Summary for laser welding chem film Discussion
laser welding 4047 aluminum that has been chem film finished per MIL-DTL-5541 class 3 is best handled by welding before the conversion coating, according to Dan Miller. He says the ideal sequence is to weld first and apply chem film afterward; if the part must remain coated, the weld area and possibly nearby surfaces may need to be re-coated. Miller notes that the chem film can begin to break down around 150-200° (as he recalls), so heat from welding is a concern. If the part does not need to stay coated, he sees no major welding problem beyond possible fume generation. He also cautions that chem film is easily scratched, so minimizing post-coating handling and operations is important.
Q. Are there any problems when laser welding 4047 aluminum that has been chem film finished per MIL-DTL-5541 class 3?
Dan Miller
welder – San Jose, California, USA
June 5, 2012
A. Ideally you’ll want to do the welding prior to chem film. At best case, you’ll will now have to go back in and apply the chem film to the weld, and perhaps the surrounding area (the chem film will start to break down at around 150-200° if I correctly recall). This is, of course, assuming that your part requires the weld to be coated.
If it doesn’t need to be coated, then I can’t see any problems with welding, other than perhaps fume generation.
Chem film is also easily scratched, so I’d want to limit the amount of post coating operations as much as possible.
Marc Green
anodizer – Boise, Idaho
June 9, 2012