I'm currently using 6inch A106 300lb. rated seamless piping in a pressure vessel that operates at about 150 psi and 750degF.  During a mishap, the vessel was heated in excess of 1300 degF for a period of several hours, forming a small bulge in the pipe (nothing drastic).  According to the ASME Boiler and Pressure Vessel code, the temperature limitation of A106 is 1000 degF.  Has heating the pipe to 1300 severely damaged the carbon steel itself?  Should I replace the pipe, or continue to operate at 150psi and 750 degF?   I can't find any information on this issue.