EP4058611A1

EP4058611A1 - Regulated heat treatment of foil

Info

Publication number: EP4058611A1
Application number: EP20803186.4A
Authority: EP
Inventors: Stephan Draese; Olaf ERDMANN; Bernd Kemper; Volker Schmitz; Oliver Seiferth; Andreas Kramer
Original assignee: Speira GmbH
Current assignee: Speira GmbH
Priority date: 2019-11-12
Filing date: 2020-11-12
Publication date: 2022-09-21
Also published as: JP2022550211A; WO2021094432A1; KR20220070517A; BR112022007669A2; CN114729413A; KR20240026248A; JP7378615B2

Abstract

The invention relates to a method for the heat treatment of metal strip or foils in the form of strip coils or foil coils in a heat treatment furnace for removing rolling residue. The problem of providing a method for the heat treatment of metal strip or foils in the form of strip coils or foil coils in a heat treatment furnace for removing rolling residue, with which high-quality metal products can be provided in a process-stable and low-cost manner and the ratio of rejects of metal strip and foils can be reduced, is solved by determining, during the performance of the heat treatment, the content of at least one evaporation and/or oxidation product in the furnace atmosphere and/or in the process exhaust gas, and using said determination for process control or regulation of the heat treatment, wherein the dynamics of the removal of rolling residue on the metal strip or foils are controlled or regulated during the heat treatment. The invention further relates to a device for the heat treatment of metal strip or foils for carrying out the method according to the invention.

Description

Regulated film heat treatment

The invention relates to a method for the heat treatment of metal strips or foils in a heat treatment furnace, in particular for the removal of rolling residues. The invention further relates to a device for the heat treatment of metal strips or foils for carrying out the method according to the invention.

Heat treatment plays a special role in the production of metal strips or foils. During the manufacturing process, the metal products usually go through hot and cold rolling processes and, if necessary, intermediate annealing so that temperature-dependent processes in the structure of the material can be used to influence the properties of the metal products in a targeted manner.

The various process steps are usually followed by final annealing, which is one of the most critical processes, especially in film production. The final annealing serves on the one hand for recrystallization or partial recrystallization, the so-called state annealing or back annealing of the metal strips and foils, with the recrystallization taking place when the recrystallization temperature of the material is exceeded. On the other hand, the finish annealing is used for thermal cleaning of the strip surfaces, in particular for so-called degreasing of rolling residues such as lubricants used in the rolling mills, for example greases, waxes and rolling oils. In order to ensure a lubricant-free surface for further processing of the metal products and, for example, to prevent adhesion problems during subsequent forming, the strip surfaces must be thoroughly cleaned. This is done by the staggered glow phases of the Evaporation of lubricants and oily residues on the tape or film surface.

The annealing programs used, in which a. the temperature-time curve, the volume of process air exchange between the environment and the furnace chamber and the air volume for circulation in the furnace chamber are therefore always a compromise between recrystallization and degreasing requirements for the annealing process. The process becomes even more complex with state annealing, since partial recrystallizations react more sensitively to the annealing parameters. However, since general annealing programs are generally used in the context of today's annealing processes and there are no differentiation criteria, it is not possible to react individually to the parameters of the starting material in particular. The process technology is also mostly poorly instrumented and actually effective parameters on the metal strip or the metal foil such as the metal temperature or the air volume are unknown and are only estimated on the basis of auxiliary variables such as a fan speed or a shutter position.

Over the years, two glowing philosophies have become established in the industry. On the one hand the quality-driven low-temperature long-term annealing and on the other hand the resource-driven high-temperature short-term annealing. The low-temperature long-term annealing is characterized by its tolerance to deviations in input and environmental parameters such as surface roughness, the oil content in quality and quantity, the density and humidity of the process air or the winding density in the case of metal strips or foils wound into coils This represents a quality-optimized, good-natured philosophy. A problem with low-temperature long-term annealing, however, is the contamination of rolling oil with tramp oils that do not burn off at lower annealing temperatures. In addition, the relatively long annealing times temporarily lead to a lack of free annealing capacity and, moreover, represent a not insignificant cost factor. While the requirements for product quality are increasing and narrowing Tolerance limits for the surface properties have to be adhered to, a more efficient use of energy gains in importance against the background of cost-saving and resource-saving manufacturing processes.

Although high-temperature short-term annealing is an efficient, throughput-optimized philosophy, it has a high incidence of annealing errors because it is not very tolerant of the aforementioned input and environmental conditions. The combination of fault-intolerant high-temperature short-term annealing, natural process fluctuations from the preliminary processes and poorly instrumented furnace technology inevitably leads to frequent inhomogeneities in the degreasing process and thus to annealing defects, which lead to poor unwinding quality, in particular to adhesions near the roll core, and to adhesion problems of the products in the subsequent processing. Thin metal strips or metal foils in particular react sensitively to the annealing treatments and develop tension, flow lines or even incandescent bubbles. Uncontrollable wrinkles and uneven strength properties have a negative effect on the subsequent processing steps through to the end product. In the worst case, the stresses, flow lines and incandescent bubbles can lead to cracks, rendering the metal products completely unusable.

