PURPOSE: To stably produce a nonoriented silicon steel sheet having superior magnetic properties by subjecting an extra low carbon steel slab of specific composition to hot rolling and cold rolling under specific temp. conditions and then applying heat treatment to the resulting sheet under specific conditions.
CONSTITUTION: A steel slab, containing, by weight, <0.005% C, 0.01-1.50% Si, 0.2-1.0% Mn, <0.2% P, <0.01% S, ≤0.004% or 0.1-0.5% Al, and <0.005% N and satisfying Si+Al<1.7%, is hot-rolled at <750°C finish rolling finishing temp. The resulting hot rolled plate is coiled at ≤600°C and picked to remove scale. After this plate is cold-rolled once or is cold-rolled two or more times, while process-annealed between cold rolling stages, at >80% draft at final rolling, the resulting sheet is subjected to temp. rise up to temp. T1°C satisfying inequality I at ≥1000°C/min heating rate and held at this temp. for 10-40sec. Then, the sheet is subjected to temp. rise up to a temp. in the region between Ti°C and (Ac3+10)°C at (100 to 500)°C/min heating rate and held at T2°C satisfying inequality II for 30sec to 5min.
TOMITA KUNIKAZU
ODA YOSHIHIKO
Next Patent: PRODUCTION OF GRAIN ORIENTED MAGNETIC STEEL THICK SHEET EXCELLENT IN MAGNETIC PROPERTY AND FILM CHAR...