Abstract: The present invention provides a case hardening steel which satisfies the following expression (1) representing a relationship between a maximum deformation resistance ?MAX (MPa) and a DI value, the maximum deformation resistance ?MAX (MPa) being obtained when a test piece which has a size of ? 15×22.5 mm and is cut out from a material after spheroidizing, is subjected to compressive deformation by cold forging at a compression ratio of 70% in a state that an end surface thereof is restrained, and the DI value being obtained from a Jominy quenching test: ?MAX<12.8×DI+745 . . . Expression (1). Additionally, the present invention obtains a carburized part by subjecting the case hardening steel to carburizing and quenching.

Abstract: The present invention provides a carburized part having a total amount of TiC, AlN and ZrC, which are precipitate particles, of 4.5×10?10 mole or less per 1 mm2 of grain boundary area of prior austenite grains after carburization. According to the present invention, it is possible to provide a carburized part which allows effective inhibition of abnormal grain growth in spite of a carburizing treatment and makes it possible to solve the problem of reduction in properties caused by abnormal grain growth.

Abstract: Provided is a case hardening steel which allows effective inhibition of abnormal grain growth during carburizing treatment or the like and makes it possible to solve the problem of abnormal grain growth-induced reduction in characteristics. In the case hardening steel, a total amount of TiC, ZrC and AlN which are precipitate particles contained in 100 g of a steel material after subjecting the case hardening steel to hot rolling is 3.5×10?4 mole or less.

Abstract: The present invention provides a case hardening steel which satisfies the following expression (1) representing a relationship between a maximum deformation resistance ?MAX (MPa) and a DI value, the maximum deformation resistance ?MAX (MPa) being obtained when a test piece which has a size of ?15×22.5 mm and is cut out from a material after spheroidizing, is subjected to compressive deformation by cold forging at a compression ratio of 70% in a state that an end surface thereof is restrained, and the DI value being obtained from a Jominy quenching test: ?MAX<12.8×DI+745 . . . Expression (1). Additionally, the present invention obtains a carburized part by subjecting the case hardening steel to carburizing and quenching.

Abstract: The present invention provides a carburized part having a total amount of TiC, AlN and ZrC, which are precipitate particles, of 4.5×10?10 mole or less per 1 mm2 of grain boundary area of prior austenite grains after carburization. According to the present invention, it is possible to provide a carburized part which allows effective inhibition of abnormal grain growth in spite of a carburizing treatment and makes it possible to solve the problem of reduction in properties caused by abnormal grain growth.

Abstract: Provided is a case hardening steel which allows effective inhibition of abnormal grain growth during carburizing treatment or the like and makes it possible to solve the problem of abnormal grain growth-induced reduction in characteristics. In the case hardening steel, a total amount of TiC, ZrC and AlN which are precipitate particles contained in 100 g of a steel material after subjecting the case hardening steel to hot rolling is 3.5×10?4 mole or less.