Rolling-sliding elements and process for production of the same

Abstract

The invention provides rolling-sliding elements which can attain more prolonged service lives even when used in rolling bearings to which contaminated lubricating oils are applied. Rolling- sliding elements are made of a steel which contains C: 0.7 to 0.9 wt%, Si: 0.05 to 0.7 wt%, Mn: 0.05 to 0.7 wt%, Cr: 3.2 to 5.0 wt%, Al: 0.04 wt% or below, P: 0.03 wt% or below, S: 0.03 wt% or below, Ti: 0.005 wt% or below, O: 0.0015 wt% or below, and at least either of Mo: less than 1.0 wt% and V: less than 0.50 wt% with the balance being Fe and unavoidable impurities and which has a carburized layer on the surface. The deposit carbide content of the layer is adjusted to 9 to 30 % in terms of area ratio. At least 50 % of the deposit carbides present in the layer are of M7C3 type and / or M23C6 type in terms of area ratio. The mean particle diameter of the carbides present in the layer is adjusted to 0.2 to 0.4 mum and the residual austenite content of the layer is adjusted to 35 to 60 %.

Description

Technical field [0001] The present invention relates to a rolling and sliding component and a preparation method thereof. More specifically, the present invention relates to a rolling component suitable for use as a ring and rolling element of a rolling bearing using lubricating oil mixed with foreign matter, or suitable for use as a sliding component. Rolling and sliding parts of bearing parts and preparation methods thereof. [0002] In this specification and claims, the so-called rolling and sliding parts refer to parts that perform pure rolling contact, pure sliding contact, and mixing rolling contact and sliding contact. Background technique [0003] As a rolling bearing used with lubricating oil mixed with foreign matter, or, for example, a ring and rolling element of a rolling bearing that is reduced in size and weight for the purpose of increasing automobile fuel costs, a rolling and sliding member is known. , Sliding parts can be prepared by the following method, that is...

AI Technical Summary

Problems solved by technology

However, when JIS SUJ2 is used, most of the carbides precipitated in the surface layer by carburizing treatment are cementite or the like. M with a Vickers hardness of 1150 to 1760 3 C-type carbide {=Fe 3 C, (Fe, Cr) 3 C}, this M 3 C-type carbides and other alloy carbides (M 7 C 3 , MC) compared with carburizing, the growth rate of carbides is faster (Reference: Takayama: Journal of the Japan Metal Society, 11, 45 (1981), 1195), and the hardness is lower (M 7 C 3 and the Vickers hardness of MC is above 1800)

Therefore, since the average particle size of carbides becomes larger, there is a problem that the amount of dispersed precipitation strengthening decreases, and the effect of increasing hardness by carbide precipitation decreases.

In addition, the coarsening of carbides is induced, and as a result, there is a problem that the effect of improving the rolling life cannot be sufficiently obtained.

[0006] However, increasing the amount of Cr, using M 7 C 3 Attempts to improve the rolling life when foreign substances are mixed in are not novel in themselves, and for example, inventions described in Patent Document 2 and the like have been disclosed.

However, although this invention describes the type and area ratio of carbides after carburizing, it does not specifically disclose the distribution state of the number, size, etc., and simply points out that it is necessary to prevent coarsening.

Therefore, when the carbides are not sufficiently refined and the amount of retained austenite is as large as about 50%, there is a problem that the high hardness cannot be maintained and a sufficient life improvement effect cannot be obtained.

[0007] In addition, Patent Document 3 discloses a method of prolonging the rolling life in a lubricating environment mixed with foreign matter. This method uses known carburizing steel and performs all carburizing or carbonitriding treatments to ensure a certain degree of surface hardness. , and further increase the amount of retained austenite, but this method has the same problem as the above-mentioned JIS SUJ2 case, and there is a problem that excellent rolling life cannot be obtained

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