[China Aluminum Network] I. Flow marks and patterns
Visual inspection: There are streaks on the surface of the casting that are consistent with the direction of the flow of molten metal. There are clearly visible non-directional lines that are not the same as the color of the metal substrate, and there is no development trend.
1. The causes of flow marks are as follows:
(1) The mold temperature is too low.
(2) Bad sprue design and poor position of the inner gate.
(3) The material temperature is too low.
(4) The filling speed is low and the filling time is short.
(5) The pouring system is irrational.
(6) Bad exhaust.
(7) Spray is not reasonable.
2. The reason for the pattern is that the paint in the cavity is over-sprayed or the coating quality is poor. The solution and prevention method is as follows:
(1) Adjust the cross-sectional area or position of the inner runner.
(2) increase the mold temperature.
(3) Adjust the inner runner speed and pressure.
(4) Appropriate choice of coating and adjustment of dosage.
two. Mesh fleece (tortoise crack)
Visual inspection: On the surface of the die-casting, there are traces of raised or recessed hair on the surface of the die-casting, which continuously expands and extends as the number of die castings increases.
The reason is as follows:
(1) There is a crack on the surface of the die cavity.
(2) The preheating of the die casting mold is not uniform.
The solution and prevention method is:
(1) After the die-casting mold is to be periodically or pressure-cast for a certain number of times, it shall be annealed to eliminate the stress in the cavity.
(2) If a crack has appeared on the surface of the cavity, the forming surface should be ground and the crack layer removed.
(3) Mold preheating should be uniform.
three. Cold partition
Visual inspection: The surface of the die casting has obvious, irregular, sagging linear patterns (both penetrating and non-penetrating). The shape is small and long, and sometimes the interface is smooth, and it may be broken under external force.
The reason is as follows:
(1) Two metal streams butt each other, but not fully fused but without inclusion, the bonding force of the two metals is very weak; (2) the pouring temperature or the temperature of the die casting mold is low;
(3) The runner is not in the correct position or the flow path is too long;
(4) The filling speed is low.
The solution and prevention method is:
(1) Properly increase the pouring temperature;
(2) Improve the injection time, shorten the filling time, and increase the injection speed.
(3) Improve exhaust and filling conditions.
four. Sinking (dent)
Visual inspection: There is a smooth dent (like a dish) on the surface of most of the die casting thickness.
The reason is as follows:
(1) Caused by shrinkage
1.1 Improper die-casting design is too thick;
1.2 improper placement of runners;
1.3 Injection pressure is lower and holding time is shorter;
1.4 The local temperature of the die casting mold is too high.
(2) The design of cooling system is not reasonable;
(3) premature opening;
(4) The pouring temperature is too high.
The solution and prevention method is:
(1) The wall thickness should be uniform;
(2) Thickness transition should be eased;
(3) Correctly select the location of the alloy liquid to be introduced and increase the cross-sectional area of ​​the inner runner; (4) Increase the injection pressure and extend the pressure holding time;
(5) Properly reduce the pouring temperature and temperature of the die casting mold;
(6) Local cooling for local high temperatures;
(7) Improve the overflow conditions;
Fives. Imprint
Visual inspection: traces left on the surface of the casting surface in contact with the surface of the die casting mold or on the surface of the casting.
The reason is as follows:
1, caused by ejector components
(1) The top end face is worn;
(2) Inconsistent adjustment of the top rod;
(3) The joint between the die-casting mold cavity splicing part and other parts is not good; 2. It is caused by the splicing or moving part
(1) Part of the insert is loose;
(2) Loose or worn parts of the activity;
(3) The surface of the side wall of the casting is formed by inserts that are interspersed with moving and fixed molds.
The solution and prevention method is:
(1) The length of the top bar must be adjusted to the proper position;
(2) Fastening blocks or other movable parts
(3) eliminate sharp corners when designing, fit with gap adjustment;
(4) to improve the casting structure so that the die-casting mold to eliminate interspersed mosaic form, improve the die casting mold structure; Adhesive traces
Visual inspection: Small pieces and metal or non-metal are welded to the base part of the metal, and flakes are peeled off under the action of external force. The surface of the casting after peeling is shiny and dark gray.
The reason for this is as follows:
(1) There are metal or non-metal residues on the surface of the die casting mold cavity; (2) Impurities are first attached to the surface of the cavity during casting.
The solution and prevention method is:
(1) Before the die-casting, the cavity pressure chamber and the pouring system should be cleaned to remove metal or non-metallic adhesions; (2) The poured alloy must also be cleaned;
(3) Select the appropriate coating, the coating should be uniform.
Seven. Layering (sandwiching and peeling)
Visual inspection or damage inspection: There is a significant level of metal in the casting.
The reason for this is as follows:
(1) The mold rigidity is not enough. In the metal liquid filling process, the template generates jitter; (2) The punches appear to crawl during the injection process;
(3) Improperly designed sprue system.
The solution and prevention method is:
(1) Strengthen the mold rigidity, fasten the mold parts and make them stable; (2) Adjust the cooperation of the injection punches and pressure chambers to eliminate the crawling phenomenon; (3) Reasonably design the inner runner.
Eight. Friction ablation
Visual inspection: The surface of the die casting produces a rough surface at certain locations.
The reason for this is as follows:
(1) The position and shape of the inflow runner caused by the die casting type (die) are not proper; (2) the cooling of the molten metal in the inflow runner caused by the casting condition is insufficient.
The solution and prevention method is:
(1) to improve the position and direction of the inflow runners; (2) to improve the cooling conditions, in particular, to improve the metal fluid flushing; (3) to increase the ablation part of the coating;
(4) Adjust the flow rate of the alloy fluid so that it does not generate cavitation
(5) Elimination of alloy adherents on molds.
nine. Erosion
Visual inspection: There are spots or ridges on the die castings.
The reason for this is as follows:
(1) Improper setting of the sprue location;
(2) The cooling condition is not good.
The solution and prevention method is:
(1) The thickness of the inner runner should be appropriate;
(2) Modify the position, direction and setting method of the inner runner;
(3) Strengthen the cooling of the eroded area.
ten. crack
Visual inspection: The casting was placed in an alkaline solution and the crack was dark gray. The destruction and cracking of the metal matrix is ​​linear or wavy. The lines are narrow and long, and there is a tendency to develop under the influence of external forces.
Aluminum alloy casting cracks.
Surface Treatment Process,Aluminium Surface Treatments,Metal Treatment,Metal Surface Treatment
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