engleski

Efects of laser and TIG welding of austenitic stainless steel upon corrosion phenomena

Austenitic CrNi steels are most important class of corrosion resistant steels, and welding technology is most widely applied joining process used in fabrication of variety of structures made of such steels. Considering nature of passivity and need to retain corrosion resistance of stainless steel, selection of appropriate welding process and subsequent surface treatment of area adjacent to the welded joint are of utmost importance. Taking into consideration specific and unique requirements during the process of fabrication of structures made of CrNi steels, acceptable corrosion resistance can be maintained, almost at the level equal to the used base material. If this is not a case, substantial degradation of corrosion resistance and occurrence of sudden and serious local damages are possible. Some characteristic examples of corrosion phenomena in the welded area on structures made of CrNi steels developed in real operating conditions are presented, including primarily damages in the form of pitting corrosion, stress corrosion cracking, crevice corrosion and microbiologically influenced corrosion. Also, results of testing to resistance to the pitting corrosion in the weld area of 0, 6 mm thick AISI 304 steel sheet are reported. Samples have been welded applying automated laser and TIG welding processes. Corrosion testing has been made on both sides (face and root) of samples in “ as welded” and chemically treated conditions applying ASTM G48-99a standard. Results of conducted test confirm a significant effects of surface conditions – occurrence of tint zones, particularly those containing interference colors of 1st order - and applied welding process upon corrosion resistance of welded joint. Results suggest better corrosion resistance of joints made using laser welding when compared with those made applying TIG welding.

Laser welding; TIG welding; stainless steel; pitting corrosion

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