| 摘要 |
<p>PURPOSE:To manufacture a high (r) value galvanized cold rolled extremely low-carbon steel sheet excellent in secondary working brittleness or baking hardenability with good productivity by subjecting dead soft steel having a specified compsn. mixed with Ti or Nb to specified hot rolling and thereafter executing cold rolling and galvanizing. CONSTITUTION:Steel contg., by weight, <=0.006% C, <=0.2% Si, 0.05 to 1.0% Mn, <=0.10% P, <=0.10% S, 0.01 to 0.08% solAl and <=0.005% N, furthermore contg. <=0.08% Ti and <=0.06% Nb as well as 1<={(Ti-48/32S 48/14N)/48+Nb/93}/(C/12), moreover contg., at need, <=0.002% B and the balance Fe with inevitable impurities is subjected to rough rolling, is thereafter subjected to hot rolling at 600 to 800 deg.C at >=50% draft, is coiled at 400 to 800 deg.C and is subjected to pickling and cold rolling. This steel sheet is subjected to continuous carburizing and annealing at the recrystallization temp. or above. The steel sheet contg. 3 to 30ppm solid soln. C obtd. by the above method is cooled to 350 to 550 deg.C and is thereafter subjected to continuous galvanizing.</p> |
