METHOD OF PRODUCING HIGH Si-CONTAINING HIGH TENSILE STRENGTH STEEL SHEET HAVING EXCELLENT PHOSPHATE FILM TREATABILITY

摘要

PROBLEM TO BE SOLVED: To provide a method which is useful for controlling an Si-containing oxide layer formed in annealing, and efficiently removing the formed Si- containing oxide layer so as to improve the phosphate film treatability of a high Si-containing high tensile strength steel sheet containing ≥0.5 mass% Si.;SOLUTION: In the method of producing a high tensile strength steel sheet by subjecting an oxide film to removal treatment after annealing, the annealing is performed under the condition so as to satisfy the oxygen partial pressure of 1.0×10^-23 to 1.0×10^-19%, and, after that, cooling is performed at the average cooling rate of ≥100°C/s in the temperature range of 800 to 450°C. As the removal treatment of the oxide film, the surface of the steel sheet is ground by ≥2.0 g/m², and, after that, pickling treatment is performed.;COPYRIGHT: (C)2003,JPO