The report is on the UC type portable automatic welder. The control circuit contains only transformers and selenium rectifiers instead of conventional electronic tubes. Thus the operation is simplified and. chance of trouble much decreased, (furthermore sensitivity of control increased). The quick response characteristics of the control system when the arc voltage is changed suddenly by some causes are studied by oscillograph, and the results show that the welder operates satisfactorily even by this simple control circuit.
X-ray diffraction photograms from various fractures in mild steel arc welds were taken. The author considered about the problems of rupture in weld metals in the light of lattice distortions. Main conclusions in this paper are as follows: 1. Weld metals made under constraints have lattice distortions in some measure, but these are not so large as to cause the Kα doublets to merge to continuous broad lines. 2. The surfaces of shrinkage cracks and the so-called "striated" fractures are not identical, but it is true that shrinkage cracks are apt to occur in the so-called "striated" structures. 3. Blued "striated" fractures, namely the surfaces of shrinkage cracks, have pretty large lattice distortions which cause the K. doublets to merge to continuous broad lines. 4. In the vicinity of shear fractures in tensile test specimens of all weld metais, which showed large elongation values, say 40% or more, there appears a pronounced preferred orientation as well as in forged mild steels. 5. The silvery-like portion in fisheyes is not a surface of shrinkage cracks at lower temperatures, but a brittle fracture by applied loads. 6. An X-ray diffraction photogram is an adequate measure for comparing the brittleness of weld metals. And the fractures in mild steel arc welds are to be classified as in Table 3 in accordance with lattice distortions, namely brittleness.
The experiments were made upon arc and gas welded rails to obtain the relations between their strengths and welding practices. Various types of joints and electrodes were used for welding, and .the fracture strengths were measured by bend tests. As the result, the following conclusions were obtained. 1) The arc and gas welded rail joints showed reliable strengths for practical use under satisfactory welding practices. We could classify the qualities of electrodes used and the degrees of workmanship by the fracture strengths and the appearances of fracture surfaces. 2) The arc welding was preferable to the gas welding as a method of rail connecting. 3) It was very important to select a suitable type of electrode and of superior quality to secure good mechanical strengths especially on arc welding. Austenite-type electrodes were also available as well as mild steel electrodes. 4) It was concluded that the Shintsurumi-type point was the best for both the arc and the gas welding. 6) It was recommended to anneal the joint after welding has been completed.