METHOD FOR PRODUCING ROLLING STOCK FOR DEAD SOFT STEEL SHEET HAVING HIGH AGE HARDENABILITY

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a rolling stock for a cold rolled steel sheet of high nitrogen extra low carbon which has excellent age hardenability by aging heat treatment for increasing strength after work forming such as pressing without generating the problems of surface defects in the steel sheet and defects caused by inclusions.;SOLUTION: The rolling stock for a dead soft steel sheet of ≤0.0050 mass% C is produced. In this case, molten iron is subjected to primary decarburization refining, and the components in the molten steel after the primary decarburization refining are controlled to the ranges satisfying the following inequality of [mass%N]-0.15[mass%C]≥0.0060. Next, the molten steel is subjected to secondary decarburization refining to an extra low carbon concentration region of ≤0.0050 mass% C by using vacuum degassing equipment. After that, the molten steel is subjected to deoxidation by Al so that the content of Al reaches ≥0.005 mass% after the deoxidation. Further, the components in the molten steel are controlled so as to satisfy 0.0050 to 0.0250 mass% N and [mass%Al].[mass%N]≤0.0004, and so that the content of solid solution N reaches a prescribed one or higher. Then, the molten steel is subjected to continuous casting.;COPYRIGHT: (C)2002,JPO