RU2180019C2 - Cathode copper to produce copper castings and rolled stock and process of its winning ( variants ) - Google Patents

Abstract

FIELD: non-ferrous metallurgy. SUBSTANCE: grain-oriented cathode copper with minimal saturation of precipitate with hydrogen for production of copper rolled stock by remelting, casting and hot rolling of billets in process of electric precipitation of cathode copper from aqueous solution is characterized by composition of copper predominantly from crystals with axes <111>, <100>of texture relative to direction of growth of precipitate with high reticular density with minimal content of crystals with texture axes <100>, <210> and others with low reticular density. In this case process of copper precipitation from aqueous solution containing ions of copper, sulfuric acid, ions of chlorine and organic additives consists in usage of non-stationary currents ( reverse, pulsating or combined pulsating-reverse ) and of at least one organic additive in which capacity anion-and surface- active substance, for example, alkyl sulfonates, alkyl bensolsulfonates, alkyl naphthalene sulfonates and the like is employed. EFFECT: increased quality of copper rolled stock thanks to reduced content of hydrogen in cathode copper for casting and rolling. 3 cl, 6 dwg, 3 tbl

Description

 The invention relates to the field of non-ferrous metallurgy and can be used in the production of cathode copper and its processing into castings and deformed products from copper and copper alloys.

 There are known requirements of GOST 859, GOST 546 for cathode copper of the MOOk, Mok, M1k brands, [1], ISO 431 standards [2, 3], the UK BS - 6017 [4, prototype] and other countries for Cu-SATTN cathode copper - 1, Cu-CATH-2.

 The drawback of cathode copper according to these standards is the lack of guaranteed manufacturability during hot rolling of the cast billet, the possible occurrence of hot cracks, which leads to a decrease in the production rate. In world practice, there is no method for predicting the rolling of cathode copper, for monitoring and controlling this quality of cathodes at the stage of their production. Therefore, the London Metal Exchange as the main condition for registering cathode copper puts it successfully tested on rolling mills of 2-3 leading companies, which is a long and expensive process.

 It is also known that the main reason for the formation of hot cracks is the saturation of the copper melt with hydrogen, followed by the release of water vapor and the formation of micropores during crystallization of copper [6].

 The content of dissolved hydrogen or Würz hydride in copper cathode is not fixed by modern gas analysis methods, which determine the total hydrogen content in the precipitate in the form of a solid solution, uncleaned electrolyte and inclusions of organic substances.

 Information on methods for producing electrolytic precipitation of copper with controlled dissolved hydrogen is not available in the literature. Only numerous studies are known to study the composition of cathode copper, depending on the conditions for its electrolytic deposition.

 There is completely no information about the laws governing the discharge of hydroxonium ions with the formation of not hydrogen gas, but a solid solution of hydrogen in a cathode deposit.

 Recently, the issue of obtaining textured copper deposits, i.e. precipitation with any crystallographic orientation; such precipitations have specific physicomechanical properties [17, p. 100-102].

Information on methods for producing electrolytic precipitation of metals with a given texture and physico-mechanical properties is not available in the literature. In a review of data on texture studies of electrodeposited metals for 1920–70 [9, p.141], it is stated that the characteristic texture for cathodic copper deposits is a texture with an axis <110>. With regard to electrolysis conditions, only the effect of cathodic overvoltage on the type of texture of the precipitate is considered proven. For metals with a face-centered cube lattice (silver, copper, nickel, lead, etc.), a low overvoltage corresponds to a texture <111>, medium - <100>, high - <110>, ultrahigh - <210>, which was experimentally confirmed by silver deposition [9, p. 121] and is consistent with world practice in producing cathode copper with high machinability by rolling during electrodeposition at current densities less than 200 A / m ² with low cathodic overvoltage.

It is known [12] and widely used in world practice that the reverse and pulsating current modes of electrodeposition of copper are used to produce even fine crystalline precipitates that meet the requirements of the chemical composition at current densities from 330 to 400 A / m ² .

