vertical GMAW

By welder_guy2001 (***)

Date 06-29-2002 02:40

i would weld on 1/8" plate downhill. 1/4" and thicker uphill. remember that gravity is your enemy in vertical positions. you need to put less filler metal into the weld bead, and it needs to be a little bit cooler. to do this, decrease the voltage about 1 volt (if you have a dial that will tell you how much of a turn 1 volt is) and turn down the wire feed speed until you get a nice steady crackling sound kinda like bacon frying in a pan. angle the gun upwards about 15 degrees for uphill or downhill. when welding uphill fillets move in a Christmas tree kinda pattern...start at one side of the joint and pause (about 1/8" from the intersection of the 2 pieces) then move up about 1/8" into the intersection to melt into the root, then move to the other side of the joint and pause. make sure each series of steps is about 1/8" above the previous step.

don't just weave straight across the joint because w/ MIG it tends to have less penetration than most other kinds of welding. every time you move up out of the puddle into the root with the arc you're ensuring you have full penetration to the root by melting it. and every time you weave out to the sides you're helping to spread out that bead by heating up the sides of it so it doesn't sag. so it's always good to pause on the sides. your pauses should only be a little less than a second. if you still have sag, try turning your wire feed speed down...could be that too much metal is going into the bead.

and personally, i've always found that the settings i use for 1/8" steel in the flat position is usually a good setting for 1/4"-3/8" steel in vertical up. but the only way i found that out is by messing w/ my settings and techniques.

as for downhill, just make sure your arc is ahead of the puddle...if you can't keep up w/ the puddle, or it's crowding the arc, reduce the feed speed and maybe the voltage too.

and remember....downhill welding doesn't heat up the metal as much as uphill welding. you don't need that much heat for 1/8" steel...but you need a lot for 1/4" and thicker. use your best judgement.

By Goose

Date 06-29-2002 02:52

Thanks for the reply. I simply weld in my home/race workshop. My next project is to build a large flat open car trailer using 2" x 4" box tubing, 3/16" wall thickness. I'll have to use your info as a guideline and see how it goes...this will have many vertical welds. I'm assuming I'll be welding up with 3/16"?

Funny you mention the heat reduction needed with the Mig. I've found with my Tig that inside corner, not specifically vertical, fillet welds typically need more current/heat for the same penetration as a butt weld of similar thickness materials.

I'll have to try the "tree" weave pattern...I typically will use a small "zig-zag" pattern, but I see your point about limiting the time the torch is over the root of the weld where it could be pulled down by gravity.

...very interesting:)

Thanks
Todd
http://www.malibumotorsports.cjb.net

By overthehill (*)

Date 06-29-2002 14:45

Hey Goose,

You are talking about GMAW with ER70S6 solid wire and 75/25 shielding gas? Let us know your results welding up hill on 3/16" metal. I was always told that GMAW uses a vertical downhill procedure.

By welder_guy2001 (***)

Date 06-30-2002 00:12

GMAW is an all position process w/ short circuit transfer mode. a lot of heavy steel welding is done w/ spray transfer, but most little shops and little welding machines are only set up for short circuit transfer. you can weld overhead, up, down, horizontal, flat...anything. it's all a matter of how the machine is set up. just like stick welding-- you can't weld w/ the same amperage in vertical up as you can w/ flat. you have to turn the heat down, and the wire feed speed.

By welder_guy2001 (***)

Date 06-30-2002 00:08

3/16" is actually where i'd draw the line for welding uphill vs. downhill...3/16" is too thin to weld uphill, so go down.

how much heat you need to put into a weld to get the same amount of penetration depends on which direction you go. if you go down hill you have to put in more heat because you have the puddle riding so close to the arc and if you're not careful, the arc will actually be striking directly on top of the puddle, which is bad. you want the arc to be striking somewhere between the very tip of the melted edge of the puddle to the middle of the crater formed by the heat.

as for uphill, heat rises and the puddle always wants to droop away from the arc, so there is no need for all the heat. but you don't want too little heat because that will also cause your puddle to sag in the middle. play around w/ it for a while by setting up your machine for 1/8" and then weld some 3/16" downhill, or 1/4" uphill. also, your beads for an uphill weld shouldn't be as big as a weld you'd make in the flat position because the surface tension of the hot steel can only hold a certain shape at a certain size. kinda like a drop of water...you can squeeze out a little bit of water from an eye dropper and it won't fall till you squeeze out enough for the surface tension to give way to gravity.

By overthehill (*)

Date 06-30-2002 05:36

Welder Guy is right, downhill. These are probably the easiest welds, too.
Make sure the metal is clean and free of rust. On butt joints, bevel the edges to ensure penetration. If you tack up without beveling, use a grinder, up on edge, to groove the joint. For outside corners, butt the inside edges of the two pieces together, sort of forming a bevel. Makes a very nice weld. You can even leave a slight gap for max penetration. Inside corners, just go for it. Keep the voltage/wire speed relatively high. Tune up the wire speed and voltage. It's simple, if you don't know how, ask. Use a 1/4 to 3/8 wire stick out from the contact tube to the metal (technically it's to the top of the arc, but that's nit pickin)This is important, on downhill, always keep the arc (squirt the wire) on the leading edge of the puddle. Definately take a few minutes to practice and set the machine up. Try breaking some of your practice welds so your confident it's working. Run as high of a voltage setting as you can handle the amount of weld build up. Manufacturers recommended settings are typically a little cold, and my MM250 runs 2 to 3 volts lower than indicated by the dial. What your attempting to do works, and actually, it's a lot of fun.