JP2006089795A - Rolling bearing race ring and its producing method, and rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing race ring having uniform hardness and its producing method, and a rolling bearing having the rolling bearing race ring with which warping and deformation at the heat treatment can be restrained. <P>SOLUTION: The producing method of the rolling bearing race ring, is as follows, by which after heating the race ring 1 in a thrust needle roller bearing while pressing with dies 12a, 12b, lower bainite is generated by cooling with the dies 12a, 12b as a cooling medium to carry out an isothermal transformation to this race ring. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing bearing ring, a manufacturing method thereof, and a rolling bearing, and more particularly to a thin rolling bearing bearing ring, a manufacturing method thereof, and a rolling bearing having the thin rolling bearing bearing ring.

  Conventionally, a thrust needle (needle) roller bearing raceway ring and a shell-type radial needle roller bearing raceway ring are low carbon SPCC (JIS: cold rolled steel plate) material, SCM415 material (JIS: chrome molybdenum steel steel material). A carburizing treatment for a short time has been used to harden the required hardness portion of the surface layer. In addition, a medium to high carbon steel such as SK5 material (JIS: carbon tool steel) is hardened by whole heating. All of these used carburizing and batch heating furnaces for heat treatment.

  On the other hand, thin-walled products are also quenched by high-frequency heating, and there are techniques such as the following Patent Documents 1 to 4 for quenching thin-walled products and uneven-thickness parts by high-frequency heating. However, these are all cooled with air or gas at the time of quenching, and the strain is suppressed by controlling the cooling rate, or the difference in quenching speed between the thick part and the thin part is eliminated, thereby suppressing deformation.

In addition, there is a quenching technique (for example, Patent Document 5) while giving restraint to the tubular member, but quenching uses a solution, and there is no technique using a mold as both a restraint and a quenching medium. There was no technology related to isothermal transformation technology.
Japanese Patent Laid-Open No. 6-179920 JP-A-9-302416 JP 2001-214213 A JP 2003-55713 A JP 7-216456 A

  A conventional low-carbon SPCC material or SCM415 material that has been carburized for a short time and hardened the required hardness of the surface layer is excellent in workability of the material, but since carburizing is used for heat treatment, it is suitable for offline heat treatment. Thus, there is a problem that the life and strength are not stabilized due to grain boundary oxidation during carburizing, warpage during quenching, deformation, and the like.

  In addition, medium to high carbon steel such as SK5 material has a problem that the material is high in hardness and difficult to work. In the case of whole heating and quenching in an atmospheric furnace, deformation due to cooling unevenness occurs as in carburizing. For these all-quenched products, cooling is performed slowly and uniformly (for example, cooling by blowing an inert gas), but it is difficult to eliminate the deformation and reduce warpage. Needed to be tempered to re-warp.

  On the other hand, even with high-frequency heating products, since air or water is used as the quenching medium during the induction heating-water quenching process, deformation at quenching is inevitable no matter how slowly it is cooled, especially when water is used. It was necessary to replace the liquid due to deterioration or wear.

  Quenching with a mold can be quenched without causing warpage or deformation by interlocking with induction heating, but it can be cooled with oil or water to prevent temperature rise of the mold, or after quenching with oil, the product can be cooled at a specified temperature. A technique of pulling up and restraining with a mold is common. Moreover, when press hardening with a metal mold | die, tempering is required.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a rolling bearing bearing ring having uniform hardness, a rolling bearing bearing ring having a uniform hardness, and a rolling bearing having the rolling bearing bearing ring.

  The method of manufacturing a rolling bearing race of the present invention is characterized in that after heating the bearing ring of the rolling bearing, the die is cooled as a cooling medium while being pressed with a die, and is subjected to isothermal transformation to produce lower bainite. It is what.

  In the method for manufacturing the rolling bearing race, the rolling bearing race is preferably heated by induction heating.

