熔着金属のGas-Inclusionについて(第1報)

Abstract

As regards the essential investigation of gas-inclusion in mild-steel weld deposits, a few informations have been published. However even at present the constituents, combined state and behaviour of gas-inclusion have many ambiguous points yet to be clarified. In order to determine the contents of oxide inclusion in weld metal, the authors after studying the various experimental results, adopted two analytical methods i. e., vacuum fusion method and Fitterer's residual method, which give a comparatively good stability of analytical value.On the other hand the hydrogen in weld metal was analysed by vacuum extraction method at high temperature (800°C), and the nitrogen was analysed by distillation method in addition to vacuum fusion method. In 1st report, they have been able to make clear some relations between these gas-inclusions and mechanical properties of weld metal.(A) In case of absence of hydrogen1) The hyrogen in weld metal was removed by normalizing and annealing at 950°C.2) Owing partly to difference in quantities of the alloy elements in weld metal, it was impossible to clarify the relation between gas-inclusion and the hardness, yield point and tensile strength of all-weld metal.3) The relation between gas-inclusion and percentage of elongation or reduction in area of allweld metal had no appreciable tendency.4) The lowering rate of impact value by "anneal-brittleness" (as named by Mr. Kikuchi) was nearly proportional to the difference between the oxygen obtained by vacuum fusion method and that by Fitterer's residual method. That is, it was found that the more the contents of the oxygen indeterminable by Fitterer's residual method increase, the higher the lowering rate by anneal-brittleness" becomes.(B) In case of presence of hydrogen (as welded)1) When the fractured tensile specimen showed a severe occurrence of "fisheyes" in an arc weld ; percentage of elongation and reduction in area of all-weld metal decreased.2) Contrary to expectation, the relation between the occurring rate of "fisheyes" and contents of hydrogen obtained by vacuum extraction method at high temperature (800°C) had no appreciable tendency.