normalizing or stress relieving

[212197]

for carbon steel dished end having thickness 52 mm i have to decide post forming heat treatment.

code doesnot specify whether post forming heat treatment shall be normalizing or stress relieving.

our general practice is above 16 mm, we do normalizing.

The vessel after dished end welding will undergo stress releving.

if i do normalising on dishend, as per our practice due to thickness more than 16 mm, dishend will undergo 2 times heat treatment.
if i decide stress releving, i need not to have 2 heat treatment on dish. it will be stress relevied after welding with shell i.e. entire veesel will be post weld heat treated.

To reduce cost of heat treatment, can i avoid normalising & do stress releving as anyway code does not talk about normalising.

What will be adverse effect if i do stress releving after welding with shell instead of normalising on 52 mm dish & then stress reelving after welding with shell?

 

[Don56]

What Code are you design/manufacturing to?

 

[david339933]

For Sec. VIII Div. 1
Heat Treatment is per UCS-56, as stated in UCS-79.
PWHT of the entire vessel will satisfy the post forming heat treatment required by UG/UCS-79.

 

[Morcuse]

The post forming heat treatment is a form of annealing, not a normalizing heat treatment (which is done above Ac3).

David339933's suggestion of PWHTing the entire vessel to satisfy UG/UCS-79 is spot on. You can refer to ASME Interpretation Section VIII, Division 1 (1992 Edition, 1993 Addenda); UCS-79(d), under VIII-1-95-50 for reference.

 

[staticmh]

The links below maybe useful to annswer your questions

good luck

https://www.cliftonsteel.com/knowledge-center/anne...

https://www.sciencedirect.com/topics/engineering/p...

 

[staticmh]

Code only discuss about the EFE exceed from 5% then heat treatment shall be performed as per UCS-79(d) & UCS-56 holding time and temperature ranges.

This is an normal practice we you procure the dish end formed from either hot or cold forming, it always normalized preferable regardless of thickness criteria.
Even though the client specification also dictate for it that normalizing is require or not. Normally we have been using the Shell DEP practice for this purpose and which supersede the code heat treatment required with normalizing. Basically the difference between the normalizing & heat treatment & stress reliving is only the temperature ranges. The most stringent one requirement is Normalizing which above critical temperature ranges. For better understanding you can refer to my both two link to understand the normalizing.

 

[BJI]

I have never understood how PWHT is acceptable under ASME. Other codes require normalizing after forming, or final forming at normalizing temperatures, just like the Shell DEP referenced above. PWHT will not do anything to relieve forming effects. Even performed mechanical testing once to see if normalizing could be waived, and not surprisingly the PWHT was of negligible benefit. Would be interesting to understand the code basis for accepting PWHT if anyone knows?