Stainless steel fitting - embrittlement
Stainless steel fitting - embrittlement
(OP)
Folks,
Have a stainless steel fitting, small valve welded to a pipe section, maybe about 3/4" in diameter.
The operating conditions it sees internally are 260C, 600 kPa.
Was told by operating personnel that the line suffered from an impact, which caused failure.
Material analysis has shown the pipe to be 321, and 316 on the valve side and weld.
Given that the failure has minimal deformation, despite the materials being typically ductile I suspected fatigue (although can't find evidence of this on the fracture surface) or embrittlement (sigma phase or otherwise). Although the fitting doesn't operate in the range which would promote embrittlement, perhaps uncontrolled welding may have contributed?
Was wondering if anyone had thoughts on what the mechanism could be - have attached a word doc with some images.
Thanks
Have a stainless steel fitting, small valve welded to a pipe section, maybe about 3/4" in diameter.
The operating conditions it sees internally are 260C, 600 kPa.
Was told by operating personnel that the line suffered from an impact, which caused failure.
Material analysis has shown the pipe to be 321, and 316 on the valve side and weld.
Given that the failure has minimal deformation, despite the materials being typically ductile I suspected fatigue (although can't find evidence of this on the fracture surface) or embrittlement (sigma phase or otherwise). Although the fitting doesn't operate in the range which would promote embrittlement, perhaps uncontrolled welding may have contributed?
Was wondering if anyone had thoughts on what the mechanism could be - have attached a word doc with some images.
Thanks





RE: Stainless steel fitting - embrittlement
At this operating temperature, and how the line is configured I would believe more in low cycle fatigue crack propagation along the toe of the weld just based on the appearance of the fracture surface.
RE: Stainless steel fitting - embrittlement
What filler was used for the weld?
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Plymouth Tube
RE: Stainless steel fitting - embrittlement
RE: Stainless steel fitting - embrittlement
http://nz.linkedin.com/pub/jonathan-smith/39/25/58...