JP2007182926A - Manufacturing method for needle-like roll bearing raceway member, needle-like roll bearing raceway member, and needle-like roll bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a needle-like roll bearing raceway member whose rolling fatigue life under a severe environment is improved, a needle-like roll bearing having a longer service lifetime even under a severe environment, and a manufacturing method for the needle-like roll bearing raceway member. <P>SOLUTION: The manufacturing method for the needle-like roll bearing raceway member includes a steel member preparation step, a carburizing or carbonitriding hardening step, a high-frequency hardening step, and a finishing step. In the steel member preparation step, a steel member made of steel and shaped into an outline shape of the needle-like roll bearing raceway member is prepared. In the carburizing or carbonitriding hardening step, the steel member is quenched and hardened after executing carburizing or carbonitriding hardening to the steel member. In the high-frequency hardening step, a region including a part to be a rolling face of the needle-like roll bearing raceway member is further quenched and hardened so that a remaining amount of austenite in a region having a depth of ≤0.3 mm from the face to be the rolling face is ≥50 vol.% and ≤70 vol.%. In the finishing step, finish processing is executed to the steel member. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method of manufacturing a raceway member for needle roller bearings, a raceway member for needle roller bearings, and a needle roller bearing, and more specifically, a raceway member for needle roller bearings having a long life even under severe environments. Manufacturing method, needle roller bearing race member and needle roller bearing.

  In recent years, the environment in which a rolling bearing is used has become more severe as the performance of industrial machinery, transportation equipment, and the like in which the rolling bearing is used has become higher. For this reason, rolling members such as race members and rolling elements constituting a rolling bearing are required to have a longer rolling fatigue life, particularly in a harsh environment.

  A needle roller bearing provided with a needle roller having a diameter of a roller as a rolling element of 5 mm or less and a length of the roller of 3 to 10 times the diameter of the roller is a raceway surface of the rolling element. The height of the bearing mainly in the direction of receiving a load in the cross section perpendicular to is small, and the load capacity is large for the size. The needle roller bearing also has a feature that high rigidity is easily obtained. Therefore, the needle roller bearing is expected to be applied to various uses. In a needle roller bearing, due to its structure, slip is likely to occur between a needle roller that is a rolling element and a race member for a needle roller bearing such as a race ring. Therefore, the raceway member for the needle roller bearing is subjected to rolling fatigue accompanied by slip. Therefore, in order to improve the strength against the fatigue, the raceway member for the needle roller bearing is required to improve the fatigue strength in the rolling contact surface that is a surface in contact with the needle roller and the region immediately below the rolling contact surface.

On the other hand, proposals have been made to improve the rolling life of the rolling member by controlling the retained austenite amount, surface hardness, and the like of the surface layer portion of the rolling member within a predetermined range. (For example, see Patent Documents 1 to 5).
JP 2005-90693 A JP 2004-144279 A JP 2003-343577 A JP 2000-234147 A Japanese Patent Laid-Open No. 11-101247

  However, the required characteristics of recent needle roller bearings are becoming more severe, and the above-mentioned measures for improving the life are not necessarily sufficient. Further, in order to improve the price competitiveness of industrial machines, transportation machines, etc. in which needle roller bearings are used, there is a demand for cost reduction for needle roller bearings. Therefore, for example, extending the life by changing the material constituting the needle roller bearing to an expensive material is contrary to the above-mentioned demand for cost reduction.

  Accordingly, an object of the present invention is to provide a needle roller bearing raceway member that has improved rolling fatigue life in a harsh environment while suppressing an increase in manufacturing cost, and a needle roller that has a long life even in a harsh environment. It is to provide a bearing and a manufacturing method thereof.

  The method for manufacturing a raceway member for a needle roller bearing according to the present invention is arranged and used so as to be in contact with a needle roller as a rolling element, and has a rolling surface on which the needle roller rolls. It is a manufacturing method of the bearing race member. And the manufacturing method of the raceway member for needle roller bearings of this invention is equipped with the steel member preparation process, the hardening hardening process, the partial hardening hardening process, and a finishing process. In the steel member preparation step, a steel member made of steel and formed into a schematic shape of a raceway member for needle roller bearings is prepared. In the quench hardening process, after carburizing or carbonitriding is performed on the steel member, the steel member is quenched and hardened. Furthermore, in the partial quench hardening process, the rolling is performed as an area including a portion that becomes a rolling surface of the raceway member for the needle roller bearing, which is a partial area of the steel member quenched and hardened in the quench hardening process. By further quenching and hardening the running region, the amount of retained austenite in the region of the steel member having a depth from the surface to be the rolling surface of 0.3 mm or less is set to 50% by volume or more and 70% by volume or less. . In the finishing process, the finishing process is performed on the steel member whose rolling region has been hardened and hardened in the partial hardening and hardening process, whereby the raceway member for the needle roller bearing is completed.

  Generally, retained austenite is used in rolling members used in harsh environments such as a rolling slip environment where slip occurs between the rolling elements and the raceway member, and a foreign matter mixed environment where hard foreign matter is mixed in the lubricating oil. When present in an appropriate amount, it has a function of improving the rolling fatigue life of the rolling member.

  The amount of retained austenite in the surface layer portion of the rolling member can be increased by increasing the carbon concentration or carbon concentration and nitrogen concentration in the surface layer portion by heat treatment such as carburizing or carbonitriding and then performing quenching. . When carburizing or carbonitriding is performed under general conditions, the amount of retained austenite in the surface layer portion of the rolling member made of steel is about 40% by volume at maximum, and in order to obtain the amount of retained austenite more than that, the carburizing temperature It is necessary to adopt special carburizing conditions or carbonitriding conditions such as increasing the slag or increasing the carburizing time. Therefore, if carburizing or carbonitriding is carried out under conditions that increase the amount of retained austenite, the manufacturing cost of the rolling member will increase.

  On the other hand, the inventor has intensively studied a method for easily increasing the amount of retained austenite in the raceway member for needle roller bearings. As a result, the depth from the rolling surface that has a great influence on the rolling fatigue life of the surface layer portion of the raceway member for needle roller bearings, for example, the raceway member for needle roller bearings, is greatly reduced by the following method. It became clear that the amount of retained austenite in the region of .3 mm or less can be easily increased. That is, first, by performing carburizing or carbonitriding, the amount of carbon, or the amount of carbon and the amount of nitrogen in the surface layer portion of the raceway member for needle roller bearings is increased. Then, by reheating the rolling region as a region including the portion that becomes the rolling surface of the raceway member for the needle roller bearing, carbon and nitrogen existing as precipitates combined with other elements in the region are steel. Quenching and hardening are performed by quenching after dissolving in the structure. Thereby, the amount of retained austenite in the region where the depth from the surface that should be the rolling surface is 0.3 mm or less can be increased to 50 volume% or more and 70 volume% or less. That is, according to the method for manufacturing a raceway member for a needle roller bearing of the present invention, the amount of retained austenite in a region where the depth from the rolling surface is 0.3 mm or less while easily suppressing an increase in manufacturing cost. More specifically, a raceway member for a needle roller bearing having a retained austenite amount of 50 volume% or more and 70 volume% or less can be manufactured.

