The main reason for the cold insulation of Color Coated Aluminum Coil is that the meniscus area on the surface of the condensing plate is cooled strongly, which causes the alloy liquid in this area to solidify too fast. Therefore, all measures that can reduce the cooling effect of the condensing plate are conducive to reducing or eliminating the cold insulation defects.

1. Reduce the cooling intensity of the condensing plate

The cooling intensity of the condensing plate is mainly affected by the cooling water flow rate of the condensing plate, so reducing the cooling water flow rate can reduce or eliminate the cold insulation defects. Of course, reducing the cooling strength of the condensing plate will make the semi-solid support layer thinner, which may cause it to “ ***” or “collapse” and mix with alloy liquid after leaving the support of the condensing plate, so the reduction in cooling strength is limited.

2. Raise pouring temperature appropriately

According to relevant theories of metallology, the higher the temperature of molten metal, the lower its viscosity, that is, the better its fluidity, and the surface tension also decreases with the increase of temperature, thus reducing the additional pressure and hindering the formation of cold insulation. Therefore, properly increasing the pouring temperature is conducive to eliminating the cold insulation defects. However, increasing the pouring temperature will slow down the crystallization speed of the alloy, cause coarse grains, and cause segregation nodules on the outer surface of the casting blank. Therefore, it is also limited to eliminate the cold insulation defects by increasing the pouring temperature.

3. Set up thermal insulation layer

The fluctuation of the liquid level in the crystallizer will increase the contact area between the alloy liquid and the condensing plate, thus increasing the degree of cold separation on the surface of the semi-solid support layer. In addition, in order to improve the stability of the interface bonding of the multi-layer casting blank, the thickness of the semi-solid support layer when separating from the condensing plate is required, and the solid phase ratio and the surface temperature are as stable as possible. Under the condition that the blank drawing speed is constant, the height of the cooling section of the condensing plate must be fixed, so heat preservation materials are installed on the cooling surface of the condensing plate to form a heat preservation layer.

4. Increase the liquid level in the crystallizer

Increasing the height of the alloy liquid level in the crystallizer can ensure the heat supply of the metal liquid near the condensing plate, and can also increase the static pressure of the alloy liquid to offset the effect of additional pressure, thus being beneficial to reducing or eliminating cold insulation. In addition, increasing the liquid level can also buffer the speed of newly poured alloy liquid and reduce its impact depth, which will improve the effect of gate on uneven temperature distribution of alloy liquid in the crystallizer.

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