Assessment of Residual Stresses via Charpy Test.
Assessment of Residual Stresses via Charpy Test.
(OP)
Hello Everybody !
We have a large component (fabricated via S.A.W in ASTM A 36) which needs some large welding to be developed at the port site due to transportation reasons. The weldment will be connecting two cilindrical bodies (like two "cans")which are 7.3 meters in diameter and 17 meters long (8.5 meters long each can). As neither localized stress relieving nor furnace stress relieving is possible to be developed at site (and even if it was possible , there would be distortion issues due to time and temperature) , I was suggested to run test plates under the same conditions of the actual weldment and then run charpy tests on each mock-up (one with and the other w/o. stress relieving treatment). The CVN values would then be compared in order to show whether residual stresses may or may not be detrimental to the actual components.
The question is ; Is that a reliable test to evaluate the level of residual stresses for a component which has not been stress relieved ? NOTE: Vibratory stress relief is not acceptable per the customer`s spec.
We have a large component (fabricated via S.A.W in ASTM A 36) which needs some large welding to be developed at the port site due to transportation reasons. The weldment will be connecting two cilindrical bodies (like two "cans")which are 7.3 meters in diameter and 17 meters long (8.5 meters long each can). As neither localized stress relieving nor furnace stress relieving is possible to be developed at site (and even if it was possible , there would be distortion issues due to time and temperature) , I was suggested to run test plates under the same conditions of the actual weldment and then run charpy tests on each mock-up (one with and the other w/o. stress relieving treatment). The CVN values would then be compared in order to show whether residual stresses may or may not be detrimental to the actual components.
The question is ; Is that a reliable test to evaluate the level of residual stresses for a component which has not been stress relieved ? NOTE: Vibratory stress relief is not acceptable per the customer`s spec.





RE: Assessment of Residual Stresses via Charpy Test.
Michael McGuire
http://stainlesssteelforengineers.blogspot.com/
RE: Assessment of Residual Stresses via Charpy Test.
No. The level of residual stress cannot be determined in this application using CVN impact testing.
RE: Assessment of Residual Stresses via Charpy Test.
What is the thickness of the cans? Post weld heat treatment of carbon steels is really based on wall thickness versus OD or geometry. Can you come back with some information on wall thickness?
Also, you can elevate preheat during welding to reduce susceptibility of residual stresses from welding.
RE: Assessment of Residual Stresses via Charpy Test.
RE: Assessment of Residual Stresses via Charpy Test.
Here you go :
1. Cans are 2.5" - thick. Full penetration weldment , with backgouging.
2. The connecting welding at site has not taken place as yet.
3. We are aware of those methods to measure R.S ; however, we want to avoid S/R due to high risks of distortion.
4. S.A.W is a welding process with high heat input , and that concerns a lot.
5. Vibratory S/R as mentioned before is not allowed.
6. Any ideas ?
Thank you.
RE: Assessment of Residual Stresses via Charpy Test.
I just completed a review of an EPRI report for one of the code committees with regard to changing the current PWHT exemption for P-No 1 base material from ¾” to 1.5” with preheat. Even at a 2.5” thickness with increased preheat, the level of residual stress would be lowered and you would significantly reduce the hardness in the base metal HAZ from tempering benefits associated with the higher heat input AND preheat.
RE: Assessment of Residual Stresses via Charpy Test.
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Assessment of Residual Stresses via Charpy Test.
In case the code does not allow me to use metengr`s suggestions , where can I obtain British Std. 7910 ?
RE: Assessment of Residual Stresses via Charpy Test.
ASME Section IX does not provide any guidance for design engineering of welds. It is simply a guide for weld procedure and welder qualification. The elevated preheat/temper bead information I had provided to you is referenced in the National Board Inspection Code, which is an in-service repair code for pressure retaining items.
RE: Assessment of Residual Stresses via Charpy Test.
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Assessment of Residual Stresses via Charpy Test.
metengr - in case I follow your welding thecnique suggestions, I may avoid to s.relieving ; however , still very prone to higher distortion risks than the usual heat input and preheating temperature used during the conventional process of manufacturing of the "cans" - Is it correct ?
SJones - Did I understand correct that in case I get the British Std. 7910 , I will be able to estimate side effects by assuming yield strength magnitude of R.S ?
RE: Assessment of Residual Stresses via Charpy Test.
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Assessment of Residual Stresses via Charpy Test.