UT for Weld Fusion

By pipewelder_1999 (****)

Date 09-18-2001 22:53

I don't know about "Certification" but lack of fusion can be detected with ultrasonics.
I think in some cases it is more sensitive than RT depending upon the angle of the non-fusion in relation to the film plane. There is a website at http://www.ndt.net that contains quite a bit of information related to UT.

Have a good day

By G.S.Crisi (****)

Date 09-20-2001 18:26

I believe that in saying "certifying fusion at 100% utilizing UT", Mr. Vanderbos was asking whether you can make sure that in a weld there was 100% fusion (and thus 0% lack of fusion) by means of ultrasonic test.
Pipewelder has correctly answered that in fact, UT is actually used to detect lack of fusion, sometimes with higher precision that radiographic test.
Giovanni S. Crisi
Sao Paulo - Brazil

By MBSims

Date 09-21-2001 04:32

My experience has been that fine, closely spaced porosity can be interpreted by the UT operator as a planar defect (such as lack of fusion). UT can detect lack of fusion, but can also result in rejects that would be acceptable by radiography. This means unnecessary repairs to the weld that can do more damage than good. On the other hand, if the weld passes UT, then the liklihood of lack of fusion of any significant size is very low. I don't believe anyone could "certify" that there is "100% fusion" and be making a statement that could be backed up in a court of law. If they are willing to sign such a certification, ask them to demonstrate it on a mockup weld similar to the fabrication weld.

Marty

By NDTIII

Date 09-21-2001 12:33

You can never guarantee 100% fusion in a weld with 100% accuracy. You must establish an acceptance criteria and live with it.
Of course there are differences between UT and RT, and Marty is correct in saying indications rejected by UT may be acceptable by RT. You must live with the acceptance criteris you choose initially.
Also, when choosing UT, you must consider your bevel angle. If you are using mechanized welding with, say, a 5 degree bevel angle, then standard single element transducers will most likely miss any LOF in the fill passes. You would need to use a delta technique utilizing, say a 50 degree probe followed by a 45, depending on the depth you are looking at.
If you are concerned with minute areas of LOF, I suggest you look into the use of computerized automated UT. It is much more sensitive and reliable than manual UT.