RU2166842C1 - Consumable electrode - Google Patents

Abstract

FIELD: vacuum arc furnaces. SUBSTANCE: transfer part of consumable electrode is cylindrical or stepped in shape which eliminates flaw areas in electrode for secondary and next remelting and prevents accumulation of flaws on electrode surface. EFFECT: improved reliability of electrode. 4 cl, 11 dwg

Description

 The invention relates to electrothermal, in particular to the structural elements of electric furnaces, and can be used in vacuum arc remelting of highly reactive non-ferrous metals, their alloys and steels.

 Known consumable electrode, which is an ingot of the first remelting, consisting of a consumable cylindrical part (Titanium alloys. Melting and casting of titanium alloys / Andreev A.L., Anoshkin N.F., Bochvar G.A. et al. - M.: Metallurgy 1994, p. 196, fig. 71).

 When remelting a known consumable electrode, it is welded to a cinder previously fixed in the furnace to the electrode holder, or to an adapter welded to the cinder. The welding zone is characterized by chemical heterogeneity with the base metal and is a source of contamination of the smelted ingot.

 The operation of welding this electrode to a consumable adapter or a cinder is accompanied by heating the welded surfaces with an arc, splashing and spraying the metal on the inner surfaces of the melting chamber and dropping drops into the mold, contacting the welded surfaces with each other with squeezing the liquid metal into the peripheral zone and the formation of significant leaks, the composition which differs from the composition of the base metal.

 Each time, the furnace is specially evacuated for welding, which is carried out due to the personal skills of the smelter, and then opened for inspection. If the quality of the welding, according to the controller, is considered insufficiently reliable, then the molten electrode is forced to melt at reduced current conditions or the electrode together with the welded cinder is unloaded from the furnace to eliminate defects and retrain. In practice, during smelting, electrode breaks occur at the place of welding, i.e. accident.

 In order to avoid the penetration of defective metal from the weld zone into the ingot, the smelters underfill the last part of the electrode, in practice, 50-100 mm high, which results in a significant decrease in the yield of metal and does not guarantee the purity of the smelted ingot, since during melting on the side and end surfaces of the electrode, the adapter and the cinder accumulate condensate, the kings of the hardened metal and growths, which, when the furnace, electrode holder and alloy electrode shake, fall into the melt. In the future, these chemically heterogeneous inclusions are found in ingots, in the final products of aviation and other equipment and are potential sources of destruction of products during their operation.

 After unloading the ingot from the furnace, a special mold “bowl” is installed in it, into which the remainder (“pancake”) of the electrode is fused, and the resulting float contaminated with the welding zone is sent to waste for recycling. They are used for the production of ferrotitanium, since the involvement of these substandard waste in the mixture impairs the quality of the ingots.

 The task to which the claimed invention is directed is the development of a cast consumable electrode, subsequent remelting of which excludes the possibility of the formation of refractory gas-saturated inclusions in the finished ingot while increasing the yield of metal.

 The technical result achieved by the implementation of the invention is both the absence of defective, contaminated, chemically inhomogeneous zones initially in the consumable electrode itself, and the prevention of the accumulation of defective formations on the surface of the electrode during its remelting.

 The specified technical result is achieved by the fact that in the consumable electrode for the secondary and subsequent remelts, including a cylindrical body, in accordance with the invention, the upper end of the body is made in the form of a cinder consisting of a shank and a transitional part. In this case, the contact zones of all elements of the electrode (cylindrical body, transitional part and shank) are made monolithic: cast or fused.

 The transitional part of the cinder can be made conical or cylindrical (including step).

 A removable casing of various shapes can be freely put on the transitional part and / or the end face of the electrode body. In this case, the removable casing may have an additional wall forming a storage tank for contamination.

 When performing the transitional part of the cylindrical on the upper end girdle of the electrode body, a recess can be made forming a storage tank for contamination.

