EP0910489A1 - Element of a continuous metal casting ingot mould with a copper or copper alloy cooled wall comprising on its external surface a metal coating, and method of coating - Google Patents

Element of a continuous metal casting ingot mould with a copper or copper alloy cooled wall comprising on its external surface a metal coating, and method of coating

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Publication number
EP0910489A1
EP0910489A1 EP97930592A EP97930592A EP0910489A1 EP 0910489 A1 EP0910489 A1 EP 0910489A1 EP 97930592 A EP97930592 A EP 97930592A EP 97930592 A EP97930592 A EP 97930592A EP 0910489 A1 EP0910489 A1 EP 0910489A1
Authority
EP
European Patent Office
Prior art keywords
wall
silver
copper
coating
silvering
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP97930592A
Other languages
German (de)
French (fr)
Other versions
EP0910489B1 (en
Inventor
Jean-Michel Damasse
Jean-Claude Catonne
Christian Allely
Guido Stebner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thyssen Stahl AG
USINOR SA
Original Assignee
Thyssen Stahl AG
USINOR SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thyssen Stahl AG, USINOR SA filed Critical Thyssen Stahl AG
Publication of EP0910489A1 publication Critical patent/EP0910489A1/en
Application granted granted Critical
Publication of EP0910489B1 publication Critical patent/EP0910489B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/059—Mould materials or platings
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/46—Electroplating: Baths therefor from solutions of silver
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/10—Electroplating with more than one layer of the same or of different metals
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/60—Electroplating characterised by the structure or texture of the layers
    • C25D5/615—Microstructure of the layers, e.g. mixed structure
    • C25D5/617—Crystalline layers
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/67—Electroplating to repair workpiece

Definitions

  • the invention relates to the continuous casting of metals. More specifically, it relates to the coating of the external surface of the copper or copper alloy walls of the molds in which the solidification of metals such as steel is initiated.
  • the continuous casting of metals such as steel is carried out in molds bottomless, with walls energetically cooled by an internal circulation of a cooling liquid such as water
  • the metal in the liquid state is brought into contact with the external surfaces of these walls and initiates its solidification there.
  • These walls must be made of an excellent heat conducting material, so that they * can evacuate enough calories from the metal in a reduced time.
  • copper or one of its alloys, for example containing chromium and zirconium, is adopted for this purpose.
  • the faces of these walls which are intended to be in contact with the liquid metal are coated with a layer of nickel whose initial thickness can reach up to 3 mm. It constitutes a protective layer for copper which prevents it from being overheated thermally and mechanically.
  • This nickel layer wears out over the use of the mold. It must therefore be restored periodically by total removal of the remaining thickness and then depositing a new layer, but such restoration obviously costs much less than a complete replacement of the worn copper walls. Conventionally, the nickel layer is restored as soon as its thickness has dropped to about 0.6 mm.
  • this layer of nickel on the walls of the mold is therefore a fundamental step in the preparation of the casting machine, and it is important to optimize both the cost, the properties of use and the qualities of adhesion. This is, in particular, the case on machines intended for casting steel products in the form of strips a few mm thick which do not need to be then hot rolled.
  • These machines comprise an ingot mold constituted by two cylinders rotating in opposite directions around their axes which are kept horizontal, and two refractory side plates pressed against the edges of the cylinders. These cylinders have a diameter of up to 1500 mm, and a width which, on current experimental installations, is approximately 600 to 1300 mm.
  • the complete nickel removal operation of the shell which must precede the restoration of the nickel layer is also fundamental.
  • its successful completion largely conditions the quality of the nickel layer which will then be deposited, in particular its adhesion to the shell, since it turns out to be very difficult to deposit a new layer of strongly adherent nickel on a older nickel layer.
  • this nickel removal operation must be carried out without very significant consumption of the copper from the ferrule which is an extremely expensive part, and the duration of use of which must be extended as much as possible.
  • This last requirement in particular, practically excludes the use of a purely mechanical method for this nickel-plating, since its precision would not be sufficient to guarantee both a total elimination of the nickel and a safeguard of the copper over the entire surface. of the shell.
  • the object of the invention is to propose a method of coating the external surface of the copper or copper alloy wall of a continuous casting mold generally more economical than the usual methods where a layer of nickel is deposited on this surface.
  • This method should also provide the walls of the mold with characteristics and quality at least comparable to those obtained. by depositing a layer of nickel. It should also include a step of periodic regeneration of this surface.
  • This method should be particularly suitable for the coating of cylinder ferrules for a casting machine between cylinders or on a single cylinder.
  • the subject of the invention is an element of a mold for the continuous casting of metals, comprising a cooled wall of copper or copper alloy intended to be brought into contact with liquid metal and comprising on its external surface a metallic coating, characterized in that said coating consists of a silver layer.
  • this wall is a cylinder shell for a machine for continuously casting thin metal strips between two cylinders or on a single cylinder.
  • the invention also relates to a method of coating with a metallic layer the external surface of a wall cooled in copper or copper alloy of a mold element for continuous casting of metals, characterized in that this is carried out coating by depositing a layer of silver on said surface, preferably by electrolytic means.
  • the restoration of said silver layer is carried out by leaving a residual silver layer on said wall, and by resilvering said layer by placing said cathode wall in an electrolysis bath constituted, by for example, with an aqueous solution of silver cyanide, cyanide of an alkali metal and carbonate of an alkali metal.
  • the invention consists first of all in replacing with silver the nickel traditionally used to form the external coating of the walls of copper ingot molds for continuous casting of metals such as steel. Contrary to what you might think at first glance since solid silver is considered a precious metal, this solution has multiple economic advantages, and it is perfectly technically viable. This is particularly the case when the silvering is carried out by an electrolytic method using a bath with alkaline cyanides. It has been found that such baths are suitable for producing silver deposits on copper having properties of use well suited to the protection of the walls of continuous casting molds.
  • the particular method of coating the surface of the mold which is also described and claimed includes a silvering step, and also optionally a step of silvering said surface when it is desired to restore the coating of a used mold.
  • This silvering may be only partial, whereas in the case of a nickel coating, the nickel removal of the copper must almost imperatively be total, at the risk of consuming a part of the copper of the wall.
  • Both silvering and silvering can be done by electrolytic means.
  • the silver removed from the ferrule is recovered in metallic form on the silver cathode in the deticianing reactor. Said cathode can in turn be recycled as an anode in the silvering reactor.
  • the silver removal can be carried out at least in part by chemical or mechanical means.
  • the invention will now be described in detail in one of its embodiments, applied to the coating of a copper ferrule or copper alloy of a cylinder for a machine for continuously casting steel between two cylinders or on a single cylinder.
  • the example described could easily be adapted to the cases of other types of ingot molds with copper or copper alloy walls, such as ingot molds with fixed walls for the continuous casting of slabs, biooms or billets.
  • the silvering or de-silvering method can implement various other electrolytic processes such as pad or spray coatings, as well as electrolytes different from those given in example.
  • the new ferrule is generally in the form of a hollow cylinder made of copper or a copper alloy, such as a copper-chromium alloy (1%) - zirconium (0.1%).
  • Its outside diameter is, for example, of the order of 1500 mm and its length is equal to the width of the strips which it is desired to pour, that is to say of the order of 600 to 1500 mm.
  • Its thickness may be, for information, of the order of 180 mm, but varies locally depending, in particular, on the method of fixing the ferrule to the core of the cylinder which has been adopted.
  • the ferrule is crossed by channels intended to be traversed by a cooling fluid such as water, when using the casting machine.
  • the treatment stations in the silvering / de-silvering workshop each consist of a tank containing a solution suitable for carrying out a given stage of treatment, above which the said tree can be placed with its horizontal axis and the rotate around its axis.
  • the lower part of the ferrule is thus soaked in the solution, and the rotation of the shaft / ferrule assembly makes it possible to carry out the treatment of the entire ferrule (it being understood that the ferrule normally performs several turns on it - even during the same treatment, at a speed of about 10 revolutions / min, for example).
  • the bare ferrule (in the case of the first silver plating of a new ferrule, or the silver plating of a used ferrule whose copper surface has been exposed), is preferably first subjected to mechanical preparation by polishing its surface. Then a chemical degreasing is carried out in an alkaline medium, which has the function of ridding the surface of the shell of organic materials which can pollute it. It is carried out hot, at a temperature of about 40 to 70 ° C for about fifteen minutes, and followed by rinsing with water. It can be substituted for, or even added to, an electrolytic degreasing step which would provide an even better surface quality.
  • the next step is a pickling operation in an oxidizing acid medium, which has the function of removing surface oxides, taking care to dissolve only a very minimal thickness of the shell.
  • an aqueous solution of sulfuric acid at 100 ml / 1 is used, to which 50 ml / 1 of a 30% solution of hydrogen peroxide or a another compound solution.
  • a solution of chromic acid this compound having both acidic and oxidizing properties.
  • This pickling operation in an oxidizing acid medium has maximum efficiency when the temperature of the electrolyte is between 40 and 55 ° C. It is advantageous to maintain this temperature at the interface by circulating hot water inside the channels of the rotating shell. The operation lasts approximately 5 minutes and is followed by rinsing with water.
  • the set of preparatory operations for silvering which have just been described has a total duration which, in principle, does not exceed 30 minutes.
