Why does AMS2759 require tensile testing of 17-4 H1100-H1150? 2

[BillCPE]

AMS2759/3 paragraph 4.1.1 requires tensile tests for 17-4PH aged from 1100F to 1150F. Hardness testing is sufficient for other aged conditions.

Why? What tensile test properties may vary in these conditions?

Thanks!

 

[tbuelna]

Might be a legacy requirement from the old MIL-H-6875 spec. Take a look at the attached 3.3.2 section of MIL-H-6875. 17-4PH is considered a class D steel.

 

[BillCPE]

Yep, the same requirement is in MIL-H-6875. So why does 6875 require tensile testing for the 1100-1150 aged conditions?

And while we're at it, why does 6875 require tensile tests for parts that are resolution annealed? 2759 says tensile tests are required for resolution annealed parts when required by the purchaser, but 2759 only allows a single resolution anneal. What is it about the annealing/aging cycles that is not reliably reversible?

Thanks!

 

[EdStainless]

In general PH SS undergoes grain refinement with each anneal/age cycle.
You generally see a slight drop in strength each time with an improvement in toughness. I have used this trick to meet impact properties.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[MagBen]

three other reasons:
1. 1100-1150H aver-aged has a comparable hardness with solution treated, A, condidtion, while tension properties are very different. so tensile tests are required to distinguish these two conditions.
2. 1100-1150H have the most difficult tension properties (elognation, tenisle, yield etc) to achieve.
3. upon purchaser requirements.

 

[mrfailure]

The way I read this spec, the wording regarding tensile strength is somewhat nonsensical:

"When tensile tests are required, results shall conform to the specified values. When tensile properties are not specified, they shall conform to those specified by the applicable material specification."

Since 2759/3 is the applicable spec, I would interpret this wording as meaning all aging treatments require tensile testing and have to meet the requirements of Table 7. The only difference is 1100-1150H tensile specimens have to be machined before solutionizing but tested afterward.

 

[BillCPE]

EdStainless, I read one of your previous posts talking about Charpys when I searched to see if my question had already been answered. Nice tool to add to my bag of tricks...

MagBen, I think you're right on track. Overlapping hardness with condition A should have been an obvious clue but I missed it...

mrfailure, I thought that was a bit nebulous too when I first read it, but I think the material spec is the ASTM spec such as ASTM A564 or A693.