This paper contains a dynamic study and a static one. The principle of the dynamic study is that the damping of ultrasonic wave depends upon the conditon of the path. That is, if there is a high temperature part on the path, and if there is an air gap on it, the ultrasonic wave would damp to considerable degree. But if there are no such parts, the ultrasonic wave would not damp so severely. By this study, the arthor could find several facts of spot welding phenomina. For example, the temperature rise of the contact surface of the two sheets is very rapid, and the contraction of 24S is so rapid that if the pressure of the electrode is low, the air gap would be resulted between the electrode tip surface and the sheet surface of the welded spot, causing the cracks in the nugget.
Basic experiments are carried out on the arc striking, arc reignition and flux melting phenomena of the low-hydrogen type electrodes. It has been confirmed that two defects of this kind electrodes, i. e., difficulty in arc striking end generation of blow holes at the start of weld, are eliminated by "hot-start, " an extra boost of welding current at the arc starting. A hot-start circuit without relays is achieved by using saturable reactors. Some experiments on blow holes are also given.
In our previous paper, it was for the first time clarified the radio noise was considerably generated during mere A.C. arc welding and cutting without high frequency. A further study on such a noise has been carried out at D.C. arc, the results of which are reported here. The summary is as follows. The interfering voltage of the distribution line produced during D.C. arc welding and cutting is comparatively as large as in the case of A.C. arc, but the interfering voltage in D.C. arc is reduced to the great extent by the use of a group of condensers, the fact being different from the case of A.C. arc. The interfering radiation during D.C. arc welding and cutting is comparatively small as same as the case of A.C. arc.
Various kinds of steel filler wire which contain silicon and manganese, were manufactured for trial. The carbon dioxide-Sekiguchi's filler wire-arc welding process, the C. S. Arc Welding Process for short, was put in operation with them. Then radiographies and bend tests of butts welds and measurements of mechanical properties of all weld steels obtained by this process were carried out. Moreover the shielding effect of carbon dioxide gas was compared with the effects of the atmospher (air), an argonn gas containing one per cent of oxygen and a mixed gas of carbon dioxide and argon. Authors confirmed that when the Sekiguchi's filler wires, having suitable contents of silicon and manganesee, were used and the arc and its neighbourhood were shielded with carbon dioxide gas, excellent welds were obtained, but such excellent result was not obtained with shielding by carbon dioxide gas and use of the conventional steel filler wires or without shielding by carbon dioxide gas in the atmospher and with the Sekiguchi's filler wires. And authors concluded from experimental results that the C. S. Arc Welding Process, which expects the two good effects of use of the Sekiguch's filler wire and shielding of carbon dioxide gas, was predominant in comparison with other various arc welding processes. In case of welding low carbon steel by this process. the mechanical properties of all weld metal were as follows. Ultimate tensile strength : 44-48 kg/mm2, Elongation : 30-36%, (Gauge length=4×dia.) Reduction of area: 61-67%, Charpy impact value : 16-20 kgm/cm2. In the end the authors should like to emphasis that a superior quality of weld steel by C. S. Arc Welding Process is secured in virtue of cowork of good effects of Sekiguchi's filler wire and shielding of carbon dioxide gas or mixed gas containing mainly carbon dioxide gas.
Various tests on the inert-gas metal-arc welding of a corrosion resisting aluminum-magnesiummanganese alloy "ANP", have been performed with ANP-O and ANP-1/4 plates, 1/4 in. in thickness, and various consumable electrode wires, 2S, 52S, A54S, 56S and ANP. The present report Part 4 discusses the effect of porosities in weld metal on the mechanical properties of butt-welded joint, various microstructures of weld metal and heat-affected zone in the base metal, and the effects of filler wires and surface cleaning method on the corrosion resistance of welded joint. The main conclusions are as follows; (1) The yield earl tensile strengths were affected very little by weld porosities, provided porosities were less than the elass No.4 in JIS Z 2341. However, the bend ductility of butt weld was decreased withh porosities greater than the class No.2 or 3. The ANP weld had the best ductility. (2) The corrosion attack in sea water started at the weld toe, and progressed into the interior along the bond. (3) The effects of filler wires and surface precleaning methods weight loss on the corrosion/of butt weld end bead weld were scarcely detected, because the effects of local difference and temper of base plates were more pronounced. The effect of corrosion on the mechanical properties and fatigue strength should be tested furter. (4) From the points of view of mecanical properties, cracking resistance, bend ductility and corrosion resistance, the best filler for ANP plate seems to be the ANP wire, and next A54S, and the third 56S, while 43S wire should be avoided.
An extensive investigation was performed of the effects of nickel and chromium contents on weldability of high tensile manganese-silicon steels, fourteen experimental and four commertial, which contained nickel or chromium less than 1 %. The present paper, the second part, describes the results of the following tests, namely, the weld maximum hardness, Jominy, Kommerell and Kinzel tests. From the results of tests, following conclusions have been obtained ; 1. The maximum hardness of heat-affected zone was increased appreciably by nickel addition, but remarkably by chromium. Nickel and chromium increased the maximum hardness at a rate of approximately 40 and 150 VHN per 1% increase of content, respectively. 2. The hardness at a distance, 5/8 inch from the water quenched end in Jominy test, was closely related to the maximum hardness of heat-affected zone, and increased considarably when chromium content exceeded 0.5%. 3. The maximum bend angle in Kommerell test decreased somewhat with increase of chromium content, but was not almost affected with increase of nickel up to about 1 %. 4. Ductility transition temperatures of base and welded plate specimens in Kinzel test were not markedly changed with increase of nickel, but increased considarably with chromium' addition. It might be considered that ductility transition temperature of Kinzel test specimens depends more on notch toughness of base metal rather than the maximum hardness of heat-affected zone.
The authors have published some papers concerned with anisotropic mechanical properties of structural rolled steels and described that tensile strength exhibits little or no directional properties but elongation and reduction of area decrease markedly as the angle between the test specimen axis and the rolling surface increases and approaches the thickness direction as seen in Fig 1 & 2. In this paper, supposing that bended structures and brittle inclusions are probably important variables which contribute to the poor ductility in the thickness direction, the authors have studied the effects of these variables on the directionality or the ductility in the thickness direction. Based on the experimental results as shown in Figs 5(a)-5(e), 9, 11 and 12, it would be concluded that the directionality. in other woulds, the poor ductility in the thickness direction is more caused by the alignment and shapes of microscopic inclusons, then existence of the banded structure as found in hotrolled steels.