Effect of hollow insulation riser on shrinkage porosity and solidification structure of ingot

The thermal insulation performance of riser is very important to the shrinkage porosity and solidification structure of ingot, but it is difficult to significantly improve due to the limit of thermal conductivity of riser material. A new type of hollow insulation riser was proposed based on the low thermal conductivity of air, which aims to improve the thermal insulation performance of riser. A 14.5-t steel ingot was prepared using the hollow insulation riser, and the casting temperature was 1500 °C. The temperature evolution of the external surface of mold during solidification was measured using an infrared temperature instrument. A numerical model was established to simulate the porosity and solidification structure of ingot. The reliability of numerical simulation was verified by comparing simulation and experimental results. Results show that the insulation performance of the riser can be significantly improved through application of the hollow insulation sleeve. Compared with solid insulation sleeve, the shrinkage cavity depth was decreased and the position of porosity was raised when hollow insulation riser was applied.