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 of the process organization, the characteristics of the resulting product also change. The main task of the welder is the formation of a durable weld that can withstand the loads that will also fall on the main structure. In this regard, electroslag welding is not the best solution to date, since the classic electric arc effect allows you to form more favorable seams for further operation. However, the use of slag baths for the melt process provides many other advantages for which large enterprises use this technology.
The essence of electroslag welding
The electroslag welding technique is based on the use of heat, which is generated during the melt of the material. The resulting thermal energy is the very factor that ensures the welding operation. As the material that is being melted, a slag base is used. The causative agent of the melt process is electric current, therefore, a special generator is used in the organization of the process. The process features include the fact that electroslag welding can be performed only in conditions of vertical placement of workpieces. Under the action of the generated heat, a liquid metal, which is formed during the fusion of electrode wires and welded elements, fills the space between the parts. To keep the liquid bath of slag and metal from excessive flow, water-cooled sliders are installed on different sides of the working bath. As the seam is welded, they rise and do not allow the working mass to 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 property of electrical conductivity, fused flux begins to shunt the arc, stopping its burning. In this case, the melting and heating of the flux continues due to thermal exposure, 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 slag, which not only releases energy under the influence of current, but can also directly transmit it to the working parts.
The electrode and the target metal are bonded to each other through a slag bath. Next, a metal bath is formed. This may require different periods of time, depending on the characteristics of the material. The main thing is that the metal liquid base lies a level below the slag bath, but also requires the connection of molding sliders that inhibit leakage. To do this, use copper sliders cooled by water.
Types of welding
Approaches to the implementation of this method differ in the type of electrode used. For example, the classical scheme provides for the use of electrode wire, which is fed into the slag bath as it melts. With this approach, the master must also inform the electrodes of the reciprocating horizontal movements, 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 workpieces. The use of plates is also common. With this scheme, electroslag welding is performed with the expectation of dimensional correspondence of the active elements to the parts. In any case, their shape should be similar to the workpiece being welded. The plates are fixedly fixed in the gap and, depending on the state of the slag bath, can be supplied to the working area as the operation is performed.
Welding equipment
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 technologies, can be implemented at a current density of 0.1 a / mm 2 , which is hundreds of times less than with the same arc method. To accomplish this task, automata are used that correspond to several conditions. First of all, the technique should provide a gap between the different edges of the bath. The second condition is that the equipment for electroslag welding must allow the vertical formation of the weld. And the last significant condition is that welding should be performed in one approach. As additional equipment, wire feed rollers, a current-conducting mouthpiece, sliders with slats and tubes for water cooling are also used.
Consumables for welding
The active basis for such welding is the mentioned electrodes, which may have several fixed axes. The feed to the slag bath is provided 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 carried out with varying degrees of intensity - correction for manipulating the same electrodes in order to increase heating is also done taking into account the type of metal. In general, from the point of view of complexity for the master, the most difficult process of electroslag welding with the contact principle of exposure. Typically, the contact-slag technique is used in cases where it is necessary to weld the rods to a flat surface.
Technology benefits
One of the main advantages of the method is the possibility of welding without the need for preliminary separation of the edges, since the process is implemented with a gap between the workpieces of up to 3 cm. Also, electroslag welding has a high deposition rate, which also gives financial advantages in the form of savings on the organization of the event. Pluses will be noticeable after the operation is completed. The fact is that welding of this type provides a symmetrical arrangement of the seam with respect to the axis. This factor eliminates the formation of angular deformations, which ultimately simplifies the installation of parts with their correction.
Fields of application
The possibilities of using this technique determine precisely its disadvantages. This method is impractical to use in most typical welding operations. Most often, the technology is involved in construction and industrial conditions. For example, the manufacture of massive beds, the installation of turbine equipment, the installation of thick-walled drums and boiler units are only part of the common operations that use electroslag welding. The application of this method in production allows the assembly of large structures. The fundamental difference between electroslag technology and other methods of reducing metal elements is the assumption of the possibility of replacing forged or cast massive parts with welded analogues made of small castings or forgings.
Conclusion
For a number of reasons, even in the targeted areas of this technology, its application is not always allowed. Limitations are mainly associated with technological shortcomings that make the use of the method inappropriate. For example, electroslag welding will be ineffective if it is planned to be used at a site where materials that are sensitive to thermal effects are also present. That is, for economic reasons and the quality of the joint obtained, the technology justifies itself, but another nuance arises. Such welding is characterized by a large heat-affected zone; accordingly, in working with a stationary arrangement of parts, all materials adjacent to them will also be subjected to strong temperature effects.