GMAW

Date 03-04-2007 18:44

Hello monsoon12, a brief explanation goes something like this: welding process can have an effect on directional choice, GMAW/short arc process generally will look better and possibly attain better weld performance by using the forehand angle, yet in many instances the backhand method will provide better penetration and more weld buildup as required. GMAW/spray process can be used in either a forehand or backhand method depending on joint configuration, material thickness, wire diameter, and possible a few other variables. Since the forehand method in this process yields less penetration and flatter and wider bead profile it is better suited in many cases for thinner materials or instances where over-penetration is an issue. On the other hand the backhand method can be used to lay down more weld metal, provide deeper penetration, and possibly provide better bead profile when trying to run oversized fillet welds for given wire diameters. The mechanics of the various wire-fed weld processes will be affected by using the forehand/backhand methods in similar ways, forehand/ wider beads, less penetration, backhand/ narrower beads, greater pentration(when bead oscillation is only in a straightline to bead direction, no side to side, circles, or other width enhancing motion.).
FCAW is where the forehand/backhand methods can be seen in a way that can be detrimental to weld bead performance, in some instances when the forehand method is employed it can trap slag at the root of weld while performing groove welds or fillet welds, this will not always occur, however the likelyhood is far greater than if a similar weld were performed with the backhand method, operator skill and experience can affect this also. There will likely be other responses which differ from the ones that I have offered here. You should use your own judgement and experience to decide what works for you. As long as your welds conform to the requirements of the jobs at hand you'll do just fine. My $.02. Regards, aevald

By jarsanb (***)

Date 03-05-2007 16:22

It really depends on the application. Obviously if you are welding open root groove welds then a drag angle is the prefered method. Beyond that you would use whatever the joint is asking for, assuming you have an understanding of the different techniques. On multi-pass situations you will be saving yourself time more often than not by taking advantage of the drag angles. It will fill a joint faster than pushing. If your filler passes haven't left much room for an easy, visually pleasing cap, then you would use the push technique to keep the cap height down (in the flat and horizontal positions). As far as single pass fillet welds, you can manipulte the parameters to fit whatever you want. Typically you would run slightly higher voltages at a given wire feed speed for a drag technique over a push and vise versa. Our company uses GMAW for all of our pipe welding including fittings and backhand is used probably 20:1 over a push in the flat and horizontal positions given the nature of the fittings and joints. Again, joint design and parameter settings will dictate the method used - both can produce high quality welds.

By yorkiepap (***)

Date 03-05-2007 19:56

Hey monsoon12,
I agree with both aevald and jarsanb regarding both parameters of MIG. I use both applications, and as stated, for penetration...drag, for appearance and thin metal...push. I believe that if you learn both procedures, you will be a much better welder with the MIG process. We have certain jobs that I have to do that a vertical down is necessary and it becomes a drag technique on one side, and a push technique vertical up on the opposite corner. Also, you will find the torch angle will really help you if you prefer "push", maintain almost 90deg, as that will increase penetration. Since 90% of our material is <.125, I use the push method except for the aforementioned angle welding. Anyway, I feel that if you take some time and some scrap and do some practicing, you will get quite proficient with both.....Denny