Investigation into microstructures and properties of AISI 430 ferritic steel butt joints fabricated by GMAW

Abstract

Heat input is extremely important for achieving joints with high mechanical properties in ferritic stainless steels. Thus, one of the objectives of this study is to show the effect of heat input on microstructural evolution and thus on the mechanical behavior. For this aim, 5 mm thick AISI 430 plates were butt welded using two heat input levels. Extensive optical microscopy and SEM investigations, microhardness measurements, mechanical tests (i.e., tensile and bending) were conducted to investigate the microstructures evolving in the weld area and to determine the mechanical properties of the joints produced. Strength overmatching was obtained in the weld region of both joints fabricated with both heat inputs employed. In addition, the HAZ region is much wider in the joint fabricated with higher heat input. Although the higher heat input joint exhibited a wider HAZ region the hardness values were similar in the HAZ regions of both joints. As a result, both joints exhibited similar tensile properties, i.e., a strength performance of about 99%. In contrast, the root bend specimen of the higher heat input joint did crack in the bending test while both surface and root bend specimens of the lower heat input joint did not fail.