精炼渣成分与轴承钢夹杂物类型关系热力学分析

针对轴承钢中钙铝酸盐大型夹杂物的控制问题,通过计算GCr15轴承钢中尖晶石MgO·Al2 O3、钙的铝酸盐CaO·6Al2 O3夹杂物生成热力学,分析精炼渣成分与夹杂物类型之间的定量关系.结果表明：当钢水中含有质量分数0.10×10-6的溶解钙Ca]时,只要溶解镁Mg]质量分数小于10×10-6,MgO·Al2O3就会被Ca]还原成 CaO·6Al2O3；当精炼渣碱度为7.04,(MgO)质量分数为1.38%时,钢水中溶解Mg]质量分数比临界Mg]质量分数低56%,夹杂物以尺寸大于10μm的CaO-Al2O3系复合夹杂为主；当精炼渣碱度为3.75,(MgO)质量分数3.14%时,钢水中溶解Mg]质量分数比临界Mg]质量分数低14%,夹杂物以尺寸小于8μm的MnS包裹MgO·Al2 O3复合夹杂为主；当精炼渣钙铝比C/A为1.8~2.0时,控制精炼渣碱度R为4.5~5.5,(MgO)质量分数为3%~5%,即能使钢中MgO·Al2O3保持稳定而不转变为CaO·6Al2O3.

Thermodynamic analysis of the relationship between refining slag composition and inclusion type in bearing steel

In order to control large calcium aluminate inclusions in bearing steel, the quantitative relationship between refining slag composition and inclusion type is discussed by calculating the formation thermodynamics of MgO·Al2 O3 and CaO·6Al2 O3 in this paper. The results show that MgO·Al2 O3 can be reduced to CaO·6Al2 O3 by dissolved aluminum with 0. 10í10 -6 Ca and less than 10í10 -6 Mg in molten steel. When the basicity of refining slag is 7. 04 and the content of ( MgO) is 1. 38%, the content of Mg in liq-uid steel is about 56% lower than the critical value, and the main inclusions is CaO-Al2 O3 , whose dimension is larger than 10μm. As the basicity of refining slag is 3. 75 and the content of ( MgO) is 3. 14%, the content of Mg in liquid steel is about 14% lower than the critical value, and the main inclusions is MgO·Al2 O3 surrounded by MnS, whose dimension is less than 8μm. Under the condition that the Ca/Al ratio is between 1. 8 and 2. 0, MgO·Al2 O3 inclusions can be kept stable rather than reduced to CaO·6Al2 O3 when the basicity of refining slag is between 4. 5 and 5. 5 and the content of MgO is between 3% and 5%.