  Preferably, in the manufacturing method of the raceway member for a needle roller bearing, in the finishing process, in the raceway member for the needle roller bearing completed by performing the finishing process, the depth from the rolling surface is 0.3 mm or less. The amount of retained austenite at 50 vol% or more and 70 vol% or less, and the compressive stress in the region where the depth from the rolling surface is 0.05 mm or more and 0.1 mm or less is 250 MPa or more, and the surface of the raceway member for needle roller bearings Finishing is performed so that the amount of retained austenite in the region where the depth from the steel is 1 mm or more is 10% by volume or less.

  As described above, the retained austenite has a function of improving the rolling fatigue life of the raceway member for needle roller bearings. On the other hand, residual austenite transforms into martensite over time during use of the raceway member for needle roller bearings. Since the transformation involves a volume change, the retained austenite may cause deterioration in the dimensional stability of the needle roller bearing race member, which may adversely affect the rolling fatigue life of the needle roller bearing race member. is there. Also, since retained austenite has a lower hardness than martensite, if the retained austenite increases too much, the hardness required for the raceway member for needle roller bearings cannot be obtained, and the rolling fatigue of the raceway member for needle roller bearings There is also a risk that the service life may be reduced. The present inventor has examined the relationship between the retained austenite amount, compressive stress, dimensional change over time, hardness and rolling fatigue life of the raceway member for needle roller bearings, and obtained the following knowledge. That is, in the raceway member for needle roller bearings, the amount of retained austenite in the region where the depth from the rolling surface is 0.3 mm or less is extremely large, specifically 50 vol% or more and 70 vol% or less. During use of the raceway member for the needle roller bearing, residual austenite having a relatively low hardness is plastically deformed in the vicinity of the rolling surface. Due to this plastic deformation, the rolling contact surface is deformed so that the stress applied is relaxed, and the retained austenite is transformed into martensite by being induced by the deformation. As a result, the hardness of the deformed portion is increased and a compressive stress is generated in the vicinity of the rolling surface, so that the rolling fatigue life of the raceway member for needle roller bearings is improved (self-strengthening ability of retained austenite). In particular, the above effect is remarkable in a region where the load stress is high on the rolling surface, for example, a region where an edge load occurs. Therefore, the effect of improving the rolling fatigue life is great in a raceway member for a needle roller bearing in which a region having a high load stress is generated on the rolling surface.

  Moreover, the rolling fatigue life of the raceway member for needle roller bearings improves by making the compressive stress in the area | region whose depth from a rolling surface is 0.05 mm or more and 0.1 mm or less into 250 Mpa or more. That is, in general, compressive stress may be generated on the rolling surface due to the influence of finishing processing such as grinding and polishing performed on the rolling surface in the finishing process of the needle roller bearing raceway member. However, not only the rolling surface (surface) but also the compressive stress in the region where the depth from the rolling surface is 0.05 mm or more and 0.1 mm or less has a great influence on the rolling fatigue life of the raceway member for needle roller bearings. Thus, the rolling fatigue life is greatly improved by setting the compressive stress in the region to 250 MPa or more. This is considered to be because crack generation and propagation due to rolling fatigue are suppressed not only in the rolling surface (surface) but also in the region immediately below the rolling surface.

  Further, the amount of retained austenite in the region where the depth from the surface of the raceway member for needle roller bearings is 1 mm or more is 10% by volume or less, so that the amount of retained austenite with low hardness is suppressed in the core portion, and needle rollers Sufficient rigidity is ensured for the entire bearing member. Further, by suppressing the volume change due to the transformation in the core portion of the needle roller bearing raceway member, it is possible to restrain the dimensional change over time of the needle roller bearing raceway member as a whole.

  Here, if the amount of retained austenite in the region where the depth from the rolling surface is 0.3 mm or less is less than 50% by volume, the self-reinforcing ability of the retained austenite is not sufficient, and if it exceeds 70% by volume, the plasticity of the retained austenite Due to deformation and transformation to martensite, it is difficult to ensure sufficient accuracy of the rolling surface. Therefore, the amount of retained austenite in the region where the depth from the rolling surface is 0.3 mm or less is preferably 50% by volume or more and 70% by volume or less as described above. Moreover, in the raceway member for needle roller bearings used under particularly severe conditions, it is more preferable that the amount of retained austenite is 60% by volume or more and 70% by volume or less.

  Furthermore, in the method for manufacturing a raceway member for a needle roller bearing, a region in which the amount of retained austenite is 50% by volume or more and 70% by volume or less is a rolling surface surface region having a depth from the rolling surface of 0.3 mm or less. The finishing step may be performed so that the amount of retained austenite is limited to 40% by volume or less in a region where the depth from the surface in the surface region excluding the surface region of the rolling surface is less than 1 mm.

  As a result, a necessary and sufficient amount of retained austenite can be ensured in the surface area of the rolling surface that greatly affects the rolling fatigue life, and the aforementioned self-strengthening ability of retained austenite can be exhibited. On the other hand, limiting the amount of residual austenite in the region where the depth from the surface in the surface region excluding the surface region of the rolling surface is less than 1 mm by limiting the region having a very large amount of residual austenite to the surface region of the rolling surface. As a result, the dimensional change of the entire needle roller bearing race member with time can be suppressed to a practically sufficient range. As a result, the rolling fatigue life of the needle roller bearing race member can be further improved. In order to further improve the dimensional stability, it is preferable that the amount of retained austenite in a region where the depth from the surface in the surface region excluding the rolling surface layer region is less than 1 mm is 30% by volume or less.

  In addition, according to the manufacturing method of the raceway member for needle roller bearings of the present invention, the amount of retained austenite in the region having a depth of 0.3 mm or less from the surface to be the rolling surface in the partial quench hardening process is 50 volumes. % To 70% by volume. Therefore, the amount of retained austenite is not reduced to less than 50% by volume due to processing-induced transformation by finishing such as grinding and polishing in the finishing process, so that the above-mentioned amount of retained austenite is 50% by volume to 70% from the surface to a predetermined depth. % Or less can be satisfied. Note that the amount of retained austenite may be 50% by volume or less on the surface due to processing-induced transformation, but even in that case, the residual amount of 50% by volume or more remains in a region having a depth of 50 μm from the surface, which is a region where there is no influence of processing. All you need is austenite. That is, if the amount of retained austenite is 50% by volume or more and 70% by volume or less for the entire region having a depth of 0.3 mm or less from the surface to be the rolling surface, the condition for the amount of retained austenite is satisfied. . Further, by adjusting the finishing conditions such as grinding and polishing in the finishing step, the above-described compressive stress condition can be satisfied. Furthermore, by selecting carbon steel, carburized steel, bearing steel, etc. as the material for the raceway member for needle roller bearings, and appropriately setting the conditions for carburizing or carbonitriding in the quench hardening process, the above-mentioned needle roller bearing It is possible to satisfy the condition that the amount of retained austenite is 10% by volume or less in a region where the depth from the surface of the track member is 1 mm or more. Manufacturing conditions for satisfying the conditions for the amount of retained austenite and the compressive stress can be experimentally determined in consideration of the size, shape, etc. of the raceway member for needle roller bearings.

  In the method for manufacturing a raceway member for a needle roller bearing of the present invention, preferably, the rolling region is quenched and hardened in the partial quench hardening step after the partial quench hardening step and before the finishing step. Further, a partial plastic working step of performing plastic working on a portion that becomes a rolling surface that is a part of the steel member is further provided.

