Comparison between weave bead welding and multi-layer multi-pass welding for thick plate Invar steel

The welding technology of weave bead welding (WBW) and multi-layer multi-pass welding (MLMPW) are considered to offer advantages over fusion welding in terms of thick plate. The present paper employs a 19.05-mm thick Invar steel plate as the research object to compare the quality of welded joints using WBW and MLMPW. A temperature field model of WBW is established using finite element method; transient temperature field and welding thermal cycle curves of WBW are compared with the ones of MLMPW, which indicates that the characteristic of WBW molten pool periodically changes over time and its temperature distribution is uneven. Moreover, the examinations and analyses of macro/microstructures of WBW and MLMPW are conducted. The results indicate that the inter-layer of Invar steel using WBW is fused better than the one using MLMPW. Perfect weld seam with no defects and a grain growth mechanism of epitaxial solidification of WBW are clearly exposed. The width of heat affected zone (HAZ) using WBW is roughly narrower than that of MLMPW. In addition, the tensile test is conducted to demonstrate that the WBW welded joint has the higher quality.