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.
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| 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
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| 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.
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| 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.
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| 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:
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