Aluminum alloy die-casting molds must be preheated to a certain temperature before use and must always be maintained within a certain temperature range during the production process. The role of aluminum alloy die-casting mold preheating has the following three points:

(1) Avoid premature thermal fatigue failure caused by the “thermal shock” of high-temperature liquid metal to the cold die casting mold, so as to extend the service life of the die casting mould.

(2) Prevent the liquid metal from quickly losing fluidity due to chilling in the mold, so that the die casting cannot be filled smoothly, resulting in defects such as insufficient pouring, cold shut-off, and “freezing”, or even if it is formed, the line will increase due to chilling. Shrinkage can cause defects such as cracks or increased surface roughness in die castings.

(3) The thermal expansion gap in the gap part of the die-casting mold should be adjusted by preheating before production, otherwise the alloy liquid will penetrate the gap and affect the normal production.

There are many methods for preheating die-casting molds. Generally, gas injection, blowtorch, electric heater or induction heating are used.

In continuous production, the temperature of the die-casting mold tends to continue to rise, especially when die-casting high melting point alloys, the temperature rises quickly. In addition to causing liquid metal to stick to the mold, excessive temperature may also cause problems such as deformation of the die-casting parts due to too late solidification, excessive push-out temperature, and stuck moving parts of the mold. At the same time, excessive die-casting mold temperature will slow down the cooling of the die-casting parts, causing coarse grains and affecting their mechanical properties. Therefore, when the temperature of the die-casting mold is too high, cooling measures should be taken. Cooling is usually done with compressed air, water or other liquids.