Use of electron microprobe analysis to explain metallurgical phenomena and their effect on properties when welding stainless steel

摘要: A modified electron probe microanalysis (EPMA) instrument containing six wavelength dispersive spectrometers has been used for mapping cross-sections of stainless steel base material and welds. It made it possible to measure the composition in specific small areas illustrate element partitioning; ranging from centerline segregation concealed sub-microstructure. Examples industrial research are given demonstrate versatile application field this established technology. EPMA was study chemical gas tungsten arc welds lean duplex grade UNS S32101 performed with without nitrogen additions argon-based shielding gas. The level not only determined weld metal content, but also affected evaporation other elements metal. Mapping could be reveal detailed information about dendritic substructure fusion line that seen conventional microscopy as microstructure is controlled by nitrogen. With measured local composition, calculate pitting resistance equivalent number, PRE = Cr + 3.3 × Mo + 16 × N (wt%) thereby visualize variation microstructure. Nitrogen strongly concentrated austenite largest impact on PRE. Pitting corrosion testing confirmed ferrite phase most susceptible attack a higher average does significantly increase critical temperature. applied all-weld E347T0 type flux-cored wire bismuth additions. Bismuth can have negative effect ductility after post-weld heat treatment and/or applications at high suggested due grain boundary segregation, debated whether occurs or oxide Bi2O3. Hot tensile content affects 700 °C proved segregates round particles oxide.