Dehydrogeneration heat treatment and ISR

[shahdadf]

dear friends,
what is the difference between Dehydrogeneration heat treatment and intermediate stress relieving?
regards,

 

[stanweld]

Dehydrogenation heat treatments are performed in the temperature range of 500 F to 600 F to permit hydrogen to evolve from the deposited weld metal and base metal HAZ. Intermediate stress relieving operations are generally done at temperatures 100 to 200 F below Code minimum allowable PWHT temperatures.

Do not equate the intermediate heat treatment defined in 131.6.1 of ASME B31.1 as being intermediate stress relief.

 

[shahdadf]

thanks stanweld,
but is there any advantage or disadvantage for using them?
regards,

 

[stanweld]

Intermediate stress relieving treatments are primarily used when welding thick pressure vessel components; generally over 4-inches thick and generally in P-No.4 and P No. 5 materials to assure freedom from delayed hydrogen induced cracking during subsequent welding of other shell courses. The cost of each weld is high and the price of repair even greater.

Dehydrogenation treatments are used when welding hardenable materials to mitigate hydrogen induced cracking, especially useful for welding P91 piping and other Cr-Mo-V martensitic alloy components prior to final PWHT. Dehydrogenation treatments are also used after plating operations on hardened materials to prevent hydrogen cracking after plating.