钙处理时机对LF-RH精炼过程Al_(2)O_(3)基夹杂物的影响

Effect of calcium treatment time on Al_(2)O_(3) based inclusions during LF-RH refining process

为研究LF-RH精炼工艺生产Q690钢时不同钙处理时机下夹杂物特征的变化,开展工业试验对RH精炼前后钙处理炉次取样进行定量分析对比。钙处理后夹杂物中CaO质量分数持续增加,CaS质量分数瞬态增加,夹杂物熔点降低。RH精炼前钙处理炉次中,RH精炼过程夹杂物的成分接近低熔点区,结束时夹杂物数量密度和面积分数分别为15个/mm^(2)和0.01%。RH精炼后钙处理炉次中,RH精炼过程夹杂物依旧为高熔点Al_(2)O_(3)-MgO类型,结束时夹杂物数量密度和面积分数分别降至1个/mm^(2)和0.002 5%。RH精炼前钙处理会使RH精炼过程夹杂物熔点以及夹杂物与钢液间的接触角降低,导致夹杂物去除驱动力降低,从而抑制夹杂物的去除。因此LF-RH精炼工艺生产铝脱氧钢时,为提高精炼过程钢中非金属夹杂物的去除效率,应在RH精炼后进行钙处理操作。

In order to study the characteristics of inclusions in Q690 steel produced by LF-RH refining process under different calcium treatment time, industrial experiments were carried out to quantitatively investigate and compare the samples of calcium treatment before and after RH. After calcium treatment, the content of CaO in inclusions increased continuously, the content of CaS increased instantaneously, and the melting point of inclusions decreased. In the heat with calcium treatment performed before RH refining, the composition of inclusions during RH refining were close to the low melting point zone, and the number density and area fraction of inclusions after RH refining were 15 per aquare millimeter and 0.01%, respectively. While in the heat of calcium treatment after RH refining, the inclusions during RH refining were still high-melting-point Al_(2)O_(3)-MgO type, and after RH refining their number density and area fraction were reduced to 1 per aquare millimeter and 0.002 5%, respectively. Calcium treatment before RH refining will reduce the melting point of inclusions and the contact angle between inclusions and molten steel, leading to the decrease of driving force for inclusion removal, thus inhibiting the removal of inclusions. Therefore, for the production of Al-killed steel by LF-RH refining process, in order to improve the removal efficiency of non-metallic inclusions in steel during refining process, calcium treatment should be carried out after RH refining.