Based on the fact that the notch toughness of steel has been improved by accelerated cooling (A.C.) after the finishing rolling, the weldability of notch ductile semi-killed steel A.C.-treated was investigated. From the results of standard V-notched Charpy, Tipper, Van der Veen and Kahn tests, aging test (by standard V-notched Charpy test), under-bead-cracking test by C.T.S. type, I.LW. maximum hardness test and Commerel test, it was recognized that the weldability of A.C. semi-killed steel is superior to th at of ordinarily rolled semi-killed steel.
To speed up the automatic welding, we used the two welders, multiple power connecting process and parallel connecting process. In this welding, the effects of many factors, the distanc of electrode, welding current, speed, voltage, and angle and dimension of groove were investigated. As the result it is found that the multiple power connection process is the most valuable one which obtains the high speed of the welding and it also confirms the mechanical superiority of the weld metal.
We have made many test specimens of stainless steel over cladding by submerged series arc welding, and selected two specimens. One of these has many falts and another one has none. These two specimens are made from low carbon steel 75mm×300mm×500mm and deposited one and two layers with stainless steel deposite. We inspected those specimens by means of ultrasonic detector using the water flow method and recorded the detecting figures of these specimens. Then cut these specimens across the deposited beads and compared detecting figures, and found that this method was useful for this purpose.
Al-steel, which has a high heat-resistance property, is welded by the general coated electrode and Ni-Cr type electrode with manual arc welding method or by the swaged wire electrode from the same component plate with tungsten innert gas arc welding method, submerged welding method and bare electrode D.C manual arc welding method. The results of mechanical test for weldment by each methods show that the elongation at room te-mperature is very low as compared with base metal, and it is not recovery by the post heat treatment at 700-900°C. According to the measureing results of scale rate for the elevated heat in the range 150-950°C during 3 monts, that of the deposit metals welded by the swaged wire electrodes are in the range 4.9-8.2 %, that by the Ni-Cr type electrodes are 9.3-17.6% and that by the general coated electrodes are 27.5-38.7%. To conclude the examination results of appearences of weldment, X-ray photo-graphy, hardness test and microstructures, tungesten innert gas arc welding method used the swaged wire electrode obtains the best weld joints.
At present the most difficult problem in the three phase frequency converter type resistance welding machine is secondary current measurement. In this paper we discussed some questions on next two typical measuring methods, which seem to be most useful up to date, series resistance voltage drop method and toroidal coil method. Results obtained are as follows ; (1) For series resistance use, the height of pulsating component measured is higher than actual current. For toroidal coil use, (2) the influence of coupling position between welder lower arm and coil does not appear. (3) current magnitude is measured smaller than actual current value, and the errer is approximately proportional to welding time.
A method enabling metals to be welded at room temperature, called cold pressure welding has recently been developed. This unique welding process without the use of heat or electricity, requiring only the simplest tools and permitting the use of unshilled operators, is evoked considerable interst thronghout industry. The writers' study herein introduced, aimed at the cold pressure butt-welding for aluminium used for electrical industry. The results of the experiment are summarized as follows : (1) For the pressure welding, a cleaning method of the surface to be joined is most important. According to our experiments, the motor-driven rotary wire scratch-brushing treatment is most suitable for this purpose. (2) The breaking strength of the butt-joint is depend upon the working degree of the specimens prepared for, that is, joint efficiency of cold pressure welding for annealed material is over 100%, but for cold drawn one is not so good. For example, the efficiency for 67% cold drawn specimen is about 97%. (3) The "Figure of Merit" used to classify weldability for aluminium to aluminium is about 30. This values are same order to A. B. Sowter's data obtained from lap welding, reported in the Materials and Methods, Nov., 1948. (4) The distance from sleeve end to the cleaned surface to be joined is affected on the breaking strength of the welded specimen for tension or torsion test. It was found that the longer distance is necessary to be obtained stable and complete welding and the suitable distance is about similer to the diameter of specimen. (5) Distribution of micro-hardness of cold butt welds is measured. In case of cold drawn meterials, the hardness value of the portion separated 2-3 mm from the weld interface is lower than the value of specimen itself. It is thought that the cause of this phenomena is related to the "Bauschinger Effect".
Intergranular cracks of the steel are easy to occure, when the brazing brass alloy is deposited on the steel in which residual tensile stress is present. These cracks are caused by solder brittleness, that is, the brazing alloy intrudes into and weaken grain boundaries of the steel under the condition of the existence of tensile stress at high temperature. According to the high temperature stress rupture test, solder brittleness by brass brazing alloy commences at the lower temperature than melting point of the alloy, and its tendency increases with rising temperature. Near and above the melting point of the alloy, the brazed specimens rupture almost instantly by considerably low stress without showing no sign of creep. Brazing alloy intrusions into grain boundaries do not take place without stress, and increasing stress increases the tendency to solder brittleness. Silver brazing alloy has less tendency to solder brittleness than brass. In order to avoid the cracking by solder brittleness, it is necessary to eliminate residual tensile stress before brazing by stress relief annealing or other methods. Brazing with silver brazing alloy also prevents cracking.