1. Description of cold insulation
     The characteristic of such defects is that the surface of the casting is irregular, such as wrinkling or cold layer. The most common reason is that during the filling process, two metal liquids with lower temperatures and velocities meet. When two streams of molten metal converge, if gas is drawn in, it increases the likelihood of such defects occurring. This type of defect may also occur at the end of the filling process (Figure 1), which is also known as insufficient pouring. This type of defect has different names, such as cold insulation, cold filling, cold seam, and fusion mark. The appearance of these defects may vary slightly, but the root cause is usually similar.

2. Simulated interpretation

    Detailed analysis of metal liquid filling temperature and speed through visual filling process. The initial filling temperature result (basic criterion) shows the temperature at which the metal liquid reaches a certain surface. If the critical temperature is lower than the liquidus temperature of the alloy, solid phases will be generated in the molten metal, and the viscosity of the molten metal will increase. Even at relatively high temperatures, if the metal liquid flows at the front or has a low velocity and high pressure at the end of filling, similar defect characteristics will still be displayed.

3. The fundamental cause of cold insulation
Low surface temperature of molten metal or mold
The velocity of the first and/or second stage of the injection curve is relatively low
Switching position lag between high and low speeds - pre filling
Less opportunity to clean/wash the area
The design of gate position leads to uneven flow of molten metal
Gas is entrained at the forefront of the flow of molten metal