STEEL SHEET EXCELLENT IN PAINT BAKE HARDENABILITY AND RETARDED NATURAL AGING HARDENABILITY AND ITS MANUFACTURING PROCESS

摘要

PROBLEM TO BE SOLVED: To provide a steel sheet of good paint bake hardenability and retarded natural aging hardenability and its manufacturing process.;SOLUTION: The steel sheet which contains, by mass%, 0.0005-0.0025% C, ≤2.0% Si, ≤3.0% Mn, ≤0.15% P, ≤0.015% S, 0.2-1.4% Cr, 0.003-0.020% O, ≤0.008% Al, 0.001-0.005% N and the balance Fe and inevitable impurities is offered. It is preferable that solid-soluted C is ≤0.0020% and solid-soluted N is 0.0005-0.004%. A hot rolled and cold rolled steel sheet, and further a cold steel sheet for a galvanized sheet which has good paint bake hardenability and retarded natural aging hardenability is obtained by remaining solid-soluted N and adding Cr and O into an ultralow carbon steel.;COPYRIGHT: (C)2004,JPO