From the German patent application DE 197466733 A1 a method for determining the gas atmosphere in a heat treatment furnace is known, with which the supply of inert gas can be optimized during the heat treatment. A precise method for controlling a furnace atmosphere is also known from European patent application EP 2 871 248 A1. However, both documents do not deal with the avoidance of annealing errors in the annealing of strip or foil coils.

The present invention is therefore based on the object of providing a method for the heat treatment of metal strips or foils in a heat treatment furnace, in particular for the removal of rolling residues which reliably and inexpensively high-quality metal products can be provided and the scrap portion of metal strips and foils can be reduced. In addition, the present invention is based on the object of proposing advantageous devices for the heat treatment of metal strips or foils, in particular for carrying out a method according to the invention.

According to a first teaching of the present invention, the above-indicated object for a method for the heat treatment of metal strips or foils in the form of strip or foil coils in a heat treatment furnace to remove rolling residues is achieved in that while the heat treatment is being carried out, the content of at least one Evaporation and / or oxidation product is determined in the furnace atmosphere and / or in the process exhaust gas and is used for process control or regulation of the heat treatment, the dynamics of the removal of rolling residues on the metal strips or foils being controlled or regulated during the heat treatment.

The heat treatment is, for example, a final annealing of the metal strips or foils. Corresponding annealing can facilitate further processing such as subsequent forming steps, improve the mechanical properties of the metal products and promote dimensional stability. Finished annealing is carried out in particular for soft annealing and cleaning purposes. By cleaning, in particular degreasing, the surface of the rolled metal product can be freed from residues of the cooling lubricants and prepared, for example, for strip coating. Problems during further processing such as poor winding quality or adhesion problems during subsequent forming can be prevented by cleaning the product surfaces. For this purpose, the metal strips or foils are annealed in the form of a strip or foil coil in the heat treatment furnace. In principle, the heat treatment can also involve intermediate annealing, the aim of which, for example, is to facilitate subsequent rolling steps. Even with intermediate anneals, annealing defects can already occur, especially if the metal strips or foils are in the form of a coil and their thickness is very small.

The elimination of rolling residues is determined by the evaporation and oxidation of the cooling lubricants that remained as residues on the surfaces of the metal products after rolling, whereby the metal temperature, the type and amount of rolling oil coating and the atmosphere in the furnace chamber, the so-called furnace atmosphere or process air , are decisive for the vapor pressure of the rolling oil to be evaporated and the oxidation of the same. The temperature of the metal product results among other things. from the given temperature-time curve of the annealing program, the weight and dimensions of the product, the material thickness, the degree of furnace filling, the construction type and the degree of efficiency of the furnace. The type and amount of the rolling oil coating result from the selection and the (variable) composition of the rolling oils used for rough rolling, double and finishing rolling, which in turn consist of base oils and additives. In particular, the composition of the furnace atmosphere has a major impact on the cleaning result. Both the composition of the furnace atmosphere and that of the process exhaust gas that is discharged from the furnace chamber are in turn dependent on a number of factors. They are i.a. a product of the stage of annealing, the process step to be carried out, the furnace filling level and the starting material to be treated.

It has been shown that with the method according to the invention, the conditions of the starting material, for example the boiling behavior and the amount of oil coating, as well as the status of the annealing process, for example the evaporation and oxidation phase, implicitly by measuring the content of at least one evaporation and / or Oxidation product are detected in the furnace atmosphere and / or the process exhaust gas. Salary information generally quantifies the proportion of an individual Substance in a mixture. In the present case, this also includes, for example, concentrations which indicate the amount of a product in relation to a given volume of air. A pure determination of the amount without knowledge of the volume is also conceivable.

By determining the content of at least one evaporation and / or oxidation product, a statement can be made about the dynamics of the evaporation and the oxidation of the cooling lubricants. Depending on this, the method according to the invention can in turn influence the control or regulation of the heat treatment, in particular the removal of the rolling residues can be controlled or regulated, whereby the dynamics of the evaporation and oxidation of the rolling residues, for example in strip or foil coils, can be advantageously controlled . A direct measurement in the furnace atmosphere can preferably provide real-time results and thus a high level of information about the contents of evaporation and / or oxidation products currently in the atmosphere. While a measurement in the process exhaust gas is particularly easy, it entails a time delay due to the inertia of the process.

According to the invention, it was recognized that by determining the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust, the heat treatment, in particular the removal of rolling residues, can in turn be advantageously controlled or regulated. Process control means here that the actual value of a parameter, if it deviates from the desired setpoint, is changed by suitable process action so that the actual value approaches the setpoint and ideally reaches it. Because the drifting away from the setpoint is counteracted, the feedback is a negative feedback. The process control can be carried out, for example, by a PID controller. In the process control, on the other hand, there is no feedback and consequently no closed action sequence. Control is understood to mean influencing the behavior of a system, the system being controlled by the Control is brought into another state. The control or regulation can take place by influencing selected parameters, for example by reducing or increasing a value.

The control or regulation according to the method according to the invention is characterized in that it depends on the content of at least one evaporation and / or oxidation product that is present in the furnace atmosphere and / or in the process exhaust gas, and thus depending on the conditions of the starting material as well as the status of the annealing process. This has the advantage that it is possible to react appropriately to variations in the process parameters mentioned, and thus the surface of a rolled metal product is reliably freed of cooling lubricant residues. The method according to the invention thus makes it possible to use high-temperature short-term annealing while at the same time avoiding the typical annealing defects. It thus represents a practicable, cost-effective solution for the removal of rolling residues and increases the fault tolerance of the high-temperature short-term annealing, which is highly dependent on the input conditions and process parameters.

