Method for forming a peripherally-coated curved copper rod

Abstract

The present invention relates to a method for forming a peripherally-coated curved copper rod (9) for electrowinning anodes that prevents the rod coatings from detaching due to folding and bending, and prevents the use of multiple injection moulds or matrices for every conductive bar design.

Description

[0001] METHOD FOR FORMING A PERIPHERALLY COATED CURVED COPPER BAR

[0002] DESCRIPTIVE MEMORY

[0003] TECHNICAL FIELD

[0004] The present invention is developed in the field of electrowinning or electrorefining of high purity metals and specifically relates to a method or process for obtaining a curved anode copper bar by bending it from a straight bar, in which said straight bar has been previously treated to increase its roughness and coated to improve its conductivity and corrosion resistance.

[0005] DESCRIPTION OF PRIOR ART

[0006] When forming a copper bar coated peripherally with a lead-antimony alloy, a different injection die must be used for each bend radius, depending on the bar's design. It may be, for example, horn-shaped, since bend radii are never the same. In order to reduce the need for injection dies with different characteristics tailored to the design of each bar, the coated copper bar can be bent using a hydraulic press. However, although the use of a hydraulic press allows the bar to be bent, this process has the disadvantage of causing the lead alloy layer injected into the radius areas to peel off.

[0007] In the state of the art, we can cite patent CL 54299, which discloses a coating method or process for the manufacture of anodes, in which the bar is subjected to a pre-coating with an alloy composed mainly of lead and silver. With this pre-coating and with the hot copper bar, said copper bar is introduced into one of several molds suitable for the various shapes that the bar can have, and through injection or a similar method, the copper bar is peripherally coated with a lead-antimony alloy in which said suitable mold can have different shapes depending on the specifications of the bar corresponding to the final shape it will have, considering its radii of curvature to subsequently be joined to a lead plate.

[0008] To solve the problem posed, a method is provided that allows increasing the roughness of the bar surface by means of a surface treatment, thus obtaining a greater degree of adhesion, which is sufficient for a straight coated copper bar to be bent without the injected coating alloy coming off, using a single injection mold for any radius of curvature required for the straight bar.

[0009] SUMMARY OF THE INVENTION

[0010] The present invention discloses a method for forming or obtaining a coated curved copper bar that is obtained from a straight copper bar that prevents the detachment of the coatings from the bar due to bending or curving, allowing to reduce the number of injection dies for this purpose, in which said method considers subjecting a straight copper bar to a surface treatment to increase its roughness, subsequently to a pre-coating by immersion welding in a molten bath of an alloy composed of lead and silver, then the straight bar with the pre-coating is introduced into an injection die with a mold for a straight bar where a peripheral coating of the bar is carried out with a lead-antimony alloy.Finally, the bar is removed with the pre-coating and peripheral coating and placed on a hydraulic table to mechanically form the copper bar with the pre-coating and peripheral coating using a hydraulic press so that it is bent to the required bending radii.

[0011] BRIEF DESCRIPTION OF THE FIGURES

[0012] Figure 1 A shows schematically the straight copper bar entering the Pb-Ag pre-coating bath.

[0013] Figure 1 B shows a schematic representation of the already coated straight copper bar coming out of the Pb-Ag pre-coating bath.

[0014] Figure 2A shows schematically the straight bar with the Pb-Ag pre-coating entering the injection die.

[0015] Figure 2B shows schematically the straight bar with the Pb-Ag pre-coating in the injection die for the peripheral Pb-Sb coating.

[0016] Figure 2C shows schematically the straight bar with the Pb-Ag pre-coating as it exits the injection die already coated with the Pb-Sb peripheral coating.

[0017] Figure 3A shows a schematic representation of the straight bar with the Pb-Ag pre-coating and the Pb-Sb peripheral coating installed between the press and the bending die. Figure 3B shows a schematic representation of the straight bar with the Pb-Ag pre-coating and the Pb-Sb peripheral coating during the bending process between the press and the bending die.

[0018] Figure 3C shows the finished bar with the Pb-Ag pre-coating and the Pb-Sb peripheral coating already bent at the corresponding angles.

