GCr15轴承钢120 t LF精炼终点CaO-MgO-Al2O3夹杂的特性研究

采用ASPEX自动扫描电子显微鏡夹杂物分析系统，结合热力学理论分析,研究了GCr15轴承钢LF 精炼终点CaO-MgO-Al₂O₃夹杂的形成机理。结果表明,LF精炼开始达到稳定时，钢液中的夹杂物主要以A1₂O₃夹 杂为主，到LF精炼终点时演变成为近似球形的Al-Mg-Ca-(S)类复合夹杂。MgO ? Al₂O₃/CaO ? A1₂O₃/A1₂O₃夹杂的稳定存在区图表明，当钢液中Ca大于1.2x10^-6时,就可使MgO ? A1₂O₃转化为CaO-MgO-Al₂O₃夹杂。精炼过程优先形成MgO ? A1₂O₃夹杂,随后,Ca会与钢液中的MgO -Al₂O₃夹杂发生反应，进而形成CaO-MgO-Al₂O₃复合夹杂。由于在钢液凝固过程中CaS夹杂的析出，因此，最终试样钢中检测到了 CaO-MgO-Al₂O₃-(CaS)复合氧化物夹杂。

Study on Characteristics of CaO-MgO-Al2O3 Inclusions in GCr15 Bearing Steel at 120 t LF Refining

The formation mechanism of CaO-MgO-Al₂O₃ inclusions in GCr15 bearing steel at LF refining end point is studied by ASPEX automatic scanning electron microscope combined with thermodynamic theory analysis. The results show that Al₂O₃ is the main type inclusion in molten steel when the LF refining started to reach stability, and then evolves into an approximately spherical Al-Mg-Ca-( S) type composite inclusion at LF refining end. The stable phase diagram of MgO ? Al₂O₃/CaO ? A1₂O₃/A1₂O₃ shows that MgO ?Al₂O₃ can be transformed into CaO-MgO-Al₂O₃ inclusions when Ca] is greater than 1.2 x 10 ^-6 in molten steel. The MgO ? A1₂O₃ inclusion would be formed firstly in the refining process, afterwards ,the Ca would react with MgO ? A1₂O₃ inclusion to form CaO-MgO-A1₂O₃ composite inclusion. As a result of the precipitation of CaS inclusion in the solidification, therefor the CaO-MgO-Al₂O₃ -(CaS) composite oxide inclusion is detected in the final steel sample.