JP2018080357A - Rolling slide member, method for producing the same, steel for carbonitriding and rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling slide member that can secure a long rolling life even in a high load condition, a method for producing the same and a rolling bearing.SOLUTION: A ball bearing 1 as a rolling bearing has outer and inner rings (10,20) and a ball (30) as rolling slide members, which include substrate parts (10a1,20a1,30a1) and surface carbonitrided layers (10a2,20a2,30a2) of a composition consisting of C 0.1-0.5 mass%, Si 0.05-0.25 mass%, Mn 1.2-2.3 mass%, Ni 0.1 mass% or less, Cu 0.05 mass% or less, Cr 2.5-3.1 mass%, Mo 0.01-0.1 mass% with the balance being Fe and inevitable impurities, and satisfying formula: 47.2≤8.1Mn+13.7Cr≤61.8 and formula: 0.65≤9.2Si+29(Ni+Cu)+18.5Mo≤5.5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rolling sliding member, a manufacturing method thereof, a carbonitriding steel material, and a rolling bearing including the rolling sliding member.

  Rolling sliding members used for bearings or the like are required to have a long rolling fatigue life when used under severe usage conditions such as high load conditions. Thus, it has been proposed to ensure a long rolling fatigue life by depositing precipitates by precipitation strengthening on the surface of a steel material used for the production of rolling sliding members (see, for example, Patent Document 1). .

JP 2001-98343 A

  However, in the rolling sliding member described in Patent Document 1, when the precipitate area ratio exceeds 30%, the precipitate is likely to be a starting point of separation. Therefore, in the rolling sliding member described in Patent Document 1, the rolling fatigue life may be shortened.

  The present invention has been made in view of such a situation, and provides a rolling sliding member capable of ensuring a long rolling fatigue life even under high load conditions, a manufacturing method thereof, and a rolling bearing. Objective.

In one aspect, the present invention is a rolling sliding member having a polished rolling sliding surface that comes into relative contact with a mating member, and 0.1 to 0.5% by mass of carbon, 0.05-0.25% by mass of silicon, 1.2-2.3% by mass of manganese, 0.1% by mass or less of nickel, 0.05% by mass or less of copper, and 2.5-3.1 of chromium Containing 0.01% to 0.1% by mass of molybdenum and the balance being iron and inevitable impurities, the formula (I):
47.2 ≦ 8.1Mn + 13.7Cr ≦ 61.8 (I)
(In the formula, Mn represents the manganese content (mass%), and Cr represents the chromium content (mass%)).
And formula (II):
0.65 ≦ 9.2Si + 29 (Ni + Cu) + 18.5Mo ≦ 5.5 (II)
(In the formula, Si represents the silicon content (mass%), Ni represents the nickel content (mass%), Cu represents the copper content (mass%), and Mo represents the molybdenum content (mass%).
The present invention relates to a rolling and sliding member comprising a base portion having a composition satisfying the above and a surface carbonitriding layer. In this case, the position of the maximum orthogonal shear stress generation depth from the rolling sliding surface exists in the surface carbonitriding layer.

  The rolling sliding member of this invention contains the base | substrate part which has the said composition, and a surface carbonitriding layer. Therefore, according to the rolling sliding member of the present invention, an amount of retained austenite sufficient for strengthening the structure by stress-induced martensitic transformation can be ensured. Moreover, in the rolling sliding member of the present invention, stress-induced martensitic transformation is likely to occur. Therefore, according to the rolling sliding member of the present invention, a long rolling fatigue life can be ensured even under high load conditions.

  In the rolling sliding member of the present invention, it is preferable that the Vickers hardness Hv at a position where the maximum orthogonal shear stress generation depth is 700 to 800 from the rolling sliding surface. A rolling sliding member having such a configuration has sufficient hardness and toughness as a rolling sliding member.

  In the rolling sliding member of the present invention, the amount of retained austenite at the position of the maximum orthogonal shear stress generation depth from the rolling sliding surface is preferably 25 to 50% by volume. Moreover, it is preferable that the area ratio of the precipitate particle | grains in the position of the said maximum orthogonal shear stress generation depth from the said rolling sliding surface is 1% or less. Furthermore, it is preferable that the average particle diameter of the precipitate particles at the position of the maximum orthogonal shear stress generation depth from the rolling sliding surface is 0.4 μm or less. In a rolling sliding member having such a configuration, an amount of retained austenite sufficient for strengthening the structure due to stress-induced martensitic transformation is secured, and the occurrence of internal origin delamination is suppressed. Therefore, according to the rolling sliding member having such a configuration, a long rolling fatigue life can be ensured more reliably.

In another aspect, the present invention is a method of manufacturing a rolling sliding member having a polished and sliding sliding surface that is relatively in contact with a counterpart member,
(A) Carbon 0.1-0.5 mass%, Silicon 0.05-0.25 mass%, Manganese 1.2-2.3 mass%, Nickel 0.1 mass% or less, Copper 0 .05 mass% or less, chromium 2.5-3.1 mass%, molybdenum 0.01-0.1 mass%, the balance being iron and inevitable impurities, the formula (I):
47.2 ≦ 8.1Mn + 13.7Cr ≦ 61.8 (I)
(In the formula, Mn represents the manganese content (mass%), and Cr represents the chromium content (mass%)).
And formula (II):
0.65 ≦ 9.2Si + 29 (Ni + Cu) + 18.5Mo ≦ 5.5 (II)
(In the formula, Si represents the silicon content (mass%), Ni represents the nickel content (mass%), Cu represents the copper content (mass%), and Mo represents the molybdenum content (mass%).
Obtaining a shaped material from a steel material having a composition satisfying
(B) The raw material is heated and maintained at 850 to 980 ° C. in a carbonitriding atmosphere having a carbon potential of 1.1 to 1.5 and a ratio of the ammonia flow rate to the carburized metamorphic gas flow rate of 1 to 5%. A process of carbonitriding the shape material to obtain an intermediate material,
(C) The step of quenching by heating and holding the intermediate material after the step (B) at 830 to 870 ° C, and (D) The intermediate material after the step (C) was heated and held at 160 to 200 ° C. Then, it is related with the manufacturing method of a rolling sliding member including the process of tempering by cooling. In the method for manufacturing a rolling sliding member of the present invention, an operation of performing carbonitriding on a shaped material obtained from a steel material having the above composition is employed. As a result, at the position where the maximum orthogonal shear stress is generated from the rolling sliding surface, a sufficient amount of retained austenite is secured for toughening the structure by stress-induced martensite transformation, and a structure in which stress-induced martensite transformation is likely to occur. A structure can be formed. Therefore, it is possible to obtain a rolling sliding member that exhibits the above-described effects.

  In still another aspect, the present invention provides a steel material for carbonitriding, which has a carbon content of 0.1 to 0.5 mass%, silicon of 0.05 to 0.25 mass%, manganese 1.2 to 2.3 mass%, nickel 0.1 mass% or less, copper 0.05 mass% or less, chromium 2.5 to 3.1 mass%, molybdenum 0.01 to 0.1 mass% %, The balance being iron and inevitable impurities, and a carbonitriding steel material having a composition satisfying the above formulas (I) and (II). Since the carbonitriding steel material of the present invention has the above-described composition, the amount of retained austenite sufficient for strengthening the structure by stress-induced martensitic transformation is ensured by performing carbonitriding, and the stress It is possible to form a structure in which induced martensite transformation is likely to occur.

