Welding Tips and Tricks

Good afternoon everyone. I wanted to ask if this is normal. I would make a spot weld on stainless and wait until the post flow has stopped. No matter what there is discoloration around the spot. Even using a #12 cup and gone up to 25cfh. Is this normal?

How thick is the SS and how long is your post purge?
Also are you using a backer?

Poland308 wrote:How thick is the SS and how long is your post purge?
Also are you using a backer?

I think it was 1/8. No back purge, but I want all te way through . Just a surface test

Could be pulling stuff through the puddle. Try a piece of copper pipe hammered flat as a backer.

stainless discolors when its hot and meets air. its not so much cup size or flow but rather time to let the stainless cool down.
if you have a backer thats sucking heat out, you want it quick and hot and let the backer suck the heat out while you keep it covered until its cooled down enough.
its just speed, be real fast. on and off the heat so your not pouring the heat into the metal.

you can see this when the weld is perfect while the post flow is still going but as soon as it stops its colors. sometimes you can tap the pedal/switch to trigger a 2nd post flow.

tweake wrote:stainless discolors when its hot and meets air. its not so much cup size or flow but rather time to let the stainless cool down.
if you have a backer thats sucking heat out, you want it quick and hot and let the backer suck the heat out while you keep it covered until its cooled down enough.
its just speed, be real fast. on and off the heat so your not pouring the heat into the metal.

you can see this when the weld is perfect while the post flow is still going but as soon as it stops its colors. sometimes you can tap the pedal/switch to trigger a 2nd post flow.

I see the discoloration immediately. Even as the post flow is running.

Ant428 wrote: I see the discoloration immediately. Even as the post flow is running.

Bad or no gas coverage. What tungsten stickout are you eunning? Gas lense good? New gas bottle or one you've had no issues with before?

Ant428 wrote: I see the discoloration immediately. Even as the post flow is running.

The discoloration is more lie,lay a result of too high amperage. Postflow won’t remove the heat discoloration if you exceed the needed heat to weld it. If the “spot weld” is clean and not discolored, then your gas is fine. Either a thicker backer, or less amps (just a few) would be my recommendation.

Ant428 wrote:
I see the discoloration immediately. Even as the post flow is running.

i suspect overheating. you may be trying to do the spot way to big.
i'm not sure on the technique for that.

cj737 wrote:

Ant428 wrote: I see the discoloration immediately. Even as the post flow is running.

The discoloration is more lie,lay a result of too high amperage. Postflow won’t remove the heat discoloration if you exceed the needed heat to weld it. If the “spot weld” is clean and not discolored, then your gas is fine. Either a thicker backer, or less amps (just a few) would be my recommendation.

So I lowered the amps to 40. Did a small spot, still discoloration around the spot.

How long are you applying heat when doing the small spot?

Demented wrote:How long are you applying heat when doing the small spot?

2 seconds?

You might have crappy SS or a little bit of contamination in your Argon. Where'd you get that SS piece?

Oscar wrote:You might have crappy SS or a little bit of contamination in your Argon. Where'd you get that SS piece?

Metal supply. I'll grab a fresh one and try again.

I dont do as much stainless as some of these guys but it looks like the brown ring is what you are talking about. I see welds to the side without this brown ring. I weld aluminum and sometimes I see soot from adding filler and the filler rod itself deflecting the gas. Looking at your spots it appears the ring is worse on one side than the other and it reminds me of what is see somtimes. Idk if that helps.

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Just a couple things. Are you cleaning the base metal first? We can't see your torch angle nor arc length, but they always play a part in TIG welding.

Just FYI, I get a light straw ring most of the time, but you are getting a white discoloration as well which indicates perhaps another issue.

Why don't you try shortening the stickout, even with the #12 cup, to just 3/16-1/4", use a gas flow of about ~1.8x cup size, and hold a fixed arc length of 3/4 to 1 tungsten diameter (don't eyeball it, make sure!), and hold the tungsten perfectly normal (perpendicular from all directions) to the base metal. At this point you have you will have eliminated several variables [torch angle, arc length, stickout] to narrow down your issue. I would also wire brush it with a small "toothbrush" SS wire brush, and wipe it with acetone. Make sure your tungsten is clean as well. It should be clean, a bit shiny, free of oxidation (not dull):




It might be obvious to us, but just to make sure, your tig torch including the collet body, collet, and cup should be clean and not oily/greasy/etc. All this stuff is no bueno for TIG welding.


You should also soap your joints to see if you have leaks, as they can obviously be detrimental.