 Closest to the first embodiment of the proposed method is a method for producing cathode copper, in accordance with which the electrodeposition of copper from an aqueous solution containing copper ions, sulfuric acid, chlorine ions and organic additives is carried out, and during electrodeposition, reversible and pulsating unsteady currents can be used, which allow change the speed of electrode processes [17, p.143-145, prototype].

 There are no data on current modes for obtaining copper deposits with a given texture and physico-mechanical properties.

 These issues are at the research stage; no ready-made technological modes for producing cathode copper with guaranteed rolling properties have been proposed.

Known methods for reducing the content of a number of impurities in the cathode copper, for example, using additives in the electrolyte of organic substances that belong to the class of anionic surfactants:
- sodium butylnaphthalene sulfonate from 5 to 100 mg / l in order to reduce the surface tension of the electrolyte, prevent the formation of "floating" sludge and reduce the loss of noble metals with cathodes during refining of copper with a high content of nickel and antimony [14];
- trialkyl phosphates in a concentration of from 50 to 500 mg / l, dialkyl phosphonates in a concentration of from 50 to 200 mg / l in order to reduce the silver content in the cathode deposit [15];
- sulfonol together with polyacrylamide during the deposition of copper foil in order to increase the adhesive properties of the foil without reducing its ductility [16].

 Closest to the second variant of the proposed method is a method for producing cathode copper, in accordance with which the electrodeposition of copper from an aqueous solution containing copper ions, sulfuric acid, chlorine ions and organic additives [17, p.122-124, prototype].

 As organic additives, surfactants are used that have the trade names Aviton, Separan, Orzan A, Gulakh, etc., the chemical composition, class, and purpose of which are unknown. The choice of surfactants is rather subjective. There are no data on the choice of organic additives for obtaining copper precipitates with a low hydrogen concentration, with a given texture and physico-mechanical properties.

 The proposed invention will achieve a technical result, expressed in improving the quality of copper by reducing the content of hydrogen or Wurz hydride in cathode copper for the production of castings and copper.

The specified technical result is achieved by the fact that in the process of electrodeposition of cathode copper for the production of castings and rolled metal from copper and copper alloys, a textured cathode copper is formed with minimal saturation of the precipitate with hydrogen, characterized in that it consists mainly of crystals with texture axes relative to the direction of growth of the precipitate <111>,<100> with a high reticular density with a minimum content of crystals with texture axes <110>, <210> with a low reticular density; the method of producing it by electrodeposition from an aqueous solution containing copper ions, sulfuric acid, chlorine ions and organic additives - consists in the fact that unsteady currents are used for electrodeposition - reverse, pulsating or combined pulsating-reversing currents with a sequence of periods: direct pulse - pause - reverse pulse, with a direct pulse duration of 10 to 300 s, pauses for pulsating and pulsating-reverse modes - from 1 to 5 s, reverse pulse for reverse and pulsating-reverse in the usual modes - from 0.5 to 1 s, at a current density of the direct pulse from 200 to 500 A / m ² , a reverse pulse from 100 to 300 A / m ² , and anionic surfactant is used as at least one organic additive an active substance (surfactant) selected from the group consisting of alkyl sulfonates, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alcohol sulfoethoxylates, amidosulfonates, salts of alkyl phosphonic acids with a specific consumption of from 20 to 200 g / t copper precipitate; high molecular weight, elastic, permeable surfactant from the group of animal glue, gelatin, casein, albumin, aldolase, globin, gum arabic, agar-agar, polyvinyl alcohols, polyacrylamide and others with a specific consumption rate are also used as an additive in the electrolyte from 30 to 150 g / t of copper precipitate, and thiourea with a specific flow rate of up to 100 g / t of copper precipitate is used as an additive to smooth the surface of the precipitate, an anionic surfactant is added to the condensate to rinse the cathodes and then turn on the reflector botany solution in the electrolyte when adjusting its composition.

 The essence of the invention consists in using the relationship between the content of hydrogen dissolved in the cathode precipitate and the texture of the precipitate — the orientation of the crystallographic planes relative to the directions of crystal growth during electrodeposition.

