A study has been carried out to get an idea about the performance of the Tigamajig test which has been developed for the study of hot-cracking.
It has been shown that this technique is an excellent method to evaluate the hot-cracking sensitivity of sheet materials with thickness less than 3 mm.
The results of the Tigamajig tests performed on 16 heats of materials including SUS 310S, Incoloy 800, Hastelloy X and Inconel 600 indicates that the device permits the evaluation of the hot-cracking sensitivity of different types of materials and effect of specific alloying elements on the hot-cracking susceptibility.
Good correlation was found between the hot-cracking tendency indicated by the Tigamajig test and actual weldments such as spot welds and MIG fillet lap welds.
Metallographic examination indicates that the cracking produced by this device are solidification cracking in the fused metal and liquation and ductility-dip cracking in the heat affected zone.

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Experimental studies were carried out on the formation of penetration beads. To investigate the effects of welding conditions on the shape of TIG-penetration beads, mild steel, stainless steel and aluminium alloy were welded. The results obtained are as follows:
(1) The penetration relates with the width bw and cross sectional area Am of the welds.
(2) These experimental results agree with values analysed by two dimensional interfacial tension theory.
(3) Relation between bead width bw and welding heat input is obtained by calculations of two dimensional heat conduction theory (using physical properties in the solid state near to the melting point and heat efficiency η=0.6). Relation between bead area Am and wire feeding is also obtained by calculations from bt (≅Am/bw).

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It was proved in the previous report that the presence of alloy-rich bands in base metal played an important role in the formation of partially-melted regions, such as grain-boundary liquation. In this report, the change in segregation ratio of alloying elements in bands under the rapid non-equilibrium heating rate in weld thermal cycle was analyzed theoretically. According to the analysis, alloying elements to cause partially melting and the process and mechanism of the formation of partially-melted regions in HAZ were discussed and proposed.

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Application of the thermostable moiré grating has been investigated for measuring the strain distribution of the welded joint deformed in high temperature. The thermostable moiré grating, produced by electrochemical technique, could be successfully reproduced to the welded joint in HP (0.5C-25Cr-35Ni) steel and to the dissimilar-metal joint, 1 1/4 Cr- 1/2 Mo steel to HK40 steel. The grating was stable even at a temperature of 900°C in HP steel welded joint and 510°C in dissimilar-metal joint under creep condition. Thermal expansion and the macroscopic creep deformation was measured by moiré method and local creep deformation was by fine grating method. From these strain measurement, the characteristic of the creep deformation and the creep crack initiation was discussed.

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The corrosion behaviour of silver brazed SUS 304 stainless steel in sodium chloride solutions with the additions of cupric chloride has been investigated using electrochemical and metallographic techniques. The interfacial corrosion mechanism was discussed in relation to the polarization behaviour of SUS 304. The cause of the interfacial corrosion of stainless steel was found to be attributable to the removal of corrosion resistant passive oxide films on stainless steel during brazing by brazing flux, because the anodic reaction was enhanced by the flux treatment. The interfacial corrosion could be penetrated along the narrow and less corrosion resistant zone between filler and stainless steel.
Preferentially dissolved zinc and copper from α-Cu phase precipitated as chlorides on the specimen surface. The added copper in corrosive solution enhanced the corrosion rate by accelarating the cathodic reaction of both stainless steel and filler alloy. The precipitation of the metallic copper produced by cathodic reduction was occurred on the cathodic site such as al-Ag phase of filler alloy and stainless steel surface. The pH change during the immersion test was thought to be caused by the precipitation of added copper and the dissolution of iron, zinc and other alloying elements.

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In this report, an investigation was carried out on the effects of molybdenum and silicon contents on the notch toughness and tensile strength of 40% Ni-6% Mn-10% Cr type weld metal of multi-pass TIG welding. Main experimental results are as follows:
(1) Molybdenum was effective to increase the tensile strength and 0.2% proof stress of all deposited metal, but charpy V-notch impact value at -196°C decreased gradually when the molybdenum content in welding wire exceeded about 7 percent.
(2) Silicon was found to play an important role to raise Charpy V-notch impact value at -196°C when the silicon content was decreased from 0.24 percent to 0.01 percent.
(3) It was confirmed that the distribution of carbides in heat affected zone of multi-pass weld metal was influenced by the content of silicon, and the fracture path and the dimple pattern of fracture surface of impact specimen corresponded to the distribution of carbides in weld metal.

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In the previous report, cold-rolled pure aluminium has a larger range of friction welding parameters, which give no defective weld. interface and better reproducibility of sound joints, compared with annealed pure aluminium.
In this report, the effect of local-cold-working of base metal on friction weldability was studied. Local-cold-working was carried out by peening the friction surface or swaging the end of friction side. Al-Al joint and Al-Cu dissimilar metal joint were friction welded.
Experimental results are as follows;
(1) Local-cold-working is effective for friction welding of aluminium. Especially, work hardening to the cylindrical surface layer of 2-3 mm depth by swaging makes nearly as same as satisfactory friction weld as cold-rolled bar.
Peening was not so effective as swaging.
(2) Friction weld between swaged aluminium and annealed copper gives higher fracture stress and better reproducibility of sound joint, compared with between annealed aluminium and copper.

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