Identifying Organic Contaminants in Sub Tier Castings Using FTIR Fingerprinting
Attenuated total reflectance FTIR identifies organic parting agents on raw castings before expensive coating processes fail on customer lines.
Die Casting Contaminants
Meaning
Unwanted substances or particles that enter the molten metal or the mold cavity during the high pressure casting process. Presence of die casting contaminants often results in structural defects such as porosity, inclusions, cold shuts, or shrinkage in the final component. These impurities originate from recycled scrap metal, degraded lubricants, atmospheric dust, or mold oxidation within the foundry environment.
Structural Impact
Internal defects occur when non-metallic particles become trapped in the solidified metal matrix. This interruption of the crystalline structure reduces the tensile strength and the fatigue resistance of the part. If a component for an automotive engine contains such impurities, it may fail under operational stress.
Regular spectroscopic analysis of the melt helps identify the specific chemistry of the pollutants before casting begins.
Surface Interference
External pollutants affect the adhesion of secondary coatings like paint or powder. Lubricant residue or oxide scales on the surface of the aluminum part prevent the coating from forming a chemical bond. This leads to peeling or blistering shortly after the part leaves the production line.
Cleaning steps like degreasing and acid pickling are used to remove these films.
Prevention Protocol
Control of the melting temperature and the use of ceramic filters minimize the introduction of dross into the die. Proper maintenance of the plunger and the spray system reduces the breakdown of oils into carbonaceous deposits. Foundries also implement strict sorting of return material to avoid mixing different alloys.