  As a result, even in applications where the rolling contact surface is not subject to sufficient plastic deformation by using needle roller bearing race members, it is possible to assist in the self-strengthening ability of retained austenite by performing plastic working in advance. In addition, the rolling fatigue life can be improved.

  In the manufacturing method of the raceway member for the needle roller bearing of the present invention, preferably, in the finishing step, the depth from the rolling surface is 0.05 mm or more in the raceway member for the needle roller bearing completed by performing the finishing step. Finishing is performed so that the compressive stress in the region of 0.1 mm or less is 500 MPa or more, and the amount of retained austenite in the region of 1 mm or more in depth from the surface of the raceway member for needle roller bearings is 10% by volume or less. Is done.

  By causing the compressive stress in the region where the depth from the rolling surface is 0.05 mm or more and 0.1 mm or less to be 500 MPa or more, generation and propagation of cracks due to rolling fatigue is suppressed, and the raceway member for needle roller bearings It is possible to improve the rolling fatigue life. Further, by suppressing the amount of retained austenite in the core portion, the rigidity and dimensional stability of the entire needle roller bearing race member can be ensured.

  The compressive stress condition is optimal by experimentally selecting the finishing conditions such as grinding and polishing after performing the partial plastic working process as described above. This can be achieved by determining the conditions. In addition, the condition that the amount of retained austenite is 10% by volume or less in the region where the depth from the surface of the above-mentioned needle roller bearing raceway member is 1 mm or more is the selection of the material for the needle roller bearing raceway member. This can be achieved by optimizing the conditions for carburizing or carbonitriding in the quench hardening process.

  In the method for producing a raceway member for a needle roller bearing according to the present invention, preferably, the heating in the partial quenching and hardening step is performed by induction heating. By adopting induction heating that is relatively easy to heat, such as induction heating, as the heating method in the partial quenching and hardening process, it is relatively easy to apply only the vicinity of the portion that becomes the rolling surface of the raceway member for the needle roller bearing. Quenching can be carried out by heating.

  The needle roller bearing race member according to one aspect of the present invention is manufactured by the above-described method for manufacturing a needle roller bearing race member. Providing a raceway member for a needle roller bearing that is manufactured by the above-described method for producing a raceway member for a needle roller bearing and that has an improved rolling fatigue life in a harsh environment while suppressing an increase in production cost. be able to.

  The needle roller bearing according to one aspect of the present invention includes a race member and a plurality of needle rollers that are in contact with the race member and disposed on an annular raceway. And the said track member is the above-mentioned track member for needle roller bearings.

  According to the needle roller bearing in one aspect of the present invention, since the needle roller bearing raceway member having the above-described excellent characteristics is provided, an increase in manufacturing cost is suppressed and even in a harsh environment. A long-life needle roller bearing can be provided.

  A raceway member for a needle roller bearing according to another aspect of the present invention is disposed and used so as to contact a needle roller as a rolling element, and has a needle shape having a rolling surface on which the needle roller rolls. This is a roller bearing race member. And the amount of residual austenite in the area | region whose depth from a rolling surface is 0.3 mm or less is 50 volume% or more and 70 volume% or less, and the area | region whose depth from a rolling surface is 0.05 mm or more and 0.1 mm or less The amount of retained austenite in the region where the compressive stress at 250 MPa or more and the depth from the surface is 1 mm or more is 10% by volume or less.

  As described above, retained austenite has a function of improving the rolling fatigue life of the raceway member for needle roller bearings, while causing deterioration in dimensional stability and a decrease in hardness. According to the raceway member for a needle roller bearing of the present invention, the amount of retained austenite in the region where the depth from the rolling surface is 0.3 mm or less is 50% by volume or more and 70% by volume or less, whereby the retained austenite self By utilizing the strengthening ability, it is possible to improve the rolling fatigue life of the raceway member for the needle roller bearing. In particular, the effect of improving the rolling fatigue life is great in a raceway member for a needle roller bearing in which a region having a high load stress is generated on the rolling surface. Even when the amount of retained austenite in the region immediately below the rolling surface is less than 50% by volume, the amount of retained austenite is 50% as a whole in the region where the depth from the surface to be the rolling surface is 0.3 mm or less. If the volume% is 70% by volume or more, the above-mentioned residual austenite amount condition is satisfied. Moreover, the rolling fatigue life of the raceway member for needle roller bearings improves by making the compressive stress in the area | region whose depth from a rolling surface is 0.05 mm or more and 0.1 mm or less into 250 Mpa or more. Further, by setting the retained austenite amount in the region where the depth from the surface of the needle roller bearing raceway member is 1 mm or more to 10 volume% or less, the rigidity of the needle roller bearing raceway member as a whole is ensured. , Dimensional change over time can be suppressed.

  Here, if the amount of retained austenite in the region where the depth from the rolling surface is 0.3 mm or less is less than 50% by volume, the self-strengthening of the retained austenite is not sufficient, and if it exceeds 70% by volume, the rolling surface is sufficient. It is difficult to ensure accurate accuracy. Therefore, the amount of retained austenite in the region where the depth from the rolling surface is 0.3 mm or less is preferably 50% by volume or more and 70% by volume or less as described above.

  Further, in the raceway member for needle roller bearings, the region in which the amount of retained austenite is 50% by volume or more and 70% by volume or less is limited to the rolling surface surface layer region having a depth from the rolling surface of 0.3 mm or less, The amount of retained austenite in a region where the depth from the surface in the surface region excluding the rolling surface surface layer region is less than 1 mm may be 40% by volume or less.

  As a result, a necessary and sufficient amount of retained austenite can be ensured in the surface area of the rolling surface that greatly affects the rolling fatigue life, and the aforementioned self-strengthening ability of retained austenite can be exhibited. On the other hand, limiting the amount of residual austenite in the region where the depth from the surface in the surface region excluding the surface region of the rolling surface is less than 1 mm by limiting the region having a very large amount of residual austenite to the surface region of the rolling surface. As a result, the dimensional change of the entire needle roller bearing race member with time can be suppressed to a practically sufficient range. As a result, the rolling fatigue life of the needle roller bearing race member can be further improved. In order to further improve the dimensional stability, it is preferable that the amount of retained austenite in a region where the depth from the surface in the surface region excluding the rolling surface layer region is less than 1 mm is 30% by volume or less.

  A needle roller bearing according to another aspect of the present invention includes a race member and a plurality of needle rollers that are in contact with the race member and disposed on an annular raceway. The track member is a needle roller bearing track member according to another aspect of the present invention described above.

  According to the needle roller bearing in another aspect of the present invention, since the raceway member for the needle roller bearing having the above-described excellent characteristics is provided, a needle roller bearing having a long life even in a severe environment is provided. can do.

  Here, the amount of retained austenite is calculated by measuring the diffraction intensities of the martensite α (211) plane and the austenite γ (220) plane using, for example, an X-ray diffractometer (XRD). Can do. In addition, the compressive stress can be easily measured by, for example, an X-ray stress measuring device in a direction parallel to the rolling surface.

  As apparent from the above description, according to the raceway member for a needle roller bearing and the method for producing a needle roller bearing of the present invention, the rolling fatigue life in a harsh environment can be reduced while suppressing an increase in production cost. An improved needle roller bearing raceway member and a long-life needle roller bearing can be manufactured even in a harsh environment. Further, according to the raceway member for needle roller bearing and the needle roller bearing of the present invention, the raceway member for needle roller bearing with improved rolling fatigue life under a severe environment and a long life under a severe environment. Needle roller bearings can be provided.