 The transitional part of the cinder can be made buried in the cylindrical body of the electrode.

 The implementation of the upper part of the consumable electrode, which is a monolithic ingot of the first remelting, in the form of a cinder, consisting of a shank and a transitional part, allows you to fix the electrode on the electrode holder of the furnace of the second remelting without intermediary devices and preparatory welded operations.

 The implementation of the contact zones of all elements of the electrode (cylindrical body and transitional part, transitional part and shank) monolithic: cast or fused (in skull, plasma, electron-beam or vacuum arc furnaces) ensures the absence of a defective metal in the consumable electrode and thus prevents contamination of the smelted ingot by extraneous chemically heterogeneous inclusions.

 When performing the transitional part of the conical-shaped cinder, metal condensate and hardened kings do not accumulate on the electrode, but roll into the molten ingot molten metal bath and have time to melt.

 Remelting of such an electrode can be performed as usual, with underfusion of a certain height of the cylindrical body, and until the cylindrical body is completely melted or even before the small height of the transitional conical part is fused to a certain diameter.

 The implementation of the transitional part of the cinder of cylindrical shape due to existing technology and the existing fleet of equipment. The stepped transitional part of a cylindrical shape is convenient for fixing and grooving the remainder of the consumable part of the cylindrical body before depositing the next ingot electrode on it. When remelting electrodes with a cylindrical transitional part, a part of the cylindrical body is left unfinished, which is then grinded for reuse.

 A removable casing protects the surface of the transitional part of the cinder, as well as the end surface of the electrode body in the case of the transitional part of the cylindrical shape, from hardening condensate and allows reuse of the unfused cinder without intermediate cleaning.

 The storage tank, made on a removable casing, plays the role of an additional trap for contamination.

 At the final stage of melting with increasing luminescence of the annular outer edge around a relatively cold and dark protective casing, conditions for visual control and timely shutdown of the furnace are improved.

 Thus, during remelting of the claimed consumable electrode, high quality and chemical uniformity of the obtained ingot of the second remelting is ensured and the yield of metal is also increased.

 The remaining upper part of the electrode, including the shank and the transitional part, is essentially a chemically clean revolving element, the so-called "revolving cinder", intended for repeated use.

 In one case, the “back-burner" is laid with the shank down in a pallet of the corresponding design of the mold of the vacuum arc furnace, the pressed consumable electrode is melted onto it and the monolithic cast consumable electrode (ingot of the first remelting) of the declared form is again melted, with the shank for the electrode holder of the second remelting furnace.

 Repeated use of the "reverse cinder" when repeating remelts twice or more times increases the chemical uniformity and microstructure of complex alloyed steel ingots and non-ferrous alloys.

 In another case (for example, during skull melting), a “turn cinder" with a cylindrical transitional part is laid with the shank down in a pallet of the corresponding design, while the transitional part can protrude from the pallet, and is poured with molten metal, realizing the variant when the cylindrical transitional part is buried in the body of the electrode, receiving the claimed monolithic cast consumable electrode with a shank for the second remelting furnace.

 The “reverse cinder” is otherwise loaded as a whole into the crucible of the skull furnace with the next charge, it is melted, the molten metal is poured into the mold with a tray of the corresponding design and the claimed monolithic cast consumable electrode with a shank for the electrode holder of the second-vacuum vacuum arc furnace is obtained.

 Small-sized consumable electrodes of the claimed form are fully adapted for melting by the VADER (vacuum are double-electrode remelting) method with repeated use of “reverse cinders”.

 In addition, consumable electrodes of the claimed form can be used in electron beam and plasma remelting.

 In the extreme case, the “cinder” can be used as a conventional cinder, that is, serve for welding a pressed electrode and use it by known technology in first remelting furnaces.

