Patent ID: 7501028

Claim:
Method for producing a non-grain oriented magnetic steel strip or non-grain oriented magnetic steel sheet, comprising the following steps: casting a steel which, in addition to iron, contains unavoidable impurities (in weight %) C: <0.005%, Mn: ≦1.0%, P: <0.8%, Al: <1% and Si providing that 1.4%<% Si+2% Al<2.5% (where % Si=Si content and % Al=Al content) to form a fabricated material, processing the fabricated material to form a hot strip in a hot rolling process at hot rolling temperatures which, starting from ≦1,300° C., are adjusted in such a way that with substantially complete exclusion of a purely austenitic structure (γ phase) a first temperature range is passed through in which a processed steel has an austenite/ferrite dual phase multi-structure (α, γ multi-phases), so the magnetic steel strip or magnetic steel sheet, after a surface treatment including etching, cold rolling and annealing of the hot strip obtained after the hot rolling process, has a magnetic polarisation J 2500 ≧1.74 T, measured in a longitudinal direction of the strip or sheet and at a magnetic field strength of 2,500 A/m and a value P 1.5 (50) of magnetic losses of <4.5 W/kg, measured in the longitudinal direction of the strip at J=1.5 T and a frequency f=50 Hz, wherein a span, A T , of a second temperature range within which the processed steel has the purely austenitic structure (γ phase) is less than 50° C., and wherein temperature during the hot rolling process is controlled while avoiding the span, A T , of the second temperature range.