JP2013163833A - Bearing component and rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing component which can reduce rare metal elements contained in a material while securing excellent durability, and to provide a rolling bearing.SOLUTION: An outer race 11, an inner race 12 and a ball 13 which are bearing components, are formed of a quench-hardened steel containing 0.40-0.60 mass% C, 0.15-0.35 mass% Si, 0.10-1.10 mass% Mn, 0.0010-0.0100 mass% B and the balance Fe and inevitable impurities.

Description

  The present invention relates to a bearing component and a rolling bearing, and more particularly to a bearing component and a rolling bearing capable of reducing rare metal elements contained in a material while ensuring excellent durability.

  High alloy steel to which rare metal elements such as Cr (chromium), Ni (nickel), Mo (molybdenum), and V (vanadium) are added has been developed as bearing steel that constitutes bearing parts including raceway members and rolling elements. ,It is used. These rare metal elements are added mainly for the purpose of improving hardenability, high high-temperature hardness, precipitation strengthening due to the formation of carbides, and the like. On the other hand, with regard to these rare metal elements, problems such as price increases and deterioration in availability have arisen in recent years due to resource depletion and political export restrictions. For this reason, bearing components are not designed to improve the material strength by using high alloy materials, but the rare metal elements in the material are reduced to achieve the required strength and other characteristics by heat treatment and surface modification technology. The technology to do is demanded.

  On the other hand, carbon steel for machine structure (JIS standard SC steel) is used instead of bearing steel containing more than 1% by mass of Cr such as high carbon chromium bearing steel (for example, JIS standard SUJ2) which is widely used at present. ) Can be considered as a bearing steel. For example, JIS standards S45C and S55C, which do not contain rare metal elements, are widely used in automotive parts, and therefore have the advantage that they are not only easily available in various parts of the world but also are inexpensive. JIS standard S53C is also applied to rolling bearings as a material for automobile hub bearings.

  However, the carbon steel for mechanical structure has low hardenability compared to the high carbon chromium bearing steel. Therefore, there exists a problem that the size of the bearing which can apply carbon steel for machine structures is limited. Also, bearing parts made of carbon steel for machine structural use have a problem that the rolling fatigue life is shorter under conditions where high surface pressure is applied to the rolling surface than bearing parts made of high carbon chromium bearing steel. . For this reason, bearing parts made of carbon steel for mechanical structures have a problem that it is difficult to apply to applications with high surface pressure.

  On the other hand, in a low carbon steel with a carbon content of 0.35% by mass or less with refined crystal grains, boron is added for the purpose of compensating for the hardenability reduced by the refinement of crystal grains and enhancing impact characteristics. Added steel for case hardening has been proposed (see, for example, Patent Document 1). The bearing ring is constituted by a bearing ring made of a high carbon steel having a carbon content of 0.65% by mass or more and dispersed with titanium carbide and / or carbonitride having an average particle diameter of 50 nm or less. A technique for adding boron to steel has been proposed (see, for example, Patent Document 2).

JP 2006-307271 A JP-A-11-51065

  As described above, when a material that simply does not reduce or add rare metal elements, such as carbon steel for mechanical structures, is adopted as the material of the bearing component, the allowable bearing size and surface pressure are reduced. There is a problem that the performance is lowered.

  The present invention has been made to solve the above-described problems, and its object is to provide a bearing component and a rolling bearing capable of reducing rare metal elements contained in the material while ensuring excellent durability. Is to provide.

  The bearing component according to the first aspect of the present invention has carbon of 0.40 mass% or more and 0.60 mass% or less, silicon of 0.15 mass% or more and 0.35 mass% or less, and 0.10 mass. It is made of a steel that has been hardened and hardened and contains the remainder of iron and impurities, and contains manganese in an amount of not less than 1% and not more than 1.10% by mass and boron in an amount not less than 0.0010% by mass and not more than 0.0100% by mass.

  Further, the bearing component according to the second aspect of the present invention includes 0.40% by mass or more and 0.60% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon; Containing 10 mass% or more and 1.10 mass% or less of manganese, 0.0010 mass% or more and 0.0100 mass% or less of boron, and 0.50 mass% or more and 1.00 mass% or less of chromium, and the balance iron And made of hardened steel made of impurities.

  Further, the bearing component according to the third aspect of the present invention includes 0.40% by mass or more and 0.60% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon; Containing 10% by mass or more and 1.10% by mass or less of manganese, 0.0010% by mass or more and 0.0100% by mass or less of boron, and 0.015% by mass or more and 0.050% by mass or less of titanium, and the balance It consists of a hardened and hardened steel consisting of iron and impurities.

