20CrMoH钢精炼过程中T[O]和夹杂物的研究

Study of Total Oxygen Content and Non-metallic Inclusions in 20CrMoH Steel During Refining Process

为优化生产工艺，改变冶炼方法和炉渣组成，进行了齿轮钢20CrMoH生产试验，分析讨论了生产过程钢中的T[O]、低熔点钙铝酸盐非金属夹杂物的形成过程。结果表明，出钢脱氧时加入足够的Al，钢水的T[O]含量降低非常快，当w（FeO）＋w（MnO）≤0.5%时，SiO2已经成为钢水氧化的氧源；选用w（CaO）=55%-60%，w=（Al2O3）35%-40%，w（MgO）≤6%的CaO-Al2O3-MgO渣系精炼，可以得到w（T[O]）=0.0010%的钢水，夹杂物的变化过程和Ca处理时夹杂物的转变过程类似；钢包渣中w（CaO）/w（Al2O3）的比值为1.50-1.65时，能使钢液中的Al2O3夹杂转变为低熔点的钙铝酸盐，得到与钢液Ca处理相同的效果，在RH真空处理后不再需要钙处理。

Industrial experiments of 20CrMoH steel, a typical gear steel, were carried out with new processes and new slags. Total oxygen content of steel was analyzed, as well as the formation mechanism of the calcium aluminates of very low molting point in the molten steel. From the results, several conclusions can be drawn. First, total oxygen content is decreased sharply during tapping after aluminum addition, and SlOE in slag is the main oxygen source when （FeO% 4-MnO%） is lower than 0. 005. Second, with the use of CaO-Al2O3-MgO refining slag of （CaO%） 55-60, （Al2O3%） 35-40, （MgO%）≤6, super-clean molten steel can be produced with total oxygen content of 10^-5. And further, the transformation of the calcium aluminates inclusions in secondary refining is similar to the transformation during calcium treatment. Finally, the transformation of aluminates in the molten steel to low melting point calcium aluminates can be achieved when the CaO/Al2O3 ratio of the slag is controlled between 1.50- 1.65,as for calcium treatment, and Ca-treatment can be eliminated after RH.