Weld Identification

Date 04-24-2007 23:46 Edited 04-24-2007 23:48

Spatter shadows can tell you a story. Maybe the HAZ if there's a possibility that one of the hotter processes was used, like SAW. Bead width can be another indicator.

I'm lucky, I never have to guess. All my guys use GMAW or GTAW.

But you said 304, so that leaves me asking, how long is the joint? If it's smallish, and there's no indication of spatter, I'd place money on GTAW. 304 cleans up nice, but you can still find spatter from SMAW or wire feed processes.

By CWI555

Date 04-25-2007 01:26

original weld was seam pipe via EFW. The question is if a weld repair area has been ground and machined leaving no visible trace of the repair bead type, is there a method to identify the originating weld process without any further information?

By ssbn727 (*****)

Date 04-25-2007 07:26

PMI for material identification...
What's the size of the repair?
You got me when it comes to positively identifying the process used under those conditions.

Respectfully,
Henry

By js55

Date 04-25-2007 14:29

WOW!! What a great question.
I don't know that there is a method non destructively. If there is I anxiously await someone posting it.
Destructively you could micro analyze for non metallic inclusions which would tend to be a larger volume percent with SMAW, FCAW, and SAW.
Etching cross sections can provide dilution info. The deposit PMI's, which could then be compared against filler metal chemistry ranges, with consideratin for Cr loss across the arc with SMAW, SAW, and GMAW which is not the case with GTAW.
You could also etch longitudinally for penetration consistency which would tend to vary more with manual process such as SMAW.
Once you build a series of 'not this-not that' results you could deductively reason which process. Maybe.

By CWI555

Date 04-26-2007 01:05

Thanks everyone for your replies.

My case is more proving what it's not, rather than what it is. The specification in question only allows GTAW for repair. It is suspected that in a few cases, SMAW was used, and in others GMAW. I don't think there is a none destructive method, but we do have some cut samples to play with. I am thinking of wet chemical (optical emission spectroscopy) as the spark emission is not as accurate. SEM for imaging, as well as optical microscope, and as you suggested cross sectionals, longitudinal and transverse. I don't have to prove what it is, only what it is not. Js55, I didn't think of the non metallic inclusions, but thats a good point.
If anyone has any ideas of how to improve on this methodology please speak up.

Thanks again for everyone who has provided input.

Regards,
Gerald

By js55

Date 04-26-2007 13:25

Gerald,
Is there something other than non metallics that SEM or Opticals can be used to determine process?

By CWI555

Date 04-26-2007 21:30

Dendretic coring from rapid cooling (the delta ferrite and precipitated carbide should should show well if present in the austenite matrix), I believe it could be at least a clue for comparison in regards to heat input cold vs hot. Anything and everything I can get to at least have a starting point. I can find no text that addresses this directly and most of the reactions are the same I recieved here that being no one seams to know of or have a canned solution for this particular problem. I will also have a sample welded with the parameters of the WPS from the supplier to compare against. (what it should have been welded with to start with.)

If anyone thinks my methodology is off base please speak up. Or better yet if anyone knows of a standard solution for this.

By TomD

Date 04-25-2007 16:54

You should be able to narrow your search by asking what process was used and what processes that shop is capable of performing. Then, if in doubt, I would look for indications of that process or indications it could not be that process. If it is a critical part, you may be able to require them to repeat the process for comparisson. Good Luck. Tough Question.