The metal strips or foils are preferably annealed in the form of strip or foil coils in a batch furnace. Batch ovens are usually not as costly to operate and purchase as continuous ovens. One difficulty with batch furnaces, however, is usually ensuring that the temperature is evenly distributed, for example when loading metal coils into the furnace. Inhomogeneities in the cleaning process usually occur primarily with strip or foil coils, since the rolling oil is oxidized and the exhaust gases are expelled via the end faces of the wound rolls. In the case of heat treatment, the heating initially takes place from the outside, the metal inside the foil coil, on the other hand, does not heat up as quickly. This leads to a delayed increase in the evaporation and / or oxidation products, but ultimately a sudden increase in the event of additional heating of the metal inside the foil coil. The inhomogeneities can lead to Cause annealing defects and poor unwinding quality as well as adhesion problems during further processing. Thin metal strips and foils in particular are sensitive to annealing treatments and form stresses or even incandescent bubbles, especially inside the foil coils, which in the worst case can lead to cracks in the products.

With the method according to the invention, a statement can be made about the speed and the uniformity of the evaporation process in the case of strip and foil coils. In addition, it is possible to react advantageously to the scatter of the input parameters and process parameters of the cleaning process and thus in particular to influence the gas pressure in the strip or foil coils, which is harmonized, for example controlled or regulated, by the method. Harmonizing the gas pressure can be understood to mean, for example, an equalization of the increase in the gas pressure, that is to say a reduction in the dynamics of the evaporation during the heat treatment. The method according to the invention can therefore advantageously control or regulate the dynamics of the evaporation and oxidation of the rolling residues in strip and foil coils. The furnace atmosphere, which is precisely coordinated with the aid of the method according to the invention, thus also ensures the desired results for the heat treatment of strip or foil coils and enables an increase in the fault tolerance of high-temperature short-term annealing. Tape and foil coils produced with the method according to the invention can be unwound, in particular, at increased speed without sticking.

Metal foils with a thickness of 1 μm to 250 μm, preferably 1 μm to 60 μm, particularly preferably 4 μm to 20 μm, are treated with the method according to the invention. The production of metal foils is carried out starting from what is known as foil pre-rolled strip, usually with the process steps of pre-rolling, doubling, finishing rolling, separating, winding and finish annealing. Here, the pre-rolling and finish-rolling serve to decrease the height, the doubling the joining of two strip layers for the doubled finish-rolling, the separating the separation of the finished rolled foil webs, the winding up, the provision of foil coils and the final annealing, the degreasing of the foil surfaces and the recrystallization of the material.

Preferably, with the method according to the invention, the gas pressure of the evaporation and / or oxidation products in the strip or foil coil is controlled or regulated during the heat treatment, so that targeted damage to the metal strips or foils through too rapid evaporation or too rapid generation of oxidation products in the strip. or foil coil can be significantly reduced.

According to a first embodiment of the method according to the invention, in the process control or regulation, the furnace temperature, the furnace temperature gradient, the process air exchange volume, the circulating volume of process air and / or the composition of the furnace atmosphere is dependent on the content of the at least one evaporation and / or oxidation product in the furnace atmosphere and / or controlled or regulated in the process exhaust gas. It was recognized that in particular the parameters temperature, temperature gradient, exchange volume and circulation volume as well as the composition of the furnace atmosphere have an influence on a particularly effective and homogeneous heat treatment of strip or foil coils. Uniform evaporation of the residues is necessary to ensure that rolling residues are uniformly removed from the product surfaces, for which a homogeneous temperature distribution is crucial. In order to avoid a sudden increase in evaporation and oxidation products in the furnace atmosphere and / or in the process exhaust gas, the temperature gradient can be adjusted accordingly with the aid of the method according to the invention. The circulating volume of process air can also be used to indirectly influence the uniformity of the temperature distribution in the heat treatment furnace. In addition, a constant distribution of the individual gas components in the furnace chamber can be achieved by controlling or regulating the circulation volume. Through a control or Regulation of the process air exchange volume, for example in the context of convection ventilation, can also influence the furnace atmosphere.

The dynamics of the evaporation and oxidation of the rolling residues, in particular the rolling oils, are thus controlled according to the invention, for example, by a hindering or promoting setting of the furnace temperature, the setting of the gradient of the furnace temperature and the setting of the furnace atmosphere.

The vapor pressure of the rolling oil to be evaporated and the speed of the evaporation process are influenced by measuring and setting the furnace chamber temperature and the gradient of the furnace chamber temperature. For example, setpoint values can be assigned to the parameters to be measured. In cases in which the concentration of rolling oil and partially oxidized rolling oil or the concentration of rolling oil oxidation products in the furnace atmosphere exceeds or falls below a predefined threshold value, the furnace temperature is changed, for example held or lowered, or the gradient of the temperature rise is changed, for example reduced .

