JPH05132743A - Bearing - Google Patents

Abstract

PURPOSE:To provide a bearing remarkably improved in fatigue life to a greater extent than heretofore. CONSTITUTION:The bearing is constituted by sintering a powder of alloy having a composition which consists of, by weight, <=2.0% C, 2.0-5.0% Cr, <=2.0% Si, <=2.0% Mn, <=2.0% V, h12.0% Mo, <=24.0% W, and the balance Fe with inevitable impurities and where 6<=Weq<=24 is satisfied when W+2Mo=Weq and also C specified by C=C-(0.06Cr +0.033W+0.063Mo+0.2V) satisfies C<=0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing, and more particularly to a technical means for improving fatigue strength such as pitting resistance and flaking strength.

[0002]

2. Description of the Related Art In recent years,
For example, as automobiles have higher output and lower fuel consumption, automobile parts are required to be lighter in weight. In particular, if the bearings are made smaller and lighter, the ripple effect is high, which is a strong demand.
Along with this, the need for higher strength and longer life of bearings is rapidly increasing.

Conventionally used as a bearing is high carbon chrome bearing steel (SUJ-2) as a bearing material, which is hardened and tempered to obtain Rockwell hardness H.
RC58-64 or case-hardened steel (SCr42
0H, SCM420H, etc.) is used to carburize and heat-harden the surface hardness of which is HRC58-64.

Various improvement plans based on these materials and treatment methods have been proposed in order to further improve the service life, but the improvement effect thereof is at most about 2 to 5 times.

As a means for increasing the fatigue strength, it is considered effective to uniformly precipitate fine carbides in the material. However, in the case of ordinary ingots, even if a carbide-forming element is added unnecessarily, fine carbides are not formed. It does not precipitate uniformly, rather rather, a large carbide is generated, or this is segregated at the grain boundaries, which rather shortens the life.

[0006]

SUMMARY OF THE INVENTION The present invention has been made against the background of such circumstances, and C: 2.
0% or less, Cr: 2.0 to 5.0%, Si: 2.0% or less, Mn: 2.0% or less, V: 2.0% or less, Mo: 1
2.0% or less, W: 24.0% or less, the balance Fe and unavoidable impurities, and W + 2Mo = Weq,
6 ≦ Weq ≦ 24, and ΔC = C− (0.06C
r + 0.033W + 0.063Mo + 0.2V) is characterized in that the alloy powder having a composition satisfying the condition of ΔC ≦ O is sintered to form a bearing.

As described above, the present invention constitutes the bearing by sintering the alloy powder. That is, as long as the conventional materials and treatment methods are adopted, the life improvement effect is limited to about 5 times and further improvement is difficult. Therefore, in the present invention, attention is paid to the sintering of the alloy powder, and the bearing is obtained from such alloy powder. I did it.

In the case of powder, unlike the ingot, fine carbides can be uniformly precipitated and dispersed. Therefore, in the present invention, appropriate ranges of the tungsten equivalent Weq and the free carbon ΔC are obtained, and each of the materials is By determining the proper balance of the content of the components, the required hardness was secured, and it was possible to obtain a bearing having a significantly longer life and better workability than the conventional one.

For example, according to the present invention, HRC 60 or more,
A bearing having a rolling fatigue life (L ₁₀ ) of 10 ⁸ or more can be obtained.

In the present invention, as the alloy powder, one or more components of P, O and S in the alloy powder are P: 0.015% or less, O: 0.0080% or less, S : It is possible to use those specified to 0.010% or less (claim 2).

Further, the alloy powder may contain one or two kinds of Co and Ni in an amount of Co: 15.0% or less and Ni: 5.0% or less (claim). Item 3).

Alternatively, as the alloy powder, one or more of the P, O, and S components in the alloy powder may be P: 0.
015% or less, O: 0.0080% or less, S: 0.01
It is possible to use one which is specified to 0% or less and which contains one or two kinds of Co and Ni in an amount of Co: 15.0% or less and Ni: 5.0% or less (claim). 4).

