Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D1/00—Electroforming
  • C25D1/04—Wires; Strips; Foils

Definitions

• the present invention relates to an installation for the continuous production of an extra-thin metal sheet by electrolytic deposition
• the electrodeposition technique has been known and used for a long time to form thin metal coatings on substrates having the most diverse forms. Continuous deposition is particularly suitable for elongated products, of great length, such as strips or wires, which can pass through to the deposition device. This technique makes it possible to produce adherent coatings, which remain permanently at the surface of the sub stratum, or non-stick coatings, which can be detached from _? _
• patent LU-A-86.119 by the same applicant, there is known a device for depositing an electrolytic coating, in particular not adhered, on a rotary cathode.
• This device comprises an anode which is designed so as to ensure a high turbulence of the electrolyte in the space between the anode and the cathode, by practicing an electrolyte supply perpendicular to the plane of the cathode and without using any excessive motor pressure.
• the average thickness and the width of the extra-thin sheet to be produced are determined according to the needs of the users and therefore vary, for a given installation, within relatively narrow limits.
• the increase in production implies an increase in the speed of the substrate which in turn leads to an increase in the length, and therefore in the size, of the depositing device, in order to maintain the same duration. deposit.
• the size of the deposition device can, to a certain extent be minimized by resorting to some special precautions, such as the use of an anode making it possible to operate with high current densities and the use of a Electrolyte flow and current density as high as possible.
• some special precautions such as the use of an anode making it possible to operate with high current densities and the use of a Electrolyte flow and current density as high as possible.
• it remains necessary to increase the net length of deposit that is to say the length of the zone where the electrodes are actually opposite one another.
• This increase is obtained by a simultaneous increase in the length of the anode and of the cathode in the direction of travel of the substrate.
• the length of the anode can be easily increased by juxtaposing several devices such as those described in the brief LU-A-86.119 already cited.
• the desired increase in the net deposition length implies a substantial increase in the diameter of the drum, which is limited, and practical, for reasons of manufacture, assembly and size. sharply.
• a mobile cathode constituted by a metal belt rotating around two parallel rollers.
• Such a belt can have a sufficient length for the deposition to be carried out completely on a single belt, regardless of the speed thereof. It overcomes the aforementioned drawbacks of rotary drum cathodes, but it gives rise to other difficulties related in particular to the length and speed of the belt. In particular, one can mention the difficulty of guiding a belt of great length and the need to compensate for the deformation in chain net, which are further complicated by the aggressive nature of the ambient environment. Such an installation is also faced with problems of sealing and braking of the belt relative to 1 r ELECTRICITY SUPPLY belt by brushes.
• the object of the present invention is to provide an installation for the continuous manufacture of an extra-thin metal sheet by electrolytic deposition of a non-adherent coating on a mobile substrate followed by the detachment of this coating, an installation which avoids various aforementioned drawbacks and of ensuring a high production of extra-thin sheet.
• the installation which is the subject of the present invention is based on the use of anodes of the type described in the aforementioned patent LU-A-86,119 and of a mobile cathode moving opposite these anodes.
• the installation which is the subject of the present invention for the manufacture of an extra-thin metal sheet by electrolytic deposition on a movable cathode and subsequent separation of the deposit and the cathode, which comprises at least one anode comprising a plate pierced with a first series of orifices connected to means for supplying electrolyte and a second series of orifices connected to means for discharging the electrolyte, is characterized in that : a, the movable cathode is constituted by a metal belt stretched between two parallel rollers, preferably horizontal; (b) at least one of said rollers is motorized in order to put the belt in rotation around the two rollers:
• a first plurality of said anodes is disposed opposite a portion of the length of a first strand of said belt;
• (f) means for adjusting the speed of said metal belt, the flow rates for supplying and discharging the electrolyte. as well as the intensity of the electric current.
• the device of the invention comprises means for rinsing the extra-thin sheet, respectively means for drying this extra-thin sheet, which are located before the device for separating said sheet.
• sheet and your mobile cathode the device can also include an installation for subjecting the sheet to a treatment causing an increase in its carbon content.
• said cathode is constituted by a titanium belt, preferably polished.
• the surface condition of the method strongly influences the detachment ability and the quality of the extra-thin sheet produced, and it is advantageous in this regard that the cathode has an active surface as polished as possible.
• the active surface of the belt is that which receives the electrodeposition.
• the second of said preferably horizontal rollers is also equipped with a drive motor.
• the device of the invention comprises a second plurality of anodes arranged opposite a portion of the length of the second strand of said belt, the plate of said anodes being electrically connected to the positive terminal d '' a source of direct electric current.
