RU2762460C1 - Method for producing special copper ingots - Google Patents

Abstract

FIELD: non-ferrous metallurgy.

SUBSTANCE: invention relates to the field of non-ferrous metallurgy, specifically to the production of high-purity copper ingots for superconducting materials. Strips of cathode copper are used as starting materials, the stage of preparation of starting materials is carried out by cutting sheets of cathode copper into strips 150±10 mm wide, straightening and milling at the ends, the production of a consumable electrode is carried out by welding the strips together, with one of the ends. The electrode is prepared for fastening to the furnace rod, after which a sequential triple electron-beam remelting of the obtained consumable electrode is carried out, with intermediate machining of the surface of the welded ingots to a depth of 3-7 mm after all stages of remelting.

EFFECT: invention makes it possible to weld ingots of high-purity copper with an oxygen content of no more than 0.0015% and a minimum level of impurities of non-ferrous metals.

3 cl, 2 tbl, 2 dwg

Description

1. Field of technology

The invention relates to the field of non-ferrous metallurgy, specifically to methods for producing ingots of high-purity copper for superconducting materials. The method includes the stage of preparing the starting materials by cutting sheets of cathode copper into strips 150 ± 10 mm wide, straightening and milling them at the ends, making a consumable electrode by welding the strips together, while one of the ends of the welded electrode is prepared for fastening to the furnace rod followed by a sequential triple electron-beam remelting of the obtained consumable electrode, with intermediate machining of the surface of the welded ingots after all stages of remelting. The method allows surfacing ingots of high-purity copper with an oxygen content of no more than 0.0015% and a minimum level of impurities of non-ferrous metals.

2. Prior art

The known "Method for producing high-quality copper by vacuum arc melting" (Patent RU 2 156 822 (C22 B 15/14), 2000), including melting copper cathodes in a graphite crucible with a non-consumable graphite electrode with a specific power of an electric arc within 4⋅10 ⁶ - 6 ⋅10 ⁶ W per 1 m ^{2 of the} inner cross-section of the crucible during the time, the duration of which is determined by the expression: 8.1 cth / 10 ^-9 ⋅q / ≤τ≤8.9cth / 10 ^-9 ⋅q /, where cth - hyperbolic cotangent function; τ is the duration of the melting, s; q is the specific power of the electric arc, W / m ² . The known method does not provide for obtaining ingots of high-purity copper for superconducting materials of the required purity and the established requirements for electrical properties due to the insufficient degree of refining of the melt.

There is a known "Method of obtaining in vacuum high-purity copper ingots" (Patent RU 2 407 815 (С22В 15/14), 2010), including obtaining copper melt, refining the melt from volatile oxides and other impurities, deoxidizing with carbon, refining in a deoxidized state, casting metal into ingots and crystallization, and before melting, copper charge materials are subjected to surface etching and melted in a graphite crucible, on the bottom of which graphite pieces are placed in an amount of 0.15-0.6% of the copper charge weight. The disadvantage of this method is the lack of effective operations, providing the oxygen content in the ingots of high-purity copper less than 0.003%.

The known "Method of obtaining a workpiece from copper or its alloys" (Patent RU 2 247 162 (C22B 09/18, C22B 15/00), 2005), which includes the manufacture of a consumable electrode from charge materials, its electroslag remelting into a mold on a pallet, the formation the ingot and its deformation to obtain a billet, while the consumable electrode is made by melting the charge materials in a 6-12-ton crucible in a vacuum induction furnace, the electroslag remelting of the consumable electrode is carried out into a crystallizer with a diameter of 500-700 mm, while the electric remelting mode is selected depending on from the diameter of the mold, seven seeds are placed on the pallet, one - in the center and six - along the periphery at the wall of the mold, and the electrical contact is dispersed onto the seeds, and after deformation the workpiece is cooled in air. The disadvantage of the technical solution is that it does not allow to obtain copper ingots with a low oxygen content of less than 0.040%.

It is also known accepted by the applicant for the closest analogue - the method of vacuum-arc remelting ("Electric industrial furnaces. Arc furnaces and special-purpose installations" edited by A.D. Svenchansky, 2nd ed., M., Energoizdat, 1981, p. . 217), in which the consumable electrode is mechanically attached to the electrode holder of the vacuum arc furnace using a collet or wedge clutch. The disadvantage of this method is that it is not possible to achieve an oxygen content in copper ingots of less than 0.003%.

3. The essence of the invention

3.1. Formulation of a technical problem

The technical result, which the invention is aimed at, consists in obtaining ingots of high-purity copper with an oxygen content of no more than 0.0015% and a minimum level of impurities of non-ferrous metals.

The result of solving a technical problem

The problem is solved due to the fact that the smelting of high-purity copper ingots is carried out in an electron-beam furnace using a consumable electrode pre-fabricated by welding strips of cathode copper to each other.

3.2. Features

In contrast to the known technical solution, which includes the preparation of raw materials, the manufacture of a consumable electrode from them and its remelting to obtain an ingot; in the claimed technical solution, strips of cathode copper are used as starting materials, the stage of preparing the starting materials is carried out by cutting sheets of cathode copper into strips with a width of 150 ± 10 mm, their straightening and milling at the ends, the manufacture of a consumable electrode is carried out by welding the strips together, while one of the ends of the welded electrode is prepared for fastening to the furnace rod, after which sequential triple electron-beam remelting of the obtained consumable electrode is carried out, with intermediate machining of the surface of the welded ingots after all stages of remelting.

Electron beam remelting is carried out at a speed of the order of 4-7 mm / min and a power of 150-170 kW, while the vacuum is maintained at a level of (3.0-5.0) × 10 ^-4 mm Hg.

After all stages of electron-beam remelting, the deposited copper ingots are machined to a depth of 3–7 mm.

