In order to prevent electrode sticking, arc-drive circuits of two types are used in case of an a. c. arc welding machine. They act on the principle that the short circuit between the electrode and the work decreases the reactance of welding transformer, resulting in the increase of short circuit current. Considerations on the ideal characteristics of arc welding machines are also given.
There are various defects in the old method using Sato's type dilatometer for obtaining continuous cooling transformation diagrams. Those defects were removed by using the new apparatus explained in this report. The new appratus consist of two parts for recording dilatation and for thermal analysis. As the appratus for recording dilatation, the dilatometer originated by Dr. Adolf Rose was imported from Germany, and reconstructed so as to be suitable for rapid heating and high temperatures up to 1500°C. Furthermore, a recording apparatus was devised by the authors and erected in Japan so as to fit for the author's experiments. In regard to the apparatus for thermal analysis, Dr. Rose's idea was refered, and it was designed by the authors and manufactured in Japan so as to be suitable for rapid heating and high temperatures up to 1500°C.
In this report, the high tensile steel "Wel-ten 55" containing 0.13% C, 0.48% Si and 1.40% Mn was used for the investigation. The authors constructed separately the continuous cooling transformation diagrams of same steel with one method using the Sato's apparatus for quenching test and with other method using the new apparatus. The both continuous cooling transformation diagrams were compared each other, and the critical cooling times Cz', Cf', Cp' and Ce' nearly agreed respectively each other. However there were considerable differences between the both transformation beginning curves to intermediate structure or them to martensite. In the case used Sato's apparatus for quenching test, those curves exist in the lower temperature side. This is considered to be due to the reason that a γ-type bar was used for the temperature indicator in the Sato's apparatus and a certain delay in cooling rate of a specimen, being due to transformation, was neglected. In the new apparatus, the temperature-measurement is correct since the temperature of the specimen is measured directly. The following matter was also confirmed as well as in Report 3: the continuous cooling transformation diagram in case of rapid heating maximum temperature 1300-1400°C is very useful for supposition of the structure and hardness in the heat-affected zone, in the neighbourhbourhood of fusion line, by welding.
In this report, the continuous cooling transformation diagram, in case of rapid heating maximum temperature 1350°C, was constructed with the new apparatus for "Wel-ten 55" containing 0.18% C, 0.47% Si, 1.40% Mn. Next, effects of chemical composition on the continuous cooling transformation diagram were investigated in regarding to three kinds of "Wel-ten 55" treated in the Reports 1-6. Critical cooling time Cf', showing the limit over which primary ferrite appears, is changed remarkably by carbon content. When the carbon content decreases from 0.18% to 0.13% (amount of reduction : 0.05%), Cf' decreases from 8.5 to 3.8 sec. (amount of reduction : 4.7 sec.). The effects of other elements are very small in comparison with that of carbon. The value of critical cooling time Cf' is very important in case of welding the steel showing it, since the structure and properties of the heat-affected zone, in the neighbourhood of fusion line, by welding show a remarkable increase of brittleness with decrease of cooling time when the steel is cooled with various cooling times in the neighbourhood of Cf'. The steel maker should make efforts to product steels whose Cf' are smaller as much as possible and which show the required strength, It is considered to be free from danger that the welding of the steel is carried out with a certain condition by which the cooling of heat-affected zone near the fusion line occurs with a larger cooling time than Cf'.
The main parts of this paper are 1 Effect by dynamic variation of contact resistance 2 Thermal conduction when heat is generated only by specific resistance with direct current 3 Effect by physical constants variation with temperature 4 A method of consideration for Thermal conduction to yz direction of sheet. 5 Numerical calculation of aluminium alloy and mild. steel.
Deposition of lead on steel surface called "Homogen Lining" have been applied widely to chemical equipments. But the coherent mechanism of lead on iron or steel surface is not evidently described yet. In addition basis studies concerning to the Hommogen technique are little obtained. Experiments have been carried out by the authors to dissolve these problems described above. The erosion of iron by molten lead procceds remarkably at the temperature of 750-800°C in the argon atomosphere (Fig.23 and 24) and lead wet the base metal at these temperature (Fig.5B). Polished surface of iron is microscopically disturbed as shown in Photo. 1 and 2 by the deposition of lead on iron surface with a technique similler to the Homogen Lining. It is considered that lead unite to the rough surface of iron mechanically. If steel is used as a mother metal, the pearlite region eroded severely rather than ferrite part as shown in Photo. 3 and 4. Lead cohere to steel through the irregularity caused by this pearlite attacking. When the eutectoid steel is used as a base metal, the joining surface is not rough because the surface is eroded uniformly by the molten lead. Good bonding strength is obtained also in this case though. It is not clear that the cohesion mainly due to mechanical means or to other ways. Studies on the ternary system of Fe-C-Pb are thought to be desirable. On the Hommogen Lining practice, ZnCl2 have to be used as a flux for both lead oxide and iron oxide. The mixture of ZnCl2 and SnCl2 (80 : 20) is more effective though pre-heating temperature of base metal must be maintained 300°C distinctly as shown in Fig. 1. Homogen Lining is perfomed easily according to the increase of carbon content of base steel. When cast iron is used as a base metal, heating must be done from the opposite side after the flux is applied.
There are two types of front fillet test specimen, one is Splice type, the other is Cross type. But there is difference of breaking strength of the two types, inspite of same sized fillet. Test was then made to study the stress distribution of the two types fillets, and to study above mentioned point by it's result. Thickness of specimens was 10mm, size of fillets were 30mm and 50mm, and those were devided into Splice type (FS) and Cross type (FC). Test Results : According to wire strain gauge, (1) Yielding of fillet went on from inside to outside. (2) Breaking strength of FS were higher than FC, but stress concentration of inside of fillet was inverse. We consider, the difference of stress concentation is due to shape of non-welded slit between base metals each other. (3) Average breaking angle of FS fillet was 24°50' and shape was linear, but shape of breaking fillet of FC was very different from FS. (4) Breaking strength of long spliced specimens were higher than short, inspite of same sized fillet and same FS type.
We measured deformations of plates shown in Fig. 2 and 3, specially in detail angular distortions due to moving heat sources (oxyacetylene flames) under various conditions (Table 1). We discuss the characteristic elements of the angular distortions using a model shown in Fig. 5. Next, We treat time variations of the angular distortions (Fig. 6), one of their special features is shown in Table 2.