Effects of Ni and N on Mechanical and Corrosion Properties in High Cr and Mo Duplex Stainless Steel Weldment

概要

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A new duplex stainless steel, 27.5%Cr-7%Ni-3.8%Mo-0.3%N, with superior corrosion resistance in sea water was developped. The effects of nickel and nitrogen contents were studied on the precipitation phenomenon in the heat affected zone (HAZ) of 27.5%Cr-Ni-3.8%Mo-N steels, considering that the increase of chromium and molybdenum contents, which is effective for improving pitting corrosion resistance, promotes many second phase precipitates in the weldment. Adding nickel more than 8% to the duplex steel with 0.15% nitrigen caused sigma phase precipitation in the HAZ, and adding nickel less than 6 % caused a large amount of nitride precipitation in the HAZ, which resulted in embrittlement and pitting corrosion in the HAZ. However, the sigma phase and nitride precipitation in the HAZ were prevented with a 0.3% nitrogen content and a nickel content rangingfrom 6% to 8%. Pipes and tubes were manufactured of newly developed stainless steel using a powder metallurgical technique and their mechanical and corrosion properties in the weldment were evaluated. A sufficiently high impact value at 273K and pitting corrosion resistance were obtained in the weldments of the pipes and tubes.
社団法人溶接学会の論文
1992-04-01