Abstract
An evaluation of the effect of counter gravity filling of investment castings on the reproducibility of mechanical properties has been carried out for a low alloy steel. Two types of gravity filled moulds, (reflecting ‘bad’ running system design practice and ‘good’ practice), and four types of counter gravity filled moulds were cast and their mechanical properties assessed by tensile testing. The Weibull moduli of the results were determined as a measure of reproducibility of the mechanical properties associated with the different casting processes. The results showed that the counter gravity filling method produced higher values of the Weibull modulus than gravity filled methods, even with well designed running systems. This clearly demonstrated the value of a mould filling approach that avoided entrainment of the surface of the cast steel. The highest value of the Weibull modulus (>186), was associated with the ‘C3 process’, in which the mould was rotated during solidification.
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