A system for degassing hydrogen uses silicon nitride ceramic rotors. The technology’s rotors stir molten aluminum and disperse the gas. By adding bubbles of an inert gas, hydrogen is drawn out from the metal, which otherwise would cause voids and substantially weaken castings.
Most rotors for this purpose are made of graphite. Graphite rotors, however, cannot withstand the high heat of the molten aluminum for long, and they have a useful lifetime of between one and four weeks. The new Nissan equipment overcomes both the short lifetime of graphite rotors and the cracking problems of ceramic rotors. During production, the rotors reduce half of the dross on the molten aluminum metal surface. Similarly, the porous material reduces 60 percent of the consumption of argon gas.