 On the planes of a copper crystal with a lattice of a face-centered cube (110), (210) and others with a low reticular density, there are favorable conditions for the formation of a solid solution of hydrogen in copper or Wurz hydride [5] both during electrodeposition from an aqueous solution and during heating precipitation in a hydrogen-containing atmosphere during the remelting of the cathodes, which is proved by studies on nickel, which, like copper, has an fcc lattice [6], and is consistent with the theory of the formation of interstitial solid solutions [7].

The possibility of saturation of the copper precipitate with hydrogen during its electrodeposition from an aqueous solution due to the discharge of hydroxonium ions by the reaction
H ₃ O + e -> [H] _cu + H ₂ 0
with the dissolution of atomic hydrogen in the precipitate is confirmed by our calculations according to reference thermodynamic data [8], which showed that the equilibrium concentration of hydrogen in the copper precipitate at a cathodic potential of +150 to -50 mV is 4-50 g / t.

The data obtained on copper single crystals indicate the electrochemical inequality of different crystallographic planes and a significant difference in them of the zero charge potential and the exchange currents of electrode reactions. In particular, for the electrode reaction Cu ²⁺ + 2e -> Cu, the exchange currents are, A / cm ² : for the (111) plane - 1.14 • 10 ^-3 ; for the plane (100) - 1.61 • 10 ^-3 ; for the (110) plane - 2.74 • 10 ^-3 [8].

 The corresponding shift in the discharge potentials of copper and hydroxonium ions and a half-density of packing of copper atoms during the discharge of ions and crystallization of the precipitate lead to a more significant discharge and dissolution of hydrogen on the (110) planes as compared to the (111) planes. Therefore, the degree of dissolution of hydrogen in the cathode deposit during electrolysis and the rolling of copper after its remelting without additional degassing is determined mainly by the texture of the cathode deposit. From the point of view of rolling ability, in the vector coordinate reference system, textures with axes <111> are the best, the worst - <110>. Therefore, to evaluate the quality of cathode copper for the production of rolled steel and to control this quality of cathodes at the stage of their production, along with the data of chemical analysis, as well as other requirements of the standards, the results of crystallographic analysis of the texture of cathode copper should be additionally used: cathode copper containing a predominant number of crystals with texture axes <111>, as well as crystals of other textures with a dense packing of planes by atoms with a minimum content of crystals with a texture axis <110> relative it to cathode copper with good rolling properties.

 Example 1

 The decisive effect of the texture of the copper cathode deposit on the processing of copper cathodes into a copper wire rod is proved by the results of industrial tests of three batches of cathode copper of one enterprise weighing 300 tons each at the Sautweiser continuous smelting and rolling plant with control of the texture of cathode copper samples, the mass fraction of sulfur in the cathodes wire rod and the output of copper wire rod of different classes according to the data of the current swirl defectomat "Ferster", are given in table 1.

 The residual hydrogen content in the wire rod of different classes amounted to, g / t: 1-2 grade - 0.3-0.5; Grade 3 - 1.0-1.1; Grade 4 - 1.4-1.5.

 Tests have shown that the texture of the cathode copper deposit is a more significant factor determining the defectiveness of the wire rod than the mass fraction of sulfur. The predominance of crystals with a texture axis <111> in batches 1 and 2 in the cathode deposit ensures a yield of wire rod of classes 1-2 of more than 90% even with a mass fraction, sulfur in the cathodes is higher than that stipulated by GOST 859 for MOOk grade copper, and a high content of crystals with a texture axis <110> of party 3 did not allow to obtain wire rod of grades 1-2 with an extremely low mass fraction of sulfur in the cathodes and wire rod. The data obtained indicate industrial applicability, novelty and inventive step of the claimed technical solution.

The essence of the proposed methods for producing cathode copper with the necessary texture at current densities of more than 200 A / m ² consists in applying the corresponding electric and colloidal electrodeposition modes, which ensure the formation of crystals with a given texture, or block the growth of faces with a low reticular density.

