JP2005113176A - Method for producing bearing race - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten time needed to a grinding process by suppressing deformation developed before and after heat treatment after grinding small, in a method for producing a bearing race. <P>SOLUTION: After obtaining a ring-like blank having a prescribed width by performing annealing and cutting off to a cold-worked steel tube, cutting, heat treatment, and grinding are performed to the ring-like blank to produce an inner race or an outer race of the roller bearing. At this time, annealing is performed at a temperature not lower than an A<SB>1</SB>transformation point. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an inner ring or an outer ring of a rolling bearing.

Conventionally, an inner ring and an outer ring of a rolling bearing are manufactured, for example, by the following method. First, a rod made of high carbon chromium bearing steel is processed into a tubular shape by hot working or the like to obtain a seamless steel pipe. Next, after spheroidizing annealing is performed on the steel pipe, the dimensions are adjusted by performing cold working (rolling or drawing by a pilga mill).
Next, this steel pipe is annealed for the purpose of removing stress generated by cold working. Next, this steel pipe is cut into a ring-shaped material. Next, this ring-shaped material is cut by a lathe and processed into the shapes of an inner ring and an outer ring. Next, the processed material is subjected to heat treatment such as quenching and tempering. Next, grinding for finishing is performed to adjust the roundness.

And conventionally, as the annealing after the cold working, “strain relief annealing” is performed at a temperature of 680 to 720 ° C. lower than the A ₁ transformation point.
In addition, the following patent documents 1-3 are mentioned as a patent document with which the prior art of the manufacturing method of a bearing raceway is described.
Japanese Patent Publication No.7-37645 JP-A-9-176740 JP 2002-105536 A

However, when a ring-shaped material having a small ratio (t / a) of thickness (t) to outer diameter (a) (for example, 0.06 or less) is used, the annealing after the cold working is performed. When “strain relief annealing” is performed, there is a problem that the deformation is large before and after the heat treatment after cutting, and the grinding process takes time to ensure a predetermined roundness. Further, the black skin generated on the surface by annealing may not be removed in the grinding process, resulting in a defective product.
The present invention provides a ring-shaped material having a predetermined width by annealing and cutting a cold-worked steel pipe, and then performing cutting, heat treatment, and grinding on the ring-shaped material. An object of the method of manufacturing an inner ring or an outer ring of a rolling bearing is to suppress deformation occurring before and after heat treatment after cutting, thereby shortening the time required for the grinding process.

In order to solve the above problems, the present invention obtains a ring-shaped material having a predetermined width by annealing and cutting a cold-worked steel pipe, and then cutting the ring-shaped material, Provided is a method for manufacturing a bearing race, wherein the annealing is performed at a temperature equal to or higher than the A ₁ transformation point (727 ° C.) in a method for manufacturing an inner ring or an outer ring of a rolling bearing by heat treatment and grinding. To do. As the annealing, it is preferable to perform spheroidizing annealing including a process of maintaining the temperature at or above the A ₁ transformation point.

In the method of the present invention, by performing the annealing at A ₁ transformation point or more temperature, the compressive residual stress at the position (near the surface) to be 100μm~150μm inwardly from said ring-like material surface below 100MPa be able to.
Since the residual stress exists in a state where the tensile stress and the compressive stress are balanced in the entire ring-shaped material, if the compressive residual stress on the surface side is small, the tensile stress existing inside is also small to balance this. . And the deformation | transformation before and behind heat processing arises because the residual stress which exists in the ring-shaped raw material after annealing is open | released by the heat processing after cutting. Therefore, the magnitude of deformation before and after the heat treatment depends on the magnitude of compressive residual stress existing in the vicinity of the surface of the ring-shaped material after annealing.

The reason why the compressive residual stress is limited by the value at a position of 100 μm to 150 μm from the surface to the inside is that there is an effect of cutting at a position on the surface side from 100 μm, and cold working at a position inside from 150 μm. This is because the influence of.
The method of the present invention is suitable as a method for producing a bearing ring in which the ratio (t / a) of the thickness (t) to the outer diameter (a) of the ring-shaped material is 0.060 or less.

