The blank is broken or broken, forming elongated cracks, which are irregularly lined, with two kinds of penetration and non-penetration, which develop under the action of external force. The difference between cold and hot crack: the metal in the cold crack is not oxidized, and the hot crack is oxidized.
Reason for formation:
(1) The casting structure is unreasonable, and the shrinkage resistance is too small.
(2) The ejector device is deflected and the force is uneven.
(3) The mold temperature is too low or too high, and it is severely strained and cracked.
(4) The harmful elements in the alloy exceed the standard and the elongation decreases.
(1) Improve the structure of the casting, reduce the difference in wall thickness, increase the roundness and the arc R, and set the process ribs to make the section change smoothly.
(2) Correct the mold.
(3) Adjust the mold temperature to the working temperature to remove the slope and unevenness and avoid cracking.
(4) Control the composition of the aluminum coating to make it a harmful element.