  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)
FIG. 1 is a schematic cross-sectional view showing a configuration of a thrust needle roller bearing as a needle roller bearing provided with a raceway member for needle roller bearings according to Embodiment 1, which is an embodiment of the present invention. FIG. 2 is a schematic partial sectional view of a raceway ring as a raceway member for a needle roller bearing provided in the thrust needle roller bearing of FIG. FIG. 3 is a schematic sectional view of a needle roller as a rolling element provided in the thrust needle roller bearing of FIG. 1 to 3, a thrust needle roller bearing as a needle roller bearing in Embodiment 1 of the present invention, a race ring as a race member for needle roller bearings, and a needle roller as a rolling element (needle shape) The structure of the roller) will be described.

  Referring to FIG. 1, a thrust needle roller bearing 1 according to Embodiment 1 has a disk shape and is a pair of raceway members for needle roller bearings arranged such that one main surface faces each other. The track ring 11, a plurality of needle rollers 13 as rolling elements, and an annular retainer 14 are provided. The plurality of needle rollers 13 are in contact with the raceway rolling surface 11A formed on one main surface of the pair of raceways 11 facing each other, and are arranged at a predetermined pitch in the circumferential direction by the cage 14. It is rotatably held on an annular track. With the above configuration, the pair of race rings 11 of the thrust needle roller bearing 1 can rotate relative to each other.

  Next, a description will be given of the race 11 as a needle roller bearing race member constituting the thrust needle roller bearing 1. Referring to FIG. 2, raceway ring 11 as a needle roller bearing raceway member is arranged and used so as to be in contact with needle roller 13 as a rolling element, and raceway rolling for needle roller 13 to roll is performed. This is a needle roller bearing race member having a running surface 11A. The amount of retained austenite in the rolling surface surface region 11B, which is a region having a depth of 0.3 mm or less from the raceway rolling surface 11A, is 50 vol% or more and 70 vol% or less, and the depth from the raceway rolling surface 11A. The compressive stress in the region of 0.05 mm or more and 0.1 mm or less is 250 MPa or more, and the retained austenite amount in the raceway ring core region 11D in which the depth from the surface is 1 mm or more is 10% by volume or less. .

  Furthermore, in the race 11 of the first embodiment, the region where the retained austenite amount is 50% by volume or more and 70% by volume or less is limited to the rolling surface surface layer region 11B, and the surface region excluding the rolling surface surface layer region 11B. The amount of retained austenite in the raceway ring surface layer portion 11C, which is a region having a depth from the surface of less than 1 mm, is 40% by volume or less.

  According to the race 11 of the first embodiment, the amount of retained austenite in the rolling surface surface layer region 11B is set to 50% by volume or more and 70% by volume or less, thereby utilizing the self-strengthening ability of the retained austenite. The rolling fatigue life can be improved. That is, when the thrust needle roller bearing 1 is operated, the retained austenite having a relatively low hardness is plastically deformed. By this plastic deformation, the raceway rolling surface 11A is deformed so as to relieve the stress applied, and induced by the deformation, the residual austenite is transformed into martensite. As a result, the hardness of the deformed portion is increased, and a compressive stress is generated in the vicinity of the raceway rolling surface 11A, so that the rolling fatigue life of the raceway 11 is improved (self-strengthening ability of retained austenite). In particular, in the raceway 11 such that the above-mentioned effect becomes remarkable in a region where the load stress is high in the raceway rolling surface 11A, for example, a region where edge load occurs, and a region where the load stress is high in the raceway raceway 11A. Greatly improves rolling fatigue life.

  Further, in the raceway ring 11 of the first embodiment, the rolling stress of the raceway ring 11 is increased when the compressive stress in the region where the depth from the raceway rolling surface 11A is 0.05 mm or more and 0.1 mm or less is 250 MPa or more. Dynamic fatigue life is improved. That is, by setting the compressive stress not only in the raceway rolling surface 11A but also in the region where the depth from the raceway rolling surface 11A having a great influence on the rolling fatigue life is 0.05 mm or more and 0.1 mm or less to 250 MPa or more. In addition, the rolling fatigue life is greatly improved. When the thrust needle roller bearing 1 is operated, the raceway rolling surface 11A and the region immediately below the plastic roller are subjected to plastic working, and martensitic transformation of retained austenite proceeds. By the transformation accompanied by the volume expansion, the compressive stress in the region where the depth from the raceway rolling surface 11A is 0.05 mm or more and 0.1 mm or less further increases and contributes to the improvement of the rolling fatigue life.

  Furthermore, in the raceway ring 11 of the first embodiment, the retained austenite amount in the raceway ring core region 11D is set to 10% by volume or less, so that sufficient rigidity is secured as a whole of the raceway ring 11, and the dimension with time Change can be suppressed.

  Furthermore, in the race 11 of the first embodiment, the region in which the retained austenite amount is 50% by volume or more and 70% by volume or less is limited to the rolling surface surface layer region 11B, and the retained austenite amount in the track ring surface layer portion 11C. Is 40% by volume or less. For this reason, necessary and sufficient retained austenite is secured in the rolling surface surface region 11B that greatly affects the rolling fatigue life, so that the self-strengthening ability of the retained austenite is exhibited and the retained austenite in the raceway surface layer portion 11C. By suppressing the amount, sufficient dimensional stability and hardness of the race 11 are ensured. As a result, the rolling fatigue life of the race 11 is further improved.

  Next, the needle roller 13 as a rolling element constituting the thrust needle roller bearing 1 will be described. Referring to FIG. 3, needle roller 13 according to the first embodiment basically has the same configuration as raceway ring 11 as the raceway member for the needle roller bearing described based on FIG. 2. That is, the needle roller 13 as a rolling element is in a rolling surface surface layer region 13B that is a region having a depth of 0.3 mm or less from the needle roller rolling surface 13A that is a surface in contact with the raceway ring 11 that is a raceway member. The amount of retained austenite is 50% by volume or more and 70% by volume or less, the compressive stress in the region where the depth from the needle roller rolling surface 13A is 0.05 mm or more and 0.1 mm or less is 250 MPa or more, and the depth from the surface The amount of retained austenite in the needle roller core region 13D, which is a region of 1 mm or more, is 10% by volume or less.

  Furthermore, in the needle roller 13 of the first embodiment, the region where the retained austenite amount is 50% by volume or more and 70% by volume or less is limited to the rolling surface surface region 13B, and the surface region excluding the rolling surface surface layer region 13B. The amount of retained austenite of the surface portion 13C of the needle roller, which is a region having a depth from the surface of less than 1 mm, is 40% by volume or less.

  According to the needle roller 13 of the first embodiment, similarly to the race ring 11, the amount of retained austenite in the rolling surface surface layer region 13B is set to 50% by volume or more and 70% by volume or less, whereby the self-reinforcing ability of the retained austenite is increased. It can be used to improve the rolling fatigue life. Further, the rolling fatigue life of the needle roller 13 is improved by setting the compressive stress in the region where the depth from the needle roller rolling surface 13A is 0.05 mm or more and 0.1 mm or less to 250 MPa or more. Further, in the needle roller 13 according to the first embodiment, the amount of retained austenite in the needle roller core region 13D is 10% by volume or less, so that sufficient rigidity is secured as a whole of the needle roller 13 and the time-dependent dimension. Change can be suppressed.

