JP2003148490A - Method for manufacturing thrust type ball bearing race - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a thrust type ball bearing race having sufficient reliability and further improved anti-rolling fatigue life to severer usage environments caused by light weight and low fuel consumption performance of an automobile. SOLUTION: In manufacturing the thrust type ball bearing race provided with ball bearing grooves, a bearing race main body is molded by forging, setting steel material to have lengthwise metal flow in a perpendicular direction to a thrust load direction. After conducting finishing then, carburization or carbonitriding is conducted. Anti-rolling fatigue life of the thrust type ball bearing race is thus further improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thrust type ball bearing race.

[0002] A lot of developments have been made for a long time with respect to the improvement of rolling fatigue strength of bearing steels. Examples thereof include a method of reducing non-metallic inclusions mixed in the bearing steel as much as possible, a method of giving a compressive residual stress to the surface, and further controlling a residual austenite amount.

Further, in order to improve the rolling fatigue life of bearing steel, one of the main techniques is to reduce the oxygen content in the steel to make it a clean steel (for example, Japanese Unexamined Patent Publication No. Hei 7 (1999) -83945).
No. 109541 uses a steel for bearings whose Mn content is restricted to 0.20% or less as a base material, is melted by an electron beam melting method, and non-metallic inclusions having a diameter of 15 μm or more float from the molten metal. A method for manufacturing ultra-clean bearing steel is disclosed in which the diameter of the non-metallic inclusions in the steel is 15 μm or less while ensuring the time for separation. ).

[0004] In the technique for producing such ultra-clean steel, the oxygen content in the steel is reduced to reduce the oxide non-metallic inclusions which are the starting points of fatigue fracture. , A method of melting steel and performing vacuum degassing,
With the introduction of ladle refining, continuous casting and multiple melting technology,
Oxygen content in steel can be significantly reduced.

Furthermore, by controlling the total amount and size of oxide-based non-metallic inclusions, removing large inclusions, and controlling the composition and morphology to make them ultrafine and evenly distributed, rolling Fatigue life has been significantly extended (for example, NS
K Technical Journal No. 65
2 1992).

As a measure for further improving the rolling fatigue life,
In order to positively utilize the compressive residual stress and retained austenite on the surface, the conventional SUJ steel, which has been established in JIS as bearing steel, has been used for case hardening, which has been established in JIS as carburizing or carbonitriding steel. Some steel types have been changed to steel, and measures have been taken to cope with a wide range of environments, from a clean lubrication environment to a dirty lubrication environment in which foreign matter such as abrasion powder is mixed. In combination with clean steel, the rolling fatigue life is further improved.

However, reliability of the bearing life is a more important issue due to the severer use environment due to the recent weight reduction and fuel consumption reduction of automobiles, and it is difficult to say that it is sufficient at present. It's a reality.

In the bearing developed by combining the best material and heat treatment developed in the past, as a result of the thrust type life test under a clean lubrication condition, the L10 life is 1 × 10 8 at a surface pressure of 5.0 GPa. However, under actual conditions of use, unbalanced loads and uneven contact due to torque fluctuations occur, and 5.
There is a problem that surface peeling occurs under the condition of more than 0 GPa.

As a conventional method for manufacturing a thrust type ball bearing race, there is, for example, one shown in FIG.

That is, a round bar-shaped steel material 11 having a composition of case hardening steel and having a longitudinal metal flow F as shown in FIG. 5 is used, and the longitudinal direction of the round bar-shaped steel material 11 is sliced. After obtaining the bearing race body (specimen A before quenching) 12, this bearing race body 12
The ball bearing groove was roughened by machining, carburized or carbonitrided and quenched, and then polished to obtain a thrust type ball bearing race (test piece A after quenching).

In the thrust type ball bearing race manufactured by such a method, the surface fatigue strength is improved and the surface fatigue strength is prevented from lowering due to the inclusion of foreign matter such as abrasion powder generated during operation in the lubricating oil. Therefore, during the carburizing or carbonitriding treatment, the amount of retained austenite in the surface portion of the carburizing or carbonitriding layer is adjusted to 20 to 40% by volume (for example, JP-A-8-372).
0, JP-A-8-4774).

[0012]

In the conventional method of manufacturing a thrust type ball bearing race, as shown in FIG. 5, the round bar-shaped steel material 11 is cut in a direction perpendicular to the metal flow F in the longitudinal direction. Therefore, in the used state, as shown in FIG. 6, the direction of the load P acting on the ball bearing race 13 is parallel to the direction of the metal flow F.

