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AMS 6411H 4330MOD Temper Temperature

AMS 6411H 4330MOD Temper Temperature

Hi all,

Utilizing 4330 MOD per AMS 6411. After going through the document I found it odd that a temper temperature was not listed in order to hit the minimum mechanical properties specified. Below I list the heat treatment spelled out in AMS6411H.

3.4.5 Response to Heat Treatment
Extracted specimens shall meet the following requirements after being normalized by heating to 1700°F ± 10 holding at heat for not less than 1 hour, and cooling air; hardened by heating to 1550°F ±10, holding at heat for 1 hour ±0.2, and quenching in oil, and heated to the required tempering temperature, held for not less than 1 hour, and cooled in air.

After consulting AMS2759/2F, I see that they list the tempering temperature as 500°F with the caveat that it's only a "suggested temperature only."

EMJ Blue Book recommends 575°F for the temper temperature in order to hit min mechanicals.

Anyone with more experience designing with this specific material have any insight/advice on what to temper to?


RE: AMS 6411H 4330MOD Temper Temperature

It depends on the exact chemistry of your material and the previous thermo-mechanical history.
Such details are not part of the material spec, they do fall under 2759/2F, and they do kindly give you a place to start.
I know of critical applications where the temper temperature is verified on samples before every production run.

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

RE: AMS 6411H 4330MOD Temper Temperature

After consulting AMS2759/2F, I see that they list the tempering temperature as 500°F with the caveat that it's only a "suggested temperature only."

A lot depends on the experience of Your heat treater. They will need to analyze the material certs, their time-temperature history and the actual hardness of each HT LOT after the Aus-Quench operation.

This will then enter the world of the 'heat-treaters art': their experience and judgment will lead them to suggest a target tempering temperature for the first temper operation. After that first temper they will evaluate the results as-to how close they came to the target Rockwell hardness. IF needed they can adjust the tempering temperature to close-in on the target hardness during the second Tempering operation. NOTE. Sometimes 'practice makes perfect'... so be patient.

I usually add 'wiggle words' for the tempering operation that allow heat-treater's discretion RE tempering temperatures; provided that hardness readings sampled all-over the raw part fall within an agreed-upon range of min-max RHC readings.

CAUTION. I STRONGLY URGE that each part, and EACH HT coupon, be serialized [etched or CRES-tagged] to ensure traceability. LESSON LEARNED!

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", forum]

RE: AMS 6411H 4330MOD Temper Temperature

Good words to the wise. Keeping serialization and lot control is the difference between and issues and a disaster.

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P.E. Metallurgy, Plymouth Tube

RE: AMS 6411H 4330MOD Temper Temperature

Will and Ed,

Sorry for the late reply. Your advice is well taken. I have a pretty good repore with my heat treaters so I'll be leaning on them heavily. That's why they're the experts right?


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