  • the purpose of the pre-silvering operation, carried out prior to the actual silvering, is intended to be placed under chemical conditions intended to prevent a displacement of silver by the copper during the silvering, which would be detrimental to the adhesion deposit money. It is particularly useful even if the ferrule is not pure copper, but a Cu-Cr-Zr alloy. It lasts 4 to 5 minutes and is preferably done at room temperature, the ferrule being placed as a cathode in an electrolyte consisting of an aqueous solution of sodium cyanide (50 to 90 g / l approximately) and sufficiently silver cyanide diluted in dissolved metal (30 to 50 g / 1). We can also replace sodium cyanide with potassium cyanide (65 to 100 g / 1).
  • One or more soluble (silver) or insoluble anodes can be used -
  • insoluble anodes there is destruction of the free cyanide which transforms into carbonate and releases ammonium. It is therefore necessary to periodically recharge this electrolyte with free cyanide additions which can advantageously be taken from the rinsing effluents which follows the silvering operation proper.
  • This pre-silvering operation makes it possible to deposit on the surface of the ferrule a layer of silver a few ⁇ m thick (1 to 2 ⁇ m for example) while removing the acid deposits which could remain after brightening.
  • the ferrule is then transferred as quickly as possible to the silver plating station without undergoing rinsing, in order to take advantage of the presence on its surface of a cyanide film which protects it from passivation.
  • the actual silvering operation is carried out in an electrolyte essentially based on an aqueous solution of sodium and silver cyanides, to which an excess of free sodium hydroxide is added, but may also consist of a mixture of cyanides of potassium and silver in excess free potash. Potassium carbonate is also added.
  • a typical composition for this bath is: - AgCN: 115 to 150 g / 1; - KCN: 215 to 250 g / 1; - KOH: 30 to 40 g / 1;
  • the optimal operating temperature is 40 to 45 ° C.
  • the potassium carbonate is necessary to obtain homogeneous corrosion of the anodes. It can be replaced by sodium carbonate, with the disadvantage that sodium carbonate has a lower solubility. Potash can be replaced by soda. They ensure the conductivity of the electrolyte, as well as the stability of the anionic complex under which the silver is found (Ag (CN) 4 • ** • -).
  • the silver plating operation is generally carried out using a direct current source, which can advantageously be replaced by a source of transient currents, which make it possible to increase the fineness of the crystallization.
  • the crystallization can also be advantageously modified by lowering the temperature of the shell / electrolyte interface, for example by circulating cold water through the channels of the shell. Under these conditions, the silver electrolyte is a hot source and the ferrule is cold source A temperature gradient is established and the interface then offers a greater activation overvoltage, favorable to increasing the hardness of the coating
  • the anode or anodes are soluble anodes constituted by one or more anodic baskets of titanium containing beads of silver or metallic silver in any other form, for example cartons
  • These titanium panodes are used as dimensionally stable electrodes
  • Their shape follows that of the ferrule in its submerged part, which makes it possible to homogenize the distribution of the densities of cathodic current on the ferrule As the anode-cathode distance does not vary under these conditions, the panodes keep the current densities constant on the cathode
  • the silver layer undergoes attacks and mechanical wear which lead to its progressive consumption. Between two castings, the surface of the shell must be cleaned, and the silver layer can, at least from time to time. , to undergo a light machining intended to compensate for the possible heterogeneities of its wear which could compromise the homogeneity of the thermomechanical behavior of the ferrule on all of its surface II is also important to restore the initial roughness of the ferrule whenever this is necessary.
  • a predetermined value which is generally estimated at around 1 mm
  • the use of the cylinder is interrupted, the ferrule is disassembled and can undergo a treatment for complete or only partial desilvering, which must precede the restoration of the silver layer of the shell. For this purpose, the ferrule can be again mounted on the axis which supported it during the silvering operations. If the silver removal is complete, the silver layer is then restored according to the whole process which has just been described.
  • the silver is dissolved by placing the ferrule as an anode in an appropriate electrolyte, generally based on nitric acid and containing a copper inhibitor, such as phosphate ions.
  • an appropriate electrolyte generally based on nitric acid and containing a copper inhibitor, such as phosphate ions.
  • a copper inhibitor such as phosphate ions.
  • One way to shorten the silver reduction operation would be to precede it with a mechanical silver removal operation which would aim to reduce its residual thickness without however reaching the copper.
  • This operation would also have the advantage of homogenizing this thickness and removing the various surface impurities (in particular metal residues) which could locally slow down the start of dissolution. We would still avoid being still dissolving the silver in certain areas of the shell even when in other areas the copper has already been exposed.
  • the method of silver plating by electrolytic route has the drawback of requiring for its implementation a special solution, incompatible for reasons of toxicity with the other operations carried out in the silver plating-silver plating workshop where ferrules are used. elsewhere cyanide solutions.
  • the inventors therefore recommend practicing the restoration of the silver coating of the shell by direct recharging in a silver plating bath (advantageously that which served for the first silver plating previously described), without obligation to completely or almost completely remove the coating. residual money.
  • Such a procedure is possible, because it is easy to electrochemically deposit a new layer of silver on an older layer of silver and to obtain good adhesion of the new layer to the old, whereas this does not is not an option for nickel.
  • the silver refill does not have the defects generally attributed to other forms of demetallization in general and of nickel removal in particular, due to the natural alkalinity of the silver plating bath. .
  • This alkalinity can, in fact, be used as a means of natural passivation of the infrastructure of the silvering station if it is made of uncoated steel.
  • Another advantage of the invention is that it never needs to wear said steel infrastructures in an anodic situation, which would promote their corrosion and would be detrimental to their durability.
  • Another advantage of direct refill silvering compared to almost total electrochemical silvering followed by resilvering is to avoid the total dissolution of silver in certain preferential areas (such as the edges of the shell) during silvering, which would lead to localized exposures of copper. In addition, it makes the renewal of the pre-silvering stage unnecessary. Finally, the refill silvering carried out under conditions avoiding any dissolution of the copper of the ferrule makes it possible not to attack the surface of the ferrule, therefore to prolong its duration of use.
  • the refill silvering can be preceded by a light machining of the used silver layer, to homogenize its thickness and remove impurities which would be detrimental to the adhesion of the new silver layer on the old.
  • a silver-plating workshop for ferrules would therefore be distinguished in that it would not necessarily include an installation for dissolving a used coating by chemical or electrochemical means. It would therefore be more economical to build. It would also be more economical to exploit, because it would consume less electricity: silver deposits three times faster than nickel with an equal current density, in particular because it is monovalent while nickel is bivalent. This advantage is however partially offset in that, to obtain equivalent thermal protection of the shell with a silver deposit and a nickel deposit, a silver layer must be deposited approximately twice as thick as the corresponding nickel layer. . On the other hand, this layer of silver offers mechanical protection of the shell that is superior to the thinner layer of nickel.
  • the cost of the silver salts used is, in fact, not very different from that of the nickel salts used for the traditional nickel plating of the walls of the mold. Overall, the cost of a silver coating is therefore not much higher than that of a nickel coating, and above all the repair of a used ferrule of a casting cylinder is much faster and economical.
  • Cyanide effluents from the workshop can be treated with bleach to destroy the cyanides. Since bleach is easily produced electrolytically, these effluents can be treated slightly chlorinated by continuous electrolysis: the metallic silver is recovered at the cathode and the cyanides in ammonium carbonate are directly destroyed on anionally stable anodes. Simple and economical solutions can therefore be found to the environmental problems that can arise from the use of cyanide salts.
  • the invention particularly finds its application to the conditioning of the ferrules of cylinders of continuous casting installations of steel between cylinders or on a single cylinder, because of the large dimensions and the high cost of manufacturing these parts, of which it is important. to extend life as much as possible. But it goes without saying that one can envisage its transposition to the treatments of walls of ingot molds of copper or copper alloy of all shapes and formats, intended for the casting of all metals supporting being put in the liquid state. , in contact with silver under the casting conditions.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Metallurgy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Coating With Molten Metal (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Electroplating And Plating Baths Therefor (AREA)

Abstract

The invention concerns an element of a continuous metal casting ingot mould with a copper or copper alloy cooled wall to be contacted with liquid metal and comprising on its external surface a metal coating, characterised in that the said coating consists of a silver plating. In a preferred embodiment, this wall is a cylinder hoop for a continuous casting machine of thin metal strips between two cylinders or on one single cylinder. The invention also concerns a method for coating with a metal plating the external surface of a copper or copper alloy cooled wall of an element of a continuous metal casting ingot mould, characterised in that a coating is effected by the deposit of a silver plating on said surface preferably by electrolysis. Preferably, the restoration of said silver plating is done by allowing a residual silver plating to subsist on said wall, and by effecting a re-silvering of said plating by placing said wall in cathode in an electrolysis consisting, for instance, of an aqueous silver cyanide solution, of an alkaline metal cyanide and of an alkaline metal carbonate.

