Fusion Welding Process

Overview

Fusion welding processes- Fusion welding is a joining process that uses fusion of the base metal to make the weld. The three main type of the fusion welding are as follows:

1. Gas Welding :
Oxyacetylene welding (OAW)

2. Arc Welding :
Shielded metal arc welding (SMAW)
Gas-tungsten arc welding (GTAW)
Plasma arc welding (PAW)
Gas-metal arc welding (GMAW)
Flux-cored arc welding (FCAW)
Submerged arc welding (SAW)
Electroslag arc welding (ESW)

3. High-energy beam welding :
Electron beam welding (EBW)
Laser beam welding (LBW)

Since there is no arc involved in in the electroslag welding process, it is not exactly an arc welding process. For convenience of discussion, it is grouped with arc welding processes.

Electroslag strip Cladding

Fusion Welding

(REF.- Welding Metallurgy, Second Edition. Sindo Kou Copyright 􀂶 2003 John Wiley & Sons, Inc. ISBN: 0-471-43491-4)

Comments

Oxyacetylene Welding (OAW)

OXYACETYLENE WELDING The Process:- Gas welding is a welding process that melts and joins metals by heating them with a flame caused by the reaction between a fuel gas and oxygen. Oxyacetylene welding (OAW), shown in Figure is the most commonly used gas welding process because of its high flame temperature. A flux may be used to deoxidize and cleanse the weld metal. The flux melts, solidifies, and forms a slag skin on the resultant weld metal. Three different types of flames in oxyacetylene welding: neutral, reducing, and oxidizing , which are described next. Advantages and Disadvantages :- The main advantage of the oxyacetylene welding process is that the equipment is simple, portable, and inexpensive.Therefore, it is convenient for maintenance and repair applications. However, due to its limited power density, the welding speed is very low and the total heat input per unit length of the weld is rather high, resulting in large heat-affected zones and severe distortion.The...

Electroslag Welding (ESW)

ELECTROSLAG WELDING The Process :- Electroslag welding (ESW) is a process that melts and joins metals by heating them with a pool of molten slag held between the metals and continuously feeding a filler wire electrode into it, as shown in Figure. The weld pool is covered with molten slag and moves upward as welding progresses. A pair of water-cooled copper shoes, one in the front of the workpiece and one behind it, keeps the weld pool and the molten slag from breaking out. Similar to SAW , the molten slag in ESW protects the weld metal from air and refines it. Strictly speaking, however, ESW is not an arc welding process, because the arc exists only during the initiation period of the process, that is, when the arc heats up the flux and melts it. The arc is then extinguished, and the resistance heating generated by the electric current passing through the slag keeps it molten. In order to make heating more uniform, the electrode is often oscillated, especially when welding thicker...

Plasma Arc Welding (PAW)

PLASMA ARC WELDING The Process:- Plasma arc welding (PAW) is an arc welding process that melts and joins metals by heating them with a constricted arc established between a tungsten electrode and the metals, as shown in Figure 1. It is similar to GTAW , but an orifice gas as well as a shielding gas is used. As shown in Figure 2, the arc in PAW is constricted or collimated because of the converging action of the orifice gas nozzle, and the arc expands only slightly with increasing arc length. Direct-current electrode negative is normally used, but a special variable polarity PAW machine has been developed for welding aluminium, where the presence of aluminium oxide films prevents a keyhole from being established. Fig-1 Plasma arc welding: (a) overall process; (b) welding area enlarged and shown with key holing. Arc Initiation:- The tungsten electrode sticks out of the shielding gas nozzle in GTAW (Figure 1b) while it is recessed in the orifice gas nozzle in PAW (Figure...

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