What is electroslag welding

Electroslag welding

If it is necessary to connect metal structures with a thickness of 2 cm or more, electroslag welding is used. A very unique feature of this type of welding work is thermal energy, which is the main source of heating. Heat appears directly in the bath where the molten flux is located at the moment when the electric current passes from the electrode to the product itself. ESW performs well when connecting metal parts of unlimited thickness.

The essence of electroslag welding: the secret of technology

The formation of a working slag bath occurs due to the melting of the slag flux. Throughout the entire process, the same depth of the slag bath is maintained. The welding current, which passes through the electrodes located in the bath itself, ensures constant temperature and maintains the electrical conductivity of the slag. When the metal pool crystallizes, the necessary weld is formed.

The electroslag welding process is characterized by certain features:

1. Heat emissions during the welding process completely depend on the types of additional filler materials and the characteristics of the incoming current into the slag bath.
2. Preservation of the minimum gap directly between the workpieces being welded. It must be maintained at minimum values ​​to avoid significant deformation of the edges of parts and displacements.
3. The values ​​of internal stresses of the welding process are characterized by significant indicators.
4. After completion of the welding procedure, additional heat treatment is required. This procedure allows you to improve the current structure of the workpiece joint.

The material used as the melting base is slag base. The melting process is initiated by an incoming electric current, which is provided by a specialized current generator. A special feature of the EHS is the fact that the parts must be arranged vertically. To eliminate leaks of the working mass, special cooled sliders are installed on the workpieces.

Electroslag welding methods

There are 3 directions of ESW, each of which has its own surfacing:

1. Ensuring welding bonding using wire electrodes.
2. Connection using a melting mouthpiece.
3. Welding is performed with electrodes with a large cross-sectional area.

The welding process, provided by wire electrodes, is widespread in modern industry. It can be carried out using 1, 2, 3 electrode wires with no vibrations or in combination with them. ESW can also be produced using wire electrodes without direct entry of the nozzle into the weld gap.

The process of obtaining a working seam through the use of a melting nozzle is considered a common universal type of joining workpieces of various thicknesses, as well as curved parts. The melting mouthpiece has the form of several plates or combined rods, in which there are special channels for supplying electric current and wire.

Electroslag welding modes are based on the use of slag as the main heat source during the welding process.

Devices for electroslag welding

A feature of any unit intended for electroslag welding is the minimum total consumption of flux materials. These devices can provide the connection of parts of different thicknesses in a single welding pass. In this case, there is no need to cut the edges, and the productivity of ESW is significantly superior to multilayer flux welding, which is performed automatically.

Hardware welding devices provide the supply of electrodes directly to the point of contact of the workpieces. They also maintain the continued sustainability of any electroslag operation. A common practice for solving such problems is the use of automatic units for welding work, which are able to move vertically more evenly and smoothly than heavy semi-automatic devices.

Any unit that provides high-quality ESW meets the general requirements for the implementation of this type of welding work:

• The technical device must create and maintain a gap separating the parts of the bath.
• The possibility of vertical formation of the current connecting seam must be maintained.
• The weld must be created in one approach.

Additional devices that ensure high-quality welding are: wire rollers responsible for the constant supply of wire, a mouthpiece with the ability to transmit current, additional sliders with holding bars and water cooling tubes.

Advantages and scope of ECS technology

Electroslag welding technology has advantages due to which it is actively used in modern factories:

• In the process of creating a welded joint, there is no need to separate the edges.
• Any weld created using ESW technology is created under conditions of excessive deposition. The deposition rate provides serious economic benefits to any enterprise.
• With respect to the axial planes, the symmetry of the seam is completely preserved. This advantage is manifested when connecting workpieces with upcoming adjustments.

The scope of application of electroslag welding is concentrated both in the construction industry and on production sites. Thanks to EHS, massive frames are manufactured, turbines are installed, and strong connecting seams are created for the installation of huge drum structures and heavy devices for boiler rooms. The manufacturing application of this technology is in the assembly of large structural projects.

As a result, the economic component and the quality of the resulting butt joint when using electroslag welding have decent indicators, but the excessive thermal zone significantly limits the scope of application of this type of welding.

Source: https://svarkagid.com/jelektroshlakovaja-svarka/

What is the essence of electroslag welding?

There are many types of welding that use different energy sources, many of which are uncommon and rarely used. Electroslag welding is one of these options.

This technology is based on the fact that the heating of the joint zone occurs when exposed to the heat of the slag bath. The bath, consisting of slag, is heated using electric current.

Slag is used as a protective medium, since it creates an impenetrable shell through which hydrogen and oxygen, which oxidize the crystallization zone, cannot penetrate.

Electroslag welding process

One of the features of the process is the absence of an electric arc for welding. Here, an electric current is simply released into the slag, which conducts it unhindered.

Due to this, a sufficient amount of heat is released, which melts the edges of the base metal. The current-conducting electrode is immersed in a slag bath.

Due to the fact that there is complete contact, the electric arc does not burn, but the flow of current continues. Electricity flows through the molten slag.

Most often, the welding process takes place in a vertical position, and the seam is created from the bottom up. A gap is allowed between the parts being connected. In order for the seam to form normally on both sides of the gap, copper sliders with crystallizing properties are mounted.

These properties are obtained by cooling the sliders with water. When a seam is formed at a specific location of the weld pool, the copper parts move in the direction of the further passage of the seam.

