UT of 309 dissimilar welds

[welda]

I am required to UT 316L Stainless penetrators into a vessel body of 30mm thick P355J2 (50D) material. I have used a 309 filler wire. I have welded a calibration block but can't get an echo through the weld material. Does anyone have any experience they would be kind enough to share?

 

[metengr]

welda
This could be a grain size problem along the fusion zone of the weld. I have seen this before with UT of austenitic stainless steel butt welds where lage grain size resulted in a mirror-like reflector. Have you changed the frequency of the transducer to reduce attenuation, and increase penetration of the sound?

 

[ndeguy]

welda

With such welds, the deposited weld metal will have a cast columnar grain structure. Standard pulse-echo single crystal shear wave probes are ineffective for examining this structure as the ultrasonic beam is scatterred and skewed as it traverses the grain boundaries. Standard practice for such welds is high-angle, low frequecy, twin crystal longitudinal wave probes using a block of the sort you have described. Put in artificial reflectors at the root fusion faces and in the volume of the weld to ensure that the equipment can pick up these reflectors.

Caveat - Due to poor S/N ratio and the above skewing effect, correct interpretation requires extensive experience.

Below is a link to one paper retrieved by Googling "ultrasonic test of stainless steel welds"

http://www.ndt.net/article/v06n01/bieth2/bieth2.htm

Good luck



Nigel Armstrong
Lloyds Register
Independent Verification Body Surveyor

 

[welda]

Hi guys,

Thank's for the rapid response.

I have tried testing with numerous frequencies and different angled probes with no joy. I had forseen problems with this testing but not to this extent!

ndeguy, I will run this information passed my NDE contractors and see if they have the required equipment/ experience to carry out your suggestion.

Thank's again.

 

[JR97]

Welda,

The key is to use angled longitudinal waves instead of the traditional shear waves for the angle inspections. I will respectfully disagree with NDEGUY in that dual element and high angle transducers are not stanard practice. We routinely test 300 series stainless welds up to 4 inches thick using single element, 2.25 MHz angle longitudinal transducers. The problem with using angle longitudial waves is the fact there will always be a shear wave component at a lower angle. As the lonigitudinal angle is increased above about 45 degrees, the strength of the shear wave is considerably greater than the strength of the longitudial wave. non-relevant reflections returning from the lower angled shear wave are easily confused with signals of interest from the longitudinal wave.

JR97

 

[hogan666]

I would suggest consulting a level III familiar in UT of SS