| 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 blasting an aluminum die cast product. CONSTITUTION:Blast shot is projected at a projecting speed of 25-34m/sec from a blast machine to the treated object of an aluminum die cast product, etc. using zinc group blast shot made of a zinc or a zinc alloy in which an iron grade is less than 0.01wt.%, having a hardness within the range of Hv=30-45, and in which the oxide film on the grain face is removed, to carry out blasting. In this case, a blast machine in which a rubber sheet is not used as the lining on a blast machine site which is brought into contact with the shot is used. The oxide film on the surface of shot can be reduced or removed at the time of the manufacture of the shot while also being able to be removed with an appropriate means after the manufacture. In order to suppress the oxidation of surface at the time of manufacture, e.g., a deoxidizer is added to water to remove the dissolved oxygen in the water, and the shot is sufficiently dried by means of flash drying.
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