Study on the Filtering Purification of AZ91 Magnesium Alloy

High quality magnesium casting depends significantly on the purification of its alloy melt. However, it is very difficult to obtain high-quality magnesium alloy melt due to its high reactivity and its tendency of combustion. The fluxing processing, a traditional purification method for magnesium melt, not only bears the risk of flux inclusions but also is facing more and more environmental pressure today. Therefore, the effective substitutes for fluxing processing, such as physical filtering method, are paid more attention recently. In this paper, the effects of technological conditions including the pore size of stainless steel mesh and the filtering temperature on the purification degree of AZ91 alloy melt were investigated in the mesh filtering processing, in which 2 wt.% calcium was added into the melt in order to obtaining ignition-proof property. The results indicated that mesh filtering processing could improve the purification degree markedly, and the purification degree increased with the increase of filtering temperature properly or the decreased of pore size of mesh. However, too high filtering temperature would lead to the increasing of the tendency of oxidation and combustion, and too small pore size would decrease the filtering ability of mesh which would lead to the interrupting of purification operation.