Defects and Prevention of Lost Foam Casting-Sand Sticking
The molten metal penetrates into the sand mold to form a mechanical mixture of metal and sand. There are two situations: one is that the molten metal penetrates into the molding sand through the cracks of the coating to form iron-clad sand (ie, mechanical sanding). This defect can generally be Clear away; another situation is that metal penetrates into the molding sand through the coating, forming chemical sticky sand that is difficult to remove.
(1) Reasons 1) In the case of coating cracks, due to insufficient molding sand compactness, excessive molding sand particles and excessive vacuum, the first medium-sticky sand situation occurs.
2) When the coating is too thin or partially not brushed, the second kind of sand will be produced when the temperature of the molten metal is high and the vacuum is large.
(2) Preventive measures
1) Improve the thickness and refractoriness of the coating.
2) When modeling, the tightness should not be too large to avoid damage to the coating.
3) Choose the appropriate negative pressure. 4) Choose finer raw sand.
5) The pouring temperature should not be too high.
6) Choose the right pressure head.
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