PURPOSE: To obtain a raw plate for soft quality surface treatment having uniform quality and excellent deep drawability by containing the specific quantities of C, Mn, P, Al, and N in an Al killed steel, hot-rolling this Al killed steel at the specific temp. and next executing the over-ageing treatment after recrystallizing annealing by the continuous annealing method.
CONSTITUTION: The low carbon Al killed steel is contained by wt% of 0.01W0.06% C, 0.05W0.60% Mn, ≤0.02% P, 0.005W0.008% acid soluble Al, ≤0.0070% N and remaining part of Fe with inevitable impurities. The Al killed steel is hot-rolled, wound at 600W700°C and cold-rolled. Next, by the continuous annealing method, the recrystallizing annealing is executed at the temp. range of ≥recrystallizing temp. and ≤850°C for 5secW5min. After that, it is cooled at 5W250°C/sec cooling velocity and the over-ageing treatment at 300W500°C for 30W180sec is executed. Further, the Al killed steel is cooled to Ar3 the transformation point or below and next after heating, it may be executed by the same method as the above. In this way, T-1 to T-3 class surface treating steel plate having excellent uniformity for quality and high strength to pressure is obtd.
KONO TAKESHI
NOSAKA SHOJI
YAMASHITA YASUHIKO
TANAKA SEIICHI
