Case-hardened steel article

Abstract

This case-hardened steel article is provided with a base metal and a carburizing layer, wherein the base metal has a predetermined chemical composition. The number density of Ti-based precipitates having a circle-equivalent diameter of 5-50 nm in a surface layer region from the surface to a depth of 0.1 mm is at least 0.5 precipitates per mu m2. The number density of AlN having a circle-equivalent diameter of 50 nm to 100 nm in said surface layer region does not exceed 0.5 AlN per mu m2.

Description

technical field [0001] The present invention relates to a case-hardened steel component. [0002] This application is based on Japanese Patent Application No. 2015-070701 for which it applied in Japan on March 31, 2015, and claims the priority thereof, and uses the content here. Background technique [0003] Parts for mechanical structural use may be damaged due to sudden and large stress. In particular, in vehicle gears such as differential gears, transmission gears, and carburized shafts with gears, the dedendum may be damaged due to impact fracture due to the load when the vehicle is suddenly started or stopped. In order to prevent such a phenomenon, especially in differential gears and transmission gears, it is desired to further increase the impact value (shock resistance characteristic). By sufficiently increasing the impact value of these machine structural parts, the amount of material used for the machine structural parts can be reduced, and weight reduction of th...

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Problems solved by technology

However, since AlN has low thermal stability and is easy to coarsen, the effect of refining crystal grains is insufficient

[0007] As described above, the technologies disclosed in Patent Document 1 and Patent Document 2 cannot sufficiently meet the demand for obtaining a case-hardened steel part having excellent impact value and high hot-rollability.

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