Experimental Study On Increasing Productivity Of LF Refining Process

To improve use ratio of refining equipment and productivity, Al-CaO-CaC2 slag system pre-desulfurizing and conditioning agent and CaCO3-MgCO3-CaC2-NaCl-CaCl2 slag system foaming agent are devised in this paper, which is originated from problems about refining periodic time of 200t LF in the northern work area of No.2 steel plant, Anshan New Iron and Steel Ltd. The paper also studies on the effect of refractories on desulfurizing ratios. This is important to the selection of LF refractory in the field.The comparison experiments about Al-CaO-CaC2 slag system pre-desulfurizing and conditioning agents are designed and thermal simulation experiments are carried out in MoSi2 Furnace. Through these experiments, desulfurizing ratios of molten steel are abtained and optimal composition of pre-desulfurizing and conditioning agent is acquired in this experimental condition.The comparison experiments about CaCO3-MgCO3-CaC2-NaCl-CaCl slag system foaming agents are designed which are based on pre-molten refining slag without fluorine. Accoring to foaming relative heights, optimal composition of foaming agent is obtained in this experimental condition.Magnesium-aluminum spinel refractory containting carbon, magnesium-carbon refractory and magnesium oxide refractory are applied in the comparison experiments in which the pre-molten refining slag and non-pre-molten refining slag are used in the experiments, and according to the desulfuring ratios, the proper refractories in LF refining process are decided.The experimental results show:(1) Desulfurizing ratios in molten steel increase at first and then decrease according to increment of Al, CaC2 and CaO contents in pre-desulfurizing and conditioning agents. These show that the contents of Al, CaC2 and CaO all have optimal values.(2) The optimized pre-desulfurizing and conditioning agent is obtained in this experimental condition and its composition is:WAl=33-37%,wCaC2=48-52%,wCaO=13-17%. The optimized pre-desulfurizing and conditioning agent is superior to field slag, which can decrease the oxidative of tap slag significantly, pre-desulfurize before LF process and has minor influence on other elements in molten steel.(3) The optimized foaming agent composition is obtained in this experimental condition:wCaCO3=55-60%,WMgCO3=15-20%,WCaC2=6-8%,wCaCl2=8-9%,wNaCl=9-10%.The optimized foaming agent has higher foaming relative height than field foaming slag. The results also indicate that proper chloride contents in foaming agent can increase foaming relative height.(4) Using optimized pre-desulfurizing and conditioning agent and foaming agent in field experiments, LF refining time has shortend greatly. Refining periodic time decreases from about 60min to about 40min. Productivity has improved efficiently.(5) In the three types refractories, both magnesium-aluminum spinel refractory containting carbon and magnesium-carbon refractory obtain higher desulfurizing ratios. Magnesium oxide refractories has lower desulfurizing ratios. Magnesinm-aluminum spinel refractory containting carbon and magnesium-carbon refractory can lead to recarburization in molten steel, so they are not fit to the production of low-carbon steel.