Characteristics of electroslag welding

Electroslag welding is a welding method that utilizes the resistance heat generated by current passing through molten slag. It has the following characteristics:

1. **Large thickness welding capability**
Electroslag welding can weld very thick workpieces in a single pass, typically used for welding workpieces with thicknesses of 40mm to 2000mm. Theoretically, the plate thickness that can be welded is unlimited, but in practice, it is limited by equipment, power supply capacity, and operating techniques. Commonly welded plate thicknesses are approximately 13-500mm.
2. **High production efficiency and low cost**
When welding workpieces thicker than 40mm, no beveling is required; a gap of 25-35mm between the welding ends is sufficient for a single-pass weld, resulting in high productivity. The consumption of welding wire and flux is low, and the thicker the workpiece, the lower the relative cost.
3. **Few weld defects**
The molten pool in electroslag welding is well-protected, and the liquid state is maintained for a longer time, allowing for a more complete metallurgical process. Gases and impurities in the molten pool have sufficient time to float out, resulting in fewer defects such as pores and slag inclusions in the weld. The weld metal has a low nitrogen content, making it less prone to defects such as pores, slag inclusions, and cracks.
4. **Coarse grain size in the welded joint**
Due to the long residence time at high temperatures in the weld and heat-affected zone, coarse grains and overheated structures are easily formed, reducing the impact toughness of the welded joint. Post-weld heat treatment, such as normalizing, is usually required to improve its properties.
5. **Suitable for vertical position welding**
The vertical position provides the best conditions for the formation of the molten pool and weld in electroslag welding. It can also be used for welding inclined welds (angle with the vertical line to the ground plane ≤ 30°). Pores and slag inclusions are less likely to occur in the weld metal.
6. **Stable welding heat source**
The heat source in electroslag welding is the resistance heat generated by the current passing through the liquid molten slag. The slag pool temperature can reach 1600-2000℃. The current mainly flows from the welding wire or the end of the plate electrode through the slag pool to the metal molten pool. The current field is conical, which is the main heat-generating area of ​​electroslag welding. 7. Gradually increasing and slowly cooling welding thermal cycle curve
Electroslag welding has a slow welding speed, a large heat input, a very wide heat-affected zone, and a relatively long high-temperature dwell time, leading to severe grain growth in the heat-affected zone.
8. High energy utilization efficiency
In electroslag welding, the current generates heat through the molten slag, and the slag covering the weld pool reduces heat loss. The energy utilization efficiency is significantly higher than that of arc welding, resulting in better economic efficiency.
9. Coarse-grained weld joint
Due to the large heat input and slow cooling rate, the weld and heat-affected zone remain at high temperatures for a long time, leading to coarse grains. This is a typical disadvantage of electroslag welding, but it is an inherent characteristic of the process.