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Is the die casting mold directly related to product quality?

Essai Industries Co.,Ltd | Updated: Jun 15, 2017

The control of surface temperature of die casting die is very important for producing high quality die castings. Uneven or improper die-casting mold temperature will also lead to the casting size instability, in the production process of the top casting deformation, resulting in thermal pressure, viscous mold, surface depression, internal shrinkage and heat bubbles and other defects. When the difference of mold temperature is large, the variables in the production cycle, such as filling time, cooling time and spraying time, have different influences.
1). Cold lines:
Reason: The temperature of the front of the molten soup is too low, and there are traces in the overlap.
Improvement methods:
1. Check if the wall thickness is too thin (design or manufacture), the thinner area should be filled directly.
2. Check the shape is not easy to fill, the distance too far, closed areas (such as fins (Fin), raised), blocked areas, too small fillet, etc. are not easy to fill. And notice whether there are ribs or cold spots.
3. Shorten filling time.
4. Change the filling mode.
5. Improve mold temperature.
6. Improve the temperature of molten soup.
7. Check the alloy composition.
8. Increased escape may be useful.
9. The vacuum device may be useful.
2). Rift:
Reason:
1. Shrinkage stress.
2. The force of the ejection or the whole edge is cracked.
Improvement methods:
1. Increase fillet.
2. Check for hot spots.
3. Pressurization time change (cold chamber machine).
4. Increase or shorten the time of closing.
5. Increase the draft angle.
6. Increase the ejection pin.
7. Check whether the mold has dislocation, deformation.
8. Check the alloy composition.
3). Stomata:
Reason:
1. The air is mixed in the molten soup.
2. The source of the gas: melting, in the material tube, in the mold, the type of agent.
Improvement methods:
1. Appropriate slow speed.
2. Check whether the flow path is smooth and whether the cross-sectional area is decreasing.
3. Check whether the area of escape is large enough, whether there is obstruction, the location is located in the final filling place.
4. Check if the type of agent is too much spray, whether the mold temperature is too low.
5. Use vacuum.
4). Cavitation Erosion:
Reason: Because the pressure suddenly reduces, causes the gas in the molten soup to swell suddenly, the impact mold, causes the mold damage.
Improvement methods:
Do not change the area of the runner rapidly.
5). Shrinkage:
Reason: When the metal from the liquid solidification to the solid state of the space to become smaller, if there is no metal supplement will form shrinkage. Usually occurs at a slower solidification point.
Improvement methods:
1. Increase the pressure.
2. Change the mold temperature. Local cooling, spray-type agent, reduce mold temperature, and sometimes just change the position of the shrinkage, rather than shrinkage.
6). Peeling:
Reason:
1. Poor filling mode, resulting in overlapping of molten soup.
2. Mold deformation, resulting in overlapping of molten soup.
3. Inclusion oxide layer.
Improvement methods:
1. Switch early to high speed.
2. Shorten filling time.
3. Change filling mode, gate position and gate speed.
4. Check whether the mold strength is adequate.
5. Check whether the pin mold is good or not.
6. Check for inclusion of oxide layer.
7). Ripple:
Reason: The first layer of molten soup on the surface of rapid cooling, the second layer of molten soup has failed to melt the first layer, but there is enough fusion, resulting in different organizations.
Improvement methods:
1. Improve filling mode.
2. Shorten filling time.
8). Holes produced by bad flow:
Reason: The molten soup flows too slowly, or too cold, or the filling mode is poor, so there is a hole in the solidified metal junction.
Improvement methods:
1. To improve the method of cold lines.
2. Check the temperature of the molten soup is stable.
3. Check the mold temperature charge is stable.
9). Holes in the fractal surface:
Reason: It may be shrinkage or porosity.
Improvement methods:
1. If the shrinkage, reduce the thickness of the gate or overflow well inlet thickness.
2. Cooling gate.
3. If the blowhole, pay attention to the problem of exhaust or gas.
10). Burrs:
Reason:
1. The clamping force is insufficient.
2. Mold Clamping bad.
3. The mold strength is insufficient.
4. The temperature of molten soup is too high.
11). Shrinkage:
Reason: The shrinkage occurs below the surface of the pressure.
Improvement methods:
1. With the method of improving the shrinkage.
2. Local cooling.
3. Heat the other side.
12). Carbon deposition:
Reason: The mold is attached to the mould by a free agent or other impurity.
Improvement methods:
1. Reduce the amount of the spray.
2. Increase the mold temperature.
3. Choose a suitable type of agent.
4. Use soft water to dilute the agent.
13). Bubbling:
Reason: The gas coil is below the surface of the casting.
Improvement methods:
1. Reduce air entrainment (same as stomatal).
2. Cooling or preventing low mold temperature.
14). Sticky mould:
Reason:
1. The zinc product is attached to the mold surface.
2. Molten soup impact mold, causing damage to the mold surface.
Improvement methods:
1. Reduce mold temperature.
2. Reduce the roughness of the surface.
3. Increase draft angle.
4. Coating.
5. Change the filling mode.
6. Lower gate speed.