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Title: Manganese and nitrogen in stainless steel SMA welds for cryogenic service

Journal Article · · Weld. J. (Miami); (United States)
OSTI ID:6618029

Evaluation of a shielded metal arc (SMA) weld test matrix in which manganese (1.5 to 10 wt-%) and nitrogen (0.04 to 0.26wt-%) were varied independently has clarified the effect of these elements on cryogenic mechanical properties and predicted ferrite number (FN). Several molybdenum and boron additions were also made, but they had no observable effect on strength or Charpy V-notch (CVN) absorbed energy. The matrix was based on a type 308L stainless steel weld metal composition. Desired compositions and constant FN were attained through alloy additions to the electrode coating. For each weld, one all-weld metal 4-K tensile specimen and five 76-K CVN impact specimens were tested. Increasing the nitrogen content from 0.05 to 0.25 wt-% linearly increased the 4-K yield strength from 600 to 1300 MPa (87 to 188.5 ksi) and decreased the 76-K lateral expansion from 0.6 to 0.1 mm (0.24 to 0.04 in.). Nitrogen reduced the 76-K CVN absorbed energy but not linearly. The addition of manganese slightly increased the yield strength and slightly decreased the lateral expansion. The 4-K tensile strength was relatively unaffected by alloy additions; values varied between 1300 and 1500 MPa (188.5 and 217.5 ksi). The DeLong FN predictive equation was improved by substituting the Szumachowski-Kotecki constant manganese term of 0.35 into the DeLong nickel equivalent. Analysis of the remaining FN deviation revealed an interaction between nitrogen and manganese. Addition of manganese-nitrogen interactive terms to the nickel equivalent increased the accuracy of the FN prediction.

Research Organization:
National Bureau of Standards, Fracture and Deformation Div., Boulder, CO
OSTI ID:
6618029
Journal Information:
Weld. J. (Miami); (United States), Vol. 66:3
Country of Publication:
United States
Language:
English

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