding atmosphere having a carbon potential of 1.1 and an ammonia concentration of 5% by volume at 860 ° C. for 6 hours and up to 80 ° C. The conditions are such that oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is heated at 300 ° C. for 2 hours and then air-cooled (tempered) (Example 4).
The heat treatment conditions shown in FIG. 8 are as follows. The raw material was heated in a carbonitriding furnace in a carbonitriding atmosphere with a carbon potential of 1.2 and an ammonia concentration of 1% by volume at 860 ° C. for 6 hours and up to 80 ° C. The conditions are such that oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is heated at 300 ° C. for 2 hours and then air-cooled (tempered) (Example 5).
The heat treatment condition shown in FIG. 9 is that the raw material is heated in a carbonitriding furnace in a carbonitriding atmosphere with a carbon potential of 1.2 and an ammonia concentration of 1% by volume at 860 ° C. for 6 hours and up to 80 ° C. The conditions are such that oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is heated at 250 ° C. for 2 hours and then air-cooled (tempered) (Example 6).
The heat treatment conditions shown in FIG. 10 are as follows. The raw material was heated in a carbonitriding furnace in a carbonitriding atmosphere having a carbon potential of 1.1 and an ammonia concentration of 4% by volume at 860 ° C. for 6 hours and up to 80 ° C. Oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is maintained at −55 ° C. for 1 hour (subzero treatment), then heated at 300 ° C. for 2 hours and then air-cooled (tempered) (implementation) Example 7).
The heat treatment conditions shown in FIG. 11 include heating the raw material in a carburizing furnace at 860 ° C. for 6 hours and oil cooling to 80 ° C. in a carburizing furnace (carburizing and quenching). The obtained shaped material was heated at 300 ° C. for 2 hours and then air-cooled (tempered) (Comparative Example 1).
The heat treatment condition shown in FIG. 12 is that the raw material is heated in a carbonitriding furnace in a carbonitriding atmosphere with a carbon potential of 1.3 and an ammonia concentration of 1% by volume at 860 ° C. for 6 hours and up to 80 ° C. Oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is heated at 300 ° C. for 2 hours and then air-cooled (tempered) (Comparative Example 2).
The heat treatment conditions shown in FIG. 13 are as follows. The raw material was heated in a carbonitriding furnace in a carbonitriding atmosphere having a carbon potential of 1.0 and an ammonia concentration of 10% by volume at 860 ° C. for 6 hours and up to 80 ° C. Oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is heated at 300 ° C. for 2 hours and then air-cooled (tempered) (Comparative Example 3).
The heat treatment condition shown in FIG. 14 is that the raw material is heated in a carbonitriding furnace in a carbonitriding atmosphere with a carbon potential of 1.2 and an ammonia concentration of 1% by volume at 860 ° C. for 6 hours and up to 80 ° C. Oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is heated at 350 ° C. for 2 hours and then air-cooled (tempered) (Comparative Example 4).
The heat treatment condition shown in FIG. 15 is that the raw material is heated in a carbonitriding furnace in a carbonitriding atmosphere with a carbon potential of 1.0 and an ammonia concentration of 10% by volume at 860 ° C. for 6 hours and up to 80 ° C. Oil cooling is performed (carbonitriding and quenching), and the obtained shaped material is maintained at −55 ° C. for 1 hour (subzero treatment), then heated at 300 ° C. for 2 hours and then air-cooled (tempered) (Comparison) Example 5).

Test example 1
Vickers hardness, surface carbon content, surface nitrogen content, kind and form of precipitate particles, and area of the precipitate particles of the surface layers of the test pieces obtained by the methods of Examples 1 to 7 and Comparative Examples 1 to 5 The rate was examined.

  The Vickers hardness of the surface layer was measured using a Vickers hardness tester after cutting in the depth direction from the surface of the test piece, applying a Vickers indenter at a depth of 50 μm from the surface of the test piece.

  The surface carbon content and the surface nitrogen content were determined by measuring the surface carbon content and the surface nitrogen content of the product obtained by embedding finish polishing after cutting each test piece in the direction perpendicular to the axial direction. Obtained by measuring with. Here, the surface carbon content and the surface nitrogen content were values in a range from the surface of the test piece to a position having a depth of 10 μm.

