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Technical Discussions
Dhiliban
Other, QA/QC engineer
L&T HCP, India, Joined May 2016, 16

Dhiliban

Other, QA/QC engineer
L&T HCP,
India,
Joined May 2016
16
10:02 Jul-16-2016
Probe selection for examination of austenitic stainless steel welds with UT

Dear Experts

What kind of angle beam probe to be selected for examining AUSTENITIC STAINLESS STEEL wether longitudinal wave angle beam probe or shear wave angle beam probe

Since Austenitic Stainless steel is FCC crystal structre and coarse grains where the attenuation will be more what are the steps we should follow

    
 
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Ali
NDT Inspector,
Iran, Joined Mar 2013, 97

Ali

NDT Inspector,
Iran,
Joined Mar 2013
97
10:29 Jul-16-2016
Re: Probe selection for examination of austenitic stainless steel welds with UT
In Reply to Dhiliban at 10:02 Jul-16-2016 (Opening).

Dhiliban,
Try the link below.
http://www.ndt.net/forum/thread.php?msgID=45536

    
 
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Diego
Consultant,
Freelance, Spain, Joined May 2013, 188

Diego

Consultant,
Freelance,
Spain,
Joined May 2013
188
11:50 Jul-16-2016
Re: Probe selection for examination of austenitic stainless steel welds with UT
In Reply to Dhiliban at 10:02 Jul-16-2016 (Opening).

Dhiliban.
You may employ longitudinal dual element angle beam longitudinal wave probes. In addition, a weld mock up, with reference reflectors in the weld deposit, should be used. If you use the indicated probes, you should bear in mind that angle beam longitudinal wave search probes are normally limited to 1/2 path examinations, since there is a substantial loss in beam energy upon reflection due to mode conversion

    
 
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Dhiliban
Other, QA/QC engineer
L&T HCP, India, Joined May 2016, 16

Dhiliban

Other, QA/QC engineer
L&T HCP,
India,
Joined May 2016
16
10:12 Jul-18-2016
Re: Probe selection for examination of austenitic stainless steel welds with UT
In Reply to Diego at 11:50 Jul-16-2016 .

Thanks Ali and Digeo

Mr.Diego
Why we have to specifically use longitudinal for examination of UT whether it will experience less attenuation

    
 
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Arunprakash
NDT Inspector,
Caterpillar India, India, Joined Apr 2009, 30

Arunprakash

NDT Inspector,
Caterpillar India,
India,
Joined Apr 2009
30
12:00 Jul-18-2016
Re: Probe selection for examination of austenitic stainless steel welds with UT
In Reply to Dhiliban at 10:12 Jul-18-2016 .

Longitudinal wave would have less attenuation than shear wave for the given frequency.

Normally, Stainless steel have coarse grains, generally low frequency probes being selected for testing.

Attenuation is directly proportional to grain size of the material and indirectly proportional to wave length.

Shear wave would have approximately half of the value of longitudinal wave length for the given frequency. Hence attenuation is high for shear wave when compare to longitudinal wave for the given/selected frequency.

    
 
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Arunprakash
NDT Inspector,
Caterpillar India, India, Joined Apr 2009, 30

Arunprakash

NDT Inspector,
Caterpillar India,
India,
Joined Apr 2009
30
13:14 Jul-18-2016
Re: Probe selection for examination of austenitic stainless steel welds with UT
In Reply to Dhiliban at 10:12 Jul-18-2016 .

For stainless steel testing, we need to have less attenuation which can be obtained from longitudinal wave of low frequency probe.

    
 
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Diego
Consultant,
Freelance, Spain, Joined May 2013, 188

Diego

Consultant,
Freelance,
Spain,
Joined May 2013
188
17:28 Jul-18-2016
Re: Probe selection for examination of austenitic stainless steel welds with UT
In Reply to Dhiliban at 10:12 Jul-18-2016 .

Mr.
Mr. Dhiliban
There are several reasons to employ special probes in lieu of conventional probes.
a) Scattered energy from natural metallurgical discontinuities generates noise indications at higher amplitude than would be expected for the case of ferritic welds. The choice of wave mode
(longitudinal, shear) and probe characteristics (sound field, frequency, bandwidth, etc.) should be optimized to allow a reliable separation of weld defect indications from noise indications
b) The ultrasonic beam has to cross different regions in the parent metal and in the weld itself.
The velocity of sound may vary along this path and this may change the direction of the sound beam. Consequently, this may result in inaccuracy in determining reflector positions.
c) Attenuation in the weld metal is generally more severe than for ferritic welds and can be more or less pronounced depending on the angle of the beam with respect to the preferred orientation
direction of the grain structure. Therefore, the ultrasonic technique should seek to minimize beam path length in the weld metal and, where possible, aim to take advantage of any directions of reduced attenuation in the weld.
d) Beam divergence can also be directionally dependent. The beam profile is usually different from that measured in parent plate (whether ferritic or austenitic) so that size estimation methods which depend on a knowledge of the beam profile, such as the so-called dB drop methods, are not always suitable on austenitic welds.

    
 
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dhiliban
Other, QA/QC engineer
L&T HCP, India, Joined May 2016, 16

dhiliban

Other, QA/QC engineer
L&T HCP,
India,
Joined May 2016
16
14:37 Jul-19-2016
Re: Probe selection for examination of austenitic stainless steel welds with UT
In Reply to Diego at 17:28 Jul-18-2016 .

Dear Mr.Arunprakash,Mr.Diego,Mr.Ali

Thanks for your detialied explaination

Mr.Diego
As you mentioned 6-DB method will not produce accurate result,wether the results are accetpable eventhough they are approximate,If not so

Then which technique we have to depend for defect sizing.

Thanks in advance
Dhiliban

    
 
 Reply 
 
Diego
Consultant,
Freelance, Spain, Joined May 2013, 188

Diego

Consultant,
Freelance,
Spain,
Joined May 2013
188
22:09 Jul-19-2016
Re: Probe selection for examination of austenitic stainless steel welds with UT
In Reply to dhiliban at 14:37 Jul-19-2016 .

Download Notes for sizing flaws Virus Scan recommended!

Mr .Dhiliban
Specifically I have not mentioned the 6-DB method. I referred all methods which are called dB drop. Of course the 6-DB method is included.
In notesforsizingflaws, see document attached, there are some notes for sizing defects. These notes were prepared by me a few years ago, and taking as reference Handbook On the Ultrasonic Examination of Austenitic Welds and the ASTM standard E-2192 . I advise you to read this standard.
If you want more help to deepen this topic, let me know by sending me an email to my address
1    
 
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