超低氧齿轮钢28MnCr5中镁铝尖晶石夹杂物的控制

利用FactSage软件对28MnCr5钢液和镁铝尖晶石夹杂物的平衡反应进行了分析,当wAl]在0.02%~0.04%之间,wMg](0.39~0.42)×10-6的临界范围时开始生成镁铝尖晶石。计算发现:在现有28MnCr5钢精炼工艺条件下,钢液中会不可避免生成镁铝尖晶石夹杂物。当钢液wMg]8.5×10-6时,加入钙不能使其转变成低熔点液态夹杂物;而当钢液wMg]小于此值时,增加wCa]时,夹杂物按照"镁铝尖晶石→CaO-Al2O3-MgO系液态夹杂物→CaO"路径转变,钢液wCa]增加至3×10-6左右时均能将其转化为CaO-Al2O3-MgO系液态夹杂物。计算表明,精炼渣还原提供的Ca]不能使28MnCr5钢中镁铝尖晶石夹杂物完全变性,须采用向钢液中喂钙线等手段来提高钢液中的钙含量。

Control of magnesia-alumina spinel inclusions in the ultra-low-oxygen gear steel 28MnCr5

The equilibrium reaction between the 28MnCr5 molten steel and the magnesia-alumina spinel inclusions was investigated by software FactSage. It is concluded that the critical w??Mg?? increases from 0. 39??10-6 to 0. 42??10-6 with the w??Al?? ranging from 0. 02% to 0. 04%, which makes the spinel inclusions form in molten steel. It is found that the formation of spinel inclusions in 28MnCr5 is unavoidable in the present refining process. The calculation results show that the spinel inclusions can not be transformed into the low-melting-point liquid inclusions when w??Mg???8. 5??10-6. When w??Mg?? is less than that, the spinel inclusions can be transformed according to the route ??spinel??CaO-Al2O3-MgO liquid inclusions??CaO?? with the increasing w??Ca??. The critical w??Ca?? is 3??10-6 which can transform spinel inclusions into liquid inclusions completely. According to the calculation results, the calcium reduced from refining slag is not enough to make spinel inclusions transformed completely. It is necessary to increase w??Ca?? by application of calcium wire feeding process.