Time-varying disturbances of temperature field in investment casting and corresponding shrinkage defects control methods

Disturbances in the temperature field are a key factor affecting the quality of investment castings. During production, the shell is transferred from the preheating furnace to the pouring furnace, experiencing significant changes in thermal conditions, which lead to disturbances in the shell's temperature field. Fluctuations in temperature during this transfer process can greatly impact the final casting quality. This study combines numerical simulation and on-site temperature measurements to analyze how time-varying disturbances in the shell temperature field contribute to the formation of shrinkage defects. Results show that as shell transfer time increased from 0 to 240 s, surface temperatures at key shell locations dropped from the preheated 950 °C–776 °C, leading to a 512.34% increase in the number of shrinkage defects and a 285.47% increase in total defect volume. By implementing the time-varying disturbance control method of insulating the shell with cotton and applying sand-filling modeling, the shell's surface temperature can be maintained above 930 °C during the 240s transfer process, resulting in a reduction of 83.67% in shrinkage defects and 90.18% in total defect volume. This study offers a new approach to reducing disturbances in process parameters and preventing casting defects during the casting process. It also proposes innovative solutions to address long-standing quality control challenges in shell mold casting.