Study On The Deoxidation And Inclusion Behavior Control In Silicon Steel

The quality of Si-steel is seriously affected by the quantity, scale, type and distribution of non-metallic inclusions. During the casting process, especially during the unsteady casting state such as the start of casting and the ladle change, inclusions in the molten steel is seriously affected by slag entrapment, refractory erosion and re-oxidation by air, so that the cleanliness and the performance of the Si-steel slab is affected.In this paper, the production method of a non-oriented electrical Si-steel from a domestic steel company was taken as a research subject. Through sampling from tundish and slab followed by NOx analyze and bulk sample electrolysis, the content change of oxygen and nitrogen and the change of content, scale, type and source of large-size non-metallic inclusions under both Si-deoxidization and Al-deoxidization method is systematically studied. Under the experiment conditions of this paper, the main conclusions are as follows:1. The content of T.[O] and [N] in head slag and the molten steel in the corresponding tundish were significantly higher than other casting state, indicating the re-oxidation phenomenon in the start of casting process was serious, suggesting the airproof in the start of casting needed improvement to reduce the removal part of the head slag.2. During different casting state, all the content of [N] in the slag were lower than the molten steel in tundish, indicating the shrouded casting between tundish and crystallizer had problems and re-oxidation by air was serious. However, the floating and removal of inclusions in tundish were effective, so that the content of T.[O]. in the slab was significantly lower than the molten steel in tundish.3. The content of T.[O]. and [N] in the Al-deoxidization slag were generally lower than Si-deoxidization slag.4. With Si deoxidization method, almost all of the large-size inclusions in 2 meters’head slag were formed by slag entrapment. As the casting continues,4 meters’head slag and steady state slag began to show Ca-Mg system inclusions formed by refractory erosion, SiO2, Al2O3, and calcium-aluminum silicate.5. With Al deoxidization method, the components of large-size inclusions in during the process of casting starting were silicate inclusion containing K and Na formed by slag entrapment, Ca-Mg system inclusion formed by refractory erosion. During the steady casting state, the entrapment and erosion was suppressed, so the inclusions were mainly Al2O3 inclusions and calcium-aluminum silicate.