The vapor pressure of the rolling oil to be evaporated and the speed of the evaporation process are also influenced by measuring and setting the content of already evaporated and / or oxidized rolling oil in the furnace atmosphere. If the content of rolling oil and partially oxidized rolling oil or the content of rolling oil oxidation products in the furnace atmosphere falls below, for example, a predefined threshold value, the process air exchange is changed, for example increased or reduced.

The oxidizability of the rolling oil to be evaporated and / or evaporated and the speed of the oxidation processes are also influenced by measuring the content of already evaporated and / or oxidized rolling oil in the furnace atmosphere and by setting the oxidizing ability of the furnace atmosphere. For example, in those cases in which the content of rolling oil and partially oxidized rolling oil or the content of rolling oil oxidation products in the furnace atmosphere exceeds a predefined threshold value, the oxidation ability of the furnace atmosphere can be increased by adding process gases that weaken or reduce the oxidation, such as nitrogen or hydrogen, In those cases in which the content of rolling oil and partially oxidized rolling oil or the content of rolling oil oxidation products in the furnace atmosphere falls below a predefined limit value, the oxidation capability of the furnace atmosphere is influenced, preferably reduced, by adding process gases that increase oxidation, such as oxygen or ozone influenced, preferably increased.

The advantageous embodiment of the method according to the invention thus makes it possible in particular to influence the gas pressure in metal strip or metal foil coils in many ways, to harmonize it over time and thus to increase the fault tolerance of high-temperature short-term annealing. The cleaning process of the surface of the metal strip or the metal foil in the wound coil can be optimized through the continuous control of and the regulated influence on the temperature level and gradient and / or the composition of the furnace atmosphere.

According to a further advantageous embodiment of the method according to the invention, the furnace temperature gradient is controlled or regulated in the process control or regulation depending on the gradient of the content of the at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas. Depending on an increase or decrease in the content of the evaporation and / or oxidation products, the steam pressure of the rolling oil to be evaporated and the speed of the evaporation process can also be influenced in a targeted manner. If the gradient of the content of rolling oil and partially oxidized rolling oil and / or the content of rolling oil oxidation products in the furnace atmosphere exceeds, for example, a predefined one Threshold value, the gradient of the temperature rise is adapted, for example reduced.

To control or regulate the heat treatment, according to a next advantageous embodiment of the method according to the invention, the carbon content (Cges content), the content of organic compounds (Vorg content), the carbon monoxide content (CO content) and / or the carbon dioxide content (CO2- Content) in the furnace atmosphere and / or in the process exhaust gas and used for process control or regulation of the heat treatment. The carbon content of the furnace atmosphere and the process exhaust gas can be reliably determined in a particularly simple manner and is characteristic of evaporation and oxidation products. The CO and / or CO2 content represents the content of rolling oil oxidation products, while the Vorg content reflects the content of rolling oil and partially oxidized rolling oil. The totality of all carbon-containing substances, ie including Vorg, CO and CO2, is characterized by C _tot.

The Cges content, the Vorg content, the CO content and the C02 content in the furnace atmosphere or in the process gas are particularly critical parameters.

Thus, it was found that it in conventionally carried out annealing steps of metallic tape or Metallfoliencoils in the furnace atmosphere or in the process exhaust gas to a very sudden increase in the C _ges -content, the Vorg content, the CO content and / or C02 content comes, the _tot in a pronounced C - peak, Vorg peak CO Peakbzw. C02 peak results. However, such conventional processes lead to the above-described problems in tape or film production and accordingly provide inadequate product results. With the aid of the method according to the invention, however, the heat treatment can advantageously be influenced in a targeted manner and such carbon peaks can be reduced or avoided, for example, by controlling or regulating the temperature, the circulation volume or the process air exchange, which leads to good annealing results. The maximum carbon content Cges max, the maximum content of organic compounds Vorgmax, the maximum carbon monoxide content COmax and / or the maximum carbon dioxide content CO2 max is preferably limited in the furnace atmosphere and / or in the process exhaust gas, for example with a defined exchange volume of the furnace atmosphere or process exhaust gas volume. By limiting the maximum carbon content C _ge s max, the maximum content of organic compounds Vorgmax, the maximum carbon monoxide content COmax, and / or the maximum carbon dioxide content C02 max with a defined exchange volume of the furnace atmosphere or process exhaust gas volume, the method according to the invention allows, for example, to control the maximum evaporation rate , whereby advantageously good annealing results can be achieved, in particular incandescent bubbles can be reduced or avoided entirely.

According to a further embodiment, the carbon _{gradient C ge} s Grad, the gradient of the content of organic compounds Vorg Grad, the carbon monoxide gradient COcrad and / or the carbon dioxide gradient CO2 Grad in the furnace atmosphere and / or in the process exhaust gas is limited. It has been shown that too high a gradient in the C _ge s, Vorg, CO or C02 content in the furnace atmosphere or in the process exhaust gas indicates a sudden and strong increase in evaporation and / or oxidation products which in turn would lead to sticking and the formation of incandescent bubbles in the metal products. The control of the gradient thus enables control of the evaporation rate and thus, regardless of the total content of C _ge s, Vorg, CO and / or CO2 in the furnace atmosphere and / or in the process exhaust gas, avoidance of incandescent defects such as incandescent bubbles.

