| 摘要 |
A plate (10) and a tooth (2) are integrally formed from one sheet of a steel plate material. Over the entire surface layer, the plate (10) and tooth (2) have a carburized layer (15, 25) with a higher carbon concentration than the central portion in the thickness direction. The carburized layer (15) in the plate (10) is harder than the central portion (17) in the thickness direction, and the carburized layer (25) in the tooth (2) has undergone quenching treatment and is even harder than the carburized layer (15) of the plate (10). The carbon concentration in the central portions (17, 27) in the thickness direction of the plate (10) and the tooth (2) is 0.2 mass% or less, and the carbon concentration of the carburized layers (15, 25) exceeds 0.2 mass%. |
