EP2930723B1 - Device and method for processing a wire - Google Patents

Description

The invention relates to a method and a device for processing a wire, in particular an aluminum wire, wherein in a coating device for applying at least one layer of a coating on the wire at least one layer of a coating material is applied to the wire and the applied layer then in a baking oven for Drying or curing of the applied layer is dried or hardened, wherein the wire before the application of the layer and recrystallization of the wire through a separate from the baking oven annealing furnace, which is arranged in the wire conveying direction in front of the baking oven and is arranged for recrystallization of the wire promoted becomes.

In particular, the invention relates both to the preparation of a previously drawn wire on a coating and the application of the coating, wherein the wire is an uncoated bare wire, the metal structure is distorted due to the plastic deformation of the wire during the drawing, so that it has a corresponding reduced extensibility or Has tensile strength. In the coating, one or more coating materials may be applied to the wire in multiple layers and / or as a coating composition. Suitable coating materials are any lacquers or synthetic resins which are conventionally used in the coating or enameling of wires, in particular polyester imide (PEI) and / or polyamide imide (PAI). The baking oven (often referred to as a coating oven, kiln, or "curing oven") is designed to dry and cure the coating. In the process, solvents contained in the paint film are evaporated, discharged into the direct environment and transported away until the remaining polymer finally "crosslinks" or hardens on the wire surface. After application of the last layer of the coating, the wire is usually cooled and conveyed to a winder device for removal of the finished wire.

In-line annealing of copper wires in thermally heated tube annealing (or profiles), which uses inert gases such as water vapor (or nitrogen), is currently taking place in enamel wire systems. are flowed through. Such tube annealing are for example in the EP 0 448 999 A2 and the DE 31 18 839 A1 shown. The heat input into the wire takes place in such tube annealing convective on the proper movement of the wire through the inert gas atmosphere, heat radiation between Glührohrinnenwand and wire, and finally via heat conduction between Glührohrinnenwand and standing in direct contact with this wire (grinding wire). The heat input through heat conduction is dominant. The contact between the wire and the tube wall is even required in this case to provide the necessary heat transfer rates at the high throughput speeds. The abrasion and the damage of the copper wire surface by the contact with the tube wall are very small. The steam takes over the function as a protective gas against oxidation of the copper and at the same time the cleaning of drawing agent residues of the previously drawn bare wire. Attempts to anneal aluminum wires with such glow tube systems have repeatedly failed. Aluminum has a much lower melting point (660 ° C) than copper (1083 ° C) and is much softer due to the material. Direct contact of the rapidly moving aluminum wire with the glow tube inner wall leads at temperatures corresponding to massive abrasion and damage to the wire surface, and ultimately to the timely blockage of the glow tubes. Due to the large length of conventional glow tubes (~15m) and their relatively small diameters (25 mm), contact between wire and tube wall is almost inevitable. Although aluminum has a lower recrystallization temperature than copper, it also has a lower thermal conductivity. At the high throughput speeds of the aluminum wires corresponding to high heating tube temperatures would be required for their heating process, which would make trouble-free production operation impossible. In the conventional process method for coating aluminum wires in enameled wire plants, therefore, attempts are made mostly essential processes such as recrystallization annealing of the wire metal, a thermal cleaning of the wire metal surface of firmly adhering organic drawing agent residues and baking of the To realize paint films in one and the same furnace. For example, this describes CN 102074308 A a device and a process for producing painted aluminum wires, wherein the annealing of the unpainted wires and the curing after the application of the paint is carried out in one and the same furnace. The problem here is that for physical and thermodynamic reasons, however, these processes require different wire temperatures to complete them. Since both the soft-to-glow wire traces (ie, the tracks or sections of the wire in the oven) and the wire tracks to be coated forcibly have the same residence time in the oven at the same furnace conditions, but now form almost the same temperature profiles along the individual wire tracks. The various processes can therefore not be reconciled in terms of process technology: in this form of process development, the initial coating of the aluminum wires is often carried out on incompletely recrystallized bare wires with greatly variable softness and consequently with not completely cleaned out liner coatings. In order to still achieve a minimum of recrystallization, the temperature in the oven must be higher than actually suitable for drying. In addition, for the removal of the evaporated solvent, the air in the oven must be constantly replaced and therefore cooling fresh air constantly be reheated. Apart from the associated energy expenditure, the softness differences between the individual wire traces, which can not be controlled, lead to different wire tensile stresses, which in turn can cause wire tears and production losses. Due to the insufficient thermal cleaning of the bare-wire traces also usually follows an insufficient adhesion of the paint on the wire surface. In order to ensure the adhesion of the paint, a so-called "primer coating" is therefore usually applied as an adhesive interface even before applying the actual coating paint. Regardless of the extra effort, the "primer" coatings have very low heat classes, which automatically limits the applicability of the finished wire in often thermally loaded coils and windings. Such an aluminum enameled wire is so limited use and thus limited demand. Conversely, if a higher temperature is set in the oven to better To achieve recrystallization and cleaning, the coated traces are forcibly burned, resulting in improperly baked wire and also lower coating quality.

