Reasons for the peeling of aluminum castings

Reasons for the peeling of aluminum castings

The aluminum casting is a kind of surface defect commonly found in sand casting. It is a kind of surface defect commonly found in sand casting. It is limited when the surface of the casting is not solidified or the strength of the solidified shell is very low. Caused by arching and cracking. Mainly due to the quality of the molding sand and the modeling operation. The sand surface sand layer is expanded by heat, and whether the sand grains are rearranged depends on whether the seed stress can be absorbed.

After the metal is poured into the sand mold, a very dry layer is formed on the surface of the mold, and a high water layer is produced immediately after the dry layer, and the heat-wet tensile strength is much lower than that of the wet sand type body. The surface layer of the mold is thermally expanded, and stress is concentrated in the high water layer with low strength, and cracks occur, and the rat tail further develops into a sand-sanded crucible. Because the high water layer strength of the mold is low, and it is separated from the mold body due to the expansion of the dry layer on the surface of the mold, it can slide freely, and concludes that it is the most easy to produce in terms of sand inclusions. The condition is that the casting time is too long, and the aluminum casting has a wall thickness and a flat shape. The degree of sand inclusions is related to the time at which cracks occur on the surface of the sand. For example, if the high-water layer sand has high heat-wet tensile strength, the crack initiation time of the surface dry sand can be prolonged. If the molten metal is completely filled with the molding sand and no cracking is formed, the sanding and crucible defects of the casting are not formed. The longer all sands are cracked, the less likely they are to cause sand inclusions.