| 摘要 |
<p>PURPOSE:To improve deep drawability and baking hardenability by adding specific amounts of Ti and Nb to an ultralow carbon steel and applying hot rolling, cold rolling, and annealing under respectively specified conditions. CONSTITUTION:The steel has a composition consisting of, by weight, <=0.01% C, <=0.5% Si, 0.05-2.0% Mn, <=0.1% P, <=0.015% S, 0.005-0.08% sol.Al, <=0.006% N, <=0.1% Ti, <=0.1% Nb, and the balance Fe. Further, Ti and Nb are added independently or in combination and satisfy the conditions in equation I and inequality II. This steel is roughed at a temp. not lower than the Ar, point, hot-rolled under the condition of >=40% total draft in an unrecrystallized ferrite region and in the region between 600 deg.C and the Ar3 point, coiled, and pickled. Subsequently, cold rolling is done under the conditions of >=30% cold rolling rate and 80-95% total draft of cold rolling in an unrecrystallized ferrite region. Then, continuous annealing is done in a carburizing atmosphere at a temp. not lower than the recrystallization temp., by which the amount of solid-solution C is controlled to 5-30ppm.</p> |
