HT-50 鋼大入熱潜弧溶接用 Ti-B 系溶接材料の研究

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The development of a new welding flux which has been applied successfully to large heat input one-side sumberged arc welding (>250KJ/cm heat input) to 50Kg/(mm)^2 class steel is described. It has been demonstrated that the Si-Mn weld metal using commercially availabel flux for midl steel is occasionally not sufficient to large heat input welding of 50Kg/(mm)^2 class steel with respect to the notch toughness and ductility, especially when used with matching strength and higher level of hydrogen content. A means of overcoming those problems by the use of Si-Mn-Ti-B weld metal has been described. This method provides uniform structure of ferrite and pearite, because free B suppresses the nucleation of large primary ferrite along γ grain boundaries and Ti acts to suppress the formation of boron nitride. It was found that suitable composition ranges of Ti and B are 0.01 to 0.02% Ti and 0.003 to 0.005% B at about 1.3% Mn. To provide this optimum range of Ti and B to the one-side submerged arc weld metal, a completely new baking type flux has been developed. The flux is CaO-MgO-TiO_2-SiO_2 type containing TiO_2 as one of the main constitutents and a small quantity of B_2O_3. Ti and B are introduced to the weld metal by the reduction of those two oxides during the wleding, respectively. Suitable range of flux constituents are discussed mineralogically so as to provide stable mechanical properties and welding workability for entire plate thickness ranging from 12 to 40mm. The characteristics of welding result with the newly developed TiO_2 type flux are as follows : (i) The flux shows good workability, namely, good bead shape and good slag detouchment. (ii) Weld metal shows higher notch toughness and yield strength at moderate tensile strength. (iii) And tensile strength of weld metal is less depend on the carbon equivalent.
社団法人溶接学会の論文
1978-01-05

HT-50 鋼大入熱潜弧溶接用 Ti-B 系溶接材料の研究

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