| 摘要 |
The invention relates to a process and a plant for making low-alloy silicon steel intended for manufacturing the strips comprised in the construction of high-power transformers. According to the invention, the process takes place in a three-phase arc furnace using iron ores with a Fe content >60% as a starting material, where the oxides within the ore are reduced with metallic Si and Al, followed by an advanced deoxidation , first by diffusion and, further on, by precipitation, when the alloying with Si also takes place, as well as the introduction of the silico-calcium with nitrogen, as an inhibitor, the liquid steel being discharged in a casting ladle where it is subjected to barbotage with argon and conveyed to the continuous casting plant, to obtain ingot slabs which are subsequently heated to temperatures ranging between 1380...1430°C in a continuous discharge heating furnace and rolled into 2 mm-thick strips, then subjected to a normalizing heat treatment, to pickling and to a first cold rolling operation, up to a thickness of 0.7...0.8 mm, followed by an intermediate annealing in reducing atmosphere and a second cold rolling operation, up to a final thickness of 0.23...0.30 mm, and by a secondary recrystallization annealing, at a temperature of 1170°C, in hydrogen atmosphere, and, as a final stage, an electrically insulating varnish of forsterite MgSiOis applied on the strips, at a thickness of 2...5 μ m, to result in a steel composition having 0.002% C and 3.5% Si, at the most, and an oriented-grain texture, with high induction and magnetic permeability values. |