Description

ELEMENT D'UNE LINGOTIERE POUR LA COULEE CONTINUE DES ELEMENT OF A LINGOTIERE FOR THE CONTINUOUS CASTING OF
METAUX, COMPRENANT UNE PAROI REFROIDIE EN CUIVRE OU ENMETALS, INCLUDING COOLED OR COPPER WALL
ALLIAGE DE CUIVRE COMPORTANT SUR SA SURFACE EXTERNE UNCOPPER ALLOY HAVING AN EXTERNAL SURFACE ON
REVETEMENT METALLIQUE, ET PROCEDE POUR SON REVETEMENTMETAL COATING, AND METHOD FOR COATING
L'invention concerne la coulée continue des métaux. Plus précisément, elle concerne le revêtement de la surface externe des parois en cuivre ou en alliage de cuivre des lingotières dans lesquelles on initie la solidification des métaux tels que l'acier La coulée continue de métaux tels que l'acier est effectuée dans des lingotières sans fond, aux parois énergiquement refroidies par une circulation interne d'un liquide refroidissant tel que de l'eau Le métal à l'état liquide est amené au contact des surfaces externes de ces parois et y amorce sa solidification. Ces parois doivent être réalisées en un matériau excellent conducteur de la chaleur, afin qu'elles * puissent évacuer suffisamment de calories du métal en un temps réduit. Généralement, on adopte à cet effet le cuivre ou un de ses alliages, contenant par exemple du chrome et du zirconium.The invention relates to the continuous casting of metals. More specifically, it relates to the coating of the external surface of the copper or copper alloy walls of the molds in which the solidification of metals such as steel is initiated. The continuous casting of metals such as steel is carried out in molds bottomless, with walls energetically cooled by an internal circulation of a cooling liquid such as water The metal in the liquid state is brought into contact with the external surfaces of these walls and initiates its solidification there. These walls must be made of an excellent heat conducting material, so that they * can evacuate enough calories from the metal in a reduced time. Generally, copper or one of its alloys, for example containing chromium and zirconium, is adopted for this purpose.
Généralement, les faces de ces parois qui sont destinées à être au contact du métal liquide sont revêtues d'une couche de nickel dont l'épaisseur initiale peut atteindre jusqu'à 3 mm. Elle constitue pour le cuivre une couche protectrice qui lui évite d'être trop sollicité thermiquement et mécaniquement.Generally, the faces of these walls which are intended to be in contact with the liquid metal are coated with a layer of nickel whose initial thickness can reach up to 3 mm. It constitutes a protective layer for copper which prevents it from being overheated thermally and mechanically.
Cette couche de nickel s'use au fil de l'utilisation de la lingotière. Elle doit donc être restaurée périodiquement par enlèvement total de l'épaisseur subsistante puis dépôt d'une nouvelle couche, mais une telle restauration coûte évidemment beaucoup moins cher qu'un remplacement complet des parois de cuivre usées. Classiquement, on restaure la couche de nickel dès que son épaisseur est descendue à 0,6 mm environ.This nickel layer wears out over the use of the mold. It must therefore be restored periodically by total removal of the remaining thickness and then depositing a new layer, but such restoration obviously costs much less than a complete replacement of the worn copper walls. Conventionally, the nickel layer is restored as soon as its thickness has dropped to about 0.6 mm.
Le dépôt de cette couche de nickel sur les parois de la lingotière est donc une étape fondamentale dans la préparation de la machine de coulée, et il est important d'en optimiser à la fois le coût, les propriétés d'emploi et les qualités d'adhérence. C'est, en particulier, le cas sur les machines destinées à couler des produits sidérurgiques sous forme de bandes de quelques mm d'épaisseur qui n'ont pas besoin d'être ensuite laminées à chaud. Ces machines, dont la mise au point est actuellement en cours, comportent une lingotière constituée par deux cylindres tournant en sens contraires autour de leurs axes maintenus horizontaux, et de deux plaques latérales en réfractaire plaquées contre les chants des cylindres. Ces cylindres ont un diamètre pouvant atteindre 1500 mm, et une largeur qui, sur les installations expérimentales actuelles, est d'environ 600 à 1300 mm. Mais à terme, cette largeur devra atteindre 1300 à 1900 mm pour satisfaire les impératifs de productivité d'une installation industrielle. Ces cylindres sont constitués par un noyau en acier autour duquel est fixée une virole en cuivre ou alliage de cuivre, refroidie par une circulation d'eau entre le noyau et la virole ou, plus généralement, par une circulation d'eau interne à la virole. C'est la face externe de cette virole qui doit être recouverte de nickel, et on imagine aisément que, du fait de la forme et des dimensions de cette virole, son revêtement soit plus complexe que celui des parois des lingotières de coulée continue classiques qui sont formées d'éléments tubulaires ou d'un assemblage de plaques planes, et qui sont de dimensions beaucoup plus réduites. L'optimisation du mode de dépôt du nickel est d'autant plus importante dans le cas des viroles pour cylindres de coulée que:The deposition of this layer of nickel on the walls of the mold is therefore a fundamental step in the preparation of the casting machine, and it is important to optimize both the cost, the properties of use and the qualities of adhesion. This is, in particular, the case on machines intended for casting steel products in the form of strips a few mm thick which do not need to be then hot rolled. These machines, the development of which is currently in progress, comprise an ingot mold constituted by two cylinders rotating in opposite directions around their axes which are kept horizontal, and two refractory side plates pressed against the edges of the cylinders. These cylinders have a diameter of up to 1500 mm, and a width which, on current experimental installations, is approximately 600 to 1300 mm. But ultimately, this width should reach 1300 to 1900 mm to meet the productivity requirements of an industrial installation. These cylinders consist of a steel core around which is fixed a copper ferrule or copper alloy, cooled by a circulation of water between the core and the ferrule or, more generally, by a circulation of water internal to the ferrule. It is the external face of this ferrule which must be covered with nickel, and it is easy to imagine that, because of the shape and dimensions of this ferrule, its coating is more complex than that of the walls of conventional continuous casting molds which are formed of tubular elements or an assembly of flat plates, and which are of much smaller dimensions. Optimizing the nickel deposition mode is all the more important in the case of ferrules for casting rolls since:
- du fait de l'absence de laminage à chaud ultérieur, les défauts de surface de la bande qui résulteraient d'une médiocre qualité du revêtement de nickel risquent davantage de s'avérer rédhibitoires pour la qualité du produit final;- Due to the absence of subsequent hot rolling, the surface defects of the strip which would result from poor quality of the nickel coating are more likely to prove unacceptable for the quality of the final product;
- comme les quantités de nickel à déposer sur les viroles avant leur utilisation et à enlever au début de l'opération de régénération de la couche sont relativement importantes, cela conduit à consommer d'importantes quantités d'électricité, et à consacrer un temps très important notamment à l'opération de nickelage: typiquement plusieurs jours.- as the quantities of nickel to be deposited on the ferrules before their use and to be removed at the start of the layer regeneration operation are relatively large, this leads to consuming large quantities of electricity, and spending a very long time important in particular for the nickel plating operation: typically several days.
L'opération de dénickelage complet de la virole qui doit précéder la restauration de la couche de nickel est également fondamentale. D'une part, son bon achèvement conditionne en grande partie la qualité de la couche de nickel qui va être ensuite déposée, notamment son adhérence sur la virole, car il s'avère très difficile de déposer une nouvelle couche de nickel fortement adhérente sur une couche de nickel plus ancienne. D'autre part, cette opération de dénickelage doit être effectuée sans consommation très significative du cuivre de la virole qui est une pièce extrêmement onéreuse, et dont la durée d'utilisation doit être prolongée autant que possible. Cette dernière exigence, notamment, exclut pratiquement l'emploi d'une méthode purement mécanique pour ce dénickelage, car sa précision ne serait pas suffisante pour garantir à la fois une élimination totale du nickel et une sauvegarde du cuivre sur l'ensemble de la surface de la virole.The complete nickel removal operation of the shell which must precede the restoration of the nickel layer is also fundamental. On the one hand, its successful completion largely conditions the quality of the nickel layer which will then be deposited, in particular its adhesion to the shell, since it turns out to be very difficult to deposit a new layer of strongly adherent nickel on a older nickel layer. On the other hand, this nickel removal operation must be carried out without very significant consumption of the copper from the ferrule which is an extremely expensive part, and the duration of use of which must be extended as much as possible. This last requirement, in particular, practically excludes the use of a purely mechanical method for this nickel-plating, since its precision would not be sufficient to guarantee both a total elimination of the nickel and a safeguard of the copper over the entire surface. of the shell.
D'autres procédés de coulée visent à couler des bandes métalliques encore plus minces par dépôt du métal liquide sur la périphérie d'un cylindre unique en rotation, qui peut également être constitué d'un noyau en acier et d'une virole refroidie en cuivre. Les problèmes de revêtement de la surface de la virole qui viennent d'être décrits s'y posent exactement de la même façon.Other casting methods aim at casting even thinner metal strips by depositing the molten metal on the periphery of a single rotating cylinder, which can also consist of a steel core and a cooled copper ferrule. . The coating problems of the surface of the shell which have just been described arise there in exactly the same way.
