Acciai Speciali Terni, S.p.a.

Centro Sviluppo Materiali S.p.a.

Thyssenkrupp Acciai Speciali Terni S.p.a.

Acciali Speciali Terni S.p.a.

Centro Sviluppo Material S.p.a.

Rina Consulting—centro Sviluppo Materiali S.p.a.

Centro Svilippo Materiali S.p.a.

Stefano Fortunati

Giuseppe Abbruzzese

Stefano Cicale'

Stefano Cicale′

Stefano Cicale&prime;

Mario Tului

Claudia Rocchi

Paolo Marini

Luca Risso

Stefano Cicale

Susanna Matera

Cicale' Stefano

A process for the production of grain non-oriented electric Fe&#x2014;Si steel strips, with excellent electric and/or magnetic characteristics to be used preferably for construction of electrical machines is disclosed.

Process for the production of grain non-oriented electric steel strip, with an high degree of cold reduction

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

The present invention has as objective a procedure for the oriented-grain magnetic sheet that provides particular operative hot rolling mill conditions of silicon steel slabs, by means which it is possible to highly contain the heterogeneities of hot rolled sheet re-crystallization. The use of these operative conditions permits to reduce the growing tendency of the crystallized grain during the annealing of the sheets at a final thickness that precedes the secondary oriented re-crystallization. Contemporarily, the particular operational conditions of hot rolling mill according to the invention permit a fine precipitation of secondary phases useful to the control of the grain growing, starting from a quantity of sulphur (S) and nitrogen (N) in matrix lower than corresponding provided by the conventional technologies and consequently disposable in metallic solid solution before the rolling after the heating of the slabs at temperature values lower than 1300&#xb0; C.

Process for the production of grain-oriented magnetic sheets

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 a grain oriented magnetic strip, made of steel containing 2.3 to 5.0% of silicon, obtained by producing a hot-rolled sheet containing a distribution of second phases capable of controlling the secondary recrystallization by means of a two-step hot-rolling with an intermediate annealing, and by changing it into the final product.

Process for the production of a grain oriented magnetic strip

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.

Process for the production of grain oriented electrical steel strips

Process for the production of oriented grain electrical steel strips, in which a silicon steel, comprising at least 30 ppm of S, is directly cast as strip 1.5-4.5 mm thick and cold rolled to a final thickness of between 1.0 and 0.15 mm; characterised by the following staged: Cooling and deformation of the solidified strip to obtain a second phases distribution in which 600 cm&#x3c;Iz&#x3c;1500 cmand Iy=1.9 Fv/r (cm), Fv being the volume fraction of second phases stable at temperatures of less than 800&#xb0; C., and r being the precipitates mean radius, in cm; Hot rolling between solidification and coiling of the strip at a temperature of not less than 750&#xb0; C., with a reduction ratio of between 15 and 60%; Cold rolling with reduction ratio of 60-92%; Cold rolled strip annealing at 750-1100&#xb0; C., with increase of the nitrogen content of at least 30 ppm with respect to the initial composition at the strip core, in nitriding atmosphere.

By forming, after the annealing of the continuously cast body, a limited number of precipitates apt to the control of the grain growth, and utilising a cold rolling reduction ratio of at least 70%, it is possible to obtain in a subsequent step of continuous nitriding the direct formation of nitrides useful for the grain growth control and subsequently, still in a continuous treatment, to at least start the oriented secondary recrystallization.

A process for the production of oriented-grain electrical steel sheet with high magnetic characteristics, and more precisely a process in which the slab obtained from continuous casting is continuously nitrided by a reaction between aluminium and nitrogen is described. Amount, size and distribution of precipitates are controlled, enabling a high-temperature continuous heat treatment during which the primary-recrystallization and a high-temperature nitriding are realized.

Process for the production of oriented-grain electrical steel sheet with high magnetic characteristics

During the treatment of electrical steel, a careful combination of heat treatment of the slab with a specific primary recrystallization and nitriding treatment allows for control of the distribution, quantity and dimensions of precipitates in order to obtain a homogeneous precipitation of nitrogen compounds by direct reaction of the absorbed nitrogen with aluminum during the nitriding step.

Process for the treatment of grain oriented silicon steel

The production of grain-oriented electrical steel sheets is disclosed wherein grain growth in the steel is inhibited by a method comprising the regulation of the content of sulfur and manganese in the steel strp and the cold rolled strip is continuously nitrided at high temperature.

Process for the inhibition control in the production of grain-oriented electrical sheets

In the production of grain-oriented electrical steel strip, the grain growth inhibition is controlled by balancing the copper, aluminum and carbonium content in order to control the type and quantity of precipitated second phases and obtain optimum grain dimensions during the decarburization annealing. This is done by using a continuous high-temperature thermal treatment in which nitrogen is diffused into the steel strip and aluminum is directly precipitated as aluminum nitride which controls the grain orientation of the final product.

A process for the production of grain oriented silicon steel sheet which provides an optimization of the production of conventional, grain oriented silicon steel strips, by the use of an appropriate synergistic combination of the composition levels of some elements and appropriate treatments which result in the control of the presence and type of inhibitors, and by so doing, controlling the primary-recrystallization grain size.

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Rome, Italy

Stefano Fortunati