Method for lowering rephosphorization in semisteel steelmaking

Abstract

The invention relates to a method for lowering rephosphorization in semisteel steelmaking, and belongs to the technical field of steelmaking. The invention aims to solve the technical problems that the slag state is watery and rephosphorization is high during tapping in semisteel steelmaking. The technical scheme of the invention is characterized in that the method for lowering the rephosphorization in semisteel steelmaking is provided. The method comprises the steps that a, converter steelmaking is performed after semisteel is placed in a converter; activated lime with the dose of 20-25kg / t steel, high-magnesium lime with the dose of 30-35kg / t steel and an acid composite slag former with the dose of 8-12kg / t steel are added in the converter while blowing is started; b, after blowing is finished, light-burned magnesian limestone with the dose of 8-10 kg / t steel and steel slags with the dose of 8-10 kg / t steel are added in the converter; and c, slags are baffled, and steel tapping is performed. By adopting the method, final slags of semisteel steelmaking can be effectively densified; the slag tapping amount is reduced; and the aim of lowering rephosphorization is realized.

Description

technical field [0001] The invention belongs to the technical field of steelmaking, and in particular relates to a method for reducing phosphorus return in semi-steelmaking. Background technique [0002] Phosphorus is a harmful element to most steel types. It not only deteriorates the weldability of steel, but also significantly reduces the plasticity and toughness of steel, especially at low temperatures. The impact toughness of steel is significantly reduced, resulting in "cold brittleness" , brittle fracture occurs, so the phosphorus content must be strictly controlled in the steelmaking process. "Returning phosphorus" refers to the phenomenon that phosphorus returns to molten steel from slag. Specifically, in the process of steelmaking, slag is unavoidable when tapping the converter, and the slag contains phosphorus oxides. During the deoxidation and refining process after tapping, the phosphorus oxides in the slag will be reduced to steel, resulting in rephosphorizati...

AI Technical Summary

Problems solved by technology

For semi-steel steelmaking, since the Si content in semi-steel is traces and the C content is lower than that of ordinary molten iron, the heat source for converter steelmaking is insufficient. Therefore, compared with ordinary molten iron steelmaking, semi-steel steelmaking needs to add SiO 2 , FeO and Fe 2 o 3 Composite slag with other substances, more oxygen needs to be supplemented and blown in the later stage of smelting to meet the requirements of the temperature at the end of tapping, resulting in lower C content and higher oxygen activity in molten steel at the end of semi-steel steelmaking compared with ordinary molten iron steelmaking, and a higher slag state. Dilute, resulting in easy slag rolling during the tapping process, so it is difficult to control the slag after tapping, and the phosphorus return is high. At present, there is still a lack of effective technological measures for industrial application