Le but de l'invention est de proposer une méthode de revêtement de la surface externe de la paroi en cuivre ou alliage de cuivre d'une lingotière de coulée continue globalement plus économique que les méthodes habituelles où on dépose une couche de nickel sur cette surface. Cette méthode devrait également procurer aux parois de la lingotière des caractéristiques et une qualité au moins comparables à celles obtenues par dépôt d'une couche de nickel. Elle devrait également inclure une étape de régénération périodique de cette surface. Cette méthode devrait être particulièrement adaptée au cas du revêtement des viroles de cylindres pour machine de coulée entre cylindres ou sur un cylindre unique. A cet effet, l'invention a pour objet un élément d'une lingotière pour la coulée continue des métaux, comprenant une paroi refroidie en cuivre ou en alliage de cuivre destinée à être mise au contact du métal liquide et comportant sur sa surface externe un revêtement métallique, caractérisée en ce que ledit revêtement est constitué par une couche d'argent. Dans une application préférentielle de l'invention, cette paroi est une virole de cylindre pour machine de coulée continue de bandes métalliques minces entre deux cylindres ou sur un cylindre unique.The object of the invention is to propose a method of coating the external surface of the copper or copper alloy wall of a continuous casting mold generally more economical than the usual methods where a layer of nickel is deposited on this surface. . This method should also provide the walls of the mold with characteristics and quality at least comparable to those obtained. by depositing a layer of nickel. It should also include a step of periodic regeneration of this surface. This method should be particularly suitable for the coating of cylinder ferrules for a casting machine between cylinders or on a single cylinder. To this end, the subject of the invention is an element of a mold for the continuous casting of metals, comprising a cooled wall of copper or copper alloy intended to be brought into contact with liquid metal and comprising on its external surface a metallic coating, characterized in that said coating consists of a silver layer. In a preferred application of the invention, this wall is a cylinder shell for a machine for continuously casting thin metal strips between two cylinders or on a single cylinder.
L'invention a également pour objet un procédé de revêtement par une couche métallique de la surface externe d'une paroi refroidie en cuivre ou alliage de cuivre d'un élément de lingotière de coulée continue des métaux, caractérisé en ce qu'on réalise ce revêtement par dépôt d'une couche d'argent sur ladite surface de préférence par voie électrolytique.The invention also relates to a method of coating with a metallic layer the external surface of a wall cooled in copper or copper alloy of a mold element for continuous casting of metals, characterized in that this is carried out coating by depositing a layer of silver on said surface, preferably by electrolytic means.
Préférentiellement, la restauration de ladite couche d'argent s'effectue en laissant subsister sur ladite paroi une couche d'argent résiduelle, et en procédant à une réargenture de ladite couche en plaçant ladite paroi en cathode dans un bain d'électrolyse constitué, par exemple, par une solution aqueuse de cyanure d'argent, de cyanure d'un métal alcalin et de carbonate d'un métal alcalin.Preferably, the restoration of said silver layer is carried out by leaving a residual silver layer on said wall, and by resilvering said layer by placing said cathode wall in an electrolysis bath constituted, by for example, with an aqueous solution of silver cyanide, cyanide of an alkali metal and carbonate of an alkali metal.
Comme on l'aura compris, l'invention consiste en premier lieu à remplacer par de l'argent le nickel traditionnellement utilisé pour former le revêtement externe des parois de lingotières en cuivre de coulée continue des métaux tels que l'acier. Contrairement à ce que l'on pourrait croire à première vue puisque l'argent massif est considéré comme un métal précieux, cette solution présente de multiples avantages économiques, et elle est parfaitement viable techniquement. C'est particulièrement le cas lorsque l'argenture est réalisée par une méthode électrolytique employant un bain aux cyanures alcalins. Il s'est avéré que de tels bains sont aptes à la réalisation de dépôts d'argent sur du cuivre présentant des propriétés d'usage bien adaptées à la protection des parois de lingotières de coulée continue.As will be understood, the invention consists first of all in replacing with silver the nickel traditionally used to form the external coating of the walls of copper ingot molds for continuous casting of metals such as steel. Contrary to what you might think at first glance since solid silver is considered a precious metal, this solution has multiple economic advantages, and it is perfectly technically viable. This is particularly the case when the silvering is carried out by an electrolytic method using a bath with alkaline cyanides. It has been found that such baths are suitable for producing silver deposits on copper having properties of use well suited to the protection of the walls of continuous casting molds.
Le procédé particulier de revêtement de la surface de la lingotière qui est également décrit et revendiqué inclut une étape d'argenture, et aussi éventuellement une étape de désargenture de ladite surface lorsqu'on désire restaurer le revêtement d'une lingotière usagée. Cette désargenture peut n'être que partielle, alors que dans le cas d'un revêtement de nickel, le dénickelage du cuivre doit quasi impérativement être total, au risque de consommer une partie du cuivre de la paroi. L'argenture et la désargenture peuvent être toutes deux réalisées par des moyens électrolytiques. L'argent éliminé de la virole est récupéré à l'état métallique sur la cathode d'argent dans le réacteur de désargenture. Ladite cathode peut à son tour être recyclée comme anode dans le réacteur d'argenture. En variante la désargenture peut être réalisée au moins en partie par des moyens chimiques ou mécaniques. L'invention va à présent être décrite en détail dans l'une de ses formes de réalisation, appliquée au revêtement d'une virole en cuivre ou alliage de cuivre de cylindre pour machine de coulée continue de l'acier entre deux cylindres ou sur un cylindre unique. Mais il est clair que l'exemple décrit pourra aisément être adapté aux cas d'autres types de lingotières à parois en cuivre ou alliage de cuivre, tels que les lingotières à parois fixes pour la coulée continue de brames, biooms ou billettes. Il est également clair que la méthode d'argenture ou de désargenture peut mettre en œuvre différents autres procédés électrolytiques tels que les revêtements au tampon ou par aspersion, ainsi que des électrolytes différents de ceux donnés en exemple. On peut également prévoir une immersion complète de la paroi en cuivre dans un bain d'argenture, et dans ces conditions l'invention peut être appliquée sur une virole en rotation permanente ou intermittente, ou bien sur une virole maintenue immobile dans un électrolyte en circulation forcée.The particular method of coating the surface of the mold which is also described and claimed includes a silvering step, and also optionally a step of silvering said surface when it is desired to restore the coating of a used mold. This silvering may be only partial, whereas in the case of a nickel coating, the nickel removal of the copper must almost imperatively be total, at the risk of consuming a part of the copper of the wall. Both silvering and silvering can be done by electrolytic means. The silver removed from the ferrule is recovered in metallic form on the silver cathode in the deagenturing reactor. Said cathode can in turn be recycled as an anode in the silvering reactor. Alternatively, the silver removal can be carried out at least in part by chemical or mechanical means. The invention will now be described in detail in one of its embodiments, applied to the coating of a copper ferrule or copper alloy of a cylinder for a machine for continuously casting steel between two cylinders or on a single cylinder. However, it is clear that the example described could easily be adapted to the cases of other types of ingot molds with copper or copper alloy walls, such as ingot molds with fixed walls for the continuous casting of slabs, biooms or billets. It is also clear that the silvering or de-silvering method can implement various other electrolytic processes such as pad or spray coatings, as well as electrolytes different from those given in example. It is also possible to provide for complete immersion of the copper wall in a silver plating bath, and under these conditions the invention can be applied to a ferrule in permanent or intermittent rotation, or else to a ferrule kept immobile in a circulating electrolyte forced.
Classiquement, la virole neuve se présente globalement sous la forme d'un cylindre creux en cuivre ou en alliage de cuivre, tel qu'un alliage cuivre-chrome (1%)- zirconium (0,1%). Son diamètre extérieur est, par exemple, de l'ordre de 1500 mm et sa longueur est égale à la largeur des bandes que l'on désire couler, soit de l'ordre de 600 à 1500 mm. Son épaisseur peut être, à titre indicatif, de l'ordre de 180 mm, mais varie localement en fonction, notamment, du mode de fixation de la virole sur le noyau du cylindre qui a été adopté. La virole est traversée par des canaux destinés à être parcourus par un fluide refroidissant tel que de l'eau, lors de l'utilisation de la machine de coulée.Conventionally, the new ferrule is generally in the form of a hollow cylinder made of copper or a copper alloy, such as a copper-chromium alloy (1%) - zirconium (0.1%). Its outside diameter is, for example, of the order of 1500 mm and its length is equal to the width of the strips which it is desired to pour, that is to say of the order of 600 to 1500 mm. Its thickness may be, for information, of the order of 180 mm, but varies locally depending, in particular, on the method of fixing the ferrule to the core of the cylinder which has been adopted. The ferrule is crossed by channels intended to be traversed by a cooling fluid such as water, when using the casting machine.
