Microstructure Observation of High-Current Buried-Arc Welded Joint

Abstract

To address the recent need for improved efficiency in thick plate welding, a high-current buried-arc welding system has been developed. In a high-current buried-arc welding process, it is necessary to adequately evaluate the thermal effect of high heat input on the welded joint. The mechanical properties have been verified1), and in the present study, we focused on observing microstructures. In some regions of the weld metal in the joint welded through high-current buried-arc welding, a characteristic metallographic structure was observed in which the macrostructure appeared extremely coarse. However, this coarse macrostructure was assumed to be a trace of the prior γ grain; the actual microstructure mainly consisted of fine intragranular idiomorphic ferrite and acicular ferrite. These two types of ferrite are known to precipitate at different temperature ranges; thus, their mixed structure is extremely characteristic and is formed because of high heat input.