JPH032328A - Manufacture of race for rolling bearing - Google Patents

Abstract

PURPOSE:To manufacture the race for a rolling bearing having excellent rolling life by subjecting ring stock obtd. by turning a martensitic stainless steel to area reducing treatment by rolling at least to form a track part and subjecting the race to heat treatment. CONSTITUTION:The inside of a through hole 11 of a receiving ring 10 is charged with ring stock (r) manufactured from a martensitic stainless steel and a roll 20 is inserted into a through hole (r) (about 1) of the ring stock (r). Next, the roll 20 is rotated in the state where the ring stock (r) is fitted into a groove 21 of the roll 20 and the roll 20 is pressed against the inner wall face 12 of the receiving ring 10 as shown by the arrow. In this way, a projected line 22 of the roll 20 is brought into contact with the inner wall face (r)2 of the ring stock (r) to regulate the width by the groove 21 of the roll 20; the ring stock is rolled by the roll 20 and the receiving ring 10 to obtain an outer race R formed with a track part R3 corresponding to the shape of the projected line 22 on the inner wall face. The outer race R at least formed with the track part R3 is subjected to heat treatment to progress the entering of primary carbide into solid solution to a matrix and to refine the primary carbide, by which the outer race R having prolonged service life can be obtd.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method of manufacturing a race for a rolling bearing, such as an outer ring or an inner ring of a rolling bearing, and more specifically, relates to a method for manufacturing a race for a rolling bearing, such as an outer ring or an inner ring of a rolling bearing. The present invention relates to a method of manufacturing a race for a rolling bearing that has an excellent lifespan.

<Prior art and problems to be solved by the invention> Conventionally, races for rolling bearings such as the outer ring and inner ring are generally manufactured by turning a raw metal to form a predetermined shape, followed by heat treatment and polishing. has been done.

However, martensitic stainless steel such as 5US4400, which has excellent corrosion resistance and is mainly used in rolling bearings used in corrosive atmospheres, is produced using the above conventional manufacturing method, which results in large primary carbides remaining in the structure. Corrosion resistance cannot be fully demonstrated, and there is a risk that the rolling life will be insufficient.

Therefore, it is conceivable to increase the heat treatment temperature to a high temperature to promote solid solution of the secondary carbide into the matrix. However, in this method, as mentioned above, secondary carbides are unevenly distributed in the matrix as giant particles, so heat treatment may cause local composition changes and martensite becomes brittle, or crystal grains may become As a result, the wear resistance deteriorates and the rolling life is shortened.

This invention was made in view of the above circumstances, and aims to provide a method for manufacturing a long-life rolling bearing race that can withstand use particularly in corrosive atmospheres. .

Means for Solving the Problems> In order to solve the above problems, the method for manufacturing a race for a rolling bearing of the present invention involves rolling a ring material,
It is characterized in that at least the raceway portion is formed and then heat treated.

Effect> According to the method for manufacturing a race for a rolling bearing of the present invention having the above-mentioned configuration, the huge primary carbide in the material ring is destroyed and fragmented by the surface reduction effect caused by the rolling process. -The surface area of subcarbides increases. Therefore, by heat treatment at a normal temperature where there is no risk of crystal grain growth, solid solution of the primary carbide in the matrix is promoted and the primary carbide is refined. In addition, dislocations introduced into the matrix in the material ring during rolling work work to promote the diffusion of chromium and carbon, so heat treatment at normal temperatures promotes the solid solution of carbides into the matrix. , - secondary carbides are refined. Furthermore, since the secondary carbides are uniformly dispersed in the matrix by the rolling process, there is no possibility of local compositional changes occurring due to solid solution during heat treatment. <Example> The present invention will be described below with reference to drawings showing an example of manufacturing an outer ring as a race for a rolling bearing.

As shown in FIG. 1, in this embodiment, a material ring manufactured by turning from martensitic stainless steel is subjected to area reduction processing by rolling processing, and a raceway portion R3 is formed on the inner wall surface R2 of the through hole R1. Rolling processing step 1 of forming the formed outer ring R (see Figure 3) into the shape; Turning finishing step 2 of chamfering the formed outer ring R; Heat treatment step 3 of heat treating the outer ring under normal heating conditions; Polishing. The process is comprised of process 4 and raceway superfinishing process 5.

In the rolling process 1, the receiver shown in Fig. 2 is a ring I.
O and roll 20 are used.

The receiver ring IO is freely rotatably supported by a support device (not shown), and is provided with a through hole 11 for accommodating the material ring r. Moreover, this through hole 11 is
The inner diameter thereof is set to a dimension corresponding to the outer diameter dimension of the outer ring R to be manufactured.

The roll 20 is inserted into the through hole r1 of the material ring r housed in the through hole 11, and rotates while pressing the material ring r against the inner wall surface 12 of the ring 10.
It is for rolling a raw ring R, and is provided with an annular groove 21 on the outer peripheral surface of a cylindrical main body having a depth and width corresponding to the thickness and width of the outer ring R to be manufactured.

