Centro Sperimentale Metallurgico S.p.a.

Terni Societa Per L'industria E L'elettricita S.p.a.

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Roberto Ricci Bitti

Edmondo G Marianeschi

Mario Barisoni

Massimo Barteri

Pietro Brozzo

Paolo Marini

Carlo Borgianni

Sandro C Basevi

An annealing separator for use on grain-oriented silicon steel strip comprises a magnesium oxide base composition containing rare earth metal oxides. The rare earth metal oxides are present in an amount of 0.8 to 30% by weight of the composition; but in the lower range of 0.8 to 5% by weight, and preferably up to 7% by weight, the oxides have a particle size of less than 325 mesh, and a fraction of 35-55% by weight smaller than 500 mesh. Alkali metal silicate may be present in an amount 5 to 45% by weight. Strip coated with annealing separator of the invention is characterized in that the coating is almost totally free of surface cavities, in that the denitriding and desulfuring rates are greatly accelerated, in that the surface resistivity of the coating is substantially increased, and in that the coating adheres more strongly to the strip.

Annealing separator and steel sheet coated with same

A process for the production of oriented-grain high magnetic permeability steel sheet including the steps of continuously casting a steel slab haing a weight % composition within the range of 2.5-3.5 Si, 0.01-0.04 S, less than 0.07 C, less than 0.15 Mn, and an acid-soluble aluminum in an amount between 0.01 and 0.05, at a feed rate ranging from 700 to 1000 kg/minute, into an ingot mold of a length over 1200 mm and cooling it in said ingot mold with a quantity of water ranging from 2.8 to 4 m.sup.3 per ton of steel; heating the slab so obtained to 1300.degree.-1400.degree. C and immediately thereafter hot-rolling it to a thickness in the range between 2 and 3.1 mm, annealing the strip so obtained at a temperature in the range between 1050.degree. and 1150.degree. C, keeping it at this temperature for a duration between 5 and 30 seconds; cooling it at any desired cooling rate to 750.degree.-850.degree. C at a temperature at which austenite is still present in it; keeping the strip at this temperature for a duration ranging from 30 to 200 seconds; and finally quenching it from the initial quenching temperature of 400.degree. C at a cooling rate of between 10.degree. C/second and 100.degree. C/second; cold-rolling the strip so obtained with a reduction rate ranging from 80 to 90% and subjecting it finally to the decarburization and recrystallization annealing operations as well as to other final anneals.

Method for the production of high-permeability magnetic steel

Low carbon silicon-aluminum single-oriented steel sheet having high magnetic induction is produced by hot rolling at 1370.degree.-1430.degree.C., annealing from 10 to 60 seconds at 1050 to 1170.degree.C., slow cooling to 700.degree.-900.degree.C., quenching from 700.degree.-900.degree.C., cold rolling with a reduction in thickness of 80 to 90%, recrystallization and decarburization annealing in wet hydrogen from 780.degree. to 870.degree.C. for 2 minutes, and final annealing at 1200.degree.C. in a mixture of 10-50% hydrogen and 50-90% nitrogen. Cold rolling can be effected in two stages, the first stage to reduce the thickness by 20 to 50% followed by annealing at 700.degree. to 900.degree.C., quenching and final cold rolling with a reduction in thickness of 80 to 90%. The preferred temperature range prior to quenching, for one-step cold rolling, is 750.degree. to 850.degree.C.; and for two-step cold rolling, the first quench is preferably from a temperature of 750.degree. to 850.degree. C. and the second quench preferably from a temperature of 850.degree. to 900.degree.C.

Process for manufacturing silicon-aluminum steel sheet with oriented

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Lanuvio (Rome), Italy

Roberto Ricci Bitti