UNS S31803 vs 316

[gtzaki]

Hi

We had some parts made up specified to be made in 2205 Duplex. When the parts came, it looked good and we were very happy with the machining quality. However, I remembered from my experience with 2205 that it is magnetic and so I did a simple test and found that our parts are not magnetic. I've contacted the machining company and they sent us an inspection certificate for UNS S31803 material which they claimed they used to machine the parts up.

So my question is, is UNS S31803 magnetic? I understand that duplex is partly ferritic and should be magnetic, but I don't know whether there might be a slight difference between the 2205 I had previously and the one they supplied.

Also, is there an easy/cheap/non-lab way to find out whether the part is in fact some inferior SS? My boss suggested comparing hardness, any other ideas?

Best regards,
Zaki

Norzaki Mizan
Geoteknic Pty Ltd
QLD, Australia

 

[moltenmetal]

31803 and 316SS have compositions different enough that you can determine it by X-ray fluorescense (XRF). Lots of inspection companies out there have point and shoot XRF machines which will tell you the alloy composition precisely enough for that purpose. The test is non-destructive and takes a few seconds to complete. Unfortunately the units themselves are pretty costly to buy yourself.

 

[DiplingAndre]

Hi!
2205 and S31803 is only slightly different.
According to my experience both materials should be lightly magnetic.
The best way to find out what kind of material you have is to to an PMI with an XRF or OAES. an XRF type leaxes also no burn marks like the OAES but is not that accurate.
Its an easy, quick and save way to find out what you have!
If you don't have a PMI instrument in your company you can ask someone else to do it for you. I'm sure there are different service companies who can do it.

Best regards Andre

 

[metengr]

Yes, the duplex stainless is magnetic. However, you need to verify or sort the material using PMI to confirm if it is duplex or an austneitic stainless steel.

 

[gtzaki]

I've contacted the machining company and they've checked with their supplier who has said that UNS S31803 is non-magnetic, and the machining company themselves did say that it was more difficult to machine this material (which indicates possibility that it is what they say it is).

DiplingAndre, the 2205 Duplex material that we had in the workshop was highly magnetic. The 'supposedly' UNS S31803 that was machined up is slightly magnetic (not dissimilar to 316).

Thanks for the suggestions guys, I'll be looking around locally for an inspection company to do a quick and easy test to check the composition.

Norzaki Mizan
Geoteknic Pty Ltd
QLD, Australia

 

[EdStainless]

S31803 is not 2205, 2205 is S32205 which is a more restricted chemistry.
That aside, 2205 is highly magnetic and 316 should be little to non-magnetic. They are very different. Even when 316 is highly cold worked and it is more magnetic it is still a lot less than 2205.

Is there anywhere on the part where you can do a hardness? 2205 will be Rc20-25 and 316 should be below Rb90.

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Plymouth Tube

 

[gtzaki]

Ed, thanks for the clarification on S31803 and S32205.
We know that 2205 is highly magnetic due to the half ferritic structures. What do you reckon, is S31803 magnetic as well?

We can do a hardness test on the part, will have to source the tools for it.

 

[EdStainless]

since all S32205 is S31803 (but not vica versa) they will look the same as far as magnetism and hardness goes.

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Plymouth Tube

 

[gtzaki]

Ed, thanks for the clarification.

A supplier in China got back to me and said that they degauss their 2205 duplex prior to selling. Is it common practice for suppliers to degauss duplex?

-- Australia --

 

[DiplingAndre]

I think it depends what you do or want do do with your material. But I read a lot of specs where it's required.
But degaussing means not to take away the ability to react to a permanent magnet (which is probably your test if the material is magnetic or not)its only that the material do not act as a magnet itself.

 

[gtzaki]

Thanks Andre, I was clarified of this words mixup by a corrosion specialist at the ASSDA (Australian Stainless Steel Development Association).

He said that Duplex SS is a slightly magnetic material (if you put it next to a compass, it could attract the needle).
He says that all duplex SS attracts magnet strongly (if you put a magnet next to it, it will stick strongly to the material). This is because of the part ferritic structure in the material. Heat treating or annealing will not affect the ferritic structure, which means that it will always attract magnets strongly.

So that pretty much concludes that the material for the part we got is not a duplex material.

Thanks for the info and feedback guys!

-- Australia --

 

[EdStainless]

Two words.
ferromagnetic
magnetized
the first is when a material interacts with a magnetic field, ie being attracted to a magnet.
the second is when a material possesses a magnetic field of its own. Any material that is magnetized must be ferromagnetic.

You can turn magnetization on and off by magnetizing and demaging (degaussing).
The first one cannot be changed as it is an intrinsic material property.
If your material does not strongly attract a permanent magnet (even a rather weak one) then it is not 2205.

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Plymouth Tube