The electric welding process has riven rise to special ways of doing work. and to special manufactures dependent on its conferring the ability to do work which otherwise could not be attempted. Examples of this are easily found. and the welding apparatus in such cases often takes on a special form peculiarly fitting it for the particular work. In the construe tion of metal wheels the process has been applied to unite the two parts of a hub, which, when brought together and welded, serve also to clamp and weld the iron or steel spokes firmly.
Another case of the special character of the work demanding welding machines of a design and construction altogether different from other work, is in the manufacture of pro jectiles and shells for guns. The parts of the projectile, such as the steel point or tip, the softer tubular body, and perforated butt end, are formed separately and accurately (Fig. 10).
They are then placed in the special welder, where they are united very accurately in their axial relation, but little finishing being required to complete the work. The application of the electric welding process to wire jointing hieing one of the earliest and simplest cases, has become very extended, and inillions of joints are annually made in wires of various size and of different metals. The joints arc usually as strong as the annealed metal, or nearly so. When the wires to be united possessed a structure (Inc to working. such us drawing through the draw plate, it is, of course, not to be expected that such structure will be retained at or quite near the joint welded electrically, as the heating anneals the wire and takes away the grain or toughness conferred by the mechan ical kneading of drawing, rolling, or hammering. In such cases it is customary, where it is practicable, to hammer the joint after welding, special devices, delivering numerous quick blows of small hammers, being made for the purpose. Drawing subsequent to welding restores the structure, and the hammering is then not usually required. The applica tion of the process to the iirodttetion of chain effects a saving in weight, inasmuch as mild steel may replace wrought-iron, and, therefore, yield a chain of equal strength of less weight and cost. The uncertainty of steel welding by the ordinary process has been a bar to the use of ordinary forge welding, and electric welding, on the other hand, enables the milder steel to be employed with almost the same facility as wrought iron. The electric process also enables bars or pieces of such
shape of section as could not be worked by the ordinary welding methods, to be dealt with easily, and hence finds a wide field of application special to itself, in addition to its use for the ordinary work of bar welding, as in tires, axles, etc., pipe welding, etc. _Machinery of the same general character as electric welding machines is applicable to use in electric soldering and brazing. In such cases the current is passed through one or both pieces, so as to bring them tip to the temperature at which the solder melts. In the presence of a suitable flux, the operation can generally be performed with great facility and rapidity. A number of such machines have heel) put in operation. They possess the advantage of local izing the heat almost solely in the portions of metal at the joint, as in electric welding. In consequence, the extensive sealing of partly finished surfaces on each side of a brazed joint (such as occurs with the lire or blow-pipe often employed) is prevented, and the heating action is under the most perfect control. The clamps for holding the work may, of course, remain stationary in the case of elect rie soldering or brazing, though they are often made movable and adjustable for the placing of the. pieces in proper relative positions prior to the heating..
The welding machinery is also applied with but slight modifications (generally of a purely mechanical nature) to such operations as electric forging and shaping, including upsetting and riveting. The portions of metal to be heated for such operations are included between the terminals of the heavy secondary, and are quickly brought to the proper working heat by the passage of the heavy current. After this, either by a movement imparted to the pieces clamped and heated, or by separate dies or formers, the desired shape is given to the plastic metal, and the pieces may be heated and pressed a number of times in succession, in ease the nature of the work is such as to require it.