  Further, the bearing component according to the fourth aspect of the present invention includes 0.40% by mass or more and 0.60% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon; 10 mass% or more and 1.10 mass% or less manganese, 0.0010 mass% or more and 0.0100 mass% or less boron, 0.50 mass% or more and 1.00 mass% or less chromium, 0.015 mass It is made of a steel that has been hardened and hardened and contains the remaining iron and impurities.

  The bearing parts according to the first and third aspects of the present invention are made of steel to which rare metal elements such as Cr, Ni, Mo, and V are not added. Further, in the bearing component according to the second aspect and the fourth aspect of the present invention, only Cr is added as a rare metal element, and the addition amount is set smaller than that of JIS standard SUJ2. Further, by adding boron to the steel, the steel has a carbon content of 0.40 to 0.60% by mass, which is sufficient for a steel having a low silicon content. Imperviousness is imparted, and excellent durability of the bearing parts made of the steel is ensured.

  Further, chromium is added to the steel constituting the bearing component in the second and fourth aspects. Thereby, the application size of a bearing component can be expanded.

  Titanium is added to the steel constituting the bearing component in the third and fourth aspects. When boron is added to the steel, the boron combines with nitrogen in the steel to form a nitride. Thus, boron which became nitride does not contribute to improvement of hardenability. On the other hand, nitrogen in the steel is fixed as titanium nitride by adding titanium that is more reactive with nitrogen than boron, and the effect of improving the hardenability by boron can be reliably obtained.

  As described above, according to the bearing component of the present invention, it is possible to provide a bearing component capable of reducing the rare metal element contained in the material while ensuring excellent durability.

  The reason why the component composition of the steel constituting the bearing part is limited to the above range is as follows.

Carbon: 0.40 mass% or more and 0.60 mass% or less The quenching hardness of steel is mainly correlated with the carbon content, and the amount of carbon dissolved in the base metal is 0.5 mass regardless of other components. If it is% or more, the quenching hardness is almost constant. In order to provide the bearing part with a quenching hardness of 60 HRC or more necessary for obtaining a sufficient rolling fatigue life, the carbon content needs to be 0.4 mass% or more. On the other hand, when the carbon content increases, coarse carbides and pearlite structures are formed, and the machinability and plastic workability deteriorate. And in order to respond | correspond to this, the spheroidizing annealing for dispersing a carbide | carbonized_material finely is needed. In order to reduce the manufacturing cost, it is preferable to omit this spheroidizing annealing. In order to omit the spheroidizing annealing, the carbon content is preferably 0.6% by mass or less. Also, in order to improve the surface damage resistance (peeling resistance) and wear resistance by precipitating carbides and nitrides on the surface layer, the carbon concentration on the surface of the bearing component is increased to 0.8 to 1.1% by mass. It is conceivable that the bearing parts are subjected to a carburizing treatment or a carbonitriding treatment for increasing the nitrogen concentration to about 0.5% by mass. If the carbon content of the material steel is 0.4 mass% or more, the time required for carburizing treatment or carbonitriding treatment can be shortened as compared with general carburized steel. From the above viewpoint, the carbon content is set to 0.40 mass% or more and 0.60 mass% or less.

Silicon: 0.15 mass% or more and 0.35 mass% or less Silicon contributes to the improvement of the temper softening resistance of steel. When the silicon content is less than 0.15% by mass, the function cannot be exhibited sufficiently. On the other hand, when silicon content exceeds 0.35 mass%, the problem that forgeability falls may arise. Therefore, the silicon content is set to 0.15 mass% or more and 0.35 mass% or less.

Manganese: 0.10% by mass or more and 1.10% by mass or less Manganese contributes to improving the hardenability of steel. In order to effectively use the function, addition of 0.30% by mass or more is desirable, but the addition of boron can reduce the manganese content to 0.10%. On the other hand, if the manganese content exceeds 1.10% by mass, a large amount of manganese sulfide (MnS), which is a non-metallic inclusion, is formed in the steel, which may adversely affect the characteristics of the bearing component. Therefore, the manganese content is set to 0.10% by mass to 1.10% by mass.

Boron: 0.0010% by mass or more and 0.0100% by mass or less Boron has a function of improving the hardenability of steel by adding a small amount. In order to ensure the hardenability equivalent to JIS standard SUJ2, which is widely used as steel constituting the bearing parts, it is necessary to add 0.0010% by mass or more. On the other hand, the boron solid solubility limit in the ferrite phase of the base material is about 0.005% by mass. Therefore, if boron is added in an amount exceeding 0.0100% by mass, the possibility that the boron precipitates as a precipitate such as a nitride, carbide, carbonitride, etc. continues to the grain boundary and becomes coarser. If hard and coarse precipitates exist below the contact surfaces of the bearing parts (the surface of the race member that contacts the rolling element and the surface of the rolling member that contacts the race member), stress concentration occurs and internal cracks occur. This may cause the rolling fatigue life to be shortened. Therefore, the boron content is set to be 0.0010 mass% or more and 0.0100 mass% or less (10 ppm or more and 100 ppm or less).

