Steel material for vacuum carburization, and method of manufacturing the same

Abstract

The invention provides a carburization part having sufficient surface fatigue strength and a carburization part having surface fatigue strength and flex fatigue strength; and a steel material for obtaining the carburization parts. The present invention is a steel material for vacuum carburization containing C, Si, Mn, S, P, Cr, Mo, V, Al, and N, in which an average circle-equivalent diameter of avanadium carbide is 25 nm or less. The present invention also includes a method for manufacturing the steel material. Specifically, the method includes subjecting a steel having a predetermined chemical ingredient composition to blooming by holding the steel at 1200 DEG C or above for 30-300 minutes, followed by hot rolling by setting a heating temperature before the hot rolling to 950 DEG C or above and heating retention time to 30 minutes to 5 hours.

Description

[0001] This application is a divisional application of PCT / JP2015 / 057833 with application number: 201580014824.7, application date: 2015.3.17, and title of invention: "Steel for vacuum carburizing and its manufacturing method". technical field [0002] The present invention relates to a steel material for vacuum carburizing, and more specifically, to a steel material for obtaining a carburized part having excellent surface fatigue properties and bending fatigue properties after vacuum carburizing, and to a manufacturing method and a steel material using the same carburized parts, and methods of making such parts. The steel material of the present invention is useful as raw materials such as gears and shafts used in automobiles, construction machinery, and various other industrial machinery. Hereinafter, the case where it is applied to automobile gears will be described as an example, but it is not limited thereto. mean. Background technique [0003] Looking at the environme...

AI Technical Summary

Problems solved by technology

The purpose of the description is that surface hardening such as gas carburizing, vacuum carburizing, carbonitriding, high concentration carburizing (hypereutectoid carburizing) and shot peening can also be performed on this case hardened steel. In the technology of Patent Document 2, it is considered that the improvement of the softening property of the surface layer is insufficient.

Therefore, according to the technology of Patent Document 2, surface fatigue strength and bending fatigue strength that can sufficiently cope with the miniaturization of components and high stress load required recently cannot be obtained.

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