  In the above-described method for manufacturing a rolling bearing race, the rolling bearing race is preferably a medium carbon steel containing 0.4% by mass or more of carbon.

  The rolling bearing race of the present invention is manufactured by any of the methods described above and has a lower bainite.

  The rolling bearing of the present invention includes the above-described rolling bearing race and a rolling element.

  In the above rolling bearing, preferably, the rolling bearing is a thrust needle roller bearing.

  In the manufacturing method of a rolling bearing bearing ring, the inventors of the present application deformed by pressing the rolling bearing bearing ring with a mold, cooling the mold as a cooling medium, and isothermally transforming to produce lower bainite. It has been found that long-life bearing race rings with no torsion, uniform hardness distribution and excellent toughness can be manufactured.

  As described above, according to the method for manufacturing a rolling bearing race of the present invention, since the transformation is caused by maintaining a constant temperature, the material of the rolling bearing race is a bainite structure, and the quenching distortion is less than that of the martensite structure. Even if tempering is not performed, there is an advantage that it has toughness and can suppress aged dimensional change. Moreover, since it is not necessary to perform tempering, the rolling bearing race can be heat-treated with a piece-by-piece. Further, since it is not necessary to perform tempering, normal quenching / tempering can be completed in one step, and the production process can be omitted.

  Further, since warpage and deformation can be suppressed, a thin bearing race can be manufactured with high accuracy. In addition, because constant temperature transformation is performed using a mold as a cooling medium, uniform heat treatment is possible rather than quenching with blast or oil, and stable quality is ensured by keeping the press pressure and mold temperature constant. be able to. Also, since no water or oil is used, the working environment is clean and there are no environmental pollution problems such as waste liquid.

  Moreover, quality control is easy to perform because of quenching one by one. Further, the hardness can be increased by forming the lower bainite.

  In the manufacturing method of the above-described rolling bearing race, by rolling the rolling bearing race by induction heating, an inexpensive high-frequency material (machine structural steel) can be applied and the life is stable. Moreover, since it heats by induction heating, it can heat in a short time and cannot produce surface abnormal layers, such as grain boundary oxidation and decarburization. Moreover, since it heats by induction heating, a quenching condition and a coil shape can be changed and a non-isothermal transformation part can be made partially, Therefore It can apply also to the product which needs a bending process after heat processing.

  In the manufacturing method of the above-described rolling bearing race, sufficient hardness can be obtained when the rolling bearing race is a medium carbon steel containing 0.4 mass% or more of carbon.

  By using the rolling bearing raceway described above, a rolling bearing having a stable life and strength, for example, a thrust needle roller bearing can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 and 2 are schematic cross-sectional views showing a method of manufacturing a rolling bearing race in one embodiment of the present invention in the order of steps. First, steel having a predetermined composition, for example, medium carbon steel containing 0.4% by mass or more of carbon is prepared as a raw material. The steel is subjected to processing such as cutting to form a bearing race.

  With reference to FIG. 1, the bearing race 1 is mounted on a rotary table 10 and is induction-heated by, for example, a heating coil 11. At this time, the bearing race 1 is rotated by the rotary table 10.

Referring to FIG. 2, the bearing race 1 heated to a predetermined temperature is sandwiched between cooling molds 12a and 12b controlled to a predetermined temperature, and a weight 13 is placed on the cooling mold 12b. As a result, the bearing race 1 is cooled by using the cooling molds 12a and 12b as a cooling medium while being pressed by the cooling molds 12a and 12b at a pressing pressure of, for example, 2.94 N / cm ² or more, and is subjected to constant temperature transformation and hardening. . That is, the cooling molds 12 a and 12 b serve as a cooling medium in the constant temperature transformation of the bearing race 1 while restraining the bearing race 1.

  By the above method, it is possible to produce a long-life bearing race 1 having a uniform hardness distribution, no defects such as oxidation and decarburization on the surface, and very little warpage and deformation. The bearing race 1 has a lower bainite.