Next, the reasons for limiting each component in the present invention will be described in detail. C: 2.0% or less C is limited to 2.0% or less because the toughness deteriorates when the content is more than 2.0%.

Cr: 2.0 to 5.0% Cr is a carbide forming element, and if the amount is less than 2.0%, the formation of carbide is insufficient and the wear resistance is reduced. On the contrary, if the content is more than 5.0%, the manufacturability will decrease.

Si: 2.0% or less If the content of Si is more than 2.0%, embrittlement occurs due to graphitization of cementite and the malleability deteriorates. Therefore, in the present invention, it is 2.0% or less.

Mn: 2.0% or less If the amount of Mn exceeds 2.0%, quenching cracks and embrittlement due to the formation of retained austenite occur.

V: 2.0% or less If the amount of V is more than 2.0%, the hardenability is lowered and the manufacturability is lowered.

Mo: 12.0% or less W: 24.0% or less If Mo and W are 12.0% or less and 24.0% or less, respectively, cost increase and manufacturability decrease can be avoided.

Co: 15.0% or less Co is set to 15.0% or less in order to avoid an increase in cost and prevent embrittlement from occurring.

Ni: 5.0% or less The reason why Ni is limited to 5.0% or less is to avoid an increase in cost and to prevent embrittlement due to the formation of retained austenite.

P: 0.015% or less If P is more than 0.015%, the impact resistance decreases, so the amount is made 0.015% or less.

O: 0.0080% or less O forms an inclusion and tends to become a fracture starting point. Therefore, in the present invention, the amount is limited to 0.0080% or less.

S: 0.010% or less S is limited to 0.010% or less in order to prevent deterioration of toughness and hot workability.

[0024]

EXAMPLES Examples will be described in detail in order to further clarify the characteristics of the present invention. Alloy powders having various compositions shown in Table 1 were produced, sintered, and subjected to a quenching / tempering hardness measurement and a radial rolling life test with a load stress of 5884 N / mm ² . The results are shown in Table 2. In addition, M, N, in Table 1
O is a comparative example, of which M is SUJ-2 powder,
N is SUJ2 ingot, and O is SCM420 carburized material.

The numerical values in the columns of L ₁₀ and L _{50 in} Table 2 represent the number of repetitions when the cumulative damage probability is 10% and 50%, respectively.

[0026]

[Table 1]

[0027]

[Table 2]

As can be seen from these results, all of the examples of the present invention have high hardness and the fatigue life is extended by about 10 times or more as compared with the conventional example (comparative example).

The embodiment of the present invention has been described in detail above, but this is merely an example, and the present invention can be carried out in a mode in which various modifications are made based on the knowledge of those skilled in the art without departing from the spirit of the invention. is there.

Claims (4)

[Claims] 1. C: 2.0% or less by weight Cr: 2.0 to 5.0
% Si: 2.0% or less Mn: 2.0% or less V: 2.0% or less Mo: 12.0% or less W: 24.0% or less The balance Fe and unavoidable impurities W + 2Mo = W
When eq, 6 ≦ Weq ≦ 24, and ΔC = C− (0.06Cr + 0.033W + 0.063
A bearing formed by sintering an alloy powder having a composition satisfying the condition that ΔC defined by Mo + 0.2V) and ΔC ≦ O 2. 2. One or more components of each of P, O and S in the alloy powder are defined as P: 0.015% or less O: 0.0080% or less S: 0.010% or less. The bearing according to claim 1, wherein the bearing is provided. 3. The alloy powder is one or two of Co and Ni.
The bearing according to claim 1, wherein the seeds are contained in an amount of Co: 15.0% or less and Ni: 5.0% or less. 4. One or more components of each of P, O and S in the alloy powder are defined as P: 0.015% or less O: 0.0080% or less S: 0.010% or less and The bearing according to claim 1, which contains one or two kinds of Co and Ni in an amount of Co: 15.0% or less and Ni: 5.0% or less.