Titanium: 0.015 mass% or more and 0.050 mass% or less As described above, boron added to steel reacts with nitrogen at a high temperature to form BN (boron nitride). If it does so, the solid solution amount of the boron in a base material will reduce, and the improvement effect of the hardenability by boron addition will fall. On the other hand, by adding titanium having a higher reactivity with nitrogen than boron, nitrogen in the steel can be consumed, and the solid solution amount of boron in the base material can be increased. When the addition amount of titanium is less than 0.015% by mass, the above effect is not sufficiently exhibited. On the other hand, when the added amount of titanium exceeds 0.050% by mass, nitride (TiN) continuously precipitates and becomes coarse, and becomes a stress concentration source under the contact surface of the bearing part, which adversely affects the rolling fatigue life. There is a risk of giving. Therefore, when adding titanium, the addition amount is desirably 0.015 mass% or more and 0.050 mass% or less. Moreover, by making the addition amount of titanium 0.010% by mass or more, the effect of refining crystal grains can be expected due to the pinning effect by TiN (titanium nitride) that does not dissolve in the base material even at high temperatures. As is clear from the Hall Petch relationship, the refinement of crystal grains can improve the material strength and contribute to the improvement of the rolling fatigue life. On the other hand, the titanium addition amount can be less than 0.010% by mass from the viewpoint of surely obtaining the hardenability improvement effect by adding boron and minimizing the cost increase by adding titanium.

Chromium: 0.50 mass% or more and 1.00 mass% or less Chromium improves the hardenability of the steel and improves the rolling fatigue life of the bearing component. If the addition amount is less than 0.50% by mass, this function is not sufficiently exhibited. On the other hand, if it is added in excess of 1.00% by mass, one of the most important objects of the present invention, reduction of rare metal elements, is not sufficiently achieved. Therefore, when adding chromium, the addition amount is desirably 0.50 mass% or more and 1.00 mass% or less.

  In the bearing component, a titanium precipitate consisting of at least one selected from the group consisting of titanium carbide, nitride, and carbonitride is dispersed in the steel. The average diameter may be 0.1 μm or more and 5 μm or less.

  Thus, by disperse | distributing the titanium precipitate of a suitable magnitude | size in steel, the refinement | miniaturization effect of a crystal grain can be acquired reliably, suppressing the bad influence on rolling fatigue life. The average diameter of the titanium precipitate is calculated by observing the precipitate with a scanning electron microscope (SEM) after cutting the bearing part and etching the cross section with an appropriate etching solution. Can be determined.

  In the bearing component, boron precipitates made of boron nitride are dispersed in the steel, and the average diameter of the precipitates including the titanium precipitates and boron precipitates is 0.1 μm or more and 10 μm or less. There may be. By doing in this way, the addition effect of boron and titanium can be acquired, suppressing the bad influence on the rolling fatigue life by a large-sized precipitate.

In the bearing component, the number of prior austenite crystal grains of the steel in the cross section of the bearing component may be 8000 pieces / mm ² or more. By doing in this way, the microstructure of the steel which comprises a bearing component refines | miniaturizes and the characteristic of a bearing component improves.

  In the bearing component, the oxygen content of the steel may be 15 ppm or less. By reducing the oxygen content that adversely affects the rolling fatigue life of the bearing component to this level, it is possible to obtain a bearing component having a long life more reliably.

  In the bearing component, the carbon concentration is higher in the region including the contact surface, which is the surface to be contacted with the other bearing component, compared with the inside, and the carbon concentration is 0.8 mass% or more and 1.1 mass% or less. A carbon-enriched layer may be formed.

  By increasing the carbon concentration on the contact surface, carbide (eg, cementite) can be formed on the contact surface. Carbide improves the durability of the contact surface and prolongs the rolling fatigue life of bearing parts. In order to obtain such an effect by the carbide, it is preferable to form a carbon enriched layer of 0.8% by mass or more. On the other hand, in order to increase the carbon concentration beyond 1.1 mass%, a treatment at a higher concentration than the general carburizing treatment is required, which causes an increase in manufacturing cost.

  In the above-mentioned bearing component, the nitrogen concentration is higher in the region including the contact surface, which is the surface to be contacted with other bearing components, compared with the inside, and has a nitrogen concentration of 0.05% by mass or more and 0.5% by mass or less. A nitrogen-enriched layer may be formed.

