JP2002012919A - Bearing parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive bearing part improved in cold workability and extended in rolling fatigue limit. SOLUTION: This bearing part is formed of a steel comprising, by weight, 0.6-0.8% C, 0.05-0.25% Si, 0.2-0.9% Mn, 0.4-1.2% Cr, one or two kinds of 0.10-0.30% Mo and 0.03-0.10% V, and the balance Fe with inevitable impurities. The steel has the largest carbide particle diameter of less than 1.5 μm after the treatments of spheroidizing annealing including the furnace cooling at the cooling rate of 10 deg.C/hr, quenching and tempering, and also the carbide amount of 2-7% in terms of area rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing component used as a bearing ring or a rolling element of a rolling bearing.

[0002]

2. Description of the Related Art Conventionally, bearing parts are, for example, JIS SUJ
2 made of high carbon chromium steel.

[0003]

[Problems to be solved by the invention] However, JIS S
Since UJ2 has a large carbon content, there is a problem that the processability is inferior and the cost is high. In addition, there is a problem that the life is likely to vary due to the relatively large particle size of the carbide after the quenching treatment and the tempering treatment.

An object of the present invention is to provide a bearing component which solves the above-mentioned problem.

[0005]

A bearing component according to the present invention has a C content of 0.6 to 0.8 wt% and a Si content of 0.05 to 0.25 wt%.
%, Mn 0.2-0.9wt%, Cr 0.4-1.2wt%
And Mo 0.10 to 0.30 wt% and V
Spheroidizing annealing, quenching including furnace cooling at a cooling rate of 10 ° C./hour, containing one or two of 0.03 to 0.10 wt%, the balance being Fe and the unavoidable impurities. After the treatment and the tempering treatment, the maximum carbide particle size is 1.5 μm or less, and the amount of carbide is 2 to 7% in area ratio.

The reasons for limiting the alloy components in the above steel are as follows.

C: 0.6-0.8 wt% C has the property of increasing the quench hardness, but if its content is less than 0.6 wt%, the quench hardness is insufficient, There is a problem that the wear resistance becomes insufficient and the load capacity becomes small. On the other hand, if the content of C exceeds 0.8 wt%, it becomes difficult to reduce the size of carbides, causing variations in the rolling life, as well as an increase in deformation resistance and a decrease in cold workability. Moreover, the cost increases. Therefore, the content of C should be selected in the range of 0.6 to 0.8 wt%, and particularly preferably in the range of 0.65 to 0.75 wt%.

Si: 0.05-0.25 wt% Si has the property of shortening the time required for deoxidation.
If the content is less than 0.05% by weight, a long time is required for deoxidation, and the cost increases. On the other hand, when the content of Si is 0.2
If the content exceeds 5 wt%, spheroidization of the carbides becomes difficult and the carbides become reticulated carbides, and the deformation resistance increases and the cold workability decreases. Therefore, the content of Si is 0.05 to 0.1.
It should be selected within the range of 25 wt%, especially 0.10 to
Preferably, it is in the range of 0.20 wt%.

Mn: 0.2-0.9 wt% Mn has the property of improving hardenability, but if its content is less than 0.2 wt%, its effect is reduced. On the other hand, if the content of Mn exceeds 0.9 wt%, the toughness is reduced and the workability is reduced. Therefore, the content of Mn should be selected within the range of 0.2 to 0.9 wt%, and particularly preferably within the range of 0.2 to 0.5 wt%.

Cr: 0.4-1.2 wt% Cr has the property of increasing the strength, but if its content is less than 0.4 wt%, spheroidization of carbides becomes difficult, resulting in reticulated carbides. On the other hand, if the Cr content exceeds 1.2% by weight, the cost is increased and the effect of increasing the strength is not further improved. Therefore, the content of Cr is 0.4
１．２1.2 wt% should be selected, but especially 1.0
Preferably, it is in the range of ~ 1.2 wt%.

Mo 0.10 to 0.30 wt% and V0.
One or two of 03 to 0.10 wt% Mo and V compensate for the decrease in hardenability caused by reducing the content of each of the above alloy components as compared with the normal JIS SUJ2 material, and make the microstructure fine. However, if the content of Mo is less than 0.10 wt% and the content of V is less than 0.03 wt%, the effect is not sufficiently exhibited, and the content of Mo is 0.30 wt%. If the V content exceeds 0.10 wt%, the cost increases. Therefore, the content of Mo should be selected within the range of 0.10 to 0.30 wt%, and the content of V should be selected within the range of 0.03 to 0.10 wt%. .03-
It is preferable to be within the range of 0.05 wt%.

In the above, the reason why the maximum carbide particle size after the spheroidizing annealing treatment including the furnace cooling at a cooling rate of 10 ° C./hour, the quenching treatment and the tempering treatment is limited to 1.5 μm or less is as follows. This is because if the maximum carbide particle size exceeds 1.5 μm, the rolling fatigue life becomes short. That is, as a result of an experimental study performed by the present inventors, the relationship between the particle size of the largest carbide in the bearing component and the rolling fatigue life (when grease lubricated) is shown in FIG.
This is because it was found that the rolling fatigue life was shortened when the maximum carbide particle size exceeded 1.5 μm. The particle size of the largest carbide is particularly preferably 1.0 μm or less. In FIG. 1, the solid line shows the case where the amount of carbide is 2% in area ratio, and the broken line shows the case where the amount of carbide is 7% in area ratio.

