AMS H6875 Needed on Drawings? 2

[SwaggingIt]

Hi. Havent posted on here since college...

I'm working with a lot of stainless steels and our material callout on drawings include "... HEAT TREAT PER AMS-H-6875..." in addition to calling out the H condition using the AMS standard for that specific material such as AMS 5659 for 15-5PH. For example, an entire callout for 15-5PH is “15-5PH PER AMS 5659. HEAT TREAT PER AMS-H-6875, CLASS D, COND. H1025”.

My questions is that isn't calling out AMS-H-6875 redundant because we already state the H condition we want the material to be? And the AMS specific standard, such as AMS 5659, states the hardness, strength, and quality assurance requirements so theres really not much calling out AMS-H-6875 is doing for us except maybe handcuffing us to that specific standard.

But I'd love to hear from any material experts on whether or not we should keep that heat treat callout on our drawings. Thank you!

- Luke

 

[SWComposites]

What is the issue that makes you want to delete the heat treat callout? I see no harm in including it. What is the specific application?

 

[SwaggingIt]

I'm at a small company where turn over has been high the past year+ so nailing down the history of why things the way they are isnt always easy. We work in aerospace/defense. Part is a gearmotor.

The concern around including AMS 6875 is that it might constrain our vendors to that specific heat treat standard which may increase lead time and price. When it may not be needed since the material properties and quality is called out in the material specific AMS standard, so calling out AMS 6875 is just being redundant at best, constricting our supply chain at worst.

Then again, perhaps AMS 6875 is the de facto standard for raw steels that vendors use anyways, so whether we call it out or not makes no difference. This is what I'm not sure of which drives all my other questions. I have the question out to our vendor, but was hoping for input from any material experts as well. Thanks.

 

[Ti_Metallurgist]

My take is that AMS 5659 specifies the material composition, and provides a recipe for heat treating to the solution treated condition. There are basic guidelines for heat treating samples of the solution treated material to verify that it has the capability to achieve precipitation hardened properties, H900 - H1150. The true heat treat specs have much more detail to ensure consistent processing of the full size bars or parts, and includes many more quality assurance requirements. AMS-H-6875 is pretty much the standard for heat treat of raw materials, and I don't believe specifying it will restrict your supply chain options. It was technically superseded by AMS 2761 but is still called out everywhere. AMS 2759/3 is what you would typically call out for machined parts.

 

[EdStainless]

Do either of those spec refer to AMS 2750?
This is the spec on furnace class, control, and calibration.
AMS 2759/3 J is the current revision. This is PH material specific.
AMS 2761 is for raw material and in most cases explicitly states that the material is not to be used in that condition.
AMS 6875C is not for use in any new parts since it has been stabilized. It also is focused on HT of raw material.

We haven't done it 15-5PH yet, but most of the other PH alloys have been re-written so that there is a "/" spec for each heat treat condition.
So for 17-4PH there is AMS 5622/1050 and then 6 others with the condition noted.
We have also done this to AMS 5934 for 13-8PH.

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P.E. Metallurgy, consulting work welcomed

 

[SwaggingIt]

Thanks for all the info.

I was reading AMS 2759/3 yesterday and its pretty similar to AMS H6875. When should you callout one versus the other?

And to put this thread to bed so I can get my drawings out to procurement this week... Do you guys see any issue with leaving AMS H6875 (or AMS 2761) off the drawing? I would still callout AMS 5659 in the case of using 15-5PH. Or would you guys prefer to see a heat treat callout on the part drawings?

You guys have been a big help. We need a materials SME at my company...

 

[mrfailure]

I ran across these questions recently with regard to FA of a pH steel. H-6875 applies to the raw material heat treatment while 2759/3 is for heat treatment of parts.

You cannot take a shortcut by assuming any heat treatment that achieves the specified properties for 5659. You are required by the drawing to actually have the heat treatment of the raw material be performed in accordance with H-6875, It would be a huge red flag from a quality standpoint if you did not certify this was done. I would not accept the material for any aerospace or military applications if I was the customer.

 

[SwaggingIt]

Thanks @mrfailure.
I control what goes on the drawing. So the question remains, should I include AMS-H-6875 (or 2761) or is 5659 enough since it lists the H condition?

Half of me wants to leave it off because 5659 with the H condition implies heat treatment to 6875 (or 2761).
Other half of me wants to include it because we're in aerospace/defense and we need to exhibit traceability/control of all processes.

 

[EdStainless]

Do not put AMS 6875 on the drawing. It will never be revised again and will become history only.
The most correct path is to list 5659 (material), 2761 (RM HT), and 2759/3 (finished part HT).
Unless 5659 explicitly refers to either of the others they should be listed.

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P.E. Metallurgy, consulting work welcomed

 

[SwaggingIt]

Thanks Ed. Our quality dept fully agrees with you. So shall it be done!