A356 cast aluminum in as cast (F) condition

[Omid18]

Hi All,

We're having an issue with a series of our "as cast" condition A356 parts. Previously we never needed to test the "as cast" version of the A356 parts because they are used in very non-demanding applications. We would temper the casting only when it was necessary and test for it.
We recently encountered an issue with a new regulatory body because they are requesting material certification for all parts , including the as cast A356. They agree that the material is adequate for the application and does not need to be tempered, but they also are requesting testing to certify that the material is indeed "as cast" A356. This is all good and dandy, but the problem is that ASTM B26 which defines the requirements of sand cast aluminum simply does not include F tempered A356 in its list of mechanical properties (It includes the tempered versions) and so the testing facility does not know what to test to. Is there another standard that we could reference for the testing facility that includes F tempered A356? most other standards that I have found have the same issue as ASTM B26 it is very weird that 356 has properties for the F temper included, but A356 which is a variant of 356, does not.

Thank you for your help!

 

[EdStainless]

Does the spec have any requirement other than chemistry? Maybe a hardness?
The MTR with chemistry and stating that this is A356 as cast is all that you need.
If they want a mechanical test then they should point to the spec where it is required. If they persist ask them to show you the acceptance criteria.

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P.E. Metallurgy, consulting work welcomed

 

[Omid18]

Thanks for the reply EdStainaless.
What you are saying makes "sense" but unfortunately class societies don't always operate on sensibility. The surveyor says he needs to see a chemical and mechanical test report that says material X passes per Y standard. He also argues that the testing is to make sure the casting process is being done properly and there are no major defects. When we asked them for their recommended spec, we were told that it is our responsibility to figure that out. In short, they are not helpful. The only solution for us is to find a standard set that defines the A356-F mechanical properties just as B26 does for 356-F.

 

[EdStainless]

Or give them a report with mech test and simply say that it meets the requirements of the specification.
Since there are none then any test results will meet the requirements.

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P.E. Metallurgy, consulting work welcomed

 

[3DDave]

One area that could be trouble is if A356 spontaneously age hardens and doesn't remain in the -F condition indefinitely. I would expect the 356 alloy to do the same, but maybe that alloy is in the B26 standard because someone had a similar problem and paid to have the testing done to get it included. That's where many standards come from - needing to sell stuff and needing a standard, the seller pays to get that standard created. I'd suggest contacting ASTM, particularly the governing subcommittee to see if they can shed light on adding A356-F to the standard.

 

[Omid18]

Thanks 3DDave! I did in fact reach out to ASTM last week but I have yet to hear back and I don't think I will any time soon (if ever). I don't think that has the potential to be a solution for us in the short term.

 

[EdStainless]

There are a lot of ASTM spec without mech property requirements, especially cast alloys.
We used to report properties all of the time on MTRs where the spec had not requirement for strength or reporting because a customer asked for it.
We always included a footnote to the properties saying there the properties were being supplied for information purposes only and were not part of the applicable specification.

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P.E. Metallurgy, consulting work welcomed

 

[Compositepro]

When I was working for an aerospace composite materials manufacturer many of the tests were done to proprietary company specifications. The specification was listed with the data just as it would be if it were ASTM.

 

[Omid18]

Thank you all. It seems like the only solution is to convince the surveyor to give us a break somehow. Appreciate all your help.