摘要
本文主要讨论模铸件缩孔和缩松的缺陷类型，以及针对这些缺陷的防治措施。缩孔是指在铸造模具中注入金属时由于金属熔温略降，模芯和模沟与金属之间的附着力不足引起的缺陷。缩松是由于模流的不同速度使金属在模具内的部位出现滑动的现象。将有助于减少熔温对金属的硬度的影响，提高模流的流动速度，防止金属复合以及使用冷却也有助于减少这些缺陷的形成。
Introduction
Die casting has become a rapid and cost-effective manufacturing process for large quantities of small metal parts. However, like other molding processes, defects occur during die casting, among which shrink hole and shrinkage are common defects. Shrink holes and shrinkage in die casting can cause problems, including poor mechanical properties and decreased fatigue life. Therefore, it is important to identify the defects and their causes and take preventive measures to reduce the occurrence of defects in die castings.
Shrinkage and shrinkage in die casting
Shrinkage and shrinkage are two common defects of die castings. Shrink hole is a defect caused by the decrease in metal solidification temperature and the insufficient adhesion between the core and cavity of the casting mold and the metal. This defect mostly occurs near the outer surface of the casting, which can weaken the mechanical properties of the casting. Shrinkage is the phenomenon of metal sliding within the mold due to uneven flow rate of the metal. This phenomenon usually occurs in the bottom of the casting, resulting in rough surface or other defects.
Prevention and Control
In order to reduce or prevent shrinkage and shrinkage in die castings, the following preventive measures can be taken.
1. Reduce the influence of temperature on metal hardness: The hardness of metal is related to the solidification temperature of metal. Therefore, the decrease of solidification temperature can help to reduce the occurrences of shrinkage and shrinkage. This can be achieved by thermal insulation measures such as increasing the filling temperature of metal or increasing the pressure of the injection system.
2. Improve the flow rate of the metal: It is necessary to improve the flow rate of metal inside the mold to reduce the risk of shrinkage and shrinkage. The most effective way is to shorten the injection time and increase the flow rate of metal.
3. Prevent metal composite: Metal composite is also a factor leading to shrinkage and shrinkage, so efforts should be made to reduce metal composite. This can be achieved by reducing the germination time of metal, adding flow aids such as wax and paraffin, and using lubricants to reduce the difficulty of metal composite.
4. Using cooling: Adopting cooling measures can reduce the number of defects, because cooling can improve the thermal conductivity of the inner and outer layers of the casting and reduce the thermal stress in the casting. However, too much cooling can damage the casting surface, so it is necessary to adjust the cooling time and cooling rate of each part of the casting accordingly.
Conclusion
Die castings often have shrinkage and shrinkage defects due to their particular casting process. Therefore, it is necessary to take preventive measures to reduce the occurrence of these defects. The prevention and control measures described above can reduce the occurrence of shrink holes and shrinkage defects in die castings.
