Abstract: A method for controlling the magnesium content of molten aluminum includes the steps of injecting a halogen gas into the molten aluminum, sampling a portion of the resulting gases evolved from the molten aluminum, detecting the presence of constituents in the sampled gases and/or characteristics of the sampled gases indicative of the imminent evolution of unreacted halogen gas, and adjusting the rate of halogen gas injection to approach the point where unreacted halogen gas is about to be evolved. In the preferred embodiment, the halogen gas is chlorine; the detected constituents are gaseous hydrogen chloride (CHl) and aluminum chlorhydrate compounds (Al.sub.2 Cl.sub.x .multidot.(OH).sub.6-x); and the detected characteristic is the opacity of the sampled gases. The invention includes a technique for adjusting the rate of halogen gas injection so as to approach the optimal rate. The invention also includes (1) a sensor for detecting the content of HCl and Al.sub.2 Cl.sub.x .multidot.(OH).sub.

Abstract: A molten metal pump includes a filter that prevents ingestion of foreign material such as dross from molten metal within which the pump is immersed. The filter is a large structure that is secured to the base of the pump surrounding the pump's inlet. The filter forms a cavity adjacent the pump's inlet. The ratio of the surface area of the filter to the inlet area of the pump is very large; the filter has a low porosity while maintaining a high flow rate for the pump.

Abstract: A method of melting metal particles includes the steps of swirling molten metal in a vortex within a crucible, adding metal particles onto the surface of the metal, and submerging the metal particles substantially immediately after the particles have been added onto the surface. Apparatus for carrying out the method includes a mixer having a vertically oriented sleeve secured to the bottom of the crucible, the sleeve supporting a plurality of blades on its outer surface and having a plurality of openings adjacent its bottom. The blades force the metal particles beneath the surface of the metal and create turbulence which ensures rapid melting of the particles. The blades as well as the openings adjacent the bottom of the sleeve break up any agglomerated metal particles. Discharge piping is connected to the bottom of the crucible. A vortex breaker is disposed in the piping to control the vortex in the crucible.