replacement springs

[macvol]

Good Morning, first time here.
I am working on a project involving an application of getting something to work at cryogenic temperatures that was designed for use at ambient temps. First experience was very well as this device was cooled to 5K then back to ambient and still worked. The problem was that at about 243 K (-50F) the device did quit working, (but we continued the experiment) on to 5K and back. at approx. the same temp the device recovered and seems to have suffered no ill effects. I am looking at the springs used in applying tension as a possible culprit in the cooling cycle. Suspect them to be steel (music wire?) and not being familiar with the material properties am wondering if/when they might lose their compression capabilities and if their are suitable material springs available on the market anywhere. I have found some becu springs but don't know their properties, any suggestions here? the physical size of the springs is: 0.091" O.D. ; 0.300 length ; 10 active coils; 0.014" dia. wire ; the springs are just one of only two parts active in this device in that movement/compression is needed for operation and they are the more easily replaced. Randy

 

[iainuts]

Hi Macvol,
Music wire at that temperature is definately a no-no. It might be ok in a static application, but I'd not even use it then as there's so many other materials that will be much more forgiving. Although it should work, you run the risk of the wire breaking as it becomes much more brittle at low temperature. If the spring doesn't break or deform though, it probably wasn't the culprit of why your device may have had an issue at about -50 F.

I'd suggest stainless, especially 301 or 302 spring temper although 17-4 and 17-7 are common materials that will work also. I'd also suggest using a copper alloy such as Berylium copper or phosphor bronze. Either way, you're much better off than the music wire.