Rolling parts and producing process thereof

Abstract

Various inexpensive rolling elements for use under high interface pressure such as induction hardened gears are provided, which have improved seizure resistance at tooth flanks and a temper hardness of HRC 50 or more at 300 DEG C. To this end, a rolling element is made from a steel material which contains at least 0.5 to 1.5 wt % carbon and 0.2 to 2.0 wt % one or more alloy elements selected from V, Ti, Zr, Nb, Ta and Hf; and in which 0.4 to 4.0% by volume one or more compounds selected from the carbides, nitrides and carbonitrides of the above alloy elements and having an average particle diameter of 0.2 to 5 mum are dispersed. In such a rolling element, the soluble carbon concentration of a martensite parent phase of a rolling contact surface layer is adjusted to 0.3 to 0.8 wt %, the martensite parent phase having been subjected to induction hardening and low temperature tempering, and one or more of the above carbides, nitrides and carbonitrides are dispersed in an amount of 0.4 to 4.0% by volume within the martensite parent phase.

Description

technical field [0001] The invention relates to a rolling part such as a gear manufactured by quenching and hardening a rolling surface layer by means of high-frequency quenching, carburizing and quenching, carburizing and nitriding quenching, nitriding and quenching, and a manufacturing method thereof. Background technique [0002] In the past, in the reducer of construction and civil engineering machinery, etc., from high surface pressure resistance (200kgf / mm 2 From the point of view that the above) is valued, gears that are carburized and quenched or carburized and nitrided and quenched on SCr, SCM, and SNCM low-carbon steels are generally used, but locally with low surface pressure (~ 150kgf / mm 2 ) conditions, medium carbon steel and medium carbon low alloy steel (0.45 to 0.6% by weight C) are used for heat treatment such as induction hardening. [0003] As a gear reducer used in the above-mentioned construction and civil engineering machinery, from the viewpoint of hi...

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Problems solved by technology

[0004] In addition, most of the above-mentioned construction and civil engineering machines cross over obstacles such as rocks and structures while driving, or excavate these obstacles while rotating, and impact loads act on the gears of these driving and rotating gear reducers. Therefore, there is a problem of carburizing and quenching gear damage

[0005] On the other hand, in the hardened gear of induction quenching, although it has higher toughness than the carburized and quenched gear, as mentioned above, when the hardened gear is 150kgf / mm 2 When used under the above high surface pressure, there is a problem in the surface pressure resistance strength that is prone to pitting corrosion, scratches, and early wear.

In addition, on the carburizing and quenching hardened gear, it has a 230kgf / mm 2 The problem of insufficient durability when used under the above high surface pressure, and insufficient surface pressure when used in a miniaturized structure

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