These parts are made of copper, since it has a higher melting point than the base metal.

Advantages

Electroslag welding can be used to weld cast iron, steel, aluminum, titanium and other metals that are difficult to weld.

This technique is also great for thick metals that other welding will not take. Here the joining process takes place in one pass and there is no need to risk multi-layer seaming.

This eliminates the need to remove slag each time after a pass.

The chamfers on the edges cannot be removed. During welding, either one or several wire electrodes are used, and their cross-section can be different. This helps to achieve high productivity of the process and makes it cheaper. Moreover, in comparison with other methods, with increasing thickness of the workpiece, these indicators only increase.

Flaws

Electroslag welding has certain disadvantages. Technically, it can only be carried out if the metal thickness is 1.6 cm or more.

The welding process becomes most profitable only with a thickness of 4 cm, which is not always feasible in the industrial sector.

Sometimes it is necessary to carry out additional heat treatment so that the metal of the weld and near it takes on the properties that are needed for work, since they change under the influence of ESW.

Source: https://steelfactoryrus.com/v-chem-zaklyuchaetsya-suschnost-elektroshlakovoy-svarki/

Electroslag welding (page 1 of 3)

Ministry of General and Professional Education of the Russian Federation.

Omsk State Technical University

Department of Equipment and Welding Technology.

Course work.

In the course “Engineering Creativity”.

On the topic: “Electroslag welding.”

Completed:

Student MSF S-110

Checked:

Associate Professor Ph.D.

Shestel L.A.

Omsk, 2000

1. Introduction

Electroslag welding (ESW) has found wide application in the manufacture of metallurgical, rolling and power equipment, in boiler, hydraulic and press construction, in construction, etc. Using this welding method, structures are made from carbon and alloy steels, titanium, aluminum, copper and their alloys. The range of welded metal thicknesses is 20-2500 mm.

The modern equipment of EHS is such that it allows solving almost any industrial problem at the highest technical level. Moreover, as many years of experience have shown, the effectiveness of using ESW largely depends on the correct choice of welding equipment, as well as the rational solution of issues of welding technique and the use of appropriate technological equipment.

annotation

In this work, I considered a type of welding such as electroslag welding. The welding process itself, welding methods and, accordingly, their application in various industries, including mechanical engineering, were considered. A table of classification of various welding methods is provided. Some technical characteristics of this process are considered.

:

Introduction.

1. Description of the process.

2. Technological parameters.

2.2 Classification of types of electroslag welding.

2.3Features of the electroslag process.

3. Scope of application.

Conclusion.

Literature.

1.Process description

A welding method based on the release of heat when an electric current passes through molten slag is called electroslag welding . In the space formed by the edges of the products being welded and the forming devices, a bath of molten slag is created, into which a metal rod - an electrode - is immersed.

The current, passing between the electrode and the base metal, heats the melt and maintains a high temperature and electrical conductivity in it. The temperature of the slag bath must exceed the melting point of the base and electrode metal. The slag melts the electrode immersed in it and the edges of the product.

The molten base metal, together with the electrode metal, collects at the bottom of the slag bath and forms a metal bath, which, when solidified, forms a seam connecting the edges of the product. As it melts, the electrode moves downwards.

The best conditions for melting the base metal and for obtaining a deep slag bath are created when the weld axis is vertical. Therefore, electroslag welding is most often used in combination with forced formation of a weld pool. Electroslag welding in the lower position is less convenient and has not become widespread.

2.Technological parameters of the electroslag welding (ESW) process

The essence of the forced formation method is the artificial cooling of the surface of the metal bath.

The main purpose of slags during EHS is the conversion of electrical energy into thermal energy. Therefore, the main characteristic of slags is their electrical conductivity and its dependence on temperature.

If there were a slag that did not change its conductivity depending on temperature, then it could be used relatively easily for welding purposes.

It is always possible to select a voltage that, when applied to a constant resistance, will cause the required power to be released in this resistance and, therefore, will maintain the required temperature in it.

In fact, the conductivity of molten slag increases sharply with increasing temperature, and below a certain temperature, slag is practically non-conductive. This circumstance complicates the stabilization of the process.

Some slags containing titanium dioxide are good conductors even in the solid state at room temperature. This kind of slag has electronic conductivity, in contrast to the ionic conductivity of slags in a liquid state.

Unlike submerged arc welding, in electroslag welding almost all the electrical power is transferred to the slag pool, and from it to the electrode and the base metal. The condition for the stability of the process is the constancy of the temperature of the slag bath, in other words, the equality of the received and emitted heat.

One of the obstacles that arises in the practical application of the electroslag process is the possibility of an arc discharge occurring between the electrode and the free surface of the slag bath or, most often, in the depths of the slag bath. Such a discharge can be very unstable, and its occurrence during electroslag welding can lead to the formation of weld defects.

To prevent an arc discharge, welding must be carried out under conditions opposite to the conditions for stabilizing the arc discharge: in a deep slag bath, on alternating current, at low open circuit voltage and using slags with low stabilizing properties. These measures make it difficult for an arc discharge to occur and increase the stability of the electroslag process.

However, if the stability conditions of the arc discharge are excessively deteriorated, there are cases of disruption of the stability of the electroslag process due to, for example, accidental leakage of the slag bath.

To restore a slag bath, a fairly stable arc discharge is required with a shallow bath and a rapid decrease in its stability with a deep bath.

