STUDY OF THE INFLUENCE OF WELDING PARAMETERS ON THE STRESS-CORROSION RESISTANCE OF AISI-304 STEEL

Austenitic stainless steel has been welded to coat pressure vessels in petrochemical plants. The material is highly susceptible to stress co rrosion in chloride environments, which can damage the weld and lead t o the rupture of the component. In this work we did the evaluation of the influence of welding parameters on the stress corrosion resistance of AISI 304 steel exposed to a magnesium chloride solution. AISI 304 sheets were manually welded using three different coated electrodes (A WS E309-16, E308L-16, E316L-16) and two heat inputs (5.0 and 9.0 kJ/cm ). The welded samples were analysed by tensile strength tests, optical microscopy and corrosion tests carried out according to ASTM G36-73 g uidelines. The results showed that the AWS E309-16 electrodes produced the best results due to the microstructure of the resulting weld meta l. The presence of a network of ferrite particles in an austenitic mat rix acts as a barrier to crack propagation, thus enhancing the resista nce to stress corrosion of the material. This effect is associated to the morphology and distribution of the phase rather than its contents. Welding in a direction parallel to the stress axis using a relatively high heat input improved the stress corrosion of the material even fu rther. The HAZ (Heat Affected Zone) of AISI 304 steel was highly susce ptible to stress corrosion in chloride solution. The presence of carbi de precipitates in the austenite grain boundary deteriorated the corro sion resistance of the steel, as they promoted anodic dissolution and the development of stress corrosion cracks.