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| Effect of improving dephosphorization of molten steel by optimizing slagging in large converters |
| ZHI Jian-guo1,2, WU Wei3, GAO Qi3, XU Tao4, LUO Hai-ming4, ZHANG Xiao-feng2,5 |
1. Baotou Iron and Steel (Group) Co., Ltd., Baotou 014010, Nei Mongol, China;
2. Inner Mongolia Enterprise Key Laboratory of Rare Earth Steel Products Research and Development, Baotou 014010, Nei Mongol, China;
3. Department of Metallurgical Technology Institute, Central Iron and Steel Research Institute, Beijing 100081, China;
4. Rare Earth Steel Sheet Plant Steelmaking Operation Department, Baotou Iron and Steel (Group) Co., Ltd., Baotou 014010, Nei Mongol, China;
5. Technical Center, Baotou Iron and Steel (Group) Co., Ltd., Baotou 014010, Nei Mongol, China |
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Abstract In the face of the problems of slow slagging speed, higher oxygen content of molten steel and iron oxide content of end-point slag, and unstable phosphorus content of molten steel at the end-point of BOF, the slag formation and oxygen supply process of 260 t converter were studied by slag melting measurement, thermodynamic equilibrium calculation and slag mineral phase analysis. The results show that the melting temperature of the slag is 1 330 ℃ at the initial stage of the converter, which is unfavorable for melting the slag in the early stage of the converter; the melting temperature of the final slag is 1 200 ℃, which is not conducive to the maintenance of the converter lining in the late stage of converter blowing; The difference of the phosphorus content between BOF end-point and the phosphorus equilibrium is large, indicating that the kinetic conditions of the BOF end-point are insufficient. The slag contains a high content of free calcium oxide and partially unmelted lime. By improving the order and quantity of slagging addition, strengthening the technical measures of oxygen lance position control and bottom blowing gas stirring at the end-point of BOF, a higher dephosphorization rate at the BOF end-poin and a phosphorus distribution ratio between slag and molten steel can be obtained, and the phosphorus content between slag and molten steel is closer to the equilibrium value; the BOF end-point slag is well developed and the free calcium oxide content is moderate.
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Received: 16 December 2019
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2020, Vol. 55 