  Furthermore, in needle roller 13 of the first embodiment, the region in which the amount of retained austenite is 50% by volume or more and 70% by volume or less is limited to rolling surface surface layer region 13B, and the amount of retained austenite in needle roller surface layer portion 13C. Is 40% by volume or less. Therefore, the self-reinforcing ability of retained austenite is exhibited and sufficient dimensional stability and hardness of the needle roller 13 are ensured. As a result, the rolling fatigue life of the needle roller 13 is further improved.

  Next, a description will be given of a method of manufacturing the raceway ring 11 as the raceway member for the needle roller bearing, the needle roller 13 as the rolling element, and the thrust needle roller bearing 1 as the needle roller bearing in the first embodiment. FIG. 4 is a diagram showing an outline of a method for manufacturing the bearing ring, the needle roller and the thrust needle roller bearing in the first embodiment. With reference to FIG. 4, the manufacturing method of the bearing ring, needle roller, and thrust needle roller bearing in Embodiment 1 is demonstrated.

  Referring to FIG. 4, first, a steel member preparation step is performed in which a steel member made of steel and formed into a schematic shape of raceway ring 11 or needle roller 13 is prepared. Specifically, by performing processing such as forging and turning on a material such as a steel bar made of carburized steel, carbon steel, bearing steel or the like, the bearing ring 11 and the needle roller 13 shown in FIG. The steel member shape | molded by the following general shape is prepared.

  Next, referring to FIG. 4, after performing carbonitriding on the steel member, the carbonitriding and quenching process as a quench hardening process for quench hardening, and quench hardening in the carbonitriding and quenching process The rolling region should be a rolling surface by further quenching and hardening a rolling region as a region including a portion that becomes a rolling surface of the race 11 or the needle roller 13, which is a partial region of the formed steel member. A heat treatment step is performed including an induction hardening step as a partial quench hardening step in which the amount of retained austenite in the region of the steel member having a depth of 0.3 mm or less from the surface is 50% by volume or more and 70% by volume or less. The Details of this heat treatment step will be described later.

  Next, with reference to FIG. 4, a finishing process is implemented. Specifically, the raceway ring 11 and the needle roller 13 are finished by performing a finishing process such as a grinding process on the steel member that has been subjected to the heat treatment process. Thereby, the raceway ring 11 or the needle roller 13 of Embodiment 1 is completed.

  Further, referring to FIG. 4, an assembly process is performed. Specifically, referring to FIG. 1, for example, the thrust needle roller bearing 1 as a needle roller bearing is assembled by combining the raceway ring 11 and the needle roller 13 with the cage 14 and the like.

  Next, the heat treatment process will be described in detail. FIG. 5 is a diagram for explaining the details of the heat treatment process for the raceway and needle roller included in the method of manufacturing the raceway, needle roller and thrust needle roller bearing in the first embodiment. In FIG. 5, the horizontal direction indicates time, and the time elapses toward the right. In FIG. 5, the vertical direction indicates the temperature, and the higher the temperature, the higher the temperature. With reference to FIG. 5, the detail of the heat processing process implemented with respect to the steel member of Embodiment 1 is demonstrated.

Referring to FIG. 5, the steel member prepared in the steel member preparation step is heated to a temperature of 800 ° C. or higher and 900 ° C. or lower, which is a temperature of A ₁ point or higher, for example, 850 ° C., and is 30 minutes or longer and 300 minutes or shorter. For example, 120 minutes. At this time, by heating in an atmosphere in which ammonia (NH ₃ ) is added to the RX gas and the enriched gas, the carbon concentration and the nitrogen concentration in the surface layer portion of the steel member are adjusted to desired concentrations. Thereafter, the steel member is immersed, for example, in oil at 100 ° C. (oil cooling), so that the steel member is cooled from a temperature of A ₁ point or higher to a temperature of _Ms point or lower. As described above, the carbonitriding and quenching process in which the steel member is quenched and hardened is performed. In this carbonitriding and quenching step, the retained austenite amount in the raceway ring surface layer portion 11C and the needle roller surface layer portion 13C is 15% by volume to 40% by volume, more preferably 15% by volume to 30% by volume, and the raceway ring core. The carbon concentration and the nitrogen concentration in the surface layer portion of the steel member are adjusted so that the amount of retained austenite in the part region 11D and the needle roller core region 13D is 10% by volume or less. The retained austenite amount of the bearing ring surface layer portion 11C and the needle roller surface layer portion 13C is 40% by volume or less, preferably 30% by volume or less because the smaller the amount, the better the dimensional stability. In order to make the amount of retained austenite of the running surface region 11B, 13B 50% by volume or more, it is preferably 15% by volume or more.

Here, the point A ₁ in the case of heating the steel refers to a point that the structure of the steel corresponds to the temperature to start the transformation from ferrite to austenite. Further, the M _s point means a point corresponding to a temperature at which martensite formation starts when the austenitized steel is cooled.

Further, the hardened and hardened steel member is heated to a temperature of 150 ° C. or higher and 700 ° C. or lower, which is a temperature of A ₁ or less, for example, 180 ° C., and is held for 30 minutes or longer and 200 minutes or shorter, for example, 120 minutes. Then, it is cooled in air at room temperature (air cooling). Thereby, the first tempering step is completed. Here, when importance is attached to the rigidity of the raceway member for the needle roller bearing, the tempering temperature is preferably 150 ° C. or higher and 250 ° C. or lower in order to avoid a significant decrease in hardness due to tempering. Further, when plastic working such as caulking is performed on a region other than the rolling region, the tempering temperature is preferably 500 ° C. or higher and 700 ° C. or lower in consideration of ease of processing.

Next, referring to FIG. 5, for the steel member for which the first tempering process has been completed, the region including the rolling surface surface layer regions 11 </ b> B and 13 </ b> B is heated at a temperature of A ₁ point or higher by high-frequency heating. An induction hardening process is carried out in which heating is performed at a temperature of 800 ° C. or higher and 1000 ° C. or lower and held for 0.1 seconds or longer and 3 seconds or shorter, for example 0.5 seconds, and then cooled by spraying water. In the high-frequency heating, by adjusting the frequency and output, it is possible to heat only the target portion locally with relative ease. Therefore, high frequency heating is suitable as a heating method in the partial quenching and curing step in the production method of the present invention. In order to perform a desired heat treatment, the optimum heating condition can be experimentally determined by adjusting the above-described frequency, output, heating time, and the like. In particular, in the present method, it is necessary to increase the retained austenite only in the shallow region of the surface layer. Therefore, a high frequency capable of locally increasing the object to be processed, for example, a short time at 100 kHz to 150 kHz, for example, 0 Heating for 1 second or more and 1 second or less is desirable. In this induction hardening process, the rolling surface by the surface layer region 11B and 13B to become carbide region or the like is dissolved, and reduced M _S point below 70 vol% to 50 vol% retained austenite amount of the area It becomes possible. Further, since _{the M S} point in the region is lower than that of the core region, the depth of the bearing washer raceway surface 11A or needle roller rolling surface 13A is a compressive stress in 0.1mm or less in the region than 0.05mm It becomes possible to set it as 250 Mpa or more. Thereafter, the second tempering step is performed under the same conditions as the first tempering step.

