Authors have already published a part of the themes about the after-arc phenomena, the aim of which is to contribute to the improvement of the stability of the arc as mentioned in § 1. In our 1st repor we have mentioned the special behaviors of the after-arc with D.C. arc, and in this report we will clarify the same phenomena with A. C. arc, in which the perfect results in measuring the arc voltage will be explained. Experimentally, much effortsahave been made at the following points; a) To fix the phase of the current at the interruption. b) The phase of the power source be changeable at the reignition. The former has been done by use of the thyratron, to the grid of which the impulse generated at the zero-point of the arc current was applied, and the latter was made possible by combining the other thyratron with the proper relay circuit. In reference to the measurement of the arc voltage, the vacume tube was used in order to catch the small voltage without disturbing the arc space through measurements. The following conclusions are illustrated; a) The after-arc phenomena with A. C. arc have a kind of characteristics of rectification, and on the case of the electrode negative it continues longer than the case of the reverse. b) The interrupter voltage Vi begins to decrease immediately after the arc resistance Ra became to be comparable with the oscillo. resistance Ro.
This report describes the results of a brief experiment as to single bead test welds, laid on eutectoid steel rail, which is considerably higher in its carbon content than normal carbon rail (about 0.6%C). Main investigation is the effect of the variation in welding conditions such as electrode type (ilmenite and low hydrogen), electrode diameter (3.2, 4, 5, 6mm) and initial plate temperature (0, 25, 200, 300°C) on the cracking, micro-structure and hardness in the heat-affected zone.
In the previous report, results of abrasion testing of homogeneous Carbon steel pieces were reported. It is the purpose of this research to study on abrasion resistance of various hardface-welded depositmetals against sand in a rapid Current of water and to analize some of the aspects of abrasion mechanism. Very hard depositmetals, as welded, were chosen for analizing abrasion mechanism. When shooting angle is 30°, the harder the material is, the more abrasion resistant, but when 90°, material of which hardness is Vickers 400-500, is most abrasion resistant. Then, observations of sand scratches on mild steel and quenched steel pieces were made by means of microscope and profilometer.
To investigate the weldabilities of Killed and Rimmed steels, using the electrodes of the types of both Low-Hydrogen and Ilmenite the low temperature-brittle ness tests are carried out by the "Synthetic Impact Test Method. As the effect of the electrodes for the weldabilities it was recognized that Low-hydrogen type is superior than Ilmenite, but, in the temperature range lower than -20°C, there is no differenses in the impact values. As the effects of the steels types, Killed steel is excellent, but no differenses lower than 0°C. So that there exist no differenses in the point of impact values, at the temperatures lower than -20°C., in spite of the types of the electrodes and the kinds of the steels, and these phenomena will, mainly, depend upon the mechanisms of the clack propagations, which initiates in the heat-affected parent plates. Transition zone of the rimmed steel is wider than killed, and the first sign of the brittleness is higher temperature than killed.
To save the weight of structure, it is general tendency to adopt the low high-tensile-strength steel to the large structures instead of heavy section of mild steel plates. But it is quite difficult to weld such low alloy steels without causing cracks, because of their hardenability as compared to mild steels. The authors have studied the weldability of these steels and prepared this report to summarize our present knowledge of the effect of electrode types and preheat temperatures on weldment. As a result, conclusions have been obtained as follows : (1) In Kommerell bead bend test, comparison of transition temperature at 45°bending angle to maximum load (ductility transition temperature) or of bending angle to maximum load at temperature -20°C shows the difference between ductile and brittle behaviour of weldments for high tensile steels, while comparison of transition temperature at 90°maximum bending angle (fracture transition temperature) or of maximum banding angle at tmperature 20°C shows little significant effect of electrode type. (See Fig. 9) (2) Measuring above-mentioned ductility transition temperature, the weldments of low hydrogen type electrods shows sufficient ductility as compared to these of ilmenite or cellulose type electrods, (See Fig. 9) (3) Little difference has been obtained between the toughnesses of both weldments with ilmenite type electrodes when preheated at temperature 50°C, and with low hydrogen type electrodes without preheating. (See Fig. 14) (4) In any cases preheating over 250°C is needless. (See Fig. 13) (5) In general, higher hardness levels in heat affected zone of specimen exhibit lower bending angle to maximum load at temperature -20°C. In this case, hardness over 350 V.H.N. is unfavourable from the standpoint of behaviour of ductility transition in Kommerell test. (See Fig. 17)
Characteristics of angular distortion in T-fillet welded joints are similar to those of bead-on plate as shown in Fig. 1. Relation between angular change in T-fillet joint and welding conditions is shown in Fig. 2. Angular change by the same electrode becomes maximum when the thickness of plate (h) about 8-10mm. (see Fig. 4). Angular change for the multi-pass fillet weld is approximately proportional to numbers of layer or weight of deposited metal per unit weld length (w) (see Fig. 3). Then simple formula for angular change of multi-pass fillet weld is given by eq. (5), where C/w0 is constant depending on the electrode used. Experimental results are shown in Fig. 6. Effect of electrode size in manual weld and comparison of manual and submerged arc weld is shown in Fig. 8. From this we know that when h≤16mm, the larger size of electrode produces the smaller angular change, and when h<8mm, the angular change due to unionmelt weld is larger than manual weld