  By forming the nitrogen-enriched layer on the contact surface, the rolling fatigue life of the bearing component can be extended. When the nitrogen concentration of the nitrogen-enriched layer is less than 0.05% by mass, the effect cannot be obtained sufficiently. On the other hand, in the nitrogen-enriched layer exceeding the nitrogen concentration of 0.5% by mass, vacancies are scattered in the base material, which causes a decrease in strength.

  In the bearing component, a hardened layer by induction hardening may be formed in a region including a contact surface that is a surface to be contacted with another bearing component. Thereby, it is possible to obtain a bearing component having high toughness while imparting sufficient durability to the contact surface.

  In the bearing component, the hardness of the contact surface may be 60 HRC or more. Thereby, high durability of a contact surface can be obtained more reliably.

  The rolling bearing according to the present invention includes a race member and a plurality of rolling elements arranged in contact with the rolling surface of the race member. At least one of the race member and the rolling element is the bearing component of the present invention. By providing the bearing component of the present invention as a race member or rolling element, according to the rolling bearing of the present invention, it is possible to reduce the rare metal elements contained in the material while ensuring excellent durability. A bearing can be provided.

  As is apparent from the above description, according to the bearing component and the rolling bearing of the present invention, it is possible to provide a bearing component and a rolling bearing capable of reducing rare metal elements contained in the material while ensuring excellent durability. be able to.

It is a schematic sectional drawing which shows the structure of a deep groove ball bearing. It is the schematic fragmentary sectional view which expanded and showed the principal part of FIG. It is a flowchart which shows the outline of the manufacturing method of a rolling bearing. It is a schematic fragmentary sectional view which shows another example of a structure of a deep groove ball bearing. It is a flowchart which shows another example of the manufacturing method of a rolling bearing. It is a CCT diagram of SUJ2. It is a CCT diagram of S53C. It is a CCT diagram of S53C-B-2. It is a CCT diagram of S53C-B-Cr. It is an optical microscope photograph which shows the former austenite crystal grain boundary of S53C. It is an optical microscope photograph which shows the former austenite crystal grain boundary of S53C-B-2. It is a schematic front view which shows the structure of the principal part of a point contact rolling life tester. It is a schematic side view which shows the structure of the principal part of a point contact rolling life tester. It is a figure which shows the result of a rolling fatigue life test.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
First, Embodiment 1 which is one embodiment of the present invention will be described. Referring to FIGS. 1 and 2, deep groove ball bearing 1 that is a rolling bearing in Embodiment 1 includes an outer ring 11 as a first race member that is a bearing component, and an inner ring as a second race member that is a bearing component. 12, balls 13 as a plurality of rolling elements that are bearing parts, and a cage 14. The outer ring 11 is formed with an outer ring rolling surface 11A as an annular first rolling surface. The inner ring 12 is formed with an inner ring rolling surface 12A as an annular second rolling surface facing the outer ring rolling surface 11A. Further, the balls 13 are formed with ball rolling surfaces 13A (the surfaces of the balls 13) as rolling elements rolling surfaces. The outer ring rolling surface 11A, the inner ring rolling surface 12A, and the ball rolling surface 13A are contact surfaces of these bearing components. The balls 13 are in contact with each of the outer ring rolling surface 11A and the inner ring rolling surface 12A on the ball rolling surface 13A, and are arranged at a predetermined pitch in the circumferential direction by an annular retainer 14. It is rotatably held on an annular track. With the above configuration, the outer ring 11 and the inner ring 12 of the deep groove ball bearing 1 are rotatable relative to each other.

  Referring to FIG. 2, the outer ring 11, the inner ring 12, and the ball 13, which are bearing parts, are 0.40 mass% or more and 0.60 mass% or less of carbon, and 0.15 mass% or more and 0.35 mass% or less. A quench hardening treatment comprising silicon, 0.10% by mass to 1.10% by mass manganese and 0.0010% by mass to 0.0100% by mass boron, the balance being iron and impurities. Made of steel.

  Outer ring 11, inner ring 12 and ball 13 which are bearing parts in the present embodiment are made of steel to which rare metal elements such as Cr, Ni, Mo and V are not added. Further, by adding boron to the steel, the steel has a carbon content of 0.40 to 0.60% by mass, which is sufficient for a steel having a low silicon content. Imperviousness is imparted, and excellent durability of the bearing parts made of the steel is ensured. As described above, the outer ring 11, the inner ring 12 and the ball 13, and the deep groove ball bearing 1 which are the bearing components in the present embodiment can reduce the rare metal element contained in the material while ensuring excellent durability. It is a bearing part and a rolling bearing.