This can be achieved by using a small diameter electrode, increasing the gap between the edges or changing the open circuit voltage of the welding transformer accordingly. Increasing the gap is not economically profitable.

The use of slags based on calcium fluoride, which have high electrical conductivity, significantly reduces the time required for the transition from the arc process to the electroslag process.

In order for the electrode metal to reliably fuse with the base metal, the surface of the latter must be previously melted and have a temperature close to the melting point. In addition, the metal surface must be reliably protected from oxidation. When arc welding in the lower position, melting of the edges and filling of the groove with metal, as a rule, does not occur simultaneously.

The metal from the cavity melted by the arc is thrown back, and the cavity is filled only after the arc is withdrawn. When welding vertical seams, this phenomenon is expressed even more clearly; the metal of the edges, melted by the arc or slag, flows down, forming a common bath with the electrode metal.

As a result of melting of the edges, a cavity unfilled with metal always forms above the metal bath.

In cases where the edges of the base metal begin to melt well above the surface of the metal pool, the edges immediately above the pool may find themselves cooled below the melting point. In this case, so-called non-fusion is possible. It should not be mixed with undercooked edges where they remain unmelted. If there is no fusion, the edges are melted, but they are not fused to the weld metal.

Non-fusion becomes possible when the welding voltage is too high, the slag pool is too deep and when using slags that change little in their electrical conductivity and viscosity with temperature.

With normal characteristics of the slag and correctly selected welding modes, premature melting is prevented by the thermal and electrical insulating layer formed by the slag at the cold edges of the product.

Thanks to it, the current between the electrode and the metal bath passes as if in an insulated tube, and heating of the edges, even with large interelectrode gaps, begins at the very surface of the metal bath.

Most of the heat generated in the slag is transferred into the bath by the electrode metal. Almost all the thermal energy is transferred to the base metal through the surface of the metal bath.

If the welding voltage is kept higher than necessary to melt the electrode and the edges of the base metal, then the excess heat in the slag bath is used to increase the penetration of the edges. If this is not necessary, then this heat can be used to melt the filler material. It can be supplied in the form of a wire, just like an electrode, or in separate small pieces.

As the electrode diameter decreases, the interelectrode gap decreases and the risk of non-fusion decreases sharply. Electrode vibrations in the horizontal direction have an even greater influence on the size of the interelectrode gap and the nature of melting of the base metal.

X-ray studies and oscillography of the electroslag welding process in various modes have shown that the metal is transferred from the electrode to the metal bath in the form of drops.

The larger the droplet size, the lower the welding current, the higher the voltage between the electrodes and the metal bath, and the greater the depth of the slag bath.

On the contrary, lowering the welding voltage, decreasing the pool depth and increasing the current contribute to the fine-droplet transfer of electrode metal into the weld pool.

At high electrode feed rates common when welding low-carbon steels, low voltages, or shallow slag pool depths, metal droplets may connect with the metal pool before being separated from the electrode.

This metal connection between the electrode and the bath lasts for a very short time; it is destroyed almost instantly under the influence of electrodynamic forces that arise in the conductor and increase sharply with increasing current density. However, due to the high frequency of short circuits, the average time for the current to pass through the metal can constitute a significant proportion of the total welding time.

This phenomenon is not in the nature of a short circuit. The total conductivity of the welding zone at the moment of short circuit increases only 1.5 - 1.7 times. The power, depending on the characteristics of the power source, changes slightly or increases.

Source: https://mirznanii.com/a/170906/elektroshlakovaya-svarka

Basic assumptions and simplifications adopted in the classical theory of heat propagation during welding

At the current level of development of mathematics, an analytical solution to the heat equation in general form (5.21) has not yet been found, however, with the introduction of some assumptions and simplifications, it is possible to obtain partial ones suitable for practical use 

Differential heat equation

The complex process of changing the temperature of points of a body with coordinates jc, y, z in time t is described by the differential equation of thermal conductivity. To derive this equation, it is necessary to consider the heat balance in a certain elementary volume  

Source: https://msd.com.ua/teoriya-svarochnyx-processov/elektroshlakovaya-svarka-11/

Characteristics and application of electroslag welding. Methods, technology, advantages and disadvantages

Electroslag welding belongs to the thermal class and is a type of fusion welding. The heating source is the heat released when the energy carrier passes through the slag bath.

The working process takes place in a vertical plane and consists in the passage of a welding electric current circuit through the electrode, base metal and liquid slag. Melting of the base metal and filler material occurs due to the heat from the heated slag bath.

Electroslag welding is classified according to the type, number of electrodes and the presence of electrode vibrations.

GOST standards

Requirements, technical conditions, types of connections and other information related to electroslag welding are contained in mandatory GOST standards. Some standards:

1. Welding processes : GOST 30482-97 - rules for the technological process of working with a wire electrode or a consumable nozzle for low-alloy and carbon steels.
2. Welding materials : GOST 9087-81, GOST 30756-2001 – technical specifications for fused welding fluxes for electroslag welding and technologies.
3. Welded joints : GOST 15164-78 – types, elements, dimensions.

Where is it used?

The main area of ​​application is heavy engineering.

