Review of fluidity concepts in casting

Abstract

The fundamentals of the different types of fluidity test, including the spiral test and the various thin section fluidity test, are evaluated. It is demonstrated that all of these tests actually give information in harmony, provided that proper allowance is made for the action of the effective section thickness on both the back-pressure due to capillary repulsion and the freezing time of the section. Thus the effect of the size and shape of the channel section is rationalised in terms of (i) the effective reduction in head pressure because of the back pressure due to surface tension, and (ii) the effective modulus of the section, since this directly affects its solidification time. It will be demonstrated that fluidity can be understood in terms of simple mechanisms of solidification, the superheat of the cast metal, and the latent heat of freezing. The action of remelting within a flowing channel leading to the continuous and indefinite flow of liquid metal is reintroduced here (following the original wo...