A, strain, along the open direction of the casting surface showing a strip of traces of trauma, there is a certain depth, serious for a face-like scars. The other is the metal liquid and mold welding, adhesion and strain. So that the surface of the casting more meat or lack of meat.
Reason: the cavity surface damage, the direction of the mold is too small or inclined slope, the top out into the skew, pouring temperature is too high, the mold temperature is too high lead to alloy liquid adhesion. The use of release agent is not good, iron content of less than 0.6%.
B, bubble: aluminum alloy die castings on the surface of the grain size of the uplift also has subcutaneous formation of the cavity.
The reason is that the alloy liquid in the pressure chamber is too low, easy to produce rolling gas, injection rate is too high, mold exhaust bad, the melt is not degassing, melting temperature is too high, mold temperature is too high, metal solidification time is not enough, Strength is not enough, and premature mold out of casting, compressed gas expansion, too many release agent.
C, cold separation, die casting surface has obvious, irregular, subsidence linear lines (there are two types of penetration and not through) shape small and narrow, sometimes the edge of the smooth transfer, the possibility of development in the external force.
Cause: two metal flow docking each other, but not completely fused and no inclusion in the meantime, two metal binding milk weak. Pouring temperature or die casting mold temperature is low, the choice of alloy improper, poor mobility, sprue position is not right or flow is too long, true charge speed is low, the injection ratio is low.
D, discoloration, spot: casting surface showing a different color than the base metal.
Reason: improper release agent, release agent used too much, over the ground, graphite containing graphite lubricant fell into the casting surface.