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5 Reasons of Cold Shut of Aluminum Die Casting Parts

5 Reasons of Cold Shut of Aluminum Die Casting Parts

5 Reasons of Cold Shut of Aluminum Die Casting Parts

1) What is the cold shut of aluminum casting parts?

  The gap where metal flows butt or overlap but not merge is called cold shut. The main feature is the obvious, irregular, and sunken linear lines, the shape is small and narrow, and some junction edges are smooth and may be broken. The area where the cold shut occurs in aluminum alloy die castings are usually the area far from the gate. It is due to the fact that when the metal flow is divided into several strands, the flow front of each strand has been in a condensed state (called the solidification front), but under the push of the subsequent metal flow, it is still filled. When the metal stream that it meets also has a solidification front, the solidified layer that meets can no longer be fused, and the joints appear gaps. Severe cold shut has a certain hindrance to the use of castings, which should be determined by the use conditions of the castings and the type of cold shut.

2) Why the cold shut will be caused in aluminum die casting parts:

  • The molten metal pouring temperature is low or the mold temperature is low.

  • The alloy composition does not meet the standard and the fluidity is poor.

  • The molten metal is filled in separate runners, resulting in poor fusion.

  • The gating design is improper and the filling process is too long.

  • Low filling speed or poor exhaust.

3) How to improve the cold shut:

  • Properly increase the pouring temperature and mold temperature.

  • Change the alloy composition to improve fluidity.

  • Improve the gating system, increasing the speed of the inner gate, and improving the filling conditions.

  • Improve the overflow conditions and increase the overflow flow.

  • Increase injection speed and improve exhaust conditions.

  • Increase the specific pressure.

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