The type and area ratio of the precipitate particles are as follows. In the measurement field of 800 μm ² , each element was measured using EPMA under the conditions of acceleration voltage: 15 kV, irradiation current: 2.016 × 10 ⁻⁷ A, and scan magnification: 3000 times. It was observed by mapping and image processing.

When the Vickers hardness of the surface layer after tempering at 200 to 300 ° C. is 680 or more, the hardness sufficient to ensure a long life is ensured in the use environment at 200 to 300 ° C. It is considered possible. Therefore, whether or not the test pieces obtained by the methods of Examples 1 to 7 and Comparative Examples 1 to 5 are suitable for use in a use environment of 200 to 300 ° C. was evaluated according to the following criteria. The results are shown in Tables 2 and 3. In Tables 2 and 3, “M (C, N) precipitate” means chromium carbide, chromium nitride, chromium carbonitride, molybdenum carbide, molybdenum nitride, molybdenum carbonitride. Vanadium carbide, vanadium nitride, vanadium carbonitride, carbide containing at least two selected from the group consisting of chromium, molybdenum and vanadium, nitride containing at least two, and at least two It means a general term for the precipitates of carbonitrides.
(Judgment criteria)
Good: Vickers hardness after tempering at 200 to 300 ° C. is 680 or more.
Impossible: Vickers hardness after tempering at 200 to 300 ° C. is less than 680.

  From the results shown in Table 2, the raw material obtained from the steel was heated and maintained at 860 to 900 ° C. in a carbonitriding atmosphere having a carbon potential of 1.1 to 1.25 and an ammonia concentration of 1 to 5% by volume. Thereafter, a carbonitriding quenching treatment for quenching is performed, followed by a tempering treatment for tempering at 200 to 300 ° C., and a precipitate having a particle size of 0.01 to 0.1 μm made of a chromium compound at a position of 50 μm from the surface. Particles, precipitate particles made of molybdenum compound with a particle size of 0.01 to 0.1 μm, precipitate particles made of vanadium compound with a particle size of 0.01 to 0.1 μm, particle size 0 made of chromium-molybdenum-vanadium composite compound By making the area ratio of the 0.01 to 0.1 μm precipitate particles and the 0.01 to 0.1 μm precipitate particles made of iron nitride 5 to 15%, 200 to 300% Hardness use suitable for use in an environment (surface Vickers hardness 680 or higher) it can be seen that it is possible to ensure. In addition, since the carbon content is 0.7 to 1.2% by mass and the nitrogen content is 0.15 to 0.6% by mass, the range from the surface of the test piece to the position having a depth of 10 μm is carburized. It was found that a nitride layer was formed.

  On the other hand, the heat treatment conditions of Comparative Examples 1 to 5 are quenching after heating and maintaining at 860 to 900 ° C. in a carbonitriding atmosphere having a carbon potential of 1.1 to 1.25 and an ammonia concentration of 1 to 5% by volume. This is a condition deviating from the carbonitriding and quenching treatment conditions and the tempering treatment conditions for tempering at 200 to 300 ° C. Therefore, it can be seen from the results shown in Table 3 that the steel materials obtained by the methods of Comparative Examples 1 to 5 cannot obtain hardness suitable for use in a use environment of 200 to 300 ° C.

  In addition, instead of steel materials having the composition shown in Table 1, as steel materials, carbon 0.15-0.45 mass%, manganese 0.4-1.5 mass%, silicon 0.5 mass% or less , 0.3-2.0% by mass of chromium, 0.1-0.35% by mass of molybdenum, 0.2-0.4% by mass of vanadium, and 0.005-0.1% by mass of aluminum And when the other steel materials whose balance is iron and inevitable impurities are used, fine precipitates in an amount equivalent to those in Examples 1 to 7 are obtained, and therefore, steel materials having the compositions shown in Table 1 were used. It seems that the same tendency is seen.

