Magnetic testing question: 309 filler? 1

[kingnero]

What is the general consensus on MT on ferromagnetic steels, welded with an austenitic stainless filler?
Can this be done? If so, are there limitations on the acceptance criteria, is the accuracy as high as when performed on all magnetic joints?
I am by no means an NDT expert, I just had a quick browse through the (ISO) MT standards, and this case does not seem to be mentioned.
I know PT (dye penetrant testing) is an alternative, but I have High strength parts that were welded with a 309 filler, and MT has been performed (possible the MT operator was not aware of the filler metal that was used). I would like to know whether or not I can trust these test reports.
Thanks for your input.

 

[EdStainless]

Did you MT the weld qualification coupons? How did those look?
Yes, these welds would likely look funny in MT.
They will be a mixed structure. The center of the weld will be austenitic and the mixed zones will be duplex.

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P.E. Metallurgy, consulting work welcomed

 

[weldstan]

You should not trust the results and should perform PT on the welds in question.

 

It is assumed across the welding industry that MT is just not done on austenitic stainless steels and their welds.

309 weld deposits contain on the order of 10% ferrite, which is the ferromagnetic phase, so MT will not give useful information if it gives any information at all. It might even give a false indication at the sharp boundary between a sightly ferromagnetic weld deposit and a fully non-ferromagnetic 304 base metal.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[kingnero]

Thanks all for the interesting and informative replies.
I will not accept these reports and will require retesting using PT, as clearly suggested by weldstan.

The center of the weld will be austenitic and the mixed zones will be duplex.

Due to a very high dilution rate, the center of the weld is martensitic (up to 450 HV), so there are other issues to deal with as well, apart from the reporting.

It is assumed across the welding industry that MT is just not done on austenitic stainless steels and their welds.

That is what I was thinking, but so far I see no evidence that supports this ideology.
However I do not dispute this at all, I merely asked this because I was hoping for confirmation. The message is well received.

 

[mfgenggear]

Any non magnetic steels have to be flo or dye penetrant inspected. then it has to be x-ray.
The penetrant will pick up surface cracks or indications.
The x-ray will verify subsurface indications,
Use the standard specifications to specify
The quality requirements.
I was trained for both.
Recommendation but not necessary.
For the penetrant to verify properly
The welds have to be hand ground to a smooth surface

 

[kingnero]

Thanks for the additional information.

 

I've seen several prognostications about what weld structures will result, but all the information we have about the base metal(s) is that it is 'high strength'.

Alloys possessing the property of being attracted to magnets are referred to as 'ferromagnetic'. 'Magnetic' is the word that is colloquially used (and also when I am tired).

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[mfgenggear]

there are stainless steels that depending on the heat treatment become magnetic, but are NDT tested with flo pen and or X-ray.

 

[EdStainless]

That is huge dilution given the Ni content of 309. Even if the center is martensitic the composition and magnetic properties will vary all over the weld. You likely also have massive carbide formation in weld also then. The variations in composition and structure would complicate MT.

mfg, thanks. I gave up on this a long time ago. Everything is magnetic, that is has some kind of magnetic properties just like it has mass. Ferromagnetic is what most people mean and I let it go. Of course there is diamagnetic and paramagnetic also.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[mfgenggear]

Thanks ED,
I have memory loss with correct technical nomenclature. but we all know what it means.

 

[kingnero]

That is huge dilution given the Ni content of 309. Even if the center is martensitic the composition and magnetic properties will vary all over the weld. You likely also have massive carbide formation in weld also then. The variations in composition and structure would complicate MT.

Dilution is estimated based on the macrographs to be around 75%. Yes, there are carbides, yes, this entire thing is not going as expected. Thanks to everybody for your insights.

 

[gtaw]

Carbon steels, high strength low alloy steels are magnetic. Austenitic stainless is at best slightly magnetic. You will see a magnetic particle indication at the weld interface between the carbon or HSLA steel and the weld deposited with austenitic stainless filler metal. Good weld or bad, the magnetic particle indication will be there.

Best regards - Al