In the process of die-casting production, the high-temperature metal solution is pressed into the mold cavity and cooled by the heat exchange with the mold. The die-casting mold should absorb the heat brought by the high-temperature metal solution and dissipate heat through the space and the die-casting machine. Generally, the heat absorbed is greater than the natural heat dissipation. Therefore, the mold temperature will gradually rise with the progress of the die casting process. If the mold temperature is too high, it will affect the casting quality and mold life. In order to carry out normal die-casting production, the mold temperature must be kept basically constant.
The commonly used cooling methods include: extending the die-casting cycle, spraying release agent or coolant or opening a cooling channel in the mold to cool with cooling water. Prolonging the die-casting cycle will reduce the production efficiency, and the effect of spraying release agent or coolant is limited. Therefore, water cooling becomes the main method of mold cooling.
At present, the cooling water of die-casting mould is mostly directly connected into the mould for heat exchange with the mould. Among them, foreign die-casting enterprises mostly use special chillers for cooling large and complex die-casting molds, with high temperature control accuracy, while domestic enterprises generally use tap water directly for cooling, so the accuracy of mold temperature control is very poor. Although the direct water cooling effect of the mold is very good, due to the heat exchange formed by the direct contact between the water and the mold, it has a great thermal impact on the mold, and it is very easy to form small microcracks inside the mold. If the microcracks penetrate the mold surface, it will affect the casting quality and mold life.
If the method of inlaying cooling water pipe is adopted, although the direct contact between water and mold is avoided, there is always a gap between the cooling water pipe and mold, and the air in the gap is equivalent to forming an insulation layer, which will seriously affect the heat transfer, resulting in poor cooling effect. This is also the main reason why direct water cooling is mostly used in die-casting moulds at present.
At present, the cooling pipes are used in the following ways: fixed-point cooling, linear cooling and circulating circuit cooling.
Generally speaking, the casting inlet, diversion cone, core-pulling and parts with thicker wall thickness adopt fixed-point cooling, while the cooling of the whole mold mostly adopts linear and circular cooling. For the core needle part on the mold, the best cooling method is to use the fixed-point cooling method based on high-pressure circulating water.
The advantages of this fixed-point cooling process based on high-pressure circulating water are:
① Simple structure, good cooling effect, low processing cost and convenient processing and maintenance.  
② It is very effective to adjust the temperature gradient after mold testing, and can be added and adjusted at any time.  
③ It can effectively control the distance between the cooling point and the surface of the mold cavity, thus effectively controlling the mold temperature.