  In another aspect, the present invention provides an outer ring having a rolling sliding surface on the inner periphery, an inner ring having a rolling sliding surface on the outer periphery, and a plurality of rollers disposed between both rolling sliding surfaces of the outer inner ring. The rolling bearing according to claim 1, wherein at least one of the outer ring, the inner ring, and the rolling element comprises the above-described rolling sliding member. Since the rolling bearing of the present invention includes the above-described rolling sliding member, stress-induced martensitic transformation occurs with the rolling of the rolling element, and the structure on the rolling sliding surface is strengthened. Therefore, the rolling bearing of the present invention exhibits the above-described excellent operational effects.

  According to the rolling sliding member and the rolling bearing of the present invention, a long rolling fatigue life can be secured even under high load conditions.

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 a diagram which shows heat processing conditions. Example 1 is a graph showing the change over time in the maximum orthogonal shear stress generating depth z ₀ residual austenite amount of the position of the inner ring is a sliding member rolling obtained in each Comparative Example 4 and Comparative Example 8. Example 1 is a graph showing the change over time in the Vickers hardness of the maximum orthogonal shear stress generating depth z ₀ position in the inner ring is a sliding member rolling obtained in each Comparative Example 4 and Comparative Example 8.

[Explanation of terms]
In this specification, the “maximum orthogonal shear stress generation depth” refers to a depth at which the amplitude of the orthogonal shear stress generated inside the rolling sliding member is maximized. The maximum orthogonal shear stress generation depth usually varies depending on the use of the rolling sliding member, the shape of the rolling sliding member, the usage conditions of the rolling sliding member, etc., so the usage of the rolling sliding member, the rolling sliding member It can be appropriately determined according to the shape, the use conditions of the rolling sliding member, and the like. When the rolling sliding member is a constituent member of a rolling bearing, the maximum orthogonal shear stress generation depth can be determined from the size of the rolling elements that constitute the rolling bearing.

  When the rolling sliding member is a rolling element, the maximum orthogonal shear stress generation depth is usually a depth of [0.2 to 2.5% of the diameter D of the rolling element] from the rolling sliding surface of the rolling element. is there. Here, “the diameter D of the rolling element” indicates the diameter of the ball when the rolling element is a ball bearing ball. Further, “the diameter D of the rolling element” indicates the large end diameter of the roller when the rolling element is a roller of a roller bearing. When the rolling sliding member is a race ring (outer ring or inner ring), the maximum orthogonal shear stress generation depth is the [diameter D of the diameter D of the rolling element that rolls on the raceway surface of the raceway from the raceway rolling surface. 0.2 to 2.5%].

[Rolling bearings]
Hereinafter, a rolling bearing 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 disposed concentrically with the outer ring 10 on the inner peripheral side of the outer ring 10, and a plurality of rolling elements ( Ball 30) and a retainer 40 for holding a 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. In the present invention, the rolling bearing is not particularly limited, and may be other rolling bearings such as a cylindrical roller bearing and a tapered roller bearing.

[Rolling sliding member]
Hereinafter, the outer and inner rings 10 and 20 and the balls 30 of the ball bearing 1 will be described as examples of the rolling sliding member according to the present embodiment. Outer ring 10 includes a base portion 10a1 and a surface carbonitriding layer 10a2. The surface carbonitriding layer 10a2 is present on the base portion 10a1. On the inner peripheral surface of the outer ring 10, a track portion 11a on which a plurality of balls 30 roll is formed. That is, as shown in FIG. 1, the track portion 11a is formed on the surface of the surface carbonitriding layer 10a2. The surface of the track portion 11a is a rolling sliding surface. The outer ring 10 makes a contact including a rolling contact, a sliding contact, or both contacts relative to the ball 30 on the rolling sliding surface. Note that the 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.

  Inner ring 20 includes a base portion 20a1 and a surface carbonitriding layer 20a2. The surface carbonitrided layer 20a2 exists on the base portion 20a1. On the outer circumferential surface of the inner ring 20, a raceway portion 21 a is formed that faces the raceway portion 11 a and on which a plurality of balls 30 roll. That is, as shown in FIG. 1, the track portion 21a is formed on the surface of the surface carbonitriding layer 20a2. The surface of the track portion 21a is a rolling sliding surface. The inner ring 20 makes a contact including a rolling contact, a sliding contact, or both contacts relative to the ball 30 on the rolling sliding surface. 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 ball 30 includes a base portion 30a1 and a surface carbonitriding layer 30a2. The surface carbonitrided layer 30a2 is present on the base portion 30a1. The surface of the ball 30, that is, the surface of the surface carbonitriding layer 30 a 2 of the ball 30 is a rolling sliding surface. The ball 30 makes a contact including a rolling contact, a sliding contact, or both contacts relative to each of the outer inner rings 10 and 20 on the rolling sliding surface.

Base portions 10a1, 20a1, 30a1 are composed of 0.1 to 0.5% by mass of carbon, 0.05 to 0.25% by mass of silicon, 1.2 to 2.3% by mass of manganese, and 0.1% by mass of nickel. % Or less, 0.05% by mass or less of copper, 2.5 to 3.1% by mass of chromium, and 0.01 to 0.1% by mass of molybdenum, and the balance contains iron and inevitable impurities. Base portions 10a1, 20a1, 30a1 are represented by the formula (I):
47.2 ≦ 8.1Mn + 13.7Cr ≦ 61.8 (I)
(In the formula, Mn represents the manganese content (mass%), and Cr represents the chromium content (mass%)).
And formula (II):
0.65 ≦ 9.2Si + 29 (Ni + Cu) + 18.5Mo ≦ 5.5 (II)
(In the formula, Si represents the silicon content (mass%), Ni represents the nickel content (mass%), Cu represents the copper content (mass%), and Mo represents the molybdenum content (mass%).
It has the composition which satisfy | fills. The composition of the base portions 10a1, 20a1, 30a1 is the same as the composition of the carbonitriding steel material described later.

The amount of retained austenite in the structure tends to increase as Ms decreases. Further, the processing-induced transformation property from austenite to martensite tends to be higher as Md ₃₀ is higher. “Ms” means a temperature at which martensitic transformation starts during quenching and cooling. “Md ₃₀ ” means a temperature at which 50% of the structure of the steel material is transformed into martensite when a 30% tensile true strain is applied to the steel material.

The Ms is represented by the formula (III):
Ms = 550-350C-40Mn-35V-20Cr-17Ni-10Cu-10Mo-10W-0Si + 15Co (III)
(Wherein C is carbon content (mass%), Mn is manganese content (mass%), V is vanadium content (mass%), Cr is chromium content (mass%), Ni is Nickel content (mass%), Cu content copper (mass%), Mo content molybdenum (mass%), W content tungsten (mass%), Si content silicon (mass%) %), Co indicates the cobalt content (% by mass))
[Edited by Japan Heat Treatment Technology Association, "1.7 Effect of Alloying Elements on Steel", Introduction, Structure and Properties of Metallic Materials, July 2004, p. 40].