 According to the basic principles of theoretical electrochemistry at the initial stage of copper electrodeposition, the limiting stage is the formation of a large number of nuclei with a predominance of crystals with a texture <111> - a nucleation texture [10, p.207]. With further crystal growth, the texture <110> is formed - the texture of growth. The texture of the substrate or the texture of nucleation is preserved on the thickness of the sediment according to different data from 0.1 to 3 microns [9, p. 80], [11, p.136].

Based on these provisions, the condition for the formation of a cathodic copper deposit with a predominance of texture <111> is the deposition by layers with a thickness of 0.1 to 3 μm, which at current densities of 200-500 A / m ² corresponds to a deposition time of 10 to 300 s, i.e. non-stationary current modes - pulsating, reverse or combined pulsating-reverse in the sequence: forward pulse - pause - reverse pulse. The pause duration is determined by the conditions for equalizing the ion concentration by diffusion in the electrode layers of the electrolyte and should be from 1 to 5 s according to our calculations. the duration of the reverse pulse — by removing the anode passivation and recharging the double electric layer — from 0.5 to 1 s.

The use of reverse and pulsating current modes of copper electrodeposition for obtaining smooth fine crystalline precipitates that meet the requirements of the chemical composition at current densities from 330 to 400 A / m ^{2 is} known [12] and is widely used in world practice. About the use of non-stationary current modes to obtain copper sediment with the specified textures <111> and <100> information is missing, which allows us to conclude about the novelty and inventive step of the claimed technical solution.

 Example 2

The results of our texture studies of the cathode deposit of copper obtained at a current density of 350 A / m ^{2 by} deposition from an electrolyte containing 150 g / l sulfuric acid, 45 g / l copper, 40 mg / l chlorine ions with a specific gelatin consumption of 80 g / t copper , thiourea - 70 g / t of copper and a temperature of 60 ^o With different durations of a direct pulse, pause and reverse pulse are given in table. 2.

Reversing and pulsating current modes of copper electrorefining at a current density of the direct pulse of 360-370 A / m ² , reverse pulse - 200 A / m ² and the ratio of the duration of the direct pulse and reverse (or pause), s: 10: 0.5; 20: 1; 40: 1; 40: 2; 60: 3; 80: 4; 100: 5, tested under industrial conditions at colloidal mode with a specific consumption of additives, g / t: gelatin - 80; thiourea - 70. The most even precipitation with a current efficiency of at least 90% was obtained with reverse modes of 40: 1 and 10: 0, 5 s and pulsating 100: 5 s.

Based on texture studies of copper deposit and industrial tests to obtain textured copper cathodes with a predominance of textures with axes <111> and <100>, unsteady current electrolysis modes are proposed at current densities of 200 to 500 A / m ² — reversible, pulsating, and combined pulsating reverse pulse-pause-reverse pulse in the sequence with a duration of periods, s: forward pulse - from 10 to 300, pause - from 1 to 5, reverse pulse - from 0.5 to 1.

Another way to control the texture of the cathode deposit of copper is to block the growth of crystal faces with a low reticular density due to the adsorption of surfactants on them. According to the provisions of theoretical electrochemistry [13, p.335], various types of surfactants are adsorbed on the cathode surface and block the growth of the deposit in an unequal manner depending on the cathode potential and the potential of zero surface charge E _N.Z. : cationic surfactants - more negative E _N.Z. , nonionic (molecular) surfactants - near E _N.Z. , anionic surfactants - with a cathode potential more positive _than E _N.Z. .

 There are no data on the zero-charge potential of different crystallographic planes for copper; the reference literature provides the zero-charge potential only for polycrystalline copper samples: 0.0 V [8, p.155], +0.09 V [13, P.239], -0.118 V [10, p.176].

