How to Weld a Vertical Up With Flux Core

Set the welder for the correct heat and wire speed. Normally, steel that is welded vertically up is pretty thick. so there isn't much worry about burning through it. Inside the door that keeps the spool of wire, there is a chart which tells you base levels to set the dials at for each thickness of material. Start there. If you need to go hotter, turn up the levels as you go.

Weld the material. Starting from the bottom, squeeze the trigger on the MIG gun and move across and slightly upward over the surface to be welded. Pause there for a second or two to create more molten steel, then drag the MIG gun slightly upward and across the weld area again. Pause on the other side for a second or two. Repeat this process until the weld is complete. The trick is to move fast enough from side to side that the molten steel does not run, yet slow enough that you get a good fusion. The importance of moving upward diagonally instead of back and forth is so that you do not burn over the previous weld. The slag that builds up on the top of the weld when using flux core will burn into the weld, causing porosity and structural damage.

Clean the weld. The aforementioned slag will have to be removed from the surface of the weld using a stiff wire brush or slag hammer. Once the slag has been cleared away and the surface of the steel has cooled, it is safe to grind away excess material, if necessary, and paint.