Design of Runner and Gating Systems for the Investment Casting of 431 Stainless Steel Netting Hook through Numerical Simulation

Abstract

In the production of netting hook, which requires wear resistance and long service life enabling the fishing net production with high efficiency, there has been some studies to achieve its forming method for high durability and designated smooth surface. The process of investment casting or known as “lost wax casting” is one of casting methods to fabricate metal part with a complex shape. Flow behavior of stainless steel grade 431 at the temperature higher than 1600°C is a critical factor in casting mold design of the lost wax process. In the study, CAST-DESINERTMsimulating software was used to analyze flow of liquid metal to clarify the solidification of SS431 which caused defects in the product. Non-preferred heat transfer phenomena and using of the unsuitable mold design normally lead to defects in casting such as misruns, cold shuts, shrinkage, pin holes and porosity. Parameters in casting such as pouring temperature, preheating temperature, preheat time, pouring rate and cooling rate were given by the current production condition. The experimental design technique for simulation analysis of casting and gating system has been designed to be consistent and appropriate to the casting part. The cross-sectional design of the runner was two types of hexagonal and circular cross-section runner. The angle of gating system was kept constant at 90 degrees to the runner. As a results of the simulations, shrinkage porosity, filling time as well as solidification time were used to evaluate the cross-sectional design of runners. It was found that a circular cross-section runner led to the shorter filling time than a hexagonal one. Furthermore, there was no remarkable difference of shrinkage porosity in all simulated conditions. However, in terms of filling time, the results depended on the combination of runner design and gating system.