# Welding stainless steel



## Just for fun (Jul 7, 2021)

So playing around with some unknown Stainless steel.  I have welded some thicker stainless steel before without any issues, ok well at least without the black blobs on the backside.   I don't have any way of purging the back side.   But what is causing those big dark lumps?  I didn't keep track of the exact amps I was using.  But low amps between 35 and 50 amps.  1/16" materal, 1/16 tungsten,  #6 cup, 15 cfm argon and 1/16 filler rod.

Front side



Back side



35 Amps no filler rod



Back side, no filler.
	

		
			
		

		
	




Tim


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## 682bear (Jul 7, 2021)

The lumps on back are where the puddle melted through the thin material and formed a bubble under the material...

Caused by either too many amps, or moving too slowly, or both. Either way, there was more heat applied than the material could handle.

-Bear


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## erikmannie (Jul 7, 2021)

I don’t have very much experience with welding stainless, but my guess is that the black is oxidation due to oxygen (from the air, obviously) present back there while it was hot.

Try welding with the weldment very flat (e.g. clamped down) against a welding table, or figure out a way to purge the back side.

I use a dual argon flowmeter for backpurging Ti:









						SPARC Dual Output Argon Flow Meter & Regulator CGA580
					

Dual Argon Flow Meter & Regulator by SPARC available for purchase today. Perfect for MIG and TIG Welding. The pressure gauge goes from 0 to 4000 psi. The output flow is adjustable from 0-60CFH. The tank input fitting is a CGA-580 style, so it fits all argon, helium, nitrogen, and argon/CO2 mixed...




					sparcwelders.com


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## jwmelvin (Jul 7, 2021)

Sugaring is the term for the heavily oxidized metal on the i shielded back side. If you can’t purge with argon then you may try Solar Flux. 









						Why You Should Use SOLAR FLUX
					

The Problem When welding stainless steel (or one of the high nickel alloys (Inconel, Monel, etc.), the shielding gas or the flux in the electrode only protects the FRONT of the weld. You must use s…




					solarflux.wordpress.com


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## Just for fun (Jul 7, 2021)

Thanks guys,

682bear, I kind of figured it all had to do with heat and/or speed and the lack of shielding.  I'm new to tig welding and have never seen it bubble up like that before.

Erikmannie,  I have looked into the dual argon flow meters in the past, just never made it a priority.   I guess it's time to look at it again.   

Jwmelvin,  Thanks for the pro tip on the solar flux.


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## Cadillac (Jul 7, 2021)

Cooked it!


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## jakes_66 (Jul 7, 2021)

Yup, sugared through for sure.  It's very common on thin materials, don't worry you didn't do anything wrong.  It's a simple fact that you must deal with when welding thin stainless steel.  In fact any material will do it to one degree or another.  Any high temperature metal in contact with atmospheric oxygen will oxidize readily.

At work our welders work with these conditions every day.  Every fabricator has a selection of jigs and fixtures to handle back-purging any variety of situations and positions as well as a handy roll of high temperature tape to seal them up and attach!


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## Just for fun (Jul 7, 2021)

One more little test weld, I clamped my coupon to a piece of aluminum, 35 amps.  Looks better, still not good but at least now I know what's going on.


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## Ulma Doctor (Jul 7, 2021)

with stainless steel, the black lumps are Carbide Precipitation
with the aluminum, it is aluminum oxide precipitation

lower welding temperatures or advancing the weld pool quicker is a good place to start
if you stay in one spot too long, the parent metal melts all the way through


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## Lo-Fi (Jul 7, 2021)

You may be welding with the amperage too low. 

Welding "cool" makes you stay in one place longer waiting for a decent puddle and end up pumping pump far more heat in than you would if you'd had more amps and worked faster. Moving quickly is so, so important when welding thin stuff, but it's not easy! MIG with stainless wire is much easier to get a decent joint and not cook the other side (without back purging), for what it's worth.


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## rwm (Jul 7, 2021)

This might be a dumb question, but some of your weld zones look etched beyond the weld. You are not on AC are you?
Robert


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## brino (Jul 7, 2021)

Great question Tim!
I am glad you're not too proud to show your fails.

Thanks everyone for some great tips and discussion.
With my day at work dealing with detailed emails and spreadsheets it good to have something interesting to read!

I have learned something today.

-brino


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## Just for fun (Jul 7, 2021)

rwm said:


> This might be a dumb question, but some of your weld zones look etched beyond the weld. You are not on AC are you?
> Robert



Nope,  I'm on DC.


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## Just for fun (Jul 7, 2021)

brino said:


> Great question Tim!
> I am glad you're not to proud to show your fails.
> 
> Thanks everyone for some great tips and discussion.
> ...


Thanks,  Glad I could bring some entertainment to your day! 

You never know unless you ask. 

Tim


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## Just for fun (Jul 7, 2021)

Lo-Fi said:


> You may be welding with the amperage too low.
> 
> Welding "cool" makes you stay in one place longer waiting for a decent puddle and end up pumping pump far more heat in than you would if you'd had more amps and worked faster. Moving quickly is so, so important when welding thin stuff, but it's not easy! MIG with stainless wire is much easier to get a decent joint and not cook the other side (without back purging), for what it's worth.



Thanks for the tip.  I'll get another piece cleaned up, turn the heat up a bit and try and go a little faster.  Backing it up with a piece of aluminum helped.


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## brino (Jul 8, 2021)

Just for fun said:


> Backing it up with a piece of aluminum helped.



A copper backer may be even better.....


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## rwm (Jul 8, 2021)

Tim- I was specifically looking at this pic:



Those welds on the left have a funny zone around them and the bead has a dark appearance. Do you purge your torch before the first weld? Could the gas flow have been too low? Could the metal be clear coated that you don't know about? Any chance the material is 303 SS? (Which doesn't like to be welded due to Sulfur and Phosphorus)
The back side it always and issue if you get full thickness penetration.  For cosmetically important welds I try not to do that. I also will clam a flat piece of steel on the back sometimes. Copper is superior but expensive.
Robert


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## Just for fun (Jul 8, 2021)

Robert,  I thought maybe that is what you were looking at.  Those welds on the left are the back side of the first pics I posted and what made me ask the question to start with.   I flipped it over and clamped it to a piece of aluminum to do the next two little beads.  I don't have that much of the stuff, so I don't want to waste too much until I finish the cup holder for my wife's ATV.  LOL  

I have no idea what the material is, it was in the junk pile.


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## rwm (Jul 8, 2021)

Ahhh. Makes sense now.
Robert


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## Just for fun (Jul 31, 2021)

Ok,  I've been playing around with that piece of stainless.  Clamping it to a piece of copper really helped and so did turning up the amps and moving faster.

Thanks for the pro tips! 

Anyway I started with this:



And ended with this:


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## Lo-Fi (Jul 31, 2021)

Great, they look pretty passable! Nice job


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