Brown Haze?

Enjoying my PM 205. Tig welding is new to me but so far I am happy with the welder. My question today is regarding a brown haze that was surounding an area I was doing a fillet weld. I was welding 1/8th wall thickness mild steel tubing. I am not sure if the brown haze, kind of a powder around the weld area is a sign of problems with argon flow, dirty steel or tungsten contamination. I did rework the area a bit after initial pass as my penetration was not right. Thanks in Advance ............Wayne.

I think you are dealing with dirty steel. A lot of times you think "new" or unrusted steel is clean enough to weld. But it is not. You'll need to get the mill scale thoroughly removed within 1 inch of the weld area. The brown stuff should be greatly reduced. Improper torch angle can worsen the problem because it creates a vacuum be

Not to be a wise acre but what is a "vacuum be"?

I think he meant "behind the cup", which can draw air into the weld and contaminate your work. Also, the flow rate being to high can make this worse; maybe 5 to 7 LPM depending on your cup size. You want the lowest flow that keep you shielded. Watch out for wind, fans, drafts, etc. Check your pre and post flow; maybe 2 (pre)and 8 (post) seconds. Hope this helps, good luck.

Yes, you are right....somehow something got axed in my statement....lol

Thanks for the tips. I think the steel was not cleaned properly. I have been using the stainless steel brush on my angle grinder for my aluminum welds and wondering if stainless steel brushing is also important for welding mild steel. With my oxy/ace welding I used to do I just sanded the tubing with an 80 grit wheel and all was well. For tig is the stainless brush important like it is for aluminum. Also I am assuming if I use a stainless brush for steel I should keep it just for steel and not share this brush for aluminum cleaning?..wayne

Wayne,
Stainless brushing is not necessary, and actually, post weld brushing with stainless can actually dull the weld finish if the weld is still hot.

What is needed is to grind with either a grinding wheel or flap disc to remove the scale. Mill scale is not easily removed with any brushing. It takes a lot of effort to do so and even though the surface may become shiny, it isn't down to the bare metal yet. Until you see bright silver gleaming, it isn't finished.

Thanks Mark....I was using the brush I spin in my angle grinder that I bought for Aluminum....does this mean I have now contaminated that brush using it on steel and I need a new brush for Aluminum?...wayne

Yes,
I would get another brush for sure.