Computer Simulation of Lost Foam Process of Cast Iron

Abstract

Although several computer simulation codes have been developed to predict and prevent defects of lost foam castings, most of them are focused on aluminum alloy castings. This paper presents a new simulation method suitable for not only aluminum alloy but also cast iron. First of all, main assumptions and numerical schemes are as below: 1) Gas flow in the mold follows the D’Arcy’s law. 2) The gas pressure in the kinetic zone (gas gap) is uniform in each gas group and is solved by using the flow field of melt one time-step before. 3) The gas obeys the ideal gas law. 4) Latent heats of evaporative pattern degradation are simplified by an overall latent heat in which both melting and evaporation are considered. 5) The pattern absorbs heat of melt through conduction, radiation and convection. Further, X-ray direct observations of mold filling behaviors of cast iron were carried out in order to better understand the physical fundamentals and to evaluate simulated results. It was found that: 1) Mold filling behaviors of cast iron are quite different from those of aluminum alloy castings depending on the gating system and thickness of the casting. 2) Bubble floating-up often occurred in the case of the downward flow. 3) Although the newly developed simulation code could predict the mold filling to some extent, further work needs to be done, including better understanding of the heat transfer mechanism between the melt and pattern.

A benchmark experiment of the mold filling of a cast iron plate by lost foam casting

“…Shivkumar et al 6 investigated the thermal degradation of the foam pattern, gaseous products and a partially depolymerized viscous residue by using a similar method. Sun et al 7 & Ohnaka et al 8 directly observed the mold filling behaviors during lost foam casting by X-ray method. Numerical simulation is also a widely used method for the investigation of the filling process of lost foam casting.…”

Thermal Analysis on Solidification Behaviors of Hypoeutectic Grey Iron in Lost Foam Casting

“…In recent years, considering characteristics of the lost foam casting, lots of researchers [2][3][4][5][6][7] pay more attention to understand characteristics of mold-filling and pyrolysis of cast iron. Through experiments and mathematical methods, they built the fluid melt and temperature distribution models of interface moving of metal and foam.…”