METAL-POWDER PRODUCTION BY CENTRIFUGAL ATOMIZATION

A new atomizer has been designed and constructed of the centrifugal di sc type. A liquid metal stream leaving the tundish enters the centre o f the disc and is atomized by centrifugal force. Droplets formed fly i n air and then enter a water vortex barrier 5cm thick. The wafer barri er is 10cm away from the disc. Solidification is partially in air and partially in water. Lead, aluminium and 8640 steel have been atomized Atomization and material parameters investigated were: (1) disc shape (flat, cup shaped and vaned) and size, (2) liquid metals (different de nsities and melting temperatures), (3) liquid metal superheat (varying viscosity and surface tension), (4) disc speed (15,000rpm (1570rad/s) to 25,000rpm (2618rad/s) and (5) liquid metal flowrate. The character istics of the powders produced were examined by various techniques. Th e shape of the steel powders was spherical and that of aluminium and l ead powders was irregular Mean powder size is dependent on the atomizi ng parameters, and is about 100 mu m. Microhardness of the steel powde r is 1045 HV, which has a supercooled martensitic structure. Of the th ree different disc geometries, the performance of the vaned disc was m uch better than that of the others. The powders produced were finer; a nd the efficiency and production rate were much higher than with the o ther disc shapes