Title of Invention | PROCESS FOR ELECTROLYTIC COATING OF A STRAND CASTING MOULD |
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Abstract | PROCESS FOR ELECTROLYTIC COATING OF A STRAND CASTING MOULD. Process for electrolytically coating a mould in which internal surfaces (4) thereof demarcate a mould (2) cavity (3) having a generally rectangular cross-sectional shape when viewed in an axial direction, comprising: positioning an electrode (7) in the mould cavity (3); whereby the electrode comprises an insoluble electrode having a same cross-sectional shape as the cross- sectional shape of the mould (2). sealing off the entire mould cavity (3) with a head piece and a base piece positioned externally to said mould cavity (3) with sealing elements (8, 9) on both front faces at the ends of the mould (2), whereby the head piece (5) and the base piece (6) each have at least one opening forming an intake and a discharge opening for introducing and discharging electrolyte (25), providing an electrical connection between the electrode (7) and the mould (2); pumping electrolyte (25) by a pump into the mould cavity and back to the pump (16), wherein the electrolyte (25) is a sole supply of coating material; providing a current between the electrode (7) and the mould cavity (3); and changing the current direction periodically, wherein the current-direction is changed intermittently to pulse deposit the coating material, and, Coating the mould cavity (3) over its entire length at one time with a substantially uniform thickness including the four corner regions of the mould cavity. |
Full Text | Process for electrolytic coating of a strand casting mould The invention relates to a process for electrolytic coating of a strand casting mould according to the precharacterizing clause of claim 1. Strand casting moulds are subject to a constant abrasive wear during casting, so that the mould cavity and therefore also the cross-section dimensions of the cast strands become ever larger. After a certain number of working cycles, the particular strand casting mould must therefore be replaced by a new one or reworked. Various methods for reworking the moulds for the purpose or re-establishing the original geometry of the mould cavity or the intended dimensions of the mould cavity are known. Reworking can be carried out, for example, by explosion forming of the mould on a mandrel. Not only is this method relatively complicated, expensive and environment- polluting, it also means a deformation of the external shape of the mould, which in turn involves an enlargement of a water gap present on the periphery of the mould and as a result an adverse influence on the cooling of the mould. Other known pressing processes for reshaping the moulds in which the mould is first compressed from the outside and the mould cavity is then brought to the original internal dimensions by internal grinding or internal milling also have the latter disadvantage. Finally, it is known from EP-A-0 282 759 to bring the mould cavity of a strand casting mould back to the intended dimensions by electrolytic coating of the internal surfaces which demarcate the mould cavity. In this generic process, the mould, which serves as the cathode, is immersed in an electrolyte bath (Cu sulfate bath) together with a perforated anode basket which is positioned in the mould cavity and is filled with soluble copper pieces (cubes, balls, discs). When a direct current is connected, the copper is separated out of the electrolyte bath and deposited on the mould surfaces, the copper separated out of the electrolyte bath being replaced by the dissolved anode copper. A relatively low current density, for example of about 15 A/dm2, is achieved in this dipping electrolytic process. From experience, in the case of electrolytic dip-coating of mould cavities which are usually polygonal in cross-section there is the risk that the layer is of insufficient thickness in the corner regions, that is to say the layer thickness is only about 1/4.to 1/10 of that in the other regions. This non-uniform layer build-up can be only partly remedied with special anode geometries. This means a further mechanical reworking is necessary. With the production of thick layers there is furthermore the risk that corner bridges with enclosed cavities are formed, as a result of which the mould becomes unusable. A further disadvantage of electrolytic dip-coating is that the external surfaces of the mould must be covered with a material which is inert towards the electrolytic treatment. The present invention is based on the object of proposing a process of the abovementioned type with which the intended dimensions of the mould cavity can be achieved or re- achieved as simply as possible even in strand casting moulds having a mould cavity of polygonal cross-section, without problem zones arising in the corner regions of the mould cavity. Furthermore, the strand casting moulds to be coated should as far as possible remain unchanged in their external dimensions. This object is achieved according to the invention by a process having the features of claim 1. Preferred further embodiments of the invention form the subject matter of the dependent claims. With