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Need information on metal strap with no (very little) work hardening.

dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
My adult son and I are brainstorming a device that would require a strap of metal which could be bent into a flattened “C” shape, straightened, and re-bent many (hundreds?) of times without work hardening and breaking. As an example of the desired stiffness, think of a ribbon of soft between 20 and 16ga steel 1” wide and 12” long. Used a few times, such a piece would do nicely. But eventually it would harden and break.

I‘ve done a bit of searching the web and have come across a few “exotic” (to me at least) alloys like MPN35 that might have the desired work hardening resistance. But, so far, I can not get a sense of their cost, workability, or their availability. I imagine a few folks here will have had some practical experience with metals that might fit our requirements. So, I’d love to hear suggestions, cautions, and guffaws, if appropriate.

Denis
 
Is there a reason why conveyor belt chain cannot be used in your design?
Yes, lightness, thinness, and the ability to temporarily hold the flattened configuration are needed just like the the bendable tab on a Manila envelope holds its position temporarily.

Denis
 
a strap of metal which could be bent into a flattened “C” shape, straightened, and re-bent many (hundreds?) of times without work hardening and breaking.
Depends on how smart your users are, how many times, how easy the strap is to replace etc but copper is really easy to anneal. People do that for head gaskets and so on all the time.
 
Buy a flexicurve, the core is square lead with a tin strip edge, lead recrystallises at room temperature.
The tin is to prevent bending in 2 planes.
Common enough drawing aid.
Mark
 
Thanks to all who have answered. It sounds like lead or other low-temperature recrystallizing metal might come closest to what I need. But, public acceptance of lead in products is low and its weight is high. Both factors are problems.

The fact that some metals actually recrystallize at room temperature and do so rapidly was new information for me and interesting.

Most likely, some other method of securing our items will need to be considered.

Denis
 
Can you use a braided metal? SS braid, or copper braid? Seems like they'd survive more cycles than solid metal.
 
This material seems like a pipe dream. I can't think of anything that you can take beyond its yield point so it holds its shape multiple times without eventual damage. Maybe there's a plastic that could do it.
 
Can you use a braided metal? SS braid, or copper braid? Seems like they'd survive more cycles than solid metal.
That may be worth exploring, cuz you are right that braided wire whether Copper or Aluminium would have some holding power and would tolerate repeated bending better than solid.
This material seems like a pipe dream. I can't think of anything that you can take beyond its yield point so it holds its shape multiple times without eventual damage. Maybe there's a plastic that could do it.
Pipedream? Ya, maybe with that implying impossible to fulfill. And with what I have known til now that is true. The thing I have trouble with is not knowing what I don't know. This group has such a wide and deep range of experience that I figured if there really was a solution, someone here might pop up with something other than the "usual suspects."
Polyethylene or Polypropylene might. You can mold the living hinges in toolboxes. Properly done, they have a near infinite flex life.

No douubt about the durability, but lacks holding power.
Then to get bendy you may have to use a laminated sort of thing I’d guess, thin sheets of strip?
Mark
This is along the lines of braided material. Not a bad thought and likely to have both reasonable holding power and durability.

Denis
 
Comment: I think the several one or two word answers I've gotten are well-intended and I appreciate them. But who knows what they mean? Is this a material the respondent has extensively used in just the sort of application inquired about in the first post or is it a suggestion based on a thought that popped into their head but without any knowledge of pricing, availability, and true suitability to the task?

I am really hoping for experience-based answers that address the whole picture. And I have a feeling that a material truly suitable for my needs may not exist.

Denis
 
gold never work hardens ........pure iron can be bent and straightened many times ,but probably not as much as required.
Actually pure gold does work harden .. if you accidentally make a gold wire seal with a bump or twist in it you have to anneal it to remove the springiness or it won't sit in place before you clamp it. Trivia I know.
Back to the OP, does it need to be 'C' shape, could it be an acute vee like the springs on flintlocks? that way the stress would not be concentrated in the small radius, reason the springs are that way. OOPS! I forgot 'straightened'. I think you are between a rock & a hard place.
And now, RED FACE, you are dead right John, else gold leaf, as you point out, would be nigh impossible. Apologies. I suspect gold work hardens very slightly .. my term 'anneal' was a bit of a stretch, we used to gently waft a fluffy neutral flame over springy seals & you could see them relax onto the asbestos bench top nice & flat. Obviously my memory to back 50 years is a bit suss.
 
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