Voltage curent characteristics of three phase rectifier type d.c. welder with non-saturable series reactor (Fig. 1) are calculated for the cases when d.c. reactor Ln is zero and infinity, under the assumption that internal resistance is negligible compared to a.c. inductance L.. The results are shown in Fig. 2 and Fig. 3. It is worth to notice that in case of LD=0, the current wave form of d.c. side is similar to that of no load d.c. voltage for all part of the characteristics though the wave form of a.c. side varies according to the variation of the load resistance. See. Fig. 6. Point Q in Fig. 2 shows the critical point when the over lap angle u becomes less than 60°. Curve, QRS is given by equation (21). The curve in Fig. 3 can be divided into three parts PQ, QR, RS. Each of PQ and RS is linear and QR is circular. Equations for the parts are given in (36), (44), (48). The current wave forms of a.c. side are shown in Fig. 8. The range (a)-(b) of Fig. 8 is well known. In the range (b)-(d), the over lap angle u is constant and the phase angle φ increases from 30° to 60° as load resistance decreases. In the, range (d)-(f) which corresponds to RS of the characteristics shown in Fig 3, the phase angle rp increases from 60° to 90° and the angle β in which the phase current is equal to d.c. current ID which is maintained as constant due to infinite d.c. inductance decreases from 60° to zero as load resistance decreases to ideal short circuit. It is remarkable that for the interval 60-β, the load terminal is short circuited through the rectifiers of the sam polarity. The phase of the initiation of the short circuit is given in equation (38) for B phase. See Fig. 11.
The influence of heat treatment on the creep rupture strength at 550°C of weld joint of 2 1/4 Cr-1 Mo steel, 57 mm thick, were investigated. The used steel was worked with bending, reverse bending and straightening at 950-960°C, which assumed in the manufactured process of a welded seamy tube for heavy thickness steel. After the hot working processes, comparative specimens of base metal, weld metal and weld joint were made in the following three different conditions of heat treatment ; (A) normalizing and tempering (950°C×2.5 h air cooling and 720°C×3.5 h furnace cooling)→submarged arc welding→stress relief (720°C×3.5 h furnace cooling), (B) submarged arc welding→normalizing and tempering (950°C×2.5 h air cooling and 720°C×3.5 h furnace cooling) and (C) submerged arc welding→stress relief (720°C×3.5 h furnace cooling). The results are as follows ; (1) The creep rupture strength of weld metal was inferior to that of base metal for the three different conditions of heat treatment. (2) The creep rupture strength of conventional small size specimens, cut off from the weld joint, were generally superior to that of large size specimens, having the shape as welded but no reinforcement. (3) The heat treatment of normalizing and tempering after welding reduced the creep rupture strength in comparison with that of stress relief after welding. Generally, the creep rupture strength of columnar stracture in weld metal seem to be superior to that of ferrite emerged with the recrystallization by normalizing.
This report deals with some experiments on TIG welding aluminum and its alloys to mild steel coated with various materials including Al, Al-Si, Al-Cu, Al-Be, Sn, Zn, Zn-Al and so on by a simple hot dipping method. The results obtained in this study are summarized as follows. 1) Additions of Si, Be and Cu to Al inhibited the formations of an intermetallic layer between mild steel and Al-base coating, but additions of Mg and Ag did not, and in the cases of Zn and Zn-Al coatings an intermetallic layer was little observed. 2) The tensile strengths of welded joints were equal to or higher than those of aluminum parent alloys in 1100 and 3003 alloys, but lower than in 5052, 5083 and 6061 alloys. 3) As tensile testing of heat-treated welds showed reduction of strength, these joints are not applicable to high temperature services. But there is possibility for use of aluminum alloys are concerned. 4) The definite relation between coating materials and mechanical properties of welded joints was not observed as far as this study was concerned. But further study should be necessary for explaining this relation, using test panels which have high quality coating on the steel. 5) As a whole a 4043 filler rod was satisfactory comparing with a 5356 filler rod. It has been confirmed from this study that aluminum can be joined to mild steel by TIG welding provided mild steel is suitably coated with proper materials. Mechanical properties of welded joints, however, depend mainly on the coating quality and skill for welding technique. Therefore, under the conditions of satisfactory coating quality and skillful welding technique, further study should be necessary especially regarding the relation between mechanical properties of weld and an intermetallic layer with metallurgical consideration of interfacial layers of various coating combinations.
The strength and deformation of end fillet welded joints wre investigated experimentaly and theoretically. Large size end fillet test specimens were used to observe local deformation of fillets closely. Theoretical evaluations on the strength and on the fracture mechanism based on various kinds of yield conditions of the material were presented and compared with test results. It was cleared that the shear stress has the overwhelming effect on the strength of end fillet welded joints and standing on this point of view rather simple and practical calculation formula was proposed.