Here, 0.50 mass% or more and 1.00 mass% or less of chromium may be added to the steel. Thereby, it becomes easy to ensure sufficient hardenability and rolling fatigue life while suppressing addition of rare metal elements as much as possible.
Moreover, 0.015 mass% or more and 0.050 mass% or less of titanium may be further added to the steel. Thereby, nitrogen in steel can be fixed as titanium nitride, and the effect of improving the hardenability by boron can be obtained more reliably.

  Furthermore, outer ring 11, inner ring 12 and ball 13 in the present embodiment are carbon in areas including outer ring rolling surface 11A, inner ring rolling surface 12A and ball rolling surface 13A, respectively, compared with inner portions 11C, 12C and 13C. It has strengthening treatment layers 11B, 12B, and 13B that are carbon-enriched layers having a high concentration and a carbon concentration of 0.8% by mass or more and 1.1% by mass or less. The formation of the reinforcing treatment layers 11B, 12B, and 13B is not essential in the present invention. However, by forming this, the durability of the outer ring rolling surface 11A, the inner ring rolling surface 12A, and the ball rolling surface 13A is improved. Thus, the rolling fatigue life of the outer ring 11, the inner ring 12 and the ball 13 can be further extended.

  Further, the strengthened layers 11B, 12B, and 13B may be nitrogen-enriched layers having a higher nitrogen concentration than the inside and a nitrogen concentration of 0.05% by mass or more and 0.5% by mass or less. Thereby, durability of the outer ring | wheel 11, the inner ring | wheel 12, and the ball | bowl 13 can be improved further. It should be noted that the reinforced processing layers 11B, 12B, and 13B may be layers having only one of the carbon concentration and the nitrogen concentration higher than those of the interiors 11C, 12C, and 13C, or may be layers having both a high carbon concentration and a nitrogen concentration. There may be.

  Furthermore, in outer ring 11, inner ring 12 and ball 13 in the present embodiment, titanium is deposited in the steel with at least one selected from the group consisting of titanium carbide, nitride and carbonitride. The thing is disperse | distributed and the average diameter of the said titanium precipitate may be 0.1 micrometer or more and 5 micrometers or less. Thus, by disperse | distributing the titanium precipitate of a suitable magnitude | size in steel, the refinement | miniaturization effect of a crystal grain can be acquired reliably, suppressing the bad influence on rolling fatigue life.

  Further, in outer ring 11, inner ring 12 and ball 13 in the present embodiment, boron precipitates made of boron nitride are dispersed in the steel constituting them, and includes the above titanium precipitates and boron precipitates. The average diameter of the precipitate may be not less than 0.1 μm and not more than 10 μm. By doing in this way, the addition effect of boron and titanium can be acquired, suppressing the bad influence on the rolling fatigue life by a large-sized precipitate.

Furthermore, in the outer ring 11, inner ring 12 and ball 13 in the present embodiment, the number of old austenite crystal grains of steel in the cross section of outer ring 11, inner ring 12 and ball 13 is preferably 8000 pieces / mm ² or more. Thereby, the microstructure of the steel constituting the outer ring 11, the inner ring 12 and the ball 13 is refined, and the characteristics of the outer ring 11, the inner ring 12 and the ball 13 are improved.

  Further, in the outer ring 11, the inner ring 12 and the ball 13 in the present embodiment, it is preferable that the oxygen content of the steel constituting the outer ring 11, the inner ring 12 and the ball 13 is 15 ppm or less. Thereby, the rolling fatigue life of the outer ring 11, the inner ring 12 and the ball 13 can be further increased.

  Furthermore, in outer ring 11, inner ring 12 and ball 13 in the present embodiment, it is preferable that the hardness of outer ring rolling surface 11A, inner ring rolling surface 12A and ball rolling surface 13A is 60 HRC or more. Thereby, the high durability of the outer ring rolling surface 11A, the inner ring rolling surface 12A, and the ball rolling surface 13A can be obtained more reliably.

  Next, the bearing component and the rolling bearing manufacturing method in the present embodiment will be described. With reference to FIG. 3, a steel material preparation process is first implemented as process (S10). In this step (S10), 0.40% by mass to 0.60% by mass of carbon, 0.15% by mass to 0.35% by mass of silicon, and 0.10% by mass to 1.10% by mass. A steel material containing the following manganese and 0.0010% by mass or more and 0.0100% by mass or less of boron and including the remaining iron and impurities is prepared. Specifically, for example, a steel bar, a steel pipe, a steel plate and the like having the above composition are prepared. Moreover, 0.50 mass% or more and 1.00 mass% or less of chromium may be added to the said steel material. Moreover, 0.015 mass% or more and 0.050 mass% or less of titanium may be added to the said steel material.

  Next, a forming step is performed as a step (S20). In this step (S20), for example, by performing processing such as forging and turning on the steel material prepared in step (S10), the outer ring 11, inner ring 12 and ball 13 shown in FIGS. A molded body formed into a shape is produced.

