17-4PH 1

[dho]

this material can have so many heat treat conditions. H900, H1025, H1100........
i have one very small part, H-1025. i checked HRc, it reaches 44, higher than AMS spec. but as you know HRc is just for reference, not a base for rejection. (tensile listed as minimum)
what other metallurgical way to nail down the heat treat condition, as H-1025 relative lager elongation is critical to my application.
thanks.

 

[metengr]

If the part is too small for destructive mechanical testing for additional information, you have what you have.

 

[EdStainless]

In the past I have had a similar problem, I took one part (the lot had a dozen pieces) and re-aged it at 1025. The hardness should be unchanged or go down a point. If it drops 4-5 points then they were aged at a lower temp the first time.

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P.E. Metallurgy, Plymouth Tube

 

[redpicker]

I agree with EdStainless, If the hardness is on the high side, re-aging at the correct aging temperature will not be detrimental and will only improve the ductility.

 

[israelkk]

17-4PH H-1025 can have a range of 10RC variation. Therefore, you could get 34-44RC. 17-4PH H-1025 is never guarantied for hardness but only for minimum yield and ultimate tensile strength. See MIL-HDBK-5J or AR-MMPDS-01 for example.

For every batch of heat treat and material heat lot you may get different hardness results. Therefore, when you specify standard heat treatment of H-1025 do not expect strict hardness results. If you ask for hardness then the heat treatment is not standard and is not guarantied by the spec.

 

[MagBen]

Hardness control might not that bad for 17-4 H1025, especially for strip and plate products.

For strip and plate:
AMS 5604E specifies 35-42HRC
ASTM A693: <.1875'' 35-43, .1875-4.0'' 33-42

For bar:
AMS 5643 34-42 (hardness is not a basis for rejection)
ASTM A564, A705 MIN 35HRC

There are complicated HT, but the tendency is pretty clear: as the aging temperatures increase, hardness, tensile, yield decrease, while elongation, impact strength increase.

when hardness=44hrc, the aging temperature was probably lower than 1025F.

 

[EdStainless]

Or the particular lot chemistry puts you right at the top of the strength range.
We always used both strength and temperature in our spec (not AMS restricted).
If the material was on the high side of the strength we would re-age at a higher temp.
We were looking to meet a min. strength and get maximum toughness.

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P.E. Metallurgy, Plymouth Tube

 

[dho]

from all threads here, the conclusion is that there is no way to verify the H1025 was done right or wrong (aging temp off spec).
right?

 

[EdStainless]

Unless you thought ahead and had test coupons (cur from the same lot of material) heat treated along with the parts, no you can't tell. With your high hardness the min elongation would be the telling factor.

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P.E. Metallurgy, Plymouth Tube

 

[MagBen]

I would first point to lower temp, but cannot exclude other factors (heat chemistry, solution HT, or even test itself). In engineering world, jumping to a conclusion based on one test point, one smaple piece is danger.

 

[EdStainless]

I would still take a few pieces and re-age them at 1025F.
However you need to be careful to not jump to conclusions.
Given the tolerance in aging temperature, and how steep the strength vs temperature curves are in this region you could easily get a change. Say the original aging was at 1015, and you re-age at 1035. Based on published cures that should produce a change of 3-4 points RC.
But if you re-age and can assure that parts never exceed 1025, and you get more than a 5 point drop then I would be concerned.

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P.E. Metallurgy, Plymouth Tube

 

[dho]

need HELP, HELP !!
AMS5643, table 2. "elongation in 4D".
what 4D stands for?
thanks.

 

[MagBen]

4D = 4x diameter of the test specimen. So if you tension specimen diameter is .5'', the length to be measured is 2''.
so a strip specimen (dog bone), elongation in 2'' or 4W is used. w = width of strip.

 

[dho]

thank MagBen and all.