サブマージアーク溶接金属の窒素吸収

抄録

To investigate effects of nitrogen contents in wires and plates, carbon contents in wires, flux chemistry and welding condition on nitrogen absorption by weld metal and slag during submerged-arc welding, singlepass beads have been deposited on Si-Mn steels of 20 mm thickness by using the combination of four kinds of agglomerated and fused fluxes, having different basicity, with seven kinds of Si-Mn welding wires, having different carbon and nitrogen contents.
The results showed that only the molten weld pool produced by highly basic fused flux absorbed nitrogen from the arc atmosphere in addition to wire and plate when welding at high speed, whilst at low welding speed no nitrogen absorption occurred from the arc atmosphere independently of flux type or flux basicity and hence nitrogen content in weld metal was almost the same as all amounts of nitrogen which came from wire and plate.
Nine kinds of Si-Mn steels and two kinds of CaO-MgO-Al₂O₃-SiO₂ slags have been melted by a tungsten arc in a copper cruicble within Ar-N₂ atmosphere in order to examine effects of nitrogen contents in arc atmosphere and steels, steel oxygen content, slag basicity and melting time on nitrogen contents in arc-melted metals and slags.
Nitrogen dissolves into molten metal from arc atmosphere and then it is partially transferred into slag according to a dissociation reaction of silica. This nitrogen transfer decreases with increase in slag basicity, ilicon and oxygen contents in metals because of a reduction of silica dissociation. Molten slag without the coexistence of molten metal does not absorb nitrogen from arc atmosphree. Nitrogen dissolution into molten metal is accelerated in oxygen rich metal to some extent when no metal coexists with slag.