The Md ₃₀ is represented by the formula (IV):
_{Md 30 = 551-462 (C + N} ) -9.2Si-8.1Mn-13.7Cr-29 (Ni + Cu) -18.5Mo-68Nb (IV)
(Wherein C is carbon content (mass%), N is nitrogen content (mass%), Si is silicon content (mass%), Mn is manganese content (mass%), Cr is Chromium content (mass%), Ni content of nickel (mass%), Cu content of copper (mass%), Mo content of molybdenum (mass%), Nb content of niobium (mass%) %))
[Nohara Kiyohiko et al., “Composition and grain size dependence of work-induced martensitic transformation in metastable austenitic stainless steel”, Japan Iron and Steel Institute, Japan Steel Association, “Iron and Steel”, 63, No. 5, April 1, 1977, pp. 772-782].

In the formulas (III) and (IV), the inventors of the present invention are elements in which manganese and chromium have a small effect of lowering Md ₃₀ and have a large effect of lowering Ms, and silicon, nickel, copper, and molybdenum reduce Md ₃₀ . It is an element having a great effect of lowering, and carburizing a raw material obtained from a carbonitriding steel having a composition satisfying formulas (I) and (II) based on formulas (III) and (IV) It has been found that the rolling life can be extended when nitriding is performed.

  In the rolling bearing, when the rolling element rolls, the maximum orthogonal shear stress is generated inside the rolling sliding surface. At the position where the maximum orthogonal shear stress is generated in the rolling sliding member, the structure is fatigued and the strength is lowered. A tissue with reduced strength is likely to be a starting point for peeling. On the other hand, at the position of the maximum orthogonal shear stress generation depth of each of the outer inner rings 10 and 20 and the balls 30, an amount of retained austenite sufficient to strengthen the structure by stress-induced martensite transformation is secured. Further, stress-induced martensitic transformation is likely to occur at the positions of the maximum orthogonal shear stress generation depths of the outer inner rings 10 and 20 and the balls 30. Therefore, in the ball bearing 1, the structure of the outer inner rings 10, 20 and the balls 30 is strengthened at the initial stage when the balls 30 start rolling. Therefore, according to the outer inner rings 10 and 20 and the balls 30, a long rolling fatigue life can be ensured.

  The surface carbonitrided layers 10a2, 20a2, and 30a2 have a carbon content of 0.7 to 1.0 mass%, a nitrogen content of 0.1 to 0.4 mass%, and a Vickers hardness Hv of 700 to 800. It is a certain layer. The surface carbonitriding layers 10a2, 20a2, and 30a2 can be formed, for example, by performing carburizing, quenching, and tempering described later on a carbonitriding steel described later. The positions of the maximum orthogonal shear stress generation depths of the outer inner rings 10 and 20 and the balls 30 exist in the surface carbonitriding layers 10a2, 20a2 and 30a2. Therefore, at the positions of the maximum orthogonal shear stress generation depths of the outer inner rings 10 and 20 and the balls 30, it is possible to secure a sufficient amount of retained austenite for strengthening the structure by stress-induced martensitic transformation. In the surface carbonitrided layers 10a2, 20a2, and 30a2, except for the carbon content, the silicon content, the manganese content, the nickel content, the copper content, the chromium content, and the molybdenum content The remainder is the same as the composition of the base portions 10a1, 20a1, 30a1.

  The Vickers hardness Hv secures sufficient hardness as a rolling sliding member at a position where the maximum orthogonal shear stress is generated from the rolling sliding surfaces of the raceways 11a and 21a of the outer inner rings 10 and 20 and the balls 30. From the viewpoint, it is 700 or more, preferably 710 or more. The Vickers hardness is 800 or less, preferably 790 or less, from the viewpoint of securing sufficient toughness as a rolling sliding member.

  At the position where the maximum orthogonal shear stress is generated from the rolling sliding surfaces of the raceways 11a and 21a of the outer inner rings 10 and 20 and the balls 30, the amount of retained austenite is caused by stress-induced martensitic transformation during rolling of the rolling elements. From the viewpoint of strengthening the structure and improving the rolling fatigue life, it is preferably 25% by volume or more, more preferably 30% by volume or more. The amount of retained austenite is preferably 50% by volume or less, more preferably 45% by volume or less, from the viewpoint of obtaining the hardness required for a rolling bearing.

  Precipitate particles are present in the surface carbonitrided layers 10a2, 20a2, and 30a2. In the present specification, “precipitate particles” means particles made of chromium carbide, particles made of chromium nitride, particles made of chromium carbonitride, particles made of molybdenum carbide, particles made of molybdenum nitride, molybdenum charcoal. It means a generic name for particles made of nitride, particles made of chromium-molybdenum composite carbide, particles made of chromium-molybdenum composite nitride, and particles made of chromium-molybdenum composite carbonitride.

  At the position where the maximum orthogonal shear stress is generated from the rolling sliding surfaces of the raceways 11a and 21a of the outer inner rings 10 and 20 and the balls 30, the average particle diameter of the precipitate particles is separated from the internal starting point at the position. From the viewpoint of suppression, it is preferably 0.4 μm or less, more preferably 0.3 μm or less. Note that the precipitate particles may not exist. In this case, the lower limit of the average particle diameter of the precipitate particles is 0 μm. The average particle size of the precipitate particles is the total particle size of the precipitate particles existing in the field of view of the range of 1 μm × 1 μm obtained by the transmission electron microscope at the position where the maximum orthogonal shear stress is generated from the rolling sliding surface. It is the value calculated | required by measuring and calculating an average value from the obtained measured value.

  Further, at the position where the maximum orthogonal shear stress is generated from the rolling sliding surfaces of the raceway portions 11a, 21a and the balls 30 of the outer inner rings 10, 20, the area ratio of the precipitate particles is separated from the internal starting point at the position. From the viewpoint of suppression, it is preferably 1% or less. The area ratio of the precipitate particles is obtained by obtaining the area of the precipitate particles existing in the field of view of 1 μm × 1 μm range obtained by a transmission electron microscope at the position where the maximum orthogonal shear stress is generated from the rolling sliding surface. This is a value obtained by dividing the obtained area value by the area value of the visual field.

[Carbon nitrided steel]
The steel for carbonitriding according to the present embodiment has a carbon content of 0.1 to 0.5% by mass, silicon of 0.05 to 0.25% by mass, manganese of 1.2 to 2.3% by mass, nickel of 0.1% by mass. 1 mass% or less, copper 0.05 mass% or less, chromium 2.5 to 3.1 mass%, molybdenum 0.01 to 0.1 mass%, the balance being iron and inevitable impurities And having a composition satisfying the formulas (I) and (II). Since the carbonitriding steel material according to the present embodiment has the above composition, the amount of retained austenite sufficient for toughening the structure by stress-induced martensitic transformation is ensured by performing carbonitriding. In addition, it is possible to form a structure in which stress-induced martensitic transformation is likely to occur.

  Carbon is an element for ensuring the hardenability of the carbonitriding steel during the production of the rolling sliding member and obtaining the internal hardness for ensuring the strength. However, when the carbon content in the carbonitriding steel material is excessive, the rolling sliding member becomes too hard, causing a decrease in workability before heat treatment and the like. The carbon content in the steel for carbonitriding is 0.1% by mass or more, preferably 0.15% by mass or more from the viewpoint of obtaining sufficient internal hardness. In addition, the carbon content in the carbonitriding steel is 0.5% by mass or less, preferably 0.45% by mass or less, from the viewpoint of sufficiently obtaining workability before heat treatment.

