engleski

Effects of Type of Backing Gas upon the Corrosion Prpperties of Welds on High Alloyed Steel

Effects of type of backing gas applied for root shielding upon the corrosion properties of root pass have been reported. Welding has been made applying TIG process and no filler material has been added. Argon has been used as the shielding gas.The base material were pipes with 2 mm thick walls, made of austenitic steel grade AISI 304 (equivalent to WNr. 1.4301) and duplex steel grade AISI S 31 803 (equivalent to WNr. 1.4462). In the case of welding of austenitic grade Ar, N2, and N2/ 5%H2 gases were used for root backing, while for the duplex grade, Ar, Ar/ 2%N2, Ar/ 10%N2 and N2 gases were used. Root pass has been tested for resistance to pitting corrosion applying ASTM G 48-92 method for 72 hours at 20°C and 24 hours at 50°C. Corrosion testing has been performed in the surface cleaned condition of samples. Content of ferrite in samples of welds has been determined, and for duplex steel analysis of microstructure has been done. Results of investigation indicate that type of shielding gas for root side has effects upon the resistance to pitting corrosion and percentage of ferrite in the root pass.

duplex steel; austenitic steel; backing gas; root pass; pitting

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