  According to the present invention, a ring-shaped material having a predetermined width is obtained by annealing and cutting a cold-worked steel pipe, and then the ring-shaped material is subjected to cutting, heat treatment, and grinding. As a result, in the method of manufacturing the inner ring or outer ring of the rolling bearing, the time required for the grinding process can be shortened by suppressing the deformation occurring before and after the heat treatment after cutting, as compared with the conventional method. Can be reduced.

Hereinafter, embodiments of the present invention will be described.
A single row deep groove ball bearing (rolling bearing) having a nominal number 6810 includes an inner ring 1, an outer ring 2, a ball 3 and a cage 4 as shown in FIG. 1. Further, as shown in FIG. 2, the outer diameter 2 of the outer ring 2 of this ball bearing is 65 mm, the inner diameter b is 60.5 mm, and the width c is 7 mm. The thickness t of the outer ring 2 is (65-60.5) /2=2.25 mm, and the ratio (t / a) of the thickness (t) to the outer diameter (a) is 2.25 / 65 = 0.0346≈0.035.
The outer ring 2 was produced by the following method, and the following tests 1 to 3 were performed. The procedure is shown in the flowchart of FIG. In Test 3, the outer diameter a was fixed at 65 mm, and the ratio (t / a) of the outer ring 2 was changed by changing the inner diameter b.

[Test 1]
A seamless steel pipe made of SUJ2 obtained by hot working was prepared, and the steel pipe was annealed (1). This annealing (1) was heated to 800 ° C., held at this temperature for 2 hours, cooled to 740 ° C. in 2 hours, held at this temperature for 2 hours, and then cooled to 650 ° C. at a cooling rate of 5 ° C./h. It was performed by cooling to air after cooling gradually. Next, cold rolling (cold working) using a pilga mill was performed. This process introduces strain into the steel pipe.

Next, in No. 1-1, this steel pipe (a cold-worked steel pipe) was cut to a width corresponding to the width of the outer ring 2, and then "annealing (2)" was performed. This “annealing (2)” was heated to 800 ° C. (temperature above the A ₁ transformation point), held at this temperature for 2 hours, cooled to 740 ° C. in 2 hours, and held at this temperature for 2 hours. It was performed by cooling to 650 ° C. at a cooling rate of 5 ° C./h and then air cooling. This “annealing (2)” corresponds to “spheroidizing annealing including a process of maintaining the temperature at or above the A ₁ transformation point”.

In No. 1-2, the above-described “annealing (2)” was performed on the cold-worked steel pipe, and then cut into a width corresponding to the width of the outer ring 2.
In No. 1-3, after performing the “annealing (3)” on the cold-worked steel pipe, it was cut into a width corresponding to the width of the outer ring 2. This annealing (3) was performed by heating to 700 ° C. and holding at this temperature for 2 hours, followed by slow cooling to 600 ° C. at a cooling rate of 150 ° C./h, followed by air cooling. This annealing (3) corresponds to “strain relief annealing at a temperature lower than the A ₁ transformation point”.

In this way, 50 ring-shaped materials No. 1-1 to 1-3 were produced. Next, each ring-shaped material was turned into an outer ring shape (cut with a lathe) to obtain an outer ring precursor (an outer ring before heat treatment). The roundness of the outer ring precursor at the position of the raceway groove 21 was measured. An average value was calculated from 50 measurement results. The average value is shown in Table 1 below.
Next, the outer ring precursors of No. 1-1 to 1-3 were quenched at 840 ° C. and tempered at 180 ° C. Next, the roundness at the position of the raceway groove 21 of the outer ring precursor after the heat treatment was measured. An average value was calculated from 50 measurement results. The average value and the minimum and maximum values of the roundness measurement values are shown in Table 1 below. Also, the difference in roundness before and after heat treatment (“average value of roundness after heat treatment” − “average value of roundness before heat treatment”) was calculated. The calculated values are also shown in Table 1. Next, the outer ring was completed by grinding the outer ring precursor.

