Electroslag Welding Technique

Electroslag Welding Technique

Electroslag Welding technique. Electroslag process proceeds steadily at current densities of about 0.1 A / mm 2 (in arc welding, the order of 20-30 A / mm 2 ). Therefore possible to replace the wire electrodes on the plate or strip electrodes. However, if you can not use the feeder plate electrodes (lack of space on the product, etc.) and welding products of complex cross section (plate electrode should be fixed) to compensate for the lack of metal to fill the space between the electrodes and the electrodes and the edges of the base metal using consumable welding method mouthpiece. In this case, the electrode plate shape can repeat the form of welded edges and be part of.

Current lead wire to the electrode via a sliding contact with the melt plate electrode (mouthpiece). When contact-slag welding rods of different cross-sectional After formation of the desired metal bath come off the welding current and sediment of the upper rod. This method can be welded to the flat surface of the rods.

The stability of the electroslag process, the shape of the weld and base metal penetration depth depends on the parameters of welding. The main parameters are: welding speed V, the welding current I St. , feed rate of the electrode V p , welding voltage U C in the thickness of the metal, per one electrode, the electrode spacing z. Auxiliary components of the regime: the gap between the edges b, of the flux, the depth of the slag bath h w B, the speed of reciprocating movement of the electrode, its "dry" crash L z , the cross section of electrodes, etc. The depth of the slag bath, depending on the strength of the welding current varies from 25 to 70 mm. The speed of the reciprocating movement of the electrode of 25-40 m / h Sukhoi crash electrode 60-80 mm.

With increasing current strength increases the rate of melting of the electrode and increases the depth of the metal bath h w B. The joint width varies slightly. With the increase of the electrode feed rate v pr (typically 100-500 m / h), the electrode is immersed in the slag bath in more depth. This reduces the welding voltage U St , metal bath depth h m B and the width of the joint b w . Ratio of weld shape (shape metal bath) decreases with increasing current and podvyshaetsya with increasing diameter of the electrode and the welding voltage.

The number of electrode wires, their diameter and the cross section of plate electrodes or melting mouthpieces, the speed of delivery and other parameters are chosen so as to get the speed and welding voltage to ensure stability of the process and the required size and shape of the seam.

Application of electroslag welding makes fundamental changes in production technology of large-sized products. It is possible to replace the large cast or forged details of welded-cast or welded-forged from smaller forgings or castings.

Preparations for welding should be collected, taking into account shrinkage of the joint after welding. Slides for a snug fit and forming devices to smooth out the edges of the last joint of the burrs, scale, and so the width to 100 mm. To display the outside seam shrinkage cavity at the end of the seam set off, and the withdrawal of fusions at the beginning of the seam - the input bar, which is removed after welding cutting. To begin welding in a pocket formed by the input bars, poured flux that melts the welding arc to obtain the required size of the slag bath. After this arc is shunted by the slag, and the process goes - electroslag.

Before you start welding slag can be poured, melted in a special mold. For guidance electroslag bath you can use special fluxes, electrically conductive solid state. Original process of welding of circular joints. Welding start on the front plate. During further rotation of welding products in the early part of the defective weld seam to close the cut. With the closure of the joint rotation of the product stops and starts moving the welding set up as in the usual straight seam welding. The closure of the suture and the withdrawal of shrinkage cavity is carried out with a special pocket of the wafers or die.

See also:
Electroslag Welding Technology
Electroslag Welding
Electroslag Welding Technique

Electroslag Welding

all about electroslag welding

Electroslag welding is widely used for metal compounds increased thicknesses of steel and iron of different composition, copper, aluminum, titanium and their alloys. The advantages of method is the possibility of a single pass welding of virtually any thickness of metal that does not require the removal of slag and appropriate adjustment of welding installation before welding the subsequent passage, as in other methods of welding. At the same time carry out welding without bevelling on the edges. For welding can use one or more wire electrodes or other electrodes enlarged cross-section. As a result, achieved high productivity and efficiency of the process increases with the thickness of the base metal.

Disadvantages include ways that the electro-slag welding is technically possible with the metal thickness exceeding 16 mm and with rare exceptions, is economically beneficial when welding metal thickness exceeding 40 mm. The method allows only vertical weld seams. When welding of certain metals in the formation of the weld metal and heat affected zone of unfavorable structures requires subsequent heat treatment to obtain the required properties of welded joints.

