Welding Tips and Tricks

Up Vs. Down...........why do you get better penetration on uphill vertical vs. downhill vertical ??? Also is the difference in penetration that much ???

You will under normal circumstances get better penetration when welding uphill. How much more depends on gun-angle, amps/voltage settings, travelspeed, etc, etc.

Hi there,

Vertical up is generally considered to be the strongest type of weld, with any process. Because the molten metal wants to run down away from the arc, there is an almost gouge like effect happening. The metal flows out of the pool and exposes fresh metal to the arc.

Where as vertical down you have to race the puddle to get to fresh metal so the depth of penetration is limited due to the high travel speed. Sound welds are easily made with vertical down, but you need to concentrate on not letting the molten metal flow under the arc as cold lapping will result.

In Vertical up welded test joints that i have done, i have seen 10mm (3/8) plates tear along the side of the fillet and on 12mm (1/2) tear the guts out of the plate under the weld. When we broke them on a press.

Mick

Mick sums it up nicely.

MIG up vs. MIG down is a balancing act. It takes finesse to make a MIG up weld look good; It takes almost as much finesse to make MIG down strong.

In MIG up, as Mick says, gravity tends to open a keyhole at the arc, but bunches the molten metal at the low side. In MIG down, you must balance heat, wire speed, and travel speed so the puddle doesn't outrun the arc, or you'll be arcing ON the puddle rather then under it. (This leads to cold-lap and poor to no penetration.)

Steve