In the die casting process, porosity is a major issue and implies the defects in the material used. Porosity affects the structural integrity of a part and weakens the material, making it less functional. However, it does not always necessarily mean the material has defects and it can be corrected by adopting some changes into the whole process.
Porosity within metals is the result of voids, air pockets, and holes found in its surface. This occurs mainly due to the trapping of air by the machinery of the die cast process, which leaves gap at the die or mold filling. The air used to force the molten metal into the mold is also a cause for porosity, as it remains without exiting the chamber through vents and overflows.
Causes & Prevention
There are yet many other causes of porosity in die casting process such as the design of the mold, cast parts, purity of the metal, low metal temperatures, pressure and speed of the machines, etc. Checking for porosity in materials is done through X-Ray scans, computerized tomography, and inspecting the inside by cutting the material.
Die casters have successfully tried many methods to prevent the porosity of materials in the die casting process. Creating an efficient die casting process is one way to reduce the chances of porosity in materials and thereby ensuring its quality. Using high quality materials is vital in the process along with adequate maintenance of the equipments.
Melting the material in vacuum or using a low solubility gas such as Argon is an effective way to prevent the formation of air bubbles inside the casting. This is technically known as avoiding gas porosity. Proper de-gassing after melting or filtering prevents oxide formation, which is yet another cause of porosity.
Proper cooling ensures reducing metallurgical defects like hot tears and hot spots on the material. Adjusting the cooling practices by adding more die spray or localized cooling channels is done, if the hot spots persist.
Dealing with Defects
Porosity involves the formation of holes and voids in a casted material. These defects arise due to three common facts like the design, material used, and the manufacturing process. However, the various defects may or may not have an impact on the overall quality and efficiency of the material.
Quality die casting companies have strict reviewing process that detects any such defects. It is instrumental in determining all the properties of the flaw to find the best solution in resolving it.