Enhancement of upsetting technology for minimizing internal defects in heavy ingot casting: simulation, optimization, and experimental validation

Abstract

During the solidification of heavy ingots during casting, internal metallurgical defects are commonly observed. Despite the application of upsetting to remove internal voids in ingots, defects are often not fully eliminated by the end of the process. To address this challenge and produce upset ingots with minimal internal defects, this study introduces a novel approach. The first step involves simulating the formation of shrinkage porosity during ingot solidification and identifying the critical zone prone to internal defects. Subsequently, the study analyzes the effective strain distribution and mean stress in different sections of the critical zone using various upsetting anvil geometries. An optimized approach is then proposed, involving the shifting of the critical area to where the most significant plastic deformation is likely to occur. This is achieved through a new pin-making strategy and the selection of the best geometry for the pair of upsetting dies. To validate the model, 100CrMo7-3 heavy ingots are produced and subjected to upsetting and cogging operations using a 63MN hydraulic press. The results from ultrasonic and microscopic examinations indicate that the proposed method leads to fewer internal imperfections. Additionally, a comparison between numerical and experimental results demonstrates good agreement, resulting in a reduced risk of remaining internal shrinkage porosities after upsetting large-scale ingots.