  Silicon is an element for deoxidizing steel during smelting and increasing the strength of the steel. Further, when the silicon content in the carbonitriding steel material is excessive, silicon may make it difficult for stress-induced martensitic transformation of retained austenite to occur. The silicon content in the carbonitriding steel is 0.05% by mass or more, preferably 0.07% by mass or more from the viewpoint of ensuring sufficient strength. The silicon content in the carbonitriding steel is 0.25% by mass or less, preferably 0.23% by mass or less, from the viewpoint of facilitating stress-induced martensitic transformation of the retained austenite amount.

  Manganese is an element for securing the hardenability of the carbonitriding steel during the production of the rolling sliding member and obtaining the internal hardness for securing the strength. In the present embodiment, manganese is an element that increases the amount of retained austenite in the structure and hardly suppresses stress-induced martensitic transformation of retained austenite. Chromium described later increases the amount of retained austenite in the structure, but tends to produce coarse precipitate particles of nitride during the carbonitriding process. Therefore, in this embodiment, instead of increasing the content of chromium and increasing the amount of retained austenite in the structure, by increasing the manganese content, the amount of retained austenite sufficient for strengthening the structure by stress-induced martensitic transformation is increased. Secured. The manganese content in the steel for carbonitriding is 1.2 from the viewpoint of ensuring a sufficient amount of retained austenite for toughening the structure by stress-induced martensite transformation and facilitating stress-induced martensitic transformation of retained austenite. It is at least mass%, preferably at least 1.25 mass%. Further, the manganese content in the carbonitriding steel is 2.3% by mass or less, preferably 2% by mass or less from the same viewpoint.

  When the content of nickel in the carbonitriding steel material is excessive, nickel increases the amount of retained austenite in the structure, but may make stress-induced martensitic transformation of the retained austenite difficult to occur. The content of nickel in the carbonitriding steel is 0.1% by mass or less from the viewpoint of facilitating stress-induced martensitic transformation of retained austenite. Note that the carbonitriding steel does not need to contain nickel. In this case, the lower limit of the nickel content in the carbonitriding steel is 0% by mass.

  When the copper content in the carbonitriding steel material is excessive, copper increases the amount of retained austenite in the structure, but may make stress-induced martensitic transformation of the retained austenite difficult to occur. The content of copper in the carbonitriding steel is 0.05% by mass or less, preferably 0.03% by mass or less, from the viewpoint of facilitating stress-induced martensitic transformation of retained austenite. Note that the carbonitriding steel does not need to contain copper. In this case, the lower limit of the copper content in the carbonitriding steel is 0% by mass.

  Chromium is an element used for improving the hardenability of the carbonitriding steel. In this embodiment, chromium is an element that increases the amount of retained austenite in the structure and hardly suppresses stress-induced martensitic transformation of retained austenite. The chromium content in the steel for carbonitriding is 2.5 from the viewpoint of ensuring a sufficient retained austenite amount for toughening the structure by stress-induced martensite transformation and facilitating stress-induced martensite transformation of retained austenite. It is at least mass%, preferably at least 2.6 mass%. Further, the content of chromium in the carbonitriding steel is 3 from the viewpoint of suppressing the formation of precipitates such as coarse carbides, coarse nitrides, coarse carbonitrides, and preventing a decrease in rolling fatigue life. .1% by mass or less, preferably 3.0% by mass or less.

  Molybdenum is an element used for improving the hardenability of the carbonitriding steel. If the molybdenum content in the carbonitriding steel material is excessive, molybdenum may cause coarsening of precipitates. Further, when the molybdenum content in the carbonitriding steel material is excessive, molybdenum increases the amount of retained austenite in the structure, but sometimes makes stress-induced martensitic transformation of the retained austenite difficult to occur. The molybdenum content in the carbonitriding steel is 0.01% by mass or more, preferably 0.02% by mass or more, from the viewpoint of improving the hardenability of the carbonitriding steel. In addition, the molybdenum content in the carbonitriding steel is 0.1% by mass or less, preferably 0.08% by mass or less, from the viewpoint of facilitating stress-induced martensitic transformation of retained austenite.

  The inevitable impurities are substances that are inevitably mixed from raw materials and the like when manufacturing a carbonitriding steel. The inevitable impurities are substances allowed within a range that does not impair the object of the present invention. Examples of the inevitable impurities include phosphorus, sulfur, aluminum, nitrogen, oxygen, boron, niobium, and titanium, but are not particularly limited.

In formula (I), formula (Ia):
8.1 Mn + 13.7Cr (Ia)
[Mn and Cr are the same as Mn and Cr in the formula (I). ]
The value of is 47.2 or more, preferably 49 or more, from the viewpoint of securing a retained austenite amount sufficient for strengthening the structure by stress-induced martensite. In the formula (I), the value of the formula (Ia) is 61.8 or less, preferably 61.1 from the viewpoint of suppressing the excessive generation of retained austenite and securing the hardness required for the rolling bearing. It is as follows.

In formula (II), formula (IIa):
9.2Si + 29 (Ni + Cu) + 18.5Mo (IIa)
[Si, Ni, Cu and Mo are the same as Si, Ni, Cu and Mo in formula (II)]
The value of is 0.65 or more, preferably 1 or more from the viewpoint of securing the strength required for the rolling bearing. In the formula (II), the value of the formula (IIa) is 5.5 or less, preferably 4.5 or less, from the viewpoint of easily causing stress-induced martensitic transformation of retained austenite.

[Production method of rolling sliding member]
The outer inner rings 10 and 20 and the balls 30 are, for example, a pre-process for forming a shaped material formed from the carbonitriding steel material, and a carbonitriding and quenching treatment is performed on the obtained shaped material to obtain an intermediate material. It is obtained by a method including a surface hardening treatment step for obtaining a finish and a finishing step for finishing the obtained intermediate material. Hereinafter, a method for manufacturing the outer ring 10 will be described as an example of a method for manufacturing the rolling sliding member according to the present embodiment. FIG. 2 is a process diagram showing each process of a method for manufacturing an outer ring which is a rolling sliding member according to an embodiment of the present invention, and FIG. 3 is a diagram showing an example of heat treatment conditions in the surface hardening process.

  First, a shaped material 14 for the outer ring 10 formed from the carbonitriding steel material is obtained (see “Pre-processing step”, FIG. 2A). The raw material 14 has portions corresponding to the track portion 11a, the end surface 11b, the shoulder surface 11c, and the outer peripheral surface 11d.

  Next, the obtained raw material 14 is subjected to surface hardening treatment to obtain an intermediate material 15 ["surface hardening treatment step", FIG. 2 (b)]. As shown in FIG. 3, the surface hardening process includes a carbonitriding and quenching process and a tempering process. In the surface hardening treatment step, first, the raw material 14 is placed in a carbonitriding atmosphere in a carbonitriding furnace with a carbon potential of 1.1 to 1.5 and a ratio of the ammonia flow rate to the carburized metamorphic gas flow rate of 1 to 5% After carbonitriding by heating and holding at a carbonitriding temperature of 850 to 980 ° C. for 3 hours or more, heating and holding at a quenching temperature of 830 to 870 ° C. for 1 hour or less, and then oil cooling to 80 ° C. (Carbonitriding quenching process). Thereafter, the obtained shaped material 14 is tempered by holding at a tempering temperature of 160 to 200 ° C. for 0.5 to 4 hours (tempering step). Thereby, the intermediate material 15 including the base portion 10a1 and the surface carbonitriding layer 10a2 is obtained. The carbonitriding atmosphere is obtained by supplying a carburized gas and ammonia gas to a carbonitriding furnace.

