Material Identification

[robday2000]

Hi there guys,

This is my first post so i would like to say thanks for the extensive information available on these forums. its really interesting.

Now, I normally liike to run searches for answers but in this instance I have something quite specific I need to find out. I have an element breakdown of a flange I tested on a 9 chrome line. The flange should have been 9 chrome but the Niton Gun gave me the reading below.

Mo 0.41%
Nb 0.02%
Ni 4.92%
Co 16.68
Fe 62.53%
Mn 13.84%
Cr 0.98%
V 0.22%
Ti 0.08%

I have not come across this before. I normally see, Carbon, Stainless and Chrome on the lines that I work on.

Thanks for your time and any input is appreciated.

Regards
Bob

 

[metengr]

How did you prepare the surface for testing? All surface oxide, oil, etc., must be removed by light surface grinding for best results.

 

[robday2000]

Yes, all pmi procedures are carried out correctly. the surface was clean and free from contamination (as good as any other surface prep).

Contaminatation was the first thing that came to mind so i prep'd the surface even more and retested.

Cheers

 

[metengr]

Well, before I would finally decide there is a material nonconformance I would go the next step and remove a small piece off of the end of the flange and have it tested in the lab.

 

[robday2000]

Unfortunately that's not my decision to make. What would normally happen in this instance is that the Flange will be replaced during the next TA. If, conventional NDT methods show that it is not highly corroded.

I'll go ahead and report this as a no match with the chemical analysis for the area inspector to evaluate.

Thanks for your input

 

[EdStainless]

If this part is supposed to be 9Cr you have cause to have it removed.
This chemistry look austenitic, so I would worry about SCC.
I would not take the risk to leave it. If it doesn't match the spec it must be removed.

Is there any marking on the flange? What alloy was specified?

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Plymouth Tube

 

[metengr]

You should also check the fitting with a magnet. If it is austenitic, you'll know right away because the magnet will not cling to the fitting.

If the fitting is strongly magnetic, I would still have a sample remove for complete chemistry. I have seen strange results from portable alloy analyzers used in the field that were out of calibration, mis-applied or used on improperly prepared surfaces.

 

[bruv]

Robday2000:

Regarding your surface preparation, is there any schance you could have picked up contamination from the tool used to clean the surface? This could possibly explain the Co and/or Mn levels.

I've had a look in all my references and can't find anything getting close to the chemistry you give.

 

[robday2000]

I dont think it is a contamination issue with the equipment as I had done around 100 readings before and after this particular flange. All readings were fine except this one. Only possible contamination could be from the petroleum coke???

I tested the flange numerous times and in 2 different locations and got similar results.

I'll have a look again tomorrow with a magnet and to look at the idents. Whatever the case, it will definitely want chopping.

 

[arunmrao]

High manganese levels will evidently make it non magnetic in my opinion.This test may be misleading.

Sorry for my ignorance,but does a corrosion resistant alloy have high Co and Mn?

I have not failed. I've just found 10,000 ways that won't work." — Thomas Edison
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[CoryPad]

Stellite has Co

Maraging steels have Co

 

[metengr]

robday2000;
There is one other possibility, you may be testing in a location(s) that were weld repaired or contain a weld build-up for corrosion protection. Check to see if the flange is ASME B16.5.

 

[EdStainless]

The are Co, Mn, low C, wear resistant alloys, but they shouldn't be in a flange.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[arunmrao]

Ed,
That is precisely my concern. This alloy chemistry should not have been on a flange material. It really beats me.

I have not failed. I've just found 10,000 ways that won't work." — Thomas Edison
_____________________________________

 

[robday2000]

I think this is 1 1/4 Chrome. The flange opposite is 1 1/4 chrome and has the same idents. Retested the flange and gave a different reading to the ones I was getting before.

Strange. I have checked the calibration on my set and its fine. Must just be one of those things. Possibly contamination played a part.

 

[metengr]

robday2000;
This is why you should remove a sample and verify actual chemical composition results if there is a problem with PMI devices.