Rolling-sliding elements and process for production of the same

Abstract

The present invention provides a rolling and sliding part that can achieve a longer life when used in a rolling bearing using lubricating oil mixed with foreign matter. The rolling and sliding parts are formed of steel composed of C: 0.7-0.9 wt%, Si: 0.05-0.7 wt%, Mn: 0.05-0.7 wt%, Cr: 3.2-5.0 wt%, Al: 0.04 Wt% or less, P: 0.03wt% or less, S: 0.03wt% or less, Ti: 0.005wt% or less, O: 0.0015wt% or less, and contains at least Mo: less than 1.0wt% and V: less than 0.50wt% One, the balance is Fe and unavoidable impurities, and the surface has a carburized surface layer portion. The area ratio of all precipitated carbides in the surface layer is 9 to 30%. Among all the precipitated carbides present in the surface layer, the carbides having an area ratio of 50% or more are M7C3 type and / or M23C6 type. The average grain size of carbides in the surface layer is 0.2 to 0.4 μm, and the amount of retained austenite in the surface layer is 35 to 60%.

Description

technical field [0001] The present invention relates to a rolling and sliding part and a method for producing the same. More specifically, the present invention relates to a rolling part suitable for use as a ring and a rolling element of a rolling bearing using lubricating oil mixed with foreign matter, or a rolling part suitable for use as a sliding Rolling and sliding parts of bearing parts and their preparation methods. [0002] In this specification and claims, the so-called rolling and sliding components refer to components that perform pure rolling contact, pure sliding contact, and mixed rolling contact and sliding contact. Background technique [0003] A rolling and sliding part is known as a rolling bearing using lubricating oil mixed with foreign matter, or as a ring and rolling element of a rolling bearing that is small and lightweight for the purpose of improving automobile fuel consumption, for example. . Sliding parts can be manufactured by taking a finished ...

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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