Possibility of use:

• connection of thick-walled sheets and parts (armored hulls of ships, shafts of hydraulic turbines, frames of powerful presses and rolling mills, armor of tanks, drums of high-pressure boilers);
• welding of metals having different chemical compositions;
• construction of casings domain;
• production of welded-forged and welded-cast structures;
• production of metallurgical equipment , thick-walled cylinders.

The method is also used for welding metal of small thickness (14-30 mm), for example, installation joints of ship hulls on a slipway.

Welding methods

Electroslag welding methods depend on the type of electrodes used and are divided into:

• electrode wires;
• large cross-section electrodes;
• melting mouthpiece.

Using electrode wires

The process is performed using a wire electrode with a cross-sectional diameter of 2-3 mm without transverse vibrations.

The speed of wire feeding into the slag bath must be constant. The method is used when welding metal up to 50 mm thick.

To weld thicker metal, several electrode wires are used. The electrodes move in a reciprocating manner in a direction perpendicular to the longitudinal axis of the seam being welded.

Use of large cross-section electrodes

Rods and plates of round, square or other cross-section are used. The dimensions and number of electrodes depend on the size of the parts being connected, the shape and size of the holes and cavities being welded.

The method is mainly used when the elements being welded are thick and the seam height is up to 1 m.

As it melts, the plate electrode is lowered into a slag bath, the depth of which is 20-25 mm. The formation of a weld occurs as a result of the connection of the molten base metal with the molten material of the plates.

Application of melting mouthpiece

The method combines welding with electrode wires and large cross-section electrodes. A steel plate (mouthpiece) is installed motionlessly in the gap between the parts to be connected. It has tubes or grooves through which electrode wires are passed.

The mouthpiece remains stationary during the welding process. Electrode wires are fed into the slag bath, which melt and fill the gap between the elements being connected. Simultaneously with the wire, the part of the mouthpiece that is located in the slag bath melts.

Electroslag welding mechanism

The size of the mouthpiece and the number of wires are selected in accordance with the dimensions of the parts to be welded. This method is used when connecting elements with a complex cross-section and low seam heights. The melting mouthpiece is made with a cross-section of the same shape as that of the parts being connected.

Welding technology

The parts to be welded are installed vertically, leaving a sufficient gap between the edges. The formation of the weld metal is forced. A wire electrode or steel plate (rod) and flux are supplied to the welding zone. An arc burns between the wire and the metal at the beginning of the process.

After a sufficient layer of liquid flux (slag bath) has formed, the arc goes out and the electric current passes only through the flux. The generated heat promotes further melting of the flux, wire electrode and edges of the materials being welded.

The molten metal forms a weld pool by flowing to the bottom of the slag pool.

The welding head, together with copper mold sliders, moves along the parts to be joined from bottom to top, holding them. The sliders that form the weld metal are cooled through channels through which water circulates.

The goal is to ensure normal formation of the seam and prevent leakage of liquid slag and metal from the melting space. As the gap fills, the slider plates move upward.

The metal of the bath cools, crystallization occurs and a weld is formed along the entire height of the edges of the materials being joined.

Equipment

The method requires the use of equipment - automatic and semi-automatic welding machines, machines and installations.

The automatic welding machine for slag welding contains:

• power supply;
• welding head;
• devices (sliders) for forced retention of the weld pool;
• mechanisms for moving the welding machine and electrodes;
• controls;
• wire spools;
• Flux hopper;
• devices for monitoring the position of the weld pool.

Approximate cost of welding machines on Yandex.market

Advantages and disadvantages

The positive qualities of the method include:

1. Possibility of single-pass welding of products with unlimited thickness . The consequence is a reduction in the labor intensity of the welding process, cheaper production, and improved quality of seams.
2. There is no need for special preparation of the edges of parts , which reduces the amount of preparatory work.
3. Flux consumption is 15-20 times less compared to submerged arc welding.
4. The vertical position of the welding process does not require frequent turning of products.
5. Ensuring uniform penetration of the edges of the joined elements.
6. No angular deformations on the sheets after welding.
7. High performance.

Flaws:

• mandatory vertical seam orientation;
• inadmissibility of interrupting the welding process to avoid defects;
• the need to install additional equipment (sliders, slats);
• coarse-grained seam structure;
• the need for heat treatment of the finished product in order to improve strength.

Source: https://elsvarkin.ru/texnologiya/vidy/elektroshlakovay-svarka/

What is the essence of electroslag welding - a metalworker's guide

Electrode welding, which has become widespread due to its relative simplicity, is not always able to ensure stable quality of the weld structure. Meanwhile, in the manufacture of certain types of products this characteristic is important. In order to eliminate the existing technological disadvantage, an electroslag welding technique was developed. It is called ESH for short.

Look to the root

The essence of the process is that a special chemical composition - welding flux - is placed into the prepared gap between the parts being connected, which is acted upon using an electric arc.

As a result of heating, the flux melts, turning into slag, which protects the processing area from exposure to atmospheric air. When using this technology, the molten metal cools slowly, which creates favorable conditions for the formation of a high-quality structure of the connecting seam.

It is quite difficult to understand what electroslag welding is by watching a video. Indeed, in this case, the audience gets an idea only of the external side of the process.

