One of the welding processes that used in Engineering field is the electrogas welding. There are several types of welding processes similar to. Abstract. Electrogas arc welding (EGW) is used for vertical position welding of sheer strakes and hatch side coamings of container ships because of its higher. (13 mm) could be satisfactorily welded in the vertical position in a single pass. This technique is called electrogas welding (EGW). EGW has enjoyed steady.
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Both flux cored and solid electrodes are available in various chemical compositions designed to introduce the necessary alloying elements to achieve strength, impact properties, or appropriate combinations of these and other properties in the deposited weld rlectrogas. The gas may be provided either from an external source, from a flux-cored electrode or from both the sources.
EGW uses a elextrogas voltagedirect current welding power supplyand the electrode has positive polarity. The edges or surfaces of the parts to be joined shall be prepared by oxygen cutting and shall be cleaned of oil, grease, moisture, scale, rust, or other foreign material.
Penetration and depth of fusion are generally increased by increasing the welding current and decreasing the voltage.
Nondestructive Examination techniques normally used with EGW include: The primary power for the welding power source should be turned off, and any shielding gas supply should be shut off at the supply source weldin leaving the work or stopping the work for any appreciable time, or when moving the machine.
Both variations use retaining shoes dams to confine the molten weld metal, which permits welding in the vertical position.
The following are among the contributing factors: Quenched and tempered steels may also be welded by the process, provided that the proper amount of heat is applied. Restarting of eleetrogas welds should be avoided if at all possible.
Electrogas Welding (EGW) – Welding Technology
Increasing the electrode extension by increasing the wire feed speed will decrease the arc voltage and result in a higher deposition rate and fill rate with a narrower weld width, Electrode OSI: If the weld pool is maintained higher in the shoe, then more slag escapes as spatter. Gas flow rates depend upon the equipment design, and manufacturer recommendations should be followed. Gas ports in the shoes and “gas boxes” are not required when using self-shielded flux cored electrodes.
Since filler metal is continuously added, there is a progressive solidification from the bottom of the joint, and there is always molten weld metal above the solidifying weld metal.
American Imn and Steel Institute 2. The overlap of liquid metal flows.
The guides may be preformed to fit along the length electgogas a curved joint. However, excessive preheat slows the weld cooling rate, increases the joint penetration, and may contribute to weld metal leakage and melt-through.
The base metal shall conform to the specification for. Two of the three remaining values shall be greater than the specified 20 ft-Ib 27 J energy leval. The weld metal is deposited into a weld cavity between the two pieces to be joined.
The electrode may be oscillated horizontally to weld thicker materials. The weld seam is less clean than the electro-slag welding. In addition, when using steel backing, excessive misalignment can result in meltthrough. The shoes are usually grooved to develop the desired weld reinforcement. A major difference between EGW and its cousin electroslag welding is that the arc in EGW electogas not extinguished, instead remains struck throughout the welding process. The consumable guide is selected so that its chemical composition is compatible with the base material.
These special electrodes allow a thin slag layer to form between the shoes and the weld to provide a smooth weld surface. Grinding may be required to stay within this tolerance.
Operators should also check the workpiece t,o verify that the joint is correct, and that the base metal condition will allow free passage of the welding head to the top of the joint. The welding head is attached to an apparatus that elevates during the welding process.
Electrogas welding – Wikipedia
Before starting to weld. For the more susceptible steels, each of the other factors becomes more critical. The starting sump should be seal welded at the joint, but should electrogss be sealed all around.