1. Electrogas Flux cored Shielding
Electrogas Welding (EGW) is a mechanized welding process that uses either flux-cored or solid electrodes. The process is normally performed in the vertical position, and is designed to weld a joint in a single pass by depositing weld metal into a cavity created by separated joint faces on two opposite sides and water-cooled molding dams or “shoes” on the other two sides. During welding, shielding of the massive molten weld pool is provided by a gas The gas may be produced by the flux cored electrode or from an external source or both.
As the weld metal is being deposited, the water cooled “shoes” or dams are moved up the weld joint exposing the completed weld below. This necessitates the vertical movement of the welding head through which the wire or multiple wires are fed as well.
Flux cored Shielding
AWS Welding Handbook
Ed 8 Vol

2. Electrogas External Shielding Gas
Electrogas welding utilizes machine welding equipment. The vertical movement of the welding head is usually automatic. Other mechanized oscillation movement or multiple wires may also be provided in particularly thick plate or large weldments.
External Shielding Gas
AWS Welding Handbook
Ed 8 Vol

3. Electroslag
The Electroslag Welding process (ESW) is very similar to the Electrogas process in that a large weld pool is supported between the walls of a think plate and movable shoes which are moved up the plate as the weld progresses. Weld pool shielding is provided, however, by a molten slag bath. There are two variations of this process, the non-consumable guide method and the consumable guide method.
In the non-consumable guide method, the flux bath is refreshed with new flux occasionally. The consumable guide method uses a guide tube to guide the wire. It melts and adds additional weld metal. Some tube also contain flux coating so that flux in small quantities is continually added to the flux bath.
AWS Welding Handbook
Ed 8 Vol

4. Advantages Used for thick weldments Produces sound welds
Increased cost effectiveness as thickness increases
The advantages of the Electrogas and electroslag processes are its ability to weld thick vertical sections in a single pass thus eliminating the need for multi-pass welding techniques. This results in increased cost effectiveness.

5. Disadvantages Once started, the weld must continue
Coarse grained Heat Affected Zone
Disadvantages of these processes are that once the arc is initiated, it is extremely difficult to stop the process as any termination will result in solidification defects occurring in the weld metal.
In addition, the high heat input with these processes cause heat affected zone grain growth which may deteriorate mechanical properties in this portion of the weld.