From various literatures, authors are informed that pretty amount of arsenic in base metal has no seriously detrimental effects on welding, but small amount of arsenic in core steel is warned. Therefore authors intended to investigate influences of arsenic in core steel on cracking tendency and mechanical properties, especially shock value, of weld metal. In this investigation, coated electrode were used. And from the experimental results, they concluded as follows: a) If non arsenical mild steel is welded with low carbon core steel containing various arsenic, there are tendencies that hardness of the weld metal increases, whereas, shock value of the same weld metal decreases with increase of arsenic in core steel. And if fillet weld are made on condition of high restriction, cracks occur in the weld metal obtained with core steel containing 0.86% arsenic. b) If non arsenical Cr-Mo steel is welded with Cr-Mo core steel containing various arsenic content (<about 0.6% arsenic), there are tendencies that hardness of the weld metal decreases, whereas, shock value of the same weld metal increases with increase of arsenic in core steel. And no difference is recognized on weld metal crack. It is supposed that rather cracking tendency of the weld metal decreases with increase of arsenic in core steel. Accordingly, authors consider as follows on welding of mild steel. Deterioration of weld metal properties are so remarkable that when we have to use arsenical core steel in the future, it will be necessary to adopt any suitable methods to avoid such deterioration of properties. At the 2nd report, authors wish to describe on a important device Which is available for prevention such deterioration of properties.
In order to know the distribution of thermal stresses induced in a circular disc of mild steel with its central part welded, and to make clear the cause of appearance of Lüders, lines observed on the polished surface of the disc as reported in the first report, it becomes necessary to develope an analytical study of thermal stresses. As weld was made at the centre of the circular disc and the disc was thin enough, thermal stresses can be assumed to be a function of radius and time only. To know the distributioa of thermal stresses and especially, of residual stresses in the above-mentioned care, it is, at least, indispensable to erect formulae of thermal stresses which take into consideration the plastic deformation occuring by drastic heating in the neighbourhood of the central hot portion. Here, making a rough assumption that in the above-mentioned welded dise the central region lying above a certain limiting temperature behaves as a pqrfectly plastic body, and the outer region of rather lower temperature as a perfectly elastic one, the author has erected formulae of thermal stresses taking into account the plastic deformation. It is, however, to be noticed that the plastic deformation which perhaps occurs by yielding is utterly out of consideration.