高温镍基合金电渣重熔过程中的Al、Ti成分控制

Control of Al and Ti Contents During Electroslag Remelting of High-Temperature Ni-based Alloys

摘要:

电渣重熔过程中Al和Ti的氧化导致电渣锭轴向成分不均匀，从而对电渣锭的耐腐蚀性能和力学性能产生不利影响。为了控制电渣铸锭中Al和Ti含量的均匀性，需要明确高温电渣重熔过程中Al和Ti含量的变化，并通过优化渣体系比例和冶炼条件来减少合金中Al和Ti的氧化。在现有文献的基础上，以CaF₂-CaO-Al₂O₃-MgO-TiO₂这一低氟渣系和Incoloy825合金为例，综述了电渣重熔过程中Al和Ti元素控制的研究现状。应用离子与分子共存理论（IMCT），结合FactSage软件，总结了渣的热力学和动力学研究方法。讨论了温度和渣成分对合金中平衡Al、Ti含量的影响。基于膜渗透理论，提出了预测合金中Al和Ti含量的动力学模型，得到了电渣过程中Al和Ti含量随时间变化的数学方程式以及渣-金属反应速率的限制方法。确定电渣重熔Incoloy825合金时TiO₂的最佳添加量约为10％。用IMCT和FactSage对渣-金平衡实验结果进行了比较和分析。FactSage计算结果比IMCT计算结果更准确。TiO₂含量越高，计算结果与实验结果之间的偏差越小。

Abstract:

The oxidation of Al and Ti in the electroslag remelting process causes an uneven axial composition of the electroslag ingot, which adversely affects its performance, including corrosion resistance and mechanical properties. To control the uniformity of Al and Ti content in electroslag ingots, it is necessary to clarify the change in Al and Ti content during the high-temperature electroslag remelting and to reduce the oxidation of Al and Ti in the alloy by optimizing the slag system ratio and smelting conditions. The research status of Al and Ti element control in the electroslag remelting process was reviewed based on the existing literature, taking the low-fluorine slag CaF₂-CaO-Al₂O₃-MgO-TiO₂ and Incoloy 825 alloy as examples. The ion and molecular coexistence theory of slag (IMCT) was used along with FactSage software to summarize the thermodynamic and kinetic research methods. The effects of temperature and components of slag on the equilibrium Al and Ti contents in the alloy were discussed. Based on the film-penetration theory, a kinetics model for predicting Al and Ti contents in the alloy was proposed, and the mathematical equation of the Al and Ti contents vs time in the electroslag process and the slag-metal reaction rate-limiting method were obtained. Results show that the optimum TiO₂ addition during the electroslag remelting for Incoloy 825 alloy is determined to be approximately 10%. The slag-metal equilibrium experimental results were compared and analyzed using IMCT and FactSage. It is found that the FactSage calculation results are more accurate than the IMCT calculation results. The higher the TiO₂ content, the smaller the deviation between the calculated and experimental results.