| 摘要 |
A process is described for recycling scrap aluminum-matrix composites, e.g. gates and risers from a casting operation. A melt of the scrap composite is provided in a treatment vessel by heating at a temperature of 720 DEG -750 DEG C., such as to avoid unwanted stirring and contamination of the melt. While mixing with the impeller, a gas is injected through a gas outlet beneath the surface of the melt and near the rotating impeller. This melt is mixed with a vaned rotor impeller such that no vortex is formed and oxide film is not drawn into the melt. This treatment gas comprises a mixture of a major proportion of an inert gas and a minor proportion of reactive gas. The gas injection is continued only until small gas bubbles have been well distributed through the melt but before the gas causes the reinforcing parties to start rising to the surface. After the gas is stopped, the melt is allowed to rest for a period of time at the reaction temperature of 720 DEG -750 DEG C. with at least periodic gentle mixing to keep the reinforcing particles distributed evenly throughout the melt. During this treatment, hydrogen is removed from the melt by diffusion into the gas bubbles and the other non-metallic impurities are attached to the bubbles and lifted into a dross layer on the surface by flotation, while the reinforcing particles remain dispersed in the melt. The dross layer containing oxide films and other impurities is skimmed from the surface of the melt, leaving a purified aluminum matrix composite. This composite can then be cast in the usual manner.
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