As can be seen from this table, No. 1-1 and No. 1 were subjected to “annealing (2)” corresponding to “spheroidizing annealing including a process of maintaining the temperature above the A ₁ transformation point” after cold working. -2, the change in roundness before and after the heat treatment was as small as 20 μm and 30 μm. In contrast, in No. 1-3 in which “annealing (3)” corresponding to “strain relief annealing” at a temperature below the A ₁ transformation point was performed, the change in roundness before and after heat treatment was as large as 100. It was. The minimum value of roundness was the same at 10 μm, but the maximum value of No. 1-3 was large at 380 μm, whereas No. 1-1 and No. 1-2 were small at 150 μm and 170 μm. .

[Test 2]
In contrast to “cold-worked steel pipes” obtained in the same manner as in Test 1, in Nos. 2-1 to 2-4, the above-mentioned “annealing (2)” was changed to Nos. 2-5 to 2-6. Then, "annealing (4)" was performed, and in Nos. 2-7 to 2-9, the above-mentioned "annealing (3)" was performed. This “annealing (4)” is heated to 800 ° C. (temperature above the A ₁ transformation point), held at this temperature for 2 hours, cooled to 650 ° C. at a cooling rate of 30 ° C./h, and then air-cooled. I went there.

  Next, the steel pipe after each annealing is cut into a width corresponding to the width of the outer ring 2 to obtain a ring-shaped material, and these are turned into an outer ring shape, whereby No. 2-1 to 2-9 outer ring precursors are obtained. Got the body. Next, the roundness (roundness before heat treatment) of these outer ring precursors at the position of the raceway groove 21 was measured. Next, the residual stress of the raceway groove 21 of these outer ring precursors was measured at a position of 100 μm to 150 μm inward from the surface of the raceway groove 21. The measured values are shown in Table 2 below. The residual stress of “−” indicates “compressive residual stress”.

  Next, the outer ring precursors No. 2-1 to 2-9 were quenched at 840 ° C. and tempered at 180 ° C. Next, the roundness at the position of the raceway groove 21 of the outer ring precursor after the heat treatment was measured. Then, the difference in roundness before and after heat treatment (“roundness after heat treatment” − “roundness before heat treatment”) was calculated. The calculated values are also shown in Table 2 below. Next, the outer ring was completed by grinding the outer ring precursor.

As can be seen from this table, Nos. 2-1 to No. 2 were subjected to “annealing (2)” corresponding to “spheroidizing annealing including a process of maintaining the temperature above the A ₁ transformation point” after cold working. -4 and No. 2-5 to No. 2-6 where “annealing (4)” corresponding to “annealing at a temperature equal to or higher than the A ₁ transformation point” was performed, the change in roundness before and after the heat treatment The amount was 10 to 90 μm, and the compressive residual stress was 5 to 100 MPa. On the other hand, in Nos. 2-7 to 2-9 where “annealing (3)” corresponding to “strain relief annealing at a temperature lower than the A ₁ transformation point” was performed, the roundness before and after the heat treatment was The amount of change was 160 to 320 μm, and the compressive residual stress was 120 to 200 MPa.

As can be seen from the results, by performing the annealing after cold working at A ₁ transformation point or higher, the compressive residual stress at the location of the outer ring precursors can below 100 MPa, along with this, before and after heat treatment The amount of change in roundness at 10 can be reduced to 10 to 90 μm. In addition, from the comparison between No. 2-1 to No. 2-4 and No. 2-5 to 2-6, as the annealing after cold working, “including the process of maintaining the temperature above the A ₁ transformation point” It can be seen that by performing “spheroidizing annealing”, the amount of change in roundness before and after the heat treatment can be particularly reduced to 10 to 65 μm.

