| As a harmful ingredient in most types of steel, phosphorus is an element that must be removed in smelting process. Phosphorus is easely aliquated in grain boundary, and it can markedly debase impact flexibility of steel in low temperature.In this paper with the trait of oxidation dephosphorization and the requirement of ultra-low phosphorus steel in bao steel we have studied three types of dephosphorization slags and effection of technology. Our target is to define which slag is better when used in dephosphorization of low phosphorus steel. In this experiment we learned pipeline steel. Coming from experiment of CaO slag,BaO slag,Na2O slag, we have validated effect when oxygen activity of steel liquid,quantity of slag,basicity are changed. Get dephosphorization result of CaO-CaF2-FetO,BaO-CaF2-FetO,Na2SiO3 slag:(1) CaO-CaF2-FetO slag has low price and easily gotten. Use this slag can get high dephosphorization. In carbon tube furnace average phosphorus content can drop to 37.7×10-4%, and average dephosphorization efficiency is 54.09 % when 60～75%CaO:15～25%CaF2:10～20%FetO slag is used. In induction furnace average phosphorus content can drop to 38.75×10-4%, and average dephosphorization efficiency is 67.3%. So this type of slag is properly used in produce.(2) When 10～20%BaO:50～65%CaO:15～20%CaF2:10%FetO or30～60%BaO:20～55%CaO:15～20%CaF2 slag is used. In carbon tube furnace average phosphorus content can drop to 33.67×10-4%, and average dephosphorization efficiency is 58%. In induction furnace average phosphorus content can drop to 45.8×10-4%, and average dephosphorization efficiency is 62.35%. BaO slag has good dephodphorization efficiency in low oxygen activity.(3) When converter slag to Na2SiO3 is 2:1～4:1. In carbon tube furnace average phosphorus content can drop to 36.7×10-4%, and average dephosphorization efficiency is 49%. In induction furnace average phosphorus content can drop to 51.3×10-4%, and average dephosphorization efficiency is 56.2%. In process of reaction this slag largely volatilizes and losses much.In this paper one kinetics model has been built and validated from experiment. When phosphorus content in steel liquid is under 100×10-4% mass transfer coefficient is about 0.02～0.08cm/s. The limit of reaction is located in mass transfer of phosphorus in steel liquid. Effect of diffuse about PO4 3? in slag has little influence. Some measure can be used to accelerate dephosphorization rate such as stir molten steel,bigger reaction interface.According to experiment in lab we have trialed in steeelmaking factory of Baosteel. From that we see that with selected slag ultra-low phosphorus steel in which phophorus content about 50×10-4% can be smelted by converter tapping—dephosphorization with slag—skim—LF when phosphorus content is about 100×10-4% after converter tapping. |
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