15-5PH Questions

[Veranium]

Does all 15-5 need to be cooled to 70F? We are wondering at my company if cooling 15-PH to 40F or below would give us better mechanical properties?

We usually get material that is with the .5-.7 range. My previous company used to require that we always held our manganese within the .75-.9 range. Is there any benefits in control the Mn or any of the alloying elements mainly Cr and Ni.

Thank you

 

[WKTaylor]

WHAT SPECIFICATION are You procuring Your material per [ASTM, AMS, etc].... and what form... Casting, plate/sheet, extrusion, bar, forging [etc]??????????

What is the SOURCE [country/company of origin]??????????

Are You receiving reliable material certification [test, chemistry, etc] documentation from the OEM's test lab... or an independent test lab????????

What heat-treat specification [processes] are You using? ASTM, MIL, AMS...????????? What is Your intended heat treatment tensile range or [Hxxxx] condition??????????


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", Homebuiltairplanes.com forum]

 

[EdStainless]

Based on the chemistry you can calculate the martensite transition finish temperature.
As long as you get below this and stay there for a few hours you will be fine.
Is this material was made to the AMS spec, and it was annealed properly, and it has not been cold worked, then the Mf temp should be roughly 100-120F.
So 70F is adequate. The original Armco data sheet says cool below 90F.
I have seen heats made poorly that had Mf below 30F.
This is not good material.
The real test is to run some test bars.
The final properties are a function of both annealing and aging.
15-5 is a modified version of 17-4 that is used to get good toughness in thick sections.
It is not uncommon to double HT this material, first into the overaged (H1150M) condition and then re-anneal and age to final properties.
If there is ever any chance that this will see any possible corrosive conditions make sure your final age is 1050F or higher.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Veranium]

WKTaylor (Aeronautics)12 Aug 22 04:10
WHAT SPECIFICATION are You procuring Your material per [ASTM, AMS, etc].... and what form... Casting, plate/sheet, extrusion, bar, forging [etc]??????????
Forging Billets, AMS5659S
What is the SOURCE [country/company of origin]??????????
I work at Forging operation now so i do not know the actual source of the raw material but the billets were made by an US company.
Are You receiving reliable material certification [test, chemistry, etc] documentation from the OEM's test lab... or an independent test lab????????
From the OEM's lab per ASTM A751
What heat-treat specification [processes] are You using? ASTM, MIL, AMS...????????? What is Your intended heat treatment tensile range or [Hxxxx] condition??????????
40-43HRC
180-200KSI
Solution and Aged condition is a requirement from customer spec we are using.

 

[EdStainless]

No elongation or impact toughness requirement?
I'll just add that AMS has 'stabilized' all of the PH SS specs for high strength conditions.
They can still be used for legacy applications but they are prohibited in new designs with a lot of special actions.
They are so susceptible to hydrogen embrittlement and SCC that they are discouraged from being used.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Veranium]

"EdStainless (Materials)12 Aug 22 15:36
No elongation or impact toughness requirement?
Our Fracture toughness requirement is a 77KSi min(K1C)
Elongation is 10min
RA is 38min
I'll just add that AMS has 'stabilized' all of the PH SS specs for high strength conditions.
They can still be used for legacy applications but they are prohibited in new designs with a lot of special actions.
They are so susceptible to hydrogen embrittlement and SCC that they are discouraged from being used."

Which alloys should I be looking at to get the best results mechanically? We cannot change too many things in how we process the part so our main improvements will have to come from Chemistry and forging process because Heat treat cannot be touched. We have leeway to cool the parts below a certain temperature.

I am no expert but I believe my best bets at improving our mechanical results are to control supplier chemistry and determine if our cooling method is enough to transform the microstructure quick enough.