  Next, a strengthening process layer formation process is implemented as process (S30). In this step (S30), carburizing treatment or carbonitriding treatment is performed on the molded body produced in step (S20). This step can be omitted if the carbon-enriched layer and the nitrogen-enriched layer are not formed on the bearing component.

Next, a quench hardening process is implemented as process (S40). In this step (S40), the molded body heated to a predetermined quenching temperature (a temperature of _one point A or higher) is hardened by being immersed in, for example, a cooling liquid (quenching oil or the like). The quenching temperature can be, for example, 820 ° C. or higher and 850 ° C. or lower.

  Next, a tempering step is performed as a step (S50). In this step (S50), the molded body that has been quenched in the step (S40) is tempered. Specifically, for example, the tempering treatment is performed by holding the molded body for 2 hours or more and 4 hours or less in an atmosphere heated to a temperature range of 160 ° C. or more and 200 ° C. or less.

  Next, a finishing process is performed as a process (S60). In this step (S60), the molded body that has been tempered and heat-treated in step (S50) is processed. Specifically, the bearing part is completed by, for example, polishing the region corresponding to the contact surface of the bearing part on the molded body that has been heat-treated.

  Furthermore, an assembly process is performed as a process (S70). In this step (S70), bearing parts such as the outer ring 11, the inner ring 12 and the balls 13 produced in steps (S10) to (S60) are combined with the separately prepared cage 14 and the like. The deep groove ball bearing 1 in the form is assembled. Thereby, the manufacturing method of the rolling bearing in this Embodiment is completed.

(Embodiment 2)
Next, Embodiment 2 which is another embodiment of the present invention will be described. The bearing component and the rolling bearing in the second embodiment basically have the same structure as that of the first embodiment, and can produce the same effect as well. However, referring to FIG. 4 and FIG. 1, the bearing component and the rolling bearing in the second embodiment are different from those in the first embodiment in the method for forming the reinforcing treatment layer.

  Referring to FIGS. 1 and 4, reinforcement treatment layer 11 </ b> B and reinforcement treatment layer 12 </ b> B are formed on outer ring 11 and inner ring 12 in Embodiment 1 shown in FIG. 1 so as to cover the entire surface, respectively. On the other hand, the outer ring 11 and the inner ring 12 in the second embodiment shown in FIG. 4 are formed with the reinforcing treatment layer 11B and the reinforcement treatment layer 12B, respectively, limited to the outer ring rolling surface 11A and the inner ring rolling surface 12A and the vicinity thereof. Has been. That is, the reinforcing treatment layer 11B is not formed on the outer peripheral surface and the end surface of the outer ring 11 in the second embodiment. Further, the reinforcing treatment layer 12B is not formed on the inner peripheral surface and the end surface of the inner ring 12 in the second embodiment. The reinforcing treatment layers 11B and 12B in the second embodiment are induction hardened layers formed by induction induction hardening.

  Next, a method for manufacturing the bearing component and the rolling bearing in the second embodiment will be described. Referring to FIG. 5, first, after the step (S10) is performed as in the case of the first embodiment, the steel material prepared in step (S10) is formed, and the shapes of outer ring 11 and inner ring 12 are formed. Thus, a molded body formed into a shape is produced.

Next, an induction hardening process is implemented as process (S31). In this step (S31), induction hardening is performed on the molded body produced in step (S20). Specifically, region and its neighboring region corresponding to the outer ring rolling surface 11A and inner ring raceway surface 12A of the produced molded body in step (S20) is induced locally A ₁ transformation point or above the temperature by heating The area is heated. Thereafter, the heated region is strengthening layer 11B is induction hardening layer, 12B is formed by being cooled to a temperature below M _S point (quenching).

  Then, steps (S40) and (S50) are performed in the same manner as in the first embodiment, whereby outer ring 11 and inner ring 12 in the second embodiment are completed. Further, in the step (S70), the outer ring 11 and the inner ring 12 produced in the steps (S10) to (S60), the separately prepared ball 13, the cage 14 and the like are combined to form the deep groove in the above embodiment. The ball bearing 1 is assembled. Thereby, the manufacturing method of the rolling bearing in this Embodiment is completed.

  In outer ring 11 and inner ring 12 in the present embodiment, reinforcing treatment layers 11B and 12B are formed by induction hardening. Therefore, according to the bearing component in the present embodiment, the outer ring 11 and the inner ring 12 that are bearing components having the reinforced treatment layers 11B and 12B can be manufactured in a short time and with high energy efficiency.