• said first and second pluralities of anodes are arranged opposite portions of substantially equal length of the respective strands of said belt, from a first of said horizontal rollers, 1 ′ assembly comprising said first roller, said first and second pluralities of anodes and the corresponding portions of the strands of the belt is enveloped by a sealed enclosure, the second of said rollers is located outside said enclosure and said enclosure includes liquid tight for the entry and exit of said belt.
• At least one anode is constituted by a parallelepipedic box whose wall located opposite the cathode is made of an electrically conductive material, preferably in graphite, the other walls of said box being preferably made of an electrically insulating material which is chemically inert with respect to the electrolyte.
• the means for electrically connecting an anode comprise copper bars connected to the plate of said anode, preferably on both sides of the width of said plate.
• the electrical connection means of said metal belt comprise brushes, which are preferably immersed in the electro ⁇ lyte.
• the means for rinsing, respectively drying, the extra-thin metal sheet comprise devices for spraying water, respectively air, in the direction of said sheet.
• Fig. 1 shows a general view of this particular embodiment
• Fig. 2 illustrates the circuit of the electrolyte in this embodiment
• Fig. 3 illustrates a particular variant of the installation comprising a carburizing device.
• FIG. 1 shows a general view, in length, of a particular embodiment of the installation of the invention.
• This installation includes a mobile cathode in the form of a metal belt (1, stretched between two parallel horizontal rollers (2,3).
• the edges of the belt (1) can be hidden, on the anode side, by means of the moven an adequate coating so as to give the extra-thin sheet the desired width.
• the rollers are driven in rotation by motors, not shown, and their direction of rotation is indicated by a curved arrow.
• the metal belt (1) thus defines an upper strand (4) which, as will be explained below, is the input strand, and a lower strand (5) or output strand
• the installation also comprises anodes of the type described in the patent LU-A-86.119 cited above, in which the wall pierced by two series of orifices is a flat graphite plate
• These anodes are divided into two groups, namely an upper group (6) in which the anodes are positioned from so that their graphite plates respe ctives are opposite and parallel to the outer face of the upper strand (4 ⁇ of the belt, and a lower group (7) in which the anodes are positioned so that their respective graphite plates are opaque and parallel to the outer face of the lower strand N of the belt.
• the metal belt (1) is not partially immersed in the electrolyte and it can therefore be considered that the installation for manufacturing an extra-thin metal sheet consists of two separate parts. , despite the physical continuity of the belt (1).
• the submerged part of the installation comprises: a portion of the belt (1), said portion having a constant length, but being constantly renewed as a result of the movement of the belt; - the two groups of anodes [6, 7):
• the non-submerged or aerial part of the installation includes:
• the submerged part of the installation is surrounded by a sealed enclosure (8), which includes airlocks for entering and leaving the belt.
• a polarization electrode making it possible to eliminate any chemical attack on the extra-thin sheet by the electro ⁇ lyte the passage from the upper group (6) to the lower group (7) of the anodes. This arrangement also makes it possible to avoid the manufacture of cylindrical anodes.
• This submerged roller (3) must have a diameter large enough to transmit to the belt the torque necessary for its rotation and to minimize the risk of rupture of the belt by fatigue.
• the supply of both an electrolyte and an electric current to the anodes of the two groups mentioned above can be carried out either individually or by cells grouping together any number of anodes.
• the various power supplies will be described with reference to a cell, it being understood that such a cell could have only one anode.
• the electrical supply of a cell is ensured by means of a set of copper bars, known per se, connected to the graphite plate, on both sides of its width: this arrangement has the effect to reduce the ohmic losses in the graphite plate and thus to minimize the variations in the current density liable to cause variations in the thickness of the deposit along the width of the belt.
• the electric supply to the cathode is carried out by means of brushes immersed in the electrolyte and distributed over the "internal" surface of the belt 1;, opposite the groups of anodes.
• the brushes are submerged eliminates the need for sealing joints between fixed parts and moving parts.
• the electrolyte acts as a lubricant and thus reduces the frictional force applied to the belt.
• the electrolyte reduces the contact resistance between the cathode and the brushes and thus contributes to improving the electrical efficiency of the installation.
• the electrolyte circuit will be described later, with reference to FIG. 2.
• the non-submerged roller (2) has a diameter equal to that of the submerged roller (3). It ensures the transmission of half of the torque necessary for driving the belt, as well as guiding the belt in the transverse direction.
• the means for rinsing and / or drying the extra-thin metal sheet are located before the device separating said sheet and the belt, 1).
• This arrangement makes it possible to carry out the important and delicate rinsing and 'or drying operations while the extra-thin sheet still adheres to the belt: this thus reduces the risks of degradation or tearing of this sheet.
