低碳低合金钢中CaO-Al_2O_3-SiO_2-MgO系夹杂物熔化温度的控制

Control on melting temperature of CaO-Al_2O_3-SiO_2-MgO inclusions in low carbon low alloy steel

通过FactSage计算分析低合金钢中CaO-Al2O3-SiO2-MgO四元系夹杂物的熔点和低熔点区域的控制范围;并与热丝法试验结果对比发现,在低于1 500℃时,利用FactSage预测该四元夹杂物熔化温度是可行的,计算熔点与热丝法所测结果的偏差小于4%。夹杂物液相区的变化规律为,随着MgO,SiO2和Al2O3含量的增加,夹杂物低熔点区域面积都是先增大后减小;随着CaO含量的增加,夹杂物低熔点区域有2次先增大后减小的变化过程。控制CaO-Al2O3-SiO2-MgO系中w（CaO）为40%~50%,w（Al2O3）在15%~25%之间,w（MgO）为5%~8%。可获得最大范围的低熔点区域。当w（MgO）为8%时,为满足熔化温度≤1 500℃,减少中间包水口结瘤,须控制最佳CaO与Al2O3质量比为1.0~1.6,SiO2质量分数为10%~15%。

The controlling compositions of low melting point inclusions in a CaO-A1203-SiO2-MgO inclusion system in low alloy steel were calculated and analyzed by FactSage. Compared with the experimental result of the hot thermocouple technique, the calculated method is verified to be reliable to predict the melting point of the inclusion system below 1 500 ~C and the relative error is below 4%. The results indicate that with the contents increasing of magnesia, silicon oxide and alumina, the area of low melting point inclusions increases at first and then decreases. However, the area increases at first and then decreases appear twice with the contents increasing of calcium oxide. To obtain the maximum area of low melting point inclusions, the calcium oxide mass fraction should be controlled approximately from 40% to 50%, alumina mass fraction should be controlled between 15% and 25%, and the magnesia mass fraction should be controlled from 5% to 8%. When the MgO content is restricted to 8%, to ensure the melting temperature below 1 500C and reduce the nozzle clogging, mass ratio of CaO to A1203 should be valued in 1.0-1.6, SiO2 mass fraction should be controlled to 10%-15%.