Production method null of the alloy hot dip zincing cold rolling steel sheet for the deep drawing which is superior in the printing hardenability and resistance powder ring

摘要

PURPOSE:To obtain the steel sheet by using a dead-soft carbon steel in which Ti of prescribed composition is added, limiting the amount of S, and also limiting cooling velocities after recrystallization annealing and after alloying treatment, respectively, in a steel sheet for automobile outer and inner sheets. CONSTITUTION:A steel having a composition consisting of, by weight, =0.005% C, =1.0% Si, =1.0% Mn, =0.1 % P, =0.002% S, 0.01-0.1% Al, =0.005% H, Ti in the amount of =[(C%)-12/32(S%)]X4% by effective Ti(Ti*) represented by an equation and =0.1% by Ti quantity, and the balance Fe is used. This steel is continuously cast into a slab, and, directly after reheating or casting, finish hot rolling is completed at a temp. of the Ar3 point or above and the resulting plate is coiled, pickled, and cold-rolled by the ordinary method, and the resulting sheet is subjected to recrystallization annealing in the temp. region between 800 deg.C and the Ac3 point for =1sec. Successively, this steel is cooled at =50 deg.C/s cooling rate, subjected to hot dip galvanizing and further to alloying treatment, and then cooled at =10 deg.C/s cooling rate.