The reason why the amount of carbide after the spheroidizing annealing including quenching at a cooling rate of 10 ° C./hour, quenching and tempering is limited to an area ratio of 2 to 7% is as follows. It is as follows. That is, as a result of the present inventors' experimental research, the relationship between the amount of carbide and the amount of wear in the bearing component is as shown in FIG. 2, and the amount of carbide in the bearing component is less than 2% in area ratio. , The wear amount increases and the wear resistance decreases, and the relationship between the amount of carbide in the bearing parts and the rolling fatigue life (when grease is lubricated) is as shown in FIG. This is because it has been found that when the amount of carbide exceeds 7% in area ratio, the rolling fatigue life becomes short. The amount of carbide is particularly preferably 3 to 5% in area ratio.

Such a bearing component is manufactured, for example, by the following two methods.

In the first manufacturing method, a steel bar which has been subjected to spheroidizing annealing is cut into a predetermined size, then formed into a ring shape by cold forging, and further formed into a predetermined shape by turning. Next, the steel sheet is heated at 850 ° C. for 30 to 40 minutes and then rapidly cooled to perform a quenching treatment. Finally, 160-18
Tempering treatment is performed by heating at 0 ° C. for 1 to 2 hours. Thus, a bearing component is manufactured.

In the second manufacturing method, a rolled steel bar is cut into a predetermined size, and then formed into a ring by hot forging. Then, after heating at 760 ° C. for 6 to 7 hours, 680 ° C.
A spheroidizing annealing treatment is performed by cooling the furnace to 10 ° C. at a cooling rate of 10 ° C./hour, followed by air cooling. Next, a predetermined shape is formed by turning. Then, at 850 ° C, 30 ~ 4
After quenching after heating for 0 minutes, quenching is performed.
Finally, a tempering treatment is performed by heating at 160 to 180 ° C. for 1 to 2 hours. Thus, a bearing component is manufactured.

[0017]

[Function and Effect of the Invention] C 0.6-0.8wt%, Si
0.05-0.25wt%, Mn0.2-0.9wt%, C
r 0.4-1.2 wt%, and Mo0.10
Spheroidization containing one or two of 0.30 wt% and V 0.03 to 0.10 wt%, made of steel consisting of balance of Fe and unavoidable impurities, including furnace cooling at a cooling rate of 10 ° C./hour Since the maximum carbide particle size after annealing, quenching, and tempering treatment is 1.5 μm or less and the amount of carbide is 2 to 7% in area ratio, conventional high carbon materials such as JIS SUJ2 are used. Compared to chromium bearing steel, it has better cold workability, and when used as a bearing component, has a longer rolling fatigue life and lower cost.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below together with comparative examples.

[0019]

[Table 1]

After performing spheroidizing annealing on a steel bar composed of ten kinds of steels having the compositions shown in Table 1, each steel bar is cut into a predetermined size, then formed into a plate by cold forging, and further turned. As a result, a disk-shaped sample having a diameter of 65 mm and a thickness of 11 mm was prepared. Next, each sample was subjected to a quenching treatment by heating at 850 ° C. for 40 minutes and oil-cooling. Finally, each sample was tempered by heating at 160 ° C. for 2 hours. Then, the particle size of the largest carbide and the area ratio of the carbide in each sample were measured. The results are also summarized in Table 1.

In addition, each sample, a JIS SUJ2 disc and a JIS
Combined with a SUJ2 ball, a JIS SUJ2 disc was subjected to 1800 c. In spindle oil # 60 while applying a thrust load of 5320 MPa to each sample using a thrust rolling fatigue life tester. p. m, and a rolling fatigue life test was performed by rolling a JIS SUJ2 ball. The bearing steel of Comparative Example 1 (JIS S
Samples of B ₁₀ life consisting UJ2) was examined life ratio in the case of the 1. Table 2 shows the results.

[0022]

[Table 2]

Further, after spheroidizing annealing was applied to a material made of ten kinds of steels having the compositions shown in Table 1, a cylindrical sample having a diameter of 6 mm and a length of 12 mm was made from each material.
Then, using each of the samples, the deformation resistance at the time of 25 ° C. and restrained compression deformation at a compressibility of 60% was measured,
The deformation resistance ratio when the deformation resistance of the bearing steel sample of Comparative Example 1 was set to 1 was examined. Table 2 shows the results.

Further, the columnar sample produced in the same manner as described above was subjected to constrained compressive deformation at a temperature of 25 ° C. by changing the compressibility by 5%, and the lowest compressibility at which cracking was observed (limit Compression ratio). Table 2 shows the results.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the particle size of the largest carbide in a bearing component and the rolling fatigue life.

FIG. 2 is a graph showing the relationship between the amount of carbide in a bearing component and the amount of wear.

FIG. 3 is a graph showing the relationship between the amount of carbide in a bearing component and the rolling fatigue life.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) F16C 33/44 F16C 33/44 33/62 33/62 (72) Inventor Atsuhiko Ota Minamisenba, Chuo-ku, Osaka-shi F-term (reference) 3-8101 Koyo Seiko Co., Ltd. 3J101 BA10 BA70 DA03 EA01 EA03 FA31 4K042 AA22 BA03 DA01 DA02 DA03 DE01

Claims (1)

[Claims] (1) C 0.6-0.8 wt%, Si 0.05-
0.25wt%, Mn0.2 ~ 0.9wt%, Cr0.4 ~
Including 1.2wt%, Mo0.10-0.30wt%
And one or two of V 0.03 to 0.10 wt%
The size of the largest carbide after being subjected to spheroidizing annealing, including quenching and tempering, including furnace cooling at a cooling rate of 10 ° C./hour, containing seeds and the balance of Fe and unavoidable impurities. A bearing component having a thickness of 1.5 μm or less and an amount of carbide of 2 to 7% in area ratio.