The pre-content is preferably measured by an FID analyzer, preferably an on-line FID analyzer, the CO content by a CO analyzer, preferably an on-line CO analyzer, the CO 2 content by a CO 2 analyzer, preferably an on-line CO 2 analyzer, and / or the C _total content by an FID analyzer and a CO analyzer and optionally a CO 2 analyzer.

F1D (flame ionization detector) analyzers are particularly suitable for monitoring for volatile carbonaceous substances. Since the detector signal of an FID analyzer is linearly proportional to the carbon content over a wide concentration range, this can be estimated without calibration, so that F1D analyzers can be used particularly well for quantification. In addition, an FID analyzer is not only fast and robust, it is also very sensitive. The determination of the carbon content can thus be carried out reliably and reliably.

To measure the CO or C02 content, for example, CO or C02 sensors or infrared analyzers can be used, which are characterized by particularly high precision. In particular, the CO 2 infrared analysis represents a particularly precise in situ measurement method. At the same time, however, infrared analyzes are relatively expensive and complex, since the analyzers require regular calibrations.

The Cges content can be measured using an FID analyzer, preferably an on-line FID analyzer, a CO analyzer, preferably an on-line CO analyzer, and a CO 2 analyzer, preferably an on-line CO 2 analyzer, be determined. Sufficient accuracy for determining the C _total content can, however, be achieved by using an FID analyzer and a CO analyzer.

According to a further advantageous embodiment of the method according to the invention, the heat treatment is carried out at a temperature of 80 to 120.degree. C. or more than 200.degree. C., preferably more than 220.degree. C., particularly preferably more than 300.degree. With annealing temperatures above 200 ° C, an essentially complete elimination of rolling residues on the product surfaces can be achieved. The duration of the heat treatment depends, among other things, on the temperature and the mass of the material to be treated. In the case of low-temperature annealing at 80 to 120 ° C., the method according to the invention can remove Roll residues, for example in the case of hard-rolled foils, can be achieved without significant softening.

Metal strips or foils are preferably treated in the form of coils. Depending on the coil width, annealing times can be approx. 20 to 180 hours in order to achieve essentially complete removal of the rolling residues. The coil width depends primarily on the use of the metal strips and foils. Narrow coils have a width of 250 mm to 1000 mm, for example. For an essentially complete cleaning of the product surfaces, the annealing times for narrow coils are about 80 hours at an annealing temperature of approx. 220 ° C, approx. 35 hours at a temperature of approx. 350 ° C and one at a temperature of approx. 400 ° C Glowing time of only about 20 hours. Wide coils, on the other hand, can have widths of 1000 mm to 2500 mm, preferably 1300 mm to 2100 mm. For example, the glow time at a temperature of approx. 220 ° C. is approx. 180 hours, at a temperature of approx. 350 ° C. approx. 80 hours and at a temperature of approx. 400 ° C. approx. 60 hours.

Aluminum or aluminum alloy strips or foils are preferably treated. The material aluminum is characterized by its diverse technical uses. By adding alloying elements, aluminum strips and foils with different properties can be produced. In combination with different thermal treatments, the mechanical properties of aluminum can be optimally adapted to the respective processing and usage conditions.

Among other things, aluminum is considered a key material for the packaging industry. In the food and pharmaceutical sectors in particular, aluminum is found in many packaged product forms, such as liquid packaging, e.g. B. milk or juice cartons, omnipresent. Due to their low density, the use of aluminum tapes and foils is particularly advantageous for weight-sensitive applications. No competing material can match it A combination of formability, printability and excellent barrier properties, such as low permeability for light, oxygen and flavorings, make aluminum foil unsurpassed when it comes to protecting and maintaining complex food supply chains. The use of appropriately treated aluminum strips and foils for food packaging, in particular for liquid packaging, is therefore particularly advantageous.

According to a second teaching of the present invention, the above-mentioned object is achieved by a device for the heat treatment of metal strips or foils in the form of a strip or foil coil for removing rolling residues according to the method according to the invention, in that the device has at least one means for determining the content at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas while the heat treatment is being carried out and at least one means for controlling or regulating the heat treatment depending on the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas, which are designed in such a way that the dynamics of the removal of rolling residues on the metal strips or foils during the heat treatment can be controlled or regulated with them. The at least one means for controlling or regulating the heat treatment is designed in particular for controlling or regulating the heat treatment depending on the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas. The device according to the invention is therefore suitable for carrying out the method according to the invention.

The device for heat treatment is preferably a batch furnace. Batch ovens are usually less expensive to operate and purchase than continuous ovens and enable the heat treatment of metal strips or foils wound into coils. For this purpose, a batch furnace has a furnace body and a furnace chamber, the furnace chamber inside the Furnace body is arranged and is designed for receiving at least one tape or foil coil.

The device according to the invention also has at least one means for determining the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas, such as a Vorg, CO and / or CO 2 analyzer, preferably an F1D or an infrared analyzer. The process air inside the furnace chamber is called the furnace atmosphere. An exchange of process air takes place between the furnace chamber and the environment, it also being possible according to the invention to provide means for determining evaporation and / or oxidation products in the process exhaust gas. A PID controller, for example, can be provided as a means for controlling or regulating the heat treatment.

