A concave portion that appears on a smooth surface.
Reason for formation:
(1) The structure of the casting is unreasonable, and a hot section is generated in the local thick portion.
(2) The alloy has a large shrinkage rate.
(3) The gate cross-sectional area is too small.
(4) The mold temperature is too high.
(1) Improve the structure of the casting, the wall thickness should be as uniform as possible, and the transitional connection should be used. The thick part can be used to eliminate the heat knot.
(2) Reduce the alloy shrinkage.
(3) Appropriately increase the cross-sectional area of the ingate.
(4) Reduce the temperature of the aluminum liquid and the temperature of the mold, use a temperature control and cooling device to improve the heat balance condition of the mold, improve the exhaust condition of the mold, and use a paint with a small amount of gas.