Weldieg process applicable to butt weld joint in only one side has been required from the view point of assemblies member and elevation of efficiency as well as reduction of cost and improvement of working efficiency.
This paper reports that C0₂+UM multiple electrodes automatic arc welding applying CO₂ gas arc welding to the leading electrode has a unique effect unexpectable from other processes of one side and one pass automatic arc welding

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Ultrasonic welding is a process for joining plastics by the introduction of high-frequency vibration in the overlapping plastics to be joined.
No filler rods were used. The workpieces were clamped moderately under low static-force, and ultrasonic energy was transmitted to them for a brief interval.
The mechanism by which ultrasonic welds of plastics are produced has not been fully made clear but our resarches will bring it into light step by step.
Certain characteristics of ultrasonic welding of thermoplastics are apparent. For example, weld occurs when the tip oscillates in a parallel plane to the weld interface.
Static clamping force and oscillating force introduced dynamic stresses and plastic flow in the thermoplastics. A moderate temperature rise was noted in the weld zone.
It was known that the process of welding mainly depends on thermal deformation, material properties at room temperature and 1 st transition temperature.
The relations of these factors to microstructural bonding are complex. Spot-type ultrasonic welding machine was used at 2000 W inth a frequency of 22 kilocycles.

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The welded butt joint carsied out by automatic submerged arc welding is mostly fractured under transverse tension load at "soften part" in heat-affected zone, and the joint efficiency frequently falls lower than 100 percent.
This paper is concerned with the investigation on the influence of the heat input energy given by automatic submerged arc welding (UNION MELT) on the strength of joint, the notch toughness of weld metal at center, and the microscopic structures in weld heat-affected zone.
From experimental results it is summarized as follows ; When welding heat input energy exceeds 80×10³ Joules/cm the joint efficiency falls lower than 100 percent. Using the authors' standard welding procedure, there is no problem on the reducing of welded joint efficiency up to 30 mm plate thickness.
On the other hand, the notch toughness of weld metal which is made by various welding conditions is examined by Vee Charpy impact test, and shows the highest level when welding is carried out by the condition of heat input energy (70-80) × 10³ Joules/cm.
From the microscopic examination, "soften part" are regarded as the refined grain structure made by welding heat, and micro-Vicker's hardness in soften part is measured as 90 percent to the mother metal,
Thus the most favorable procedure to selected for submerged welding has been clarified by the above mentioned.
In this shipyard the production of superior 2H-steel pressure vessels, penstocks, and steel constructions has been successfully carried out by thus found proper UNION MELT welding procedure.

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Although welding stresses exist in a welded specimen both during and after welding, only those remaining after the specimen has completely cooled have been much discussed, and many works have been done to measure the distribution of residual stresses in welded joints.
If, however, one wants to make clear weld cracking. behaviours, the most important thing to be done is to inquire minutely into the proceses of generation and growth of welding stresses.
The following are researches on the dynamic measurements of the generation process of stresses in weld which are produced in welding mild steel under the restrained conditions. In measuring the process a trially-made experimental restraint apparatus indicated in Fig. 3 was used.
The conclusions obtained from the above experiments are as follows.
Though the tensile stresses were slightly produced by the contraction of deposit metal at temperatures higher than that of the Ar' transformation, they were soon counteracted by compressive stresses due to the Ar' transformation.
Consequently, restraint stresses are evidently considered to be generated really aftet the Ar' transformation has been finished ; the so called Heyn's "Grenze Temperatur" of plastic and elastic deformation is 500-450°C.
When deposit metal cools down below 500-450°C, restraint stresses are rapidly generated. They keep growing up to the yield point of mild steel while the deposit metal cools down to the room temperature.

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