Test example 2
The steel material shown in Table 1 was processed into a predetermined shape to obtain a shaped material having an outer diameter of 40 mm and a thickness of 16.3 mm. Next, the obtained shaped material was heated in a carbonitriding furnace in a carbonitriding atmosphere with a carbon potential of 1.25 and an ammonia concentration of 2% by volume at 860 ° C. for 6 hours and oil cooling to 80 ° C. (Carbonitriding and quenching), and the resulting shaped material was heated at a tempering temperature of 160 ° C., 180 ° C., 200 ° C., 220 ° C., 240 ° C., 260 ° C., 280 ° C. or 300 ° C. for 2 hours and then air-cooled (tempering). ). The obtained intermediate material was polished to obtain a test piece. The Vickers hardness after tempering at 200-300 degreeC of the surface layer of each obtained test piece was investigated. The Vickers hardness after tempering the surface layer at 200 to 300 ° C. is cut in the depth direction from the surface of the test piece, and then applied with a Vickers indenter at a depth of 50 μm from the surface of the test piece. It was measured using a Vickers hardness tester. FIG. 16 shows the result of examining the relationship between the tempering temperature and the Vickers hardness after tempering at 200 to 300 ° C. in Test Example 2.

  From the results shown in FIG. 16, after the carbonitriding and quenching treatment in which the carbon potential is 1.1 to 1.25 and the ammonia concentration is 1 to 5% by volume in a carbonitriding atmosphere and heated to 860 to 900 ° C. and then quenched. It can be seen that by tempering at 200 to 300 ° C., a Vickers hardness of 680 or more can be secured.

  DESCRIPTION OF SYMBOLS 1: Ball bearing, 10: Outer ring, 10a: Base material, 10a1: Steel material, 10a2: Carbonitriding layer, 11a: Outer ring raceway part, 14: Shape material, 20: Inner ring, 20a: Base material, 20a1: Steel material, 20a2 : Carbonitriding layer, 21a: inner ring raceway, 30: ball

Claims (5)

A rolling sliding member having a polished rolling sliding surface that makes a rolling contact or sliding contact or contact including both contacts relative to a counterpart member,
Carbon 0.15-0.45 mass%, manganese 0.4-1.5 mass%, silicon 0.5 mass% or less, chromium 0.3-2.0 mass%, molybdenum 0.1 The surface layer of a steel material containing 0.35% by mass, vanadium 0.2-0.4% by mass, and aluminum 0.005-0.1% by mass consists of a base material that is a carbonitriding layer,
The surface layer in the range from the surface of the rolling sliding surface to 50 μm is a precipitate particle having a particle size of 0.01 to 0.1 μm made of a chromium compound and a precipitate having a particle size of 0.01 to 0.1 μm made of a molybdenum compound. Particle, a precipitate particle having a particle size of 0.01 to 0.1 μm made of a vanadium compound, a precipitate particle having a particle size of 0.01 to 0.1 μm made of a chromium-molybdenum-vanadium composite compound, and a particle size made of iron nitride Including 0.01-0.1 μm precipitate particles,
The area ratio of the precipitate particles at a position of a depth of 50 μm from the surface is 5 to 15%,
A rolling sliding member having a Vickers hardness of at least 680 at a depth of 50 μm from the surface.   The rolling sliding member according to claim 1, wherein a carbon content in the surface layer is 0.7 to 1.2 mass%.   The rolling sliding member according to claim 1 or 2, wherein a nitrogen content in the surface layer is 0.15 to 0.6 mass%. A method of manufacturing a rolling sliding member having a rolling sliding surface having a polished finish for making a rolling contact or sliding contact or a contact including both contacts relative to a counterpart member,
Carbon 0.15-0.45 mass%, manganese 0.4-1.5 mass%, silicon 0.5 mass% or less, chromium 0.3-2.0 mass%, molybdenum 0.1 Carbon potential of 1.1 to 0.35 mass%, a shape material formed from a steel material containing vanadium 0.2 to 0.4 mass% and aluminum 0.005 to 0.1 mass%. A carbonitriding step of performing a carbonitriding and quenching treatment for quenching after heating and holding at 860 to 900 ° C. in a carbonitriding atmosphere having an ammonia concentration of 1 to 5% by volume and
A method for producing a rolling sliding member, comprising a tempering step of tempering the shaped material after the carbonitriding and quenching step at 200 to 300 ° C. A rolling bearing comprising an inner ring having a raceway portion on an outer peripheral surface, an outer ring having a raceway portion on an inner peripheral surface, and a plurality of rolling elements arranged between both raceway portions of the inner and outer rings,
A rolling bearing, wherein at least one of the inner ring, the outer ring, and the rolling element is the rolling sliding member according to any one of claims 1 to 3.