We recently had 135 x-rays performed on .060" wall tubing, Inco 625. They were welded GTAW full penetration butt welds. Nearly all the xrays show a linear indication centered in the weld. It is not lack of penetration, cracks and don't believe it is lack of fusion. We are not sure how well the vendor cleaned the parts prior to welding and suspect that they didn't do a good job due to the presence of oxides on the root surface. Could these indications in the middle of the welds be the oxides from the metal edge surfaces? If we only saw these indications on a few shots, I might buy lack of fusion. These indications are on probably 80% of the 135 shots. The best way I can describe the indication is this: they stay close to center of the weld, are not in straight lines and have diffused edges (soft focus.) Wanted to find out if anyone else has ever seen similar RT work on Inconel 625.
E-mail replys welcome. alan.riddle@perkinelmer.com
I have not seen the type of defect that you described, but thought I would give an idea seeing as you have not had an answer yet.
It may be possible that you had a problem with back purgeing and the indications may be a form of "cauliflower".
Regards
Niekie
Alan:
Just before I switched professions from a welder to an inspector, I was working as a GTAW welder-welding titanium, inconel and aluminum thin gauge tubing typically 2" - 4" diameter for Boeing.
I was instructed to perform "dummy" welds where there should have been a joint on some 2.5" - 0.049" wall Inconel 625 tubing. The weld was made (I assume) to appear that the part was fabricated per the drawings (they had figured out a way to eliminate one of the weld joints). Anyway, I had a number of parts rejected for IJP. I was quick to point out that this was impossible, and that the RT technician or whom ever was reading the film was incorrectly. Same condition that you posted. Indications at the center of the weld which were thought to be IJP.
To this day I still don't know why the parts were rejected considering there was no joint at this location. I was instructed to put another pass over these, they then were found to be acceptable. I thought the interpreter was trying to get OT or something. If you find out what causes this appearance on film, please let the Forum in on this. Thanks.
You might try contacting Sam Kiser at Special Metals for his opinion on this. I heard a great presentation he gave last week on alloy 690 welds that involved "oxide inclusions" in welds made with alloy 52 wire with GTAW process. Perhaps your problem is similar. I will forward Sam's e-mail address tomorrow from work.
Marty
alan,
We're welding the same material only to SA312 type 254 smo base metal. Nearly all of the weld have failed also. Here is what I have observed:
On some welds, I have pt'd the root and found no indication. Upon x-ray the same black line appears. We cut out one of the welds and then cross-sectioned it. A crack like indication was found to be near the root to hot pass interface. It could have been non-fusion also. It was very hard to tell. I believe the hot-pass was causing the discontinuity in the upper portion of the root.
Anyone else please feel free to add whatever information you have as well.
Thanks for the info. We did some additional destructive testing last week. The parts are formed and then heat treated prior to welding, we have pretty much determined the indications we are seeing on the film are oxides as the parts were not properly cleaned after heat treat.
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