含硫齿轮钢中(CaO)_(x)(Al_(2)O_(3))_(y)和CaS的形成机理与控制

FORMATION AND CONTROL OF(CaO)_(x)(Al_(2)O_(3))_(y) AND CAS INCLUSIONS IN SULFUR-CONTAINING GEAR STEEL

针对含硫钢中的CaS类夹杂物易造成水口堵塞问题,对20CrMnTiS钢中存在的钙铝酸盐夹杂物(CaO)_(x)(Al_(2)O_(3))_(y)及CaS的生成条件分别进行了热力学和动力学分析。结果表明:20CrMnTiS在1600℃下进行钙处理,当钢中[Al]s为0.02%时,需将Ca控制在0.0039%~0.010%;鉴于Al_(2)O_(3)夹杂物的变性动力学分析,钙处理前钢中的Al_(2)O_(3)夹杂物不宜过大,粒径最佳尺寸≤1μm,且喂硫线之前,应给予充分的钙处理时间,使Al_(2)O_(3)夹杂物完全变性为钙铝酸盐夹杂物(12CaO·7Al_(2)O_(3))。含硫齿轮钢合理的精炼工艺为:铁水预处理→转炉→LF精炼(钙处理)→RH真空脱气→软吹(软吹中后期喂硫线)→方坯连铸。

For the CaS inclusion in sulfur-containing steel is easy to cause nozzle blockage,the formation conditions of calcium aluminate inclusions(CaO)_(x)(Al_(2)O_(3))_(y)and CaS in 20CrMnTiS steel were analyzed by thermodynamics and kinetics.The results show that when the[Al]s is 0.02%,the Ca is required to be controlled at 0.0039%~0.010%;based on the denaturation kinetics of Al_(2)O_(3)inclusion,the Al_(2)O_(3) inclusion should not be too large before calcium treatment,and the particle size should be≤1μm;and the sufficient calcium treatment shall be given full time before sulphur wire feeding to completely denature Al_(2)O_(3)inclusions into calcium aluminate inclusions(12CaO·7Al_(2)O_(3)).Therefore,the reasonable refining process of gear steel containing S is:hot metal pretreatment→converter→LF process(calcium treatment at the end of LF process)→RH process→soft blowing(sulfur wire-feeding at mid-late period of soft blowing)→billet continuous casting.