Carbon steel sheet having excellent carburization properties, and method for producing same

Abstract

Disclosed is a carbon steel sheet which contains not less than 0.20% by mass but not more than 0.45% by mass of C, not less than 0.05% by mass but not more than 0.8% by mass of Si, not less than 0.85% by mass but not more than 2.0% by mass of Mn, not less than 0.001% by mass but not more than 0.04% by mass of P, not less than 0.0001% by mass but not more than 0.006% by mass of S, not less than 0.01% by mass but not more than 0.1% by mass of Al, not less than 0.005% by mass but not more than 0.3% by mass of Ti, not less than 0.0005% by mass but not more than 0.01% by mass of B, and not less than 0.001% by mass but not more than 0.01% by mass of N. The carbon steel sheet has a K value, which is expressed by 3C + Mn + 0.5Si, of not less than 2.0, a surface hardness, namely a Rockwell hardness of not more than 77 on the B scale, and an average N content of not more than 100 ppm in the region from the surface to the depth of 100 [mu]m. The carbon steel sheet is carburized in a carburizing atmosphere having a carbon potential of not more than 0.6.

Description

technical field [0001] The present invention relates to a carbon steel sheet excellent in carburizing and hardenability and a method for producing the same. [0002] This application claims priority based on Japanese Patent Application No. 2009-079959 for which it applied in Japan on March 27, 2009, and uses the content here. Background technique [0003] Conventionally, automotive parts such as chain parts, gear parts, and clutch parts, or industrial machine parts, have been produced by hardening the surface by heat treatment such as quenching after forming. [0004] However, in recent years, in addition to complicating the shape of parts, wear resistance and fatigue characteristics are required for the parts themselves. Therefore, not only workability to withstand complex machining when processed into parts is required for the billet, but also hardenability for surface hardening is required. The so-called hardenability and workability of the billet are opposite character...

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Problems solved by technology

[0010] Regarding the production conditions of the B-containing steel sheet, Patent Document 1 discloses that annealing is performed in a hydrogen atmosphere or an Ar atmosphere with the nitrogen content suppressed to 10% by volume or less, but there is no mention of the processes before and after the annealing.

In addition, the technology considering the carburizing treatment under the low-carbon potential targeted by the present invention has not been disclosed.

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