Pour faciliter les manipulations de la virole lors des opérations qui vont être décrites, celle-ci est d'abord montée sur un arbre, et c'est ainsi qu'elle sera transportée d'un poste de traitement à l'autre avant son montage sur le noyau du cylindre. Les postes de traitement de l'atelier d'argenture/désargenture sont chacun constitués par un bac contenant une solution adaptée à l'exécution d'une étape donnée du traitement, au- dessus duquel on peut placer ledit arbre avec son axe horizontal et le mettre en rotation autour de son axe. On fait ainsi tremper la partie inférieure de la virole dans la solution, et la mise en rotation de l'ensemble arbre/virole permet de réaliser le traitement de l'ensemble de la virole (étant entendu que la virole effectue normalement plusieurs tours sur elle-même au cours d'un même traitement, à une vitesse d'environ 10 tours/mn, par exemple). Sur ces postes de traitement, il peut également être utile, afin d'éviter une pollution ou une passivation par l'atmosphère ambiante de la partie émergée de la virole, de prévoir un dispositif d'arrosage de cette partie émergée avec la solution de traitement. On peut également, à cet effet, envisager d'inerter l'atmosphère ambiante au moyen d'un gaz neutre tel que de l'argon, et/ou installer un système de protection cathodique de la virole. Toutefois, si cela est possible, on peut prévoir que ces bacs permettent une immersion totale de la virole, ce qui rend un tel arrosage ou inertage sans objet.To facilitate handling of the shell during the operations which will be described, it is first mounted on a shaft, and this is how it will be transported from one treatment station to the other before it is assembled. on the cylinder core. The treatment stations in the silvering / de-silvering workshop each consist of a tank containing a solution suitable for carrying out a given stage of treatment, above which the said tree can be placed with its horizontal axis and the rotate around its axis. The lower part of the ferrule is thus soaked in the solution, and the rotation of the shaft / ferrule assembly makes it possible to carry out the treatment of the entire ferrule (it being understood that the ferrule normally performs several turns on it - even during the same treatment, at a speed of about 10 revolutions / min, for example). On these treatment stations, it can also be useful, in order to avoid pollution or passivation by the ambient atmosphere of the part emerged from the shell, to provide a device for watering this emerged portion with the treatment solution. One can also, for this purpose, consider inerting the ambient atmosphere by means of a neutral gas such as argon, and / or installing a cathodic protection system for the ferrule. However, if this is possible, provision can be made for these tanks to allow total immersion of the shell, which makes such watering or inerting not applicable.
La virole nue (dans le cas de la première argenture d'une virole neuve, ou de l'argenture d'une virole usagée dont on aurait mis à nu la surface en cuivre) subit d'abord, de préférence, une préparation mécanique par polissage de sa surface. Puis on pratique un dégraissage chimique en milieu alcalin, qui a pour fonction de débarrasser la surface de la virole des matières organiques qui peuvent la polluer. Il est réalisé à chaud, à une température d'environ 40 à 70°C pendant une quinzaine de minutes, et suivi d'un rinçage à l'eau. On peut lui substituer, voire lui ajouter, une étape de dégraissage électrolytique qui procurerait une qualité de surface encore meilleure. L'étape suivante est une opération de décapage en milieu acide oxydant, qui a pour fonction d'ôter les oxydes de surface, en veillant à ne dissoudre qu'une épaisseur très minime de la virole. On utilise à cet effet, par exemple, une solution aqueuse d'acide sul-urique à 100 ml/1, à laquelle on ajoute avant chaque opération 50 ml/1 d'une solution à 30% d'eau oxygénée ou d'une solution d'un autre percomposé. On peut également utiliser une solution d'acide chromique, ce composé présentant à la fois des propriétés acides et oxydantes. Cette opération de décapage en milieu acide oxydant présente une efficacité maximale lorsque la température de l'électrolyte est comprise entre 40 et 55°C. Il est avantageux de maintenir cette température à l'interface par une circulation d'eau chaude à l'intérieur des canaux de la virole en rotation. L'opération dure environ 5 minutes et est suivie d'un rinçage à l'eau.The bare ferrule (in the case of the first silver plating of a new ferrule, or the silver plating of a used ferrule whose copper surface has been exposed), is preferably first subjected to mechanical preparation by polishing its surface. Then a chemical degreasing is carried out in an alkaline medium, which has the function of ridding the surface of the shell of organic materials which can pollute it. It is carried out hot, at a temperature of about 40 to 70 ° C for about fifteen minutes, and followed by rinsing with water. It can be substituted for, or even added to, an electrolytic degreasing step which would provide an even better surface quality. The next step is a pickling operation in an oxidizing acid medium, which has the function of removing surface oxides, taking care to dissolve only a very minimal thickness of the shell. For this purpose, for example, an aqueous solution of sulfuric acid at 100 ml / 1 is used, to which 50 ml / 1 of a 30% solution of hydrogen peroxide or a another compound solution. It is also possible to use a solution of chromic acid, this compound having both acidic and oxidizing properties. This pickling operation in an oxidizing acid medium has maximum efficiency when the temperature of the electrolyte is between 40 and 55 ° C. It is advantageous to maintain this temperature at the interface by circulating hot water inside the channels of the rotating shell. The operation lasts approximately 5 minutes and is followed by rinsing with water.
On a avantage à réaliser ensuite une opération d'avivage, de préférence avec une solution d'acide sulfurique à 10 g/1, dans le but d'éviter la passivation de la surface de la virole.It is then advantageous to carry out a brightening operation, preferably with a 10 g / l sulfuric acid solution, in order to avoid passivation of the surface of the shell.
L'ensemble des opérations préparatoires à l'argenture que l'on vient de décrire a une durée totale qui, en principe, n'excède pas 30 minutes.The set of preparatory operations for silvering which have just been described has a total duration which, in principle, does not exceed 30 minutes.
L'opération de préargenture, exécutée préalablement à l'argenture proprement dite, a pour but de se placer dans des conditions chimiques destinées à empêcher un déplacement d'argent par le cuivre lors de l'argenture, ce qui serait préjudiciable à l'adhérence du dépôt d'argent. Elle est particulièrement utile même si la virole n'est pas en cuivre pur, mais en alliage Cu-Cr-Zr. Elle dure 4 à 5 minutes et se pratique de préférence à la température ambiante, la virole étant placée en cathode dans un électrolyte constitué par une solution aqueuse de cyanure de sodium (50 à 90 g/1 environ) et de cyanure d'argent suffisamment dilué en métal dissous (30 à 50 g/1). On peut également remplacer le cyanure de sodium par du cyanure de potassium (65 à 100 g/1). Le fait d'utiliser pour cette opération de préargenture un électrolyte dont la composition, comme on le verra, est qualitativement comparable à celle du bain d'argenture, permet de se dispenser d'une étape de rinçage intermédiaire. D'autre part, elle permet aussi de valoriser l'effluent résultant du rinçage après argenture, cet efïluent pouvant avantageusement être recyclé dans le bain de préargenture. La densité de courant cathodique est de 4 à 5 A/dm*--*. On peut utiliser une ou des anodes solubles (en argent) ou insolubles (par exemple en Ti/Ptθ2 ou Ti/Ruθ2)- Dans le cas d'anodes insolubles, il y a destruction du cyanure libre qui se transforme en carbonate et libère de l'ammonium. Il est donc nécessaire de recharger périodiquement cet électrolyte par des appoints de cyanure libre que l'on peut avantageusement prélever dans les effluents du rinçage qui suit l'opération d'argenture proprement dite. Cette opération de préargenture permet de déposer sur la surface de la virole une couche d'argent de quelques μm d'épaisseur (1 à 2 μm par exemple) tout en enlevant les dépôts acides qui pourraient subsister après l'avivage. La virole est ensuite transférée aussi rapidement que possible à la station d'argenture sans subir de rinçage, afin de profiter de la présence à sa surface d'un film de cyanure qui la protège de la passivation.The purpose of the pre-silvering operation, carried out prior to the actual silvering, is intended to be placed under chemical conditions intended to prevent a displacement of silver by the copper during the silvering, which would be detrimental to the adhesion deposit money. It is particularly useful even if the ferrule is not pure copper, but a Cu-Cr-Zr alloy. It lasts 4 to 5 minutes and is preferably done at room temperature, the ferrule being placed as a cathode in an electrolyte consisting of an aqueous solution of sodium cyanide (50 to 90 g / l approximately) and sufficiently silver cyanide diluted in dissolved metal (30 to 50 g / 1). We can also replace sodium cyanide with potassium cyanide (65 to 100 g / 1). The fact of using for this pre-silvering operation an electrolyte whose composition, as will be seen, is qualitatively comparable to that of the silver plating bath, makes it possible to dispense with an intermediate rinsing step. On the other hand, it also makes it possible to enhance the effluent resulting from the rinsing after silvering, this effluent can advantageously be recycled in the pre-silvering bath. The cathodic current density is 4 to 5 A / dm * - * . One or more soluble (silver) or insoluble anodes (for example Ti / Ptθ2 or Ti / Ruθ2) can be used - In the case of insoluble anodes, there is destruction of the free cyanide which transforms into carbonate and releases ammonium. It is therefore necessary to periodically recharge this electrolyte with free cyanide additions which can advantageously be taken from the rinsing effluents which follows the silvering operation proper. This pre-silvering operation makes it possible to deposit on the surface of the ferrule a layer of silver a few μm thick (1 to 2 μm for example) while removing the acid deposits which could remain after brightening. The ferrule is then transferred as quickly as possible to the silver plating station without undergoing rinsing, in order to take advantage of the presence on its surface of a cyanide film which protects it from passivation.
L'opération d'argenture proprement dite est conduite dans un électrolyte à base essentiellement d'une solution aqueuse de cyanures de sodium et d'argent, à laquelle on ajoute un excès de soude libre, mais peut également consister en un mélange de cyanures de potassium et d'argent dans un excès de potasse libre. On ajoute également du carbonate de potassium. Une composition typique pour ce bain est: - AgCN: 115 à 150 g/1; - KCN: 215 à 250 g/1; - KOH: 30 à 40 g/1;The actual silvering operation is carried out in an electrolyte essentially based on an aqueous solution of sodium and silver cyanides, to which an excess of free sodium hydroxide is added, but may also consist of a mixture of cyanides of potassium and silver in excess free potash. Potassium carbonate is also added. A typical composition for this bath is: - AgCN: 115 to 150 g / 1; - KCN: 215 to 250 g / 1; - KOH: 30 to 40 g / 1;
- K2CO3: 10 à 15 g/1.- K 2 CO 3 : 10 to 15 g / 1.
