In this research, a single bead was deposited on each constructional special, steel plate and the hardness distribution on the section perpendicular to the bead line was surveyed. And the following results were obtained. (1) The maximum hardness in the heat-affected zone of base metal, which is adjacent to the weld, becomes higher with increase of thickness of the base metal plate. (2) The position of a curve showing the relation between the maximum hardness in the heat-affected zone and the thickness of the base plats is variable with chemical compositions of the metal. Though equally called constructional special steel, there is often a wide difference in carbon content, and owing to this fact a remarkable difference is often confirmed among their maximum hardnesses of the heat-affected zone. (3) The larger the diameter of electrodes used for welding is, the lower the maximum hardness of the heat-affected zone is. But in regard to alloy steels containing high carbon or special steels having large quenchhardenability, such tendency is hard to be found. And on these facts, the authors tried to make simple considerations.
In the case of alloy steels, the zone adjacent to weld metal is profoundly affected by the heat of arc welding. The hardness of the heat-affected zone is very high, and the so-called hard cracks are apt to occur in this zone. In this research, first, it was revealed that under some definite conditions for welding hard cracks did not occur when austenitic steel electrodes were used, but appeared always in the case of mild steel electrodes. Next, using four types of electrodes, which were made of mild steel (very low carbon) and austenitic steel core rods shielded with a thin or thick coating, single beads were deposited on the surfaces of rectangular specimens of ducol and Mn-Cr-Mo steel. The welding was carried out taking into consideration the characteristics of each electrode. Then the hardness and microstructure of the heat-affected zones were surveyed. Under an approximately identical condition for the uses of thick or thin coated mild steel electrodes and thick or thin coated austenitic steel electrodes, the heat quantities supplied to base metals appear to be arranged from large to small in due order of the above-mentioned. And the maximum hardness of the haet-affected zone of alloy steel having an air hardening property like ducol steel is arranged from low to high in good order of the above description. Order differences among the microstructures were found in accordance with the tendency for the hardness. In the case of alloy steel having a severe air hardening-property like Mn-Cr-Mo steel, the differences among the hardness values and microstructures of the heat-affected zones were not found, but cracks were always induced when mild steel type electrodes were used as previously described. Finally, the grooves of mild steel specimens under restraint (θ-type specimens) were welded using the four types of electrodes, and the amount of welding contraction perpendicular to the weld line was measured. The amount of contraction is arranged from large to small in order of the before mentioned arrangement for four types of electrodes. Judging from these results alone, it is unable to explain the reason why the hard cracks do not occur in the case of austenitic steel type electrodes. The explanation of this reason shall be done in another research conducted by the author.
In order to reduce the defects of the usual electrostatic stored energy type spot welding, we rearranged the welding apparatus so as to be able to control the welding current wave forms, and made experiments on the welding of the light metal alloys. In this paper are reported the actions of this controlling apparatus and the resnlts obtained in the welding experiment.
The effects of external constraints upon thermal stresses in butt welded V joints are discussed in this paper. The stress-strain relation in plastic regions at high temperature is idealised as in Fig. 3 considering work hardening, the strengthening effect of which assumed to be same at any temperature. The stress increments are graphically calculated by each small time intervals and superposed on the previous stress values, then the distributions of strain accordingly determined. Figs. 7-12 and Table 2 are the calculated results.