To improve the removing efficiency of impurities and the service life and to reduce the inclusion quantity to a low level by coating a refractory- made aggregate surface with sodium silicate having softening or sticky-fusing point at the temp. of molten Al alloy.
As the refractory-made aggregate, alumina, magnesia, silica, mullite, silicon carbide or these mixtures are used and formed into a porous body having suitable shape from clay state or slurry state and fired to make a porous filter ≥6 holes/inch in the mesh. The surface of the aggregate is coated with sodium silicate having the softening or sticky-fusing point at the temp. of the molten Al alloy. The sodium silicate is indicated with a usual chemical formula NaxSiyOz (x=2 or 4, y=1, 2 or 4, and z=3, 4, 5 or 9) as outer soluble salt and meta-sodium silicate, ortho-sodium silicate, etc., are used. In this way, the inner part filtrating filter for removing the fine materials size of about 10-25 μm is obtd.
OSUMI KENJI
NAGAKURA YUTAKA
SHOWA ALUMINUM CORP
SKY ALUMINIUM
SUMITOMO LIGHT METAL IND
NIPPON LIGHT METAL CO
FURUKAWA ELECTRIC CO LTD
MITSUBISHI ALUMINIUM
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