Using a synthetic apparatus for weld thermal cycle hot ductility behavior was studied on a 9% nickel steel and four weld metals; 10N (10% Ni), 20N (21% Ni-24% Cr), 40N (39% Ni-16% Cr) and 70N (Incoweld A). In addition, to predict the actual weld cracking sensitivity, a cruciform or T type cracking test was carried out on the same combinations.
Hot cracking susceptibility increased in the following order: 10N, 20N and (40N, 70N). When the reduction in area was chosen as a criterion, a hot ductility test gave a good correlation to the resistance to the hot cracking of the weld metal by the T type test, but in the case of the hot tensile strength, the relation between those two tests was not clear from this study.

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By adding a plasticizer to rigid high polymer, we can improve the softness, elasticity, workability, adhesive property, etc. according to the purpose of use, and thus the plasticizer is applied artificially to produce excellent plastics. Therefore, much effort has been made to investigate the effects of the plasticizer and to clarify its mechanism.
The author carried out experimental research on weldability of plasticized polyvinylchloride in order to further investigate the possibility to apply polyvinlychloride to a welded structure as a strength member, and the author obtained the basic data as stated below.
1) In both cases of plasticized P.V.C and welded specimens, increase of brittleness and decrease of impact strength were recognized around 10-20 p.h.r, but at low temperature the welded specimens had not their impact strength decreased.
2) The proper kind of plasticized P.V.C, selected according to the purpose of use, is effective and also improves tensile strength, absorbed energy, etc. As for the weldment, the one to which 5-10 p.h.r is annexed is good.
3) An abnormality caused by slightly plasticized P.V.C was also found in the welded specimens.
4) Heat degradation was only recognized in plasticized P.V.C.
5) The effect of load velocity on the tensile strength of plasticized P.V.C was clarified.
6) Stress-relaxation phenomenon of plasticized P.V.C and welded specimens becomes more remarkable in proportion to the amount of plasticizer.

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There are two kinds of primer, wash primer for long term exposure and zincrich primer for steel structures including ships and bridges. Protection presents difficulties, for example, rusting in the former; and in the latter when gas cutting and welding operatings are applied, poisonous fume is emitted from the primer. In order to deal with this problem anew primer has been developed which gives a better protec-tion than the wash primer against rusting and to a lesser degree suffers the effects of welding and gas cutting than the zinc-rich primer. However, the effectiveness of the primver must be considered from the following point of view 1) gas cutting 2) shielded arc welding 3) submerged arc welding and 4) stud welding
These operations are performed frequently in shipbuilding as well as in fabricatin of other steel structures.
The purpose of this study has been to ascertain experimentally the effectiveness of the newly developed primer taking into consideration the above four points. Thrungh experimentation the following properties could be immediately ascertained.
1) Less poisonous fume of welding and gas cutting on the primer.
2) Minor effects of gas cutting and welding.
3) Obviously better than wash primer in submerged arc welding and stud weldiing. Effects of the composition in the primver welding and gas cutting were larger in the following order:
Zinc dust< Alumimum powder< Red Iron Oxide= Zinc Chromate

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It is well known that the fatigue strength of a welded joint with reinforcement is considerably decreased below that of base metal or of a smooth surface welded joint without reinforcement.
Some methods are proposed to improve the fatigue strength of a welded joint with reinforcement, that is, local heating and rapid cooling, synthetic resin coating, grinding or machining of reinforcement bead etc.
The authors also carried out some experiments to improve the fatigue strength of a steel welded joint by metallic coating.
Butt-welded joint with reinforcement was coated with various metalls. Zinc, copper and cadmium film were precipitated by electroplating. Zinc film was formed by hot galvanizing, too. In hot galvanizing process, the welded joint was dipped in zinc bath at 470°C for 70 sec and immediately cooled in water bath. Aluminium molten bath dipping and tin film soldering were also used as coating methods. In these cases, specimens were cooled in air.
Fatigue tests of welded joint specimens with various metal coatings were carried out under reversed plane bending load, to be compared with as-welded joint specimens. As a result, the fatigue strength of hot galvanized joint was improved over that of non-treated joint and was higher than that of smooth machined welded joint. Other metallic coatings had no effects.

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