2014 Volume 55 Issue 5 Pages 806-812
Permanent magnetic stirring is superior in terms of cost and operability compared with electromagnetic stirring. However, it is applied only to melting furnace. In this study, attempts were made to apply permanent magnetic stirring molten metal, and the effects of the stirring on grain refinement, increase in hardness, and suppression of porosity were investigated. We used a stirring device developed by ourselves and two alloys with different solidification morphologies and specific gravities (ρ). Results showed that needlelike crystals were cut off in Sn–Cu–Sb alloy (ρ = 7.4). On the other hand, the growth of columnar crystals was inhibited, and grain refinement and a region growing with equiaxed crystals were observed in Al–Cu alloy (ρ = 2.7) due to the stirring. Furthermore, increased hardness and suppression of porosity were confirmed with the increase in the rotating velocity of magnets in both alloys. Theoretical calculations showed that the molten metal near the mold was directly stirred by Lorentz force, but other regions were indirectly stirred by the flow of force from the directly stirring.
