Certain Aspects of Particle Distribution in Castings Formed in Rotating Moulds

Abstract

The paper undertakes to demonstrate dispersal of particles with varied densities in a melt solidifying in a rotating mould, through laboratory experiment. Molten wax, wood and sand particles were considered for the purpose. Mixture of the three, in pre decided proportions, was poured into a refractory lined, split mould, rotating about its vertical axis at different speeds and the melt was allowed to solidify under the influence of the resulting centrifugal force. Slices of the casting so obtained, were examined using an optical microscope. Also, temperature and viscosity profiles of the melt, as well as the velocity and position of the particles in the melt at any instant of time, were analyzed, with the aid of relevant mathematical equations. The solidified wax was seen to have heavy sand-particles at the outer most surface and the thickness of the particle-rich-zone decreased with the increase of mould-rotational-speed. The analytical and experimental findings were in good agreement. The investigation, also, established significant contributions of combinations of 'speed of rotation' and 'mould size' towards graded distribution of particles in the solidified melt leading to gradation of properties in the resultant casting.