JPH1037964A - Thrust type ball bearing race and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the rolling fatigue life of a ball bearing race by having sufficient reliability even against the severity of a service environment due to the tendency of the lighter weight and lower fuel consumption of an automobile. SOLUTION: In the case of manufacturing a thrust type ball bearing race having a ball bearing groove, a bearing race body 1 is formed through plastic processing together with the ball bearing groove so that the longitudinal metal flow F of steel raw material may have a direction perpendicular to the direction of thrust load. Since the direction of the thrust load P is perpendicular to the direction of the metal flow F of the steel raw material, and moreover the bearing race body 1 is formed through plastic processing together with the ball bearing groove, the rolling fatigue life can be lengthened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thrust type ball bearing race and a method of manufacturing the same.

[0002] With respect to the improvement of rolling fatigue strength of bearing steel, many developments have been made since ancient times. As an example,
There are a method of reducing non-metallic inclusions mixed in bearing steel as much as possible, a method of imparting compressive residual stress to the surface, and a method of controlling the amount of retained austenite.

[0003] One of the main technologies for improving the rolling fatigue life of bearing steel is to reduce the oxygen content in the steel to produce clean steel (see, for example, Japanese Unexamined Patent Publication No.
In -109541, a non-metallic inclusion having a Mn content of not more than 0.20% is used as a base material, is melted by an electron beam melting method, and has a diameter of 15 μm or more from the molten metal. There is disclosed a method for producing ultra-clean bearing steel in which the time for separation is ensured to reduce the diameter of nonmetallic inclusions in the steel to 15 μm or less. ).

[0004] In such a technique for making ultra-clean steel, the oxide content in the steel is reduced by reducing the oxygen content in the steel to reduce the amount of oxide-based nonmetallic inclusions that cause fatigue fracture. , A method of melting steel and performing vacuum degassing,
Ladle refining, continuous casting and the introduction of multiple melting technology
The oxygen content in steel can be greatly reduced.

[0005] Furthermore, by controlling the total amount and size of oxide-based non-metallic inclusions, removing large inclusions, controlling the composition and morphology, making them ultrafine and uniformly distributed, The 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 residual compressive stress and residual austenite on the surface, the conventional SUJ steel specified in JIS as bearing steel is replaced with the case hardening specified in JIS as carburizing or carbonitriding steel. Some steel grades have been changed to steel, and measures have been taken to cover a wide range of environments, from clean lubrication environments to dirty lubrication environments in which foreign substances such as abrasion powder are mixed. Rolling fatigue life is further improved in combination with the use of clean steel.

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

[0008] In a bearing developed using a combination of the most excellent materials and heat treatment developed conventionally, a thrust type life test under clean lubrication conditions shows that the L10 life is 1 × 10 ⁸ at a surface pressure of 5.0 GPa. . However, uneven load and one-sided contact occur due to torque fluctuation under actual use conditions.
Under the condition exceeding 0 GPa, there is a problem that surface peeling occurs.

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

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

The thrust type ball bearing race manufactured by such a method has an improved surface fatigue strength and prevents a decrease in the surface fatigue strength due to foreign substances such as abrasion powder generated during operation being mixed into the lubricating oil. Therefore, during carburizing or carbonitriding, the amount of retained austenite on the surface of the carburized or carbonitrided layer has been adjusted to 20 to 40% by volume (for example, see 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 use state, the direction of the load P acting on the ball bearing race 13 is parallel to the direction of the metal flow F as shown in FIG.

In this type of thrust type ball bearing race, the rolling contact fatigue is required in order to have sufficient reliability against severe use environment due to weight reduction and low fuel consumption of the automobile. It was an issue to be able to further extend the life.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and makes use of the inherent characteristics of steel materials more effectively to reduce the conventional rolling fatigue life. It is an object of the present invention to provide an ultra-high strength thrust type bearing race which can be further improved.

[0015]

A thrust type ball bearing race according to the present invention is a thrust type ball bearing race having a bearing groove, wherein the thrust load direction is a steel material. It is characterized in that the bearing race body is formed by plastic working together with the ball bearing groove in a direction perpendicular to the flow.