Further, in this type of thrust ball bearing race, rolling fatigue is required in order to have sufficient reliability even under severe conditions of use environment due to weight reduction of automobiles, low fuel consumption and the like. There was a problem to be able to extend the life further.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems, and more effectively utilizes the characteristics inherently possessed by steel materials, thereby improving the rolling fatigue life obtained in the past. It is an object of the present invention to provide a method for manufacturing an ultra-high strength thrust type bearing race that can be further improved.

[0015]

According to a method of manufacturing a thrust type ball bearing race according to the present invention, when a thrust type ball bearing race having a ball bearing groove is manufactured, a metal flow in a longitudinal direction of a steel material is a thrust load. It is characterized in that the bearing race body is formed by forging in a direction perpendicular to the direction, followed by finishing and then carburizing or carbonitriding quenching.

FIG. 1 shows an embodiment of a thrust type ball bearing race manufactured by the method for manufacturing a thrust type ball bearing race according to the present invention.
In this thrust type ball bearing race 1, the direction of the thrust load P is perpendicular to the direction of the metal flow F of the steel material, and the bearing race body is formed by forging, and carburizing is performed after finishing. Or, it is carbonitrided and quenched.

In the method of manufacturing a thrust type ball bearing race according to the present invention, a case hardening steel can be used as a steel material, for example, JIS G 4051.
S09CK, S15C, which are carbon steel materials established in
K, S20CK and SNCM22, which is a nickel-chromium-molybdenum steel steel material established in JIS G4103.
0, SNCM415, SNCM420, SNCM61
6, SNCM815 and SCr415 and SCr420 which are chrome steel materials established in JIS G 4104.
And SCM415, SCM418, SCM, which are chrome and molybdenum steel materials established in JIS G 4105.
420, SCM421, SCM822, JIS G
4106, manganese steel steel material, SMn42
No. 0, or manganese-chromium steel steel material SMnC420, which is also defined in JIS G 4106, can be used, but the material is not limited to these, and a material with an appropriate alloy component added can also be used. You can

[0018]

According to the method of manufacturing the thrust type ball bearing race according to the present invention, the characteristics originally possessed by the steel material are more effectively utilized to further improve the rolling fatigue life and wear resistance. Thus, a superior thrust type ball bearing race can be manufactured.

[0019]

EXAMPLES Example 1 A steel material corresponding to JIS SCM420H steel, in which C: 0.23% by weight, Si: 0.22% by weight, Mn: 0.80% by weight, P: 0. 010% by weight,
S: 0.015% by weight, Ni: 0.11% by weight, Cr:
0.98% by weight, Mo: 0.15% by weight, the balance being a low S, low P component consisting essentially of Fe and having an oxygen content of 9.0.
Clean steel adjusted to a very low ppm was used.

Then, in the step shown in FIG. 2A, a round bar-shaped steel material 2 having a diameter of 46 mm is cut into a length of 37 mm in a direction perpendicular to the longitudinal direction (that is, the direction of the metal flow F), and then, In the step shown in FIG. 2B, the electric furnace is used to heat to 1000 ° C.
In the step shown in (C) of, the diameter is 80 mm and the depth is 12
10 mm by the first shot with a hammer in a state where the round bar-shaped steel material 2 is placed in the center of a circular metal mold 3 with the longitudinal direction (that is, the direction of the metal flow F) being horizontal.
The oxide is removed together with the crushing, and (D-1) in FIG.
In the step shown in (D-2), 2-3 with a hammer
Specimen C before quenching was obtained by filling the die 3 with a disk shape having a diameter of 80 mm and a thickness of 12 mm.

By forging in this way, a pre-quenching specimen C having a metal flow F that is more densified than the pre-quenching specimen B cut in the direction parallel to the metal flow F as shown in FIG. Obtainable.

For comparison with the pre-quenched specimen C and the pre-quenched specimen B having the disk shape, a round bar-shaped steel material having a diameter of 80 mm is longitudinally (metal flow F) for comparison.
Also, a pre-quenching specimen A having a disk shape, which was cut to a thickness of 12 mm in a direction perpendicular to the () direction), was also prepared.

Next, each of the pre-quenching specimens A,
The surfaces of B and C were finished to Rmax25S, carburized and diffused (920 ° C. × 8 Hr) in the steps shown in FIG. 2 (E) and FIG. 5, and then quenched in oil at 100 ° C., 170 After tempering was carried out at a temperature of 90 ° C. for 90 minutes, specimens A, B and C were obtained after each quenching.

Test pieces A, B, C after completion of each quenching
There is almost no difference in the properties of the conventional product and the forged product, effective hardened layer depth: 1.00 mm, surface hardness: Hv7
00, core hardness: Hv345-363, amount of retained austenite on the surface: about 18%, and residual stress is ± 0 MPa at the outermost surface and the maximum value of compression at a depth of about 0.2 mm − Almost 0 from 400 MPa to 1.5 mm depth
The curve returned to MPa. Moreover, the former austenite grain size was Gc10 in JIS G 0551.