 The invention is illustrated by drawings, where in FIG. 1 shows a consumable electrode for secondary and subsequent remelting with a conical transitional part of the cinder; in FIG. 2 - electrode with a cylindrical transitional part of the cinder; in FIG. 3, 7, 8 - removable casings of various shapes, freely put on the electrode; in FIG. 4, 9 - removable casings with storage capacity; in FIG. 5 - electrode with a storage capacitance made on the end girdle of the electrode body; in FIG. 6 - electrode with a stepped transitional cylindrical part of the cinder; in FIG. 10 - deepening of the cylindrical transitional part of the cinder; in FIG. 11 - node mounting the electrode on the electrode holder of the remelting furnace.

 The monolithic consumable electrode includes a cylindrical body 1, a transitional part 2 of a conical or cylindrical shape, a shank 4. A removable casing 5 can be installed on the surface of the electrode, in which a storage tank 6 can be made. The consumable electrode can have a storage tank 7 on the end girdle.

 Example 1

 A consumable electrode was obtained on a DTVG-4PF-I1 model skull furnace in the process of filling a mold with a diameter of 650 mm overheated with liquid metal, the pan of which provides the formation of a conical transitional part and a liner.

 In the next operation — the second remelting — the finished electrode ⌀ 640 mm was fastened to the shank on the electrode holder of the DTV 8.7-G10 vacuum arc furnace, the furnace was evacuated, and melting was carried out using the technology used. The process was conducted in helium. The melting was completed at the stage of the beginning of melting of the conical transitional part and an ingot of 70 870 mm was obtained.

 After unloading the ingot and cinder, the last one was loaded with the next charge into the crucible of the DTVG-4PF-I1 skull furnace, the molten metal was melted and poured into a mold ⌀ 650 mm, therefore, we obtained another cast consumable electrode ⌀ 640 mm, weighing 4 tons.

 Example 2

 A consumable electrode with a casing loosely worn on the transitional conical part was secured to the shank on the electrode holder of the vacuum arc furnace, melted according to known technology. Melting was completed at the stage of fusion of the cylindrical body of the electrode.

 After unloading the ingot and the “reverse cinder”, the latter was freed from the casing, stripped and installed with a shank down into the special working cavity of the mold tray ⌀ 650 mm of the DTV 8.7-G10 vacuum arc furnace. A pressed consumable electrode ⌀ 560 mm was melted into a “reverse cinder” and a monolithic cast consumable electrode ⌀ 640 mm of the first remelting with a conical transitional part and a shank for the electrode holder of the second remelting furnace was obtained.

 Thus, the claimed consumable electrode, chemically pure from impurities and having the described shape, provides high quality and chemical uniformity of the ingot of the second and subsequent remelts.

 When re-using the “cinder” in vacuum arc furnaces, the smelted ingot is contaminated with copper pan.

 The high quality of the ingots of the first remelting (declared consumable electrode) and, accordingly, of the second remelting with repeated or repeated use of the “reverse cinder” of the cast consumable electrode increase the yield of metal.

 When the need to use a “reverse cinder” in vacuum arc furnaces ceases, it is used for remelting in the skull furnace, and is not rejected, which also increases the yield.

 In addition to improving the quality of smelted ingots and the yield of metal, the claimed consumable electrode provides high-performance operation of vacuum arc furnaces, reducing environmental pollution, increasing the service life of oven trays.

 In addition, the use of the claimed consumable electrode eliminates the risk of emergency situations during its remelting.

Claims (4)

 1. Consumable electrode for secondary and subsequent remelting, containing a cylindrical body, a transitional part and a shank with cast or fused contact zones between them, characterized in that the transitional part is made cylindrical or stepped.  2. The consumable electrode according to claim 1, characterized in that on the upper end zone of the cylindrical body there is a recess forming a storage tank.  3. Consumable electrode according to claim 1, characterized in that the transitional part is made buried in the body of the electrode.  4. The consumable electrode according to claim 1, characterized in that when equipped with a removable casing, the casing contains an additional wall forming a storage tank.

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