Nitrogen percentage for ASTM A 350 LF6 Cl2 material 1

[ligin18]

As per project requirement the flange material shall be ASTM A350LF6 Cl2 material. But based on Vendor material test report the percentage of nitrogen is not as per standard requirement (percentage of nitrogen is low than the standard).As per standard only LF6 grade have the nitrogen percentage. Please clarify the purpose of nitrogen in LF6 grade.
Is it possible to replace ASTM A350 FL6 Cl2 material with ASTM A694 F60.The project requirement is for 60K low temperature material. Is A694 F60 can be used as low temperature material. I read that ASTM A694 can be Charpy V-notch testing at - 46 °C and the minimum absorbed energy for full size specimen shall be 40J average and 30J single which is higher requirement than ASTM A350 material(27 J average and 20 J single).

Plz help me for this issue.

 

[weldstan]

When fine grain melting practice is required to provide low temperature impact toughness properties, nitrogen is an essential element along with aluminum (principally), vanadium or niobium to provide the many metal nitride particulates to act as nucleation sites to produce fine grains.

 

[metengr]

To answer the question;

Is it possible to replace ASTM A350 FL6 Cl2 material with ASTM A694 F60

Not enough information. The SA 350 LF6 is not equivalent to A 694 F60.

 

[weldstan]

Depending on the Code of construction, it may bee possible to substitute A694 F60 LF6. You seem to be misreading F60 which has a MSYS of 60 ksi versus LF6 which has a MSTS of 60 ksi. The difference in minimum absorbed energy requirements is based normal Codes of construction usage. LF6 is mainly used in ASME VIII and ASME B31.3 which define minimum absorbed energy - max design stress is 20ksi. F60 is mainly used in B31.8 construction which permit design stresses considerably higher, as much as 80% of the SMYS - max design stress is 48 ksi.

 

[metengr]

weldstan;
I have come across a similar situation and we did not permit use of F60 as a substitute because of notch toughness issues.

 

[ligin18]

Hi Metengr
As per piping material specification the flange material shall be low temperature 60K material for 10000 Class (API 6A).Design code is ASME B31.3.Vendor offer ASTM A694 F60 material.Can i accept the material.

 

[metengr]

Was impact testing performed for the F60, and did the results meet the minimum requirements for Grade LF6 Cl2?

 

[ligin18]

Hi Metengr
Vendor not provide any test result for for A694. Vendor clarify whether A694 F60 can offer instead of A350 LF6 Cl2 material.Can we use "A694 F60" as low temperature 60K material.

 

[ligin18]

Hi Weldstan
Can you plz provide more details.

 

[weldstan]

ligin18
Take a look at the Tables in B31.3. I believe A694 is a listed material. F60 need not be impact tested. it is only required when the MDMT as defined in your contract and B31.3 dictates. Based on the fact that your F60 has not been impact tested and the MDMT appears to be -50F, you cannot substitute the proposed A694 F60 for LF6, which will have been impact tested at -50F.

I do noy understand why your supplier/forging manufacturer can defne its material as A350 LF6 if it does not meet chemistry requireents. Because I do not have access to the ASTM Specs, I cannot verify your statements.

 

[metengr]

A 694 is not listed in B31.3 Table A.1.

Vendor not provide any test result for for A694. Vendor clarify whether A694 F60 can offer instead of A350 LF6 Cl2 material.Can we use "A694 F60" as low temperature 60K material.

No