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.
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 Ac3 transformation point and lower than 1,300°C, and then is hot-pressed at a temperature higher than the Ar3 transformation point plus 20°C, and is successively post-processed by trimming or piercing at a temperature higher than the Ar3 transformation 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.
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