Numerical Simulation of Melt Convection and Macrosegregation of Ti60 Alloy Ingot During the Vacuum Arc Remelting
Vacuum arc remelting(VAR)is one of the most commonly used methods for the production of titanium alloy ingots.Due to the high temperature and opacity of the melting process,it is difficult to experimentally study the fluid flow behavior and macrosegregation during the melting process.Based on this,the VAR melting process of Ti60 high-temperature titanium alloy was studied by numerical simulation method.The effects of melting current and magnetic field stirring intensity on fluid flow behavior and macrosegregation were also discussed.The results show that the molten pool shape changes gradually from"flat"to"V-shaped"when VAR melts titanium alloy.At the end of solidification,the content of Zr elements in the bottom and edges of the ingot is low,and the content in the center and shrinkage cavity is high.The Lorentz force generated by the melting current makes the melt flow counterclockwise,and the larger the melting current,the more intense the melt flow.At the same time,it also leads to more severe macrosegregation at the ingot center and riser.The Lorentz force generated by the stirring magnetic field is applied to the whole molten pool,which not only promotes the flow of meltin the upper part of the molten pool,but also facilitates the flow of melt in the lower part of the molten pool,and also leads to more serious macrosegregation in the ingot center and shrinkage cavity.When there is no stirring magnetic field and the stirring magnetic field is large,the Zr element will produce more serious macrosegregation in the ingot.In order to effectively control the occurrence of macrosegregation defects in VAR melting titanium alloy,small melting current and appropriate stirring intensity should be adopted.
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