Process and apparatus having improved efficiency for producing a semi-solid slurry

Claim 1

A process for improving efficiency in forming a semi-solid alloy slurry, said slurry comprising degenerate dendritic primary solid particles in a surrounding matrix of molten metal, said process comprising: providing means for containing said molten metal, said containing means having a solidification zone; electromagnetically mixing said molten metal and shearing dendrites formed in said solidification zone at a desired shearing rate; said step of electromagnetically mixing comprising: providing means for generating a moving magnetic field; supplying current at a desired frequency to said magnetic field generating means; generating said moving magnetic field with said magnetic field generating means, wherein the improvement comprises: reducing the power consumption of said generating means; said step of reducing said power consumption comprising controlling said frequency so that for said slurry having an effective cross section diameter in the range up to about 2 inches, said frequency is maintained in the range defined by the equation: ##EQU3## and for said slurry having said effective cross section diameter greater than about 2 inches, said frequency is maintained in the range defined by the equation: f=Y{[0.136×10.sup.5 (in·sec.sup.2).sup.-1 (Δ)-68.7 (in·sec).sup.-1 ]D+[-2.27×10.sup.5 sec.sup.-2 (Δ)+478 sec.sup.-1 ]} where x=from about 0.75 to about 1.25 y=from about 0.5 to about 1.5 D=said effective cross section diameter Δ=σμ o t 2 σ=electrical conductivity of said containing means μ o =magnetic permeability of said containing means t=thickness of said containing means.