| 摘要 |
PURPOSE:To prevent the surface of a product from becoming black by projecting zinc group blast shot with a specific hardness at a specific projecting speed using a blast machine in which a rubber lining sheet is not used at the time of applying blasting process on an aluminum die cast product. CONSTITUTION:A zinc group blast shot is formed by forming a zinc of high purity or a zinc alloy into grain type shot. As for a blast machine, a blast machine in which thick zinc plating, etc. is used instead of a rubber lining sheet for a lining on the blast machine site which is brought into contact with the blast shot, is used to carry out projection. If the hardness and projecting speed of the shot are excessively high, the recesses of the projecting marks are liable to be produced on a blasted product. And, this tendency is markedly shown in an aluminum die cast product. Accordingly, it is desirable to employ a low projecting speed of 25-34m/sec using soft zinc group shot with a hardness Hv=30-39 for the aluminum die cast product.
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