Description of the Electro-gas welding process-EGW
EGW refers to a continuous vertical locus of the arc welding. EGW similarly be defined as a process of high productivity derived and modified from ESW (Electro-slag welding). For this process, an arc is fixed in between consumable electrodes and workpiece. Sometimes, the shielding gas is employed though the pressure is never put into application. An arc within EGW is can never be extinguished (Kim et al.,67). However, it remains to get struck throughout the process of welding. EGW is used in making square-groove welds in support of t-joints and butt.
The groove welds are employed in the industry of shipbuilding as well as constructing storage tanks. Within the EGW, heat makes arc welding electrodes together with the workpieces to melt then flow into cavities between the welded parts. Then, there is a solidification of molten metal as of the bottom up, connecting welded components. The area welded becomes safeguarded from atmospheric contaminations through separating shielding gas through disintegrating flux-cored electrode wires. Electrodes get guidance into the field of welding through the consumable tube-like electrodes or moving variations using assembled electrode tube guides that move upwards when the weld is being laid. Thus, it keeps it from melting. EGW is applicable in various steels, which are of low and medium carbon. Also, it is applied to low alloys with higher strengths of steels as well as ones that are stainless.
Benefits of the process
- Higher rates of deposition
- The process makes it quicker to restart the weld
- Minimal angular distortion as a result of a smaller number of passes of welding
- The heat- zones, which have been affected, can be softened then embrittled as a result of the input of welding heat
- The weld is excellently visible for the operators.
Development of EGW
EGW was developed and refined in the year 1940 by Paton Institute in the United States. However, the technology is patented by Robert Hopkins (Sasaki et al. 64). It was developed to assist in shipbuilding, construction of bridges as well as used in the fabrication of the larger structural firms. The primary two California buildings are believed to be welded using the process of EGW. These are the Loss Angeles twin tower security pacific and Bank of America found in Sans Francisco. The method of EGW benefit incorporates the rate of high metal depositions. EGW has the capacity of laying metals at a rate of 16 and 19 kg every hour per electrode. It can weld thicker materials (Park 56). Multiple processes of welding need more than a single pass to weld thicker workpieces. However, one pass is often enough for EGW. The method is similarly efficient because materials handled and joint preparations are minimal as the filler metals used are higher.
Illustration
EGW is a process of machine welding since its operations need special equipment. The metal which has been welded gets deposited into the weld cavity between the joint pieces. Space is shielded with two copper dams (shoes) to avert molten slag as of running off. It mechanically drives the boots up. The electrodes, one or more, get fed through the conduit as well as the unremitting arc, get maintained through flux-cored wires at 400 A (Park 91). This needs a power of about 20Kw. Shielding is carried out by the use of inert gases like helium or argon as the material which is being welded.
Figure 1. Illustration of the process of EGW