Nitronic 50 HS stress relief?
Nitronic 50 HS stress relief?
(OP)
Hello,
The company I work for is manufacturing (on contract; we do not own the design) several components from Nitronic 50 HS (120 ksi yield). To ease our machining operations, it has been proposed that a stress relief (900F, 1 hr/inch of thickness) be performed partway through the machining. I don't have any experience with stress-relieving heavily cold-worked materials, so I am concerned about the following points, based on my current (admittedly limited) understanding of metallurgy.
Potential concerns:
1. Potential loss of yield/tensile strength due to the stress relief
2. Sensitization from carbide precipitation
Can anyone provide some guidance as to how valid these concerns are, or point me towards some reference material to digest? The application is for the Oil/Gas industry, if that helps.
Thank you
The company I work for is manufacturing (on contract; we do not own the design) several components from Nitronic 50 HS (120 ksi yield). To ease our machining operations, it has been proposed that a stress relief (900F, 1 hr/inch of thickness) be performed partway through the machining. I don't have any experience with stress-relieving heavily cold-worked materials, so I am concerned about the following points, based on my current (admittedly limited) understanding of metallurgy.
Potential concerns:
1. Potential loss of yield/tensile strength due to the stress relief
2. Sensitization from carbide precipitation
Can anyone provide some guidance as to how valid these concerns are, or point me towards some reference material to digest? The application is for the Oil/Gas industry, if that helps.
Thank you





RE: Nitronic 50 HS stress relief?
I am fairly sure that the spec does not allow any thermal treatment after the material has been cold worked to the correct properties.
If this is 120ksi min Yield then it is likely 140-160ksi UTS.
What trouble are you having?
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P.E. Metallurgy, Plymouth Tube
RE: Nitronic 50 HS stress relief?
Thank you for confirming my suspicion that this is likely not an acceptable practice, at least not without prior customer approval.
You are correct; the spec does not specifically allow for stress-relief. It does not explicitly prohibit it, but I figured there was a reason for the lack of stress-relief information available for this material, either in the spec or online.
Is the sensitization an issue as well?
To answer your other questions:
Yes, this is 140 ksi min UTS.
Issues are with distortion during/after machining' likely due to asymmetrically relieving internal stresses. The parts are long and thin, and tend to look like they're practicing their cursive after a long milling operation. We are able to reduce the distortion to an extent by modifying our machining methods, and can straighten them if they get too bad, but it is time-consuming to do so.
RE: Nitronic 50 HS stress relief?
As for sensitization, i donot think 850F is high enough to have a noticeable effect, especially given that this alloy has Nb that will tie up with carbon.
RE: Nitronic 50 HS stress relief?
Could you clamp the finished parts (either to each other or to a fixture) and SR after machining?
The tubing spec for similar alloys says that properties shall be achieved through cold work only.
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P.E. Metallurgy, Plymouth Tube