Posted 02 July 2009 - 11:48 PM
I'm guessing from your information that you are using solid cored wire, with gas shielding. No internal shielding in the wire (aka Dual Shield). If you are using true GMAW wire, and not FCAW with a gas backing; I have to break it to you that this stuff was NEVER intended to be welded overhead. If you look at the roll of wire, it will clearly state to be used in postitions 1g, and maybe 2g. That means flat, and vertical, and the vertical is doubtful. GMAW is a shop wire, and just isn't designed to do that job.
The good news is that you "can" eventually weld overhead with it. It is just going to take some time, and practice. The most important thing you can do is develop a deeper push angle, meaning lay the tip of the gun flatter, or more parallel with the piece you are welding. Try to be about 50* from parallel with the work piece. This will prevent the molten metal from clogging you nozel. Also, crank a little more amperage, or reduce your wire speed. This will allow more wire stickout, and you will actually be arcing (welding) further away from the nozel. Trying to emphasize that wire stickout will help. By that I mean set the machine to where it is actually welding nice while your gun is further away from the steel, and then really pay attention to how close your nozel is to the metal. You are going to want to move quicker than you would when welding flat, as you will accumulate a convex puddle quicker because gravity. Try drawing little circles with the tip of the wire, and pushing out of the puddle the same way each time. That will allow your weld puddle to cool, while you are moving aways from it, then as you return to the puddle your weld will fuse your existing puddle, and what you have just done.
Other tips that would be helpful are to make sure the steel is very clean. GMAW REALLLY needs clean metal to work. You aren't running enough amps to burn through dirty crap like with other forms of welding, so cleanliness is extremely important. Also, when grinding the metal, you can't have the area being welded too coarse. It helps immensely, especialy overhead, and vertical. It is just that much easier for the steel to stick. Ground placement is also important. Place the gound away from you so that the current has to flow towards that ground. It helps on a molecular level to keep all that energy working in your favor.
Hope this helps, and good luck!