Thyssenkrupp Acciai Speciali Terni S.p.a.

Centro Sviluppo Materiali S.p.a.

Stefano Cicale′

Stefano Fortunati

Giuseppe Abbruzzese

Claudia Rocchi

Process for the production of grain-oriented Fe&#x2014;Si sheets having excellent magnetic characteristics to be used for construction of electrical devices wherein the thickness of hot rolled strip (_&#x3e;3.5 mm) and the total cold deformation rate (90-98%) are higher than known processes, and wherein hot rolled strip annealing before cold rolling is not scheduled.

Process for the production of grain-oriented magnetic sheet with a high level of cold reduction

A process for producing grain oriented magnetic sheets by subjecting a steel slab &#x2266;100 mm, containing 2.5-3.5% si, to the following operations: optional first heating, to a temperature T1&#x2266;1250&#xb0; C.; first rough hot-rolling at T2 between 900 and 1200&#xb0; C., the reduction ratio (% Rid) being at least 80% in the absence of a subsequent heating or, in the presence of a subsequent heating to T3&#x2266;1300&#xb0; C., at least 60% determined by % Rid=80&#x2212;(T3&#x2212;T2)/5; second finishing hot-rolling at T4&#x3c;1300&#xb0; C. to a rolled-section thickness of 1.5 3.0 mm; cold-rolling, in one or more stages with optional intermediate annealing and with a cold reduction ratio &#x2267;60% applied in the last stage; primary recrystallization annealing, optionally in a decarburizing atmosphere; second recrystallization annealing.

Process for the production of grain-oriented magnetic sheet starting from thin slab

A process for the production of electrical steel strips, in which a strip is directly cast from molten steel and contains alloy elements apt to generate a precipitation of sulphides and/or nitrides apt to inhibit the grain growth. The strip is hot rolled in-line with the casting operation at a temperature between 1250 and 1000&#xb0; C., and in which the strip is coiled after hot rolling at a temperature of less than 780&#xb0; C. if sulphides are utilized, or at a temperature of less than 600&#xb0; C. if nitrides, or nitrides plus sulphides, are utilized.

Process for the production of grain oriented electrical steel

In the production of electrical steel strips, a special islab-reheating treatment before hot rolling is carried out so that the maximum temperature within the furnace is reached by the slab well before its extraction from the furnace. During the heating stage and performance at the highest temperatures of the thermal cycle, second phase particles are dissolved and segregated elements are distributed in the metallic matrix, while during cooling and temperature equalising steps of the slab in the furnace a controlled amount of small second phases particles are more homogeneously re-precipitated from the metallic matrix. Differently from all the conventional processes for the production of electrical steels, the slab reheating furnace become a site in which it is performed the precipitation of a controlled amount of second phases particles for the necessary grain growth control during the successive process steps.

Process for the control of inhibitors distribution in the production of grain oriented electrical steel strips

A process for the production of grain oriented electrical Fe-Si strips in which a Si-containing alloy is directly cast as a strip between 2.5&#x2013;5.0 mm thick and cold rolled in one stage, or in more stages with intermediate annealing, to a final thickness of between 0.15&#x2013;1.0 mm. The strip is then continuously annealed to carry out the primary recrystallization and then annealed to carry out the oriented secondary recrystallization. The process further includes that after solidification of the strip, and before its coiling, a phase transformation from Ferrite to Austenite is induced into the metal matrix for a volume fraction between 25&#x2013;60%, obtained by controlling the alloy composition so that the Austenite fraction is allowed within the stability equilibrium between the two phases. The strip is then deformed by rolling in-line with the casting step to obtain a deformation higher than 20% in the temperature interval 1000&#x2013;1300&#xb0; C.

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Rome, Italy

Stefano Cicale′