Air shrinkage hole defect of cylinder block water pump shell casting

ZHY Casting trial-produced a new type of dry-type cylinder liner, four-cylinder diesel cylinder block. The overall dimension of the casting is 437 mm × 257 mm × 432mm, main wall thickness 5.5 mm, minimum wall thickness 4.5 mm, maximum wall thickness 60 mm, casting unit weight 69 kg, material grade HT250. With the cylinder hole as the center, cooling water channels are designed on both sides of the cylinder block. The gear chamber and cooling water pump are respectively located on both sides of the cylinder block. Their highest points are 103 mm and 130 mm from the upper and lower parts of the cylinder block, 180 mm and 235 mm from the parting surface, and the structure is relatively thick. Therefore, the remarkable feature of “very uneven wall thickness and the highest points are far higher than the left and right end faces” is formed, The schematic diagram of its casting structure is shown in the figure.

(1) Due to the fast cooling speed of the sand-covered iron mold process and the poor fluidity of the surface layer of molten iron, the method of exhausting air by means of air injection through the exhaust needle and eliminating the mold cavity is not feasible.

(2) In the design and parting of sand-covered iron mold process, special consideration should be given to the isolated hot spot. The gas shrinkage hole can be avoided by modifying the structure to make its wall thickness uniform or by placing the isolated hot spot downward.