Skin-baked steel with excellent coarse grain prevention characteristics, fatigue characteristics, and machinability during carburizing and its manufacturing method

摘要

PROBLEM TO BE SOLVED: To provide a case hardened steel excellent in coarse particle prevention property and machinability during carburization, capable of suppressing heat treatment strain due to carburization hardening and providing excellent fatigue property after carburization hardening and a manufacturing method therefor.SOLUTION: There is provided a case hardened steel containing C:0.10 to 0.30%, Si:0.02 to 1.5%, Mn:0.3 to 1.8%, S:over 0.020 to 0.050%, Cr:0.4 to 2.0%, Al:0.005 to 0.05%, Ti:0.06 to 0.20%, Bi:0.0001 to 0.0050% and further one or more kind of Ca:0.0005 to 0.0050%, Mg:0.0003 to 0.0050%, Te:0.0003 to 0.20%, satisfying following formula (1) and excellent in coarse particle prevention property, fatigue property and machinability. 5.0≥Ti/S≥3.0 Formula (1), where Ti is the content of Ti (mass%) and S is the content of S (mass%).SELECTED DRAWING: None