Stress Relieving Annealing

Stress Relieving Annealing: 
  • As the name suggests, this process is employed to relieve internal stresses. No micro-structural changes occurs during the process. 
  • Internal stresses are those stresses which can exist within a body in the presence of external forces. These are also known as residual stresses are locked in stresses.  
  • These cracking also enhance the tendency of steels towards warpage and dimensional instability. 
  • Fatigue strength is reduced considerably when residual tensile stresses are present in steel. 
  • The problems associated with internal stresses are more difficult in brittle materials than in ductile materials. 
  • The process of stress relieving consists of heating materials uniformly to a temperature below the lower critical temperature, holding at this temperature for sufficient time, followed by uniform cooling.   
  • Uniform cooling is of utmost importance as non-uniform cooling will itself result in the development of internal stresses. Thus the very purpose of stress relieving will be lost.  
  • Plain carbon steels and low alloy steels generally temperature is limited to 6000C . Higher temperature is used for high alloy steels. 
  • The extent of the stresses relieved depends upon the temperature employed and holding time.
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