La température optimale de fonctionnement est de 40 à 45°C Le carbonate de potassium est nécessaire pour obtenir une corrosion homogène des anodes. Il peut être remplacé par du carbonate de sodium, avec l'inconvénient que le carbonate de sodium a une solubilité plus faible. La potasse peut être remplacée par de la soude. Elles assurent la conductivité de l'électrolyte, ainsi que la stabilité du complexe anionique sous lequel se trouve l'argent (Ag(CN)4 •**•-). L'opération d'argenture est généralement pratiquée à l'aide d'une source de courant continu, laquelle peut avantageusement être remplacée par une source de courants transitoires, qui permettent d'augmenter la finesse de la cristallisation. La cristallisation peut aussi être avantageusement modifiée en abaissant la température de l'interface virole/électrolyte, par exemple grâce à une circulation d'eau froide à travers les canaux de la virole. Dans ces conditions, l'électrolyte d'argenture est source chaude et la virole est source froide Un gradient de température s'établit et l'interface offre alors une plus grande surtension d'activation, favorable à l'augmentation de la dureté du revêtementThe optimal operating temperature is 40 to 45 ° C. The potassium carbonate is necessary to obtain homogeneous corrosion of the anodes. It can be replaced by sodium carbonate, with the disadvantage that sodium carbonate has a lower solubility. Potash can be replaced by soda. They ensure the conductivity of the electrolyte, as well as the stability of the anionic complex under which the silver is found (Ag (CN) 4 • ** • -). The silver plating operation is generally carried out using a direct current source, which can advantageously be replaced by a source of transient currents, which make it possible to increase the fineness of the crystallization. The crystallization can also be advantageously modified by lowering the temperature of the shell / electrolyte interface, for example by circulating cold water through the channels of the shell. Under these conditions, the silver electrolyte is a hot source and the ferrule is cold source A temperature gradient is established and the interface then offers a greater activation overvoltage, favorable to increasing the hardness of the coating
Comme on l'a dit, dans l'exemple décrit (qui, de ce point de vue, n'est pas limitatif), la ou les anodes sont des anodes solubles constituées par un ou des paniers anodiques en titane contenant des billes d'argent ou de l'argent métallique sous toute autre forme, par exemple des berlingots Ces panodes de titane sont utilisées comme des électrodes dimensionneliement stables Leur forme épouse celle de la virole dans sa partie immergée, ce qui permet d'homogénéiser la distribution des densités de courant cathodiques sur la virole Comme la distance anode-cathode ne varie pas dans ces conditions, les panodes maintiennent constantes les densités de courant sur la cathodeAs has been said, in the example described (which, from this point of view, is not limiting), the anode or anodes are soluble anodes constituted by one or more anodic baskets of titanium containing beads of silver or metallic silver in any other form, for example cartons These titanium panodes are used as dimensionally stable electrodes Their shape follows that of the ferrule in its submerged part, which makes it possible to homogenize the distribution of the densities of cathodic current on the ferrule As the anode-cathode distance does not vary under these conditions, the panodes keep the current densities constant on the cathode
A moins qu'il ne soit possible de réaliser l'immersion totale de la virole dans l'électrolyte, il est très conseillé de réaliser un arrosage permanent de la surface de la partie non immergée de la virole par ce même électrolyte, ou un inertage de cette même partie par un gaz neutre On évite ainsi les risques de passivation de la surface fraîchement argentée, passivation qui serait préjudiciable à la bonne adhérence et à la bonne cohésion du revêtement Pour cette même raison, un arrosage de la virole ou un inertage de sa surface lors de son transfert entre le poste de préargenture et le poste d'argenture est également recommandé Une mise sous protection cathodique de la virole est également envisageable Ce transfert doit, de toute façon, être effectué le plus rapidement possibleUnless it is possible to completely immerse the shell in the electrolyte, it is highly advisable to permanently spray the surface of the non-submerged part of the shell with this same electrolyte, or inerting of this same part by a neutral gas This avoids the risks of passivation of the freshly silvered surface, passivation which would be detrimental to the good adhesion and to the good cohesion of the coating. For this same reason, watering the shell or inerting the its surface during its transfer between the pre-silvering station and the silvering station is also recommended A cathodic protection of the ferrule is also possible This transfer must, in any case, be carried out as quickly as possible
On peut travailler soit à tension imposée, soit à densité de courant imposée Lorsque l'électrolyse est effectuée sous une tension de l'ordre de 10 V avec une densité de courant d'environ 4 A dm2, une durée de 5 à 8 jours environ (qui dépend aussi de la profondeur d'immersion de la virole dans le bain) permet d'obtenir un dépôt d'argent atteignant 3 mm d'épaisseur. La virole est ensuite désolidarisée de son axe support, et est prête à être assemblée au noyau pour former un cylindre qui va être utilisé sur la machine de coulée, après un éventuel ultime conditionnement de la surface de la couche d'argent, tel que l'impression d'une rugosité déterminée par un grenaillage, un usinage laser ou un autre procédé Comme il est connu, un tel conditionnement vise à optimiser les conditions de transfert thermique entre la virole et le métal en cours de solidificationIt is possible to work either at an imposed voltage or at an imposed current density. When the electrolysis is carried out at a voltage of the order of 10 V with a current density of approximately 4 A dm 2 , a duration of 5 to 8 days. approximately (which also depends on the depth of immersion of the shell in the bath) makes it possible to obtain a silver deposit up to 3 mm thick. The ferrule is then detached from its support axis, and is ready to be assembled with the core to form a cylinder which will be used on the casting machine, after a possible final conditioning of the surface of the silver layer, such as the impression of a roughness determined by shot peening, laser machining or another process As is known, such packaging aims to optimize the conditions of thermal transfer between the shell and the metal being solidified
Au cours de cette utilisation, la couche d'argent subit des attaques et une usure mécanique qui entraînent sa consommation progressive Entre deux coulées, la surface de la virole doit être nettoyée, et la couche d'argent peut, au moins de temps en temps, subir un léger usinage destiné à compenser les éventuelles hétérogénéités de son usure qui pourraient compromettre l'homogénéité du comportement thermomécanique de la virole sur l'ensemble de sa surface II est également important de restaurer la rugosité initiale de la virole chaque fois que cela est nécessaire Lorsque l'épaisseur moyenne de la couche d'argent de la virole atteint une valeur prédéterminée, que l'on estime généralement à environ 1 mm, l'utilisation du cylindre est interrompue, la virole est démontée et peut subir un traitement de désargenture complète ou seulement partielle, qui doit précéder la restauration de la couche d'argent de la virole. A cet effet, la virole peut être à nouveau montée sur l'axe qui la supportait lors des opérations d'argenture. Si la désargenture est complète, on procède ensuite à la restauration de la couche d'argent selon l'ensemble du processus qui vient d'être décrit.During this use, the silver layer undergoes attacks and mechanical wear which lead to its progressive consumption. Between two castings, the surface of the shell must be cleaned, and the silver layer can, at least from time to time. , to undergo a light machining intended to compensate for the possible heterogeneities of its wear which could compromise the homogeneity of the thermomechanical behavior of the ferrule on all of its surface II is also important to restore the initial roughness of the ferrule whenever this is necessary When the thickness average of the silver layer of the ferrule reaches a predetermined value, which is generally estimated at around 1 mm, the use of the cylinder is interrupted, the ferrule is disassembled and can undergo a treatment for complete or only partial desilvering, which must precede the restoration of the silver layer of the shell. For this purpose, the ferrule can be again mounted on the axis which supported it during the silvering operations. If the silver removal is complete, the silver layer is then restored according to the whole process which has just been described.