  In order to confirm the effect of improving the hardenability by adding boron to steel, a four master test was conducted. The experimental procedure is as follows. First, a steel bar made of steel types having five kinds of composition shown in Table 1 was prepared. In Table 1, the unit of numerical values is mass%, and the balance is iron and impurities. In Table 1, “-” indicates that the corresponding element is not intentionally added. O (oxygen) is an impurity.

  Next, a cylindrical test piece having a diameter of 10 mm and a length of 80 mm is selected from the four types of steel bars excluding S53C-B-1 among the prepared steel bars, and the length direction of the test piece matches the length direction of the steel bar. It cut out and produced. This test piece is heated to 850 ° C. assuming a quenching temperature using a four master test machine, and then cooled at various cooling rates. The change in the size of the test piece during the cooling process is continuously performed using infrared rays. Measured. And from the change of the said dimension, the temperature and time which the test piece of an austenite state transform | transforms into a pearlite, a bainite, a martensite, etc. were confirmed. And the CCT (Continuous Cooling Transformation) diagram was created from the obtained result. The created CCT diagrams are shown in FIGS.

  6, FIG. 7, FIG. 8, and FIG. 9 correspond to the CCT diagrams of SUJ2, S53C, S53C-B-2, and S53C-B-Cr in Table 1, respectively. Moreover, in FIGS. 6-9, the curve of P, B, and M is a curve corresponding to a pearlite transformation, a bainite transformation, and a martensitic transformation, respectively. 6-9, the hardest of the steel material which comprises the said test piece is so excellent that the slowest cooling rate (critical cooling rate) is the slowest among the cooling rates in which a test piece martensite transforms without causing a pearlite transformation. ing. More specifically, the hardenability can be compared using the time until the nose of pearlite transformation as a guide.

  From the comparison between FIG. 7 and FIG. 8, the hardenability of S53C-B-2 in FIG. 8 is greatly improved by the addition of a small amount of boron of 0.0017% by mass (17 ppm) compared to S53C in FIG. doing. And the hardenability of S53C-B-2 is the hardenability substantially equivalent to SUJ2 of FIG. Furthermore, as shown in FIG. 9, by adding Cr, the hardenability is further improved, and for example, it can be applied to a larger bearing such as SUJ3 used as a standard material. I can say that. Cr is more available than Ni and Mo. Therefore, when the size of the bearing exceeds the size where SUJ2 is used, Cr addition is also a promising measure.

  From the above experimental results, according to the bearing component made of steel material with the boron addition amount of 0.0020 mass% or more in the component composition not adding rare metal, it can be applied to the same size as the bearing component in which SUJ2 is adopted as the material It is confirmed that a bearing component applicable to a size equivalent to a bearing component employing SUJ3 as a material can be obtained by further adding Cr.

  An experiment was conducted to confirm the pinning effect (crystal grain refinement effect) due to precipitates when Ti was added to boron-added steel. Specifically, a cylindrical test piece having a diameter of 12 mm and a length of 20 mm was prepared from the steel bar shown in Table 1 above, and after being held at 850 ° C. for 60 minutes, it was immersed in quenching oil held at 90 ° C. Quenched. The treated specimen was cut, polished and corroded, and then the microstructure was observed to examine the size of the prior austenite crystal grains. The survey results are shown in Table 2. 10 and 11 are photographs of the microstructures of S53C and S53C-B-2, respectively.

  Referring to Table 2, FIG. 10 and FIG. 11, the crystal grain size of boron-added steel to which Ti is added is remarkably refined as compared with S53C. And by adding 0.015 mass% of Ti, the crystal grain diameter substantially equivalent to SUJ2 is obtained. Further, in the case where 0.048% by mass of Ti is added, the crystal grains are finer than SUJ2. It is known that refinement of crystal grains is effective in improving bearing life. Therefore, according to the bearing part made of steel to which 0.15% by mass or more of Ti is added, a bearing life superior to the bearing part made of SUJ2 can be expected.

  Test pieces made of each steel type shown in Table 1 were prepared, and the rolling fatigue life was evaluated using a point contact life tester. Specifically, a test piece having a diameter of 12 mm and a length of L22 mm was prepared using the steel materials of each steel type shown in Table 1 above. Then, the test specimen was subjected to submerged quenching, carburizing treatment and quenching, or induction quenching. And the lifetime of the obtained test piece was evaluated with a point contact life tester.

With reference to FIG. 12 and FIG. 13, the point contact rolling life tester 2 includes a drive roller 22, a guide roller 23, and a steel ball 24. The test piece 21 is driven by the drive roller 22 and rotates in contact with the steel ball 24. The steel ball 24 is guided by the guide roller 23 and rolls while exerting a high surface pressure with the test piece 21. The point contact rolling life test machine 2 was operated as described above, and the number of loads (life) until the test piece 21 peeled was investigated. The mating steel balls were 2/4 "steel balls, the contact stress Pmax was 4.4 GPa, the load speed was 46240 cpm, and the lubricating oil was turbine oil VG68. The test results are shown in FIG. Evaluation was made based on the L ₁₀ life obtained from the test results of 8 test pieces each.

