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Standard 4340 heat treatments?

Standard 4340 heat treatments?

Standard 4340 heat treatments?

I am working to standardize my companies material callouts and am hoping for some guidance. Current we can arbitrarily define any heat treatment for 4340 we want (130ksi yield, 200ksi ultimate wouldn't be unprecedented on legacy drawings) and this makes it really hard for our suppliers, but they can't really give me any information that would help untangle the mess. My primary heat treater just said "check the ASMs" with no more guidance.

My question is if there is a standard that provides both yield and ultimate strengths for 4340 heat treatments. In my mind I am thinking a US equivalent to the Australian AS1444 (table 4.2). I looked in ASM HandBook Volume 4 but didn't find anything relevant, just some typical properties under "Heat Treating of Ultrahigh-Strength Steels" (the book is 2200 pages long, so I may have missed it).

Does anyone know of a standard that could help me create standard callouts and correlate yield and ultimate strengths like this? Thanks in advance.

RE: Standard 4340 heat treatments?

Try an internet search for outdated US military specifications, like MIL-H-6875H.

RE: Standard 4340 heat treatments?

There are AMS specs (Aerospace Materials, under SAE) that have designated strength levels.
The heat treat specs are AMS2759-1F (below 220ksi UTS) and AMS2759-2G (220ksi UTS and higher).
Both specs have tables that list annealing, normalizing, austenitizing temps and quench media. They also have tables of suggested tempering temps for various strength levels.
There is also a table that gives suggested tempering temperatures based on the desired strength and the as quenched hardness. This table is most helpful.
Don't actually call out these specs though unless you want all of the aerospace HT rules followed (and you want to pay for them).

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Standard 4340 heat treatments?

" (130ksi yield, 200ksi ultimate ...."

In metengr's provided document those values look kind of far apart.

RE: Standard 4340 heat treatments?

Thanks for your feedback everyone!

EdStainless, I was looking at 2759-1 and it seems to only have the ultimate strength listed. I'm also looking for correlations to yield so that i know they're at least consistent with each other. You raise a really good point about not using the spec directly though because of the added cost of meeting all of the AMS requirements.

metengr, Thanks for posting that. It's really helpful. It looks like the file you linked is from ASM HandBook Volume 1, can you confirm that? (https://www.asminternational.org/search/-/journal_...)

Tmoose, That was my point of posting those numbers. We currently have some ridiculous arbitrary call outs and that's what I'm trying to get rid of. If I have a reputable source for strengths, I can at least make an argument for why some of the others need to be changed. Also because I almost guarantee not a single part has been made to match both of those values.

RE: Standard 4340 heat treatments?

There are no spec requirements for Yield, you can look in the MMPDS and see what they typically are.
There is no independent control of Yield, once you select a UTS the yield that you will get is fairly well fixed.
OK, with multiple tempers you can sometimes bring the Yield down more than the UTS and improve ductility.
But in a steel like this once you select the UTS not only Yield, but Elong, RA, and Impact toughness are all fairly well determined.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Standard 4340 heat treatments?


metengr, Thanks for posting that. It's really helpful. It looks like the file you linked is from ASM HandBook Volume 1, can you confirm that? (https://www.asminternational.org/search/-/journal_...)

Yes, it is a free copy to sell the ASM Handbooks. That is why I thought it would be of value to you rather than dealing with other specifications that probably don't apply to you.

RE: Standard 4340 heat treatments?


In addition to the comments of 'Ed' and 'Met'...

At the HT200 level You specified, 4340 is reliably HT and is usually fairly tough and robust.


NOT all 4340 is created equal. WHAT RAW MATERIAL specification are You specifying???? In aerospace there are several related AMS material specs... for various forms and for high air-melt and for very high quality [more costly] vacuum-arc-re-melt... raw stock.

Knowing the material spec, and critical performance requirements, often dictates the recommended HT spec... and also specific manufacturing procedures to insure performance aspects are not compromised by manufacturing sequence or fab process errors or exclusions.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

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