Further, in the embodiment of the thrust type ball bearing race according to the present invention, as described in claim 2, carburizing or carbonitriding and quenching can be performed.

According to a third aspect of the present invention, there is provided a method for manufacturing a thrust type ball bearing race, wherein a thrust type ball bearing race having a ball bearing groove is manufactured in a longitudinal direction of a steel material. The bearing race body is formed by plastic working together with the ball bearing groove in such a direction that the metal flow is perpendicular to the thrust load direction.

In the embodiment of the method for manufacturing a thrust type ball bearing race according to the present invention, the metal flow in the longitudinal direction of the steel material is perpendicular to the thrust load direction. The bearing race body may be oriented and formed by plastic working together with the ball bearing groove, and may be subjected to carburizing or carbonitriding and quenching after performing appropriate finishing as necessary. As described, after the steel material is carburized or carbonitrided, the residual heat during carburizing or carbonitriding is not used or reheated, and the metal flow in the longitudinal direction of the steel material is changed in the thrust load direction. The bearing race body is formed by plastic working with the ball bearing groove in the direction perpendicular to Processing can be made to perform a hardening processing after performing.

Then, as described in claim 6,
It is more desirable that the metal flow be further densified when forming by plastic working.

FIG. 1 shows an embodiment of a thrust type ball bearing race according to the present invention. The thrust type ball bearing race 1 has a 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 plastic working together with the ball bearing grooves.

In the thrust type ball bearing race and the method of manufacturing the same according to the present invention, a case hardening steel can be used as a steel material, for example, JIS G4.
S09CK, S1 which are carbon steel materials enacted in 051
5CK, S20CK and SNC which are nickel-chromium-molybdenum steels specified in JIS G 4103
M220, SNCM415, SNCM420, SNCM
Chromium steels SCr415 and SCr42 specified in 616, SNCM815 and JIS G 4104
0 and SCM415, SCM418, SC, which are chromium-molybdenum steels specified in JIS G 4105.
M420, SCM421, SCM822, JIS G
SMn4, a manganese steel material specified in 4106
20 or SMnC420, which is a manganese-chromium steel material also specified in JIS G 4106, but is not limited to these, and may be a material to which an appropriate alloy component is added. Can be.

[0022]

According to the thrust type ball bearing race of the present invention, in the thrust type ball bearing race having a bearing groove, the thrust load direction is perpendicular to the metal flow of the steel material, and Since the bearing race body is formed by plastic working together with the ball bearing groove, it is possible to make more effective use of the characteristics that the steel material originally possesses, especially to make effective use of the metal flow. It is possible to further improve the rolling fatigue life as compared with the conventional thrust type ball bearing race which is made of the same material. To provide a long-lasting thrust ball bearing race with sufficient reliability even under severe conditions It results in remarkably excellent effect that it is possible.

And, as described in claim 2,
By performing carburizing or carbonitriding and quenching, the rolling fatigue strength can be further improved and a thrust-type ball bearing race with more excellent wear resistance can be obtained. The effect is brought.

According to the method of manufacturing a thrust type ball bearing race according to the present invention, when manufacturing a thrust type ball bearing race having a ball bearing groove, the longitudinal metal flow of the steel material is perpendicular to the thrust load direction. The bearing race body is formed by plastic working together with the ball bearing groove in the orientation as described above, so the thrust type that further improves the rolling fatigue life by making more effective use of the inherent properties of steel materials The significant advantage is that ball bearing races can be manufactured.

And, as described in claim 4,
The bearing race body is formed by plastic working together with the ball bearing grooves so that the metal flow in the longitudinal direction of the steel material is perpendicular to the thrust load direction, and after appropriate finishing, carburizing or carbonitriding and quenching is performed. By doing so, there is a great effect that it is possible to manufacture a thrust type ball bearing race with further improved rolling fatigue strength and more excellent wear resistance.

Further, as described in claim 5, after the steel material is subjected to carburizing or carbonitriding treatment, the residual heat of the carburizing or carbonitriding treatment is not used or reheated,
By forming the bearing race body together with the ball bearing grooves by plastic working with the metal flow in the longitudinal direction of the steel material perpendicular to the thrust load direction, performing appropriate finishing, and then performing quenching treatment By performing plastic working after carburizing or carbonitriding, a remarkably excellent effect is obtained in that a thrust type ball bearing race having more excellent rolling fatigue life can be manufactured.