[Test 3]
In contrast to the “cold-worked steel pipe” obtained in the same manner as in Test 1, in Nos. 3-1 to 3-4, the above-mentioned “annealing (2)” was changed to No. 3-5 to 3-11. Then, the above-mentioned “annealing (3)” was performed. Next, the steel pipe after each annealing is cut into a width corresponding to the width of the outer ring 2 to obtain a ring-shaped material, and these are turned into the shape of each outer ring, whereby No. 3-1 to 11-11 outer rings are obtained. A precursor was obtained. Next, the roundness (roundness before heat treatment) of these outer ring precursors at the position of the raceway groove 21 was measured.
Next, these outer ring precursors were quenched at 840 ° C. and tempered at 180 ° C. Next, the roundness of each outer ring precursor after the heat treatment at the position of the raceway groove 21 was measured. The difference in roundness before and after heat treatment (“roundness after heat treatment” − “roundness before heat treatment”) was calculated. The calculated values are also shown in Table 3 below. Next, the outer ring was completed by grinding the outer ring precursor.

As can be seen from this table, the ratio (t / a) of the thickness (t) to the outer diameter (a) of the ring-shaped material is 0.060 or less. The amount of change in roundness of No. 3-1 to which “annealing (2)” corresponding to “spheroidizing annealing including a process of holding at a temperature equal to or higher than the A ₁ transformation point” was performed after cold working was performed. No. 3-4, 40 to 66 μm, and values obtained in No. 3-5 to 3-8 where “annealing (3)” corresponding to “strain relief annealing at a temperature lower than the A ₁ transformation point” was performed. (120 to 260 μm). In comparison between those having the same ratio (t / a), the difference in the amount of change was 80 to 200 μm.

Nos. 3-9 to 3-11 having a ratio (t / a) exceeding 0.060 perform “annealing (3)” corresponding to “strain relief annealing at a temperature lower than the A ₁ transformation point”. However, the “change amount of roundness before and after heat treatment” is 55 to 90 μm, the same “annealing (3)” is performed, and the ratio (t / a) is 0.060 or less. It was smaller than the value of 3-5 to 3-8.
Thus, when the ratio (t / a) exceeds 0.060, the change in roundness due to heat treatment can be achieved even after performing “relief annealing at a temperature below the A ₁ transformation point” after cold working. Although the amount is less than 100 μm, when the ratio (t / a) is 0.060 or less, the amount of change is as large as 120 μm or more. Therefore, it is particularly effective when the ratio (t / a) is 0.060 or less to perform “spheroidizing annealing including a process of maintaining the temperature at the A ₁ transformation point or higher” after cold working. I understand.

It is sectional drawing which shows an example of a single row deep groove ball bearing (rolling bearing). It is sectional drawing which shows the outer ring | wheel of the bearing of FIG. It is a flowchart which shows the preparation method of the outer ring | wheel performed in embodiment, and the procedure of Tests 1-3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 2 Outer ring 21 Outer ring raceway groove 3 Ball 4 Cage

Claims (4)

A ring-shaped material having a predetermined width is obtained by annealing and cutting a cold-worked steel pipe, and then the ring-shaped material is subjected to cutting, heat treatment, and grinding to obtain a rolling bearing. In a method of manufacturing an inner ring or an outer ring,
Method of manufacturing a bearing ring, characterized in that performing the annealing at A ₁ transformation point or higher. As the annealing method of the bearing ring according to claim 1, wherein performing spheroidizing annealing comprising the step of holding at a temperature equal to or higher than the A ₁ transformation point.   The method for manufacturing a bearing race according to claim 1, wherein the compressive residual stress at a position of 100 μm to 150 μm inward from the surface of the ring-shaped material is set to 100 MPa or less by the annealing.   The method for manufacturing a bearing race according to claim 1, wherein the ratio (t / a) of the thickness (t) to the outer diameter (a) of the ring-shaped material is 0.060 or less.

Images