Non-oriented silicon steel

03 Nov 2023
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Non-oriented silicon steel
 

Unoriented silicon steel is a very low carbon ferrosilicon alloy. In the deformed and annealed steel plate, the grains are randomly oriented.

Non-oriented silicon steel (siIiconsteelwithnon - orientedgrain)
Ferrosilicon alloy with very low carbon content. In the deformed and annealed steel plate, the grains are randomly oriented. The silicon content of the alloy is 1.5% ~ 3.0%, or the sum of silicon and aluminum content is 1.8% ~ 4.0%. The products are usually cold-rolled sheets or strips with nominal thicknesses of 0.35 and 0.5mm, mainly used in the manufacture of electric motors and generators.

The content of silicon, aluminum and manganese in steel is controlled in a certain range according to regulations, and the content of carbon, sulfur, nitrogen and oxygen is as low as possible. Different brands have different requirements for the content of these elements. Aluminum increases the strength and hardness of electrical steel and reduces ductility. However, the effect of aluminum on reducing ductility is not as obvious as that of silicon, and the effect is similar to silicon. Therefore, with the increase of the grade, the silicon content is increased to about 3% and no longer changes, and the aluminum content can be gradually increased to 1%. The general grade aluminum content is 0.3% to 0.6%. With the increase of the grade, the content of carbon, sulfur and manganese is further reduced. High grade impurity content is: S<0.002%, C<0.003%, N2<0.002%, O2<0.002%, after annealing without decarbonization, to prevent the formation of internal oxidation layer and internal nitriding layer. In addition, Ti<0.005% and Zr<0.002% are required to prevent the formation of fine TiN, ZrN and TiC, which hinder grain growth.

In the production process, the hot metal is pre-desulfurized, and the secondary desulfurization is done by adding Ca0+CaF: flux or rare earth elements and calcium during bconverter blowing. The boiling molten steel is further desulfurized after being decarburized by vacuum treatment. Ferrosilicon with low content of titanium and zirconium was selected for alloying. The continuous casting was sealed with argon gas and electromagnetically stirred. The billet heat is sent to the hot rolling plant and placed in a slow cooling pit. The casting billets above 350C were put into the heating furnace and heated to 1200±20C, the hot rolling final rolling temperature was 850±20C, and the coiling temperature was 600±20C. The thickness of the hot rolled plate is 2.0 ~ 2.5mm. Steel with a silicon content of more than 2% is generally cold rolled once, normalized at 900 ~ 1050C(1 ~ 3min) before cold rolling, and then cold rolled by 20 high mill. The second cold rolling method can also be used, after the first cold rolling, it is annealed at 830 ~ 870C(1 ~ 3min) in a continuous furnace with 5% ~ 20%H2+N2 atmosphere, and then cold rolled to the finished product thickness by 8% ~ 10% critical deformation. The final annealing is generally rapidly heated to 850 ~ 860C(2 ~ 4min) in a continuous furnace with 20%H2+N2 atmosphere. If you need to decarbonize, it is best to use two-stage annealing, the first section is decarbonized by 800 ~ 850C in a wet atmosphere, and the second section is annealized at a higher temperature for a short time in a dry atmosphere to promote grain growth. When annealing, the tension in the furnace is best controlled below 2.9N/mm, which can reduce the magnetic anisotropy of the steel plate, and the product's vertical and horizontal iron loss (P15) ratio is 1.1 ~ 1.3. After annealing, the steel plate is coated with semi-organic insulating coating. Large motors requiring high interlayer resistance can also be coated with inorganic salt insulation coating.
Non-oriented silicon steelNon-oriented silicon steel
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