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AssigneeThyssenkrupp Acciai Speciali Terni S.p.A.
InventorsStefano Fortunati, Stefano Cicale, Claudia Rocchi, Giuseppe Abbruzzese
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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−1<Iz<1500 cm−1 and Iy=1.9 Fv/r (cm−1), Fv being the volume fraction of second phases stable at temperatures of less than 800° 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° 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° 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.
Process for the production of grain oriented electrical steel strips in which a silicon steel is continuously cast in the form of a strip having a thickness comprised between 1.5 and 4.5 mm, and cold rolled to a final thickness comprised between 1 and 0.15 mm, subjected to a primary recrystallisation annealing and to a further annealing for secondary recrystallisation at a temperature higher than the preceding one, caracterised in that between the steps of casting and of cold rolling second phases are precipitated within the metal matrix, pertaining to at least a class of compounds chosen between sulphides, selenides and nitrides, acting as primary inhibitors, apt to slow down the movement of grain boundaries, said precipitates being so distributed within the matrix to be able to govern and control the grain growth of the primary recrystallisation, and in that between the cold rolling step and the secondary recrystallisation step a further precipitation of nitrides is induced, as secondary inhibitors apt to control, along with said primary inhibitors, the secondary recrystallisation in terms of orientation and dimensions of the grains forming the crystalline structure of the end product.
Process for the production of grain oriented electrical steel strips, in which a silicon steel comprising at least 30 ppm of S or N, at least an element chosen from the group consisting of Al, V, Nb, B, Mn, Mo, Cr, Ni, Co, Cu, Zr, Ta, W and at least an element chosen from the group consisting of Sn, Sb, P, Se, Bi, is continuously cast directly in form of strip having a thickness comprised between 1.5 and 4.5 mm, and cold rolled to a final thickness comprised between 1 and 0.15 mm, said cold rolled strip being then subjected to a primary recrystallisation continuous annealing and to a secondary recrystallisation annealing at a temperature higher than the one of primary recrystallisation, characterised in that the following group of steps is sequentially carried out:
Grain oriented electrical silicon steel strip obtained by direct rolling an as cast strip, characterised in that it comprises at least 30 ppm of S and/or N, atv least an element chosen from the group consisiting in Al, V, Nb, B, Ti, Mn, Mo, Cr, Ni, Co, Cu, Zr, Ta, W and at least an element chosen from the group consisting in Sn, Sb, P, Se, Bi.
Dependencies are inferred from the claim text.