METHOD FOR MANUFACTURING HOT-PRESSED HIGH STRENGTH STEEL MEMBER WITH LOW RESIDUAL STRESS

摘要

PPROBLEM TO BE SOLVED: To provide a method for manufacturing a high strength steel member, which is manufactured by carrying out a post processing, such as trimming, piercing, after a hot press process, and has a tensile strength of 980 MPa or higher and a low residual stress. PSOLUTION: The method for manufacturing the hot-pressed high strength steel member with low residual stress is carried out as follows. A steel plate is heated up to a temperature higher than the AcSB3/SBtransformation point and lower than 1,300C, and then is hot-pressed at a temperature higher than the ArSB3/SBtransformation point plus 20C, and is successively post-processed by trimming or piercing at a temperature higher than the ArSB3/SBtransformation point, and then is cooled. By these processes, the member having a tensile strength of 980 MPa or higher, a residual stress of 400 MPa or lower, and a martensite structure of 60% or more by an area fraction can be obtained. PCOPYRIGHT: (C)2006,JPO&NCIPI