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Electro Gas Welding â€“ Definition, Equipment, Process and Applications
Electro Gas Welding (EGW) is continuous arc welding process in which an electric arc is struck between a consumable electrode and the workpiece. The electro gas welding was developed in 1961. It is a vertical position arc welding process. In case of electro gas welding, a shielding gas is sometimes used, but pressure is not applied.
Electro gas welding is mainly used to make square groove welds for butt and t-joints.
Equipment Used in Electro Gas Welding
The electro gas welding process uses a constant voltage DC welding power supply. The voltage ranges from 30 V to 50 V, while the welding current ranges from 100 A to 800 A. The welding electrode has positive polarity.
Electro gas welding uses a wire feeder to supply the electrode, which is selected according to the material being welded. The electrode can be flux cored so it can provide protection to the weld from the atmospheric contamination or a solid wire electrode can also be used with a shielding gas (generally carbon dioxide) to protect the weld from atmospheric contamination.
The welding head is attached to an equipment which elevates it during the welding process. In electro gas welding setup, backing shoes are used which restrain the weld to the width of the workpiece. These backing shoes are made of copper and are water cooled to prevent them from melting.
Electro Gas Welding Process
The schematic diagram of the electro gas welding process is shown in the figure.
In electro gas welding (EGW), the heat produced by the electric arc is used to melt the electrode and the workpiece and allow to flow into the cavity between the parts being welded. The molted metal solidifies from the bottom up and thus joining the parts. A shielding gas or the gas produced by the disintegration of flux cored electrode is to protect the weld area from atmospheric contamination. The welding electrode is guided into the weld area either by a consumable electrode tube or by a moving head.
When the consumable electrode guide tube is used, the weld pool is composed of the molten metal (that is coming from the parts being welded), the electrode and the electrode guide tube. While, when the moving head is used, it uses an assembly of an electrode guide tube which moves upwards as the weld is laid.
In case of electro gas welding process, the welds must be vertical, varying to either side by a maximum of 15°. Generally, the workpiece must be at least 10 mm thick, while the maximum thickness of one electrode is about 20 mm. When, it is required to weld a thicker workpiece, additional electrodes are used.
As the electro gas welding process is an electric arc welding process, therefore, it requires that the welder must wear a welding helmet and the proper attire to prevent exposer to the molten metal and the bright welding arc. As the electro gas welding process is performed at great heights, therefore, the work and equipment must be properly secured and the welder should wear a safety harness to prevent injury in the event of accident.
Applications of Electro Gas Welding
Some of the applications of the electro gas welding are given as follows −
Electro gas welding can be applied to most steels, including low and medium carbon steels.
Low alloy high strength steel can be welded using electro gas welding.
Electro gas welding may also be used to weld some stainless steels.
If proper amount of heat is applied, then quenched and tempered steels may also be welded using the electro gas welding.
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