Microstructure and Toughness in Weld Metal of High Purity Ferritic Stainless Steel(Materials, Metallurgy & Weldability)

概要

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Effect of nitrogen and nickel on toughness in weld metal of high purity ferritic stainless steel (19Cr-2Mo) was investigated by means of fractography. GTA welding was carried out using 19Cr-2Mo and SUS316L filler wire in argon, argon containing 0.1% nitrogen and argon containing 0.1% air. For the weld metal by using 19Cr-2Mo filler metal, the energy transition temperature in Charpy impact test raised 30K over that of the base metal. Nitrogen caused the extremely increase of the transition temperature. For the weld metal by using 19Cr-2Mo filler wire with 4% Ni, the transition temperature was 40K lower than that without Ni in each shielding gas atmosphere. The transition temperature of the weld metal contained 7.36% nickel by using SUS316L filler metal was lower than that of the base metal even though in argon contained nitrogen. The fracture surfaces below the transition temperature in every specimens indicated the brittle fracture with tongue, which occured by the intersection of cleavage fracture and deformation twin. The initiation of the twin caused the brittle fracture, which was inhibited by nickel and accerelated by nitrogen. Consequently, the toughness of the weld metal was improved by the addition above 4% nickel.
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