Further, as described in claim 6, the metal flow can be made denser by forming the metal flow denser when forming by plastic working. Even if the same material as that of the related art is used, a remarkably excellent effect that a thrust type ball bearing race with further improved rolling fatigue life can be manufactured by effectively utilizing the metal flow is provided.

[0028]

EXAMPLE 1 A steel material corresponding to JIS SCM420H steel was used. 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 substantially low Fe and low S components composed of Fe, and having an oxygen content of 9.0.
Clean steel adjusted to an extremely low amount of ppm was used.

Then, in the step shown in FIG. 2A, the 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 (ie, the direction of the metal flow F). In the step shown in FIG. 2B, heating is performed to 1000 ° C. using an electric furnace,
In the step shown in (C) of FIG.
In a state where the longitudinal direction of the round bar-shaped steel material 2 (that is, the direction of the metal flow F) is placed sideways in the center of a circular mold 3 having a diameter of 10 mm, the first hit by a hammer is performed to 10 mm.
At the same time as crushing, oxides were removed, and (D-1) of FIG.
In the step shown in (D-2), 2-3
A sample C before quenching was obtained by filling the mold 3 with a disk having a diameter of 80 mm and a thickness of 12 mm.

By forging (plastic working) in this way,
As shown in FIG. 5, it is possible to obtain a pre-quenched specimen C having a more densified metal flow F than a pre-quenched specimen B cut in a direction parallel to the metal flow F.

For comparison, the disk-shaped specimen C before quenching and the specimen B before quenching were each made of a rod-shaped steel material having a diameter of 80 mm for comparison in the longitudinal direction (Metal Flow F).
The specimen A before quenching having a disc shape cut to a thickness of 12 mm in a direction perpendicular to the direction (1) was also produced.

Next, each of the specimens A before quenching was
The surfaces of B and C are finished to Rmax25S, and in the steps shown in FIG. 2 (E) and FIG. 5, carburized and diffused (920 ° C. × 8 hours), and then quenched in oil at 100 ° C. Specimens A, B and C were obtained after tempering at 90 ° C. × 90 min and quenching, respectively.

Specimens A, B, C after each quenching
There is almost no difference between the conventional product and the forged product, and the effective hardened layer depth: 1.00 mm, surface hardness: Hv7
00, core hardness: Hv 345 to 363, amount of retained austenite on the surface: about 18%, and residual stress: ± 0 MPa at the outermost surface portion, maximum compression value at a depth of approximately 0.2 mm− Almost 0 from 400 MPa to 1.5 mm depth
The curve returned to MPa. The prior austenite crystal grain size was Gc10 according to JIS G 0551.

Next, after quenching, the test surfaces of the specimens A, B, and C were super-finished to an Rmax of 0.03a, and the peeling life of the surfaces was compared with a thrust rolling fatigue tester under the conditions shown in the following table. .

[0035]

[Table 1]

Specimen C of the present invention manufactured by forging
In FIG. 6, the direction of the load P and the direction of the metal flow F are perpendicular to each other as shown in FIG. Are parallel as shown in FIG.

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

On the other hand, the specimen C after quenching had 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 times longer than that of the conventional product.
% Improvement.

In the production of a thrust type ball bearing race, the ball bearing groove R is also formed by forging, carburized or carbonitrided, and then polished to obtain a peel life almost equivalent to the result of the thrust test. Was.

Example 2 In Example 2, the metal flow of Example 1 was densified and the method of forging and quenching after carburizing was combined to form a thrust mold having a more excellent rolling fatigue life. The case where a ball bearing race is manufactured is shown.

First, in the step shown in FIG.
The round bar-shaped steel material 2 having a diameter of 46 mm is placed in the longitudinal direction (that is,
After cutting to a length of 37 mm in a direction perpendicular to the direction of the metal flow F), after carburizing and diffusion treatment (920 ° C. × 12 hours) in the step shown in FIG.
It was quenched at 0 ° C. to obtain a round bar-shaped forged material having an effective hardened layer depth of 1.2 mm.