It is easier to understand the essence of electroslag welding if we consider this process in a simplified form. Everything happens as follows:

• The parts to be joined are installed with a certain gap, the value of which varies depending on the size of the product, the chemical composition of the material and the parameters of the welding current. A chemical called flux is placed in this gap and an electrode is applied to it.
• The current supplied to the electrode passes through flux, the composition of which can be different. As a result of heating, a so-called slag bath is formed, inside which the temperature necessary for melting the metal is maintained. Slag, lighter than metal, is always on top, blocking the flow of atmospheric air to the weld formation zone and increasing the cooling time of the molten metal.
• To keep molten materials from flowing out, the processing area is fenced with water-cooled movable sliders made of copper. In some cases, it is possible to use the enclosing plates remaining on the finished part.

Special approach

Equipment for electroslag welding has its own characteristics. In particular, for the convenience of performing work, it is customary to use flat or strip electrodes rather than cylindrical ones. To optimize the work process and achieve the specified characteristics of the weld, fluxes of various compositions are used.

• AN-348A. Characterized by a high content of ferric iron, it belongs to the high-silicon manganese compounds and is well suited for joining unalloyed or low-alloy steels.
• FC-7. Similar in characteristics and conditions of use to AN-348A, it provides better process stability in shallow slag baths.
• Fluxes AN-8, FC-21, AN-22 belong to the group of low-silicon manganese mixtures. For heat-resistant steels of the pearlitic class, FC-21 is better suited, for carbon and low-alloy steels - AN-8, and for medium-alloy steels - AN-22.
• Low-silicon, manganese-free compounds marked AN-9 and AN-25, which replaced the AN-2 flux developed before the start of World War II, are well suited for welding alloy steels. It was thanks to the latter that the armor plates of domestic tanks were tightly connected.
• It is also worth mentioning compounds belonging to the fluoride group. With the help of ANF-5, parts are made from stainless steel, and the use of ANF-14 is justified when we are talking about welding or surfacing of cast iron.

Of course, this is not a complete list of fluxes, but only individual examples illustrating how the chemical composition of the substances used to create a slag bath can affect the parameters of the electroslag welding process.

Advantages

Electroslag welding has a number of undoubted advantages that cannot be neglected when organizing production processes.

• The ability to ensure a stable and high-quality seam structure when connecting parts of significant mass and thickness.
• There is no need for preliminary chamfering of the edges and subsequent processing of the finished product to remove slag.
• In the case of simultaneous use of several electrodes, it becomes possible to apply a welding seam along the entire length in one pass, which significantly reduces work time and speeds up production.

Flaws

Wider dissemination of the technology is hampered by its shortcomings, or more precisely, by the specific features of the process.

• In this way, it is possible to weld only vertical seams, which is only permissible when manufacturing parts of a relatively simple shape.
• To create the necessary conditions for melting the flux and maintaining the slag temperature at a given level, special equipment is required.
• The method is not applicable if the thickness of the sheets of metal being joined is less than 16 mm. In fact, even in this case, the economic efficiency of electroslag welding remains in question. It really becomes justified when working with metal with a thickness of 40 mm or more, and reaches its highest efficiency when this figure exceeds 100 mm.

It is important to know!

When planning to use this technology, you must first sensibly evaluate all its advantages and disadvantages. There are a number of important points to consider.

• The metal surface at the junction must be thoroughly cleaned of dirt and oxidation. Otherwise, the melting process inside the slag bath will be unstable.

• To ensure the best quality of the welded joint, the temperature of the metal should be as close as possible to the melting point.
• The appearance of an arc discharge in the depths of the slag bath or between its free surface and the electrode is a common cause of weld defects. That is why special attention should be paid to arc regulation.

New opportunities

It is not difficult to guess that electroslag welding, which requires qualified personnel, the use of special equipment and has a number of strict technological restrictions, cannot be carried out at home. Nevertheless, many enterprises actively and quite successfully use this technique. There are several reasons for this.

• With proper organization of the process, the structure of the connecting seam is as close as possible to the structure of the material being joined, which ensures high strength of the finished products.
• This strength is so great that in many cases, electroslag welding technology eliminates the use of complex equipment necessary for casting and forging workpieces, as well as their subsequent processing.
• Compared to other welding methods, material consumption is significantly reduced. This is important because the cost of materials makes up a significant part of the cost of the final product.

Even taking into account all the specific features, advantages and disadvantages, the scope of application of EHS is wide. Moreover, thanks to the development of modern equipment, this technology is found even in those areas of production where it had not previously been thought of.

• In heavy engineering, where, thanks to electroslag welding, it is possible to simplify the production of complex foundations and foundations. Previously, the frame of a steam turbine or high-precision machine tool had to be cast and sometimes forged, wasting valuable time on lengthy post-processing, during which a significant part of the material was wasted. Today, such a part can be pre-divided into several parts that are easier to manufacture and process, joining them together using ESW.
• In construction, when it is necessary to reliably splice massive beams of load-bearing structures. Skyscrapers built using this method last a long time.
• In the production of armored vehicles. After all, as noted above, it is electroslag welding that is used for welding thick armor plates that protect the crews and components of combat vehicles. The strength of such a connection is practically no different from a material that has undergone complex processing and can withstand various means of destruction.

The technology, proven over the years, is constantly being improved and it is quite possible that by the time you read this article, it will already reach a new level!

Source: https://ssk2121.com/v-chem-zaklyuchaetsya-suschnost-elektroshlakovoy-svarki/

Electroslag welding, essence of the process and scope of application - Machine tools, welding, metalworking

Electrode welding, which has become widespread due to its relative simplicity, is not always able to ensure stable quality of the weld structure. Meanwhile, in the manufacture of certain types of products this characteristic is important. In order to eliminate the existing technological disadvantage, an electroslag welding technique was developed. It is called ESH for short.

