1、 Flow marks patterns
Appearance inspection: there are striations on the surface of the casting that are consistent with the flow direction of the liquid metal, there are obvious non directional striations that are different the color of the metal matrix, there is no development trend.
1. The causes of flow marks are as follows:
(1) Mold temperature too low.
(2) The runner design is poor, the position of the inner gate is poor.
(3) The material temperature is too low.
(4) Low filling speed short filling time.
(5) The pouring system is unreasonable.
(6) Poor exhaust.
(7) spray is unreasonable.
2. The cause of the pattern is too much coating in the cavity poor coating quality. The solution prevention methods are as follows:
(1) Adjust the cross-section area position of the internal sprue.
(2) Increase mold temperature.
(3) Adjust the speed pressure of the inner sprue.
(4) Proper selection of coating adjustment of dosage.
2、 Net hairy wing (turtle crack)
Appearance inspection: the surface of die casting has the mark of net hair like bulge depression, which expands extends with the increase of die casting times. The causes are as follows:
(1) There are cracks on the surface of die cavity.
(2) Uneven preheating of die casting die.
The solutions prevention methods are as follows:
(1) The die casting die should be annealed regularly a certain number of times after die casting to eliminate the stress in the cavity.
(2) If the cavity surface has tortoise cracks, the molding surface shall be polished to remove the crack layer.
(3) Mold preheating should be uniform.
3、 Discussion on cold insulation of aluminum die casting factory
Appearance inspection: the surface of the die casting has obvious, irregular, sagging linear pattern (penetration non penetration). The shape is small, narrow long, sometimes the intersection edge is smooth, it may break under the action of external force. The causes are as follows:
(1) The two streams of metal connect with each other, but they are completely fused there is no inclusion between them, the bonding force of the two streams of metal is very weak;
(2) The pouring temperature die casting temperature is low;
(3) The sprue position is right the flow path is too long;
(4) Low filling speed.
The solutions prevention methods are as follows:
(1) Raise pouring temperature properly;
(2) Increase the compression injection ratio, shorten the filling time increase the injection speed.
(3) Improve exhaust filling conditions.
4、 On shrinkage (dent)
Appearance inspection: there are smooth dents on the surface of the most thick part of the die casting (like a disc). The causes are as follows:
(1) Caused by contraction
1.1 the wall thickness difference of die casting is too large due to improper design;
1.2 the sprue position is improper;
1.3 the pressure injection ratio is low the pressure holding time is short;
1.4 the local temperature of the die casting mold is too high.
(2) Unreasonable design of cooling system;
(3) Early opening;
(4) Pouring temperature is too high.
The solutions prevention methods are as follows:
(1) The wall thickness shall be uniform;
(2) The transition of thickness should be eased;
(3) Correct selection of the location of alloy liquid introduction increase of the cross-sectional area of the inner runner;
(4) Increase injection pressure prolong holding time;
(5) Properly reduce the pouring temperature die-casting temperature;
(6) Local cooling is required for local high temperature;
(7) Improve discharge conditions;