[0019] DETAILED DESCRIPTION OF THE INVENTION

[0020] The invention relates to a method or process for forming or obtaining an anode-conducting copper bar having a lead-antimony coating that does not require the use of multiple molds or injection dies for each conductor bar design with different radii of curvature. The objective of the invention is to provide a method for forming a coated curved conductive copper bar that prevents the detachment of the coatings from the bar due to bending or curving, allowing a horn-type conductive bar to be obtained with different radii of curvature, avoiding the use of multiple molds or injection dies for each conductor bar design.

[0021] The method consists of subjecting a straight copper conductor bar (1 ) to shot peening or intense sanding, to increase the roughness of the surface of the bar, until obtaining a surface roughness of between 0.1 mm to 0.3 mm, preferably 0.15 mm. It has been discovered that the increase in roughness as indicated allows obtaining an unbeatable adhesion between a pre-coating weld of the copper bar and a peripheral coating, being essential for this copper bar assembly with pre-coating and peripheral coating, to withstand the stress of hot bending necessary for forming the angles (10) of horn-type anode bars.

[0022] The immersion provided by the pre-coating occurs in a molten bath of a lead-silver based alloy (2) obtaining in a first stage a straight copper bar (3) with a lead-silver pre-coating, immediately after and with the pre-coated straight copper bar (3) it is introduced into an injection die (5) with a mold suitable for a straight bar (6) and by means of injection or another similar mechanism the pre-coated straight copper bar (3) is coated with a lead-antimony alloy, then the straight copper conductor bar peripherally coated with the lead-antimony alloy (4), still hot, is placed on a hydraulic table (1 1) with a press (7) and a dolly (8) to produce the characteristic bend of a horn-type bar and then obtain a curved copper bar (9) where its curved ends (10) have the radii of curvature adjusted to the required specifications.Finally, the curved copper bar (9) is removed from the hydraulic table (1 1 ) and placed on an assembly table to continue the anode assembly stages.

[0023] According to the above, the method for forming a coated curved conductive copper bar that prevents the detachment of the bar's coatings due to bending or curving, comprises the steps of: a) providing a straight copper bar (1 ) for anode; b) subjecting the straight copper bar (1 ) to a surface treatment to increase its roughness; c) subjecting the straight copper bar (1 ) to a pre-coating by immersion in a molten bath of an alloy composed of lead and silver (2), to obtain a straight copper bar with a pre-coating of lead and silver (3);(d) introducing the straight copper bar with the lead-silver pre-coating (3) just coated into an injection die (5) with a straight bar mold (6) and carrying out a peripheral coating of the bar with a lead-antimony alloy, to obtain a straight copper bar peripherally coated with the lead-antimony alloy (4) and with the lead-silver pre-coating; (e) mechanically shaping the straight copper bar with the lead-silver pre-coating and the peripheral lead-antimony coating, still hot, on a hydraulic table with a press (7) and a dolly (8) to bend the ends of the bar until obtaining a copper bar with curved ends (10) with the required radii of curvature;

Claims

CLAIMS 1. A method for forming a peripherally coated curved copper bar (9) for electrowinning anodes, which prevents the coatings from coming off the bar due to bending or curving, and avoids using multiple injection molds or dies for each conductive bar design, CHARACTERIZED in that it comprises the steps of: a) providing a straight copper bar (1 ) for the anode; b) subjecting the straight copper bar (1 ) to a surface treatment to increase its roughness; c) subjecting the straight copper bar (1 ) to a pre-coating by immersion in a molten bath of an alloy composed of lead and silver (2); d) introducing the straight copper bar with the pre-coating of lead and silver (3), freshly coated, into an injection die (5) with a straight bar mold (6) and performing a peripheral coating of the bar with a lead-antimony alloy;e) mechanically forming the straight copper bar with the peripheral lead-antimony coating (4), still hot, on a hydraulic table with a press (7) and a dolly (8) to bend the ends of the bar until obtaining a copper bar with curved ends (10) with the required radii of curvature.

2. The method for obtaining a curved copper bar according to claim 1, CHARACTERIZED in that the surface treatment consists of shot peening.

3. The method for obtaining a curved copper bar according to claim 1, CHARACTERIZED in that the surface treatment consists of intense sanding.

4. The method for obtaining a curved copper bar according to claim 1, CHARACTERIZED in that the roughness of the increased roughness surface is between 0.1 mm and 0.3 mm, preferably 0.15 mm.

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