  The carbon potential of the carbonitriding atmosphere is 1.1 or more, preferably from the viewpoint of ensuring the hardness suitable for the rolling sliding member and ensuring the amount of retained austenite sufficient for the toughening of the structure by the stress-induced martensitic transformation. 1.2 or more. Further, the carbon potential of the carbonitriding atmosphere is 1.5 or less, preferably 1.3 or less, from the viewpoint of suppressing the formation of coarse precipitates that are the starting point of separation.

  The ammonia flow rate relative to the carburized metamorphic gas flow rate in the carbonitriding atmosphere is 1% or more, preferably 2% or more, from the viewpoint of securing the amount of retained austenite sufficient for strengthening the structure by stress-induced martensitic transformation. In addition, the ammonia flow rate relative to the carburized metamorphic gas flow rate in the carbonitriding atmosphere is 5% or less, preferably 4% or less, from the viewpoint of suppressing the formation of coarse precipitates that are the starting point of peeling.

  The carbonitriding temperature is 850 ° C. or higher, preferably 860 ° C. or higher, from the viewpoints of ensuring toughness suitable for a rolling sliding member and shortening the processing time necessary for obtaining predetermined heat treatment properties. The carbonitriding temperature is 980 ° C. or lower, preferably 970 ° C. or lower, from the viewpoint of ensuring hardness suitable for the rolling sliding member and suppressing coarsening of the crystal grains of the precipitate particles.

  The carbonitriding time is usually preferably 3 hours or more from the viewpoint of ensuring hardness suitable for the rolling sliding member. Carbon and nitrogen tend to be widely dispersed in the carbonitriding steel as the carbonitriding time is longer. Thereby, the hardness suitable for a rolling sliding member can be ensured to a deeper position. Therefore, the carbonitriding time may be increased as necessary.

  The quenching temperature is 830 ° C. or higher, more preferably 840 ° C. or higher, from the viewpoint of securing a retained austenite amount sufficient for toughening the structure by stress-induced martensitic transformation. The quenching temperature is 870 ° C. or less, more preferably 860 from the viewpoint of improving the rolling fatigue life by adjusting the solid solution amount of carbon in the matrix of the steel material and suppressing excessive generation of retained austenite. It is below ℃.

  The holding time at the quenching temperature may be longer than the time necessary for the temperature of the entire shaped material to reach the predetermined quenching temperature. From the viewpoint of suppressing the formation of coarse precipitates and ensuring toughness suitable for a rolling sliding member, the time is preferably 1 hour or less.

  The tempering temperature is 160 ° C. or higher, preferably 170 ° C. or higher, from the viewpoint of ensuring toughness suitable for a rolling sliding member. Further, the tempering temperature is 200 ° C. or less, preferably 190 ° C. or less, from the viewpoint of ensuring hardness suitable for the rolling sliding member.

  The tempering time is 0.5 hours or more, preferably 1 hour or more, from the viewpoint of securing toughness suitable for a rolling sliding member. The tempering time is 4 hours or less, preferably 3 hours or less from the viewpoint of ensuring hardness suitable for the rolling sliding member and reducing the heat treatment cost. In the present specification, the “tempering time” refers to the time from when the raw material reaches a predetermined temperature until the start of air cooling.

  Next, a rolling sliding member (outer ring 10 is obtained by subjecting the intermediate material 15 to a polishing finishing process and, if necessary, a super-finishing process to the portions forming the raceway part 11a, the end face 11b, and the outer peripheral face 11d. (See “Finishing”, FIG. 2 (c)).

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further in detail, this invention is not limited only to this Example. The outer and inner rings and balls obtained in the following examples and comparative examples are all obtained by heat treatment under the same heat treatment conditions. Therefore, the outer ring and the inner ring having the same machining allowance at the time of polishing finishing after heat treatment have the same heat treatment properties. Therefore, the result of the test example shows the result of the inner ring as a representative result.

Examples 1-8 and Comparative Examples 1-11
The steel material shown in Table 1 was processed into a predetermined shape, and the outer ring for a deep groove ball bearing (bearing nominal number 6206) and the respective shaped material of the ball were manufactured. In Table 1, the steel materials of Examples 1 to 8 are carbon 0.1 to 0.5 mass%, silicon 0.05 to 0.25 mass%, manganese 1.2 to 2.3 mass%, nickel 0.1 mass% or less, copper 0.05 mass% or less, chromium 2.5-3.1 mass%, molybdenum 0.01-0.1 mass%, the balance being iron and inevitable It is an example of a carbonitriding steel material that is an impurity and has a composition satisfying the formulas (I) and (II). In the table, in the item “determination of formula (I)”, a white circle indicates that formula (I) is satisfied, and a cross indicates that formula (I) is not satisfied. In the table, in the item “determination of formula (II)”, a white circle indicates that formula (II) is satisfied, and a cross indicates that formula (II) is not satisfied. In the table, in the item “overall determination”, a white circle indicates that both of the formulas (I) and (II) are satisfied, and a cross indicates that at least one of the formulas (I) and (II) is not satisfied.

The obtained shaped material was subjected to heat treatment to form a surface carbonitriding layer. The heat treatment conditions are as follows.
<Heat treatment conditions>
Carbon potential CP: 1.2
Ratio of ammonia flow rate to carburized metamorphic gas flow rate: 3%
Carbonitriding temperature A: 900 ° C
Carbonitriding time t _c : 3h or more Quenching temperature B: 850 ° C
Holding time t _q at quenching temperature: 15 minutes Oil cooling: 80 ° C
Tempering temperature C: 170 ° C
Tempering time t _t : 2 hours

  The obtained intermediate material was polished and finished, and outer groove and ball for deep groove ball bearings of Examples 1 to 8 and Comparative Examples 1 to 11 were obtained. The obtained outer groove and ball for deep groove ball bearings were assembled to obtain deep groove ball bearings of Examples 1 to 8 and Comparative Examples 1 to 11.

Test example 1
About the outer inner ring used for the deep groove ball bearings obtained in Examples 1 to 8 and Comparative Examples 1 to 11, at a position of a depth of 100 μm (maximum orthogonal shear stress generation depth z ₀ ) from the rolling sliding surface. Vickers hardness Hv, amount of retained austenite at a depth of 100 μm from the rolling sliding surface, carbon content at a depth of 100 μm from the rolling sliding surface, and at a depth of 100 μm from the rolling sliding surface. Nitrogen content, precipitate area ratio at a depth of 100 μm from the rolling sliding surface, average particle diameter and rolling fatigue life of the precipitate particles at a depth of 100 μm from the rolling sliding surface (L ₁₀ life) ).

  The Vickers hardness Hv is obtained by cutting the outer and inner rings obtained in Examples 1 to 8 and Comparative Examples 1 to 11 in the depth direction from the rolling sliding surface and then indenting the indenter at a position of 100 μm from the rolling sliding surface. And measured using a Vickers hardness tester according to the method described in JIS Z 2244.

