| 摘要 |
PROBLEM TO BE SOLVED: To improve the strength characteristics of the spot weld zone of a steel sheet without deteriorating its bulging properties and drawability by allowing it to have a specified compsn. contg. C, Si, Mn, P, S, Al, Ti, Nb, Mg and N. SOLUTION: Steel contains, by weight, 0.0003 to 0.0040% C, <=0.1% Si, 0.03 to 0.8% Mn, 0.001 to 0.12% P, 0.001 to 0.015% S 0.002 to 0.10% Ti, 0.01 to 0.03% Al 0.002 to 0.04% Nb, 0.0001 to 0.0030% Mg and <=0.0040% N. A slab having this componental compsn. is subjected to hot rolling. Desirably, the finishing temp. in the hot rolling is controlled to the one equal to or above the Ar3 point, within 1.5 sec after the hot rolling, it is rapidly cooled to <=750 deg.C at a cooling rate of >=50 deg.C /sec to refine its metallic structure. Then, it is subjected to cold rolling at a rolling ratio of 65 to 95 and is thereafter annealed in the temp. range of 700 deg.C to the Ac3 point in inline annealing type continuous hot dip galvanizing equipment.
|
