Weldability of 6061T6 Alum. to 319F Alum

By Richard Date 09-14-2001 14:27

I was wondering if any information was available on the weldability of 6061T6 aluminum to 319F aluminum using welding rod #4043 aluminum?. What I would specifically like to know is if there is any known allowable shear stress for fillet welds using these two materials with the subject weld rod?. As you may have guessed we (the City of Cincinnati) already have an existing condition in which this process was performed. I was wondering if the existing sign connections could be strenghthened by adding extra fillet weld, or if the weld has absolutly no guaranteed structural value and the entire connnection needs to be reworked. I was not able to find any information regarding the weldability of these two materials in the Aluminum Design Manual, which leads me to believe that they are not weldable. The contractor, of course, insists that they are weldable.

By GRoberts (***)

Date 09-14-2001 15:10

I am not familiar with the 391F material, but at a company I used to work for, we welded 6061-T6 aluminum by the mile. It is a very weldable alloy. As far as strength goes however, in the T6 alloy (the T6 stands for the heat treatement, which happens to be solution heat treated and stabilized) the weakest part of the metal is not the filler (4043 is a recommended filler for 6061-T6), but the heat affected zone of the base metal. The heat from welding significantly softens the base metal. The question that would be most important to me in your situation, is was the contractor using a qualified aluminum welding procedure. AWS has an aluminum welding code (D1.2) that anybody purchasing welded aluminum structures should specify that contractors must qualify welding procedures to before the project even goes out for bidding. Unless of course it is covered by another code, such as ASME, ABS, etc.