Our studies on industrial samples of textured cathode copper established the limits of the zero-charge potential of different crystallographic planes of a copper crystal: (111) from +0.20 to +0.25 V, (100) from +0.15 V to + 0.18 V, (110) - from 0.00 to +0.05 V. With these data taken into account, the cathode potential is from +0.05 to +0.25 V, corresponding to the electrodeposition of copper from a sulfate electrolyte with organic additives at current densities from 100 to 500 a / m ^2, the additive in the electrolyte of any anionic surfactant, dissociating to form a surface-active anion, bespechivaet surfactant adsorption on the faces (210) and (110) and blocking their growth while maintaining the free faces (111) and (100) with a high density reticular.

As additives of anionic surfactants in the electrolyte, not subjected to thermal decomposition or hydrolysis at temperatures up to 80 ^o C and sulfuric acid content up to 25 - g / l, can be used:
- alkyl sulfonates - sulfonate A, sulfonate B, volgonate, contact T, igepones, alkensulfonates, oxysulfonates, etc .;
- alkylbenzenesulfonates - sulfonols NP-1, NP-2, NP-3, chlorine sulfonol, ultra-K and W, etc .;
- alkylnaphthalene sulfonates - alkanols B and S, nekali A, B and BX, wetting agents NB, SV-101, dispersant NF, praventol, etc .;
- alcohol sulfoxides, amidosulfonates;
- salts of alkylphosphonic acids.

 On the use of a specific class of organic substances — anionic surfactants in copper electrodeposition processes — for the specific purpose — the formation of a certain type of texture of the cathode deposit of copper with minimal hydrogen saturation, there is no information in the world patent and technical literature.

 Example 3

Examples of obtaining textured cathodic copper deposits with minimal hydrogen saturation during electrodeposition from a solution containing 45 g / l of copper, 150 g / l of sulfuric acid, 40 mg / l of chlorine ions at a current density of 300 A / m ² , at a temperature of 60 ^o C, the specific consumption of gelatin is 70 g / t of sediment, thiourea - 70 g / t with additives of different types of anionic surfactants, are given in table. 3.

 The data presented indicate the effect of additives of anionic surfactants on the process of obtaining cathode copper with a certain structure: when using anionic surfactants, the content of crystals with texture 110 having a low reticular density in the sediment does not exceed 30%.

Tests in industrial baths of an anionic additive - sodium butyl sulfonate found that at current densities of up to 300 A / m ² this additive is not only texture-forming, but also leveling sediment, and at these current densities, thiourea can be partially or completely replaced by an anionic surfactant.

 Long industrial tests at two enterprises of the addition of sodium butylnaphthalene sulfonate to the electrolyte proved its positive effect on other indicators of copper electrorefining - current efficiency, specific energy consumption, reduction of electrolyte aerosol emissions from baths, reduction of precious metals with cathodes.

 The electrolyte should also include surface-active additives that do not affect the texture of the sediment, but perform other functions: thiourea at increased current densities due to chemisorption on the protrusions blocks the growth of cones and evens out the sediment, a colloidal additive of a high molecular weight elastic permeable substance from the group comprising animal glue, gelatin, casein, polyacrylamide, aldolase, globin, gum arabic, agar-agar, polyvinyl alcohols and others, creates an elastic film on the surface of the cathode for diffusion control the role of delivery to the surface of the cathode of ions and other surfactants.

 When using an anionic additive, its double role is effective in washing the cathodes from the electrolyte with condensate as a detergent, followed by the inclusion of washing water in the electrolyte when adjusting its composition.

 The application of the proposed group of inventions ensures the production of cathode copper with minimal saturation of the precipitate with hydrogen and guaranteed rolling of castings during thermoplastic processing.

Sources of information
1. GOST 859-78. Copper. Stamps.

