Patent ID: 9321092
Filing Date: 2016-04-26
CPC Classification: B21D

Claim Text:
1. A method for forming a steel sheet by hot pressing, the method comprising the steps of: a primary forming step of obtaining a primary formed product by performing plastic working in which a heated steel sheet is pressed by upper and lower dies of a primary forming die set for a predetermined time period so as to be plastically deformed along a pressing surface of each of the upper and lower dies; a secondary forming step of carrying the primary formed product into a secondary forming die set, and machining the primary formed product with upper and lower dies of the secondary forming die set for a predetermined time period to obtain a secondary formed product; and at least one hardening step of carrying the secondary formed product into a cooling die set placed in a hydraulic press controlled by a servomotor, and allowing upper and lower dies of the cooling die set to hold the secondary formed product under pressure for a longer time period than the time period of each of the primary and secondary forming steps to obtain a hardened final formed product, wherein: