本報では, 溶融亜鉛めっき槽の建造期間短縮と建造コストの低減を目的として, 実績のある被覆法に代わる溶接方法および溶接材料について, 溶融亜鉛による腐食特性の観点から検討した。その結果, 概略以下の結論が得られた。(1)溶融亜鉛による腐食は, 材料のSi含有量に依存し, Si含有量が0.20∼0.47%以上になると腐食は急激に増大する。また, 長時間腐食は, 放物線則に従う。(2)Si含有量の少ない溶接材料を用いたガスシールド法, およびサブマージ法は, 被覆法に代わる溶融亜鉛めっき槽建造時の溶接方法および溶接材料として, 適用可能であると考えられる。

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The authors studied on the various welding characteristics and droplet transferring phenomena of the newly developed flux-cored covered electrode, whose core wire contained a flux of 4 weight percent chiefly composed of carbonates. The results obtained are as follows:
1. The bare flux-cored wire gives greater specific melting rate as compared with ordinary solid wire, and this merit is retained when it is covered with outer flux.
2. The new electrode gives, independently of the coating type, a greater melting rate and a smaller transferring droplet.
3. The feature of the new electrodes was proved to originate from the inner cored flux, because it is not seen in the ordinary electrode whose outer flux is the same as the sum of the outer and inner flux of the new electrode in its component and total quantity.
4. The new electrode gives more stable and less divergent arc, less spatter and accordingly fine and beautiful bead appearence.
5. The new method of high-speed cine-photography clarified the phenomena inside the electrode sheath. It is considered that finer droplet from the new electrode depends not only upon the mechanical action of the evolving gas from inner flux, but also upon its characteristic arc which separates the droplet sticking to the core wire tip in an earlier stage than in the ordinary electrode.

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The electrical and thermal characteristics of tungsten arc under axial gas flow in argon atmosphere of 18 to 760 mmHg are examined and various penetration shapes formed in the specimens of copper, aluminum, mild steel and stainless steel at the above mentioned ambient pressures are discussed in relation to the arc characteristics.
The facts elucidated are as follows.
1) At reduced gas pressure, elliptical "Cathode Zone", which is highly ionized and has a higher energy density compared to the arc column, is deformed to the conical shape by the axial gas stream. Arc voltage is considerably high in this case.
2) The velocity of axial gas stream increases with decreasing gas pressure and with increasing arc current. In our equipment, it becomes larger than the sound velocity under the gas pressure lower than 100 mmHg.
3) Under axial gas flow, two types of arc exist, namely "H Type" and "L Type". "H Type arc" has a higher arc voltage and in this case arc is kept at the tip part of the cathode electrode. On the other hand, "L Type arc" has a lower arc voltage and the arc covers much area of the cathode electrode.
4) At reduced gas pressure, potential gradient of arc column in "H Type arc" is nearly equal to that in "L Type arc" and is larger than that in the arc in statistic atmosphere. The sum of anode drop and cathode drop, V_A+V_K, in "H Type arc" is higher than that in "L Type arc". The difference of V_A+V_K between two types is presumed to depend on the surface condition of the cathode electrode.
5) At reduced gas.pressure molten metal is rapidly removed by the strong gas stream. As a result solid groove is formed in the metal specimen. It must be mentioned that when the cathode zone touches to the specimen, the contact zone at the specimen melts very rapidly. In this case deeply arc-gouged or sharply arc-cut groove is formed. The width of the groove corresponds to the contact diameter of the cathode is zone on the specimen.

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The feasibility of gravity arc welding (DCSP) and welding phenomena under water pressures from 0.03 to 6 Kg/cm² (guage pressure) are investigated. The 4 mm diameter coated electrodes of five types and the SM41 steel base metals of 6 and 9 mm thickness are used.
Main experimental results are summerized as follows:
(1) Welding arc can be generated easily and kept in stable under water pressures from 0.03 to 6 Kg/cm2, if only proper welding conditions are selected. Especially the high titanium oxide type electrode waterproofed by laquar has relatively good weldability.
(2) The porosity in weld metal increase with an increasing water pressure.
(3) The butt welded joints obtained under 0.03, 3 and 6 Kg/cm² pressures have sufficient tensile strength in as-welded condition. However, the tensile strength of weld metal decreases with increase of water pressure.
(4) Carbon content of weld metal is raised to some extent with increase of water pressure and manganese and silicon contents are reduced. And hardness distribution in weld metal lowers as water pressure increases.
(5) The thermal pinch effect on arc column is enhanced by increase of water pressure and constriction of arc column becomes stronger.
(6) The anode spot on base metal and cathode spot at tip of core wire fluctuate more violently as water pressure increases.
(7) Water pressure decreases melting rate of electrode.

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In order to obtain the melting surface of slagcovered welding electrode, strong impact was horizontally exerted upon the welding rod in the course of welding. The molten droplet hanging at the tip of electrode was thrown away, and the resulting convex or concave melting surface during welding was observed and measured. In addition to this, specific melting rate (S.M.R.), and mean diameter of droplet (d50), as defined in the previous paper, were measured with five types of electrode at various welding currents and polarities. The results obtained were as follows.
(1) The melting surface of each electrode changes from convex to concave as welding current increases, and the more concave it becomes, the higher is the specific melting rate of the electrode, excluding D4316 type electrode. The changes in melting. surface with current are remarkable in case of D4316, being the highest in S.M.R., and in case of D4313 being, the lowest.
(2) The specific melting rate is not affected by the changes in welding current, mean diameter of droplet, or electrode tip pattern.
(3) Difference in specific melting rate, d 50 or electrode tip pattern, with the polarity of welding current, is rather small compared with that which. occurs with the flux type of electrode, and there is no definite rule on, the effect.
(4) Small indentations always . were observed on the melting surface except pt in the case of very small, current, which might prove direct action of the arc accompanying the indirect action on the bare surface of melting during welding
(5) A new mechanism for detachment of droplet from the tip of welding electrode is proposed, . which is based on the rotation of the dorplet around the melting surface of electorode, motivated by the interaction between surface tension of droplet and repulsive force of the arc.

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The purpose of this research is to investigate the chemical reactions in the weld metal with the CO2-O2 arc welding. Many kinds of weld metal and slag by the CO₂-O₂ arc welding were analysed chemically, changing the rate of oxygen mixed in supplied gas.
In this first report the author describes the method of the experiment and the results showing relations between the rate of oxygen mixed in supplied gas and chemical compositions of weld steel and slag. And he shows that, when welded on plate, an decrease rate of carbon of weld metal is closely connected with a porosity of weld metal.
He will discuss the oxidizing reactions of carbon, silicon and manganse in the second report.

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