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Technical Discussions
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
21:33 Nov-10-2014
What type of stainless steel is?
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I need to know what type of stainless steel are these tubes, because in 8 months they presented pittings where the product began to leak. In the inside we have milk and the outside hot water. I thought about use a thickness measurement with a known thickness, but the tubes have 1mm of thickness, and I have problems to measure it correctly, it is maybe an effect of near zone? Please let me some advices. Why this happended?

 
 Reply 
 
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
21:35 Nov-10-2014
Re: What type of stainless steel is?
In Reply to Pedro Serruto at 21:33 Nov-10-2014 (Opening).

I have a 5MHz transducer of 0.250 of diameter

 
 Reply 
 
Gokul Hrishikesh
Consultant, AUT Specialist
India, Joined Jul 2013, 76

Gokul Hrishikesh

Consultant, AUT Specialist
India,
Joined Jul 2013
76
21:33 Nov-12-2014
Re: What type of stainless steel is?
In Reply to Pedro Serruto at 21:33 Nov-10-2014 (Opening).

Pedro,

Somebody planned to mix water and milk and little bit of corrosion.
God save the consumers!

Coming to the point, no one here can tell you exactly which material is that by looking at its photographs.
Get a chemical test/PMI done to get the correct answer.

Regards,

 
 Reply 
 
Pedro Serruto
Director, Level II UT, PT
Red Code Quality, Peru, Joined Sep 2013, 88

Pedro Serruto

Director, Level II UT, PT
Red Code Quality,
Peru,
Joined Sep 2013
88
15:40 Nov-13-2014
Re: What type of stainless steel is?
In Reply to Gokul Hrishikesh at 21:33 Nov-12-2014 .

Hi Gokul

This company called us to determine if these tubes are or not AISI 316L, because they said (and Ive read everywhere) that this material is used in the food industry, but, if only these tubes had some type of corrosion, that would mean that only these tubes were not AISI 316L. These are welded pipes.

 
 Reply 
 
Esmaeel Ahmadzade
Engineering,
ferdowsi university of mashhad, Iran, Joined May 2011, 11

Esmaeel Ahmadzade

Engineering,
ferdowsi university of mashhad,
Iran,
Joined May 2011
11
09:30 Nov-14-2014
Re: What type of stainless steel is?
In Reply to Pedro Serruto at 15:40 Nov-13-2014 .

Dear Pedro Serruto,
AISI316 is magnetically stable at room temperature; it is nonmagnetic(paramagnetic) whether it is deformed or not. other austenitic stainless steels such as AISI304,201,301 ,which have lower corrosion resistance than 316, can be magnetic(ferromagnetic), if they are deformed. therefore, simply you can use a magnet to examine your material in deformed and nondeformed state to understand what type of stainless steel your material is. i should mention that this is a simple way not exact. regards,

 
 Reply 
 
Rick Lopez
R & D,
John Deere - Moline Technology Innovation Center, USA, Joined Jul 2011, 191

Rick Lopez

R & D,
John Deere - Moline Technology Innovation Center,
USA,
Joined Jul 2011
191
16:13 Nov-14-2014
Re: What type of stainless steel is?
In Reply to Pedro Serruto at 21:35 Nov-10-2014 .

Pedro,
It's not clear what you're proposing to do with your 5 MHz UT probe, but your client company is going to need destructive metallography and emission spectroscopy to work out the alloy (allowable chemistry overlap often leaves you with a small list of "most likely" alloys) and underlying problem. You don't mention application details, or whether pits are localized to welded areas, but even if the alloy is correct, sensitization could be causing intergranular corrosion and failure (http://www.corrosionpedia.com/definition/1334/sensitization-stainless-steel).

 
 Reply 
 
Shank Vagal
India, Joined Jun 2014, 73

Shank Vagal

India,
Joined Jun 2014
73
19:31 Nov-14-2014
Re: What type of stainless steel is?
In Reply to Pedro Serruto at 21:33 Nov-10-2014 (Opening).

From the look at the info (not just the pic/s, for heaven's sake), it could not be a 316L material, but still you need to confirm minimum by PMI. Simple Moly test could suffice as well. As regards inspection, EMI or ET will be best suited. No UT for 1 mm (even less after corrosion). Btw, your design engineer needs to look at 1 mm thickness value once again.

 
 Reply 
 
Nirav Dave
NDT Inspector,
Company, India, Joined Jul 2014, 11

Nirav Dave

NDT Inspector,
Company,
India,
Joined Jul 2014
11
05:00 Nov-17-2014
Re: What type of stainless steel is?
In Reply to Pedro Serruto at 21:33 Nov-10-2014 (Opening).

Pedro

first you can take a magnet and check weather the material is magnetic or not because AISI 316 is generally nonmagnectic. To know the exact grade PMI is the best solution. for UT of 1mm thickness tube of course it can be done but for that pencil type probe is required with proper coupling. more over it would be better if u use higher frequency though 6MHz or 10MHz is ok.

 
 Reply 
 

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