Category: Casting And Welding

In a resistance butt welding process, the workpieces which are to be joined are placed end to end between two clamps and required pressure is applied (Figure 20.46). The high resistance at the joint generates heat on supplying high current and causes fusion to take place at the interface. The pressure applied ranges from 15…

In percussion welding, the welding heat is obtained by an arc produced by a rapid discharge of stored electrical energy in capacitor. The parts to be joined are placed in position similar to flash welding. The intense heat of arc melts the parts. The heated parts are then pressed together to complete the weld. This…

Flash welding is used to make an end-to-end joint of two thick metal pieces as shown in Figure 20.45. In this method, current is switched on and then the ends to be welded are brought closer slowly to make contact. Thus, heat is localized at the ends and reaches at the welding temperature. The ends, after…

Flash welding is used to make an end-to-end joint of two thick metal pieces as shown in Figure 20.45. In this method, current is switched on and then the ends to be welded are brought closer slowly to make contact. Thus, heat is localized at the ends and reaches at the welding temperature. The ends, after…

Projection welding is a variation of spot welding. Small projections are embossed at the plate where welds are desired as shown in Figure 20.44. The workpieces are then placed between large-area electrodes and current is switched on. High temperatures are generated at the projections. During the process, the projections collapse, owing to heat and pressure, and…

It is simplest form of resistance welding. In this process, a pair of water-cooled copper electrodes is used. Two overlapping metal plates are held between these electrodes’ jaws as shown in Figure 20.42. Figure 20.42 Resistance Spot Welding The pressure is applied to a very small area, which is known as spot. The resistance at the inner…

It is simplest form of resistance welding. In this process, a pair of water-cooled copper electrodes is used. Two overlapping metal plates are held between these electrodes’ jaws as shown in Figure 20.42. Figure 20.42 Resistance Spot Welding The pressure is applied to a very small area, which is known as spot. The resistance at the inner…

In a resistance welding, heat is generated by passing electric current through high resistance. The amount of heat generated depends on the value of current and resistance as shown in the formula.   H = I2 · R · t Joul   where I = Current in ampere, R = Resistance in ohm, and t = Time in second. When the electric current is passed through…

A highly ionized gas is known as plasma. In a plasma arc welding, arc is created between a non-consumable tungsten electrode and workpiece. A water-cooled copper nozzle surrounds tungsten electrode, which is used as cathode as shown in Figure 20.41. A gas (inert gas) like argon is supplied surrounding the tungsten electrode. The gas is forced…

In this welding, arc is created between two non-consumable electrodes (as shown in Figure 20.40) by supplying AC current. When hydrogen gas is passed through the arc, the heat of arc is absorbed by hydrogen molecules and dissociate into hydrogen atoms. When hydrogen atoms reach at cold work surface recombines to form hydrogen molecules with releasing…