RH炉脱硫过程特征热力学分析

Thermal dynamic analysis of RH de-sulphur process for silicon steel

在硅钢RH炉精炼过程脱硫实践中发现,RH精炼炉中投入一定量脱硫剂,可以起到脱硫作用。但在[Al]、[Si]含量较高的钢种,没有投入脱硫剂也有脱硫效果。另外,RH炉脱氧前也有一定的脱硫效果,RH炉结束的硫含量一般都要比中间包内硫含量要高。通过热力学理论计算发现,RH炉精炼过程脱硫可以分为两个阶段:第一阶段是钢水脱氧前,钢水中[C]和[S]反应生成CS气体,有较弱的脱硫效果;第二阶段是脱氧后脱硫阶段,钢-渣扩散脱硫、钢水中[Si]和[S]反应生成SiS气体和钢水中[S]、[Al]、[Si]和[Ca]相互作用最终生成CaS。钢水中较高的[Al]和[Si]含量对第二阶段脱硫效果有较大的正向影响。进一步的,转炉结束前CS、SiS气体的生成使得铁水[C]元素有一定的脱硫作用。CS气体在转炉持续供氧过程和铁水裸露在空气中时,被氧气氧化生成SO_(2)气体。CaO-CaF_(2)系RH炉用脱硫剂中的CO_(2)组分能够氧化钢水中的[Al]、[Si]等合金元素,同时造成钢水增碳。

The practice during RH de-sulphur process of silicon steel observed that de-sulphur effect not only happened by flux addition but also without flux when higher[Al]and[Si]inside the molten steel.Besides,de-sulphur was proved before deoxidation time to time.The last odd phenomenon was the decreasing sulphur content from RH end to tundish.Thermal dynamic calculation helped to find that the RH de-sulphur process would be divided to two stages–before deoxidation and after deoxidation.CS gas was generated by weak reaction between[C]and[S]in the first stage;in steel-slag reaction,SiS gas was generated by[S]and[Si],and complex reactions with[S],[Al],[Si]and[Ca]was conduct in the second stage.Consequently higher contents of[Al]and[Si]played big positive roles in the second stage.Furtherly,gases of CS and SiS formation inside the liquid metal before endpoint of converter bringed some of sulphur out,and then the CS gas would mix with oxygen to generate SO_(2) when meeting with the continous oxygen supplied in converter and the air on the surface of molten iron.CO_(2) component in the flux would be bad at carbon pickup control and alloy yield due to reactions with alloy elements as[Al],[Si].