Electroslag welding: varieties and essence

Welding operations with metals are mostly based on chemical-thermal melting processes. Depending on the equipment used, active consumables and, in general, the technical conditions for the organization of the process, the characteristics of the product also change. The main task of the welder is the formation of a strong seam, able to withstand the loads, which will also fall on the main structure. In this respect, electroslag welding is not the best solution to date, since the classical electric arc impact makes it possible to form seams that are more profitable for further operation. However, the use of slag baths for the melt process provides many other advantages for which this technology is used by large enterprises.

Essence of electroslag welding

The method of electroslag welding is based on the use of heat, which is produced during the melt process of the material. The resulting thermal energy is the factor that provides the welding operation. As a material that is subjected to a melt, a slag base is used. The initiator of the melt process is an electric current, so a special generator is used in the organization of the process. The special features of the process include the fact that electroslag welding can be performed only in conditions of vertical placement of blanks. Under the action of the heat produced, the liquid metal that is formed during the reflow of the electrode wires and the welded elements fills the space between the parts. To keep the molten bath of slag and metal from excessive overflow, water-cooled slides are installed from different sides of the working bath. As they weld, they rise and do not let the working mass flow out.

Technological process

The welding process begins with the excitation of the arc, which will be formed between the parts and electrode wires. The thermal energy of the arc melts the flux, after which the same slag bath is created, the level of which will rise. Due to the electrical conductivity property, the fused flux begins to shunt the arc, stopping its burning. In this case, the melting and heating of the flux continues due to thermal action, the source of which will be the current supplied to the liquid slag. That is, the technology of electroslag welding is based on the transfer of heat from the slag, which not only releases energy under the action of current, but also can directly transfer it to the working parts.

The electrode and the target metal are connected by means of a slag bath. Further, a metal bath is formed. This may require different time intervals, depending on the characteristics of the material. The main thing is that the metal liquid base lies on the level below the slag bath, but also requires the connection of molding sliders to prevent leakage. To do this, use copper sliders, cooled by water.

Varieties of welding

Approaches to the implementation of this method differ in the type of electrode used. For example, the classical scheme involves the use of an electrode wire, which, as it melts, is fed into a slag bath. With this approach, the master should also provide reciprocating horizontal movements to the electrodes, which ensures uniform heating of the welded parts throughout the thickness.

Another method involves the use of electrodes with a large cross-section or plates. In this case, the electrode will occupy most of the space formed by the gap between the blanks. The use of plates is also common. With such a scheme, electroslag welding is performed with the calculation of the dimensional correspondence of the active elements to the parts. In any case, their shape should be similar to welded blanks. The plates are fixedly fixed in the gap and, depending on the state of the slag bath, can be fed to the work area as the operation is performed.

Equipment for welding

As with traditional electric arc reconciliation, in this case a special apparatus is used. To determine its features, it should be noted that the electroslag technique, unlike other common welding techniques, can be realized at a current density of 0.1 a / mm ² , which is hundreds of times smaller than with the same arc method. To perform this task, we use automata corresponding to several conditions. First of all, the technique should provide a gap between the different edges of the bath. The second condition is expressed in the fact that the equipment for electroslag welding should allow vertical formation of the welded seam. And the last significant condition is that welding should be done in one approach. As additional equipment, wire feeding rollers, a current lead-in die, sliders with slats and tubes for cooling with water are also used.

Consumables for welding

The active basis for such welding is the mentioned electrodes, which can have several fixed axes. The supply to the slag bath is ensured at a constant speed. In addition to slag and electrodes, a melting mouthpiece can also be used. Depending on the requirements for the result, the operator can control the consumables in such a way that the process will be performed with varying degrees of intensity - the correction for manipulating the same electrodes to improve the heating is also done taking into account the type of metal. In general, from the point of view of complexity for the master, the process of electroslag welding with the contact principle of influence is most difficult. Usually contact-slag technique is used in cases where it is necessary to weld the rods to a flat surface.

Technology advantages

One of the main advantages of the method is the possibility of welding without the need for preliminary edge separation, since the process is realized with a gap of up to 3 cm between work pieces. Also, electroslag welding has a high deposition coefficient, which results in financial advantages in the form of savings on the organization of the event. Pros will be noticeable after the operation is completed. The point is that this type of welding ensures a symmetrical seam arrangement with respect to the axis. This factor eliminates the formation of angular deformations, which ultimately simplifies the installation of parts with their adjustment.

Applications

The possibilities of using this technique determine just its shortcomings. This method is inexpedient to apply in most typical welding jobs. Most often the technology is used in construction and industrial conditions. For example, the production of massive stands, the installation of turbine equipment, the installation of thick-walled drums and boiler units - this is only part of the common operations in which electroslag welding is used. The application of this method in production allows the assembly of large-sized structures. The principal difference between electroslag technique and other methods of reducing metallic elements is the assumption that it is possible to replace forged or cast massive parts with welded analogs made of small castings or forgings.

Conclusion

For a variety of reasons, even in the target areas of this technology, its use is not always permitted. Limitations are mainly related to technological deficiencies that make the use of the method impractical. For example, electroslag welding will be ineffective if it is planned to be used on a site where thermal sensitive materials are also present. That is, for economic reasons and the quality of the joint, the technology justifies itself, but there is another nuance. Such welding is characterized by a large zone of thermal influence, accordingly, in the work with the stationary arrangement of parts, all materials adjacent to them will also be subjected to a strong temperature effect.