Stainless Steel A312-TP321H Cracking 2

[azn78409]

Hi friends,
An 8" Stainless Steel A312-TP321H Catalyst Withrawing line is operating at 1000 -1300 F. This line has developed circ. and longitudinal cracks. Please advise the possible causes of material cracking.
Thank you all in advance for your help.

Regards,
azn78409

 

[metengr]

The causes of the circumferential and longitudinal indications you reported for the TP 321H material could be thermal/corrosion fatigue damage, low creep rupture ductility problems with the material, or combination of multiple damage mechanisms, etc. You should have samples removed and have a reliable metallurgical lab investigate the root cause of the problem.

 

[SMF1964]

If cracking is occurring during service, the mechanisms listed by metengr are valid, with a personal preference for thermal/corrosion fatigue. If cracking is occurring during periods of shut-down, consider stress-corrosion cracking as well. Finally, consider processing of the steel (final heat treatment) prior to service as producing a sensitized structure (yes, 321 and 347 can sensitize) that is then less resistant to high temperature intergranular corrosion.