SS 318LL

[quark]

Can somebody refer me to SS318LL composition and properties and particularly comparison with SS316. I have been searching but with hard luck. Is there a more common name for this duplex grade?

Regards,

 

[XL83NL]

Are u sure u need 318LL? Do u have a UNS number the grade you are after?
Could it be UNS S31803?

 

[kumkumvijay]

There is no ASTM grade like 318, generally L added to indicate low carbon grade ( c<0.04%). Its possible that some welding wire manufacturer can name his wire with his own specification.

 

[EdStainless]

There never has been a 318, XL83NL probably has the correct answer.

S31803 has been superseded (for most users) by S32205 (tighter chemistry, higher mechanical properties).
This is why we should be using the UNS numbers.

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Plymouth Tube

 

[quark]

It is my mistake. What I am asking for is SS 318LN.

Regards,

 

[XL83NL]

Same answer, SS 318LN does not exist, afaik.
Do you happen to have a UNS number of the grade?

 

[kumkumvijay]

L for low carbon and N for defined nitrogen conten. Low carbon support increase in corrosion resistance and nitrogen support hiemperature strength.

the link below can help you to know the different:

http://www.aksteel.com/pdf/markets_products/stainless/austenitic/316_316l_data_sheet.pdf

http://www.m-woite.de/en/materials/14462.shtml

There is a link below to know more about the duplex stainless steel

http://stainless-steel-world.net/pdf/d97_018.pdf

 

[dgallup]

As mentioned above, I think the UNS is S31803 which is 2205. See the German link above. It does list AISI 318LN but that is a bogus number but the link also crosses it to S31803 as well as several European specs.

http://www.matweb.com/search/DataSheet.aspx?MatGUID=bffb931008784caba393837cd290caa2&ckck=1

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[quark]

Sorry for the delayed reply, as I was searching for the data myself. It is indeed S31803. AISI 318LN has been referred in many websites and the equipment manufacturer has repute world over in Pharma Industry. So, I don't think it is a bogus classification. The composition given by manufacturer matches with S31803.

Intergranular corrosion and pitting seems to be not an issue as Chromium content is more than SS 316 (standard for pharma equipment) and Carbon is less. Not an issue with pitting as well. Only need to check what is the effect of lower Nickel content. There are no agressive fluids in the process.

Regards,

 

[EdStainless]

Yes it is bogus, done by ignorant people.
There never has been a 318 grade recognized by AISI, ASTM ASME or any other organization.

S31803 is the old designation for the generic alloy 2205 and it does not apply any more. Its current designation is S32205. This UNS has tighter chemistry and it is what all reputable producers are working to.

The duplex stainless alloys are very different from the austenitic grades.
-Just like in 316 the Ni has no role in corrosion resistance, only in maintaining the phase balance.
-They must be annealed correctly to preserve the correct phase balance.
-In welding the greatest concern is formation of detrimental intermetallic compounds, There are special tests for this (A923).
-There are special weld fillers, for S32205 use S32209 as weld filler.
-They cannot ever be used above 600F if you care about mechanical properties or corrosion resistance.
-They are much stronger than austenitic alloys, so you should be using thinner walls.

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Plymouth Tube

 

[quark]

The operating temperature is 50C maximum and normal operting pressure is 0.13 barg . The design pressures is 12 barg to contain dust explosion. There will be lot of welding.