 

[EdStainless]

I'll just say that I have seen a lot of spring applications in very high strength PH grades (17-7 CH900 and such) that would be better served using a fluoropolymer coated steel.
In the higher strength conditions (aging below 1025F) the PH grades still have good general corrosion resistance.
But when any corrosion does occur the resulting pitting and hydrogen generation has a high probability of leading to catastrophic failure.
If good corrosion resistance and high strength are both needed break down and look at age hardening Ni alloys.
With 15-5 and 17-4 parts that required good toughness and elong (especially transverse) we frequently double heat treated them.
First into the overaged condition (H1100M) and then re-annealed and final aged. We occasionally had to work at the very lower edge of the allowed temp (-25F) because the strength would be down slightly, but with many heats they were over strength enough that we could even re-heat treat and work at +25 and still easily meet strength.
Tip 1, test the heat and know its actual aging response. We quoted these jobs to a required minimum strength, not a specific aging temp. This way we could age then as hot as possible to improve toughness and ductility.
Tip 2, the cooling rate is not very critical

The reason that some specs say cool to 90F vs 70F before aging is related to where person writing the instructions worked. If they worked in a mill they saw 90F as below Mf and cool enough. If they worked in an air conditioned office then they thought of 70F as 'room temp'. You really should hold them cooled for a while though before you age.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Veranium]

"EdStainless (Materials)16 Aug 22 19:50
I'll just say that I have seen a lot of spring applications in very high strength PH grades (17-7 CH900 and such) that would be better served using a fluoropolymer coated steel.
In the higher strength conditions (aging below 1025F) the PH grades still have good general corrosion resistance.
But when any corrosion does occur the resulting pitting and hydrogen generation has a high probability of leading to catastrophic failure.
If good corrosion resistance and high strength are both needed break down and look at age hardening Ni alloys.
With 15-5 and 17-4 parts that required good toughness and elong (especially transverse) we frequently double heat treated them.
First into the overaged condition (H1100M) and then re-annealed and final aged. We occasionally had to work at the very lower edge of the allowed temp (-25F) because the strength would be down slightly, but with many heats they were over strength enough that we could even re-heat treat and work at +25 and still easily meet strength.
Tip 1, test the heat and know its actual aging response. We quoted these jobs to a required minimum strength, not a specific aging temp. This way we could age then as hot as possible to improve toughness and ductility.
Tip 2, the cooling rate is not very critical

The reason that some specs say cool to 90F vs 70F before aging is related to where person writing the instructions worked. If they worked in a mill they saw 90F as below Mf and cool enough. If they worked in an air conditioned office then they thought of 70F as 'room temp'. You really should hold them cooled for a while though before you age."

We have an outside source testing the material.
So you do not think chemical requirements are necessary to boost the mechanical properties?
Cooling rate doesn't matter so whether its placed into a freezer or air cooled?
Also due to the customers process we cannot change anything related to how the part is heat treated before quench only have leeway with quench to due circumstances.

 

[EdStainless]

We always considered re-heat treating permissible, after all what would you do if you encountered a control or power stability issue.
Aging and then reanneal and age results in grain refinement. This is why it improves toughness and elong.
Yes the chemistry matters, but rather than try and lock a tighter chemistry (which no mill will commit to) you adjust the temperatures.
In some cases we altered both the annealing and aging temps slightly, usually within +/-25F.
We tested samples from every heat lot and made the adjustments.
You don't want to freeze this alloy after anneal, it will finish transformation better if it is at room temp.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[WKTaylor]

V... In addition to every thought already presented by our esteemed collogues... my humble 2-cents...

IF You are using AMSxxxx 15-5PH SStl, and are aiming to attain mechanical allowables per MMPDS-*, then it is wise to HT per latest version of AMS2759 and AMS2759/3.

There is very specific language for every aspect of steel/SStl [most-all 'flavors'] HT in AMS2759G and AMS2759/3J... which has been derived by real-world metallurgists', heat-treaters' and high-volume end-users/aero-OEMs thru many years of hard work in their shops for the aero-industry... and subsequent hard work in SAE committees to derive 'details' that would drive most of us ordinary-mortals 'insane'.

I salute EdStainless for his knowledge/contribution

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", Homebuiltairplanes.com forum]

 

[Veranium]

@WKTaylor and EdStainless

Thank you guys so much for the information I will probably comeback here once this order is processed but I will attempt to tackle the Heat treating aspect and then work on checking chemical correlations.