×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Nitronic 50 HS stress relief?
2

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

RE: Nitronic 50 HS stress relief?

If you stress relive you will change the properties.
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?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Nitronic 50 HS stress relief?

(OP)
Ed,
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?

If not explicitly prohibited, you may go ahead to do stress relief annealing, but i would use a bit lower temp, say 850F. This alloy has a high work-hardening rate, it needs <15% cold work to get 120ksi yield, the material is not so heavily cold worked. Stress relief at relatively low temp can decrease the strength a bit, but not too much, probably less than 5 points.

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?

We have used long soaks at 800F (~1hr) for stress relief. We could see the charge in properties but it wasn't much.
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.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close