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What’s up guys, Michael with Michael Talks Metal here, back again to talk some metal, what else? Before we jump in, if you would be kind enough to help me out, click that little subscribe button. That helps the channel and we appreciate it! If not, how about a little thumbs up! All that is very much appreciated. Now, let’s jump in!
In the last several weeks our videos have been about aircraft quality alloy steels (AMS 2301) and also premium aircraft quality alloy steel (AMS2300). Much less commonly specified is a special aircraft quality. It requires improved cleanliness like the premiums, but does not require the second melting. It typically requires additional mill procedures and testing but at less cost than a second melting. Magnetic particle cleanliness for this quality level is defined by AMS 2304.
At the end of each video, we always caution that the specifications contain many added requirements. AMS 2304 would be a very restrictive supplemental requirement to an AQ specification that otherwise only requires AMS 2301. Material certified to any of these AMS cleanliness standards have been heat qualified by sampling. It does not replace any required inspection of finished parts. While we are on the topic of specifications there are some things to be aware of in aircraft quality material specifications.
Former MIL specifications can have AMS replacements with ” AMS” replacing “MIL” in the designation. For example MIL-S-6758 has become AMS-S-6758
In AMS standards:
The revision level of an AMS specification is indicated by a letter following the numerals. Initial issue is only numeric…… first revision is A then B and so on. Later revisions supersede the earlier. For example 4130 to AMS 6348E the “E” is the revision level. Any required heat treatments and surface conditions are typically contained within the standard so if stated separately as part of the raw material description, they may be supplemental or modified requirements. In our example AMS 6348 is for a normalized condition only.
In the military MIL standards and their AMS replacements: Revision level is also indicated by a letter following the numerical portion of the specification. In the aircraft alloys, the surface condition and physical condition use a code of numbers and letters.
For example 4130 to AMS S 6758B “B” is the revision level of the specification and would be followed by a letter for physical condition and number for the surface condition.
Physical Conditions are: A – as forged; B- as rolled: C – annealed; D – normalized;
E-normalized and tempered; F- hardened and tempered.
Surface Conditions are: 1 – as forged or as rolled; 2- descaled (pickled or blast cleaned ); 3 – rough turned; 4- cold finished ; 5 – turned or ground and polished
Normalized material would be designated Cond D-1 for normalized material with an as forged or as rolled surface.
A hardened and tempered hot rolled bar would be Cond F-1 and F-4 for a cold finished surface
The AMS versions of former MIL specifications were issued with the AMS scheme for revisions. AMS S 6758 was the initial issue, followed by “A” and then B.
So, as you can see, there’s more than enough details to address when considering what metal works for each given application. And on that note, it’s that time to close with one more reminder to check those specs!
This is Michael with Michael Talks Metal, if you made it this far…..please consider subscribing. If you have and you’ve missed previous videos, click here. Thanks for tuning in, this is Michael with Michlin Metals, I’m out.
