ホットワイヤを用いたCO_2ガスシールドアーク溶接金属部の微細組織とその機械的性質に及ぼす効果

摘要

New welding method (F-MAG) based on CO_2 gas-shielded arc welding method (MAG) was developed to increase deposition rate of weld metal. In F-MAG, filler wire (hot-wire) heated using direct-current was put into rear part of weld-pool formed with main electrode used in MAG. Multi-layered weld metals were prepared using both F-MAG and MAG. Microstructures of both as-weld and reheated zones in uppermost layer of the multi-layered weld metals were examined and the effects of microstructures on mechanical properties were analyzed. Both the as-weld and reheated zones of weld metal formed with F-MAG consisted of acicular ferrite (AF) and/or equiaxed ferrite and so on. Both strength and elongation in as-weld and reheated zones formed with F-MAG were superior compared with those formed with MAG. It could be suggested that strength increased by refinement of AF due to increase in the concentration of alloy elements being contained in hot-wire. Larger elongation of weld metal in F-MAG compared with that in MAG could be analyzed in terms of the aggregate of AFs with almost parallel slip systems between neighboring AFs, hereafter referred as to ALPS. The number of AFs contained in an ALPS formed in weld metal formed with F-MAG is larger than that with MAG, in spite of the sizes of ALPSs in weld metals formed with MAG and F-MAG being almost same between them. Deformation occurs over alot of AFs in the case of finer AF through the rotation of tensile test piece during deformation.%F-MAG法で得られた溶接金属部の機械的性質はAW部，RH部ともにCO_2溶接法により得られたそれよりも向上した。これはホットワイヤによるMn,Mo,Ti等の合金元素濃度の増加に伴って微細なAFが生成したためである。溶接金属に求められる重要な機械的性質である伸びは，一つのALPSを構成するAFの数が多くなるほど向にすると結論できた。