Effects of grain size and shape of refractory aggregates on surface roughness of castings

Effects of surface energy, grain size and shape of coating aggregates for metal mold casting on wettability of aluminum alloy melt and surface roughness of castings were investigated. The results show that the key factors influencing the wettability of alloy melt is surface energy of coating aggregates, and the secondary factors are grain size and shape. With the decrease of the aggregate surface energy, the contact angle of melt with coating is increased, and the corresponding roughness value of castings surface is decreased. With the grain size of aggregate less than 44 μm, the contact angles of melt with coatings are increased with the grain size increase. With the grain size of aggregates more than 44 μm, the contact angles of melt with coatings are decreased with the grain size increase. Spherical and ac-icular aggregate can improve the contact angles of melt with coatings and decrease the corresponding surface roughness.