In spite of the fact that the stability of the arc is essential for applying the arc to the welding, there have been comparatively less reported about it, while the efforts to stabilize the arc have been made. It seems to be chiefly because the problem to stabilize the welding arc includes too many factors to consider quantiatively. It is our aim to express quantitatively the stability of the welding arc through the analysis of the of ter-arc-phenomenon. As mentioned later, the conductivity of the arc space was continuously measured after the arc was extinguished through the interrupter which operated in syncronous with the oscillograph. These were performed under the consideration that the duration of the conducticity after the extinction of the arc means the order of the possibility of the reignition of the arc; namely stability. The results are confirmed as follows; a) The conductivity of the after-arc space continues comparatively long time of abut 0.5 seconds. b) The duration of the after-arc phenomenon is severely influenced by the arc length namely the arc voltage. c) The duration of the after-arc phenomenon is not influenced by the arc current, but by the kind of the materials of the electrodes.
In this report, effects of rod-diameter, nozzle-diameter, acetylene-condition and.flame-type on usability of gas welding rod and mechanical properties of gas weld steels were investigated, using the welding rod III containing 1.37 % Mn.and 0.13 % Si and by the same way as the report 1. The results obtained are as follows: 1. In case of thicker base plates, excellent welds were obtained by adopting comparatively large diameters of rod and nozzle. 2. Bend test results of welded joints obtained by the use of genetator acetylene were little different from those by by the use of dissolved acetylene. 3. When an extreme carburizing flame or an oxidizing flame, whose core-length was below about 8 mm in case of the nozzle number "500", was adopted, the bend test result of welded joint was bad.
The authors have been investigated the characteristics of the spot-welds of the titanium produced in Japan, and clarified the influence of welding condition on weld strength, penetration, indentation, weld-diameter, hardness and structure of welds. The authors have obtained the following conclusions. 1. Spot-welds of commercial pure titanium have fairly strength and ductility. 2. It is easily obtainable the T/S ratio of 0.35. 3. Weld strength is increased with increase of welding current and time, but it is rather decreased with too much welding current and time. 4. Weld-characteristics is little affected with tip pressure. 5. Indentation, penetration and weld-diameter are increased with increase of welding current and time, but the influence of welding time on them is less than that of welding current. 6. The specimen cleaned by CCl4 indicates the best result in welds in comparison with other surface treatments. 7. Failure of all specimens occured in the type of bottom and plug failure. 8. Hardness and structure in welds are little affected by the change of welding current and time, and hardness in welds is as same as annealed condition of parent metal. Structure is dendritic or columnar and grain growth takes. place with increase of welding current and time.
In this report the authors have investigated how to apply the flame-straightening to superstructure of the welded ship construction. It has been discovered that the flame-straightening is effective in the case of ship steel plate and its application needs the following conditions; (1) The effective heating time are 15, 20 and 30 sconds respectively in each 6, 8 and 10 mm thickness using No. 750 tip. (2) The pitches between adjacent heating points are 75 mm in straight lines and 50 mm in staggered spots. (3) Both cases of straight lines and staggered spots have equal effectiveness, but the former is rather more effective than the later. (4) Straightening is to be started from periphery to the centre of the deflected panel. (5) Using strongback it could be straightened more effectively. (6) It is recommended to use fresh water instead of sea water to cool the plate after heatiug on the dockyard.
In the 2nd report, authors confirmed that the gas ratio increase according to temperature rise of tip and so it becomes excess oxygen flame. In this report, authors introduced the relative formulas between gas flow and tip temperature, gas ratio etc. to explain the aforesaid phenomena about low pressure type welding torch, and then compared with the test results. The formula (24) comparatively agreed with our test rerults.
In this report, we give the mathematical analysis for the mechanism of Low Temperature Stress Relieving method and confirmed the virtues of this method, using comparatively small pipes. For the former object, we adopted the test pieces shown in Fig. 1. After welding, the stress-strain relations of each member are expressed by eqs. (1) & (2), where H is the inherent strain. When both side members are heated to temperature T, the central member will be deformed plastically as eq. (3), where g is the plastic strain. After cooling, T becomes zero. Then we have the relations expressed by eq. (6). In the residual stress of the central member is equal to the yielding stress of the material and the material can be assumed to be perfect plastic body, we have the relation σc1≅σc2. Then we get g??αT. From this relation stresses of each member after cooling can be expressed by eq. (7). In Fig. 2, we showed experimental and theorititcal results. Fig. 4. shows the heating and cooling apparatus for pipes. Test results are summarized in Figs. 7-11 for seam welded pipes and in Figs. 12-16 for butt welded pipes. From these curves we know Low Temperature Stress Relieving method can be sufficiently applied to welded pipes in place of annealing at the point of stress-relieving. By measuring the residual stresses at the outside and inside of the pipe, we know the occurence of bending monents by these treatment.
In former report, we confirmed the virtues of the Low Temperature Stress Relieving method in small test pipes. In this report we applied this method to large pipes. At the same time, the partial annealing method by induction heating was done. As to the object of annealing method, we can consider the following two objects; stress relieving and softening of the heat affected zone. But in the welding of mild steel plate, it will be unnecessary to consider the softening of the heat affected zone (see Fig. 16), and the stress relieving will be main object of annealing method. In this point, the Low Temperature Stress Relieving method will be applied in place of the annealing method.
Series of double blow impact tests were performed on U-notched Charpy specimens at temperatures, -65°C to 60°C, to divide the total energy absorbed into the energy for crack initiation (Wi) and the one for crack propagation (Wp). The same experimental procedure was adopted as previously mentioned in the 1st report. The Figs. 1-3 show the test results. From those figures, both the Wi and Wp-temperature curves were determined (Figs. 4-6). Compared with the results of V-notched specimen, the Wi-temperature curves became much higer in their maximum values and shifted towards lower temperature side, while the Wp-temperature curves remained practically unaltered. Mcst part of Wc consisted of Wi below the room temperature in U-notch test. The percent shear-temperature curves in Fig. 10 were also proved to possess close correlations with Wp-temperature curves. For three kinds of steels investigated, the order of the locations and the maximum values of Wi and Wp-temperature curves showed the same relations as V-notch inpact test. The good correlations were found between transition temperatures determined by low energy levels for U and V-notch test. Further, the effects of impact velocities on Wt and Wv were discussed, and found to be all the same as in V-notch test.