The investigation on the middle period dephosphorization in 70t converter

An experimental test is carried out on the 70t converter in Masteel to study the law of middle period dephosphorization in the smelting period. It is found that the dephosphorization rate is slow in the early and middle period of smelting and the content of the final P in steel cannot reach the standard due to the low oxidation of slag. The content of the final P in steel can be controlled within 0.02% by adding ore to the molten bath in the middle period and raising the lance position. The experimental test shows that the dephosphorization can still be achieved by a large margin if appropriate slag conditions are maintained in the middle period when the C and O reactions are strong. By theoretical calculation, it is concluded that the slag content should be controlled between 15 and 23%, and the basicity of slag should be between 2.5 and 2.8 in the middle period of production. Through the observation of experimental slag by SEM, it is found that the limiting factor of dephosphorization in the middle period under the test conditions is that the dephosphorization speed is too slow due to the low oxidation, rather than the solidification of phosphorus.