Pressure filtration tests of liquid Al-Si cast alloys

Though the cake mode generally dominates the Prefil Footprinter® tests, the filtrate weight versus filtration time curves deviate, to some extent, from conventional filtration equations at constant pressure. This work attempts to seek other models for the Prefil Footprinter® curves. It is interesting to find that there is a good linear relationship between ln(weight, in grams) and ln(time, in seconds) over the whole course of the filtration period, i.e. filtrate weight can be best expressed as a power function of filtration time. In the presence of the complete blockage stage, the filtrate weight or ln(weight) appears to be a line paralleling to X-axis at this substage. The physical mechanism for the model is not known at the moment. The Prefil Footprinter® filtrate weight versus filtration time curves will never be convex, i.e. they appear as concave and/or straight lines.