With the aid of the device according to the invention for heat treatment, for example, a final annealing of metal strips or foils can be carried out for cleaning purposes. The device according to the invention enables the monitoring of levels of evaporation and / or oxidation products in the furnace atmosphere and / or in the process exhaust gas and a targeted influence on the process parameters of the heat treatment, for example a control or regulation of the dynamics of the removal of rolling residues on the metal strips or - foils in the coil during heat treatment. For example, the gas pressure of the evaporation and / or oxidation products in the strip or foil coil can be controlled or regulated in this way during the heat treatment, so that a process-safe, efficient and reliable cleaning of the surfaces of the metal strips or foils from rolling residues is guaranteed. Incandescent bubbles, problems in subsequent processing steps or sticking when unwinding tape or foil coils, which can lead to product damage or even cracks in the product surface, can thus be avoided. According to a first advantageous embodiment of the device according to the invention, the device has at least one means for controlling or regulating the furnace temperature, the furnace temperature gradient, the process air exchange volume and / or the circulating volume of process air depending on the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust.

The device preferably has at least one means for controlling or regulating the furnace temperature gradient depending on the gradient of the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process waste gas. In this way, for example, a direct harmonization, that is to say for example an equalization, in particular a reduction in the dynamics of the evaporation of a rolling residue in the strip or foil coil can be achieved.

In order to be able to influence the heat treatment depending on the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas, the device preferably has at least one controllable means for influencing the heat treatment. With the aid of a heater or flap, it is possible, for example, to influence the temperature or the temperature gradient in the furnace space. A fan is advantageous for circulating air in the furnace chamber, while process gases, for example protective gas or reaction gas, can be supplied with the aid of a metering valve to adjust the furnace atmosphere, in particular the furnace atmosphere's ability to oxidize.

There are now a large number of possibilities for designing and developing the method according to the invention and the device according to the invention. For this purpose, reference is made, on the one hand, to the claims subordinate to claims 1 and 11 and to the description of exemplary embodiments in conjunction with the drawing. The drawing shows in

La, b in a schematic representation, the plan view or the

Side view of an incandescent bubble created in a foil coil,

Fig. 2 in a schematic representation an embodiment of the device according to the invention,

3a, b show, in a schematic representation, advantageous embodiments of the method according to the invention, and

Fig. 4a, b in a diagram of test results of measurements of the

Furnace parameters in the case of a conventionally performed degreasing annealing and in the case of a degreasing annealing according to an advantageous embodiment of the method according to the invention. In FIG. 1 a, a metal foil 1, preferably an aluminum or aluminum alloy foil, is shown which has been wound up in two layers to form a coil 2 and conventionally soft-annealed at 220 ° C. to 250 ° C. in a heat treatment furnace. The coil 2 has a width of 250 mm to 2500 mm, in particular approx. 1000 mm or approx. 1700 mm. The winding height h is 18 mm, for example, which means that the film layers shown are very close to the core 3 of the coil 2.

A critical glow bubble 4 has formed on the film surface as a result of a conventionally carried out final annealing. On the inner surface of the bulb 4, scratches can be seen transversely to the direction of travel, with material having been pushed on at these points. The cross section of the incandescent bulb 4 in section AB is shown in detail in FIG. At the edge of the incandescent bubble 4 in the area X there is a compression of the material. The compression can be on the inside or on the outside of the incandescent bulb 4. In the area Y of the incandescent bubble 4, the film 1 has flow lines which indicate a constriction of the material and can lead to a crack or breakthrough in the metal film 1.

The aim of the method according to the invention is to avoid the formation of such incandescent bubbles and welding of the metal strips or foils, to provide high-quality metal products in a process-reliable and cost-effective manner and thereby to reduce the scrap portion of metal strips and foils. Damage to the metal surfaces in the form of impressions and scratches also leads to quality devaluations and rejects. On the other hand, film coils are rated as good if they have good running properties and have no or a significantly reduced local tendency to stick. Incandescent bubbles of acceptable form do not stick and can be slowed down without problems with increased tape tension. This also applies in particular to film layers that are located near the coil core 3, for example at a winding height of up to 12 mm or up to 18 mm. The problems known from the prior art can be solved with the aid of the method according to the invention for the heat treatment of metal strips or foils, in particular for the treatment of aluminum or aluminum alloy strips or foils, in the form of strip or foil coils 2 in a heat treatment furnace to remove rolling residues , solve in that the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas is determined while the heat treatment is being carried out and is used for process control or regulation of the heat treatment, the dynamics of the removal of rolling residues on the metal strips or foils is controlled or regulated during the heat treatment. The method according to the invention, which thus includes, for example, atmospheric control and regulation or regulation taking into account the kinetics of the evaporation and oxidation products, can ensure the flatness of the metal products and increase their quality accordingly. 2 shows an advantageous embodiment of a device according to the invention for the heat treatment of metal strips or foils, in particular for the removal of rolling residues, the device having at least one means 8 for determining the content of at least one evaporation and / or oxidation product in the furnace atmosphere 11 and / or in the process exhaust gas 12 while the heat treatment is being carried out and at least one means 9 for controlling or regulating the heat treatment, which are designed in such a way that they can be used to control or regulate the dynamics of the removal of rolling residues on the metal strips or foils during the heat treatment .