the process according to the invention, in which the electrolyte flows in a hydrodynamically controllable manner through the mould cavity of the strand casting mould which forms the cathode, using an insoluble anode, the electrolyte alone supplying the coating material, it is possible to apply both a thin layer of the wear-resistant material with dimensional accuracy, without reworking being necessary, and a thick layer (with which at most minimal reworking arises), since the layer build-up is uniform without corner weaknesses. It is a considerable advantage of the process according to the invention that during the electrolytic coating only the internal surfaces of the mould cavity come into contact with the electrolyte and the external surfaces of the strand casting mould therefore do not have to be covered. Furthermore, intermittent anode/cathode pole reversal is also possible, with which a pulsed deposition of the coating material can be achieved and the coating influenced. It is to be emphasized as a particular advantage that the mechanical properties, such as, for example, the hardness, and in particular also the structural formation of the coating can be kept largely uniform over the entire region. The coating can be achieved more rapidly than with the conventional processes. Gristle formation on the coated surfaces can also be largely prevented. The invention is explained in more detail in the following with the aid of the drawing. In the drawing: Fig. 1 shows a schematic diagram of the process according to the invention. Fig. 1 shows, in purely schematic form, a device 1 which is envisaged for electrolytic coating of internal surfaces 4 which demarcate a mould cavity 3 of a strand casting installation 2 with a wear-resistant coating material for the purpose of achieving or re-achieving intended mould cavity dimensions. The mould cavity 3 can have, for example, a rectangular or square cross-section and can thus be demarcated by 4 internal surfaces. However, the mould could also be a mould having another mould cavity cross- section (e.g. circular, polygonal, longitudinally angled) or a so-called dog bone mould. A head piece and a base piece 5, 6 which are joined to one another via an anode 7 which extends through the mould cavity 3 are assigned to the faces of the strand casting mould 2. Sealing elements 8, 9 on the faces of the strand casting mould 2 seal off the mould cavity 3. The anode 7 is also inserted in a sealing manner in the head piece and base piece 5, 6, cf. seals 13, 14. Both the base piece 6 and the head piece 5 are provided with at least in each case one, preferably with a number of openings 11 and 12 respectively (in fig. 1 in each case one opening 11, 12 is indicated), which form intake and discharge openings for introducing and discharging an electrolyte 25 envisaged for the electrolytic coating into and out of the otherwise tightly closed mould cavity 3, which forms a reactor space. This is pumped from a reservoir container 15 with the aid of a pump 16 in a hydrodynamically controllable manner into the reactor space from the bottom through the base piece 6 and is fed with an overflow (without pressure) on the head piece 5 back to the reservoir container 15 and to the pump 16. The coating material is metered into the electrolyte 25 as oxide from a container 18. For the electrolytic coating, the strand casting mould 2, as the cathode, and the anode 7 with the wings 7' indicated can be connected to a direct current source 2 0 and thereby form a direct current circuit. Either the sealing elements 8, 9 or the seals 13, 14 simultaneously have an electrically insulating action. The anode matches in its cross-section shape the cross-section shape of the mould cavity 3. For polygonal mould cavities, corresponding prismatic anodes are used. The anode is made in particular from a platinum- or mixed ceramic-coated titanium material or from lead. It can also be constructed as a multiple anode. In principle, however, the coating material, such as, for example, copper, nickel or chromium, can also be contained in the anode, in which case it would be provided in a solid or piece form. The process according to the invention is suitable for application of, for example, layers of copper, nickel or chromium. The coating material is supplied by the electrolyte 25 alone. The anode in itself is insoluble. The anodes can be, for example, platinum-coated anodes of titanium, anodes of Pb sheet, coated mixed ceramic and other materials. Methanesulfonic acid, cyanide or sulfuric acid electrolyte types can be used as the electrolytes. Using these high-speed electrolytes, with intensive agitation of the electrolyte a current density of 2 to 4 0 A/dm2 can be achieved. With an efficient hydrodynamic control of the flow of the electrolyte through the reactor space, it is possible to apply both a thin layer of the wear-resistant material with dimensional accuracy, without reworking being necessary, and a thick layer (with which at most minimal reworking arises), since the layer build-up takes place uniformly and without corner weaknesses. The process according to the invention brings considerable advantages in particular in coating with chromium, since