Stress Relief vs. Heat Treat

Welcome to the first installment of common misconceptions about spring products. Through the years I have come across many people that use these terms interchangeably, and that is not good from a technical standpoint. Let me explain.

Stress Relief:

Stress relief is a common practice in the spring industry to relieve the stress from pre-tempered materials. A time and temperature formula for the different types of materials will relieve the internal buildup of bending and forming or coiling of the material. Stress relief is something that is not necessarily called out on drawings, but it is common practice in the industry. If you can imagine a coil spring’s outer diameter stretches, and the inner diameter will compress. Heat equalizes that stress. Also, in coil springs the heat applied will increase or decrease (open or close) the outer diameter. Here is a short list of pre-tempered common spring materials.

Material	OD (open/closes)	Temp (F)	Time
Music Wire	Closes	500° F	30 Min
Oil Tempered	Closes	500° F- 600° F	30 Min
Hard Drawn	Closes	550° F	20 Min
302 Stainless	Opens	600° F- 650° F	30 Min
316 Stainless	Does not move	600° F	1 Hour
17-7 Stainless	Opens a Little	900° F	1 Hour
Chrome Silicon	Closes	800° F	30 Min
Chrome Vanadium	Closes	800° F	30 Min
Beryllium Copper	Closes	600° F	30 Min – 2 Hours
Valve Oil Tempered	Closes	600° F	Min until blue on ends