The JP H05-325684 A shows a painting process for copper wires with an annealing furnace, wherein the still soft wire is painted after annealing and used for curing of the wire itself heat energy emitted.

The CN 103000313 A shows a vertical painting machine in which a wire is conveyed from a unwinding by a glow, a paint container and a separate baking oven.

The CN 103258600 A relates to a painting process for aluminum wires, wherein the wires are annealed in a three-layer process with different temperatures. Subsequently, a primer layer and a lacquer layer is applied directly to the wire and cured in a baking oven.

Finally, the shows JP S59-28530 A a manufacturing process for painted copper or aluminum wires, wherein the drawn wire is continuously passed through an inline annealing system and annealed at a constant coating speed. After the annealing furnace, the wire is coated with varnish, which is then cured in its own baking oven.

Accordingly, it is an object of the invention to provide a method of the initially mentioned kind, with which a high-quality wire with the highest softness, process reliability and in particular without product value-reducing primer can be produced as an adhesive interface. The method should also largely avoid detrimental to the process safety heating of solvent vapors and at the same time reduce the energy consumption associated with the process or the device.

To achieve this object, the invention provides that the wire in the annealing furnace is conveyed by a substantially self-contained flow of a hot gas, in particular a circulating air flow. Accordingly, in the device of the type mentioned, the stated object is achieved in that the annealing furnace is preferably designed for convective heating of the wire by means of a heated in a substantially closed circuit heated gas, in particular by means of hot air. The annealing furnace (or simply called annealer) is preferably designed for non-contact heating of the wire, so that even a wire made of a material with a relatively low softening temperature is not damaged in the annealing furnace. The fact that the annealing furnace is provided separately from the stoving means in this context means that the annealing furnace is spatially and thermally separated from the stoving furnace and has an independent heat supply, in particular an independent heating element or an independent heat generating unit. The arrangement of the annealing furnace in the wire conveying direction before the baking oven is of course independent of the geometric arrangement of the two ovens and merely means that in the course of producing a coated wire, a portion of the wire to be processed first passes the annealing furnace, ie is conveyed through the annealing furnace, before the same section passes the baking oven. The annealing furnace is adjusted in terms of the temperature generated in the annealing furnace or the temperature profile to which the wire is exposed, so that an optimal recrystallization of the metal structure of the wire is achieved. The recrystallization takes place, as is known, above a temperature dependent on the wire material, which can be suitably selected by the person skilled in the art, and the annealing furnace can be adjusted accordingly. The wire is preferably coated after the last exit from the annealing furnace and before the first entry into the stoving furnace. Through the separate annealing furnace, the process conditions and the heat transfer achieved in the two furnaces, ie baking oven and annealing furnace, can be set independently and optimized for the respective task. Another advantage of the separate ovens is that it allows a high wire entry temperature into the annealing furnace because no solvent vapors are to be feared, and the wire does not need to be cooled after drawing. Due to the closed flow or the circulating air, the annealing furnace has a particularly low process air discharge as well as a lower fresh air supply required compared with a furnace which is set up for drying a wire coating. The otherwise necessary heating of the fresh air supplied can therefore be omitted, at least for the most part, which reduces the energy consumption associated with the method or device. In addition, the annealing furnace allows a separate annealing process of the wire with higher transport rates than in the subsequent baking oven. The flow of the hot gas may be directed against the wire conveying direction. The higher transport rates in the annealing furnace are achieved by a higher temperature level and, in particular in the case of a flow directed counter to the direction of the wire feed, by better convective heat transfer by means of suitable flow guidance.

Furthermore, it is advantageous if the annealing furnace is controllable independently of the baking oven for setting different temperature profiles and corresponding wire temperatures. The energy consumption associated with the generation of the respective temperature profile can be optimized in this case to the respective task of the furnace.