Next, after quenching, the test surfaces of the specimens A, B, and C were superfinished to Rmax 0.03a, and the surface peeling life was compared by a thrust type rolling fatigue tester under the conditions shown in the following table. .

[0026]

[Table 1]

Specimen C of Example of the present invention produced by forging
Shows that the direction of the load P and the direction of the metal flow F are at right angles as shown in FIG. 1, and the specimen A in which the round bar steel material is cut has the direction of the load P and the direction of the metal flow F as shown in FIG. It becomes parallel as shown in.

FIG. 4 shows the result of measuring the Weibull distribution of the surface peeling life by the thrust type rolling fatigue tester. Figure 4
As is clearer, in the comparison between the specimens A and B after quenching, the specimen B has a peel life of about 25% improved.

On the other hand, the specimen C after quenching has a forging ratio of 3.8.
However, since the density of the metal flow F is high, the life of the product of the present invention is about 100 as compared with the conventional product.
It was confirmed that it improved by%.

In manufacturing the thrust type ball bearing race, the ball bearing groove R is also formed by forging, carburized or carbonitrided, and then polished to obtain a peeling life almost equal to the thrust test result. It was

When manufacturing a thrust type ball bearing race having a ball bearing groove as in the first embodiment, the bearing race main body is oriented so that the metal flow in the longitudinal direction of the steel material is perpendicular to the thrust load direction. By forming by forging, it becomes possible to manufacture the thrust type ball bearing race in which the rolling fatigue life is further improved by making more effective use of the inherent properties of the steel material.

Also, the bearing race main body is formed by forging with the metal flow in the longitudinal direction of the steel material oriented at right angles to the thrust load direction, and then subjected to carburizing or carbonitriding quenching after finishing. As a result, rolling fatigue strength and wear resistance are further improved. More desirably, the carburizing treatment is performed at 920 ° C. for 8 hours,
As a quenching treatment condition, 17 after casting in oil at 100 ° C
By performing tempering at 0 ° C. for 90 minutes, rolling fatigue strength is further improved, and it becomes possible to manufacture a thrust type ball bearing race having excellent wear resistance.

Example 2 In this Example 2, by combining the metal flow densification of Example 1 and the method of forging and quenching after carburizing, the thrust type having a further excellent rolling fatigue life. The case where a ball bearing race is manufactured is shown.

First, in the step shown in FIG.
A round bar-shaped steel material 2 having a diameter of 46 mm is longitudinally (ie,
After being cut to a length of 37 mm in a direction perpendicular to the direction of the metal flow F), in the step shown in FIG. 3B, carburization and diffusion treatment (920 ° C. × 12 Hr) are performed, and then about 10
Quenching was performed at 0 ° C. to obtain a round rod-shaped forging material having an effective hardened layer depth of 1.2 mm.

Next, in the step (C) of FIG. 3, after the carburized round rod-shaped forging material is heated to 1000 ° C. by high-frequency heating, a diameter of 80 is obtained in the step shown in FIG.
mm with a depth of 12 mm, a circular rod 3 is placed in the center so that the longitudinal direction of the round bar-shaped steel material 2 (that is, the direction of the metal flow F) is in a horizontal direction.
It is crushed by 10 mm by hitting, and further (E-1) and (E- in FIG.
In the process shown in 2), the diameter is 8 by forging with a hammer.
After the pre-quenching specimen D was obtained by filling the die 3 with a disk shape of 0 mm and a thickness of 12 mm, the residual heat was used in the step shown in FIG.
After quenching in oil at 0 ° C and tempering at 170 ° C for 90 minutes, a sample D was obtained after quenching.

In the step (C), heating was performed in a nitrogen gas atmosphere for the purpose of preventing oxidation during high frequency heating. Also,
The forging end temperature is about 850 ° C as measured by a radiation thermometer.
Therefore, the quenching in the step (F) utilized the heat.

After that, the test surface of the test piece D after quenching was reduced to 0.
Finished with 3mm polishing and finally Rmax0.0 with super finishing
A rolling fatigue test was carried out in the same manner as in Example 1 with 3a.

As a result of investigating various characteristics of the specimen D after quenching, surface hardness: Hv800, effective hardened layer depth: 0.6 m
m, core hardness: Hv 400 to 420, former austenite crystal grain size: Gc10 or less (2 to 12 μm) according to JIS G 0551, amount of surface retained austenite: about 2
2%, and the residual stress is (compression) -80 at the outermost surface.
The distribution was 0 MPa and 0.2 mm at a depth of almost 0.