Plusieurs possibilités s'offrent à l'utilisateur pour réaliser la désargenture. Une désargenture par voie purement chimique est envisageable. Mais le réactif utilisé devrait dissoudre l'argent sans attaquer significativement le substrat en cuivre, et il serait difficile de réaliser de manière bien maîtrisée une désargenture seulement partielle. Une autre voie de désargenture totale ou partielle envisageable est la voie électrolytique, du fait des différences sensibles entre les potentiels normaux du cuivre et de l'argent (respectivement 0,3 V et -0,8 V par rapport à l'électrode normale à hydrogène). Elle est aussi applicable pour les alliages cuivre-chro e-zirconium pouvant constituer la virole. Dans ce cas, la dissolution de l'argent se fait en plaçant la virole en anode dans un électrolyte approprié, généralement à base d'acide nitrique et contenant un inhibiteur du cuivre, tel que des ions phosphate. Un moyen de raccourcir l'opération de désargenture consisterait à la faire précéder d'une opération d'enlèvement mécanique de l'argent qui viserait à diminuer son épaisseur résiduelle sans toutefois atteindre le cuivre. Cette opération aurait également l'avantage d'homogénéiser cette épaisseur et d'ôter les impuretés superficielles diverses (notamment les résidus métalliques) qui pourraient ralentir localement le début de la dissolution. On éviterait encore d'en être toujours à la dissolution de l'argent en certaines zones de la virole alors même que dans d'autres zones le cuivre aurait déjà été mis à nu.Several possibilities are offered to the user to achieve the silvering. Silver removal by purely chemical means is possible. However, the reagent used should dissolve the silver without significantly attacking the copper substrate, and it would be difficult to achieve only partial de-silvering in a well controlled manner. Another possible way of total or partial silvering is the electrolytic way, due to the appreciable differences between the normal potentials of copper and silver (respectively 0.3 V and -0.8 V compared to the normal electrode at hydrogen). It is also applicable for copper-chro e-zirconium alloys which may constitute the ferrule. In this case, the silver is dissolved by placing the ferrule as an anode in an appropriate electrolyte, generally based on nitric acid and containing a copper inhibitor, such as phosphate ions. One way to shorten the silver reduction operation would be to precede it with a mechanical silver removal operation which would aim to reduce its residual thickness without however reaching the copper. This operation would also have the advantage of homogenizing this thickness and removing the various surface impurities (in particular metal residues) which could locally slow down the start of dissolution. We would still avoid being still dissolving the silver in certain areas of the shell even when in other areas the copper has already been exposed.
Toutefois, la méthode de désargenture par voie électrolytique présente l'inconvénient de nécessiter pour sa mise en œuvre une solution spéciale, incompatible pour des raisons de toxicité avec les autres opérations effectuées dans l'atelier d'argenture-désargenture des viroles où on utilise par ailleurs des solutions cyanurées. Les inventeurs préconisent donc de pratiquer la restauration du revêtement d'argent de la virole par recharge directe dans un bain d'argenture (avantageusement celui qui a servi à la première argenture précédemment décrite), sans obligation d'éliminer complètement ou presque complètement le revêtement d'argent résiduel. Une telle façon de procéder est possible, car il est aisé de déposer électrochimiquement une nouvelle couche d'argent sur une couche d'argent plus ancienne et d'obtenir une bonne adhérence de la nouvelle couche sur l'ancienne, alors que cela n'est pas envisageable pour le nickel. D'une part cela simplifie considérablement la gestion des matières de l'atelier de conditionnement des viroles, et d'autre part cela raccourcit leur durée de maintenance, et donc d'immobilisation. De plus, la recharge en argent, telle qu'elle est proposée par les inventeurs, ne présente pas les défauts généralement attribués aux autres formes de démétallisation en général et de dénickelage en particulier, en raison de l'alcalinité naturelle du bain d'argenture. Cette alcalinité peut, en effet, être utilisée comme moyen de passivation naturelle de l'infrastructure de la station d'argenture si celle-ci est en acier non revêtu. Un autre avantage de l'invention est de ne jamais nécessiter de porter en situation anodique lesdites infrastructures en acier, ce qui favoriserait leur corrosion et serait préjudiciable à leur pérennité. Un autre avantage de l'argenture de recharge directe par rapport à une désargenture électrochimique presque totale suivie d'une réargenture est d'éviter la dissolution totale de l'argent dans certaines zones préférentielles (telles que les bords de la virole) lors de la désargenture, qui conduirait à des mises à nu localisées du cuivre. De plus, elle rend superflu le renouvellement de l'étape de préargenture. Enfin, l'argenture de recharge effectuée dans des conditions évitant toute dissolution du cuivre de la virole permet de ne pas attaquer la surface de la virole, donc de prolonger sa durée d'utilisation. L'argenture de recharge peut être précédée d'un léger usinage de la couche d'argent usagée, pour homogénéiser son épaisseur et ôter les impuretés qui seraient préjudiciables à l'adhérence de la nouvelle couche d'argent sur l'ancienne.However, the method of silver plating by electrolytic route has the drawback of requiring for its implementation a special solution, incompatible for reasons of toxicity with the other operations carried out in the silver plating-silver plating workshop where ferrules are used. elsewhere cyanide solutions. The inventors therefore recommend practicing the restoration of the silver coating of the shell by direct recharging in a silver plating bath (advantageously that which served for the first silver plating previously described), without obligation to completely or almost completely remove the coating. residual money. Such a procedure is possible, because it is easy to electrochemically deposit a new layer of silver on an older layer of silver and to obtain good adhesion of the new layer to the old, whereas this does not is not an option for nickel. On the one hand it considerably simplifies the management of the materials in the ferrule packaging workshop, and on the other hand it shortens their duration. maintenance, and therefore downtime. In addition, the silver refill, as proposed by the inventors, does not have the defects generally attributed to other forms of demetallization in general and of nickel removal in particular, due to the natural alkalinity of the silver plating bath. . This alkalinity can, in fact, be used as a means of natural passivation of the infrastructure of the silvering station if it is made of uncoated steel. Another advantage of the invention is that it never needs to wear said steel infrastructures in an anodic situation, which would promote their corrosion and would be detrimental to their durability. Another advantage of direct refill silvering compared to almost total electrochemical silvering followed by resilvering is to avoid the total dissolution of silver in certain preferential areas (such as the edges of the shell) during silvering, which would lead to localized exposures of copper. In addition, it makes the renewal of the pre-silvering stage unnecessary. Finally, the refill silvering carried out under conditions avoiding any dissolution of the copper of the ferrule makes it possible not to attack the surface of the ferrule, therefore to prolong its duration of use. The refill silvering can be preceded by a light machining of the used silver layer, to homogenize its thickness and remove impurities which would be detrimental to the adhesion of the new silver layer on the old.
Par rapport à un atelier de nickelage-dénickelage des viroles, un atelier d'argenture des viroles se distinguerait donc en ce qu'il ne comporterait pas nécessairement d'installation pour la dissolution d'un revêtement usagé par voie chimique ou électrochimique. Il serait donc plus économique à construire. Il serait aussi plus économique à exploiter, car il consommerait moins d'électricité: l'argent se dépose trois fois plus vite que le nickel à densité de courant égale, notamment du fait qu'il est monovalent alors que le nickel est bivalent. Cet avantage est toutefois compensé partiellement en ce que, pour obtenir une protection thermique de la virole équivalente avec un dépôt d'argent et un dépôt de nickel, il faut déposer une couche d'argent environ deux fois plus épaisse que la couche de nickel correspondante. Mais en contrepartie, cette couche d'argent offre une protection mécanique de la virole supérieure à la couche de nickel plus mince. Quant aux réactifs, le coût des sels d'argent utilisés n'est, en fait, pas très différent de celui des sels de nickel employés pour le nickelage traditionnel des parois de lingotière. Globalement, le coût d'un revêtement d'argent n'est donc pas très supérieur à celui d'un revêtement de nickel, et surtout la réfection d'une virole usagée de cylindre de coulée est beaucoup plus rapide et économique.Compared with a nickel-nickel-nickel-plating workshop for ferrules, a silver-plating workshop for ferrules would therefore be distinguished in that it would not necessarily include an installation for dissolving a used coating by chemical or electrochemical means. It would therefore be more economical to build. It would also be more economical to exploit, because it would consume less electricity: silver deposits three times faster than nickel with an equal current density, in particular because it is monovalent while nickel is bivalent. This advantage is however partially offset in that, to obtain equivalent thermal protection of the shell with a silver deposit and a nickel deposit, a silver layer must be deposited approximately twice as thick as the corresponding nickel layer. . On the other hand, this layer of silver offers mechanical protection of the shell that is superior to the thinner layer of nickel. As for reagents, the cost of the silver salts used is, in fact, not very different from that of the nickel salts used for the traditional nickel plating of the walls of the mold. Overall, the cost of a silver coating is therefore not much higher than that of a nickel coating, and above all the repair of a used ferrule of a casting cylinder is much faster and economical.
Les effluents cyanures de l'atelier, notamment les eaux de rinçage, peuvent être traités par de l'eau de javel pour détruire les cyanures. Comme l'eau de javel se fabrique aisément par voie électrolytique, on peut traiter ces effluents légèrement chlorurés par électrolyse en continu: on récupère l'argent métallique à la cathode et on détruit directement les cyanures en carbonate d'ammonium sur des anodes di ensionnellement stables. Des solutions simples et économiques peuvent donc être trouvées aux problèmes environnementaux que peut poser l'utilisation de sels de cyanure.Cyanide effluents from the workshop, especially rinsing water, can be treated with bleach to destroy the cyanides. Since bleach is easily produced electrolytically, these effluents can be treated slightly chlorinated by continuous electrolysis: the metallic silver is recovered at the cathode and the cyanides in ammonium carbonate are directly destroyed on anionally stable anodes. Simple and economical solutions can therefore be found to the environmental problems that can arise from the use of cyanide salts.
L'invention trouve particulièrement son application au conditionnement des viroles de cylindres d'installations de coulée continue de l'acier entre cylindres ou sur un cylindre unique, du fait des grandes dimensions et du coût élevé de fabrication de ces pièces, dont il est important de prolonger la vie autant que possible. Mais il va de soi qu'on peut envisager sa transposition aux traitements de parois de lingotières de coulée en cuivre ou alliage de cuivre de toutes formes et formats, destinées à la coulée de tous métaux supportant d'être mis, à l'état liquide, au contact de l'argent dans les conditions de coulée. The invention particularly finds its application to the conditioning of the ferrules of cylinders of continuous casting installations of steel between cylinders or on a single cylinder, because of the large dimensions and the high cost of manufacturing these parts, of which it is important. to extend life as much as possible. But it goes without saying that one can envisage its transposition to the treatments of walls of ingot molds of copper or copper alloy of all shapes and formats, intended for the casting of all metals supporting being put in the liquid state. , in contact with silver under the casting conditions.

