Electroslag welding is used for welding of thick metal plates. Two plates are kept vertical at a distance of 2–3 cm. The filler wires and flux are kept in this gap. Here, the filler wires are used as the electrodes. The current supplied is AC. Initially an arc is created which melts the flux, and thereafter the molten flux short circuits; arc and heat is generated due to resistance heating of slag, and thus workpiece and electrodes are melted. The molten metal piece and slag are retained by a water cooled dam as shown in Figure 20.39. Since the weld pool formed is large and the welding speed is slow, the cooling rate is quite low. After cooling, heat treatment is required to restore the strength due to large grain size.
Figure 20.39 Electroslag Welding
Advantages
- This is the most suitable welding process for thick plates ranges from 50 to 900 mm.
- Weld is completed in single pass only. Thus, weld quality is improved.
- It gives high deposition rates.
- Flux consumption is lesser in comparison to submerged arc welding.
Limitations
- Welding is restricted to only vertical positions.
- This is suitable for welding of only thick metal plates.
- Solidification rate is required to be controlled for better quality of weld.
- After welding heat treatment is required.
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