Magneto-hydro-dynamic (MHD) casting is the way that Vforge produces the specially required feedstock that facilitates semi-solid metal flow. MHD technology is used widely in the casting world from pumping metals, containing metals, and moldless casting, as a few examples.
It may not seem obvious, but nearly all metal systems and alloys from zinc to steel to titanium are crystalline in nature. That fact alone is remarkable for any young engineer! Crystals are things like sugar and salt, but metals too? But it’s the manipulation of the metal crystals that is one of the keys to how the steel industry is able to achieve incredibly high strengths or the aluminum industry is able to make very thin wall aluminum cans with almost no metal loss.
At Vforge, our horizontal continuous casting system uses powerful magnetic fields to stir the aluminum alloys as they freeze in a water-cooled mold. The stirring action induced by our MHD system suppresses the formation of needle-like dendritic crystals and instead produces crystals that are of equal dimension in all directions. These are called “equiaxed” dendrites and they are the forerunner of the globular structure we need to practice semi-solid thixocasting.
Once we have continuously cast round bar with the equiaxed dendritic microstructure, our induction heating systems are designed to induce transformation into solid globules floating in an ocean of the partial liquid. At roughly 65% solid globules and 35% liquid, we are at an ideal state for injecting our viscous, two-phase material into a die to produce parts.
