plating, anodizing, & finishing Q&As since 1989
316L Stainless Steel is too springy
Q. I'm Girius, a specialist in design and manufacture of medical devices for Australian wildlife.
I have a project that requires the use of 316L stainless steel half rings that will be closed to full rings. I was wondering if there was away to remove some or ALL the springiness from 316L stainless steel, but without compromising its corrosion resistance? When the half rings are closed, they never quite fully close due to spring-back.
If there is an easy method to achieve this, please let me know. I am not concerned about the the final stiffness or strength.
- Melbourne Australia
March 4, 2022
A. Hi Girius!
You can heat up to 1100 °C in a furnace and throw the hot rings to water, the steel will lower its hardness. We have done it for cold forged bolts, we needed to cut the hex head but its hardness was higher than 33 HRC, so we couldn't. With this treatment AISI 316L lowered its hardness to 80 HRB and could be cut without any problem.
Later, you will be needing to pickle and passivate with nitric acid to make the surface bright and corrosion resistant again!
Best of luck!
- Cañuelas, Buenos Aires, Argentina
January 3, 2023
A. Hi Girius,
Springback is a result of material properties, specifically the elastic region of the stress strain relationship (curve). You "may" be able to reduce the springiness of the rings by heat treating them, but that depends on the state of the rings as received, you won't be able to get them below a certain level of springiness (without altering the effective composition).
The usual way to account for the springback is to overbend the pieces. This will have no effect on the corrosion resistance, and is simple and easy to do, however the design does need to account for this. The amount of overbending needed is consistent all other things constant (material, thickness, bend parameters).
I suspect that if you bought the half rings off the shelf then they would already be in their annealed state, otherwise you could ask your supplier what the temper of the rings is.
- Ballarat, Australia
October 16, 2023
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