Stress Relieving

[paavainathan]

Dear All,
One of My Client Specification refers stress relieving as Holding in 600 + or - 10 Deg C as per thickness requirement (say 1hour per inch thick) and cooling in still air without any controlled cooling.
In my opinion the Stress relieving will heating in a controlled way from 300 Deg C.
Holding in the 600 + or - 10 for the prescribed time
Cooling till 300 Deg C in controlled rate then cooling in still air.
Please clarify is there any practice like what i said above as per my client requirement.

 

[TVP]

Stress relieving is often performed on parts/components by merely placing them into a furnace (continuous or box-type) that is heated to ~ 600 C for 60-120 minutes followed by air cooling. This does not necessarily achieve the maximum amount of stress relief, but it is suitable for many applications. It all depends on how critical your application is with regards to dimensional stability, distortion, etc. Keep in mind the term is stress relief, not stress elimination.

 

[MikeMet]

TVP is right that there is not always controlled heating and cooling rates. ASME does have controlled heating and cooling rates in UCS-56. It all depends on what type of part you have and the criticality of removing stresses.

 

[paavainathan]

I hope ASME defines the rate of heating and cooling based on thickness. we are using some thumb rule as 5500/t(thickness in mm)to calculate rate of heating and cooling.