低碳含铝钢20Mn2精炼渣系CaO-SiO2-Al2O3-MgO-CaF2的优化

通过对低碳含铝钢20Mn2精炼过程的取样分析,得出精炼渣的熔化温度偏高,渣中存在大量固相CaO,并导致钢中含有CaO类夹杂物,精炼渣吸附夹杂物能力差. 利用FactSage热力学计算,从渣的低熔点区域控制和渣-钢反应这两个方面对渣系进行研究与优化. 结果表明,CaO/Al2 O3 质量比在1. 5左右添加质量分数为3% CaF2 可以有效降低渣的熔化温度,渣的熔化温度随着CaF2 含量的升高呈现先降低后升高的趋势,MgO的质量分数控制5%左右低熔点区域面积达到最大. 在SiO2 质量分数大于30%区域,钢中氧含量大体上随着CaO/Al2 O3 质量比的增加而降低,在SiO2 的质量分数低于30%区域随着CaO含量的升高而降低,钢中酸溶铝含量在SiO2 含量高的区域随着Al2 O3/SiO2 质量比的增加而升高,在SiO2 含量低的区域随着CaO/SiO2 质量比的增加而增加. 根据热力学分析结果得出合理的渣系范围:CaO 50% ~60%, Al2 O3 20% ~35%, SiO2 5% ~10%, MgO 5% ~8%, CaF2 0~5%. 优化渣系的实验结果表明,优化后渣系熔化温度降低,钢中夹杂物数量、面积和平均尺寸均有明显下降.

Optimization of CaO-SiO2-Al2O3-MgO-CaF2 refining slag in low-carbon and aluminum-containing 20 Mn2 steel

Through analysis of samples taken in the refining process of low carbon and aluminum containing 20Mn2 steel, it was found that the melting point of the refining slag was high, substantial solid CaO and CaO-type inclusions existed in the steel and slag, leading to a decrease in absorption capacity of inclusions in the molten slag. Based on thermodynamic calculations utilizing FactSage software, the slag system was investigated and optimized by integrating the control of low-melting-point regions and reactions between slag and steel. The results show that 3% CaF2 addition can decrease the melting temperature of the slag with CaO/Al2O3 mass ratio around 1. 5, and the melting point of the slag exhibits an initial decline and a subsequent rise with increasing CaF2 content. The largest low-melting-point region is obtained through governing the MgO content in a vicinity of 5%. The oxygen content in the steel decreases with increasing CaO/Al2O3 mass ratio in the region of SiO2 exceeding 30%, and decreases with increasing CaO content in the region of SiO2 lower than 30%. The acid-soluble aluminum content increases with increasing Al2O3/SiO2 mass ratio in the region of high SiO2 content and increasing CaO/SiO2 mass ratio in the region of low SiO2 content. According to results from thermodynamic analysis, the optimized slag can be given as 50% -60% CaO, 20% -35% Al2O3 , 5% -10% SiO2 , 5% -8% MgO, and 0-5% CaF2 . Experi-mental results show that the melting point of the optimized slag declines, and there are apparent decreases in the number, area and mean diameter of inclusions in the steel.