Chain conveyor remelt ingot casting improvement

Millions of tonnes of aluminum are produced on open mould chain conveyor ingot casting machines every year. Operators and thus manufacturers of these machines are interested in reducing the oxide levels in the ingots and reducing production costs by improving productivity. In addition to optimization of the current process through increased understanding, CAST has developed two patented technologies for ingot casting; a low dross filling system (CASTfill) and a mould design (CASTmould) with reduced ingot solidification time allowing 20% productivity increase. This paper describes the methodology used and application of various mathematical models including Smooth Particle Hydrodynamics (SPH). Protype filling system designs were tested on a full scale pilot system. The ingot/mould interface heat transfer was studied and measurements made of air gap formation and mould deformation on a purpose built rig which duplicates machine conditions. Relatively simple 2D inverse and 3D thermal models were used to gain insight by conducting simple sensitivity studies. The air gap formation controls the heat flow and the solidification time. Investigations were made into the use of helium. Alsim, a fully coupled 3D thermal stress model capable of predicting ingot and mould deformation and air gap formation was also applied to the problem. New mould designs were proposed and tested on the rig. Following successful plant testing both CASTfill and CASTmould have been adopted at a number of smelters.