Causes: the surface of the cavity is damaged, the slope of the mold direction is too small or inclined, the ejection and entry are skewed, the pouring temperature is too high, and the mold temperature is too high, which leads to the adhesion of alloy liquid. The use effect of release agent is not good, and the iron content is lower than 0. 6% and so on.
B. Bubble: The surface of aluminum alloy die casting has a protrusion the size of a grain of rice, and a cavity is formed under the skin.
The reasons are as follows: the alloy liquid is too low in the pressure chamber, which is easy to cause gas entrainment, the injection speed is too high, the mold exhaust is poor, the molten liquid does not degas, the melting temperature is too high, the mold temperature is too high, the metal solidification time is not enough, the strength is not enough, the casting is ejected too early, the pressurized gas expands, and the release agent is too much.
C, cold preservation, the surface of the die casting has obvious, irregular and concave linear lines (penetrating and non-penetrating), which are small and long, sometimes the transition edge is smooth, and it is possible to develop under the action of external force.
Reason: The two metal flows butt each other, but they are not completely fused, and there is no inclusion in the middle, so the binding force of the two metal flows is weak. Low pouring temperature or die casting mold temperature, improper alloy selection, poor fluidity, incorrect runner position or long runner length, low real filling speed and low injection ratio.
D, discoloration and spots: the surface of the casting presents a color different from that of the base material.
Reason: Improper release agent, excessive use of release agent, graphite in lubricant containing graphite falling to the surface of casting.
References:
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