Filter systems for high velocity liquid metal flow

Abstract

Liquid cast iron (carbon equivalent, CE = 4.3%) and Al–12.5Si were poured down a 500 mm tall sprue and cast in a straight fluidity test channel, with and without a filter system. Different arrangements of filter and bubble trap were compared to assess their effectiveness. The filling sequence was recorded on videotape by the use of real time x-ray radiography. Measurements were made of the speed of the metal and the distance to which it flowed in the fluidity casting. A critical finding was that the soundness of samples revealed a relationship with the velocity of the melt; the lower the velocity, the fewer the defects. The final design of a filtering system seems to require a mechanism for the detrainment of bubbles and the reduction in velocity of the melt from over 2 m s -1 to 0.4–0.8 m s-1. In consequence, the fluidity of the melt is reduced, but the internal quality of the casting improved from being unacceptably impaired by entrained bubbles to being substantially free from such defects.