Claims

REVENDICATIONS
1) Elément d'une lingotière pour la coulée continue des métaux, comprenant une paroi refroidie en cuivre ou en alliage de cuivre destinée à être mise au contact du métal liquide et comportant sur sa surface externe un revêtement métallique, caractérisée en ce que ledit revêtement est constitué par une couche d'argent.1) Element of a mold for the continuous casting of metals, comprising a cooled wall of copper or copper alloy intended to be brought into contact with liquid metal and comprising on its external surface a metallic coating, characterized in that said coating consists of a layer of silver.
2) Elément de lingotière selon la revendication 1 , caractérisé en ce que ladite paroi est une virole de cylindre pour machine de coulée continue de bandes métalliques minces entre deux cylindres ou sur un cylindre unique. 3) Elément de lingotière selon la revendication 1 ou 2, caractérisé en ce que ladite couche d'argent a été déposée par une méthode électrolytique.2) ingot mold element according to claim 1, characterized in that said wall is a cylinder ferrule for continuous casting machine for thin metal strips between two cylinders or on a single cylinder. 3) ingot mold element according to claim 1 or 2, characterized in that said silver layer has been deposited by an electrolytic method.
4) Procédé de revêtement par une couche métallique de la surface externe d'une paroi refroidie en cuivre ou alliage de cuivre d'un élément de lingotière de coulée continue des métaux, caractérisé en ce qu'on réalise ce revêtement par dépôt d'une couche d'argent sur ladite surface.4) A method of coating with a metallic layer the external surface of a wall cooled in copper or copper alloy of a mold ingot element for continuous casting of metals, characterized in that this coating is produced by depositing a silver layer on said surface.
5) Procédé selon la revendication 4, caractérisé en ce que ladite couche d'argent est déposée par une méthode électrolytique.5) Method according to claim 4, characterized in that said silver layer is deposited by an electrolytic method.
6) Procédé selon la revendication 5, caractérisé en ce qu'il est appliqué à une paroi en cuivre ou alliage de cuivre nue, et en ce qu'il comprend successivement les étapes suivantes:6) Method according to claim 5, characterized in that it is applied to a wall of copper or bare copper alloy, and in that it successively comprises the following steps:
- un dégraissage de la paroi;- degreasing of the wall;
- un décapage de la paroi en milieu acide oxydant;- stripping of the wall in an oxidizing acid medium;
- une opération de préargenture de la paroi, celle-ci étant placée en cathode dans un bain d'électrolyse constitué par une solution aqueuse de cyanure d'argent et de cyanure de métal alcalin, de manière à déposer une couche d'argent de quelques μm d'épaisseur;- a pre-silvering operation on the wall, the latter being placed as a cathode in an electrolysis bath consisting of an aqueous solution of silver cyanide and alkali metal cyanide, so as to deposit a silver layer of a few μm thick;
- une opération d'argenture de la paroi, celle-ci étant placée en cathode dans un bain d'électrolyse constitué par une solution aqueuse de cyanure d'argent, de cyanure d'un métal alcalin, d'hydroxyde d'un métal alcalin et de carbonate d'un métal alcalin.- a silver plating operation on the wall, this being placed as a cathode in an electrolysis bath consisting of an aqueous solution of silver cyanide, cyanide of an alkali metal, hydroxide of an alkali metal and carbonate of an alkali metal.
7) Procédé selon la revendication 6, caractérisé en ce qu'il comprend également une opération d'avivage de la paroi entre le décapage et la préargenture.7) A method according to claim 6, characterized in that it also comprises an operation of brightening the wall between pickling and pre-silvering.
8) Procédé de restauration d'un revêtement d'argent déposé sur la surface externe d'une paroi en cuivre ou alliage de cuivre d'un élément d'une lingotière de coulée continue des métaux, caractérisé en ce qu'on laisse subsister sur ladite paroi une couche d'argent résiduelle, et en ce qu'on procède à une réargenture de ladite couche en plaçant ladite paroi en cathode dans un bain d'électrolyse contenant un sel d'argent. 9) Procédé selon la revendication 8, caractérisé en ce que ledit bain d'électrolyse est constitué par une solution aqueuse de cyanure d'argent, de cyanure d'un métal alcalin et de carbonate d'un métal alcalin8) A method of restoring a coating of silver deposited on the external surface of a wall of copper or copper alloy of an element of a mold for the continuous casting of metals, characterized in that it is left to remain on said wall a layer of residual silver, and in that a silvering of said layer is carried out by placing said wall as a cathode in an electrolysis bath containing a silver salt. 9) Method according to claim 8, characterized in that said electrolysis bath consists of an aqueous solution of silver cyanide, cyanide of an alkali metal and carbonate of an alkali metal
10) Procédé selon la revendication 8 ou 9, caractérisé en ce que, préalablement à la réargenture, on procède à un léger usinage de la couche d'argent résiduelle sans l'ôter dans sa totalité.10) Method according to claim 8 or 9, characterized in that, prior to resilvering, a slight machining of the residual silver layer is carried out without removing it in its entirety.
1 1) Procédé de restauration d'un revêtement d'argent déposé sur la surface externe d'une paroi en cuivre ou alliage de cuivre d'un élément d'une lingotière de coulée continue des métaux, caractérisé en ce qu'on procède à une désargenture partielle ou totale de ladite paroi en plaçant ladite paroi en anode dans un bain d'électrolyse à base d'acide nitrique et contenant un inhibiteur du cuivre, et en ce qu'on procède ensuite à une réargenture de ladite paroi ou de la couche d'argent résiduelle en plaçant ladite paroi en cathode dans un bain d'électrolyse constitué par une solution aqueuse de cyanure d'argent, de cyanure d'un métal alcalin et de carbonate d'un métal alcalin.1 1) Method for restoring a silver coating deposited on the external surface of a copper or copper alloy wall of an element of a mold for the continuous casting of metals, characterized in that one proceeds to partial or total silvering of said wall by placing said anode wall in an electrolysis bath based on nitric acid and containing a copper inhibitor, and in that a subsequent silvering of said wall or residual silver layer by placing said cathode wall in an electrolysis bath consisting of an aqueous solution of silver cyanide, cyanide of an alkali metal and carbonate of an alkali metal.
12) Procédé selon l'une des revendications 6 à 1 1, caractérisé en ce qu'au cours de l'opération d'argenture ou de réargenture, on crée un gradient de température entre la paroi et le bain d'électrolyse en refroidissant la paroi12) Method according to one of claims 6 to 1 1, characterized in that during the silvering or resilvering operation, a temperature gradient is created between the wall and the electrolysis bath by cooling the wall
13) Procédé selon l'une des revendications 6 à 12, caractérisé en ce que lors de l'opération d'argenture ou de réargenture, on utilise une source de courants transitoires. 13) Method according to one of claims 6 to 12, characterized in that during the silvering or resilvering operation, using a source of transient currents.
EP97930592A 1996-07-11 1997-06-26 Element of a continuous metal casting ingot mould with a copper or copper alloy cooled wall comprising on its external surface a metal coating, and method of coating Expired - Lifetime EP0910489B1 (en)

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FR9608658A FR2750903B1 (en) 1996-07-11 1996-07-11 ELEMENT OF A LINGOTIERE FOR THE CONTINUOUS CASTING OF METALS, COMPRISING A COOLED WALL IN COPPER OR COPPER ALLOY HAVING A METAL COATING ON ITS EXTERNAL SURFACE AND METHOD FOR COATING THE SAME
FR9608658 1996-07-11
PCT/FR1997/001139 WO1998002263A1 (en) 1996-07-11 1997-06-26 Element of a continuous metal casting ingot mould with a copper or copper alloy cooled wall comprising on its external surface a metal coating, and method of coating

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TW438911B (en) 2001-06-07
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ES2148994T3 (en) 2000-10-16
GR3034001T3 (en) 2000-11-30
ATE192951T1 (en) 2000-06-15
JP2000514361A (en) 2000-10-31
AU710657B2 (en) 1999-09-23
KR20000022396A (en) 2000-04-25
CN1072047C (en) 2001-10-03
ZA975970B (en) 1998-01-30
WO1998002263A1 (en) 1998-01-22
FR2750903B1 (en) 1998-09-18
RO119994B1 (en) 2005-07-29
CA2258927A1 (en) 1998-01-22
BR9710229A (en) 1999-08-10
DE69702064T2 (en) 2001-01-11
TR199900041T2 (en) 1999-06-21
DK0910489T3 (en) 2000-10-09
PT910489E (en) 2000-10-31
DE69702064D1 (en) 2000-06-21
SK299A3 (en) 1999-05-07
AU3448897A (en) 1998-02-09
FR2750903A1 (en) 1998-01-16
EP0910489B1 (en) 2000-05-17
PL331180A1 (en) 1999-06-21
RU2181315C2 (en) 2002-04-20

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