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Abstract
An experimental centrifugal atomiser was designed and constructed. The apparatus operates on the principle of atomising molten metal by pouring it onto a water jet cooled rotating disc. The disc was of a cylindrical reversed cup shape and the disc was cooled on the reverse side. The cooling water did not come into contact with the liquid metal and powders produced. Liquid metal did not stick on the disc because of effective cooling. Pure tin was used as the raw material to investigate the effects of production parameters, such as disc geometry, disc diameter, rotating speed, fin number, fin type, superheat and flowrate, of the liquid metal on the mean powder size and yield rate. Pure lead, zinc, aluminium and AA2014 alloy were also atomised to investigate the effects on metal types.
The mean particle size of powders produced were in the range of 100–150 μm for tin and lead, 170–220 μm for zinc and 350–400 μm for aluminium and AA2014 alloy depending on the process parameters. The shapes of the powders were generally irregular, flaky, teardroplike and ligamental. The amount of spherical and rounded powders increased with decreasing mean particle size. A flat disc geometry with inverted triangle shaped fins gave a finer mean particle size and higher yield rate than other designs. Increasing disc rotation speed, disc diameter, superheat of liquid metal (up to 218°C) and decreasing liquid metal flowrate resulted in a finer mean particle size and a higher yield rate for tin. Discs with two fins gave a finer mean particle size and a higher yield rate.