| Abstract Scope |
In order to improve shipbuilding efficiency, high heat input welding technology is widely used. However, welded joints under high heat input usually are subjected to unexpected microstructure deterioration, leading to inferior mechanical responses. In the present work, microstructural variation and mechanical properties of EH420 shipbuilding steel welded joint processed by 145 kJ/cm electro-gas welding were systematically studied. The results show that the weld metal structure is dominated by acicular ferrites, which can provide excellent toughness. The coarse grained heat-affected zone is mainly composed of lath bainites, granular bainites and martensite-austenite (M-A) constituents. Compared with CGHAZ, WM has higher toughness (129.3J vs. 37.3J) as it contains a large number of high-angle grain boundaries (frequency 79.2). It is found that effective Ti-Al-Mg-Mn-O complex inclusions promote the formation of acicular ferrites, which, in turn, obstruct the propagation of microcracks. Moreover, coarse austenite grains in CGHAZ and the presence of significant M-A constituents (average width 1.1μm) between bainite laths may likely contribute to toughness. |