Heat treatment of Custom 455 and 17-4PH s/steel
Heat treatment of Custom 455 and 17-4PH s/steel
(OP)
Hi. Can anyone help with this heat treatment question?
As part of a heat treatment validation exercise I have measured hardness of materials following the recommended cycle
In the case of Custom 455 S/Steel, the Carpenters Data Sheet states that the maximum material strength is achieved by age-hardening to condition H900 (4 hours at 900oF and air cooled). A hardness of ~ 47-49 HRC is achieved at this condition.
However, I am measuring up to 57 HRC for some components
1)How has this happened? Could it be due to the temperature being too low?
2)If greater hardness than 47-49 HRC is achievable, why do Carpenters not recommend this as a standard cycle?
Additionally, I have experienced similar effects with Stainless Steel 17-4PH. Data sheets suggest that the maximum achievable hardness is 44 HRC, whereas I have measured up to 54 HRC (H900. 1 hour and air cooled).
Any help or explanation would be much appreciated.
Ian
As part of a heat treatment validation exercise I have measured hardness of materials following the recommended cycle
In the case of Custom 455 S/Steel, the Carpenters Data Sheet states that the maximum material strength is achieved by age-hardening to condition H900 (4 hours at 900oF and air cooled). A hardness of ~ 47-49 HRC is achieved at this condition.
However, I am measuring up to 57 HRC for some components
1)How has this happened? Could it be due to the temperature being too low?
2)If greater hardness than 47-49 HRC is achievable, why do Carpenters not recommend this as a standard cycle?
Additionally, I have experienced similar effects with Stainless Steel 17-4PH. Data sheets suggest that the maximum achievable hardness is 44 HRC, whereas I have measured up to 54 HRC (H900. 1 hour and air cooled).
Any help or explanation would be much appreciated.
Ian





RE: Heat treatment of Custom 455 and 17-4PH s/steel
RE: Heat treatment of Custom 455 and 17-4PH s/steel
Search here for other discussions of PH stainless steels. (Also mcguire and israelkk and EdStainless will be around in a bit I'm sure)
Here are some data sheets:
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Nick
I love materials science!
RE: Heat treatment of Custom 455 and 17-4PH s/steel
The hardness testing is carried out by a sub-contract supplier so this could be a bit sketchy.
I believe that the tests are carried out using Vickers testing apparatus with a 5kg load. The results are then converted from Vickers to Rockwell C scale.
Hope this helps. If not I can get specific details.
Cheers
Ian
RE: Heat treatment of Custom 455 and 17-4PH s/steel
RE: Heat treatment of Custom 455 and 17-4PH s/steel
You might also try the data at
http://www.alleghenytechnologies.com/ludlum/
Select the alloy of interest and then look at the Blue Sheet for it.
But, to your point. You always need to reanneal PH grades in order to control the properties.
My guess is that if you are seeing such harnesses that the ductility is zero. It could be from prior cold work and you are in effect getting CH material. It could also be because of odd microstructure after the previous anneal.
For recent 17-7 jobs we have been using the RH treatment that requires -100F within 1 hour of the anneal. This has improved both the strength and ductility.
= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Heat treatment of Custom 455 and 17-4PH s/steel
Unfortunately I do not have the MIL standard. I will have a look online.
I have taken your comments on board and am currently awaiting a response from Carpenters.
Many thanks
Ian
RE: Heat treatment of Custom 455 and 17-4PH s/steel