Dimensional Insatbility SS Vs. 1085

[jackpot]

It is commonly known in the spring industry that when 302SS springs are stress releived after coiling, they increase in diameter (d) and decrease in free length (Lf); conversely, music wire decreases in diameter and increases in free length.
My question is why? I suspect that it has something to do with the packing arrangement (BCC vs. FCC) of the metals but I would only be guessing. Does anybody really know the physics?

Jackpot

 

[NickE]

yes I used to know why this is, but forgot, I will think about it tonite. let me re-hash your question:

302ss (spring temper) gets diameter and looses length when stress relived after forming, 1085 spring temper does exactly the opposite.

hmmmm Have to think this one over.

nick