The principle of the process is shown in Fig. 2.13. Here the workpiece temperature at the joint is raised by resistance to the passage of an electric current across the interface of the joint. The parts to be joined (wires or rods usually) are held in clamps, one stationary and the other movable which act […]

Projection welding is a variation of spot welding. Projections are formed on one of the pieces to be joined, usually by pressing the parts between flat copper electrodes. A current pulse makes the weld at the tip of the projection leaving clean surfaces without indentations. Schematic of the set-up is shown in Fig. 2.11. Fig. […]

Electroslag Welding The electroslag welding is used for welding thick plates. The plates have square edge prepara­tion and are set vertically up with about 25 mm gap in between as shown in Fig. 2.9. A starting piece is provided at the bottom. Some flux and welding wire electrodes are fed into the gap between the […]

In atomic hydrogen welding a single phase AC arc is maintained between two tungsten electrodes and hydrogen gas is introduced into the arc. Hydrogen molecules absorb heat from the arc and change into atomic hydrogen. This atomic hydrogen when comes in contact with the plates to be welded recombines into molecular hydrogen, liberating a large […]

This process differs from MIG in that it uses CO2 instead of inert gases (argon or helium) both the normal and fine-wire machines could be used. The differences are: metal transfer mode, power source, cost and field of application. The process is schematically shown in Fig. 2.8. Fig. 2.8 Schematic diagram of MIG/MAG (CO2) welding […]

In MIG welding the arc is maintained between a consumable electrode and the workpiece in inert gas medium. It is used as a heat source which melts the electrode and thus supplies the filler metal to the joint. The principle of operation is shown in Fig. 2.7. The apparatus consists of a coil of consumable […]

• In TIG welding an arc is maintained between a non-consumable tungsten electrode and the work-piece, in inert gas medium, and is used as a heat source. Filler metal is fed from outside. The principle of operation of the process is shown in Fig. 2.6. • Direct current is normally used with electrode negative polarity […]

Submerged arc welding (SAW) is next to SMAW in importance and in use. The working of the process is shown in Fig. 2.5. In this process the arc and the weld pool are shielded from atmos­pheric contamination by an envelope of molten flux to protect liquid metal and a layer of unfused granular flux which […]

It is the most commonly used welding process. The principle of the process is shown in Fig. 2.4. It uses a consumable covered electrode consisting of a core wire around which a flux coating containing fluorides, carbonates, oxides, metal alloys and cellulose mixed with silicate binders is extruded. • This covering provides arc stabilizers, gases […]

An arc is a sustained electric discharge in a conducting medium. Arc temperature depends upon the energy density of the arc column. Arc could be used as a source of heat for welding. Fig. 2.4 Diagrammatic sketch of arc flame Arc welding is a group of welding processes that use an electric arc as a […]