In the present case, the device is a heat treatment furnace 5, in particular a batch furnace, which has a furnace body 10 in addition to the furnace chamber 6, the furnace chamber 6 being arranged inside the furnace body 10 and for receiving metal strips or foils reeled into coils 2 an annealing rack (not shown here) is designed. The process air in the interior of the furnace chamber 6 is referred to as the furnace atmosphere 11. An exchange of process air takes place between the furnace chamber 6 and the environment, with process exhaust gas 12 being emitted from the furnace chamber 6. The heat treatment furnace 5 also has a fan 7 for circulating air in the furnace chamber 6.

The heat treatment furnace 5 has at least one means 8 for determining the content of at least one evaporation and / or oxidation product in the furnace atmosphere 11 and / or in the process exhaust gas 12 while the heat treatment is being carried out. In particular, the heat treatment furnace 5 has an FID analyzer, preferably an on-line FID analyzer, for determining the Vorg content, a CO analyzer, preferably an on-line CO analyzer, for determining the CO content and / or a CO 2 analyzer, preferably an on line CO 2 analyzer, for determining the CO 2 content in the furnace atmosphere 11.

A CO or CO2 analyzer can in particular be an infrared analyzer. Alternatively, the heat treatment furnace 5 can have at least one means 8 for determining the content of at least one evaporation and / or Have oxidation product in the process exhaust gas 12 (shown here by a dashed line).

The heat treatment furnace 5 also has at least one means 9 for controlling or regulating the heat treatment. The at least one means 9 for controlling or regulating the heat treatment is designed in particular for controlling or regulating the heat treatment depending on the content of at least one evaporation and / or oxidation product in the furnace atmosphere 11 and / or in the process exhaust gas 12. For example, at least one means 9 for controlling or regulating the furnace temperature, the furnace temperature gradient, the process air exchange volume and / or the circulating volume of process air depending on the content of at least one evaporation and / or oxidation product in the furnace atmosphere 11 and / or in the process exhaust gas 12 and / or at least one means 9 for controlling or regulating the furnace temperature gradient depending on the gradient of the content of at least one evaporation and / or oxidation product in the furnace atmosphere 11 and / or in the process exhaust gas 12 can be provided. In particular, a PID controller can be provided as the means 9 for controlling or regulating the heat treatment.

In order to be able to influence the heat treatment depending on the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas, at least one controllable means 13 for influencing the heat treatment, in particular a heater, a flap, a Fan and / or a metering valve are provided. With the aid of a heater or flap, it is possible, for example, to influence the temperature or the temperature gradient in the furnace space. A fan is advantageous for circulating air in the furnace chamber, while process gases, for example protective gas or reaction gas, can be supplied with the aid of a metering valve to adjust the furnace atmosphere, in particular the furnace atmosphere's ability to oxidize. The heat treatment furnace 5 according to the invention is therefore particularly suitable for carrying out the method according to the invention. For example, the heat treatment furnace 5 according to the invention can also be used to control or regulate the gas pressure of the evaporation and / or oxidation products in the strip or foil coil during the heat treatment. FIG. 3a shows an advantageous embodiment of the method according to the invention. In the present case, while the heat treatment is being carried out, in particular to remove rolling residues, the content G of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas is determined in step A and used for process control of the heat treatment in step C in step A. For example, the Vorg content in the furnace atmosphere and / or in the process exhaust gas can be determined, for example by means of an FID analyzer. The determination of the CO content, for example using a CO analyzer, and / or the determination of the CO 2 content, for example using a CO 2 analyzer, or the determination of the Ctot content using an FID analyzer and a CO analyzer and optionally a C 02 analyzer would be conceivable.

While the heat treatment is being carried out, in step B the actual value of the content of at least one evaporation and / or oxidation product Gist, for example the actual value C _{tot ist of} the Cges content, is used for process control of the heat treatment. For this purpose, the Gist value is compared with a nominal value Gsoii. This can be done manually, for example. The heat treatment is controlled depending on the Gist value. For example, at least one parameter P, e.g. B. the oven temperature, lowered in the event that the Gist value is greater than the Gsoii value. In the event that the Gist value is smaller than the Gsoii value, the parameter P is increased. This can also be done the other way around. If the Gist value is the same as the Gsoii value, the parameter remains unchanged. In addition to the furnace temperature, the furnace temperature gradient, the process air exchange volume and the circulating volume can also be set in the process control Process air and / or the composition of the furnace atmosphere depending on the content G of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas, e.g. B. depending on the C _total content, and / or the furnace temperature gradient depending on the gradient of the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas, e.g. B. be controlled depending on the C _ges gradient.

A further advantageous embodiment of the method according to the invention is shown in FIG. 3b. In the present case, while the heat treatment is being carried out, in particular to remove rolling residues, the content G of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas is determined in step A 'and used for process control of the heat treatment in step C'. Again, the V _or content may for example be in the furnace atmosphere and / or in the process gas, for example by means of a FID analyzer determined, wherein the determination of the CO content, for example by means of a CO analyzer, and / or the determination of the C02 content, for example by means of a C02 analyzer, or the determination of C _ges -content and a CO analyzer and C were by an FID analyzer 02 optionally conceivable.

