RU2425158C2 - Vacuum arc furnace - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: at least two recesses of spherical or conic shape forming cast cavities are made in bottom of furnace. The cavities are designed to be filled with melted metal produced at melting residue of consumable electrode and for fabrication of cast work-pieces out of it. Also, summary volume of the said cast cavities is chosen from the condition of their filling with liquid metal without formation of bridges between the said cast cavities. Ingots up to 1 kg are used for electrode pressing for vacuum arc melting and ingots over 1 kg are used for re-melting in scull furnaces.

EFFECT: melting residue of electrode into cast ingots, eliminating operation for re-make of ingots of 5-60 mm height into lump, for further utilisation at pressing or at re-melting in scull furnaces due to casting ingots of various weight.

3 cl, 2 dwg

Description

The invention relates to the field of electrothermics, in particular, to designs of vacuum arc furnaces for melting titanium waste.

A vacuum arc furnace is known in which a consumable electrode is fused, which is an ingot of the first remelting, consisting of a consumable cylindrical part. 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. (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.)

The welding zone is characterized by chemical heterogeneity with the base metal and is a source of contamination of the smelted ingot. In order to avoid the entry of a defective metal from the weld zone into the ingot, the swimmers do not melt the last part of the electrode (pancake), in practice, with a height of 50-100 mm, which results in a significant decrease in metal yield. 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. The obtained ingot ("float"), contaminated with the welding zone, is used for the production of ferrotitanium. If we allow the participation of this ingot in secondary charge materials uniformly distributed over the entire volume of the charge, it is necessary to use fire cutting, heating, forging, shot peening, etching, which is a time-consuming operation, and also contributes to the ingress of oxides and nitrides into the charge materials, which creates prerequisites for smelting defective ingots.

A known vacuum furnace containing a vacuum chamber, a mold, an electrode holder, a consumable electrode and a copper tray. (RF patent No. 2152141, Н05В 7/18, publ. 2000.06.27) - prototype.

The disadvantages of the existing furnace are that when the remainder of the electrode is melted, an ingot (“float”) of 5-60 mm thickness is obtained, which does not subsequently participate in redistribution into secondary charge materials (a piece) and goes on to obtain ferrotitanium.

The problem to which the invention is directed is to reduce the laboriousness of the processing of flavors by eliminating operations (fire cutting, forging, etching, etc.) of further processing them into a piece; improving the quality of the charge materials by eliminating the ingress of oxides and nitrides into the charge materials by eliminating the operation of fire cutting, increasing the yield due to the additional use of FeTi as charge materials.

The technical result achieved by the implementation of the present invention is as follows: fusion of the remainder of the electrode into cast billets, bypassing the operations of converting ingots 5-60 mm high into a piece for their further use in pressing and / or during remelting on skull furnaces by casting billets different masses. Castings up to 1 kg - for involvement in the pressing of electrodes for vacuum arc melting, over - for remelting on skull furnaces.

The specified technical result is achieved by the fact that in the proposed vacuum arc furnace, comprising an electrode holder with a consumable electrode, a vacuum chamber, a mold and a copper pan, at least two recesses of a spherical or conical shape are made in the pan, forming casting cavities intended to fill them molten metal obtained by reflowing the remainder of the consumable electrode and making cast billets from it, while the total volume of said casting cavities is selected from the condition I fill them with liquid metal without forming jumpers between the mentioned casting planes.

The recesses are made of various volumes, the surface of the recesses is covered with a neutral flux based on CaF ₂ .

The fill factor is determined empirically (experimentally) in such a way that the liquid metal flows in the cavity without the formation of jumpers between the cast billets, the entire remaining electrode is used to make cast billets for further use as charge materials.

The location of the casting cavities of various volumes is determined empirically, but taking into account that in the central part of the pallet (bowl), blanks of maximum weight are cast, it is filled with molten metal in the first place. They are located randomly (over the entire area of the bowl), of various diameters and depths.

To prevent sticking of liquid metal during fusion of the remainder of the consumable electrode (pressed or cast), the surface of the recesses is additionally covered with a neutral flux dust film.

The feasibility of the invention is confirmed by a specific example.

Figure 1 shows a flat pallet 1 with recesses 2 of various shapes and depths.

Figure 2 shows a flat pallet with recesses of various shapes and depths, but the pallet has a concave surface with a neutral flux along the periphery of the pallet or "copper bowl" specifically designed for this operation.

The furnace operates as follows.

After fusion of the consumable electrode according to existing technology, the remainder of the electrode is melted onto a pallet (bowl), on which there are 2 recesses with a diameter of 150 mm, a depth of 120 mm, 1 recess with a diameter of 120 mm, a depth of 100 mm, 15 recesses with a diameter of 80 mm, a depth of 60 mm, the remaining recesses, evenly around the circumference, with a diameter of 45 mm, a depth of 30 mm in the form of a hemisphere or cone. To increase the mass of lumpy waste obtained on a pallet with a diameter of 1200 mm, we place a template with a thickness of 5-25 mm (the thickness is not uniform in diameter), with a diameter of 1000 mm.

The furnace is evacuated, the power supply is turned on at the reverse polarity. The cathode is a template mounted on a pallet (thicket) with recesses.

At 25 kA, the template is heated at the opposite polarity and melted. Liquid metal from the template flows into the recesses, after which metal additionally flows from the remainder of the consumable electrode. Lump waste with a total mass of 50 kg (from 0.5 kg to 5 kg) was smelted.

The lumpy waste obtained by fusing the remainder of the electrode cools down for 60 minutes. The furnace is opened and molten lump waste is removed from the recess.

The proposed vacuum arc furnace allows you to draw the metal in the "float" into the charge for smelting commodity titanium ingots, which increases the yield by 1-4%.

Claims (3)

1. A vacuum arc furnace, comprising an electrode holder with a consumable electrode, a vacuum chamber, a mold and a copper pan, characterized in that at least two spherical or conical recesses are formed in the pan, forming casting cavities intended to be filled with molten metal, obtained by melting the remainder of the consumable electrode and making cast billets from it, while the total volume of the said casting cavities is selected from the condition of filling them with liquid metal without jumper between said casting cavities. 2. The vacuum arc furnace according to claim 1, characterized in that the recesses are made of various volumes. 3. The vacuum arc furnace according to claim 1, characterized in that the surface of the recesses is coated with a neutral flux based on CaF ₂ .

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