The tilt casting process

Tilt casting is a process with the unique feature that, in principle, liquid metal can be transferred into a mould by simple mechanical means under the action of gravity, but without surface turbulence. It therefore has the potential to produce very high quality castings. Even so, the process is not often optimised in the industrial environment. This investigation represents an attempt to investigate some fundamental problems associated with the process. A computer controlled, programmable roll-over casting wheel with a diameter of 1 m was used to produce sand castings in an Al-4.5% Cu alloy. The filling of the mould was studied using real-time X-ray radiography. Real-time X-ray radiography revealed that the molten metal could exhibit tranquil, turbulent or chaotic flow into the mould during tilt casting, depending on (i) the angle of tilt of the mould at the start of casting, and (ii) the tilting speed. Essentially horizontal transfer of the melt could achieve tranquil filling of the mould with minimum surface turbulence by a tilt starting position above the horizontal. The tensile properties of castings made using various starting conditions and rotation rates were measured and the results analysed using Weibull statistics to quantify reliability. Results are summarised on a map of the various operating regimes for tilt casting. An operational window for the production of reliable castings has been defined for the first time.