PRODUCTION OF BAKING HARDENING COLD ROLLED STEEL SHEET EXCELLENT IN COLD TEMPERATURE STRAIN AGING RESISTANCE

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a baking hardening steel sheet having cold temp. strain aging resistance and excellent baking hardenability even in the case of a solid solution carbon content same as that in the conventional one. ;SOLUTION: A cold rolled steel sheet contg., by weight, 0.001 to 0.008% C, ≤0.005% N and 0.01 to 0.1% sol.Al and contg. 0.003 to 0.06% Ti and 0 to 0.06% Nb is subjected to recrystallization annealing and is furthermore subjected to hot dip galvanizing or hot dip galvanizing and alloying treatment according to necessary, next, a difference is made in the peripheral speeds between upper and lower work rolls at the different peripheral speed rate shown by the following formula with a difference within the range of 0.05 to 3%, and different peripheral speed skinpass rolling is executed, i.e., the different peripheral speed rate = [(V₁/V₀)-1]×100, where V₁: the peripheral speed of the roll on the high peripheral speed side and V₀: the peripheral speed of the roll on the low peripheral speed side.;COPYRIGHT: (C)1998,JPO