MIG Vertical up vs Vertical down

Date 01-26-2001 17:39

Typically the Vertical Up will provide deeper pen. Gravity is one factor. The upward movement allows the welder to provide a higher heat input into the weld. Whereas in a downward movement, the pool tends to follow gravity. This would be true even with the all position wires.
Of all the welder certifications I have witnessed for this position, the test is given in Vertical UP.

By John H. UK (*)

Date 01-27-2001 00:31

Vertical Up is usually much quicker to get the hang of I've found and because the work is usually below you, or mine is I'm not sure about your's, the arc is more visible. Rather than welding downwards covering it with the torch as you go. I weld from side to side horizontally if I can because I find it much easier to keep it moving smoothly. I usually rest my hand on the work and guide the torch along, a habbit I regret when it gets a little too close for comfort and my glove begins to steam or catches alight!
The heat going in depends quite a lot on the direction you have the gun as well as it's angle, your backhand (Pull) and forehand (Push) welding. If you point it the way you're moving, push, then you can put a lot of preheat into the area just infront of the arc by tipping your gun by about 30 - 40 degrees into the work, so the wire makes a smaller angle with the work. The smaller the angle on the gun, the less heat infront of the arc but more on one spot. So for big long seams you would need to angle the gun, I do anyway. If you pull the gun you will put a lot less heat infront of the arc and angling it into the work, so it's more horizontal with the work, now will just heat up the weld you're leaving behind the torch as you go.
I'd just have a muck about on some scrap bits the right size and you'll find the angle you need pretty quickly. Remember that if the real thing is massive compared to the bits of scrap you'll proberly have to end up putting lots more heat in because, obviously, as you increase size there is more metal to soak up the heat.

By boilermaker (**)

Date 01-28-2001 00:32

For me welding MIG, actually FCAW I keep the arc straight into the parent metal, but with outside winds, keeping the nozzle
straight into the metal reduces the chance you'll get porosity. And keep in mind, with vertical up, you can bury your arc
length with your wire speed where it almost pops constantly and really digs or you can put a smoker on there...it just depends
on what you want.
The Bridge used to give a vertical down stick, but I hardly doubt that too many companies give a vertical down mig.

John

By Chuck Date 01-28-2001 02:10

I have seen (and done) GMAW welding in vertical joints as follows: run root pass downhill (short-arc). This avoids excessive I.D. penetration and burn through. Weld the balance of the joint out with ether GMAW (spray or short arc) or SMAW. Bevel the root with no land, when welding the root, use a slight weave to tie-in both sides of the bevels. F.Y.I.: I have witnessed and continue to witness many welder performance tests where vertical progression is "downhill" for API-1104 pipeline work as well as in-plant ASME B31.3 process piping. Depending on the base material tensile strength, SMAW carbon steel electrodes use for this are typically E6010 or E7010.

By 357max

Date 02-06-2001 14:27

Whichever direction used, keep the electrode at the leading of the molten weld puddle. Remember if it is too "hot" and fluid, decrease the wire feed speed. That voltage control will change volts which will control the height and width of the weld deposit. Not the penetration!!

By YumpTTC (*)

Date 02-19-2001 04:56

I weld with an esab 250. I am welding 1/4 in plates. going vertical up, I run my esab's heat settings on medium, 2 and I use a wire speed of 3 1/2 to 4. Running this weld, I hold about 1/4 to 3/8 inch out of the joint for a count of 2, then slowly move to the other side the same distance away from the joint. Hold for a count of two and then move over and above the last puddle that is on the other side. I run this second puddle halfway on the last puddle and halfway on the parent metal. This is a structural weld and will produce very good penetration. With the flux core, I have heard, it is best to drag or pull the stinger. With "hard wire" use a pushing motion. This is a bit difficult to utilize when you dont have room to change angles of your gun. Therefore, I run this weld with the stinger facing straight ahead.