Hello All

I'm looking for information on tandem welding. I'm doing a T.R. (Technical Report) on SAW vs Tandem welding for National Steel Car.
I'm trying to determine if a tandem GMAW processes would outperform SAW and if so, if the costs would make it feasible. This process involves running two GMAW torch in tandem.
The first torch lays down the root pass, and the second torch washes the rest of the joint. I was thinking of using a solid wire to do the root and to lay down some initial filler metal. The second torch would use FCAW or MCAW process to wash the joint.

Any information/input would be appreciated
Any thoughts?