Abstract:Fluent software was used to simulate the interaction among the temperature field, flow field, and solute field in the vacuum arc remelting process of TC4 titanium alloy. The effects of three process parameters (smelting rate, upper surface temperature of the ingot, and cooling intensity), which are directly related to the ingot, on the ingot macrosegregation were studied. Results show that under different smelting conditions, the radial macrosegregation of Fe element shows a bell-shaped distribution at the ingot height of 1000 mm, i.e., the core of ingot presents the positive macrosegregation whereas the surface area presents the negative macrosegregation, and the degree of negative macrosegregation is greater than that of the positive macrosegregation. The effect of smelting rates on the temperature field and macrosegregation of the ingot is the most obvious: with increasing the smelting rate from 0.15 mm/s to 0.18 mm/s, the ingot height to reach the stable melting stage is increased from 1200 mm to 1600 mm, and the depth of the molten pool is increased from 494 mm to 738 mm. In the area within the distance of 130 mm from the ingot center, the macrosegregation is decreased with increasing the smelting rate, and the maximum value is 3.36% when the smelting rate is 0.15 mm/s. In the area beyond the distance of 295 mm from the ingot center, the macrosegregation is increased with increasing the smelting rate, and the maximum value is 6.23% when the smelting rate is 0.21 mm/s. The effect of upper surface temperature and cooling intensity on macrosegregation and molten pool depth is not obvious. Through the orthogonal analysis, the influence degree of three main process parameters on macrosegregation is as follows: smelting rate>cooling intensity>ingot upper surface temperature. The optimal conditions are smelting rate of 0.15 mm/s, ingot upper surface temperature of 2179 K, and cooling intensity of 500 (bottom)/1000 (side) W·m-2·K-1.