The improvements of the welding process and techniques and the various applications which have been done with so fantastic speed in recent years, have had a great effect upon the welding training in the technical high school. The urgent problem, above all, is to train as many pupils as possible to be the middle class welding engineers. But, it seems difficult to have effect to our purpose, because the present welding training is poor in the technical high school. In order to judge the present situation, we made inquiries to the welding training centers and various factories concerned, expecting their advice on the welding education. After studying the data carefully, we came to the following conclusion : 1. To open a lecture on "welding engineering" in the mechanical, metallurgical and ship-building courses in the technical high school. 2. To establish 5-8 welding courses in the technical high schools in our country. The course should have subjects relate to mechanics, metallurgy, electricity and chemistry etc., worthy enough to train the students to be the middle class welding engineers.
A modified FISCO type cracking test was used to study the cracking properties of inert-gas metalarc welds in commercially pure aluminium (2S) and aluminium-magnesium alloys (52S, 54S and 56S). An automatic welding head was employed to make intermittent welds in FISCO type specimens and the cracks were detected by X-ray radiographic and fluorescent penetrant methods. Weld metal cracks were studied by classifying into four types, namely, longitudinal crack at the start of a bead, longitudinal crack in the intermediate portion of a bead, crater crack and longitudinal crack throughout the bead. The results obtained in the experiment were as follows. 1. It is possible to compare weld cracking tendencies of Al and Al-Mg alloys by the modified FISCO type cracking test. Weld cracking tendency was not so serious for a plate thickness of 12 mm, but greatly increased for greater thickness of 20 and 30 mm. 2. Longitudinal cracks at start or in intermediate portion were increased with increase of welding speed, root opening or plate thickness. 3. Crater cracks were made greater with increase of welding current and decreased with welding speed, since the size of crater changed itself with them. 5. Variation in arc voltage scarcely affected the weld metal cracking. 5. Vee-grooved specimens were more crack-sensitive than I-grooved ones. 6. Among several combinations of welding wires and plates, the most crack-sensitive one was 2S wire-51S plate or 52S wire-2S plate. The combination of 52S wire and 52S plate came next. The three combinations, 2S wire-2S plate, 54S wire-52S plate and 56S wire-52S plate, were equally less crack-sensitive than the above three ones. In other words, the weld metals with their magnesium contents between 1 and 2 percentages showed e greatest crack sensitivity, while both the lower and higher magnesium content regions gave far better cracking resistance. 7. For the prevention of weld cracking, welding should be done with lower welding speed and a suitable value of welding current, an adequate choise of welding wire and a suitable welding procedure at the start of bead are also necessary. At the end of a weld the bead should run off the groove onto the plate surface and the crater should be finished with a crater filler method.
Phosphorus has strong tendency to from segregated structure in weld metals and coarsens ferrite grain size by forming the untransformed α phase. Silicon and aluminium were used as deoxidizer in this experiment. In higher silicon and aluminium contents, the transition temperature begins to increase at the lesser contents of phosphorus.
Following the first report, six different heats of stainless steels, wrought round bars and wrought plates of type 347, 304 and 304L alloys, were subjected to RPI hot ductility test, and following results were obtained : (1) Among the all test steels, both heats of type 347 showed the lowest value of hot ductility during the cooling portion, while type 304 medium and type 304L the highest. (2) The hot ductility of type 347 alloys showed a considerable scatter, and the wrought plate gave much better ductility than the wrought round bar, which may be contributed to the difference in heat and forming procedure. On the contrary, the difference and scatter of hot ductility of type 304 or 304L were only appreciable. (3) Microsscopic observation indicated that this phenomenon was closely related with the embrittlement due to grain boundary liquation, and the degree of embrittlement of type 347 was the greatest of all. (4) Microscopic obsrvation also showed that the fractures of all grades tested were of intergranular type except of the wrought round bar of type 304L when heated above 900°C.
In the same way as the previous report, many beads were deposited on plates by CO2-H2 and A-H2 arc welding, varying the volume percentage of mixed hydrogen in supplied gas. Experimental results made clear the following facts : 1. In the case of CO2-H2 arc welding, the weld metal becomes very porous, when the volume percentage of hydrogen in supplied gas is over about 10%. 2. It is deduced from this value that the weld metals obtained by CO2-O2 arc, argon-arc, submerged arc welding or manual arc welding with a low-hydrogen lime type electrode hardly become porous on account of hydrogen only, but the weld metals with a ilmenite, cellulose or high titania type electrode may become porous by hydrogen only under certain unfavorable welding condition. 3. The rust of joint may produce hydrogen porosity of weld metal. 4. In the case of A-H2 arc welding, the weld metal becomes porous at the lower volume percentage of hydrogen than in the case of CO2-H2 arc welding.