Further, the bottom surface of this groove 21 is provided with a through hole I?of the outer ring R? A protrusion 22 formed on the inner wall surface R2 of I and having a cross-sectional shape corresponding to the cross-sectional shape of the raceway portion R3 for supporting the rolling elements.
is formed.

In the above-mentioned bridge, the outer ring R is formed by rolling using the ring 10 and the roll 2o as follows.

First, as shown in FIG. 4(a), the receiver accommodates a material ring r having an outer diameter smaller than the inner diameter of the through hole 11 in the through hole 11 of the ring 1o. Further, the roll 20 is inserted into the through hole "1" of this material ring r.

The roll 20 may be inserted into the through hole rl at any stage before or after the material ring r is accommodated in the through hole 11.

Next, with the material ring "fitted into the groove 21 of the roll 20, while rotating the roll 20, the roll 2o is pressed toward the inner wall surface 12 of the ring 1o, as shown by the arrow in the figure. do.

As a result of this pressing, as shown in FIG. The material ring r is rolled by the receiver ring 1o.

As shown in the same figure (C1), a track portion R3 corresponding to the shape of the protrusion 22 is formed on the inner wall surface R2, and
An outer ring R is formed, the thickness and width of which are defined by the groove 21, and the outer diameter of the receiver is defined by the inner diameter of the ring IO.

In addition, as for the above-mentioned rolling processing, cold rolling processing performed at room temperature is mainly used, but so-called warm rolling processing, which is performed by heating the material ring to a temperature below the recrystallization temperature of the material, can also be adopted. .

The outer ring R formed in the above manner is extracted from the ring 10, subjected to a turning finish such as chamfering, and then heat treated under normal heat treatment conditions. After the surface polishing step 4 and the raceway superfinishing step 5, the outer ring R of the rolling bearing is completed.

In addition, when forming the outer ring by the above-mentioned rolling process, if the bearing has an inner diameter larger than the specified outer diameter of the outer ring, use a ring to roll the material ring to almost the specified outer diameter, and then roll the material ring to approximately the specified outer diameter. It is also possible to adopt a method in which the outer ring is press-fitted into a die provided with a through hole having an inner diameter and passed through the through hole of the die to adjust the outer diameter of the outer ring to a predetermined outer diameter.

According to the manufacturing method of this embodiment having the above configuration, the rolling process destroys the huge primary carbide in the material ring r, introduces dislocations into the matrix, and evenly spreads the carbide into the matrix. Therefore, by heat treatment at a normal temperature where there is no risk of crystal grain growth, it becomes easier for the secondary carbide to form a solid solution in the matrix, making it possible to refine the secondary carbide. There is no risk of local compositional changes occurring due to melting. therefore,
It is possible to manufacture a long-life outer ring R that has sufficient corrosion resistance and wear resistance, and can withstand use particularly in a corrosive atmosphere.

On the other hand, in order to manufacture the inner ring of a rolling bearing by the method of manufacturing a race for a rolling bearing of the present invention, rolling processing is performed using a rolling device for forming the inner ring shown in FIG. Through the same process as the production of
All you need to do is process the material ring.

The rolling device shown in the figure has an outer diameter corresponding to the inner diameter of the through hole of the inner ring to be formed, and is supported so as to be freely rotatable and movable in the horizontal direction in the figure. A core material 30 inserted therein, and a pair of rolls 31 and 32 for applying pressure to the material ring r inserted through the core material 30 from left and right to roll the material ring.
During the rolling process using both rolls 31 and 32, in order to prevent the material ring r from escaping in the vertical direction where it is not pressed by the rolls 31 and 32, it is pressed against the material ring r from above and below, as shown by the white arrows in the figure. A pair of auxiliary rings 33 and 34 are provided.

In addition, in the above-mentioned both rolls 31 and 32, one roll 31 is fixed and the other roll 32 is pressed in the direction of the fixed roll 31 as shown by the black arrow in the figure, so that the core material 30 is It is configured to be pressed against the inserted material ring from the left and right. Also, as shown in the figure (b+), on the abutting surface of each roll 31 to 34 against the material ring, An annular fk 35 having a depth and width corresponding to the thickness and width of the inner ring is formed, and the bottom surface of this fk 35 has a raceway portion formed on the outer wall surface of the inner ring for supporting the rolling elements. A protrusion 36 having a cross-sectional shape corresponding to the cross-sectional shape is formed.

In addition, in the forming of the outer ring and inner ring as races of rolling bearings explained above, parts other than the raceway were also rolled, but if the raceway that the rolling elements directly contact was reduced in area, Since it is possible to obtain a rolling bearing with a long life, the rolling process may be performed on at least the raceway portion.

Specific Examples> The present invention will be explained below based on specific examples and comparative examples.

