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1. (WO2017037019) METHOD FOR PRODUCING A GRAIN-ORIENTED ELECTRICAL STEEL STRIP AND GRAIN-ORIENTED ELECTRICAL STEEL STRIP

Pub. No.:    WO/2017/037019    International Application No.:    PCT/EP2016/070316
Publication Date: Fri Mar 10 00:59:59 CET 2017 International Filing Date: Tue Aug 30 01:59:59 CEST 2016
IPC: C21D 8/12
Applicants: THYSSENKRUPP ELECTRICAL STEEL GMBH
Inventors: HECHT, Christian
LAHN, Ludger
SCHEPERS, Carsten
Title: METHOD FOR PRODUCING A GRAIN-ORIENTED ELECTRICAL STEEL STRIP AND GRAIN-ORIENTED ELECTRICAL STEEL STRIP
Abstract:
The invention relates to a method for producing a grain-oriented electrical steel strip having optimized magnetic properties, wherein a steel, consisting of (in wt%) 2.0 - 4.0% Si, 0.010 - 0.100% C, ≤ 0.065% Al, ≤ 0.02% N, optionally further constituents, and the remainder Fe and unavoidable impurities, is conventionally processed in order to form cold-rolled strip, which is oxidation-/primary-recrystallization-annealed. The obtained cold-rolled strip has an oxide layer, to which an annealing separator layer is applied. In a subsequent high-temperature annealing process, a forsterite layer forms, to which an insulating layer is applied before a final annealing process. According to the invention, after the oxidation/primary-recrystallization annealing process, a spectrum is determined for the oxide layer obtained in said process by means of FTIR, for the peak of which spectrum that is present at 980 cm-1 and that represents the Fe2SiO4 molecules present in the oxide layer the "area (Fe2SiO4)" is determined and for the peak of which spectrum that is present at 1250 cm-1 and that represents the αSiO2 molecules present in the oxide layer the "area (αSiO2)" is determined. Then the composition of the steel or the parameters of the cold rolling, of the oxidation/primary-recrystallization annealing process, or of an optionally performed hot-rolled strip annealing process are set in such a way that the following condition is fulfilled: 0.5 x area (Fe2SiO4) ≤ area (αSiO2) ≤ 2 x area (Fe2SiO4).