| 摘要 |
PCT No. PCT/JP81/00289 Sec. 371 Date Jun. 16, 1982 Sec. 102(e) Date Jun. 16, 1982 PCT Filed Oct. 19, 1981 PCT Pub. No. WO82/01566 PCT Pub. Date May 13, 1982.The present invention belongs to a technical field of cold rolled steel sheet. The present invention provides a thin steel sheet suitable to be formed into, for example, an external automotive plate by a method including an appearance-finishing step by bake coating as a final step after drawing (such as press molding). The present invention aims to improve remarkably the yield strength, so-called bake hardenability, of the thin steel sheet in order to produce advantageously a light weight automobile. In addition, the invention aims to compensate advantageously the deterioration of dent resistance of the automobile due to the lowering of the weight, without deteriorating the &upbar& r value, which is an indication of the press moldability of the thin steel sheet. Accordingly, the present invention discloses an effective compounding amount of Nb, which acts to fix C and N in the steel in the presence of a proper amount of Al, and an annealing condition capable of developing effectively the contribution of Nb. |
