Excerpt from the January 2020 Issue of Global Casting Magazine
The solder defect in die casting affects surface quality and strength, especially in castings with a high seal requirement. The defect could lead to leakage that would mean more wasted cost (Fig 1.). Four aspects of soldering were analyzed, including:
- chemical principle
- mold structure
- release agent
- die casting process
For example, JAC die casting company in Suzhou, China, supplies parts to customers that don’t allow solder to be visible to the naked eye. For a German company in Shandong, China, which produces automobile parts, the solder defect area can be no more than 20 x 20 mm. Another company which produces parts with thin walls and high temperature pouring, have found it is at higher risk for solder defects.
What factors cause the solder defect? What’s the physical or chemical change between the liquid aluminum and hot iron mold? This article will share the results of a study on this defect based on the chemical principle, mold structure, release agent and die casting process.
Interfacial reaction is a series of chemical interactions that occur between the interface of two phases, according to chemical type, content, status and properties.
Solder defect is started by the chemical and physic reaction due to the strong affinity in Fe-Al. A new compound is created when the mold and liquid Al connect closely. The higher the temperature, the more intense the thermal vibration of the atoms, causing the solder ratio to rise and the corrosion of the mold to increase, until finally, it causes the solder area. When polished, the surface containing a thin nitride layer will be destroyed, causing worse cycle. Some data in the study showed that the affinity of Fe-Al will become more serious as the Fe element is decreased, creating more solder.Read More