Modelling the Oxygen Content of Titanium During Deoxidation in the Pressure Electroslag Remelting (PESR) Process

摘要

Due to the combination of high strength, low density and good corrosion resistance, titanium alloys are the material of choice in the aeronautics and medical industry. However, the use of titanium and its alloys is limited to high performance applications as a result of the high production costs. Therefore, a new production route for titanium alloys is under investigation at IME, RWTH Aachen University. Main idea is the synthesis of a TiAlV master alloy by aluminothermic reduction (ATR) of rutile ore. This alloy is then mixed with Ti-sponge in order to obtain a Ti-6Al-4V ratio and subsequently processed in a pressure electroslag remelting (PESR) furnace. In this PESR step, metallic calcium is added to the flux as a deoxidant to decrease the oxygen level of the remelted material. Since strict specifications regarding chemical homogeneity must be met the deoxidation step has to be controlled carefully in order to achieve a constant oxygen level and hence uniform mechanical properties. Since on-line measurements of the slag and metal phase are not feasible, a theoretical approach is made in order to describe the reaction rates in the PESR process. This paper presents a model for the kinetic aspects of deoxidation at the metal-slag interfaces. The calculated rate of deoxidation is presented and validated with results of experimental trials.