The CTS cracking test of 50kg/mm² high tensile steel KT and 55kg/mm² high tensile steel YC and the special cracking test of 60kg/mm² high tensile steels YF and YG were performed. The results are as follows ;
(1) The cooling of weld thermal cycles in the case of bithermal and trithermal of CTS cracking test, are generally slower than those in the case of bead on a large plate and T-butt weld joint, respectively.
(2) In the case of deposition on a CTS specimen of the steels KT and YC with ilmenite Type electrodes, cracks tend to occur in the heat-affected zone, when the cooling times are shorter than about C_f' critical cooling time.
(3) In the case that low hydrogen type electrodes are used, the cracking tendency is still small, even if the cooling times are shorter than about C_f'.
(4) In the case of the special CTS tests in which the CTS specimens were quenched in water during natural cooling after welding, the cracking tendency was large, when the specimen was quenched in water from the temperature at the neighbourhood of fusion line at the center of bead-length, being higher than about 350°C.
(5) The cracking tendency in the heat-affected zone may be predicted to some degree by the continuous cooling transformation diagram of the steel used, and the C_f' critical cooling time and the temperature-range of martensite transformation are especially concering to the cracking heat-affected zone.

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The overhead welding was experimented as well as the flat position welding. By the high speed motion pictures in this experiment, the following points were studied.
(1) Some peculiar characteristics of overhead welding.
(2) Velocity and acceleration of transfering droplet.
(3) Effects of current value, polarity, gas flow and gravity upon those in (2).

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Cutting test was carried out by using oxygen of various purities, i.e. 99.8 to 85 per cent. From the test results the relationships among oxygen purity, the maximum thickness that can be cut and cutting variables were obtained with a fair degree of accuracy. The main feature of the deleterious effects of lower purity oxygen is that for a cut of given thickness cutting speed must be lowered, and tip size enlarged. Consequently, the lower the purity of oxygen, the lower the cutting efficiency. The purity of commercially pure oxygen is 99.8 per cen. If this purity is raised to absolute 100 per cent, a considerable increase in cutting efficiency may be obtainable.
The water vapor contained in oxygen and the temperature of oxygen seem to affect more or less on the cutting action, but within the ranges normally encoutered their effects are negigible in extent.
In addition to the above test, ignition temperature of steel was surveyed. Judging from the results, it is probable that the ignition temperature is about 970°C in the range of oxygen purity from 100 to 65 per cent. However, if the purity is decreased from the above range, the ignition temperature rises conspicuously.

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Aluminium and titanium are widely used in steel making In present paper attempts have been made to establish the quantitative effects of aluminium and titanium on the notch toughness of the weld metals which were fabricated by the manual arc welding.
At the early stage of deoxidation the maximum energy remains at low value and transition temprature is higher, but more sufficient addition of aluminium and titanium lowers transition temperature and raises maximum energy.
In case of titanium deoxidation as the amount is increased over 0.1% titanium, transition temperature begins to increase.
But in aluminium deoxidation transition temperature continues to decrease up to 0.35% aluminium.

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First of all, authors confirmed that the hydrogen have been absorbed by welded metal of austenitic stainless steel is holding on non-diffusible state as shown in Table 2.
Next, gaseous compositions in welded metal as shown in Table 3 are measured with vaccume fusion analysis. The test results revealed that;
a) Gaseous compositions in normal welded metal produced by inert gas arc welding are nearly equal to each compositions in filler metals as shown in Fig. 1.
b) Normal welded metals produced by manual arc welding with coated electrode have been increased hydrogen and oxygen than filler metal.
c) Principal gaseous composition in slag inclusion is oxygen, and its in blow hole is nitrogen.

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In the present report the V-notch Charpy impact tests of specimens heated to 1350°C and cooled with various rate were performed. The results are as follows;
(1) If a kind of steel is subjected to a thermal cycle of max. heating temperature 1350°C, the transition temperature of the steel tends to become generally higher, and the absorbed energy and the bended angle at 0°C become lower.
(2) When the cooling of a thermal cycle is comparatively slow, that is, in the case of that the intermediate structure and pearlite disperse finely in the ferrite matrix of the specimen, the absorbed energy and the bended angle of the specimen at 0°C are comparatively large.
(3) The absorbed energy and the bended angle at 0°C in the case of the V-notci Charpy impact test are affected by the carbon content of steel, and the carbon content of a steel is desired to be lower for obtaining high values, as well as the case of non-notch bending test.
(4) According to results of the V-notch Charpy impact test carried out to evaluate the brittleness or ductility of specimens submitted to thermal cycles, it is difficult to clarify differences among properties of various steels. Therefore, the non-notch bending test proposed by the authors seems to be more suitable than the V-notch Charpy impact test, for evaluation of weldabilities of steels.

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