Can a sheet metal 'pre-temper' fix warping during quench?
Can a sheet metal 'pre-temper' fix warping during quench?
(OP)
I have done a lot of forming on a sheet metal part, and its ready for heat treat. I need to minimize warping during the quench and temper.
To discover and fix potential warping, ideally I'd normalize and straighten the warm part several times before final hardening heat treat. Well, you can't normalize sheet metal w/o scaling / decarb issues, so i thought of this..
Stress relieve the part first by tempring just above Ms temp (710F for 4130) for a couple of hours, then look for warping as the built up stresses relax. It wont cause the bad scale formation, and it could give me a preview of warping. I could then make the necessary straightening while it cools from temp, then re-stress relieve at 725F again.. repeat until i have no warping.
What are some other ways to stop warping? I use a molten salt quench and I do a version of Austempering to avoid the warping from Martensite.
To discover and fix potential warping, ideally I'd normalize and straighten the warm part several times before final hardening heat treat. Well, you can't normalize sheet metal w/o scaling / decarb issues, so i thought of this..
Stress relieve the part first by tempring just above Ms temp (710F for 4130) for a couple of hours, then look for warping as the built up stresses relax. It wont cause the bad scale formation, and it could give me a preview of warping. I could then make the necessary straightening while it cools from temp, then re-stress relieve at 725F again.. repeat until i have no warping.
What are some other ways to stop warping? I use a molten salt quench and I do a version of Austempering to avoid the warping from Martensite.





RE: Can a sheet metal 'pre-temper' fix warping during quench?
RE: Can a sheet metal 'pre-temper' fix warping during quench?
A few threads ago we discussed the 'upquenching' method of austemper.. to introduce a duplex structure of martensite.
By dipping below Ms a bit, then coming back up above Ms and holding in molten salt i get the benefits of even transformation and the huge toughness increases, Kic increases, crack propagation rate slows, (and yield srenght increaes via Hall Petch) that a duplex structure of Martensite and lower bainite can give!!