Next, in the step (C) of FIG. 3, the round bar-shaped forged material after carburization is heated to 1000 ° C. by high-frequency heating, and then, in the step shown in FIG.
1 mm by a hammer in a state where the longitudinal direction of the round bar-shaped steel material 2 (that is, the direction of the metal flow F) is placed sideways in the center of the circular mold 3 having a depth of 12 mm and a depth of 12 mm.
10 mm by smashing, and (E-1), (E-
In the process shown in 2), forging with a hammer has a diameter of 8
After obtaining a specimen D before quenching by filling the mold 3 with a disk shape having a thickness of 0 mm and a thickness of 12 mm, in the step shown in FIG.
After quenching in oil at 170 ° C. and tempering at 170 ° C. for 90 minutes, a specimen D was obtained after quenching.

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

Thereafter, the test surface of the specimen D after quenching was set at 0.
Finish with 3mm polishing, and finally Rmax0.0 with super finish
The rolling fatigue test was performed in the same manner as in Example 1 except that the rolling fatigue test was performed as in Example 1.

After the quenching, the characteristics of the specimen D were examined. The results were as follows: surface hardness: Hv800, effective hardened layer depth: 0.6 m
m, core hardness: Hv 400 to 420, old austenite crystal grain size: Gc 10 or less (2 to 12 μm) according to JIS G 0551, residual surface austenite amount: about 2
2%, and the residual stress is (compression) -80 at the outermost surface.
The distribution was almost zero at 0 MPa and 0.2 mm depth.

As shown in FIG. 4, the results of the rolling fatigue test show that the forged product of Example 2 (specimen D after quenching) was replaced with the forged product of Example 1 (specimen C after quenching). It was found that the efficiency was further improved by about 30%.

Factors for improving the rolling fatigue life in this case are as follows: increase in metal flow density by forging, refinement of old austenite crystal grains, dislocations due to forging quenching, and maximum shear due to increase in internal defects such as twins. It was considered that there was an increase in resistance to structural change in the stress generation depth region.

[Brief description of the drawings]

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

FIG. 2 is an explanatory view showing a manufacturing process of a thrust type ball bearing race in Embodiment 1 of the present invention, divided into FIGS.

FIG. 3 is an explanatory diagram showing a manufacturing process of a thrust type ball bearing race in Embodiment 2 of the present invention, divided into FIGS.

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

FIG. 5 is an explanatory diagram showing a relationship between a longitudinal direction (a direction of a 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 the relationship between the direction of metal flow and the direction of load 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-shaped steel material 3 Circular mold

Claims (6)

[Claims] In a thrust type ball bearing race having a bearing groove, a thrust load direction is perpendicular to a metal flow of a steel material, and a bearing race body is formed by plastic working together with a ball bearing groove. A thrust type ball bearing race characterized by being made. 2. The thrust ball bearing race according to claim 1, wherein a carburizing or carbonitriding and quenching treatment is performed. 3. When manufacturing a thrust type ball bearing race having a ball bearing groove, the bearing race body is plastically worked together with the ball bearing groove so that the metal flow in the longitudinal direction of the steel material is perpendicular to the thrust load direction. A method for producing a thrust type ball bearing race, characterized by being formed by: 4. A method of forming a bearing race body together with a ball bearing groove by plastic working with a direction in which a metal flow in a longitudinal direction of a steel material is perpendicular to a thrust load direction, and after appropriate finishing, carburizing or carbonitriding. The method for producing a thrust ball bearing race according to claim 3, wherein a quenching treatment is performed. 5. After subjecting a steel material to carburizing or carbonitriding treatment, the steel material is reheated without using residual heat during the carburizing or carbonitriding treatment, and the metal flow in the longitudinal direction of the steel material is perpendicular to the thrust load direction. 4. The method of manufacturing a thrust ball bearing race according to claim 3, wherein the bearing race body is formed by plastic working together with the ball bearing groove in such a direction that the hardening treatment is performed after performing an appropriate finishing work. 6. The method for producing a thrust type ball bearing race according to claim 3, wherein the metal flow is densified when the metal flow is formed by plastic working.