中碳铝镇静钢钙处理夹杂物控制的热力学研究

Thermodynamic Research on Medium Carbon Aluminum Killed Steel by Calcium Treatment

从热力学方面分析铝脱氧钢中Al2O3、MgO·Al2O3夹杂物变性机理及夹杂物中CaS合理控制的条件。热力学研究发现T=1 873 K,w[Al]=0.02%时,需要使钢中w[Ca]为20×10-6时,高熔点的Al2O3转变为液态的12CaO·7Al2O3,此时为避免钢中析出CaS,需使钢中的w[S]〈0.008%。T=1 873 K,w[Al]=0.02%时,生成MgO·Al2O3所需要的w[Mg]为（0.3~10）×10-6,但只需钢中钙含量为1×10-6就能将MgO·Al2O3变性为CaO·Al2O3液态夹杂。由于反应时间和MgO·Al2O3尺寸大小不同,钢中形成部分外围为液态钙铝酸盐,内部为MgO·Al2O3的未完全变性的球形夹杂。

The modification mechanism of alumina,MgO·Al2O3spinel and the condition of precipitation of calcium sulfide was thermodynamically analyzed in this paper. Thermodynamic calculations showed that in order to modify the alumina inclusions into liquid 12CaO·7Al2O3,20 ×10- 6content of calcium in steel was needed when the aluminum in steel was 0. 016% at 1 873 K,meanwhile,sulfur content should be no more than 0. 008% to avoid the precipitation of calcium sulfide. When the content of aluminum was 0. 02%,and magnesium required for MgO·Al2O3spinel formation was 0. 3 × 10- 6~ 10 × 10- 6at 1 873 K,and 1 × 10- 6calcium was sufficient to transfer spinel inclusion into liquid complex inclusions. Incompletely modified spheric inclusions where solid MgO·Al2O3covered by liquid spinel would form depending on the reaction time and size of spinel inclusions.