Experiments show that bead appearance becomes discontinuous (abnormal) when welding velocity increases over a certain high limit, other variables (welding current, arc voltage, etc.) being kept constant. Hicken and Jackson report that the bead appearance becomes continuous when arc is deflected to welding direction with use of transverse magnetic field. We have been interested in the above-mentioned experimental results. In order to find out their important factors, using transverse or longitudinal magnetic field, we have observed in detail the phenomena which have been brought about when all welds are being deposited on the mild steel with TIG arc. As the result, we have found out the following facts. (A) When magnetic field is not applied, molten metal is pushed down with plasma jet and molten layer in the bottom of pool becomes gradually thin in proportion to the increase of welding velocity. This thin molten layer tends to solidify instantly when the arc foot moves sometimes to another spot according to the arc character. This results in the formation of a "naked solid surface" in the bottom of the pool. This "naked solid surface" disturbs the free flow of the molten metal in the pool and the bead becomes discontinuous. (B) When arc is deflected to welding direction with use of transverse magnetic field, molten metal is pushed forward and the molten pool is always full of molten metal. (See Fig. 6 (a)) (C) When magnetic direction is reversed, molten metal is positively blown away with plasma jet. This causes the formation of a "naked solid surface" in the pool more easily than (B) and consequently the bead becomes discontinuous. (See Fig. 6 (b)) (D) When the longitudinal magnetic field is applied, molten metal rotates in the pool and so be "naked solid surface" is covered with molten metal. In the case of (A), bead appearance begins to become abnormal at the velocity of 200 mm/min. In the case of (B), bead appearance is always continuous for all the velocities in our experimental range. In the case of (C), bead appearance begins to become abnormal at the velocity of 120 mm/min. In the case of (D), bead appearance begins to become abnormal at the velocity of 280 mm/min. After all, it has become obvious that the "naked solid surface" causes the bead to be abnormal.
In the spot welding, the welded part expands and pushes up the electrode tip during welding current flow. If we restrict this expansion, electrode force increases and weld strength drops considerably as the result. We made experiments on mild steel, stainless steel and aluminum alloy to corroborate this phenomenon using a special spot welder with modified air cylinder and restraining the upward-movement of electrode with stopper.
The plasma arc welding has a feature of giving deep penetrated weld bead, as reported on the welding of austenitic stainless steel plate. This feature is somewhat different from the conventional TIG arc welding. In the plasma arc welding of titanium plates (thickness 7-11 mm), sound welds are obtained with a careful shielding of weldments from the open air atmosphere. Metallurgical and mechanical tests are made with almost satisfactory results. From the view point of welding heat source, plasma arc has a property, resembles to linear heat source. Deformation and shrinkage of weldment by the plasma arc welding are thus far smaller than those by ordinary arc welding. These experimental results are described briefly in this article.
The present work describes a study of the action of flux containing Cl-ions and OH- ions on wetting of solder. The corrosion potentials respectively of base metal and solder-copper as base metal and low melting point alloy as solder were used-when dipped in flux solutions of various concentrations, were investigated by an electropotentiometer. To help clarify the meaning of the measured corrosion potential, a reversible potential of anode reaction that would be reasonably considered in those half cells was thermodynamically introduced, after which the resultant corrosion product of the reaction was related in detail with the wetting of solder on the base metal, but the product was not checked here by any other experimental method. Though the reversible potential was so decided, the corrosion behaviour of the half cell was postulated as an oxygen consumption type on the base metal and a hydrogen evolution type on the solder, since the base metal was noble and the solder was base for hydrogen potential, and it also was assumed that the corrosion potential was nearly equal to the anode equilibrium potential in a local cell of metals, because such a phenomenon was genellary recognized, that is, anode pvervoltage was much samller than cathode over-voltage in a gas evolution type corrosion. The spreading tests on the base metals cleaned with 10% HNO3 solution or electropolished were made with the solder (M.P. 47°C) preplaced in baths of the HCI and ZnCl2 aqueous solutions respectively of different concentrations. From the results of these investigations, it was noted that the corrosion product had an important action controlling whether the molten solder wets the base metal or not, for example the wetting was seen in the range of flux concentration which was effectively forming CuCl but did not appear in the range of Cu2O and the wetting limit of the concentration was pH=3.5 in the case of HC1 aqueous solution under the experimental condition studied.