JOURNAL OF THE JAPAN WELDING SOCIETY

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From various literatures, the authors are informed that as long as remarkably much arsenic is not contained in a base steel, resistance-butt-welding, seam-welding and flus-hbutt-welding are possible, but forge-welding is impossible or difficult even if a little amount of senic is contained. Owing, to these literatures, the authors considered that the cause of this impossibility or difficulty is the Formation of Oxide film by heating of the steel containing arsenic. Therefore, in order to ascertain this view, they carried out a simple forge welding and an oxidation test and they concluded as follows ;
a) In case of carbon steels or Cr-Mo steels, there are tendencies that with the increase of arsenic content the oxide film, which is formed by higher temperature heating, increases and the forge-weldability decreases. That is to say, arsenic in steel promotes the formation of oxide film of the steel and this film interrupts forge-welding.
b) It seems to be likely that in case of low carbon steels containing less than 0.38% arsenic, forge-welding is possible if borax is used and in case of Cr-Mo steels containing more than 0.52% arsenic, in the range cf their experiment, forge-welding is difficult and the upper limit of arsenic contents of forge-weldable steel was not clear for lack of.lower arsenic steel specimens.
And on these facts, the authors tried to make simple considerations.
As they described at the 2nd report, with the increase of arsenic in steel, arsenic concentration increases in ferrite grains as matrix and groups of ferrite grains, which have higher arsenic concentration, is formed by segregation. Accordingly, it is supposed that the hardness of ferrite grains having higher arsenic content is higher and their adhesive property at high temperature is lower than that of ferrite grains withont arsenic.
On the ground of the experimental results and the report of Cameron and Waterhouse (it says that if forge-welding is carried cut with special flux, medium carbon steels containing arsenic show good forge-weldability), it is easily understood that the formation of oxide filmm is the important, factor which interrupts the forge-weldability.

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On micro-fissures sometimes found in mild steel arc welds, the authors observed maerescopically the appearance of fractures of the fissures, and carried out chemical analysis, microstructure test, and cementation test, etc. as to welds revealing microfissures.
They concluded from these experiments as follows :
Fracture of the fissure consisted of columnar structure comparatively fine and oriented straightly and almcst perpendicularly to the weld line. The cause of this structure stettis to be super'cooling of molten metal. Micro-fissures were inte rcry stall ine ones which developed along the primary crystal boundary by dint of shrinkage stress at higher temperature above the A₃ transformation point. This intercrystalline fissuring is considered to have befn fostered by particles of SiO₂ which were on the boundary, and it was found that Mn/Si in deposits greatly affected the occurrence of the fissures.

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