Electroslag welding of metal

Electroslag welding is ideal for welding thick parts, from 15 mm to 600 mm thick and even more. This welding technology involves heating the melting zone with heat from a slag pool heated by an electric current. The slag provides excellent protection for the solidification zone from oxidation and hydrogen, which has a negative impact. Hydrogen in the metal can cause cracks, so protection is essential when melting the metal.

The electroslag welding process is unique in that it does not require a welding arc. It utilizes the heat generated by passing the welding current through the molten slag, which conducts the current. First, the two parts to be welded are connected with special clamps. An electrode is inserted into the joint between the parts. The electrode, energized at 400 A, is immersed in the slag pool, intensely heating the slag until its temperature exceeds the melting point of the metal. This causes the metal edges to melt, leaving a strong weld. Thus, the slag acts as the weld.

Welding is performed vertically from the bottom up. As the weld solidifies, the welding unit moves upward, leaving a weld seam. The optimal electrode feed speed is selected, allowing the gap between the electrode tip and the weld pool surface to remain constant. This welding method allows for welding metal of unlimited thickness. Flux is gradually added as the weld progresses. Copper crystallizer sliders move with the welding unit, cooled with water. The unit travels at a speed of 1-1.2 m/hour.

Advantages and some features of electroslag welding

Electroslag welding produces a very strong weld seam, capable of bearing heavy loads. This weld strength is due to the displacement of hydrogen in the weld pool, which impairs weld strength. The mechanical properties are excellent. When the heat source is removed, cooling and solidification occurs at the base of the weld, beginning with the partially melted grains of the base metal and progressing toward the weld along the fusion line.

During the welding process, the weld-affected zone (HAZ) undergoes slight changes in structure, and therefore the properties of the metal. This does not result in any structural deformation of the product.

Electroslag welding of metal has the following advantages:

• the thickness of the products to be welded is very large;
• You can weld different metals: cast iron, steel, copper, titanium, aluminum and their alloys;
• welding in one pass;
• no need to remove slag;
• there is no need to prepare the part (chamfer the edges);
• one or more wire electrodes can be used;
• obtaining a high-quality weld with excellent mechanical properties.

Disadvantages of electroslag welding of metal:

• can only cook vertically;
• After welding some metals, the mechanical properties in the heat-affected zone change, weakening the metal, so additional heat treatment is necessary.

Thus, electroslag welding is a suitable method to achieve the required result.