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Up Topic Welding Industry / General Welding Discussion / Mig welding 308 and 309
- - By Chris2626 (***) Date 08-13-2011 19:12
I started a new Job about 2 weeks ago and they do a lot of mig 308 stainless and 309 carbon to stainless. I must say I have never mig welded 308 or 309 and well the weld always comes out gray looking. I'm using a tri-mix gas. These guys tell me this is the way it should look but I remember when I have tig welded it, it would be a shiny silver color when welding with 309. and same with tig 308 it would be silver or gold color.

On a side note though this place is about 5 dollars less then my last welding job but dam I'm learning a ton about fitting structural and later probably pipe fitting which I have been seriously lacking. Finally found a place that will work with me and helping me learn to fit which Tommyjoking on here said to me about a year ago talking on the phone that I may have to take a pay cut to get to learn to fit and he was right but dam I'm happy I'm learning to fit finally. I wasn't sure if a place like this existed.

So yeah about the mig 309 thing what am I doing wrong how can I get some color in my 308 or 309 weld??

Thanks
Chris
Parent - - By hillbilly (**) Date 08-13-2011 19:57
What are they using for shielding gas?
Parent - - By Chris2626 (***) Date 08-13-2011 20:14
Trimix.... it's like argon carbon dioxide and helium mixd
Parent - - By weldwade (***) Date 08-14-2011 02:27
Chris are you pushing or draging? Dragging the gun will give you a dingy grey looking weld.
Parent - - By Chris2626 (***) Date 08-14-2011 03:05
pushing
Parent - - By Lawrence (*****) Date 08-14-2011 05:49
Don't expect pretty colors with stainless GMAW spray transfer and solid wire.

The weld pool is too hot and the travel speed is too fast to keep the weld covered by shield gas until it cools sufficently to have pretty color.

I seriously doubt your code inspection requirments say anything at all about the color of the weld face.
Parent - By Chris2626 (***) Date 08-14-2011 18:33
Thanks I was just curious is all to know if I had it setup right or not.
Parent - - By 522029 (***) Date 08-13-2011 21:38 Edited 08-13-2011 21:41
I have personnaly used GMAW on several hundred feet (of weld) SS pipe. This project was 8", 10" and 14" 304L pipe welded with 308L wire.
Tri-mix gas was used.

There were also MANY 1 1/2, 2, and 3" fittings involved.

The "rainbow color", mostly straw and light purple was present.

Griff
Parent - By hillbilly (**) Date 08-14-2011 02:25
Just realized you told what shielding gas in your original post. D'oh. I've personally never used the tri mix, but I've welded my fair share of SS plate. We used the dual shield wire from ESAB in the 308 and 309 flavors but with straight argon. One variable that comes to mind is when my heat(voltage) was slighty off I wouldn't get the pretty array of colors like you become accustom to with SS.
Parent - - By DaveBoyer (*****) Date 08-15-2011 01:32
There is a wealth of information on this site: http://www.weldreality.com/ Ed's suggestions may go against the grain with the bosses at work, but the website is a good read, even if You are not using His suggested shielding gas mixtures. Don't make waves at work, but if ever in the position to make the decisions, I would try Ed's suggestions.
Parent - - By Chris2626 (***) Date 08-15-2011 03:46
Dave thanks for the website that really was a good read and still reading. I've used the trimix before but it was for ballistic steel which I can understand because you needed that extra punch to penetrate. Second day I was at this job I got into it with the shop foreman and well I've learned my lesson... I'm there to learn to fit and thats it. If they want to keep using the wrong gases and not purging stainless pipe it's on them but while i'm there I will do my best to do quality work. Another thing I notice well when I took a pipe welding test there they were using nitrogen to purge while i have always used argon. I found my pipe test came out like crap although I hadn't welded stainless pipe in about 2 years or so there really was no color at all in my weld root wasn't sugar coated but didn't have much color maybe it was because i was rusty I don't know.
One person told me it was because I was not purging with argon but I really don't know.
Parent - - By DaveBoyer (*****) Date 08-15-2011 04:47
Nitrogen is cheap. It is an accepted purge gas for brazing copper refrigerant tube, but I have not heard if using it as a purge for arc welding stainless pipe.

Nitrogen at high temperatures can harden at least some steel alloys, and can cause nitrogen embrittlement, but I don't know the details.
Nitriding, a case hardening process is an example of this.

There is a family of stainless steels [Aqumet 22 and Nitronic 50 as examples] that are strengthened by additions of nitrogen, in a similar fasion to how others [and steel] are strengthened by additions of carbon. The nitrogen does not combine with chrome like carbon does, so it does not affect corosion resistance.
Parent - - By Lawrence (*****) Date 08-15-2011 06:10
Nitrogen is pretty common for purging austinetic stainless steel pipe.

Did miles of it in the 80's in the California wine country.   It doesn't leave a silck wedding band,  the profile is the same but the surface is dull grey.  Just normal for that method.

There are cases where nitrogen is not a good choice, service conditions etc.  Engineering level decision.
Parent - By DaveBoyer (*****) Date 08-16-2011 02:10
Now I have heard of it, learn something new every day.
Parent - By Chris2626 (***) Date 08-16-2011 11:11
well that makes sense then because yes the root was very dull gray color, it seemed to really affect the caping of the weld as well it seemed
Up Topic Welding Industry / General Welding Discussion / Mig welding 308 and 309

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