• the devices used for this purpose are known per se.
• the installation includes rinsing means (9) for example by spraying water hot, possibly followed by drying means (10) such as air blowing apparatus, hot or cold.
• the detachment of the extra-thin sheet is carried out by means of a motorized pe ⁇ tit roller (11), placed approximately at the height of the axis of rotation of the non-submerged roller (2).
• FIG. 2 illustrates the circuit of the electrolyte in an installation of the type represented in FIG. 1. As indicated above, we are again referring here to an a ⁇ odic cell.
• FIG. 2 which results from a cross section along the plane II of FIG. 1, the upper (4) and lower (5) strands of the belt have been shown diagrammatically, as well as the graphite plate of an anode of each of the upper (6) and lower (7) groups.
• the present installation comprises an electrolyte circuit in which the pressure drops are low.
• Each pair of superimposed cells, one belonging to the upper group ⁇ " 4, 6) and the other to the lower group (5, 7) is supplied with electrolyte by a pump (12) taking the liquid from a collection basin ( The pump (12) sends the electrolyte through the conduits (14) and (15) which supply the first series of anode openings (6) and (7) respectively.
• the collection basin (13) is located directly below the lower group (7) of anodes and it extends at least over the entire length of the submerged part of the installa ⁇ tion.
• the electrolyte discharged from the rear face of the cells of the lower group (7) falls directly into the collection basin (13).
• the electrolyte discharged through the rear face of the cells of the upper group (6) is collected by a channel (16) of large section which runs along the immersed part of the installation over its entire length and which brings the electrolyte back into the collection basin (13) by means of a cascade (17) bypassing the submerged roller (3).
• the installation also comprises, at the entrance to its submerged part, pinch rollers (18) which make it possible to prevent the belt (1) from twisting in the deposition section.
• the device of the invention can advantageously be equipped with means for, after separation of the iron-based sheet and the movable cathode, subjecting said iron-based sheet to a treatment causing an increase in its carbon content; according to the invention, this treatment is advantageously constituted by a gas carburizing operation.
• Such treatment by gas carburizing has proven to be particularly advantageous for increasing the carbon content of a sheet.
• iron-based initial produced by electrolytic deposition.
• the tests carried out by the Applicant have shown, in an absolutely unexpected manner, that the rate of cementation of such a sheet was particularly high, provided that the conditions of the treatment were judiciously chosen.
• This high cementation speed which could in particular be due to the purity of the initial sheet, makes it possible to achieve the desired degree of cementation in a very short time, perfectly compatible with a continuous manufacturing process.
• the means for applying the treatment in ques ⁇ tion comprise a heating oven up to a temperature between 900 ° C and 1050 ° C, under a fuel atmosphere, a zone for maintaining in this temperature range and under this atmosphere for a period which does not exceed 5 min., and a cooling zone with a speed of 5 ° C / s to 20 ° C / s in the temperature range from 800 ° C to 600 ° C, then a cooling zone to room temperature.
• the installation can also include at least one device for covering said sheet with a protective metal layer, with a flash heating step to cause the formation of an intermediate layer of intermetallic alloy between said sheet and the protective layer.
• the device of the invention as just described in the above variant can also be equipped with means for coating the sheet with a protective film consisting of an oxide such as chromium oxide or an organic substance such as a lacquer, a resin or a varnish.
• Fig. 3 shows a variant of the installation of FIG. 1, in which a device is provided for cementing the extra-thin metal sheet, after it has been detached from the movable cathode.
• this device (19) Downstream of the installation (1) described in detail above, is located a device (19) intended to cause an increase in the carbon content of the extra-thin sheet.
• this device '19) is constituted by a gas carburizing furnace, where the extra-thin sheet is exposed to a burning atmosphere, for example CH, at a high temperature.
• This device (19) can be followed by other coating installations such as a dip galvanizing installation (20) or a tinning installation (21). Finally, a finishing device (22), such as an installation for depositing a protective coating by chromating, lacquering or the like, can also be installed downstream.
• a finishing device (22) such as an installation for depositing a protective coating by chromating, lacquering or the like, can also be installed downstream.
• the installations 20, 21 and 22 are, in themselves, well known in the art and do not require a detailed description. It is nevertheless advisable to limit the tensile force exerted in these installations, in order to take account of the relatively low tensile strength of the extra-thin sheet.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating Methods And Accessories (AREA)
• Electrolytic Production Of Metals (AREA)

Applications Claiming Priority (4)

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Citations (3)

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• 1988
  • 1988-02-15 WO PCT/BE1988/000004 patent/WO1988006195A1/fr unknown
  • 1988-02-15 JP JP50238288A patent/JPH01502204A/ja active Pending
  • 1988-02-15 DE DE8888870017T patent/DE3864850D1/de not_active Expired - Lifetime
  • 1988-02-15 EP EP19880870017 patent/EP0279803B1/de not_active Expired - Lifetime

Patent Citations (3)

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