  Referring to FIG. 12, the induction-hardened product and the sub-hardened product of S53C had a shorter life than the SUJ2 sub-hardened product (SUJ2 standard). On the other hand, the quenched products of S53C-B-1 and S53C-B-2, which are boron-added steels, had a rolling fatigue life equal to or greater than SUJ2. In addition, since the rolling fatigue life tends to be improved by the addition amount of Ti, it is considered that the refinement of crystal grains contributes to the extension of the rolling fatigue life.

  In the above embodiment, the deep groove ball bearing has been described as an example of the rolling bearing including the bearing component of the present invention. However, the rolling bearing of the present invention is not limited to this, and a needle roller bearing, a cylindrical roller bearing, a tapered roller The bearing component and the rolling bearing of the present invention can be applied to various types of rolling bearings such as a bearing and an angular ball bearing.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The bearing component and rolling bearing of the present invention can be particularly advantageously applied to bearing components and rolling bearings that are required to reduce the rare metal elements contained in the material while ensuring excellent durability.

  DESCRIPTION OF SYMBOLS 1 Deep groove ball bearing, 2 point contact rolling life test machine, 11 outer ring, 11A outer ring rolling surface, 11B, 12B, 13B reinforced processing layer, 11C, 12C, 13C inside, 12 inner ring, 12A inner ring rolling surface, 13 balls , 13A Ball rolling surface, 14 Cage, 21 Test piece, 22 Drive roller, 23 Guide roller, 24 Steel ball.

Claims (13)

  0.40% by mass or more and 0.60% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.10% by mass or more and 1.10% by mass or less of manganese, A bearing component comprising a hardened and hardened steel comprising 0010% by mass and 0.0100% by mass or less of boron, the balance being iron and impurities.   0.40% by mass or more and 0.60% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.10% by mass or more and 1.10% by mass or less of manganese, A bearing component comprising a hardened and hardened steel comprising 0010 mass% to 0.0100 mass% boron and 0.50 mass% to 1.00 mass% chromium, the balance being iron and impurities. .   0.40% by mass or more and 0.60% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.10% by mass or more and 1.10% by mass or less of manganese, A bearing comprising a hardened and hardened steel comprising iron and impurities, the boron containing 0010 mass% to 0.0100 mass% boron and 0.015 mass% to 0.050 mass% titanium. parts.   0.40% by mass or more and 0.60% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.10% by mass or more and 1.10% by mass or less of manganese, Containing 0010 mass% to 0.0100 mass% boron, 0.50 mass% to 1.00 mass% chromium, 0.015 mass% to 0.050 mass% titanium, and the balance Bearing parts made of hardened and hardened steel consisting of iron and impurities. In the steel, a titanium precipitate consisting of at least one selected from the group consisting of titanium carbide, nitride and carbonitride is dispersed,
The bearing component according to claim 3 or 4, wherein an average diameter of the titanium precipitate is 0.1 µm or more and 5 µm or less. Boron precipitates made of boron nitride are dispersed in the steel,
The bearing part according to claim 5, wherein an average diameter of the precipitate including the titanium precipitate and the boron precipitate is 0.1 μm or more and 10 μm or less. The bearing part according to any one of claims 1 to 6, wherein the prior austenite crystal grains of the steel in a cross section of the bearing part are 8000 pieces / mm ² or more.   The bearing component according to any one of claims 1 to 7, wherein the steel has an oxygen content of 15 ppm or less.   A carbon-enriched layer having a carbon concentration higher than the inside and having a carbon concentration of 0.8% by mass to 1.1% by mass is formed in a region including a contact surface that is a surface to be contacted with another bearing component. The bearing component according to any one of claims 1 to 8, wherein .   A nitrogen-enriched layer having a nitrogen concentration higher than the inside and having a nitrogen concentration of 0.01% by mass or more and 0.5% by mass or less is formed in a region including a contact surface that is a surface to be contacted with another bearing component. The bearing component according to any one of claims 1 to 9.   The bearing part of any one of Claims 1-10 in which the hardening process layer by induction hardening is formed in the area | region containing the contact surface which is the surface which should contact another bearing part.   The bearing part according to claim 9, wherein the contact surface has a hardness of 60 HRC or more. A track member;
A plurality of rolling elements arranged in contact with the rolling surface of the raceway member,
At least any one of the said track member and the said rolling element is a rolling bearing which is a bearing component of any one of Claims 1-12.