STEEL SHEET FOR EXCELLENT PANEL APPEARANCE AND DENT RESISTANCE AFTER PANEL-FORMING

摘要

A cold-rolled steel sheet or a zinc or zinc alloy layercoated steel sheet containing 0.0010 to 0.01 wt% of C and having asteel composition containing one or two kinds of 0.005 to 0.08 wt%of Nb and 0.01 to 0.07 wt% of Ti in the ranges given by {(12/93)Nb+ (12/48)Ti*} ~ 0.0005, 0 ~ C- {(12/93)Nb + (12/48)Ti*} ~ 0.0015,and Ti* = Ti- {(48/32)S+(48/14)N } , in which a bake hardenabilityBH f the steel sheet at 170 °C x 20 min after 2 % tensile prestrainis 10 to 35 MPa and the BH (MPa) and a yield strength YP (MPa) ofthe steel sheet satisfy the ranges given by BH~exp(-0.115 . YP+23.0)and 0.67 . BH+160~YP~-0.8 . BH+280.