A. Cold partition
Features: The gaps that appear when the metal flows with lower temperature butt but are not fused are irregular linear, there are two kinds of penetrating and non-penetrating, and there is a development trend under the action of external force.
Cause:
1. The molten metal
casting temperature is low or the mold temperature is low.
2. The alloy composition does not meet the standard and the fluidity is poor.
3. The molten metal is filled in separate strands, and the fusion is poor.
4. The gate is unreasonable and the process is too long.
B. scratches
Features: Along the demoulding direction, due to metal adhesion, the mold manufacturing slope is too small, resulting in scratch marks on the surface of the casting, and in severe cases it becomes a scratch surface.
Cause:
1. The
casting slope of the core and wall is too small or the inclination occurs.
2. There are pressure scars on the core and wall.
3. The paint is often not sprayed.
4. The iron content in the aluminum alloy is less than 0.6%
C. Sag
Features: The concave part that appears on the smooth surface of the casting, the surface is in a state of natural cooling.
Cause:
1. The structural design of the casting is unreasonable, and there are local thick parts, resulting in hot spots.
2. The alloy shrinkage rate is large.
3. The inner gate is cut and the product is too small.
4. The mold temperature is too high.
D. Bubbles
Features: Bubbles formed by the bulging of accumulated gas under the
casting skin.
Cause:
1. The mold temperature is too high.
2. The filling speed is too high, and the metal flow is involved in too much gas.
3. The coating has a large amount of gas, and the amount is too much, and it is not burnt out before pouring, so that the volatile gas is wrapped in the surface of the casting.
4. The exhaust is not smooth.
