PURPOSE: To produce a titled steel plate stably by hot rolling a steel slab contg. C, Mn, sol. Al, N respectively at prescribed ratios then coiling the same below specific temp. and cold rolling the hot rolled plate and annealing the same continuously above recrystallization temp. then subjecting the plate to soaking followed by quick cooling and an overaging treatment.
CONSTITUTION: The slab of the low carbon Al killed steel consisting of 0.01W 0.05% C, ≤0.15% Mn, 0.020W0.100% sol. Al, ≤0.005% N, and the balance substantially Fe is treated as follows: This steel slab is subjected to finish rolling at a finishing temp. higher than the ordinary Ar3 transformation point then to coiling at ≥650°C to perfect the formation of coarse grains of carbide and the deposition and cohesion of AlN. After the resultant steel plate is cold-rolled, the plate is heated above the recrystallization temp. by continuous annealing and is soaked for ≥10sec. In succession the soaked steel plate is subjected to a so-called overaging treatment wherein the plate is cooled quickly from the above-described temp. above 650°C at ≥200°C/sec cooling rate and is then held for ≥30sec. at 300W500°C to allow solid-solutionized C to deposit, whereby the intended mild cold-rolled steel plate for drawing is obtained.
ONO MASARU
HOSOYA YOSHIHIRO
NAEMURA HIROSHI
NOZOE OSAMU
JITSUKAWA MASAHARU