 2. GOST 546-88. Copper cathodes. Technical conditions

 3. Standard ISO 431-81. Refined copper profiles.

 4. UK standard BS-6017-1981 as amended. AMD 5725. Refined shaped high-quality copper. Technical conditions

 5. M. Hansen, K. Anderko. Structures of double alloys, vol. II. - M.: Metallurgizdat, 1962, p. 629.

 6. Meyer K. Physico-chemical crystallography. -M .: Metallurgy, 1972.

 7. Umansky Ya. S. and other Physical metallurgy. M .: Metallurgizdat, 1955.

 8. Handbook of Electrochemistry / Ed. A.M. Sukhotina /.- L .: Chemistry. 1981, p. 169.

 9. Kochergin S.M., Leontiev A.V. The formation of textures during electrocrystallization of metals.- M .: Metallurgy, 1974.

 10. Levin A.I. Electrochemistry of non-ferrous metals. - M.: Metallurgy, 1982.

 11. Fedotiev N.P., Alabyshev A.F. and other Applied Electrochemistry.- L .: Chemistry, 1967.

 12. Gudima N.V., Zotkov O.M., Krivousov B.A., Titarenko A.G. Intensification of electrolytic refining of copper .- M.: Metallurgy. 1978.

 13. Rotinyan A.L., Tikhonov K.I., Shoshina I.A. Theoretical electrochemistry. - L .: Chemistry, 1981.

 14. Auth. St. USSR 1005500, IPC С 25 С 1/12, priority, 1981. Electrolyte for electrolytic refining of copper.

 15. Autost. USSR 1431379, IPC C 25 C 1/12, priority 1987. Method for the electrolytic refining of copper in solution.

 16. Auth. St. USSR 955735, IPC С 25 С 1/12, priority 1981. A method for producing plastic copper foil.

 17. Kozlov V.A., Naboychenko S.S., Smirnov B.N. Copper refining. - M.: Metallurgy, 1992.

Claims (9)

 1. Cathode copper for the production of castings and rolled copper, characterized in that it consists mainly of crystals with texture axes relative to the direction of growth of the precipitate <111>, <100> with a high reticular density with a minimum content of crystals with texture axes <110>, < 210> with low reticular density.  2. A method of producing cathode copper for the production of castings and rolled metal, including electrodeposition from an aqueous solution containing copper ions, sulfuric acid, chlorine ions and organic additives, characterized in that for the electrodeposition using unsteady currents - reversible, pulsating or combined pulsating-reversible with a sequence of periods: forward impulse - pause - reverse impulse with a direct impulse duration of 10 to 300 s, pause duration with a pulsating and pulsating-reverse modes from 1 to 5 s, the duration of the reverse pulse in the reverse and pulsating-reverse modes from 0.5 to 1 s. 3. The method according to p. 2, characterized in that the direct pulse current density is from 200 to 500 A / m ² , the reverse pulse current density is from 100 to 300 A / m ² .  4. The method according to p. 2, characterized in that it further conduct quality control of the cathode copper according to crystallographic analysis of the texture of the cathode copper.  5. A method of producing cathode copper for the production of castings and rolled metal, including electrodeposition from an aqueous solution containing copper ions, sulfuric acid, chlorine ions and organic additives, characterized in that anionic surfactant is used as at least one organic additive active substance selected from the group consisting of alkyl sulfonates, alkyl benzene sulfonate, alkylnaphthalene sulfonates, sulfoethoxylates of alcohols, amidosulfonates, salts of alkylphosphonic acids with a specific flow rate of from 20 to 200 g / t adka copper.  6. The method according to p. 5, characterized in that as an additive to the electrolyte use a high molecular weight, elastic, permeable surfactant selected from the group consisting of animal glue, gelatin, casein, albumin, aldolase, globin, gum arabica , agar-agar, polyvinyl alcohols, polyacrylamide with a specific consumption of 30 to 150 g / t copper precipitate.  7. The method according to p. 5, characterized in that as an additive to smooth the surface of the precipitate, thiourea is used with a specific consumption of up to 100 g / t of copper precipitate.  8. The method according to p. 5, characterized in that the addition of the anionic surfactant is introduced into the condensate for washing the cathodes with the subsequent inclusion of the spent solution in the electrolyte when adjusting its composition.  9. The method according to p. 5, characterized in that it further conduct quality control of the cathode copper according to crystallographic analysis of the texture of the cathode copper.

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