Electroslag Welding Technology. It is known that molten fluxes form slag, which are conductors of electricity. At the same time in the volume of the molten slag in the flow of the heat of the welding current is allocated. This principle underlies the electroslag welding. Electrode and the base metal is electrically connected through the molten slag (slag bath). Released in the heat of the slag bath overheats it above the melting temperature of the ground and the electrode metal. Used by the metal electrode and the edge of the base metal and fused because of the greater density of the metal than the slag flow down to the bottom of the melt, forming a molten metal bath. electrode metal in the form of individual droplets passing through the liquid slag, interacts with it, thus changing its composition. Slag bath, while the surface of molten metal, preventing its interaction with the air. When properly selected feed rate of the electrode gap between the end of the electrode and the surface of the metal bath is kept constant. welded metal, slag and metal bath kept from flowing normally forming a special device - mobile or fixed copper sliders 5, 6 water-cooled, and the remaining plates. The upper edge of the slide is slightly above the slag bath mirrors. Crystallizing in the bottom of the metal forms a molten metal bath seam 7. Slag bath, while the surface of the metal bath, cooled by contact with the sliders, which forms a thin crust of slag, thereby eliminating direct contact with the surface of the molten metal cooled slide and preventing the formation of the weld metal solidification cracking. consumption flux by this method of welding is small and usually does not exceed 5% by weight of weld metal. Due to the small amount of slag deposited metal doping is mainly due to the electrode wire. The share of the base metal in the weld can be reduced to 10-20%. The vertical position of the metal bath, fever, and the upper part of the large residence time of metal in the molten state, contribute to improving the conditions of removal of gases and nonmetallic inclusions in the weld metal. Compared with arc welding slag bath - less concentrated heat source. Therefore, the thermal cycle of electroslag welding is characterized by slow heating and cooling of the base metal. The deviation of the axis of the welded seam of the vertical may not be more than 15 ° in the plane of a sheet of bone and 30-45 ° from the horizontal. Since the release of heat in the slag bath is I mainly in the area of the electrode, the maximum thickness of the base metal, weld using a single electrode wire is usually limited to 60 mm. When welding thicker metal electrode in the gap between the edges of the com-schayut reciprocating (up to 150 mm) or use multiple fixed or movable electrodes. In this case, it is possible to weld metal of arbitrarily large thickness.

See also:
Electroslag Welding Technology
Electroslag Welding
Electroslag Welding Technique

Fluxes For Electroslag Welding

Depending on the chemical composition of the fluxes for electroslag welding are the following types:

• high-silicon manganese - AN-348, FC-7, etc.;
• nizkokremnistye Manganese - AN-8, AN-22, FC-21, etc.;
• nizkokremnistye bezmargantsevye - AN-9, AN-25 and others;
• fluoride - ANF-5-14 ANF, ANF-R, etc.

In addition to the requirements for reliable protection of molten metal, the optimum metallurgical and chemical interactions, and provide the necessary mechanical properties of welded joints in flux for electroslag welding process is presented and a number of requirements:

• ensure a stable flow of the electroslag process;
• seal the cavity, and welding slag bath and prevent leakage into the gap between the product and sliders, sliders do not wring;
• provide easy separation of the slag crust on the surface of the weld.

These requirements are most important and provided, above all, an appropriate choice of values ​​of electrical conductivity and viscosity of the flux.

In electroslag welding heat is not an arc, and the slag bath by passing current through it. Therefore, the stability of the process is determined not by the presence of elements with low ionization potential, as in arc welding, and electrical conductivity of flux. The higher (up to a certain level), the electrical conductivity of the liquid flux, the more stable the process of electroslag welding. However, excessively high values ​​of electrical conductivity of flux (eg, ceramic, containing a significant amount of ferro-alloys) reduces heat in the slag bath, which can lead to the formation of fusions.

The graph below shows that the highest electrical conductivity have fluoride fluxes. They provide the best stability of the electroslag welding process, but have limited use (for example, for welding high-alloy austenitic steels) because of the need for low voltage welding, making it difficult to obtain the required penetration edges.

At the same time should be optimal and the viscosity of the molten flux. On the one hand, it should not be too flowable so as not to flow into the gap between the product and moving the slider. On the other hand, the high viscosity of the molten flux and its rapid solidification at low temperatures can occur from squeezing sliders welded edges and undercuts may appear at the surface of the weld and slag inclusions. Therefore, in terms of the requirements necessary to select a flux is not very "short" slag, ie, the viscosity of which varies slowly with decreasing temperature. At the same fluoride fluxes (eg, ANF-P) are the worst because they have a "short" slag (from the rapid increase in viscosity at low temperatures).

Separability of the slag crust depends on the thickness of the oxide film on the surface of the weld metal and, mainly, of the content in the flux of manganese oxides Mn 2 O 3 and MnO. The smaller the number in the flux, the better the separability of the slag crust.

To start the electroslag process can be used flux AN-25. It is electrically conductive, even in the solid state in contrast to many other fluxes designed for electroslag welding. In the absence of flux AN-25 can start with an arc welding process, which stops after filling the flux and its melting and electroslag goes into the process as a result of shunting arc melted conductive flux ("solid" start). Often used "liquid" start when poured molten flux previously.

Welding fluxes are used as special (AN-8, AN-8M, EN-22, etc.) and some of the fluxes for arc welding, electroslag suitable for the process (AN-348A, ANF-1, FC-7, 48 - PF-6, etc.). As with arc welding, the more alloyed steel, the more fluoride CaF 2 and less oxides MnO and SiO 2 must be contained in the flux.

