PRODUCTION OF EXTRA THIN SILICON STEEL SHEET EXCELLENT IN MAGNETIC PROPERTY AND EXTRA THIN SILICON STEEL SHEET EXCELLENT IN MAGNETIC PROPERTY

摘要

PROBLEM TO BE SOLVED: To produce an extra thin silicon steel sheet excellent in magnetic properties by subjecting an extra thin cold rolled steel sheet contg. specified amounts of C, Si, Mn, P, S, Al, N, Ti and Nb to annealing in an atmosphere contg. nitrogen and in an atmosphere contg. no nitrogen in succession. ;SOLUTION: A hot rolled steel sheet contg., by weight, ≤0.01% C, 2.5 to 7% Si, 0.005 to 0.12% Mn ≤0.02% P, 0.002 to 0.005% S, 0.0015 to 0.006% solAl and 0.001 to 0.008%. N with ≤0.003% Ti+Nb as impurities is subjected to descaling and is thereafter subjected to cold rolling for three times including process annealing at 70 to 950°C for ≥30sec to regulate its sheet thickness to ≤0.20mm. This cold rolled steel sheet is subjected to two stage annealing. In the primary stage, it is heated at 850 to 950°C at ≥20°C/hr temp. rising rate in a reducing atmosphere of ≥70vol% N₂ and is held for ≥3hr. In the succeeding secondary stage, it is held to 900 to 1,300°C for ≥30sec in a reducing atmosphere contg. no N₂, in a nonoxidizing atmosphere contg. no N₂ under ≤5Pa or in a vacuum under ≤0.5Pa oxygen partial pressure.;COPYRIGHT: (C)1997,JPO