고강도강 다층 용접금속 재가열부의 미세조직 및 기계적 특성

Abstract

A large fraction of reheated weld metal is formed during multi-pass welding, which significantly affects the reliability and stability of the welded structures. In this study, the effect of reheating on the mechanical properties and microstructure of high-strength steel welds during multi-pass welding was investigated. Two kinds of high-strength steel welds with different hardenabilities, i.e., welds L (low hardenability) and H (high hardenability), were produced by single-pass, bead-in-groove welding, and both welds were thermally cycled to various peak temperatures to simulate the reheated welds using a Gleeble simulator. In as-welded weld L, acicular ferrite developed extensively in the grain interior, while grain boundary ferrite and Widmanstätten ferrite formed along the prior austenite grain boundaries. The microstructure of as-welded weld H consisted mainly of bainite, with some acicular ferrite and coalesced bainite. The microstructural changes due to thermal cycling were observed by scanning electron microscopy and correlated with the mechanical properties.