  The amount of retained austenite is determined from the martensite phase (α phase) by the X-ray diffraction method at a position 100 μm deep from the rolling sliding surface of the outer inner ring obtained in Examples 1 to 8 and Comparative Examples 1 to 11. It investigated by calculating ratio of the integrated intensity with an austenite phase (gamma phase).

  The carbon content at a depth of 100 μm from the rolling sliding surface and the nitrogen content at a depth of 100 μm from the rolling sliding surface were obtained in Examples 1 to 8 and Comparative Examples 1 to 11, respectively. After cutting in the depth direction from the rolling sliding surface of the outer outer ring thus obtained, by measuring each content in the range of ± 10 μm in the depth direction centering on the position of 100 μm depth from the rolling sliding surface Asked.

The precipitate area ratio is calculated by the formula (V):
[Precipitate area ratio]
= ([Area of precipitate particles existing in visual field in range of 1 μm × 1 μm] / [visual field area]) × 100 (V)
Calculated according to [Area of precipitate particles existing in the field of view in the range of 1 μm × 1 μm] is determined by image analysis at a position of 100 μm from the rolling sliding surface of each of the inner and outer rings of Examples 1 to 8 and Comparative Examples 1 to 11. It is the area of the precipitate particles existing in the field of view in the range of 1 μm × 1 μm obtained by a scanning electron microscope. [Viewing area] is 1 μm ² .

  The average particle diameter of the precipitate particles is a field of view in the range of 1 μm × 1 μm obtained by a transmission electron microscope at a position of 100 μm from the rolling sliding surface of the outer inner ring obtained in Examples 1 to 8 and Comparative Examples 1 to 11. The total particle size of the precipitate particles present in the sample was measured, and the average value was calculated from the obtained measured values.

The rolling fatigue life was determined by performing a rolling fatigue life test under the conditions shown in Table 2 using the deep groove ball bearings obtained in Examples 1 to 8 and Comparative Examples 1 to 11, and 10% breakage obtained from the results. was evaluated by examining the L ₁₀ life indicates the probability. The 10% failure probability was determined by plotting the results of the rolling fatigue test on Weibull probability paper.

For the outer inner ring obtained in each Examples 1 to 8 and Comparative Examples 1 to 11, in Vickers hardness Hv, the position of the maximum orthogonal shear stress generating depth z ₀ at the position of maximum orthogonal shear stress generating depth z ₀ the amount of retained austenite, the carbon content at the position of maximum orthogonal shear stress generating depth z _0, the nitrogen content at the position of maximum orthogonal shear stress generating depth z _0, at the position of the maximum orthogonal shear stress generating depth z ₀ Table 3 shows the results obtained by examining the precipitate area ratio, the average particle diameter of the precipitate particles at the position where the maximum orthogonal shear stress generation depth z ₀ is ₀ , and the rolling fatigue life (L ₁₀ life).

In the rolling sliding member obtained by performing the carbonitriding treatment, the carbon content is in the range of 0.7 to 1.0% by mass, and the nitrogen content is in the range of 0.1 to 0.4% by mass. The region is a surface carbonitriding layer. From the results shown in Table 3, it can be seen that the carbon content at the position of the maximum orthogonal shear stress generation depth z ₀ is 0.77 to 0.87 mass%. The results shown in Table 3 indicate that the nitrogen content at the position of the maximum orthogonal shear stress generation depth z ₀ is 0.14 to 0.24 mass%. Therefore, it can be seen that the position of the maximum orthogonal shear stress generation depth z0 exists in the surface carbonitriding layer.

From the results shown in Table 3, in the outer inner rings obtained in Examples 1 to 8, the Vickers hardness Hv was 734.9 to 794.0, the amount of retained austenite was 26 to 50% by volume, and the precipitation It can be seen that the material area ratio is 0.4 to 0.9%, and the average particle size of the precipitate particles is 0.19 to 0.39 μm. Further, the rolling fatigue life (L ₁₀ life) of the outer inner ring obtained in Examples 1-8, it can be seen that beyond 1300 hours.

In the steel material of Comparative Example 1, the chromium content (% by mass) is an amount outside the range of the chromium content (% by mass) in the steel materials of Examples 1 to 8. From the results shown in Table 3, in the outer inner ring obtained in Comparative Example 1, the Vickers hardness Hv is in the same range as the Vickers hardness Hv of the outer inner ring obtained in Examples 1-8. I know that there is. However, in the outer inner ring obtained in Comparative Example 1, the amount of retained austenite, the precipitate area ratio, and the average particle diameter of the precipitate particles are the same as those in the outer inner ring obtained in Examples 1-8. It can be seen that the amount of retained austenite, the precipitate area ratio, and the average particle diameter of the precipitate particles are larger than the maximum values. Furthermore, the rolling fatigue life (L ₁₀ life) of the outer inner ring obtained in Comparative Example 1, since it is less than 1000 hours, an outer inner ring obtained in Examples 1 to 8 rolling fatigue life (L ₁₀ It can be seen that it is significantly shorter than (life).

The contents (mass%) of silicon, manganese, chromium and molybdenum in the steel material of Comparative Example 2 are outside the ranges of the contents (mass%) of silicon, manganese, chromium and molybdenum in the steel materials of Examples 1 to 8, respectively. Amount. Moreover, in the steel material of the comparative example 2, the value of Formula (Ia) is smaller than the minimum value of Formula (I). The value of formula (IIa) is smaller than the minimum value of formula (II). Therefore, the composition of the steel material of Comparative Example 2 does not satisfy the formula (I) and the formula (II). From the results shown in Table 3, in the outer inner ring obtained in Comparative Example 2, each of the Vickers hardness Hv, the precipitate area ratio, and the average particle diameter of the precipitate particles is as in Examples 1 to 8. It can be seen that the Vickers hardness Hv, the precipitate area ratio, and the average particle diameter of the precipitate particles of the outer inner ring obtained in (1) are in the same ranges. However, it can be seen that the amount of retained austenite of the outer inner ring obtained in Comparative Example 2 is smaller than the minimum value of the amount of retained austenite of the outer inner ring obtained in Examples 1-8. Further, the rolling fatigue life (L ₁₀ life) of the outer inner ring obtained in Comparative Example 2, since less than 1000 hours, an outer inner ring obtained in Examples 1 to 8 rolling fatigue life (L ₁₀ It can be seen that it is significantly shorter than (life).

The contents (mass%) of silicon, nickel, copper, chromium and molybdenum in the steel material of Comparative Example 3 are the contents (mass%) of silicon, nickel, copper, chromium and molybdenum in the steel materials of Examples 1 to 8, respectively. The amount is out of the range. Moreover, in the steel material of the comparative example 3, the value of Formula (Ia) is larger than the maximum value of Formula (I). The value of formula (IIa) is greater than the maximum value of formula (II). Therefore, the composition of the steel material of Comparative Example 3 does not satisfy the formula (I) and the formula (II). From the results shown in Table 3, in the outer inner ring obtained in Comparative Example 3, the Vickers hardness Hv is in the same range as the Vickers hardness Hv of the outer inner ring obtained in Examples 1-8. I know that there is. However, the amount of retained austenite of the outer inner ring obtained in Comparative Example 3, the area ratio of the precipitates, and the average particle diameter of the precipitate particles are the amount of retained austenite of the outer inner rings obtained in Examples 1 to 8, It turns out that it is larger than each maximum value of the said deposit area ratio and the average particle diameter of the said deposit particle. Further, the rolling fatigue life (L ₁₀ life) of the outer inner ring obtained in Comparative Example 3, since less than 1000 hours, an outer inner ring obtained in Examples 1 to 8 rolling fatigue life (L ₁₀ It can be seen that it is significantly shorter than (life).

