Die casting alloy pouring temperature
The pouring temperature of a die-casting alloy refers to the temperature of the molten metal when it is transferred from the furnace to the die-casting machine’s pressure chamber. It is one of the key parameters in the die-casting process that determines the molten metal’s fluidity, filling capacity, and the solidification quality of the casting. The suitable pouring temperature range varies significantly for different die-casting alloys. For example, the pouring temperature of aluminum alloys is typically between 650°C and 720°C, while the pouring temperature of zinc alloys is relatively low, generally between 410°C and 450°C. This temperature range is not set arbitrarily but is determined based on the alloy’s melting point, fluidity curve, and the structural characteristics of the casting. If the pouring temperature is too high, the molten metal will undergo increased oxidation, generating excessive slag. This will also increase the heat load on the mold and shorten its life. If the temperature is too low, the molten metal’s viscosity will increase and its fluidity will decrease, making defects such as under-pouring and cold shut more likely to occur, affecting the quality of the casting.
The stability of the pouring temperature has a direct impact on the consistency of casting quality. During the continuous production process, if the pouring temperature fluctuates too much, the fluidity of the molten metal will fluctuate, which will cause obvious differences in the filling state, solidification shrinkage, etc. of different batches of castings, increasing the scrap rate. In order to ensure temperature stability, modern die-casting workshops usually use a holding furnace to control the temperature of the molten metal. By monitoring the temperature in the furnace in real time and automatically adjusting the heating power, the temperature of the molten metal is maintained within the set range. In addition, the temperature loss of the molten metal during the transportation process also needs to be taken into consideration. For example, the transportation distance from the holding furnace to the pressure chamber, the insulation performance of the transportation pipeline, etc., will affect the final pouring temperature. Therefore, in actual production, it is often necessary to increase the set temperature of the holding furnace by 5°C to 10°C to compensate for the temperature loss during transportation and ensure that the molten metal reaches the ideal temperature when entering the pressure chamber.
Pouring temperature is closely related to the microstructure and mechanical properties of a casting. When the pouring temperature is too high, the cooling rate of the molten metal within the mold cavity slows down, resulting in coarsening of the grains and a reduction in the strength and hardness of the casting. Excessively high temperatures can also cause defects such as shrinkage and cavitation, reducing the density of the casting. Conversely, if the pouring temperature is too low, the molten metal begins to solidify during the filling process, forming fine grains. However, this can also lead to a high number of pores and inclusions within the casting due to insufficient filling. For example, when the pouring temperature is controlled at around 680°C, the casting achieves an optimal balance between tensile strength and elongation. Increasing the temperature to 730°C reduces tensile strength by approximately 5% to 8%, while decreasing the temperature to 640°C significantly reduces elongation. Therefore, precise control of the pouring temperature is crucial to ensuring that the mechanical properties of a casting meet design requirements.
In actual production, the setting of the pouring temperature needs to be optimized in coordination with parameters such as the injection speed and mold temperature. For example, for thin-walled complex castings, in order to compensate for their rapid cooling rate, it is usually necessary to appropriately increase the pouring temperature to enhance the fluidity of the molten metal and to ensure that the cavity is full with a higher injection speed; while for thick-walled castings, the pouring temperature can be appropriately lowered to reduce the risk of coarse grains, while at the same time, a lower injection speed can be used to avoid air entrapment. In addition, the mold temperature will also affect the choice of pouring temperature: when the mold temperature is low, the pouring temperature needs to be increased to prevent the molten metal from cooling rapidly; when the mold temperature is high, the pouring temperature can be appropriately lowered to balance the thermal state of the entire process system. This coordinated adjustment of multiple parameters can effectively improve the stability of casting quality.
With the development of die-casting technology, the control methods for pouring temperature are becoming increasingly intelligent. Some advanced die-casting production lines have achieved online monitoring and automatic adjustment of molten metal temperature. By installing an infrared thermometer at the entrance of the die-casting chamber, the molten metal temperature is fed back in real time and transmitted to the control system. The heating power of the holding furnace or the molten metal delivery rhythm is automatically adjusted to ensure that the pouring temperature is always within the optimal range. At the same time, combined with big data analysis technology, statistical analysis of casting quality data at different pouring temperatures can be performed, continuously optimizing the temperature setting range and achieving continuous improvement of process parameters. This intelligent temperature control method not only improves production efficiency but also provides strong support for the precision and digitalization of the die-casting process, promoting technological upgrades in the die-casting industry.