precisely in the case of chromium particularly severe corner problems arise during conventional electrolytic coating (layer 5 to 10 times thinner than on the surfaces) and the chromium can be reworked only with grinding. Pulsed deposition of the coating material can also be achieved with the process according to the invention, in which the electrolyte 25 alone supplies the coating material, since in addition to the hydrodynamic control, an intermittent anode/cathode pole reversal is possible and can influence the coating. A considerable advantage of the process according to the invention is that during the electrolytic coating only the internal surfaces of the mould cavity come into contact with the electrolyte 25 and the external surfaces of the strand casting mould therefore do not have to be covered. The anode and/or the strand casting mould could in principle be constructed rotatably about their longitudinal axis, so that rotation during the coating and therefore an improved coating could be rendered possible. Before the coating, the strand casting mould 2 is cleaned by a rinsing process, in particular a cascade rinsing, which is not explained in more detail. It is integrated in a closed system here for the coating and preferably for this rinsing. The strand casting mould is made from a metallic material or composite material, such as copper, aluminium or nickel, from a plastic or composite plastic or from a ceramic material or other materials. A rectifier device can furthermore be provided, by means of which the current direction can be reversed for the purpose of achieving a uniform layer application. If copper is used as the coating material, a commercially available copper oxide, in which the too high chlorine content is reduced by means of a washing/dissolving process, is furthermore used beforehand. Alternatively, the strand casting mould 2 can be coated only in certain regions or more thickly, i.e. with a larger layer thickness, in these regions where a relatively higher degree of wear occurs during operation, for example in the region of the bath surface, where an additional wear occurs in particular due to the covering material. An efficient coating is thus achieved. Such a partial coating can be achieved by partial covering of the anode or by insertion of non-conducting screens or by similar measures. During the coating operation, electromagnetic fields can be generated by magnets, which are not shown in more detail, through which the particles of the coating material can be conducted and. led such that a layer of the same thickness as in the other regions is deposited in certain regions, preferably in the edge regions of the strand casting mould. The invention is described adequately by the above statements. It could of course also be illustrated in other variants. WE CLAIM 1. Process for electrolytically coating a mould in which internal surfaces (4) thereof demarcate a mould (2) cavity (3) having a generally rectangular cross-sectional shape when viewed in an axial direction, comprising: a) positioning an electrode (7) in the mould cavity (3); whereby the electrode comprises an insoluble electrode having a same cross-sectional shape as the cross-sectional shape of the mould (2). b) sealing off the entire mould cavity (3) with a head piece and a base piece positioned externally to said mould cavity (3) with sealing elements (8, 9) on both front faces at the ends of the mould (2), whereby the head piece (5) and the base piece (6) each have at least one opening forming an intake and a discharge opening for introducing and discharging electrolyte (25), c) providing an electrical connection between the electrode (7) and the mould (2); d) pumping electrolyte (25) by a pump into the mould cavity and back to the pump (16), wherein the electrolyte (25) is a sole supply of coating material; e) providing a current between the electrode (7) and the mould cavity (3); and f) changing the current direction periodically, wherein the current-direction is changed intermittently to pulse deposit the coating material, and, g) Coating the mould cavity (3) over its entire length at one time with a substantially uniform thickness including the four corner regions of the mould cavity. 2. Process as claimed in claim 1, wherein copper, nickel or chromium is used as the coating material and is in each case metered into the electrolyte (25) as oxide. 3. Process as claimed in claim 1 or 2, wherein an electrolyte (25) containing methanesulfonic acid, cyanide or sulfuric acid is used. 4. Process as claimed in one of claims 1 to 3, wherein the anode (7) used in insoluble form, which can be also constructed as a multiple anode, is constructed from a platinum- or mixed ceramic-coated titanium material or from lead. 5. Process as claimed in one of claims 1 to 4, wherein the electrolyte (25) is pumped by means of a pump (16) into a reactor space which is surrounded by the internal surfaces (4) of the mould cavity (3) and is closed off at the faces by a base piece and a head piece (6, 5), and is fed from this back to the pump (16). 6. Process as claimed in one of claims 1-5, wherein the anode (7) and/or the strand casting mould (2) are constructed rotatably around their longitudinal axis, so that rotation during the coating is rendered possible. 