As shown in FIG. 4, the result of the rolling fatigue test shows that the forged product of Example 2 (specimen D after quenching) is the same as the forged product of example 1 (specimen C after quenching). It was confirmed that the amount was further improved by about 30%.

In this case, the factors for improving the rolling contact fatigue life include the densification of metal flow by forging, the refinement of former austenite crystal grains, the maximum shearing due to the increase of internal defects such as dislocations and twins accompanying forging and quenching. It is considered that there is an increase in resistance to structural changes in the stress generation depth region.

After carburizing or carbonitriding the steel material as in Example 2 above, the residual heat from the carburizing or carbonitriding is not used or reheated, and the metal flow in the longitudinal direction of the steel material is performed. The bearing race body is formed by forging in a direction that is perpendicular to the thrust load direction.
Then, by performing a quenching process after performing a finishing process, it is possible to further increase the density of the metal flow and enhance the rolling fatigue strength and rolling fatigue life. More preferably, the carburizing condition is 920 ° C. for 12 hours. The rolling fatigue strength can be further enhanced by carrying out and reheating at 1000 ° C. in nitrogen as a reheating condition, and as a quenching processing condition by casting in oil at 80 ° C. and then tempering at 170 ° C. for 90 minutes. At the same time, it becomes possible to manufacture a thrust type ball bearing race having a further excellent rolling fatigue life.

The thrust type ball bearing manufactured by the method of manufacturing the thrust type ball bearing race described in Examples 1 and 2 has high rolling fatigue strength, and very excellent rolling fatigue life and wear resistance. For example, the vehicle has sufficient reliability even in a severe operating environment due to, for example, weight reduction of an automobile and reduction of fuel consumption.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a thrust type ball bearing race according to one embodiment of the present invention together with the direction of its metal flow.

FIG. 2 is an explanatory view showing the manufacturing process of the thrust type ball bearing race according to the first embodiment of the present invention, divided into FIGS.

FIG. 3 is an explanatory view showing the manufacturing process of the thrust type ball bearing race in Embodiment 2 of the present invention separately in FIGS.

FIG. 4 is a graph showing the results of examining the Weibull distribution of surface peeling life by a thrust type rolling fatigue tester.

FIG. 5 is an explanatory diagram showing a relationship between a longitudinal direction (direction of metal flow) of a round bar-shaped steel material and a cutting direction of test pieces A and B.

6 is an explanatory diagram showing a relationship between a metal flow direction and a load direction in a ball bearing race corresponding to the test piece A shown in FIG.

[Explanation of symbols]

1 Thrust type ball bearing race 2 Round bar steel material 3 circular mold

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI theme code (reference) C23C 8/22 C23C 8/22 8/32 8/32 (72) Inventor Shinro Kino Kanagawa-ku, Yokohama-shi, Kanagawa No. 2 Takaramachi Nissan Motor Co., Ltd. F-term (reference) 3J101 AA02 AA53 BA51 DA02 DA03 EA04 FA31 FA35 GA01 4E087 AA02 BA02 BA17 CA11 CA17 CB01 DB04 DB18 DB24 GA06 HA42 HA82 4K028 AA01 AA03 CA04 CA04 CA10 CA23 CA04 DA02 DA06 DB01 DD03

Claims (5)

[Claims] 1. When manufacturing a thrust type ball bearing race having a ball bearing groove, the bearing race body is formed by forging so that the metal flow in the longitudinal direction of the steel material becomes a direction perpendicular to the thrust load direction, Next, a method of manufacturing a thrust type ball bearing race, characterized by performing carburizing or carbonitriding quenching treatment after finishing. 2. The carburizing treatment condition is that it is carried out at 920 ° C. for 8 hours, and the quenching treatment condition is that after being immersed in oil at 100 ° C., tempered at 170 ° C. for 90 minutes. A method of manufacturing a thrust type ball bearing race according to claim 1. 3. When manufacturing a thrust type ball bearing race having a ball bearing groove, after carburizing or carbonitriding a steel material, the residual heat at the time of carburizing or carbonitriding is not used or reheated. Then, the bearing race main body is formed by forging with the metal flow in the longitudinal direction of the steel material oriented at a right angle to the thrust load direction, and then finish processing is performed, followed by quenching treatment. Ball bearing race manufacturing method. 4. The carburizing condition is that it is carried out at 920 ° C. for 12 hours, the reheating condition is that it is carried out at 1000 ° C. in nitrogen, and the quenching process condition is that it is cast in oil at 80 ° C. After that, tempering is performed at 170 ° C. for 90 minutes, and the method of manufacturing the thrust type ball bearing race according to claim 1. 5. A thrust type ball bearing race manufactured by the method for manufacturing a thrust type ball bearing race according to any one of claims 1 to 4.