Molten aluminum reacts with the water vapor to form hydrogenwhich can dissolve in the aluminum melt and be released duringthe solidification of casting as a harmful gas, resulting in porosityin the casting. There have been quite a few methods of degassingmolten aluminum in industry. However, the hydrogen content willincrease with the increasing of the time even if the effectivedegassing has been carried out carefully. In order to keep a lowhydrogen content all the time during the continual pouring (suchas the case in low pressure die casting, high pressure casting andpermanent gravity casting), a patented degassing method isinvestigated. A porous refractory absorber that is connected with avacuum system is immersed in the molten aluminum. The vacuumis started inside the porous absorber and the dissolved hydrogenatom will diffuse towards the absorber. In this way, the hydrogenin the melt is removed through the vacuum system. The absorberis made of mullite and of porous structure. It is permeable withgas but can’t be penetrated by the molten aluminum. RPTexperiment (Reduced Pressure Test) and density test wereconducted to evaluate effectiveness of the new method. Theexperiments indicate that use of the absorber can improve themetallurgical quality of the melt
展开▼
