7075 Aluminum and ASME B31.3

[banjohamster]

Hi everyone,

I have a component fabricated from 6061-T6 Aluminum seamless tube, and a recent study found some limitations in it's internal design pressure at higher temperatures based upon calculations from the ASME B31.3 standard. We currently operate within those limitations, but this may change in the future.

I am currently investigated whether or not the same component can be fabricated from 7075 Aluminum instead. However, the basis for the calculations is Table A-1 in the B31.3 which gives basic allowable stresses for a variety of materials at different temperatures. In this table, 6061-T6 is listed, but 7075 is not.

Section 302.3.2 of B31.3 gives the basis for the numbers in Table A-1, and the ASM Handbook vol 2 gives some data on 7075, so given enough time, I could piece together a table of basic allowable stress at different temperatures for 7075. However, I'm wondering if I'm just re-inventing the wheel -- does anyone know of any published data for 7075 that has the allowable stress values already calculated.

Many thanks in advance

 

[metengr]

Sounds like you would need to generate an ASME B31 Code case for use of 7075 under the service conditions you expect. There are no equivalent allowable stress values that can be incorporated under B31 code without scrutiny by the code committee. The table A-1 you refer to is allowable stress values based on actual test data from previous code cases that were eventually adopted by B31.3 and B31.1 for use.

 

[banjohamster]

Thanks Metengr, for your reply. I was hoping that these values could be worked out given the guidance in 302.3.2 of B31.3. I guess I'll have to rethink my plan.

 

[metengr]

The information in 302.3.2 is how to determine allowable stress values when data is generated for materials. I still think the route of a Code Case is your best approach if you intend to use this material.

 

[EdStainless]

This shouldn't be to much effort, you have material strength values to use for the request.
Just use the ones listed in MMPDS. You could go back to the people at Battle that maintain MMPDS and as for the raw data for the product forms that you are interested in.

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P.E. Metallurgy, Plymouth Tube