7. Process as claimed in one of claims 1 to 6, wherein the strand casting mould (2) is cleaned by a rinsing process, in particular a cascade rinsing, before the coating. 8. Process as claimed in one of claims 1 to 7, wherein the strand casting mould (2) is integrated in a closed system for the coating and preferably for the rinsing. 9. Process as claimed in one of claims 1 to 8, wherein the strand casting mould (2) is made from a metallic material or composite material, such as copper, aluminium or nickel, from a plastic or composite plastic or from a ceramic material or other materials. 10. Process as claimed in claim 1, wherein if copper is used, a commercially available copper oxide in which the too high chlorine content is reduced by means of a washing/dissolving process is used beforehand. 11. Process as claimed in one of claims 1 to 10, wherein the strand casting mould (2) is coated only or more thickly in certain regions where a higher wear occurs during operation. 12. Process as claimed in claim 1, wherein the coating material, such as, for example, copper, nickel or chromium, is employed as the anode. 13. Process as claimed in one of claims 1 to 12, wherein during the coating operation the particles of the coating material are conducted by electromagnetic fields such that in certain regions, in particular in the edge regions of the strand casting mould, a layer of the same thickness as in the other regions is deposited. ABSTRACT PROCESS FOR ELECTROLYTIC COATING OF A STRAND CASTING MOULD. Process for electrolytically coating a mould in which internal surfaces (4) thereof demarcate a mould (2) cavity (3) having a generally rectangular cross-sectional shape when viewed in an axial direction, comprising: positioning an electrode (7) in the mould cavity (3); whereby the electrode comprises an insoluble electrode having a same cross-sectional shape as the cross- sectional shape of the mould (2). sealing off the entire mould cavity (3) with a head piece and a base piece positioned externally to said mould cavity (3) with sealing elements (8, 9) on both front faces at the ends of the mould (2), whereby the head piece (5) and the base piece (6) each have at least one opening forming an intake and a discharge opening for introducing and discharging electrolyte (25), providing an electrical connection between the electrode (7) and the mould (2); pumping electrolyte (25) by a pump into the mould cavity and back to the pump (16), wherein the electrolyte (25) is a sole supply of coating material; providing a current between the electrode (7) and the mould cavity (3); and changing the current direction periodically, wherein the current-direction is changed intermittently to pulse deposit the coating material, and, Coating the mould cavity (3) over its entire length at one time with a substantially uniform thickness including the four corner regions of the mould cavity. |
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1809-KOLNP-2004-(08-11-2011)-ABSTRACT.pdf
1809-KOLNP-2004-(08-11-2011)-AMANDED CLAIMS.pdf
1809-KOLNP-2004-(08-11-2011)-CORRESPONDENCE.pdf
1809-KOLNP-2004-(08-11-2011)-DESCRIPTION (COMPLETE).pdf
1809-KOLNP-2004-(08-11-2011)-DRAWINGS.pdf
1809-KOLNP-2004-(08-11-2011)-FORM 1.pdf
1809-KOLNP-2004-(08-11-2011)-FORM 2.pdf
1809-KOLNP-2004-(08-11-2011)-OTHERS.pdf
1809-KOLNP-2004-ABSTRACT 1.1.pdf
1809-KOLNP-2004-AMANDED CLAIMS.pdf
1809-KOLNP-2004-AMANDED PAGES OF SPECIFICATION.pdf
1809-KOLNP-2004-CORRESPONDENCE 1.1.pdf
1809-kolnp-2004-correspondence.pdf
1809-KOLNP-2004-DESCRIPTION (COMPLETE) 1.1.pdf
1809-kolnp-2004-description (complete).pdf
1809-KOLNP-2004-DRAWINGS 1.1.pdf
1809-KOLNP-2004-EXAMINATION REPORT REPLY RECIEVED.pdf
1809-KOLNP-2004-EXAMINATION REPORT.pdf
1809-KOLNP-2004-FORM 1-1.1.pdf
1809-KOLNP-2004-FORM 18 1.1.pdf
1809-KOLNP-2004-FORM 2-1.1.pdf
1809-KOLNP-2004-FORM 3 1.3.pdf
1809-KOLNP-2004-FORM 3-1.1.pdf
1809-KOLNP-2004-FORM 5 1.1.pdf
1809-KOLNP-2004-GRANTED-ABSTRACT.pdf
1809-KOLNP-2004-GRANTED-CLAIMS.pdf
1809-KOLNP-2004-GRANTED-DESCRIPTION (COMPLETE).pdf
1809-KOLNP-2004-GRANTED-DRAWINGS.pdf
1809-KOLNP-2004-GRANTED-FORM 1.pdf
1809-KOLNP-2004-GRANTED-FORM 2.pdf
1809-KOLNP-2004-GRANTED-SPECIFICATION.pdf
1809-KOLNP-2004-OTHERS 1.1.pdf
1809-KOLNP-2004-OTHERS 1.2.pdf
1809-KOLNP-2004-PETITION UNDER RULE 137.pdf
1809-KOLNP-2004-REPLY TO EXAMINATION REPORT.pdf
1809-kolnp-2004-specification.pdf
1809-kolnp-2004-translated copy of priority document.pdf
Patent Number | 252719 | ||||||||
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Indian Patent Application Number | 1809/KOLNP/2004 | ||||||||
PG Journal Number | 22/2012 | ||||||||
Publication Date | 01-Jun-2012 | ||||||||
Grant Date | 29-May-2012 | ||||||||
Date of Filing | 29-Nov-2004 | ||||||||
Name of Patentee | CONCAST AG | ||||||||
Applicant Address | TODISTRASSE 9 CH-8027 ZURICH | ||||||||
Inventors:
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PCT International Classification Number | B22D 11/059 | ||||||||
PCT International Application Number | PCT/EP2003/05238 | ||||||||
PCT International Filing date | 2003-05-19 | ||||||||
PCT Conventions:
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