In the steel material of Comparative Example 4, the value of formula (Ia) is smaller than the minimum value of formula (I). Therefore, the composition of the steel material of Comparative Example 4 does not satisfy the formula (I) but satisfies the formula (II). From the results shown in Table 3, in the outer inner ring obtained in Comparative Example 4, each of the Vickers hardness Hv, the precipitate area ratio, and the average particle diameter of the precipitate particles was determined in Examples 1 to 8. It can be seen that the Vickers hardness Hv, the precipitate area ratio, and the average particle diameter of the precipitate particles of the outer inner ring obtained in (1) are in the same ranges. However, it can be seen that the amount of retained austenite of the outer inner ring obtained in Comparative Example 4 is smaller than the minimum value of the amount of retained austenite of the outer inner ring obtained in Examples 1-8. Further, the rolling fatigue life (L ₁₀ life) of the outer inner ring obtained in Comparative Example 4, since less than 1000 hours, an outer inner ring obtained in Examples 1 to 8 rolling fatigue life (L ₁₀ It can be seen that it is significantly shorter than (life).

In the steel material of Comparative Example 5, the value of formula (Ia) is smaller than the minimum value of formula (I). The value of formula (IIa) is greater than the maximum value of formula (II). Therefore, the composition of the steel material of Comparative Example 5 does not satisfy the formula (I) and the formula (II). From the results shown in Table 3, in the outer and inner rings obtained in Comparative Example 5, the Vickers hardness Hv, the precipitate area ratio, and the average particle diameter of the precipitate particles were determined in Examples 1 to 8, respectively. It can be seen that the Vickers hardness Hv, the precipitate area ratio, and the average particle diameter of the precipitate particles of the outer inner ring obtained in (1) are in the same ranges. However, it can be seen that the amount of retained austenite of the outer inner ring obtained in Comparative Example 5 is smaller than the minimum value of the amount of retained austenite of the outer inner ring obtained in Examples 1-8. Further, the rolling fatigue life (L ₁₀ life) of the outer inner ring obtained in Comparative Example 5, since less than 1000 hours, an outer inner ring obtained in Examples 1 to 8 rolling fatigue life (L ₁₀ It can be seen that it is significantly shorter than (life).

The chromium content (mass%) in the steel material of Comparative Example 6 is an amount outside the range of the chromium content (mass%) in the steel materials of Examples 1 to 8. In the steel material of Comparative Example 6, the value of the formula (IIa) is larger than the maximum value of the formula (II). Therefore, the steel material of Comparative Example 3 satisfies the formula (I) but does not satisfy the formula (II). From the results shown in Table 3, in the outer and inner rings obtained in Comparative Example 6, the Vickers hardness Hv, the amount of retained austenite, and the average particle size of the precipitate particles are as in Examples 1 to 8, respectively. It can be seen that the Vickers hardness Hv, the amount of retained austenite, and the average particle diameter of the precipitate particles are in the same ranges as the obtained outer inner ring. However, it can be seen that the precipitate area ratio of the outer inner ring obtained in Comparative Example 6 is larger than the maximum value of the precipitate area ratio of the outer inner ring obtained in Examples 1-8. Further, the rolling fatigue life (L ₁₀ life) of the outer inner ring obtained in Comparative Example 6, since less than 1000 hours, an outer inner ring obtained in Examples 1 to 8 rolling fatigue life (L ₁₀ It can be seen that it is significantly shorter than (life).

In the steel materials of Comparative Examples 7 to 10, the value of the formula (IIa) is larger than the maximum value of the formula (II). Therefore, the composition of the steel materials of Comparative Examples 7 to 10 satisfies the formula (I) but does not satisfy the formula (II). From the results shown in Table 3, the rolling fatigue life (L ₁₀ life) of each of the outer and inner rings obtained in Comparative Examples 7 to 10 was less than 1000 hours, and thus obtained in Examples 1 to 8. It can be seen that it is significantly shorter than the rolling fatigue life (L ₁₀ life) of the outer and inner rings.

The content (mass%) of manganese and chromium in the steel material of Comparative Example 11 is an amount outside the range of the content (mass%) of manganese and chromium in the steel materials of Examples 1 to 8. In the steel material of Comparative Example 11, the value of the formula (Ia) is larger than the maximum value of the formula (I). Therefore, the composition of the steel material of Comparative Example 11 does not satisfy the formula (I) but satisfies the formula (II). From the results shown in Table 3, in the outer and inner rings obtained in Comparative Example 11, the Vickers hardness Hv, the precipitate area ratio, and the average particle diameter of the precipitate particles were determined in Examples 1 to 8, respectively. It can be seen that the Vickers hardness Hv, the precipitate area ratio, and the average particle diameter of the precipitate particles of the outer inner ring obtained in (1) are in the same ranges. However, it can be seen that the amount of retained austenite of the outer inner ring obtained in Comparative Example 11 is larger than the maximum value of the amount of retained austenite of the outer inner ring obtained in Examples 1-8. Further, the rolling fatigue life (L ₁₀ life) of the outer inner ring obtained in Comparative Example 11, since it is less than 1000 hours, an outer inner ring obtained in Examples 1 to 8 rolling fatigue life (L ₁₀ It can be seen that it is significantly shorter than (life).

  Therefore, based on these results, the content of carbon, silicon, manganese, nickel, copper, chromium, and molybdenum (mass%) is a predetermined amount, and the base portion having the composition satisfying the formulas (I) and (II) According to the rolling bearing provided with the rolling sliding member including the surface carbonitriding layer, it is suggested that a long rolling fatigue life can be ensured.

Test example 2
Using the deep groove ball bearings obtained in Example 1, Comparative Example 4 and Comparative Example 8, the inner ring was rotated under the conditions shown in Table 2. The rotation of the inner ring was stopped when a predetermined time had elapsed, and the same operation as in Test Example 1 was performed, whereby the amount of retained austenite at a position 100 μm deep from the rolling sliding surface of the inner ring was examined over time.

FIG. 4 shows the results of examining the change over time in the amount of retained austenite at the maximum orthogonal shear stress generation depth z ₀ position in the inner rings obtained in Example 1, Comparative Example 4 and Comparative Example 8 in Test Example 2. . In the figure, the black circles indicate the change over time in the amount of retained austenite at the position of the maximum orthogonal shear stress generation depth z ₀ in the inner ring obtained in Example 1, and the white squares indicate the maximum orthogonal shear stress generation in the inner ring obtained in Comparative Example 4. The change over time of the amount of retained austenite at the depth z ₀ position, and the white triangle indicate the change over time of the amount of retained austenite at the position of the maximum orthogonal shear stress generation depth z ₀ in the inner ring obtained in Comparative Example 8.