  With the above procedure, the heat treatment process of the raceway and needle roller included in the method of manufacturing the raceway, needle roller, and thrust needle roller bearing in the first embodiment is completed. By the manufacturing method of the thrust needle roller bearing including the heat treatment step, the bearing ring, the needle roller, and the thrust needle roller bearing of the first embodiment can be manufactured.

(Embodiment 2)
FIG. 6 is a schematic cross-sectional view showing a configuration of a radial needle roller bearing as a needle roller bearing provided with a raceway member for needle roller bearings according to a second embodiment which is an embodiment of the present invention. FIG. 7 is a schematic partial sectional view of a bearing ring (outer ring) as a needle roller bearing race member provided in the radial needle roller bearing of FIG. FIG. 8 is a schematic partial cross-sectional view of a bearing ring (inner ring) as a needle roller bearing race member provided in the radial needle roller bearing of FIG. With reference to FIGS. 6-8, the structure of the radial needle roller bearing as a needle roller bearing in Embodiment 2 of this invention and the bearing ring as a track member for needle roller bearings is demonstrated.

  Referring to FIG. 6, radial needle roller bearing 2 of the second embodiment and thrust needle roller bearing 1 of the first embodiment have basically the same configuration and have the same effects. However, the configuration of the race is different. That is, the radial needle roller bearing 2 is disposed between an annular outer ring 21 as a needle roller bearing race member, an annular inner ring 22 disposed inside the outer ring 21, and the outer ring 21 and the inner ring 22. And a plurality of needle rollers 23 as rolling elements held by an annular cage 24. An outer ring rolling surface 21 </ b> A is formed on the inner circumferential surface of the outer ring 21, and an inner ring rolling surface 22 </ b> A is formed on the outer circumferential surface of the inner ring 22. The outer ring 21 and the inner ring 22 are arranged so that the inner ring rolling surface 22A and the outer ring rolling surface 21A face each other. Furthermore, the plurality of needle rollers 23 are arranged on an annular track by having their outer peripheral surfaces in contact with the inner ring rolling surface 22A and the outer ring rolling surface 21A and being arranged at a predetermined pitch in the circumferential direction by the cage 24. It is held so that it can roll freely. With the above configuration, the outer ring 21 and the inner ring 22 of the radial needle roller bearing 2 can be rotated relative to each other.

  2, 3, 7 and 8, outer ring 21 and inner ring 22 of the second embodiment correspond to raceway ring 11 of the first embodiment, and basically have the same configuration and effects. is doing. More specifically, the outer ring 21 and the inner ring 22 of the second embodiment are the outer ring rolling surface 21A, the inner ring rolling surface 22A, and the rolling surface corresponding to the rolling ring rolling surface 11A of the bearing ring 11 of the first embodiment. Rolling surface surface layer region 21B and rolling surface surface layer region 22B corresponding to the surface layer region 11B, outer ring surface layer portion 21C and inner ring surface layer portion 22C corresponding to the raceway ring surface layer portion 11C, and outer ring core portion corresponding to the raceway ring core portion region 11D. It has a region 21D and an inner ring core region 22D. The needle roller 23 of the second embodiment has basically the same configuration as the needle roller 13 of the first embodiment.

  However, the needle roller bearing raceway member and needle roller of the second embodiment and the needle roller bearing raceway member and needle roller of the first embodiment are different from each other due to the difference in the manufacturing method. . Hereinafter, the manufacturing method of the raceway member for needle roller bearings of Embodiment 2, a needle roller, and a radial needle roller bearing is demonstrated.

  FIG. 9 is a diagram showing an outline of a method for manufacturing needle roller bearing race members, needle rollers, and radial needle roller bearings in the second embodiment. FIG. 10 is a view for explaining details of the heat treatment process for the needle roller bearing raceway member and the needle roller included in the method for manufacturing the needle roller bearing raceway member, needle roller and radial needle roller bearing in the second embodiment. FIG. In FIG. 10, the horizontal direction indicates time, and the time elapses toward the right. In FIG. 10, the vertical direction indicates the temperature, and the higher the temperature, the higher the temperature. With reference to FIG. 9 and FIG. 10, the manufacturing method of the raceway member for needle roller bearings of Embodiment 2, a needle roller, and a radial needle roller bearing is demonstrated.

  Referring to FIG. 9, the needle roller bearing raceway member, the needle roller and the radial needle roller bearing manufacturing method of the second embodiment are basically the needle shape of the first embodiment described based on FIG. The roller bearing race member, needle roller, and thrust needle roller bearing have the same configuration as the manufacturing method. However, in the second embodiment, the carburizing and quenching process is performed in place of the carbonitriding and quenching process in the heat treatment process, and the rolling surface that is a part of the steel member that is hardened and hardened in the heat treatment process, and This is different from the first embodiment in that a shot peening process as a partial plastic working process for performing plastic working is performed on the portion to be formed. Hereinafter, the difference will be described.

In the carburizing and quenching step, as shown in FIG. 10, the steel member prepared in the steel member preparation step is heated to a temperature of 900 ° C. or higher and 1000 ° C. or lower, which is a temperature of A ₁ point or higher, for example, 940 ° C. A carburizing / diffusion process is performed for 150 minutes to 600 minutes, for example, 480 minutes. At this time, the carbon concentration of the surface layer portion of the steel member is adjusted to a desired concentration by heating in an atmosphere of carburizing gas containing RX gas. Thereafter, the steel member is maintained at a temperature of 780 ° C. or higher and 880 ° C. or lower, which is a temperature of A ₁ point or higher, for example, 840 ° C., and immersed in oil of 100 ° C. (oil cooling), for example, A ₁ point A quenching step of cooling from the above temperature to a temperature below the M _s point is performed. As described above, the carburizing and quenching process in which the steel member is quenched and hardened is performed. In this carburizing and quenching step, the amount of retained austenite in the outer ring surface layer portion 21C and the inner ring surface layer portion 22C is 15% by volume to 40% by volume, more preferably 15% by volume to 30% by volume, and the outer ring core region 21D and The carbon concentration of the surface layer portion of the steel member is adjusted so that the amount of retained austenite in the inner ring core region 22D is 10% by volume or less.

  In the shot peening process, shot peening is performed on, for example, the outer ring rolling surface 21A and the inner ring rolling surface 22A, which are part of the steel member that has been hardened and hardened in the heat treatment process as described above. Thus, plastic working is performed. As a result, the retained austenite in the rolling surface surface regions 21B and 22B, which is 50% by volume or more and 70% by volume or less in the induction hardening process, is induced by plastic working by shot peening and transformed into martensite. As a result, the amount of retained austenite is reduced to, for example, 25% by volume or more and 45% by volume or less, and compression in a region where the depth from the outer ring rolling surface 21A and the inner ring rolling surface 22A is 0.05 mm or more and 0.1 mm or less. The stress rises to 500 MPa or more.

  As described above, by combining induction hardening as a carburizing and partial quenching and hardening process and plastic working such as shot peening, a region with an extremely large amount of retained austenite is formed immediately below the rolling surface. By plastic working in the vicinity of the running surface, a high compressive stress can be generated in the vicinity of the rolling surface while securing a relatively large amount of retained austenite. As a result, the load applied to the radial needle roller bearing 2 is relatively small, and the self-reinforcing ability of retained austenite cannot be fully utilized as in the first embodiment only by the operation of the radial needle roller bearing 2. However, it is possible to generate a high compressive stress near the rolling surface while securing a relatively large amount of retained austenite as described above. As a result, the rolling fatigue life of the radial needle roller bearing 2 can be improved.