General principles

It is easier to understand the essence of electroslag welding if we consider this process in a simplified form. Everything happens as follows:

• The parts to be joined are installed with a certain gap, the value of which varies depending on the size of the product, the chemical composition of the material and the parameters of the welding current. A chemical called flux is placed in this gap and an electrode is applied to it.
• The current supplied to the electrode passes through flux, the composition of which can be different. As a result of heating, a so-called slag bath is formed, inside which the temperature necessary for melting the metal is maintained. Slag, lighter than metal, is always on top, blocking the flow of atmospheric air to the weld formation zone and increasing the cooling time of the molten metal.
• To keep molten materials from flowing out, the processing area is fenced with water-cooled movable sliders made of copper. In some cases, it is possible to use the enclosing plates remaining on the finished part.

The machines are precise, the armor is strong!

Even taking into account all the specific features, advantages and disadvantages, the scope of application of EHS is wide. Moreover, thanks to the development of modern equipment, this technology is found even in those areas of production where it had not previously been thought of.

• In heavy engineering, where, thanks to electroslag welding, it is possible to simplify the production of complex foundations and foundations. Previously, the frame of a steam turbine or high-precision machine tool had to be cast and sometimes forged, wasting valuable time on lengthy post-processing, during which a significant part of the material was wasted. Today, such a part can be pre-divided into several parts that are easier to manufacture and process, joining them together using ESW.
• In construction, when it is necessary to reliably splice massive beams of load-bearing structures. Skyscrapers built using this method last a long time.
• In the production of armored vehicles. After all, as noted above, it is electroslag welding that is used for welding thick armor plates that protect the crews and components of combat vehicles. The strength of such a connection is practically no different from a material that has undergone complex processing and can withstand various means of destruction.

The technology, proven over the years, is constantly being improved and it is quite possible that by the time you read this article, it will already reach a new level!

Source: https://stanki-info.com/elektroshlakovaya-svarka-suschnost-protsessa-i-oblast-primeneniya/

Electroslag welding, essence of the process and scope of application - Metals, equipment, instructions

The essence of electroslag welding is to heat the parts being joined with the heat generated when current passes through the melted slag. The method is used mainly when working in a vertical plane.

EHS production technology

The process begins by exciting an electric arc between the electrode wire and the part. The arc temperature promotes the melting of the flux, forming a slag pool with an increasing level. The molten flux has sufficient thermal conductivity to shunt the arc, thereby stopping its combustion. At the same time, thanks to the heat released when current passes through the molten slag, the temperature and process of melting the flux are maintained.

In contact with superheated slag, the surfaces of the joined products and the electrode wire melt. The resulting liquid metal fills the gaps between the parts being welded. To keep the flowing metal and slag in the gap, copper sliders are installed on both sides of the seam, which are cooled by water and raised when the joint is ready.

Types of EHS

Electroslag welding is divided into several types, differing from each other in the types of electrodes and methods of feeding them into the bath.

• The first type includes electroslag welding, in which electrode wires are fed into the slag bath as they melt. The method involves imparting reciprocating movements to the electrodes in the horizontal plane, ensuring uniform heating of the thickness of the elements being connected.
• The second type is electroslag welding with plates or electrodes having a large diameter. The diagram assumes that the electrode should close the gap between the parts being welded as much as possible. Plate electrodes, the shape of which corresponds to the surfaces being connected, are fixed in the gap and fed into the slag bath in short periods when there is not enough liquid metal to fill the gap. Equipment for electroslag welding with plates or large electrodes is easier to operate than for wire welding.
• The third method is to use a melting nozzle during the welding process. The first and second types of welding are combined in this technology. That is, the plate is installed and fixed in a gap, the side edges of which, sometimes the central part, are filled with guide tubes through which wire is fed into the slag bath. In this case, the plate remains motionless throughout all welding operations, since the lack of metal when filling the gap is completely provided by the wire, through which the seam is enriched with alloying elements.

Advantages of the method

Connections made by electroslag welding are of high quality. Sometimes, in order to improve the structure of the weld, it is necessary to carry out heat treatment of the joint after welding, which contributes to the enlargement of the grain.

The advantages of the method are:

• low consumption of electrical energy and flux per kilogram of metal;
• process performance.

Also, with the help of electroslag remelting of metal, a significant improvement in its characteristics is achieved.

Disadvantages of the method

Electroslag welding also has a number of disadvantages:

• connections can only be made in a vertical plane, or a slope close to it;
• the process must not be allowed to stop during welding, otherwise you may get defects that will need to be repaired; Often such a connection is broken and welded again;
• the seam and the heat-affected zone have a coarse-grained structure, which is associated with the low impact strength of the metal at negative temperatures;
• first, before starting the welding process, it is necessary to manufacture and install technological parts: strip, starting pocket, forming elements.

Application of EHS

Using electroslag welding, straight, curved, and circumferential welds are made. The smallest thickness of elements connected end-to-end varies from 20 to 35 mm. It is considered more appropriate to use ESW when working with thick-walled materials and structures made of low-carbon, medium-carbon, low-, medium- and high-alloy steels. ESW is also perfect for welding products made of cast iron and non-ferrous metals such as aluminum and titanium.

