ANALYSES OF INCLUSIONS IN MOLTEN ALUMINUM BY ELECTRICAL-RESISTIVITY MEASUREMENTS

A new device, the SICO counter, which can be used to analyze inclusions in molten aluminium. has been made and tested. The concept is based on Coulter's method. Metal is pumped through an orifice, and an electric current is passed through the aperture simultaneously. The size distribution of inclusions is determined by measuring the voltage pulses induced by particles passing the orifice. The SICO counter has been used in analysis of inclusions larger than 8 mum in large industrial melts. The measurements were carried out in launders. Four examples of the use of the SICO counter are given. It was found that the SICO counter gave results similar to those obtained with the filtration method and the centrifuging method. The latter methods showed that the inclusions larger than 8 mum in size were mainly oxide films and oxide lumps. The maximum diameter of the films was 200 mum and of the lumps 20 mum. The content of oxides varied from 0.1 ppm to 5 ppm in the materials analyzed.