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Up Topic Welding Industry / Inspection & Qualification / 2205 SS Heat discoloration
- - By welderette (**) Date 04-05-2007 23:20
I am looking for some guidance in regards to the significance of  extreme black discoloration in the Haz on piping of this alloy.  Is this considered a defect and does it affect the metalurgical stability of this material?  Any insights would be greatly appreciated. Thanks Deb
Parent - By G.S.Crisi (****) Date 04-07-2007 14:52
If I were you, first thing I'd do is to brush the black surface with a stainless steel wirebrush (stainless steel must not be brushed with carbon steel wirebrushes).
If the black color goes away, then I wouldn't bother any more. But if the black color remains, in this case I'll start bothering.
Do as I suggest and come back with an answer.
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By chuck meadows (***) Date 04-08-2007 22:18
Extreme black color is an indication of extreme high heat input. At those high heat inputs, 2205 is capable of sensitization and, in some cases, sigma. Regardless, this discoloration needs to be removed in order for the 2205 to re-form it's natural chromium oxide on the surface that is necessary for corrosion protection. Interpass temp. should not exceed 300F and heat input should be in the range of 12.7 kJ/in and 63 kJ/in. A stainless steel brush is OK, but for complete removal of that black oxide, it might be necessary to consider pickling.

Chuck
Parent - - By welderette (**) Date 04-09-2007 13:15
Thank you Gentlemen!  It was my gut feeling that the things that you described were the source, and also that it would impact corrosion resistance. I have some folks telling me otherwise that it is the nature of 2205, and is fine.  I certainly appreciate the back up, Deb
Parent - - By js55 (*****) Date 04-09-2007 15:00
I would expect that if your running too high of heat inputs on 2205 you may have a phase balance problem as well. Remember, the HAZ's of DSS's (2205 specifically) do not have the enhanced chemistry (though some DSS's have N added to help) of the filler metals so they will be more succeptible to phase imbalance due to excessive heat input.
The chemistries for DSS BM's are designed to achieve phase balance in slower cooling manufacturing regimes, not rapid cooling welding regimes. Not to mention that you will have some HAZ element segregation with welding heat cycles.
Parent - - By jon20013 (*****) Date 04-09-2007 15:49
Brilliantly said Jeff.  Absolutely agree.
Parent - - By js55 (*****) Date 04-09-2007 16:56
Gray hairs and years of Duplex hell, thats all Jon.
Parent - - By jon20013 (*****) Date 04-09-2007 17:03
Be glad for your grey... did you read my funnies?
Parent - - By js55 (*****) Date 04-09-2007 17:32
Yes, I read it. I'm with Lawrence. Where's the pictures?
Parent - - By jon20013 (*****) Date 04-09-2007 17:53
Ain't no way big guy!!!!
Parent - By ssbn727 (*****) Date 04-09-2007 22:19 Edited 04-09-2007 22:31
C'mon Jon!
Like you said: "If you ca'nt laugh at yourself every once in awhile then you're taking life too seriously."
Kind of reminds me of: "Loose Lips - Sinks Ships!"

I'll tell you what, here's a picture of me when I was working in
"Rotten" Groton, Ct. for Electric Boat.
Those were strange days for sure!!! Show us a picture Jon!!!

Respectfully,
Henry
Parent - - By chuck meadows (***) Date 04-10-2007 12:24
Jeff,
  2205 DSS can definitely experience sensitization, yet still maintain the necessary 25-75 ferrite balance. Look at the 2205 Code plus Two (UNS32205). The higher nitrogen will allow this to happen. Sensitization occurs in a matter of just a couple of minutes in the sensitization temperature, but can still cool down to maintain proper austenite/ferrite balance. 2205 DSS is actually quite forgiving. AS was stated on my previous post, 2205 has a very wide range of acceptable heat input. Cooling down rate is absolutely a determining factor, though.
Parent - - By welderette (**) Date 04-10-2007 13:19
Very enlightening!  This work is coming to us from a pipe fabrication company, so all I have to go by is the visual.  Their procedure is certainly within the joules parameters, but it is obvious to me that they are not following the procedure.  They are using a flux cored process with very wide (>1/2") beads on pipe that is .250" wall.  So now we will determine the extent of the defects.  Many thanks, Deb
Parent - - By Ariel D C (**) Date 04-10-2007 16:14 Edited 04-10-2007 16:17
weld discoloration or heat tint can serve as a crevice, it cannot be totally avoided. Need to apply post weld clean up (eg. Pickling) which is "VERY IMPORTANT", as important as control of interpass temperature or the used of inert gas shielding and purging during welding.

Regards

Ariel D C
Parent - By chuck meadows (***) Date 04-10-2007 18:02
Ariel,
  I agree 100%. All are of equal importance. 
Parent - By chuck meadows (***) Date 04-10-2007 18:07
Deb,
  .250" wall is actually right at the limits where FCAW is advised. If this is .045" diameter FCW, then it is really pushing the limits due to the high volts and amps required to have a successful weld. Plus, it appears that the heat input is most likely pretty high due to the wide cap. The first thing I would look at on a visual, if that is all you have to go by, would be if the fabricator took the time to thoroughly clean the oxides from the weld and HAZ.
Parent - By chuck meadows (***) Date 05-01-2007 03:26
To everyone concerned,
  I have been invited to visit Deb (welderette) at the Power Plant in Arizona where she works. The sub-contractor and sub-sub-contractor are scheduled to attend the meeting to try to get to the bottom of this heat tint thing. I will be there tomorrow (actually, I'm in Arizona tonight) but will be meeting with the Power plant personnel, QC Manager (Deb) and other personnel involved in this. Hopefully, Deb will fill the Forum in on what we find out.

Chuck
Up Topic Welding Industry / Inspection & Qualification / 2205 SS Heat discoloration

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