Impact Mechanisms of Time-Varying Disturbances on Shrinkage Porosity in Investment Casting and Corresponding Control Strategies

Abstract

In investment casting, fluctuations in shell transfer time create temperature variations that impact the filling, solidification, and mechanical properties of the final casting. This study examines the outlet tube, a critical component in aerospace engines, using a combination of numerical simulation and on-site temperature measurement. We analyze the effect of shell transfer time on shell temperature distribution and solidification behavior, with a focus on its correlation with shrinkage porosity defects. Results show that as shell transfer time increased from 0 to 240 seconds, surface temperatures at key shell locations dropped from the preheated 950 ℃ to 776 ℃, leading to a 500% increase in the number of porosity defects and a 284.3% increase in total defect volume. To address this issue, we propose a control strategy to limit shell temperature loss during transfer and optimize the casting process to reduce shrinkage defects. By insulating the shell with cotton and applying sand-filling modeling, we maintained the shell surface temperature at 930°C during the 240-second transfer, reducing porosity defects by 80% and total defect volume by 90%.

Keywords: investment casting, shell transfer time, on-site temperature measurement, numerical simulation, shell temperature loss control strategy