  In the first and second embodiments, the needle roller bearing and the needle roller bearing raceway member of the present invention are described as an example of the thrust needle roller bearing, the radial needle roller bearing, and the raceway ring provided in them. The needle roller bearing and needle roller bearing race member of the present invention are not limited to these. For example, the raceway member for the needle roller bearing may be a shaft or a plate used so that the needle roller rolls on the surface. In other words, the raceway member for the needle roller bearing of the present invention may be a member provided with a rolling surface for rolling the needle roller. Further, the needle roller is manufactured by the same manufacturing method as the needle roller bearing race member of the present invention as in the above-described embodiment, and may have the same configuration, but it is generally out of the scope of the present invention. A typical needle roller may be used. Further, any one of the carburizing step and the carbonitriding step performed in the heat treatment step included in the method for manufacturing the needle roller bearing raceway member and the needle roller bearing of the present invention can be arbitrarily selected. Further, in the needle roller bearing raceway member and needle roller bearing manufacturing method of the present invention, whether or not the partial plastic working step such as shot peening and rolling is performed depends on the needle roller bearing raceway member and To be determined by the usage environment of the needle roller bearing, that is, whether or not it is a usage environment in which the self-strengthening ability of retained austenite can be fully utilized by using the needle roller bearing raceway member and the needle roller bearing. Can do.

  Embodiment 1 of the present invention will be described below. A roller bearing inner ring manufactured by the same manufacturing method as the raceway member for the needle roller bearing of the present invention, and a roller manufactured by a manufacturing method outside the scope of the present invention and having a configuration outside the scope of the present invention. A test was conducted to compare the rolling fatigue life with the bearing inner ring. The test procedure is as follows.

First, a method for producing a test piece (roller bearing inner ring) to be tested will be described. The test specimens of the examples were manufactured by the same method as the method for manufacturing the needle roller bearing race member described in the first and second embodiments. JIS SUJ2 and JIS SCr420 were adopted as the material steel. First, by carrying out turning or the like on a steel bar made of JIS SUJ2 and a steel bar made of JIS SCr420, it has the general shape of a roller bearing inner ring of a cylindrical roller bearing NJ206 (outer diameter φ62 mm, inner diameter φ30 mm, width 16 mm). A steel member was produced. And, as a quench hardening process, carbon steel is hardened by carbonitriding and quenching for steel members (Examples 1A to 1D) made of JIS SUJ2, and steel members (Examples 1E to 1H) made of JIS SCr420. Charcoal quenching was performed. Carbonitriding and quenching was performed by heating the steel member to 850 ° C. in an atmosphere in which 5% NH ₃ was added to RX gas, holding it for 120 minutes, and then immersing it in oil at 100 ° C. On the other hand, carburizing and quenching is performed by heating the steel member to 950 ° C. in a carburizing gas atmosphere containing RX gas, holding it for 480 minutes, lowering the temperature to 850 ° C., and then immersing it in oil at 100 ° C. Carried out.

  Furthermore, the 1st tempering process was implemented by heating the said steel member with respect to the steel member in which the hardening hardening process was implemented at 180 degreeC, and hold | maintaining for 120 minutes. And the partial hardening hardening process which induction-hardens the rolling surface vicinity (area | region of about 1 mm below rolling surface) was implemented with respect to the said steel member by the conditions of frequency 150kHz. . Then, the 2nd tempering process was implemented on the conditions similar to a 1st tempering process. And with respect to one part test piece (Example 1C, 1D, 1G, 1H), the partial plastic working process was implemented by implementing shot peening. Furthermore, the test piece of the Example was completed by performing finishing processes, such as grinding of a rolling surface.

  On the other hand, the test piece of the comparative example was produced by the same method as the test piece of the above example. However, in the test piece of the comparative example, a bright heat treatment (quenching: quenching by immersing in oil at 100 ° C after heating for 50 minutes at 850 ° C, tempering: holding at 120 ° C for 120 minutes) as a quench hardening process The adopted test piece was also produced (Comparative Example 1A). Moreover, the partial hardening hardening process is not implemented with respect to the test piece of a comparative example.

  Next, test conditions will be described. Rollers that were crowned to prevent edge loading were used as test specimens for the roller bearing inner ring as a test piece. Then, the roller and the inner ring are set so that the roller as the counterpart test piece is in contact with the rolling surface of the roller bearing inner ring which is the test piece, the load is 10 kN, the rotation speed is 2000 rotations / minute, and the lubricating oil is a condition of the turbine VG56. The specimen was rotated under. And the time until peeling occurred on the test piece was evaluated as the test piece life.

  Table 1 shows the test pieces and test results in Example 1. In Table 1, the amount of retained austenite and the rolling surface hardness indicate the amount of retained austenite and the hardness on the rolling surface of the test piece. Moreover, in Table 1, the compressive stress has shown the magnitude | size of the compressive stress in the area | region of 0.05 mm under a rolling surface.

  Referring to Table 1, among the test pieces of the examples that were not subjected to shot peening, the amount of retained austenite was 50 to 70% by volume, the rolling surface hardness was 450 to 600 HV, and the compressive stress. Is 290 MPa or more and 460 MPa or less. On the other hand, of the test pieces of the examples, those subjected to shot peening decreased the retained austenite amount to 25 volume% or more and 45 volume% or less, the rolling surface hardness was 730 HV or more and 830 HV or less, and the compressive stress was 750 MPa or more. It has risen to 900 MPa or less. This is presumably because the retained austenite near the rolling surface transformed into martensite due to the influence of plastic working by shot peening. And it turns out that the lifetime of the test piece which performed shot peening tends to become long life compared with the lifetime of the test piece which does not perform shot peening.

  When the life of the test piece of this example is compared with the life of the test piece of the comparative example, the life of the test piece of the example is the same as that of the comparative example in both the test piece subjected to shot peening and the test piece not subjected to shot peening. The life of the specimen is exceeded. From this, it was confirmed that the roller bearing inner ring of the example having the same configuration as the raceway member for the needle roller bearing of the present invention has a longer life than the roller bearing inner ring of the comparative example which is a conventional roller bearing inner ring. The Of the roller bearing inner rings of the examples, those that were not shot peened are in a state where the amount of retained austenite is extremely large (50% by volume or more) in the region near the rolling surface, but during the rolling fatigue life test The increase in rotational runout accompanying plastic deformation and martensite formation of the retained austenite was several μm or less. This is presumably because the region where the amount of retained austenite is extremely large is limited to the region near the rolling surface. Therefore, it is considered that the reduction in dimensional stability due to retained austenite in the raceway member for needle roller bearings of the present invention is within a range that does not cause any problems in practice.

  Embodiment 2 of the present invention will be described below. A roller bearing inner ring manufactured by the same manufacturing method as the raceway member for the needle roller bearing of the present invention, and a roller manufactured by a manufacturing method outside the scope of the present invention and having a configuration outside the scope of the present invention. A test was conducted to compare the rolling fatigue life with the bearing inner ring. The test procedure is as follows.

  The method for producing the test pieces of the example of Example 2 and the comparative example is the same as that of Example 1. The test conditions are basically the same as in Example 1. However, the test condition of Example 1 is that a straight type roller not subjected to crowning is adopted as the mating test piece of the roller bearing inner ring which is a test piece. Is different. Thereby, in the test conditions of Example 2, an edge load is generated on the rolling surface of the test piece.

