The applications of welding by this process are too numerous to mention here, but some of the more important ones are in the manufacture of wagon tires, axles, iron wheels, bicycle parts, pedals, brake parts, chain adjusters, tools, shovels, printers rolls, wire and strip hoops, screens, special piping, rail bonding, as shown in Figs. 104 and 105, rings and chains, automobile parts, steering knuckles and rods, step brackets, valve heads and stems, typewriter bars, sheaves and pulleys, umbrella rods, frames. Fig. 106, structural iron work, stovepipe, knives, steel enamelled ware, etc. Practically every kind of metal can be welded and every shape or section that can be put into the machine can be manipulated if the surfaces can be brought together. Special machines for welding the joints in track rails have been devised and Fig. 107 shows the cars and other details of the equipment required.
Fig. 104. Spot Welder for Bonding Rails Courtesy of Electric Railway Improvement Company.
Fig. 105. Bonded Rail Courtesy of Electric Railway Improvement Company.
A large spot welder, the details of which are shown in Fig. 108, is used and is made so that the jaws hang vertically down from a crane, with a transformer suspended between them. Pressure is applied through a hydraulic cylinder and plates are welded to each side of the web of the rail. The top of the rails is ground smooth after welding.
When welding hoops, Fig. 96, the strip is bent around and the ends brought together and clamped in the jaws of a butt welder. Most of the current will cross the joint, because the jaws are set close and the path across the joint offers the least resistance, although a part of the current will go around the hoop. Chains are welded in the same manner, Fig. 109, and the work is successful in spite of the short length of circuit around the link. Automatic machines are sometimes used for chain making, wire fencing, screens, and other articles requiring a repetition of numerous simple joints, Fig. 110. Sheet steel and aluminum automobile bodies, mud guards, bonnets, and other parts are spot welded. Coffeepots, Fig. 1ll, kettles, and similar articles have their spouts and handles spot welded on, and coal pails, wheelbarrow bodies, spiral piping, coal chutes, boxes, cabinets, lockers, steel shelving, and hundreds of other articles offer almost unlimited opportunities for welding by this system. Butt welding is used to almost as great an extent as blacksmith welding and is much cheaper.
Fig. 106. Spot Welder for Pressed Metal Frames Courtesy of Toledo Electric Welder Company.
Iron and Steel Iron and steel are used more than any other metals and are, therefore, the metals most commonly welded by all processes; fortunately they are about the easiest to weld. For butt-welding iron or steel the stock should be clamped in the dies with comparatively little projection and the ends brought together before switching on the current. Considerable pressure is required because it is better to keep the temperature below the melting point. For an upset weld the dies should be about 1 inch apart and for a flash weld they should be about ¼ inch apart for ordinary sections.
Cast iron cannot be welded commercially by this process because of its crystalline structure and the high percentages of carbon and silicon in its composition. The arc-welding process is the one to use for cast iron, as the metal passes readily from the crystalline to the fluid state when sufficiently heated, which is a disadvantage for butt or spot welding.
Fig. 108. Diagram of Lorain Rail Welder.
High carbon steel can be welded by this process but must be annealed afterwards to relieve the stresses set up by the localized heating. A good joint can always be made with steel of .25 per cent carbon or less, frequently with steel containing up to .75 per cent carbon, but seldom with that containing more than .75 per cent. It requires an experienced operator to get good results with high carbon steel because it is so easily injured. High and low carbon steels can be welded together successfully by good operators, if the low carbon stock is allowed to project further through its die than the high carbon steel.
Nickel steel may be welded readily and the strength is high.
Fig. 109. Semi-Automatic Chain Welder Courtesy 0f Thomson Electric Welding Company.
The metal is really allowed to fuse, or melt, at the joint and the pressure should be just sufficient to force out the burnt metal. It is because of this that good welds are possible, but the current must be shut off as soon as the ends of the pieces soften, and an automatic switch is provided for this on some machines. The dies should be set apart 3 or 4 times the thickness of the stock and more current should be used than for iron.
Iron and copper can be welded together, if the section of the copper is less than the iron at the point of contact, as the former is a better conductor.
Galvanized iron of No. 22 gage and heavier can be spot-welded but it will burn the zinc off at the welded spot and on both sides of the sheets. For thinner sheets it does not pay to try welding by this method.
Fig. 110. Electric Welder Capable of Welding Sixteen Wires at One Time Courtesy of Toltdo Electric Wilder Company.