(Specific example) The receiver shown in Fig. 2 is made of SUS 440C (martensitic stainless steel) using a ring lO and a roll 20.
A race for a rolling bearing corresponding to the outer ring for a ball bearing with a bearing number #6206 is molded from a ring made of a
A rolling bearing race corresponding to the inner ring of the ball bearing with the above-mentioned number #'6206 was formed using the rolling device shown in FIG. The area reduction rate in the thickness direction was 50%.

Next, after turning and finishing both of the rolling bearing races, 1
After going through a heat treatment process consisting of heating at 050℃ for 40 minutes, rapid cooling, cooling at -70℃ for 2 hours, and annealing at 180℃ for 2 hours, a polishing process, and a raceway superfinishing process, the outer ring and inner ring for ball bearings are manufactured. was manufactured.

Then, a ball bearing was manufactured by combining the above-mentioned ball bearing outer ring and inner ring with steel balls made of high carbon ROM bearing steel (SUJ2).

(Comparative example) From a material ring made of SO8440C (martensitic stainless steel), the bearing number #6206 was made by turning.
A pair of rolling bearing races corresponding to the outer ring and inner ring for a ball bearing were formed, and the outer ring and inner ring for a ball bearing were then manufactured through the same steps as in the above specific example.

Then, a ball bearing was manufactured by combining the above ball bearing outer ring and inner ring with steel balls made of high carbon chromium bearing steel (SUJ2).

(Durability Test) The ball bearings produced in the above specific examples and comparative examples were rotated under the following conditions and their lifespans were measured. Cumulative damage probability (%
) and the lifespan (time) is shown in Figure 6.

・Test conditions: Temperature...room temperature Humidity degree...50% Rotation speed - 220 Or, p, tn.

Radial load: 918 kg Lubricant: Grease (Albania No. 2) From the results in the figure, the ball bearing made in the specific example (solid line in the figure) is different from the ball bearing made in the comparative example (broken line in the figure). In comparison, about 1.
It was found to have five times the lifespan.

(Salt spray test) The inner ring of the ball bearing produced in the above specific example and comparative example was
Three pieces of each were left under the following salt water spray conditions, and the rusted area ratio of the raceway surface of each inner ring was measured after 1 hour, 2 hours, 4 hours, 8 hours, and 24 hours. .

The following table shows the average values of the rusting area ratios for three inner rings in each of the specific examples and comparative examples. (
(Margins below)・Test conditions: Temperature: 35±1℃ Salt water concentration: 5±1% (pH7±1) Spray amount: 1 to 2
ml/h Table From the results shown in the table above, it was found that the specific examples had better corrosion resistance than the comparative examples.

(Structure Observation) In the specific examples and comparative examples, the metal structure of the rolling bearing race before heat treatment was observed using a microscope.

As a result, as shown in Figure 7 (al(b) (both micrographs at 400x magnification)), huge primary carbides of about 15 μm were observed in the comparative example rolling bearing race (Figure 7 )reference). On the other hand, in the rolling bearing race of the specific example, the primary carbide is about 4 μm at most.
Only two were observed, and the others were uniform fine carbides (see Figure 7 (ω)).

<Effects of the Invention> The method for manufacturing a race for a rolling bearing according to the present invention is configured as described above, and by forming a material ring made of martensitic stainless steel into a predetermined shape by rolling processing, Because the primary carbide contained in the material is finely divided and evenly dispersed in the matrix, it has sufficient corrosion and wear resistance through subsequent heat treatment, and is particularly suitable for use in corrosive atmospheres. It becomes possible to manufacture a race for rolling bearings that is durable and has a long life.

[Brief explanation of the drawing]

Fig. 1 is a process diagram illustrating the steps of an embodiment of manufacturing an outer ring of a rolling bearing by the method of manufacturing a race for a rolling bearing according to the present invention, and Fig. 2 is a process diagram used for the rolling process of each process of the above embodiment. FIG. 3 is a perspective view showing an example of the device; FIG. 3 is a partially cutaway perspective view showing an example of an outer ring as a race for a rolling bearing manufactured using the device; FIG.
~(C) is a cross-sectional view showing the forming process of the outer ring using the above-mentioned device, and FIG. ) is a side view showing the contact surface of the roll to the material ring in the above device, FIG. 6 is a graph showing the relationship between the cumulative failure probability and the life of the rolling bearing in specific examples and comparative examples, and FIG. 7 (al is (Photograph substituted for a drawing showing the metal structure of the race for a rolling bearing manufactured in a specific example, in Figure 7)
is a photograph substituted for a drawing showing the metal structure of a race for a rolling bearing manufactured in a comparative example. 1... Rolling process, 3... Heat treatment process, I
O...The bearing is a ring, 20...Roll, r...Material ring, R...Race (outer ring) for rolling bearings.

Claims (1)

[Claims] 1. A method for manufacturing a race for a rolling bearing made of martensitic stainless steel, which comprises rolling a ring material to form at least a raceway portion, and then heat treating the ring.