It is particularly advantageous if the wire is heated in the baking oven to a relatively lower wire temperature than in the annealing furnace. Accordingly, during operation, the average temperature in the annealing furnace is advantageously higher than the average temperature in the stoving furnace. Due to the temperature difference between baking oven and annealing furnace different wire temperatures can be achieved in the two ovens even at the same wire speed, ie with the same amount of wire carried out. Due to the lower temperature in the baking oven, temperature losses during the coating of the wire can be reduced and thus the energy consumption can be further reduced overall. In addition, at the lower temperatures during firing improved insulation properties of the finished wire, In particular, a required ideal tangent delta value for achieving minimal dielectric losses can be achieved in comparison to wires whose coatings have been dried and cured at excessively high temperatures. Finally, the lower temperatures in the baking oven are also advantageous in terms of process reliability, since thus excessive heating of the solvent vapors produced during drying is avoided. Due to the higher wire temperature in the annealing furnace, which may be above a suitable or permissible for the drying of a coating temperature, a much better recrystallization and thus better softness and extensibility (higher elongation at break) of the wire can be achieved. The wire temperature can, for example, in the annealing furnace above 360 ° C, in particular between 380 and 480 ° C, and / or in the baking oven below 360 ° C, in particular between 280 and 320 ° C.

If the wire is conveyed through the annealing furnace at least twice, preferably between four and fifteen times, in particular approximately ten times, a significantly improved cleaning of the wire can be achieved in addition to the recrystallization. Due to the multiple implementation by the correspondingly hot annealing furnace, for example, drawing agent residues are burned in layers of the wire. In this way, a suitable cleaning of the wire can be achieved even at wire temperatures below 450 ° C, so that a higher energy efficiency compared to a cleaning in one step at temperatures above 450 ° C is achieved. Due to the higher temperature in the annealing furnace in comparison to known methods, better cleaning and thus better adhesion of the lacquer to the wire surface as well as a better self-passivation by oxidation in the case of an aluminum wire can be achieved because of the reaction with a virtually surface free surface.

Advantageously, the coating material can be applied directly to the wire, ie the coating material intended for insulating the wire is applied directly to the metallic surface of the wire. The usage a primer or comparable adhesive bonding layers can be dispensed with, so that the finished wire advantageously has a comparatively higher temperature resistance of the coating and higher thermal class.

It has also been found to be beneficial if the wire between the two ovens, i. between the annealing furnace and the baking oven, is conveyed via a Nachspannvorrichtung, in particular via a pneumatic dancer, for tensioning the wire. In the present device may accordingly be arranged in the wire conveying direction after the baking oven and before the annealing furnace, a tensioning device for tensioning the wire. The post-tensioning device can compensate for voltage differences due to wire temperature differences and improves the smooth and trouble-free conveyance of the wire from the annealing furnace and into the stoving furnace.

• Fig. 1 ein schematisches Diagramm des Zusammenhangs zwischen einer Drahttemperatur und der damit erzielten Dehnbarkeit des Drahtes;
• Fig. 2 eine schaubildliche Darstellung einer Drahtbeschichtungsanlage mit einem Einbrennofen und einem Glühofen;
• Fig. 3 einen pneumatischen Tänzer gemäß Fig. 2;
• Fig. 4 eine schematische Schnittdarstellung durch den Glühofen gemäß Fig. 2;
• Fig. 5 eine schematische Schnittdarstellung eines Drahtes im Längsschnitt während der Erhitzung im Glühofen; und
• Fig. 6 schematisch mehrere Querschnitte des Drahtes nach einer unterschiedlichen Anzahl von Durchführungen durch den Glühofen.

The invention will be explained below with reference to particularly preferred embodiments, to which it should not be limited, and with reference to the drawings. The drawings show in detail:

• Fig. 1 a schematic diagram of the relationship between a wire temperature and the resulting extensibility of the wire;
• Fig. 2 a perspective view of a wire coating plant with a baking oven and an annealing furnace;
• Fig. 3 a pneumatic dancer according to Fig. 2 ;
• Fig. 4 a schematic sectional view through the annealing furnace according to Fig. 2 ;
• Fig. 5 a schematic sectional view of a wire in longitudinal section during the heating in the annealing furnace; and
• Fig. 6 schematically several cross sections of the wire after a different number of passes through the annealing furnace.

