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(11) | EP 0 390 142 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Process for producing grain-oriented electrical steel sheet having high magnetic flux density |
| (57) A process for producing a grain-oriented electrical steel sheet having a high magnetic
flux density, comprising the steps of: heating a steel slab comprising 1.8 to 4.8
wt% Si, 0.012 to 0.050 wt% acid-soluble Al, 0.010 wt% or less N, and the balance
consisting of Fe and unavoidable impurities, to a temperature for hot rolling; hot-rolling
the heated slab to form a hot-rolled strip; cold-rolling the hot-rolled strip to a
final product sheet thickness at a final cold rolling reduction of 80% or more by
a single step of cold rolling or by two or more steps of cold rolling with an intermediate
annealing step inserted therebetween; primary-recrystallization-annealing the cold-rolled
strip; final-annealing the primary-recrystallization-annealed strip so that secondary-recrystallized
grains substantially completely grow up in a temperature region of from 1000 to 1100°C
and then purification is effected above 1100°C; and subjecting the primary-recrystallization-annealed
steel strip to a nitriding treatment before a secondary recrystallization occurs during
the final annealing. |