From the results shown in FIG. 4, the amount of retained austenite at the position of the maximum orthogonal shear stress generation depth z ₀ of the inner ring obtained in Example 1 before the rotation of the inner ring was it can be seen that more than the residual austenite amount of the position of the maximum orthogonal shear stress generating depth z ₀ of the. Further, it can be seen that the amount of retained austenite at the position of the maximum orthogonal shear stress generation depth z ₀ of the inner ring obtained in Comparative Example 8 is approximately the same as before the rotation of the inner ring is started. However, in the inner ring obtained in Example 1, it can be seen that the amount of retained austenite at the position of the maximum orthogonal shear stress generation depth z ₀ decreases in a shorter time than the inner ring obtained in Comparative Example 8. Therefore, it can be seen that the inner ring obtained in Example 1 contains a large amount of retained austenite at the position of the maximum orthogonal shear stress generation depth z ₀ , and easily causes stress-induced martensitic transformation.

Test example 3
Using the deep groove ball bearings obtained in Example 1, Comparative Example 4 and Comparative Example 8, the inner ring was rotated under the conditions shown in Table 2. The rotation of the inner ring was stopped when a predetermined time had elapsed, and the same operation as in Test Example 1 was performed to examine the Vickers hardness Hv at a position 100 μm deep from the rolling sliding surface of the inner ring over time.

In Test Example 3, the results of examining the change over time in the Vickers hardness at the position of the maximum orthogonal shear stress generation depth z ₀ in the inner ring obtained in Example 1, Comparative Example 4 and Comparative Example 8 are shown in FIG. . In the figure, the black circle represents the change over time in the Vickers hardness at the position of the maximum orthogonal shear stress generation depth z ₀ in the inner ring obtained in Example 1, and the white square represents the generation of the maximum orthogonal shear stress in the inner ring obtained in Comparative Example 4. The time-dependent change in the Vickers hardness at the depth z ₀ position, and the white triangle indicate the time-dependent change in the Vickers hardness at the maximum orthogonal shear stress generation depth z ₀ position in the rolling sliding member obtained in Comparative Example 8.

  From the results shown in FIG. 5, the inner ring obtained in Example 1 is the inner ring obtained in Comparative Examples 4 and 8 in a short time from the start of rotation of the inner ring at the position where the maximum orthogonal shear stress is generated. It can be seen that a larger Vickers hardness is secured.

  From the above results, the base portion and the surface having the above-described composition satisfying the formula (I) and the formula (II), wherein the contents (mass%) of carbon, silicon, manganese, nickel, copper, chromium and molybdenum are predetermined amounts. It can be seen that according to the rolling sliding member including the carbonitrided layer, a long rolling fatigue life can be secured.

  1: Ball bearing, 10: Outer ring, 10a1, 20a1, 30a1: Base part, 10a2, 20a2, 30a2: Surface carbonitrided layer, 14: Shaped material, 15: Intermediate material, 20: Inner ring, 30: Ball

Claims (7)

A rolling sliding member having a polished rolling sliding surface that comes into relative contact with a mating member,
Carbon 0.1-0.5 mass%, Silicon 0.05-0.25 mass%, Manganese 1.2-2.3 mass%, Nickel 0.1 mass% or less, Copper 0.05 mass % Or less, chromium 2.5-3.1 mass%, molybdenum 0.01-0.1 mass%, the balance being iron and inevitable impurities, the formula (I):
47.2 ≦ 8.1Mn + 13.7Cr ≦ 61.8 (I)
(In the formula, Mn represents the manganese content (mass%), and Cr represents the chromium content (mass%)).
And formula (II):
0.65 ≦ 9.2Si + 29 (Ni + Cu) + 18.5Mo ≦ 5.5 (II)
(In the formula, Si represents the silicon content (mass%), Ni represents the nickel content (mass%), Cu represents the copper content (mass%), and Mo represents the molybdenum content (mass%).
A rolling sliding member comprising a base portion having a composition satisfying the requirements and a surface carbonitriding layer.   The rolling sliding member according to claim 1, wherein a position having a maximum orthogonal shear stress generation depth from the rolling sliding surface exists in the surface carbonitriding layer.   The rolling sliding member according to claim 1 or 2, wherein a Vickers hardness Hv at a position where the maximum orthogonal shear stress generation depth is 700 to 800 from the rolling sliding surface. The amount of retained austenite at the position of the maximum orthogonal shear stress generation depth from the rolling sliding surface is 25 to 50% by volume,
The area ratio of the precipitate particles at the position of the maximum orthogonal shear stress generation depth from the rolling sliding surface is 1% or less,
The rolling sliding member according to any one of claims 1 to 3, wherein an average particle diameter of the precipitate particles at a position of the maximum orthogonal shear stress generation depth from the rolling sliding surface is 0.4 µm or less. A method of manufacturing a rolling sliding member having a rolling sliding surface that is relatively polished with respect to a counterpart member,
(A) Carbon 0.1-0.5 mass%, Silicon 0.05-0.25 mass%, Manganese 1.2-2.3 mass%, Nickel 0.1 mass% or less, Copper 0 .05 mass% or less, chromium 2.5-3.1 mass%, molybdenum 0.01-0.1 mass%, the balance being iron and inevitable impurities, the formula (I):
47.2 ≦ 8.1Mn + 13.7Cr ≦ 61.8 (I)
(In the formula, Mn represents the manganese content (mass%), and Cr represents the chromium content (mass%)).
And formula (II):
0.65 ≦ 9.2Si + 29 (Ni + Cu) + 18.5Mo ≦ 5.5 (II)
(In the formula, Si represents the silicon content (mass%), Ni represents the nickel content (mass%), Cu represents the copper content (mass%), and Mo represents the molybdenum content (mass%).
Obtaining a shaped material from a steel material having a composition satisfying
(B) The raw material is heated and maintained at 850 to 980 ° C. in a carbonitriding atmosphere having a carbon potential of 1.1 to 1.5 and a ratio of the ammonia flow rate to the carburized metamorphic gas flow rate of 1 to 5%. A process of carbonitriding the shape material to obtain an intermediate material,
(C) The step of quenching by heating and holding the intermediate material after the step (B) at 830 to 870 ° C, and (D) The intermediate material after the step (C) was heated and held at 160 to 200 ° C. Then, the manufacturing method of a rolling sliding member including the process of tempering by cooling. Steel material for carbonitriding, carbon 0.1-0.5 mass%, silicon 0.05-0.25 mass%, manganese 1.2-2.3 mass% And 0.1% by mass or less of nickel, 0.05% by mass or less of copper, 2.5 to 3.1% by mass of chromium, and 0.01 to 0.1% by mass of molybdenum, with the balance being iron and Inevitable impurities, formula (I):
47.2 ≦ 8.1Mn + 13.7Cr ≦ 61.8 (I)
(In the formula, Mn represents the manganese content (mass%), and Cr represents the chromium content (mass%)).
And formula (II):
0.65 ≦ 9.2Si + 29 (Ni + Cu) + 18.5Mo ≦ 5.5 (II)
(In the formula, Si represents the silicon content (mass%), Ni represents the nickel content (mass%), Cu represents the copper content (mass%), and Mo represents the molybdenum content (mass%).
Carbonitriding steel having a composition satisfying A rolling bearing having an outer ring having a rolling sliding surface on the inner periphery, an inner ring having a rolling sliding surface on the outer periphery, and a plurality of rolling elements disposed between both rolling sliding surfaces of the outer inner ring. There,
A rolling bearing, wherein at least one of the outer ring, the inner ring, and the rolling element comprises the rolling sliding member according to any one of claims 1 to 4.