HIGH-STRENGTH, COLD-ROLLED STEEL SHEET EXCELLENT IN FORMABILITY, HOT-DIP ZINC COATED HIGH-STRENGTH COLD ROLLED STEEL SHEET, AND METHOD OF MANUFACTURING SAID SHEETS

摘要

A method of manufacturing high-strength, cold-rolled steel sheet excellent in formability. When increasing the strength of extra low-carbon steel as a base material including Nb or a combination of Ti and Nb by adding solid-solution strengthening element thereto, quantities of P and Si to be added which have been used in quantities are decreased whereas Mn and Cr are liberally added. Thus, the yield strength is prevented from increasing and the strength can be increased, whereby a high strength cold rolled steel sheet excellent in surface formability and in resistance to denting can be manufactured. $$