Is heat treatment required for the fillet welds between stainless steel nozzles and carbon steel cylinders in pressure vessel equipment?

Thread Content

The equipment is already heat-treated. During lifting and transportation, due to an error in the lifting operation, a stainless steel pipe fitting at the bottom of the equipment collided with another piece of equipment, resulting in the weld between the flange of this stainless steel pipe fitting and the forged pipe being torn apart; the tear extended to the section where the diameter of the forged pipe changed. We plan to repurchase the forged pipes and flanges, but it will be necessary to remove the existing forged pipe sections by explosive cutting and then re-weld the fillet welds. The design specifications require overall heat treatment, yet the standards do not mention that joints formed between austenitic stainless steel materials require heat treatment. Does this type of joint need partial heat treatment? How should the heating temperature and time be determined? Can the reduced-diameter section of the forged pipe be cut off and then surfaced by welding? So what are the differences compared to the original forged pipes? Help.