  Table 2 shows the test pieces and test results in Example 2. Referring to Table 2, it can be seen that the test result of Example 2 is basically the same as the test result of Example 1. However, the difference is that the lifetime is reduced as a whole, and the difference in lifetime between the test piece of the example and the test piece of the comparative example is increased. In Example 2, this is considered to be the effect of adopting a straight type roller as the counterpart test piece. That is, as described above, under the test conditions of Example 2, edge load is generated on the rolling surface of the test piece, so that local rolling fatigue progresses on the rolling surface of the test piece, and the life of the test piece is as a whole. It is thought that it declined. Here, in the test piece of the example having the same configuration as the raceway member for the needle roller bearing of the present invention capable of effectively utilizing the self-reinforcing ability of retained austenite, the edge load of the test piece of the comparative example is larger than that of the test piece of the comparative example. The influence can be reduced. Therefore, it is considered that the life of the test piece of the example did not decrease as much as the life of the test piece of the comparative example, and as a result, the life difference between the test piece of the example and the test piece of the comparative example became large. As described above, according to the raceway member for needle roller bearings of the present invention, a long-life needle roller bearing raceway member is obtained, and the raceway member for needle roller bearings of the present invention is particularly likely to cause an edge load. It is considered to be suitable for a raceway member for a needle roller bearing used under severe conditions.

  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 raceway member for needle roller bearings, the needle roller bearing and the manufacturing method thereof according to the present invention are particularly advantageously applied to the race member for needle roller bearings, needle roller bearings and the production method thereof used in harsh environments. Can be done.

1 is a schematic cross-sectional view showing a configuration of a thrust needle roller bearing as a needle roller bearing provided with a raceway member for needle roller bearings according to Embodiment 1. FIG. FIG. 2 is a schematic partial cross-sectional view of a bearing ring as a needle roller bearing race member provided in the thrust needle roller bearing of FIG. 1. It is a schematic sectional drawing of the needle roller as a rolling element with which the thrust needle roller bearing of FIG. 1 is provided. FIG. 5 is a diagram showing an outline of a method for manufacturing the race, needle roller, and thrust needle roller bearing in the first embodiment. FIG. 5 is a diagram for explaining the details of a heat treatment process for the bearing ring and the needle roller included in the method for manufacturing the bearing ring, the needle roller and the thrust needle roller bearing in the first embodiment. 6 is a schematic cross-sectional view showing a configuration of a radial needle roller bearing as a needle roller bearing provided with a raceway member for needle roller bearings according to Embodiment 2. FIG. It is a schematic fragmentary sectional view of the bearing ring (outer ring) as a raceway member for needle roller bearings with which the radial needle roller bearing of FIG. 6 is equipped. FIG. 7 is a schematic partial cross-sectional view of a bearing ring (inner ring) as a needle member for a needle roller bearing provided in the radial needle roller bearing of FIG. 6. It is a figure which shows the outline of the manufacturing method of the raceway member for needle roller bearings in Embodiment 2, a needle roller, and a radial needle roller bearing. It is a figure for demonstrating the detail of the heat processing process of the raceway member for needle roller bearings and the needle roller included in the manufacturing method of the raceway member for needle roller bearings in Embodiment 2, and a needle roller and a radial needle roller bearing.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Thrust needle roller bearing, 2 Radial needle roller bearing, 11 bearing ring, 11A raceway rolling surface, 11B rolling surface surface area, 11C bearing ring surface layer part, 11D bearing ring core area, 13 needle roller, 13A needle roller rolling Running surface, 13B Rolling surface surface region, 13C Needle roller surface layer portion, 13D Needle roller core region, 14, 24 Cage, 21 Outer ring, 21A Outer ring rolling surface, 21B Rolling surface surface layer region, 21C Outer ring surface layer portion, 21D outer ring core region, 22 inner ring, 22A inner ring rolling surface, 22B rolling surface surface layer region, 22C inner ring surface layer region, 22D inner ring core region, 23 needle roller.

Claims (8)

A method for producing a raceway member for a needle roller bearing that is used to be in contact with a needle roller as a rolling element, and that has a rolling surface for rolling the needle roller,
A steel member preparing step of preparing a steel member made of steel and formed into a schematic shape of the raceway member for the needle roller bearing,
A quench hardening step of quench hardening after performing carburization or carbonitriding on the steel member;
A rolling region as a region including a portion that becomes the rolling surface of the raceway member for the needle roller bearing, which is a partial region of the steel member that has been hardened and hardened in the quench hardening step, is further hardened. A partial quench hardening process in which the amount of retained austenite in the region of the steel member having a depth from the surface to be the rolling surface of 0.3 mm or less is 50% by volume to 70% by volume by hardening. When,
A finishing step of completing the raceway member for the needle roller bearing by performing a finishing process on the steel member in which the rolling region has been hardened and hardened in the partial hardening and hardening step. Manufacturing method of raceway member for needle roller bearing. In the finishing step, in the raceway member for needle roller bearing completed by performing the finishing step, the amount of retained austenite in a region having a depth of 0.3 mm or less from the rolling surface is 50% by volume or more and 70% by volume. % Or less,
The compressive stress in the region where the depth from the rolling surface is 0.05 mm or more and 0.1 mm or less is 250 MPa or more,
The needle roller according to claim 1, wherein the finishing is performed so that the amount of retained austenite in a region having a depth of 1 mm or more from the surface of the raceway member for the needle roller bearing is 10% by volume or less. Manufacturing method of bearing race member.   After the partial quench hardening step and before the finishing step, the portion that becomes the rolling surface that is part of the steel member that has been hardened and hardened in the partial quench hardening step. On the other hand, the manufacturing method of the raceway member for needle roller bearings of Claim 1 further equipped with the partial plastic processing process which implements plastic processing. In the finishing step, in the raceway member for the needle roller bearing completed by performing the finishing step, a compressive stress in a region having a depth from the rolling surface of 0.05 mm to 0.1 mm is 500 MPa or more. ,
The needle roller according to claim 3, wherein the finishing is performed so that the amount of retained austenite in a region where the depth from the surface of the raceway member for the needle roller bearing is 1 mm or more is 10% by volume or less. Manufacturing method of bearing race member.   The method for manufacturing a needle roller bearing race member according to any one of claims 1 to 4, wherein the heating in the partial quenching and curing step is performed by induction heating.   A raceway member for a needle roller bearing manufactured by the method for producing a raceway member for a needle roller bearing according to any one of claims 1 to 5. A raceway member for a needle roller bearing that is arranged and used so as to come into contact with a needle roller as a rolling element, and has a rolling surface for rolling the needle roller,
The amount of retained austenite in the region having a depth of 0.3 mm or less from the rolling surface is 50% by volume or more and 70% by volume or less,
The compressive stress in the region where the depth from the rolling surface is 0.05 mm or more and 0.1 mm or less is 250 MPa or more,
A raceway member for a needle roller bearing, wherein a retained austenite amount in a region having a depth of 1 mm or more from the surface is 10% by volume or less. A track member;
A plurality of needle rollers that are in contact with the track member and disposed on an annular track;
The said raceway member is a needle roller bearing which is a raceway member for needle roller bearings of Claim 6 or 7.

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