Patent ID: 9255313
Filing Date: 2016-02-09
CPC Classification: C21D,C22C,Y10T

Claim Text:
1. A steel sheet for hot press forming, comprising: by weight, carbon (C): 0.15 to 0.35%; silicon (Si): 0.5% or less; manganese (Mn): 1.5 to 2.2%; phosphorus (P): 0.025% or less; sulfur (S): 0.01% or less; aluminum (Al): 0.01 to 0.05%; nitrogen (N): 100 to 200 ppm; titanium (Ti): 0.005 to 0.05%; tungsten (W): 0.005 to 0.1%; and boron (B): 1 to 50 ppm, wherein Ti/N: less than 1.1, where Ti/N is the atomic ratio of the corresponding elements, Ceq expressed by the following formula ranges from 0.48 to 0.58, and temperature Ar3 ranges from 670° C. to 725° C., wherein the steel sheet has a microstructure consisting of ferrite and pearlite, and wherein the steel sheet exhibits a tensile strength of 750 MPa or less before hot press forming or before cold forming and post heat treatment after cold forming and a tensile strength of 1470 MPa or more after hot press forming or after post heat treatment after cold forming, where C, Si, Mn, Ni, Cr and V indicate the contents (wt %) of the respective elements.