  In the bearing race 1 manufactured in this way, the flatness is low and the hardness is stable as compared with the conventional bearing race manufactured using air or gas as a quenching medium.

  In order to use the cooling molds 12a and 12b as a cooling medium, there is a method in which the heat capacities of the cooling molds 12a and 12b are considerably increased as compared with the bearing race 1. For example, in order to suppress the temperature rise of the cooling molds 12 a and 12 b to 5 ° C. or less while the temperature of the bearing race 1 is lowered by 900 ° C., the heat capacity of the cooling molds 12 a and 12 b is 180 ° of the heat capacity of the bearing race 1. It is necessary to make it more than double. Since the bearing race 1 is sandwiched between the upper and lower cooling dies 12 a and 12 b, the heat capacity of one of the upper and lower cooling dies 12 a and 12 b needs to be 90 times or more that of the bearing race 1. Therefore, if the bearing race 1 and the cooling dies 12a and 12b are made of the same material (for example, steel) and have the same specific heat, the mass of either the upper or lower cooling dies 12a or 12b is the bearing race. It is necessary to make it 90 times or more the mass of the wheel 1.

  For example, a thrust needle roller bearing as shown in FIG. 3 can be manufactured using the bearing race 1 manufactured by the above method. This thrust needle roller bearing is capable of rolling a pair of bearing races 1, a plurality of rolling elements (needle rollers) 2 disposed between the pair of bearing races 1, and a plurality of rolling elements 2. And a retainer 3 for retaining.

  Further, for example, a shell-type radial needle roller bearing as shown in FIG. 4 can be manufactured using the bearing race 1 manufactured by the method as described above. This shell-type radial needle roller bearing has a cylindrical outer ring 1 that is a bearing race 1 and a roller 4 with a cage disposed on the inner peripheral side of the outer ring 1. The roller 4 with a cage has a plurality of rolling elements (needle rollers) 2 and a cage 3 for holding the plurality of rolling elements 2 in a rollable manner. In addition, although the collar parts 6 and 7 are provided in the both ends of the outer ring | wheel 1, either one or both of these collar parts 6 and 7 do not need to be provided. Further, as shown in FIG. 5, a plurality of (for example, two) rollers 4 with cages may be arranged on the inner peripheral side of one outer ring 1.

  Since the bearing race 1 shown in FIG. 4 or 5 is a cylindrical outer ring 1, the cooling mold used when quenching the outer ring 1 has a shape different from the cooling molds 12a and 12b of FIG. It needs to be shaped.

  Examples of the present invention will be described below.

  Medium carbon steel S53C was used as a material. A thrust needle roller bearing race (NTN product name: AS1112) having an outer diameter of 60 mm, an outer diameter of 85 mm, and a thickness of 1 mm was manufactured from this material by turning.

  Using a high-frequency induction heating device (80 kHz), a predetermined current was passed through the induction coil close to the one-sided surface while rotating the raceway to induce induction heating (FIG. 1). In this case, the whole was slowly heated so as to have a uniform temperature (about 900 ° C.). After that, the race ring was set in an iron upper and lower press mold having a heat capacity considerably larger than that of the race ring, and immediately pressed with a predetermined pressure by the press, and the race ring was hardened by isothermal transformation by die cooling by the press (Fig. 2). Various changes were made in the mold temperature during curing by isothermal transformation and the restraint time (holding time) by the mold, and the relationship with hardness and microstructure after isothermal transformation was investigated.

  Table 1 shows the relationship between the mold temperature and the restraint time depending on the mold, the warp deformation, the hardness after the isothermal transformation, and the microstructure.

  Table 1 also shows the warpage deformation, hardness and microstructure after isothermal transformation of a sample quenched with water after induction heating, a sample subjected to blast quenching after overall heating, and a sample cooled with air after induction heating. The relationship is also shown.

From the results in Table 1, when the press pressure is 2.94 N / cm ² as in the present invention example, the mold temperature is 250 ° C. or higher and 320 ° C. or lower, and the restraint time (holding time) by the mold is 30 seconds or longer. It can be seen that by making it 5 minutes or less, isothermal transformation occurs and a structure having lower bainite is obtained. Moreover, in the structure | tissue which has the lower bainite of the example of this invention, it turns out that curvature deformation becomes 19 micrometers or less and it becomes Vickers hardness HV685 or more. In some examples of the present invention, a structure similar to that of tempered martensite observed when tempering was observed even though tempering was not performed.

  On the other hand, in the sample of the comparative example, the lower bainite was not observed in the structure, it became a quenched martensite that required tempering, warpage deformation increased, and a Vickers hardness of HV685 or higher could not be obtained.

  Table 3 shows the results of life evaluation of these bearing races under the conditions shown in Table 2.

  Here, the raceway is partly or entirely transformed at a constant temperature, and therefore tempering is not performed. Among the samples of the comparative examples, those martensitic transformed were tempered at 150 ° C. for 120 minutes. The test is a test under lean lubrication conditions.

  From the results in Table 3, it can be seen that the bearing rings manufactured by this method have a life equal to or longer than that of the sample of the comparative example in which ordinary martensite quenching is performed using a die press as a quenching medium. In addition, the sample of the comparative example that was water-quenched after normal high-frequency heating had a precision that the deformation could not be greatly tested. Moreover, the life of the comparative sample subjected to blast quenching was shortened, and the comparative sample subjected to air cooling was not hardened even though it was a thin member.

  Table 4 shows the aging change of each raceway ring after being held at 120 ° C. × 1500 hours.

  From the results of Table 4, it can be seen that the example of the present invention has less aging change than the comparative example. This is because the structure having the quenched martensite is unstable, so that the dimensional change due to temperature rise is large. However, in the isothermal transformation product of the present invention, the structure is stable and the dimensional change due to temperature rise is small. From this, it can be seen that the sample of the example of the present invention is stable in size without tempering.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. 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 rolling bearing bearing ring, the manufacturing method thereof, and the rolling bearing of the present invention are advantageously applied to a thin rolling bearing bearing ring, a manufacturing method thereof, and a rolling bearing having the thin rolling bearing bearing ring.

It is a schematic sectional drawing which shows the process of heating a bearing race in the manufacturing method of the rolling bearing race in one embodiment of this invention. It is a schematic sectional drawing which shows the process of cooling and isothermally transforming a bearing race in the manufacturing method of the rolling bearing race in one embodiment of the present invention. It is a schematic sectional drawing which shows the structure of the thrust needle roller bearing using the rolling bearing bearing ring in one embodiment of this invention. It is a schematic sectional drawing which shows the structure of the shell type radial needle roller bearing using the rolling bearing bearing ring in one embodiment of this invention. It is a schematic sectional drawing which shows the structure of the shell type radial needle roller bearing by which the roller with a some holder | retainer is arrange | positioned in an outer ring | wheel.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Rolling bearing raceway, 2 Rolling body, 3 Cage, 4 Roller with cage, 6,7 collar part, 10 rotary table, 11 Heating coil, 12a, 12b Cooling die, 13 Weight.

Claims (6)

  A method for manufacturing a rolling bearing bearing ring, comprising: heating a bearing ring of a rolling bearing, then cooling the mold as a cooling medium while pressing with a mold and isothermally transforming to generate a lower bainite.   2. The method of manufacturing a rolling bearing race according to claim 1, wherein the heating of the rolling bearing race is performed by induction heating.   The method of manufacturing a rolling bearing race according to claim 1 or 2, wherein the rolling bearing race is a medium carbon steel containing 0.4 mass% or more of carbon.   A rolling bearing race which is manufactured by the method according to claim 1 and has a lower bainite.   A rolling bearing comprising the rolling bearing bearing ring according to claim 4 and a rolling element.   The rolling bearing according to claim 5, wherein the rolling bearing is a thrust needle roller bearing.

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