IF钢非稳态连铸坯洁净度定量分析

Quantitative Research on Cleanliness of Unsteady Casted IF Steel Slabs

通过氧氮分析、定量金相分析及大型夹杂物分析等试验方法,对某钢厂IF钢生产稳态及非稳态浇注的连铸坯进行了对比研究。结果表明,稳态坯w(T[O])和w(N)的平均含量分别为11×10-6和18×10-6,显微夹杂物含量平均为4.0个/mm2,大型夹杂物含量为2.10 mg/kg,洁净度较高。非稳态浇注对连铸坯洁净度有较大程度的危害。中间包开浇头坯受到较为严重的空气二次氧化,洁净度最差;钢包交换和更换浸入式水口时受到的空气二次氧化较小,但是钢渣反应和卷渣行为较为严重;尾坯洁净度受到空气二次氧化和卷渣的共同影响。连铸坯显微夹杂物含量分布,沿铸坯宽度方向一般1/4处最多,1/2处最少;沿铸坯厚度方向内外弧附近明显高于连铸坯中心部位。

By means of T[O] and [N]measurement,metallographic observation and sample-electrolyzing,the cleanness of normal slabs and unsteady cast slabs of IF steel produced in a plant had been compared. Normal slabs have very high cleanness,where the w( T[O]) is 11 × 10^(-6),w( N) is 18 × 10^(-6) and the mean number density of micro inclusions is 4. 0 per mm2,the fraction of inclusions over 50 μm is 2.10 mg/kg. But the unsteady continuous cast slabs contain much more inclusions. The cleanness of the first slab is worst because of the serious re-oxidation. The slabs were polluted by the slag or mold powder due to the lever fluctuation in the tudish or the mold while changing ladle or SEN. The last slab of the tudish was polluted both by the air re-oxidation and the slag entrapments. The distribution of micro inclusions shows that the maximum number of inclusion is found at the 1/4 width of the slab,while 1/2 width appears minimum amount of inclusion. Along the thickness direction,the number of inclusion near the inner and outer surfaces of the slab are obviously higher than those of central area.