By kozak
Date 04-23-2012 16:00
Ok well thanks to everyone who helped on my first question my next is equally as novice. Thick aluminum plate is something that we weld often and we are in the middle of a debate as to how we should weld it with MIG or TIG. Plate thickness range from 3/8" to 2" and everything in between (we not only weld the same sizes together we also weld dissimilar sizes together). Previously we had been using a MIG with a spool gun and heated work pieces, but we had a small failure at a customer and we started to question if we should be using a different process. We are using fillet weld joints on just about everything. Thanks for the help.
By 803056
Date 04-23-2012 19:44
Edited 04-25-2012 16:01
Sorry to hear you are welding 6061-T6. Of all the heat treatable aluminum alloys it suffers the most when it comes to the degradation of the base metal properties. The tensile strength drops by about 40% (from 42 ksi to 24 ksi) as soon as you strike an arc and that is if you do everything properly.
As "eekpod" mentioned, if you do not have a qualified WPS you should consider qualifying a WPS so you know what you have. The qualification process gives you an opportunity to work out any bugs in your system. I also agree with "eekpod" that AWS D1.2 is a very useful resource if you are welding aluminum, but it is a code, not a reference. It doesn't explain why you do this or that. For that information there are other references available that are very useful.
If you need to develop WPS for your production work you might consider hiring a consultant that is a SCWI and has verifiable experience welding aluminum. The ability to develop WPSs and qualify welding procedures is one of the job skills of the SCWI as defined by AWS B5.1, whereas it is nice if a CWI has that capablity, but it isn't a skill that is expected of every CWI.
One of my friends defines aluminum as "almost a metal" because of some of its unique properties. It doesn't behave like carbon steel when it is welded or heat treated. If you hire someone to help you develop WPS and to qualify the WPS, hire someone that has a good amount of experience welding aluminum. Remember "it ain't steel".
Best regards - Al