15 February 2016

What is stress relieving process?

Stress Relieving is applied to both ferrous and non-ferrous alloys and is intended to remove internal residual stresses generated by the prior manufacturing process such as machining, cold rolling and welding. The treatment is not intended to produce important modifications in material structures or mechanical characteristics and is therefore usually limited to comparatively small temperatures.

Carbon steels and alloy steels can be given two forms of stress-relieving : 

  • Treatment at typically 150-200°C, after hardening, relieves peak stress without substantially decreasing hardness.
  • Treatment at typically 600-680°C provides almost complete stress relief.

The purpose of treatment is not to make significant changes in material structures or mechanical properties and therefore it is usually limited to relatively low temperatures.

Working principle of stress-relieving

The steel parts relief temperature normally ranges from 550 to 650 ° C. The soaking time is approximately one to two hours. After the soaking time, the components should be gently cooled in the furnace or air. In order to prevent stress owing to the difference in material temperature, slow cooling speed is essential, it is particularly essential when stress relieves large components.

Stress relief is to heat the steel below the critical limit at a temperature to eliminate the stress induced by freezing, hair cutting or cutting off the gas.

This process does not change the structure of the material and does not affect its rigidity significantly.

Benefits of stress-relieving  

  • Components with close dimensional tolerances must be stress relieved. 
  • Parts that are going to be further processed must be stress relieved. 
  • By relieving tension, welded structures can be stress-free.
  • The component can be relieved stress to minimise stress after machining and the possibility of dimensional changes.

Applications of stress-relieving 

  • Stress relieving does not change the structure of the material and does not significantly affect its hardness. 
  • Stress relieving should be achieved at temperatures > 600°C before nitrocarburization.
  • Copper and brass components can also be stress relieved. 
  • Heat treatment for a high-temperature solution is usually required for stainless steels.