Authors have comparatively presisely mentioned the after-arc phenomena in its 1st and 2nd reports, namely we have investigated the special behaviors of the after-arcs with A.C. and D.C. arcs, discussed the possibility of the reignition from the view-point of its long duration. In this report we intend to take the after-arc resistance into consideration and verify experimentally our theory. Generally speaking, our expectations seem to be exact, namely when the arc voltage remains to be extremely low after the extinction of arc, the arc reignites if the interrupter will be switched on, and to the contrary, when the arc voltage becomes to be higher than a certain value, the arc never reignite even if the interrupter is switched in. In analysis of the mechanism of the reignition of the arc, we have induced the after-arc resistance and calculated its behaviors of variations with time. According to our results, the critical resistance to make the reignition possible seems to be about 10 kilo-ohm. It is a striking fact that this critical after-arc resistance may be nearly equal to the glow-to-arc transition resistance, and this fact seems to suggest the situation of the after-arc in the process of electrical discharge.
This paper deals with the radio noise in the field of arc welding and cutting. From our results of a series measurements, it was found that considerable noise over than maximum permitted limit is generated during welding and cutting operation by mere A.C. arc discharge. The work performed are summarized briefly as follows : (1) In A.C. arc hand welding, interfering terminal voltage is about 60-110db at primary side of welding machine and field intensity of interfering radiation is about 45-70db. Also moreover noise is generated in unionmelt welding. (2) In arc cutting and oxy-arc cutting, the noise is more larger than that of the case in (1).
In the fundamental equation for the shape of the surface of a drop resting on a horizontal plane, when the drop is so small that the gravitational term can be neglected, its surface forms part of a sphere. In these circumstances, the area of contact between the drop and the plane depends only on the volume of liquid and the contact angle. An equation of balance in the horizontal direction can be written. γSU=γLS+γLV COSθ where γsv : Surface tension solid/vapor γLS : Interfacial tension of liquid/solid γLV : Surface tension of liquid/vapor It is well known that the use of a flux which reduces the γLV, will reduce the contact angle and greater spreading. The term "Wetting" of a solid by a liquid is defined in terms of the contact angle and therefore of the relative adhesions between the liquid for a solid and of the liquid for itself. Experiments were carried out with the object of determing at what temperature, the maxium spreading over a flux-cleaned copper and brass surface. As flux, ammonium-chloride, HNaNH4PO4, NaH2PO4 solution are used beside Zinc-chloride. Organic acids such as stearic acid, palmitic acid and others are also used. Solders used are 5mm dia., 1mm thickness specimen. It is interesting to compare the results obtained in Tin-Lead solder to those obtained in Lead-Cadminum, Cadminum-Zinc, Cadminum-Tin and Zinc-Tin. By the spreading degree of interfacial area, sombinations of fluxes and solders were classified as superior (over 1.0 sq. cm.) excellent (0.8-1.0 sq. cm.), good fair (0.5-0.8sq. cm.) and no-good (below 0.5sq. cm.). The following results may be drawn from the simple experiments described above : (1) The best known flux "Zinc chloride" is effective on copper except No. 5 Zn-Sn solder. (2) No. 2 Pb-Cd solder does not spread on copper but relatively good spread on Brass. (3) NH4Cl flux has little power and low wettability on copper but better results are obtained on brass.
We have been convinced that steel filler wires having proper contents of Mn and Si as deoxidizers give good weld steels free from porosity and with a small quantity of oxide inclusions. The theoretical, experimental and practical foundation of this proposal was already published by a member of authors. In this report we investigated inclusions in weld metals obtained with steel filler wires containing various amounts of Mn and Si by means of microscopic examination and Wohrman test. The results obtained are as follows. i) Porosity in weld metal decreases with increases of Mn and Si contents of the core wire and the thickness of coating of electrode used. ii) The weld metal, obtained by the coated electrode whose core wire has its composition point in field II of Fig. 1, includes less amount of nonmetallic inclusions compared with weld metal by a core wire having its composition point in other fields. iii) It was recognized by Wohrman test that inclusions in weld metals by core wires in field 1 of Fig. 1 were mainly silica and inclusions in weld metals by core wires in field II and III of Fig. 1 were mainly unsaturate silicates. iv) Some eutectic structure was recognized as large inclusions in weld metals obtained by core wires in field III and the ordinary core wire. And these inclusions accompanied with sulphide film.
It has been considered that the welding on Cr-Mo steel is carried out with many difficulty, but with sufficient preparations and proper heat treatment, the welding will be thoughly completed. This report, being founded on various tests of these alloy steel, 4-6%Cr-1/2%Mo and 9%Cr-1%Mo steel, will contribute to the welding a great deal. The results obtained were as follows; i) As Cr-Mo steel has high self-harden, it is required to maintain the preheating temperature between 400°F and 600°F before welding and is permitted to make no alteration of this preheated temperature during welding works. ii) In a case of welding used austenitic stainless steel electrodes it will be better to treat "semisoft annealing" and suitable compatible composition electrode, better to treat "full annealing". iii) In comparing austenitic stainless steel electrode with suitable compatible composition electrode, the former will be inferior to the latter in hardness, mechanical properties and micro-structure test except weldabilities. iv) In a case of the former electrode, the results of heat treatment is followed by the boundary, so called "Territe band".
This experiment was carried out to investigate the influences of pre-stain for the brittle zone of welded part, using both killed and rimmed steel plate. Test plates were pre-strained by tensile plastic deformation ranging from 0 to 10% after full-annealing. Then, single beads were welded. V-notched Charpy impact tests and hardnese measurements were carried out about the welded parts. It was concluded that the phenomena of quench and strain ageing are always the two main causes for the occurence of brittle zone.