A novel approach for energy conservation by raw material preheating in green sand casting

Abstract

This research work presents a novel method of embedding/mixing metallic raw materials (fresh billets/scrap) with green sand molds in such a way that the scrap is aligned close to the mold cavity and recovers the waste heat and gets preheated when the molten metal is poured and solidifies in the mold cavity. The waste heat is the heat from the molten metal that is dissipated into the sand. This principle has been improvised by placing insulators around the scrap, resulting in better heat recovery. When this preheated scrap is loaded into the furnace for the consecutive melting, the furnace takes lesser energy for melting this preheated scrap than it would otherwise take if the scrap at room temperature is loaded, which is the practice in conventional methods. This concept is novel in the metal casting industry and hence there is no prior knowledge available in this regard. So, many experiments were conducted to prove the concept under various conditions: uniform shaped/sized scrap, random shaped scrap, box- enclosed scrap, scraps at different distances from the cavity, different charge materials (aluminium and cast iron), etc. Under all these conditions, the viability of the concept of waste heat recovery from the molten metal and preheating of the scrap was proved and the phenomena of how preheating varies under all these circumstances was understood. Finite Element Analysis using the commercial code, ANSYS was also carried out to simulate the heat flow. A mathematical model was developed using statistical analysis of the experimental data, to predict the amount of heat recovered from the solidifying molten metal, by predicting the peak temperature acquired by the raw material for any specific combination of the following experimental parameters: a) Offset distance (distance between raw materials and mold cavity), b) Moisture content in the molding sand, c) Insulator thickness In this model, a Response Surface Design using Box-Behnken method was adopted for the Design of Experiments (DoE).