3.3. List of drawing figures

FIG. 1 shows a prepared consumable electrode for electron beam remelting, where 1 is the appearance of a consumable electrode after welding of cathode copper strips to each other; 2 - a welded arc-shaped bracket to one of the ends of the consumable electrode, in the form of a curved metal strip or reinforcement, for its movement and attachment to the furnace rod for subsequent electron-beam remelting; 3 - opposite end of the welded consumable electrode.

FIG. 2 shows a processed high-purity copper ingot after triple electron-beam remelting.

4. Description of the invention

Refining of metal in electron beam remelting (EBR) is based, as in vacuum arc remelting (VAR), on the drop melting of an ingot under conditions of evacuating the melting chamber of the furnace, however, the interaction of the metal with a rarefied gas phase under EBR conditions is different.

An independent heat source with EBM makes it possible to regulate the rate of deposition of the ingot and, accordingly, the duration of the metal's stay in the liquid state, within a wide range. In the course of electron beam remelting, the level of the metal bath remains unchanged near the upper edge of the mold, and the consumable electrode supplied from the top does not prevent the removal of gases and vapors released from the melt. The high energy concentration of the electron beam allows for a significant overheating of the surface of the metal bath, which exceeds this indicator for VAR conditions by about 100 ÷ 150 ° C.

As you know, when a consumable electrode is remelted, the metal is refined at three stages of its existence in a liquid state: in a film at the melting end of the electrode, in drops and on the surface of a liquid metal bath. Under comparable conditions (productivity, diameter of the mold used), the gas - metal interface area at the last two stages is, respectively, the same for both remelting methods. In this case, the areas of the melted end of the electrode may differ several times. So, during the VAR, the end face of the consumable electrode is usually flat and, therefore, the area of this surface is approximately equal to the cross section of the remelted electrode. With EBM, with a vertical feed of the consumable electrode, its melted end acquires a conical shape (with an apex angle from 30 to 60 °), due to which the area of this surface is 2-4 times greater than the cross-sectional area of the electrode. In combination with a higher liquid metal temperature, a deeper vacuum in the working space, this creates favorable conditions for better metal degassing, evaporation of non-ferrous metals and dissociation of non-metallic inclusions. Removal of impurities occurs in the liquid metal film at the end of the consumable electrode being melted.

In the claimed technical solution, at the stage of preparation of raw materials, strips of cathode copper, sheets of cathode copper are cut, they are straightened and milled at the ends, manufacture of a consumable electrode and electron-beam remelting, while the following operations are sequentially performed:

- cutting of cathode copper sheets into strips 150 ± 10 mm wide;

- welding of strips of cathode copper to each other (Fig. 1);

- welding of an arcuate bracket, in the form of a curved metal strip or reinforcement, to one of the ends of the welded electrode to move it and attach it to the furnace rod for subsequent electron beam remelting (Fig. 1);

- sequential triple electron-beam remelting of the obtained consumable electrode. The consumable electrode for EBM is fed from the top. The solidification of the ingot takes place in a water-cooled crystallizer. An iron plate is used as a seed plate. Electron beam remelting is carried out at a speed of the order of 4 ÷ 7 mm / min and a power of 150 ÷ 170 kW, while the vacuum is maintained at a level of (3.0 ÷ 5.0) × 10 ^-4 mm Hg;

- deposited copper ingots after all stages of electron-beam remelting are subjected to machining to a depth of 3 ÷ 7 mm (Photo 2).

The use of the proposed method allows the deposition of high-purity copper ingots with an oxygen content of no more than 0.0015%, and also to reduce the level of impurities of non-ferrous metals.

5. An example of a specific implementation (implementation of the method)

The production of high-purity copper ingots was carried out by the method of multiple electron-beam remelting into a mold with a diameter of 250 mm according to the following scheme:

preparation of raw materials (cutting, straightening, milling of strips) → production of a consumable electrode (welding of strips into a batch) → first electron-beam remelting → machining of an ingot → second electron-beam remelting → machining of an ingot → third electron-beam remelting → machining ingot.

Electron-beam remelting was carried out in an U-254 electron-beam furnace into a crystallizer with a diameter of 250 mm. Starting power at the level of 150 ÷ 170 kW. Electrode feed rate in the 4 ÷ 7 mm / min mode. The mode was stable on all swimming trunks. After the end of the melting, the ingot was held in a furnace under vacuum, after which air was puffed in. The parameters of deposited and processed copper ingots are given in Table 1.

Samples were taken from each deposited ingot to determine the chemical composition according to the "G-X" system. The results of the chemical analysis are shown in Table 2.

Thus, the use of the proposed method allows the deposition of high-purity copper ingots with an oxygen content of no more than 0.0015% and a minimum level of impurities of non-ferrous metals.

Claims (3)

1. A method of obtaining ingots of high-purity copper, including the preparation of starting materials, making a consumable electrode from them and remelting it to obtain an ingot, characterized in that strips of cathode copper are used as starting materials, the stage of preparing starting materials is carried out by cutting sheets of cathode copper into strips width 150 ± 10 mm, their straightening and milling at the ends, the manufacture of a consumable electrode is carried out by welding the strips together, while one of the ends of the welded electrode is prepared for fastening to the furnace rod, after which a sequential triple electron-beam remelting of the obtained consumable electrode is carried out, with an intermediate by mechanical treatment of the surface of the welded ingots after all stages of remelting. 2. The method according to claim 1, characterized in that the electron-beam remelting is performed at a speed of the order of 4-7 mm / min and a power of 150-170 kW, while the vacuum is maintained at a level of (3.0-5.0) × 10 ^-4 mm Hg 3. The method according to claim 1, characterized in that the deposited copper ingots after all stages of electron beam remelting are machined to a depth of 3–7 mm.

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