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 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|
Don’t let this chart Stress you out! Let the Apex Spring experts determine the best material for your applications, and we will figure out the best solution for material selection and stress relief.
The next installment will be on Heat Treatment of Annealed materials. Thanks for reading and I look forward to talking to you again.
Tom Little, Sales and Engineering Manager
Apex Spring & Stamping