LF-VD冶炼轴承钢的氧化物夹杂变化行为

Change Behavior of Oxide Inclusions in Bearing Steel Produced by LF-VD Process

通过对国内某厂BOF-LF-VD工艺生产的GCr15轴承钢全流程取样,系统研究了GCr15生产过程中大颗粒氧化物夹杂的变化行为。分析各工序氧氮含量的变化,扫描电镜观察夹杂物的形貌、大小,能谱分析仪分析夹杂物成分,钢质纯净度分析仪统计分析夹杂物的数量和当量直径ECD(Equivalent Circular Diameter)。研究表明,该流程可以获得T[O]的平均含量为9×10-4%;LF到站夹杂物基本为Al2O3系并含有少量CaO,LF喂铝后夹杂物中出现MgO,LF精炼过程中CaO含量逐渐升高,VD结束后CaO含量有所降低,MgO含量上升;LF和VD精炼后钢中夹杂物粒径大小和数量都显著下降,同时在大包到中间包之间注流被卷入空气。热力学分析表明夹杂物中的MgO来自钢包中的耐火材料,夹杂物中CaO来自于炉渣中CaO。

The change behavior of oxide inclusions in GCr15 steel produced by BOF-LF-VD process in a domestic factory was systematically studied by sampling in various steps in the production and with different analytical techniques. The content changes of oxygen and nitrogen in every step were analyzed, the morphology and size of oxide inclusions were observed by scanning electron microscopy, the composition of the inclusions was analyzed by spectrum analyzer, the number of the inclusions and Equivalent Circular Diameter （ECD） were statistically analyzed by steel purity analyzer. The results show that BOF-LF-VD process can obtain T[O] content to an average of 9×10^-4%. In LF station inclusions, the main composition is Al2O3 with a small amount of CaO, but after feeding aluminum in LF, MgO appears in inclusions, the content of CaO gradually rises in LF refining process, the content of CaO gradually declines and MgO gradually rises in VD refining process. The particle size and the number of inclusions significantly decrease after LF and VD refining, at the same time, the air is involved in the stream from laddle to tundish. Thermodynamic analysis shows that the MgO in inclusions comes from refractory material of the ladle, and CaO in inclusions comes from the slag.