Wire drawing distorts the metal texture of the wire due to plastic deformation. It increases its strength and hardness, while the extensibility deteriorates massively. In order to fulfill the mechanical-technological requirements relevant to the post-processing of the wire, the wire must again become "soft", which requires a reshaping of the microstructure. For this purpose, the wire must be heated accordingly. In the in Fig. 1 The graph shown is plotted on the abscissa, the wire temperature T and on the ordinate the achieved "softness" or extensibility R of the wire. The drawn curve R (T) schematically represents the relationship between the wire temperature T and the extensibility R. The indicated temperatures T1, T2, T3 show approximately the optimum temperature T1 for the curing of a wire coating, the optimum temperature T2 for recrystallization of the wire (corresponding to the formation of a homogeneous microstructure and thus the maximum achievable extensibility R) and the optimum temperature T3 for cleaning off drawing agent residues from the freshly drawn wire. For example, in the case of an aluminum wire coating, the temperature T1 would be approximately between 280 ° and 320 ° C, the temperature T2 between 380 and 400 ° C and the temperature T3 between 450 and 480 ° C.

In Fig. 2 a production line for producing a coated wire is shown, wherein the wire is pulled in drawing machines 1, then conveyed through the annealing furnace 2 several times. In copper wires, the thin wire usually passes to the drawing machine 1 via pulleys in an electrically heated tube annealing, which allows the heating of the copper wire via thermal radiation, but above all by direct wall contact via heat conduction. An annealing process with direct wall contact, however, can not be used, for example, with aluminum wires, since compared to copper much lower softening temperatures are present and the wire would therefore be massively damaged. Such wires, ie wires with relatively low softening temperatures, can be heated for annealing, for example with hot moving air; This method is non-contact and the occurring, for example, in the case of Aludrähten oxidation in contrast to copper wires is not a problem because it is self-passivating. At the in Fig. 2 shown production line, the wire is heated accordingly in the annealing furnace 2 with hot moving air (see. Fig. 4 ).

After leaving the annealing furnace 2, the heat-treated wire is fed via deflection rollers of the coating device 3, for example in the form of a lacquerware, at the Einbrennofeneintritt where the liquid paint is applied to the wire at ambient temperature. The dissolved polymers in the paints subsequently crosslink chemically after application and characterize the actual curing process of the paint. The paint is applied via conically shaped wiping nozzles, which are continuously fed by means of a pump pump with fresh paint. There, a paint film with a preset thickness is evenly applied to the wire surface. Due to limited adhesion of the liquid paint on the wire, the application of the paint required for the desired insulating layer thickness must be done in several steps. For this purpose, the enameled wire is guided in up to 24 tracks via two grooved deflecting rollers between the lacquerware at the oven inlet and the radiator end through the stoving oven 4. For drying the polymeric liquid film hot process air is circulated in the currently used practically worldwide painting process within the furnace, while the wire passes through the machine in a straight line against the air flow. During this convective drying, the solvents contained in the coating film are evaporated, discharged into the direct environment and transported away until the remaining polymer finally "crosslinks" or hardens on the wire surface due to the high temperatures (450-700 ° C.). In the baking oven 4 while a temperature profile is generated, with which a drying and subsequent curing of the applied layer is achieved. Between the individual coating passes, the wire is cooled in cooling devices 5. Between the annealing furnace 2 and the baking oven 3, the wire via pneumatic dancer 6 (see. Fig. 3 ), which tension the wire and compensate for temperature-induced voltage fluctuations. The completely coated finished wire is finally fed to the Wicklervorrichtungen 7, which wind the wire on rollers 8.

Fig. 4 schematically shows a longitudinal section parallel to the wire conveying direction 9 through the annealing furnace 2. On an inlet side 10 of the uncooled bare wire is introduced into the annealing furnace 2.

A high wire inlet temperature enables a small temperature loss or a small necessary heat input and an optimal recrystallization of the wire 14. The flow of the hot circulating air in the annealing furnace 2 along a closed circuit is indicated by the arrows 11, 12. In this case, the hot air in the wire transport region 13 flows counter to the wire conveying direction 9 (cf. Fig. 5 ) to allow optimum heat convection and thus maximum heat transfer from the hot air to the wire. Due to the high temperature of the hot air, residues 15 on the bare wire, eg drawing agent residues, can be removed or burned off in layers. Since the wire 14 in the annealing furnace 2 is still uncoated, there are no emissions such as when painting a paint, so that the hot air from the inlet side 10 can be circulated and reused parallel to the wire transporting area 13 according to the arrow 11. An air exchange can largely be omitted. The removed residues can be separated from the circulated hot air.

