Patent ID: 11898218
Assignee: HYUNDAI STEEL COMPANY
Field: Materials, metallurgy (Chemistry)
Classification: CPC C  B | IPC B  C

Claim 0:
1. A method of manufacturing a material for hot stamping, the method comprising:
reheating a slab at a slab reheating temperature range of 1,180° C. to 1,280° C.;
manufacturing a steel sheet by hot rolling the reheated slab at a finishing delivery temperature range of 830° C. to 930° C.; and
coiling the steel sheet at a coiling temperature range of greater than 700° C. and less than or equal to 780° C. and forming fine precipitates in the steel sheet,
uncoiling the coiled steel sheet and then cold rolling the steel sheet, and
performing annealing heat treatment on the cold rolled steel sheet at a temperature greater than or equal to 700° C., and
forming a plating layer on the annealing heat-treated steel sheet by immersing the steel sheet in a plating bath having a temperature of about 650° C. to about 700° C.,
wherein the fine precipitates include nitride or carbide of at least one of titanium (Ti), niobium (Nb), and vanadium (V), and trap hydrogen,
wherein the slab comprises carbon (C) in an amount of 0.32 wt % to 0.50 wt %, silicon (Si) in an amount of 0.15 wt % to 0.70 wt %, manganese (Mn) in an amount of 0.5 wt % to 2.0 wt %, phosphorus (P) in an amount less than 0.05 wt %, sulfur (S) in an amount less than 0.01 wt %, chromium (Cr) in an amount of 0.1 wt % to 0.5 wt %, boron (B) in an amount of 0.001 wt % to 0.005 wt %, calcium (Ca) in an amount less than or equal to 0.003 wt %, an additive in an amount of less than 0.1 wt %, balance iron (Fe), and other inevitable impurities,
wherein the additive comprises at least one of titanium (Ti), niobium (Nb), and vanadium (V),
wherein a tensile strength of the steel sheet after hot stamping is greater than or equal to 1,680 Mpa, bendability of the steel sheet after hot stamping is greater than or equal to 40°, and an amount of activated hydrogen in the steel sheet after hot stamping is less than or equal to 0.5 wppm,
wherein an amount greater than or equal to 90% of the fine precipitates is formed to have a diameter less than or equal to 0.01 μm,
wherein an amount greater than or equal to 60% of the fine precipitates are formed to have a diameter less than or equal to 0.005 μm,
wherein a mean distance between the fine precipitates is greater than or equal to 0.15 μm and less than or equal to 0.4 μm.