STRESS RELIEF

[divv]

Hi everybody!!! I have a WPS of a CA6NM welding for using in turbines wich says:

Stress Relief:
Heating rate: 33°C/hr
Temperature range: 590°C
Holding time: 11 hrs
Cooling rate: 28°C/hr

I really dont understand what they did that. I hope you can help me...Thanks!!!

 

[metengr]

The CA6NM is a cast martensitic stainless steel. Typically, the casting is furnished in a heat treated condition prior to use. If any welding is performed on this material, it should be tempered after weld repairs, which the 590 deg C thermal treatment indicates, as such. The deg C/hr are heat up and cool down rates for the tempering heat treatment to minimize thermal stresses.

 

[arunmrao]

Is the turbine a used one ? Normally extensive welding is done to these used turbines to extend their useful life.Besides casting new runer blades and turbines, I have also done some rebuilding. The tempering cycle is carried out after welding as nicely explained by metengr.