Super Heater Tubes SA213 T22 2

[ak1965]

Is it required to carry out solution Annelaing on super heater tubes SA 213 T 22 (2.25% Cr 1% Mo) material with 5 mm tube wall thickness during its manufacturing?

To my knowledge, solution annealing is done on Austenitic steels & not on T22 Alloy material. on Alloy steels, only PWHT may be required that too on thickneess more than 13 mm.

Any comments please?

 

[metengr]

There is no such heat treatment operation required for T22 tube material. The ASME SA 213 material specification is clear - the tubes shall be supplied as either annealed (not solution annealed but slow cooled in a furnace from the austenitizing temperature), or normalized and tempered.

 

[Fizza453]

AK1965

Quote "To my knowledge, solution annealing is done on Austenitic steels & not on T22 Alloy material. on Alloy steels, only PWHT may be required that too on thickneess more than 13 mm."

The above is true for cicumferetial welds only under some further conditions as per Table PW-39.4 of ASME Section I.
For tube to header joint, PWHT is mandatory.


Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN

 

[Duwe6]

PWHT is done at 1200°F and does not reach the Lower Transformation Tmeperature [about 1400°F] Solution Annealing of s/s is 1600°F, and is done to raise the tewmp to above the asutenitizing point [well above the first Critical Temp]. Different animals entirely.

Also, the PWHT of the tube-to-header welds are typically for the header. It will be thick enough that even P-1 mild steel usually requires PWHT.

 

[ak1965]

Thanks All for good replies..!

My real query:

"A super heater made of SA213 T22 tubes, while under manufacturing need to be undergo U-bending of tubes. Does this operation need solution annealing?"

Please note that 50% of this superheater coil is made of T 22 & rest is made of T91 material."

 

[metengr]

ak1965;
Your real question is should T22 and T91 tubes that are subjected to u-bending require a post forming thermal treatment?

Reply; For T91 material, follow Table PG-20 in the 2011 ASME B&PV Code, Section I. The tube material will require post bend thermal treatment.

For T22, post forming thermal treatment is neither required nor prohibited. What does this mean in code jargon? It means if the material has been cold worked and depending on service conditions, you might need to require a subcritical thermal treatment (aka PWHT) to reduce residual stresses. If the U-bend was done hot, no post bend treatment is required for T22.