轴承钢LF-VD精炼过程夹杂物行为变化研究

Study on Behavior Change of Inclusions of Bearing Steel during LF-VD Refining Process

采用夹杂物自动扫描分析仪Aspex对轴承钢炉外精炼过程中的非金属夹杂物进行大面积扫描,系统研究了炉外精炼过程钢液纯净度变化,对关键工序进行氧、氮含量分析,同时利用“无水电解”提取各个工序夹杂物,以便观察夹杂物三维形貌,以指导生产实践。研究表明,LF-VD过程,夹杂物经历了Al2O3→MgO·Al2O3→CaO-MgO-Al2O3演变。LF精炼初期,钢液中形成大量Al2O3夹杂物,随着LF精炼地进行,钢液中逐渐形成MgO·Al2O3、钙铝酸盐、CaO-MgO-Al2O3等复合夹杂物,VD真空后,钢液中形成大量CaO-MgO-Al2O3夹杂物。LF精炼初期,钢液中夹杂物数量密度达到16.25个/mm^2,随着LF精炼的进行,夹杂物数量逐渐减少,VD破空后钢液中夹杂物数量密度降低为6.87个/mm^2,随着静搅地进行,钢液中夹杂物数量密度逐渐降低,VD吊包夹杂物数量密度增加,可能是卷渣造成。

Large scale scanning of non-metallic inclusions produced during refining process of bearing steel outside the furnace is carried out with automatic inclusion scanner(Aspex),in order to systematically research the cleanness change of liquid steel during refining process outside the furnace.The contents of oxygen and nitrogen at key processes are also analyzed.The inclusions at different processes are extracted by the method of“non-water electrolytic analysis”,in order to observe their three-dimensional topography,and to guide the production practice.The research results show that during the LF-VD process,the inclusions experienced the evolution progress of Al2O3→MgO·Al2O3→CaO-MgO-Al2O3.At the beginning of LF refining,a large amount of Al2O3 inclusions are formed in the molten steel.Along with the LF refining progress,the composite inclusions of MgO·Al2O3,calcium aluminate,CaO-MgO-Al2O3 are gradually formed in the liquid steel.After VD vacuum treatment,a large amount of CaO-MgO-Al2O3 inclusions are formed in the liquid steel.At the beginning of LF refining,the number density of inclusions in liquid steel reached 16.25/mm 2.The number of inclusions gradually decreased with the progress of LF refining.After the VD system is pressurized,the density of inclusions in the liquid steel decreased to 6.87/mm 2.With static stirring,the density of inclusions in the liquid steel gradually decreases.The density of inclusions in the VD after ladle transportation increases for the possible reason of slag involvement.