PURPOSE: To obtain a cold rolled steel plate with intrasurface anisotropy and superior workability, especially high deep drawability by hot rolling a billet for a low C cold rolled steel plate while specifying the finish hot rolling inlet temp., the finish rolling thickness ratio and the finishing temp. and by rapidly carrying out forced cooling, coiling at a prescribed temp., cold rolling and recrystallization annealing.
CONSTITUTION: A low C steel contg. ≤0.08% C and ≤0.4% Mn is hot rolled under the conditions of ≤T1°C (represented by equationI) finish hot rolling inlet temp., ≥13 finish rolling thickness ratio and ≥Ar3 point finishing temp. The rolled steel is forced to be cooled as rapidly as possible to T2°C represented by equation II at ≥20°C/sec cooling rate, and it is coiled at the desired temp. The hot rolled coil is cold rolled at ≥70% cold rolling rate and subjected to recrystallization annealing by continuous annealing or box annealing to obtain the desired cold rolled steel plate with superior workability.
SAYANAGI SHIROU
NAKAJIMA HIROE