When welding carbon and low alloy steels fluxes AN-8, AN-8M, EN-22, a 48-RP-6 is preferred over flux FC-7 and AN-348-A. Last less suitable for welding with high wire feed speed and welding seams extended. Fluxes AN-22, and 48-RP-6, in addition, a better help to reduce the sulfur content in the weld. When welding carbon steels, and the positive results achieved with the use of flux AN-47 and AN-348-B.

For medium-and high-alloy steels used fluxes 48-RP-6-1 ANF, ANF-7, etc. When welding stainless steels can be applied fluxes marks the 48-RP-6-6 ANF, ANF-7, ANF-8, ANF-14, a heat-resistant steels - Fluxes ANF-7-8 ANF, ANF-R, AN-292, etc. For high-strength alloy steels (20H2M, 25HNZMFA, etc.) can be used flux AN-9.

Electroslag welding and surfacing of cast iron can be performed using flux AN-75, ANF-14. For welding of titanium using flux brands ANT-2 ANT-4, etc., for aluminum - fluxes AN-A301, A302 and AN-al

Consumption of flux for electroslag welding of about 10-20 times less than in arc welding.

Flux	A typical field of application
AN-8	carbon and low alloy steels
АN-22	low-and medium-steel
АN-348-А АN-348-В	carbon low-alloy steel
FC-7	low-carbon and carbon steels
FC-21	heat-resistant pearlitic steel
48-PF-6	different types of steels (low and high, carbon, etc.)
АNF-1	high-alloy steels

See also:
electroslag welding technology
submerged arc welding technology

Welding materials:

welding electrodes welding wire welding flux for arc welding carbon dioxide helium

argon protective gas mixture acetylene propane-butane IAF

Electroslag Welding

Common designations of electroslag welding
ESW - electroslag welding (mainly in the Soviet literature) ESW - Electroslag Welding - electroslag welding

The technology of electroslag welding
In electroslag welding of heat needed to melt the metal to be welded, is formed by passing an electric current through molten slag consisting of oxides, halides, or mixtures thereof.

Electroslag welding

Two welded parts are mounted vertically with a gap between the edges. The gap is closed on both sides of the copper water-cooled slides. The bottom gap also closes a special pocket. In the gap is filled welding flux and welding wire is lowered. In the process of welding wire is fed down the rollers, current lead is a mouthpiece. Due to the passage of current between the wire and the workpiece is heated and melted flux. The molten flux forms slag, which, being electrically conductive and is a source of heat, leading to melting of the wire and the edges and the formation of the weld pool. The arc is not present, since it is shunted by the molten slag. The welding process is bottom up. Slides, a water-cooled tubes, moved up along with the welding machine to form a weld. The molten flux at the same time provides protection for the weld pool and is involved in metallurgical processes, ensuring the required quality of the weld.

Consumption of flux with this method of welding is small and does not exceed 5% the mass of deposited metal. The flux used is the same as for arc welding, or special.

Varieties of electroslag welding
The main varieties are the electroslag welding

• multiple electrode electroslag welding,
• electroslag welding of plate electrodes,
• electroslag welding consumable mouthpiece.

Since the release of heat in the slag bath is mainly in the area of the electrode, the maximum thickness of the metal, welded wire, one is usually limited to 60 mm. At large thicknesses, it is advisable to use multiple wires - usually a multiple of three - the number of phases of the power supply. If necessary, the wires attached to variations across the gap for a better fill. Welding current per wire is I St = 200-600A, welding voltage - 26-44V, wire feed speed - V n = 100-400 m / h

Multiple electrode electroslag welding

Electroslag process proceeds steadily at current densities on the order of magnitude lower than the arc - about 0.1 A / mm 2 . Therefore, the cross section of the electrode can be increased and the wire is replaced by a plate electrode, which improves the performance of the welding process.

Electroslag welding electrode plate

In a complex product configuration can be welding consumable mouthpiece, which is a plate electrode, echoing the shape of the welded edges.

Electroslag welding consumable mouthpiece

As the mouthpiece between the consumable product, and there is a gap to fill it further into the molten pool is fed through the die wire.

Areas of application of electroslag welding
The main advantage of electroslag welding is the ability to weld in one pass details of almost any thickness. Welding is done without cutting edges, so its efficiency increases with increasing thickness of the base metal. Economically feasible to apply it starting from 40 mm, but most often it is used for welding thicknesses of 100-500 mm.

Electroslag welding is used in the manufacture of solid frames, shaft power turbines, boilers and thick drums. Its application makes fundamental changes in the technology of large-sized products. It is possible to replace the large cast or forged parts welded, cast or welded-forged from smaller forgings or castings.

The disadvantages of electroslag welding is a high heat-affected zone due to the slow heating and cooling of the metal. This often leads to negative, coarse-grained structures and require heat treatment to obtain the required properties of the weld.

Welding technology:

manual arc welding semi-automatic welding argon arc welding machine welding electroslag welding plasma welding laser welding electron beam welding

gas welding resistance welding spot welding seam welding projection welding butt welding welding underwater welding in space