Optimal design of investment casting system for toothed chain joint: computer simulations and experimental verification

Abstract

The toothed chain joint is a major component in heavy lifting equipment. They are usually fabricated using casting; however, residual casting defects in the joint tend to reduce mechanical strength and can lead to crack formation and creep following long-term usage. They also pose a safety hazard. In this study, numerical simulation was used to optimize the investment casting parameters for toothed chain joints of SNCM220 alloy. Optimization was based on predictions of cavity shrinkage, as determined using the retained melt modulus and probabilistic defect parameter, and porosity defects, estimated using the combined defect parameter-Niyama criterion. Preliminary simulation and experiment results were used to guide the establishment of two casting schemes: CaseA (reducing the length of the runner and removing the auxiliary inlets on both sides) and CaseB (increasing the number of inlets). Further simulations were conducted wherein the runner was covered with cotton insulation (6-mm thick). Virtual thermo-dynamical sensors were also used to determine the rate and direction of solidification in the mold cavity. Under nondestructive testing based on X-ray analysis, the investment castings fabricated under optimal conditions exhibited none of the detrimental defects commonly associated with this type of casting.