The method is well suited for making butt, corner, and T-joints with any seam configuration: variable section and curvature, straight and circular shape. Of these, butt welding is considered the most technically simple.

The scope of application of electroslag welding is quite wide, because the method is suitable for welding metal parts of different thicknesses in one pass. A big plus is the fact that increasing the thickness of the elements being connected directly affects the efficiency of the process. Electroslag welding is used for welding cast iron products, surfaces of non-ferrous metals, and for surfacing.

Equipment for EHS

The machines used for electroslag welding are slightly different from other welding devices.

They are equipped with:

• special devices for holding flowing metal and slag in the gap area;
• devices that move the electrode along the weld pool, ensuring uniform heating;
• a power source that ensures the stability of the process and the temperature regime of the slag bath.

Source: https://spb-metalloobrabotka.com/elektroshlakovaya-svarka-suschnost-protsessa-i-oblast-primeneniya/

Electroslag surfacing

Equipment for private production

The technology makes it possible to repair worn parts. It is in demand in various fields of industry: engineering, energy, oil. When repairing road and construction equipment, in metallurgy, when restoring mining machines and mechanisms, rollers, tractor tracks, cast iron rolling rolls and other things.

ESH surfacing is an effective means for repairing large-sized products made of steel, cast iron, non-ferrous alloys, and difficult-to-weld alloys. It is effective for large degrees of wear, more than 10mm.

Compared to argon-arc surfacing, electroslag surfacing allows you to increase productivity by 2.5-5 times and deposit large thicknesses of metal in one pass. It is also possible to additionally introduce alloying elements, or a flux containing them, into the liquid bath to obtain a deposited layer with predictable properties.

For carbon steels, fluxes such as AN-8, AN-47 are used; for alloyed ones - ANF-1, ANF-7; for stainless steel - AN-45; for surfacing cast iron - ANF-14, AN-75.

Workshop version of the ESH installation

Source: http://svarka-master.ru/e-lektroshlakovaya-svarka/

Electroslag welding: what it is, features and principles

Electroslag welding is a popular method for welding steel elements. It is usually used for vertical connection of various structures and workpieces. During it, the melting zone is heated using the heat of the bath, which contains slag. The slag masses are heated by electric current. To carry out this welding technology, special equipment is used.

The concept of EHS

Before you start welding, you should find out what the essence of electroslag welding is. When carrying out this technology, a slag mass is placed in the gap that is formed between the ends of the elements being connected. Its melting is carried out due to the appearance of an electric arc between the electrode and the part.

An additive is added to the molten slag, which immediately begins to melt along with the metal along the edges of the workpieces being joined.

Liquid metal has more weight than molten slag masses; for this reason, it sinks down and displaces slag particles. In the lower region of the gap it gradually solidifies, and the molten masses rise upward. Due to this, a vertical seam is formed. This is the essence of electroslag welding.

Features of electroslag welding

To understand what electroslag welding is, it is worth carefully considering the features of the process. The technology is carried out in several stages:

1. The parts to be connected must be installed with some clearance. Its performance may depend on the dimensions of the product, the chemical basis of the material and the parameters of the current used for welding. Flux is placed in the gap and an electrode is connected to it.
2. A current is supplied to the electrode, which passes through flux having a different composition. During heating, a slag bath is formed, inside which the required temperatures for melting the metal are maintained.
3. Lighter slag masses (slag) are located on top of the metal; they block the penetration of atmospheric air masses into the weld area, and also increase the cooling period of the molten metal mass.
4. To contain the molten metal and prevent it from flowing out, the processing area is fenced with movable sliders, which are made of copper. Sometimes barrier plates may be used.

Important properties

Electroslag welding technology has many positive features and properties that are its advantages.

Among the main qualities it is worth highlighting:

• protection of the connection from exposure to atmospheric air. This function is performed by slag in liquid form;
• changes in current density during the welding process, unlike other welding methods, have little effect on the structure of the joint;
• During the process, there is a low short-term interruption of the current supply;
• You can make connections of any thickness at a time;
• You can weld raw edges of parts;
• there is a small energy consumption;
• low cost of consumables - slag;
• high efficiency is observed.

Important! During electroslag welding, not direct current is used, as with many other welding methods, but alternating current.

Negative features

It is worth remembering that ESW technology has negative qualities; welding allows only vertical welded joints or seams at an acute angle to the vertical. This is the main reason for the low prevalence of this method.

The welding process, which has already begun, cannot be stopped in the middle, otherwise defects and inaccuracies may occur. They can be eliminated only by completely tearing the seam and performing welding work again. The metal of the connection has a coarse-grained structure. For this reason, workpieces with this compound are not recommended for use at subzero temperatures; their base becomes brittle and brittle.

Note! The electroslag welding process requires the use of a large amount of equipment. During this process, copper sliders are often used, which are pressed tightly against the joint area, as well as other auxiliary parts.

Conclusion

Electroslag welding is a reliable method for welding various metal workpieces. This method is used in large industries to connect huge structures of special importance. But still, before starting the technology, it is important to study its main features and qualities.

Interesting video

Source: https://osvarka.com/vidy-i-sposoby-svarki/elektroshlakovaya-svarka

What is electroslag welding?

There are many small industries where there are few welders, but at the same time the company produces quite high-quality products, and even in large quantities. How do they achieve this? It's simple: there are welding technologies that are characterized by increased productivity and efficiency, which allows them to be used in production of any scale.

