Partial Stress Relief of HS Alloys steels
Partial Stress Relief of HS Alloys steels
(OP)
Help.. I am fully aware of stress relief procedures for high strength alloy steels (IE: part of AMS2759/2 for instance). However, recently, I was presented with a "generic" partial stress relief process [350F--400F] for use with HS aerospace steels (180--300KSI, IE: 4330M, 4340M, 300M, etc), as part of an overhaul process for HS parts [IE: landing gear, flap tracks, etc]. The obvious benefit is avoiding damage to platings and minimal affects on residual stress mechanisms [IE: shot-peening and hole cold-working]. HOWEVER... I can find no specs, tech data, literature, etc, justifying the benefits of this process. To me, this just sounds like prophylactic hydrogen embrittlement relief [IE: same as ASM2759/9]: but I'm informed that this is NOT the intent of this procedure... and that real stress relief is occuring. Anyone have ref info/data/etc on "partial stress relief" procedures?????
Regards, Wil Taylor
Regards, Wil Taylor





RE: Partial Stress Relief of HS Alloys steels
I think all these alloys are in the
"Aerospace Structural Metals Handbook"
http://www.cll.purdue.edu/extendeduniver...
This is a very expensive set of handbooks but have everything allowed with Aerospace Metals. Check around to see if can get to a copy.
You might be able to find a heat treating book at the
www.asminternational.com
RE: Partial Stress Relief of HS Alloys steels
This if for the Aerospace Structural Metal Handbook
http://www.cll.purdue.edu/extendeduniver...
This for a book Structural Alloys Handbook
http://www.cll.purdue.edu/extendeduniver...
What is not covered in one is covered in the other
RE: Partial Stress Relief of HS Alloys steels
I purposefully reviewed the CINDAS-ASMH**, numerous heat treating specs, ASM handbooks, library reports on HSA steel, etc... before asking this question. All have no significant references to a low temp stress relief. Stress relief is invariably defined as being 50F below the KNOWN (or if unknown, spec-minimum) temering temperature.
I did find references to hydrogen re-embrittlement of HSA steel, due to the inevitable porosity of platings and oreganic coatings (after many years of service)... implying that a hydorgen relief bake during overhaul would be beneficial, similar to AMS2759/9. But in some cases this was considerd a theoretical problem... not warrented by inservice problem/failure data.
Regards, Wil taylor
CINDAS-ASMH*** provides excellent metallurgy info + mechanical values... definite companion to MIL-HDBK-5.
Regards, Wil Taylor
RE: Partial Stress Relief of HS Alloys steels
Wil,
When did you get back to Eng-Tips? The guys would love to hear from you on the "mental challenge" thread you started last year. So sorry about your mother. Welcome back.
Miper
RE: Partial Stress Relief of HS Alloys steels
Thermal effect = T (log t + 20)10-3
Low temperature stress relieving is frequently performed on components fabricated from high strength steel alloys, especially those that are formed. Cold wound/coiled springs are the items with which I have the most experience. Standards such as SAE J217 and J230 have a requirement for the springs to be stress relieved at a temperature of 230-260 C for 30 minutes. I am sure there are some SAE aerospace standards that are similar. Raytheon has a standard (BS25526) that has similar requirements. The old military standard MIL-S-6715 had a requirement for stress relief of 250 F for 1 hour.
In general, springs fabricated from patented & cold drawn steel wire (music wire) are stress relieved at 190-230 C, oil tempered carbon springs at 260-400 C, and oil tempered alloy springs at 315-425 C. I could not find any standards that cover this type of treatment, mainly because there are no universally-used standards for mechanical springs. However, all spring design handbooks discuss this topic.