Due to its rapid development, pressure casting has become the foundry industry. The booming industry sector and important markets, and the growing demand for high-quality die-casting parts, have prompted the die-casting industry to use high-performance equipment, advanced cnc machining process methods, improved die-casting alloy performance, and mold manufacturing. There have been significant changes in areas such as technological progress, but compared with foreign advanced die-casting technology, the overall gap is still not small. For this reason, technological innovation has become the driving force for the development of the die-casting industry.
Improving the quality of die-casting parts to meet the needs of domestic and foreign markets, and constantly discussing the factors that cause the development of die-casting technology to lag behind production development has become a common concern in the current die-casting industry. This article discusses the impact of die-casting mold temperature control in the die-casting process on the quality of die-casting parts. Preliminary discussion.
1 The role of mold temperature control
1) Mold temperature control has an important influence on the temperature, fluidity, filling time, filling flow state and cooling rate of the alloy liquid, crystallization state and order, shrinkage stress, etc.
2) If the mold temperature is too high, the die casting is easy to shrink and form depressions or bubbles on the surface; if the mold temperature is too low, the surface layer of the casting is condensed, and it is broken by the high-speed liquid flow to form surface defects of the casting, which will also cause the shrinkage stress of the casting to increase and cause cracks. .
3) Mold temperature control has a significant effect on extending mold life and improving production efficiency. Excessive changes in the temperature gradient of the mold, the resulting stress state and frequent stress alternation, will lead to premature cracking and deformation of the mold.
4) Mold temperature control has an impact on die casting and dimensional accuracy. The mold temperature is controlled within a certain range, the shrinkage rate of the casting is relatively stable, and the casting can obtain good dimensional accuracy, surface quality and mechanical properties.
2 The main factors affecting mold temperature
1) The pouring temperature, pouring volume, heat capacity, mold volume, casting structure and thermal conductivity of the alloy liquid.
2) The design and layout of the mold gating system and overflow trough, and the degree of adjustment of the heat balance state.
3) Die-casting cycle time and holding pressure time, the continuity of the production rhythm, the faster the frequency, the higher the mold temperature.
4) The way and medium of mold lubrication and heating and cooling.
3. The influence of mold temperature on the properties of die castings
Influence on mechanical properties
Properly increasing the mold temperature can improve the filling conditions and increase the mechanical properties of the die casting parts. However, if the mold temperature is too high, the cooling rate of the alloy liquid will be reduced, the fine-grained layer on the casting will be reduced, the grains will be coarser, and the strength will decrease. The relationship between mold temperature and mechanical properties of aluminum alloy (ZL105) die castings. It can be seen from the figure that for aluminum alloy, when the mold temperature exceeds 250°C, the strength will decrease, and for elongation, the value of the mold temperature below 150°C will gradually decrease.