One of these technologies is electroslag welding, also known as ESW. From this article you will learn the essence of electroslag welding, its pros and cons. We will also tell you what equipment and consumables are used for ESW welding.

general information

ESW or electroslag welding is a method of joining metals in which heat that melts the metal is generated in a molten slag environment. The electrode is immersed in the slag, passing an electric current, which thereby generates heat in the slag. This process does not require the use of an arc. ESW is often used when welding vertically located parts, the seam is made from the bottom up.

Varieties

There are several methods of electroslag welding, you can see them all in the picture below. Method “a” is ESW welding using one stationary electrode or with slight vibrations. Method “b” is welding using two electrodes that perform oscillating movements. Method “c” is welding using plate electrodes. Method "d" - welding using a melting nozzle.

All these methods have their own characteristics, advantages and disadvantages, so in this short article we will not talk about all types of ESW welding. Let's just say that the most popular method is using one, or less often two, electrodes, which can be stationary or perform oscillatory movements.

Technology

Electroslag welding technology is extremely simple. The two parts are installed vertically, leaving a small gap between them. The gap must be closed on both sides with sliders equipped with tubes with water for cooling. The sliders must be moved during welding so that the seam cools evenly. The gap at the bottom must be additionally closed with a special “pocket”. Then you need to pour flux into the gap and immerse the electrode in it. The current is supplied using a mouthpiece.

The current passes through the electrode directly into the flux, and it begins to melt. Subsequently, slag is formed, which, due to its high thermal conductivity, is precisely the source of heat that heats the metal. The slag melts the electrode and edges and contributes to the formation of a weld pool.

There is no arc in this process, as such. Flux protects the welded joint from the negative effects of oxygen and improves its quality characteristics. At the same time, it is used quite economically and its consumption is low. You can use regular arc welding flux or a special flux.

But we'll talk about this later.

Equipment and materials used

Equipment for electroslag welding is inexpensive and consists of a welding machine and devices that perform auxiliary functions. Usually equipment for EHS is sold as a set, which is very convenient. This kit is called a welding installation for electroslag welding. This is perhaps all that can be said about the equipment used.

But with fluxes everything is much more interesting. For ESW it is necessary to use fused fluxes. If you are going to weld carbon or low-alloy steel, then we recommend using fluxes AN-8, AN-8M, AN-22. We also make a special mention of AN-47 flux; when used, the seams are of high quality, and the welding process is always stable.

If you have to weld alloy steel with increased strength, then it is better to use AN-9 flux. Fluxes ANF-1, ANF-7, 48-OF-6 are excellent for welding high-alloy steel. Don’t forget about AN-45 flux; it can be used to weld steel with anti-corrosion properties very well. If you need to weld cast iron, we recommend ANF-14 and AN-75 fluxes.

You can use other fluxes if you see fit, but keep in mind that they must meet the following requirements:

• Perform its functions at any value of welding current or voltage, and also install the ESW process without any problems.
• Sufficiently melt the edges of parts and help improve the quality of the seam, without forming undercuts or sagging, cracks, inclusions and other defects.
• The flux you choose should not flow through the gap between the parts.
• The flux should form a slag, which can then be easily removed from the metal.

Before welding, the flux must be calcined in a furnace. Warm-up temperature can vary from 300 to 700 degrees Celsius. The temperature depends on the type of flux and is selected individually, but in any case, the calcination time should not exceed two hours.

Advantages and disadvantages

Electroslag welding has many advantages. Firstly, the welding itself is extremely stable under any type of current. In addition, it is little sensitive to any current changes or even short-term interruptions. You don't even need to be highly qualified to make a quality seam.

Secondly, such welding provides very high labor productivity. This can be achieved due to the rapid melting of the electrode. And if the welder has experience, then ESW welding will be completely unrivaled. Even a small plant will be able to produce large quantities of a variety of products.

Thirdly, electroslag welding is extremely economical. Flux is consumed little (15 times less than with classic arc welding), and electricity is also consumed (10-20% less than with arc welding). In addition, the equipment and consumables used are inexpensive. For small businesses this is a very important plus.

Fourthly, there is no need to prepare the metal edges in a special way and process them efficiently. These are the main advantages. We also note that with ESW, the weld pool is well protected from oxygen.

But it’s not without its shortcomings, although we don’t consider them that significant. First of all, with the help of ESW you can only weld parts located vertically or at a slight angle (deviation no more than 30 degrees). This significantly narrows the welder’s capabilities and makes hard-to-reach welding, for example, impossible.

There is also no option to leave welding, say, in the middle of the process, and continue it later. You cannot cook at sub-zero temperatures, otherwise the seam will be defective. Don't forget that although you won't have to prepare the edges, you will still spend time making the pocket, strips, etc.

Instead of a conclusion

We tried to briefly but clearly describe what electroslag welding is. Using this article, you will be able to apply this technology in your practice, since you now know all the brands of flux and the features of welding.

We believe that ESW welding is simply irreplaceable in small enterprises, because it is economical, productive and allows the production of relatively high-quality products. Have you ever resorted to electroslag welding? Tell us about your experience in the comments.

We wish you good luck in your work!

Source: https://svarkaed.ru/svarka/vidy-i-sposoby-svarki/chto-takoe-elektroshlakovaya-svarka.html