Since olden times there were many attempts to control remotely d.c. arc welding machines, but many efforts were in vain because of the complexcity of the control mechanisms. This paper describes a simpler control method which uses no relays and no control cables. The welding current is adjusted by a small a.c. motor whose control is carried out by connecting welding cables with a control box containing resistance. The remarkable feature of this method is that the control motor does not rotate reversely. In this paper, the authors state three control circuits and explain the actual circuit of the motor-generator type d.c. arc welding machine.
Authors analysed on the Statistics of the tensile test value(tensile strength, yield point, yield ratio, elongation and reduction of area) of ilmenite type arc welding electrodes (4 and 5 mm diameters) at the Railway Technical Research Institute, JNR., during 1950-1953 in accordance with JIS G3524 (similar to AWS standard). The results are summarized : 1) Distribution types of population of mechanical properties of two diameters were considered as normal. (Table 1, Fig. 2) 2) For the mechanical properties of two diameters, minimum, maximum value, distribution range and estimated values of mean and standard deviation were analysed. (Table 2, Fig. 3) 3) There were very significant mean differences in the values of tensile strength, yield point and reduction of area between two diametens. The values were higher in the 4 mm than in the 5 mm. (Table 3) 4) As to the variance in the tensile strength between the two diameters, the 4 mm was larger than 5 mm. (Table 4) 5) Test electrodes mostly gave standard value of D4301 (JIS G3524). Very few did not conform to standard values of tensile strength yield point, but 10% (4mm), and 5% (5mm) fell short of. elongation standard. (Table 5).
A simple calculation shows that the radiant heat from the molten pool of base metal is too small to explain the self adjusting phenomena of sigma welding, i. e. increase of melting rate of welding rod in shorter arc length. As is well known, the arc voltage increases as the arc current is increased under constant arc length in sigma welding. This positive characteristcs of high current density arc is believed to be mainly due to the increase in anode current density, which in turn results in increase in anode drop. When the welding current is increased, current distribution adjusts iteslf from Fig. 1(a) to Fig. 1(c), resulting in a increase of anode drop. It must be noticed however, that the increase of anode drop would be more pronounced if the current is confined only to the lower plane of the electrode. Fig. 2 shows the current distribution when the arc length is varied with constant current, and we see that the current concentrates to the lower end of electrode when the arc length becomes shorter (Fig. 2a), resulting in a larger anode drop. This increase of anode energy can explain the so-called self regulating action of sigma welding. For the case of D. C. S. P., the phenomena may be explained by assuming the increase of ion current component.
Some deposit metals were made on the mild steel plate and high carbon steel block by A. C arc welding process. Several types of coated electrodes showed in Tablel were used. Manganese and carbon contents of the deposit made by electrode B were not enough as an austenitic manganese steel. But concerning to the hardness distribution, it was more homogeneous than that of deposit made by electrode A. The microstructures of bottom parts of these deposits adjacent to the mother metal were consist of martensite, sorbite or fine pearlite. Cracks oftenly occured in these parts. Sometimes these crack tendensies were seen at the bottom of the single bead deposited by electrode D or E. But multiplying the deposit three layers or more with electrode D or E, dilution effect by mother metal could be avoided, chemical compositions and (micro structures) of deposit became ideal as the anstenitic high manganese steel. The single layered bead made by electrode F or C had an anstenitic structure in spite of the dilution by mother metal and cracks at the bottom of the bead seldom occured. But in multilayered deposit cracks occured along dendritic structure oftenly. For these cracks the precipitation of super saturated carbon and the red shortness of the anstenitic manganese steel were considered to be important causes. The practical manipulation of the electrode became harder with increasing nanganese in electrode core and it's coating. Electrode for single layer use only, therefore, higher manganese content as far as possible to keep the good operating quality is desirable. Electrode such as D and E were suitable to the multi layers uses. In addition, allowable lover welding current and shorter arc length with constant travelling speed of moderate value were desired in this surfacing.
In order to investigate the effect of prestrain, especially large amount of prestrain on the creep phenomena the authors performed the torsional creep test, in the direction of working, of the small round solid bar of mild steel previously twisted at room temperature. 1. The transition phenomenon in the creep rate (measured after one hour) vs. prestrain relation was observed, and the creep rate of material above the transition prestrain range is about 2 times larger than below the range (see Figs. 4-6). 2. The ratio of two creep rates above and below the transition range is approximately constant independent of stress and temperature. And on these creep rates the general equation r= KPn, P=τ⋅e-Q/RT where K and n are the constants, γ is the creep rate, τ is the shear stress, T is the absolute temperature, Q is the activation energy and R is the gas constant, is satisfied in this experiment. 3. It was found that both the decreasing point of the strain hardening rate in a torsional test and the ultimate point in a tensile test correspond to the begining point of the transition.
In the previous report, we tried the tensile tests of the eleven kinds of killed steel plates in each of three directions, i. e. rolling-transverse-and thickness-direction and confirmed that tensile properties in the thickness direction are inferior to other two directions, especially in ductility. In this paper, we studied the directionality of mechanical properties of mild steel and high tension steels. We also studied that of their heat-affected zones and deposited metals by submerged arc welding. From these sxperiments, we knew that; (1) Structural steels, containing high tension-steels, with are rolled have little ductility in the thickness-direction and near that direction as shown in Figs. 4(a), 7(a), 7(b) and 8. (2) Deposited metals by submerged arc welding have no mechanical directionality in tensile and bending propesties as shown in Figs. 3(a), 3(b), and 14. (3) Heat-affected zones have the same mechanical directionality as the parent material.
The purpose of the present paper was to. investigate the cause of very poor fillet weldability of a killed steel plate which showed at a certain shipyard pull-out type fracture through heat affected zone of fillet welds. Fillet weld Charpy impact test, fillet weld fatigue test and some microscopic inspection were conducted, and the following conclusions were obtained: 1) The fillet weld Charpy test which has been introduced in the present investigation seems to be very effective to evaluate quantitatively the fillet weldability of the test steel. 2) The result of fillet weld Charpy test -indicated a sudden decrease of absorbed energy at a critical testing temperature, at which the mode of fracture changed from ductile "through-deposit" to brittle " pull-out ". 3) Welding with low hydrogen electrodes, preheat prior to welding, or normalizing of the steel before welding were not so effective to improve the poor properties in fillet welds of the test steel. 4) As far as butt weld of the plate was concerned there was no sign of defective properties in weldability. 5) The fillet weld fatigue strength of the steel was equivalent to that of one of the other steels which showed no defective properties in fillet weld Charpy test, and there occured no pull-out type fracture in the steel throughout the fatigue test. 6) The poor properties in fillet welds of the 'plate were caused by microscopic inclusions which weakened the strength of plate along the ditection of plate thickness.