The successive removal of the residues 15 from the wire 14 is in Fig. 6 shown schematically, wherein the three wire cross sections 16 each show a different progress of the ablation. The uppermost wire cross section 17 shows the wire 14 before the first pass through the annealing furnace 2, wherein all remaining after pulling on the wire 14 residues 15 are still present; the mean wire cross section 18 shows the wire after five passes, whereby already the majority of the residues 15 could be removed; and the lowermost wire section 19 shows the completely cleaned wire 14 after the tenth pass through the annealing furnace 2.

In the annealing furnace, for example, there is an air temperature of circulating air of 650 ° C. The following table shows the tensile strength of the wire based on the elongation (in percent) until break after each pass through the annealing furnace 2: Pass 1 34.1% Pass 2 37.7% Pass 3 37.8% Pass 4 36.7% Pass 5 38.2% Pass 6 37.2% Pass 7 38.3% Pass 8 37.8% Pass 9 36.4% Pass 10 37.6%

The following table shows by way of example a sequence of passes through the baking oven 4 for baking the paint films with the respective previously applied coating material and the tensile strength of the wire after the pass: Pass 1 polyesterimide 37.9% Pass 2 polyesterimide 37.7% Pass 3 polyesterimide 38.1% Pass 4 polyesterimide 38.5% Pass 5 polyesterimide 37.8% Pass 6 polyesterimide 37.3% Pass 7 polyesterimide 38.4% Pass 8 polyesterimide 37.9% Pass 9 polyesterimide 38.2% Pass 10 polyesterimide 38.8% Pass 11 polyesterimide 37.8% Pass 12 polyesterimide 37.1% Pass 13 polyesterimide 38.5% Pass 14 polyesterimide 38.0% Pass 15 polyamide-imide 38.9% Pass 16 polyamide-imide 38.1% Pass 17 polyamide-imide 38.7% Pass 18 polyamide-imide 40.3%

Claims (10)

1. Method for processing a wire (14), in particular an aluminium wire, at least one coat of a coating material being applied to the wire (14) and the applied coat subsequently being dried and/or cured in a stoving oven (4), the wire (14) being conveyed through an annealing oven (2) that is separate from the stoving oven (4) before the coat is applied and in order to recrystallise the wire (14), characterised in that the wire (14) is conveyed in the annealing oven (2) by means of a substantially self-contained flow of a hot gas, in particular a flow of recirculated air.
2. Method according to claim 1, characterised in that the flow of the hot gas is oriented counter to the wire-conveying direction (9).
3. Method according to either claim 1 or claim 2, characterised in that the wire (14) is heated to a comparatively lower wire temperature (T) in the stoving oven (4) than in the annealing oven (2).
4. Method according to any of the preceding claims, characterised in that the wire (14) is conveyed through the annealing oven (2) at least twice, preferably between two and 15 times, in particular approximately ten times.
5. Method according to any of the preceding claims, characterised in that the coating material is applied directly to the wire (14).
6. Method according to any of the preceding claims, characterised in that the wire (14) is conveyed between the two ovens (2, 4) by means of a re-tensioning device (6) for re-tensioning the wire (14).
7. Device for processing a drawn wire (14), in particular an aluminium wire, comprising a coating device (3) for applying at least one coat of a coating to the wire (14), and comprising a stoving oven (4) for drying and/or curing the applied coat, an annealing oven (2) that is separate from the stoving oven (4) being provided, being arranged upstream of the stoving oven (4) in the wire-conveying direction (9) and being designed for recrystallising the wire (14), characterised in that the annealing oven (2) is designed for convectively heating the wire (14) by means of a heated gas that is moved in a substantially closed loop, in particular by means of hot air.
8. Device according to claim 7, characterised in that the annealing oven (2) can be controlled independently of the stoving oven (4) in order to set different temperature profiles and corresponding wire temperatures (T).
9. Device according to either claim 7 or claim 8, characterised in that, during operation, the average temperature in the annealing oven (2) is higher than the average temperature in the stoving oven (4).
10. Device according to any of claims 7 to 9, characterised in that a re-tensioning device (6) for re-tensioning the wire (14) is arranged upstream of the stoving oven (4) and downstream of the annealing oven (2) in the wire-conveying direction (9).

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