While the heat treatment is being carried out, the actual value Gist of the content of at least one evaporation and / or oxidation product is used for process control of the heat treatment. As in the case of process control, the Gist value is also compared in step B 'with a setpoint value Gsoii. Depending on the Gist value, a parameter P, e.g. B. the furnace temperature, regulated. For example, the parameter P is lowered in the event that the Gist value is greater than the Gsoii value. In the event that the Gist value is smaller than the Gsoii value, the parameter P is increased, for example. This can also happen the other way around. If the Gist value is the same as the Gsoii value, the parameter P is left as it is. In addition to the furnace temperature, the furnace temperature gradient, for example, can also be used in the process control Process air exchange volume, the circulation volume of process air and / or the composition of the furnace atmosphere depending on the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas, e.g. B. depending on the C _total content, and / or the furnace temperature gradient depending on the gradient of the content of at least one evaporation and / or oxidation product in the furnace atmosphere and / or in the process exhaust gas, e.g. B. be regulated depending on the C _ges gradient.

In contrast to the control system, there is a closed operating sequence in the regulation. The Gist value is continuously compared with the Gsoii value and influenced by changing the parameter P in order to adjust it to the Gsoii value.

A PID controller, for example, can be used for process control.

In Fig. 4a the writing of an FI D analyzer is shown during a conventional finish annealing on an aluminum foil coil with a width of 1616 mm. The final annealing was carried out at a program temperature of 330 ° C for a duration of almost 72 hours. The diagram shows the CO content [ppm], the oven and program temperature [° C], the air volume [m ³ / h] and the fan speed [rpm] as a function of time [h]. Content was carried out in the present case in the furnace atmosphere. This allows conclusions to be drawn about the content of evaporation and / or oxidation products in the furnace atmosphere. Alternatively, however, the CO content can also be determined in the process exhaust gas. Further alternatively or additionally, the V _or can be - and / or the CO-content or the C _tot content in the furnace atmosphere and / or process exhaust gas to be determined.

The diagram shows very clearly that with conventional finish annealing, a COmax peak of 1000 ppm in the furnace atmosphere occurs after a short time. The CO gradient in this case was about 200 ppm / h. However, extensive tests have shown that, for example, COmax peaks of more than 220 ppm and CO gradients of more than 10 ppm / h reflect a negative annealing result. It has been shown that with an appropriate furnace atmosphere there is tension, welds and the formation of incandescent bubbles in the metal foil. In the worst case, these in turn can lead to cracks in the film when the coil is being unwound. In the diagram in FIG. 4b, on the other hand, the COmax content was limited to only approx. 70 ppm, the COmax gradient is approx. 5.5 ppm / h. The program temperature was set at 220 ° C., the amount of air was ^{kept constant at about 280 m 3} / h and the speed of rotation was kept constant at about 640 rpm. As can be seen from the graph, the formation of a pronounced CO peak during the annealing treatment could be avoided in the present case. In order to achieve this, according to the method according to the invention, the furnace temperature was controlled or regulated depending on the CO content in the furnace atmosphere. While both the furnace temperature and the CO content in the furnace atmosphere rise uniformly up to the point in time of about ten hours (cf. dashed line), the furnace temperature was lowered at the critical value of about 50 ppm of CO content. The CO gradient then flattens out and is now only around 1.4 ppm / h until the CO content drops again after around 24 hours. In this way, tensions and the formation of incandescent bubbles in the metal foil can be reduced or avoided, high-quality metal products can be made available in a process-reliable and cost-effective manner, and the proportion of rejects on metal strips and foils can be reduced.

Claims

1. A method for the heat treatment of metal strips or foils (1) in the form of strip or foil coils (2) in a heat treatment furnace (5) for the removal of rolling residues, characterized in that the content of at least one evaporation and / or oxidation product is determined in the furnace atmosphere (11) and / or in the process exhaust gas (12) and is used for process control or regulation of the heat treatment, the dynamics of the removal of rolling residues on the metal strips or foils during the heat treatment being controlled or regulated becomes.

2. The method according to claim 1, characterized in that the gas pressure of the evaporation and / or oxidation products in the strip or foil coil is controlled or regulated during the heat treatment.

3. The method according to claim 1 or 2, characterized in that in the process control or regulation the furnace temperature, the furnace temperature gradient, the process air exchange volume, the circulating volume of process air and / or the composition of the furnace atmosphere depending on the content of the at least one evaporation and / or oxidation product in the furnace atmosphere (11) and / or in the process exhaust gas (12) is controlled or regulated.

4. The method according to any one of claims 1 to 3, characterized in that in the process control or regulation of the furnace temperature gradient depending on the gradient of the content of the at least one evaporation and / or oxidation product in the furnace atmosphere (11) and / or in the process exhaust gas ( 12) is controlled or regulated.

5. The method according to any one of claims 1 to 4, characterized in that the carbon content (C _total content), the content of organic compounds (Vorg content), the carbon monoxide content (CO content) and / or the carbon dioxide content (C02- Content) is determined in the furnace atmosphere (11) and / or in the process exhaust gas (12) and is used for process control or regulation of the heat treatment.

6. The method according to claim 5, characterized in that in the furnace atmosphere (11) and / or in the process exhaust gas (12) the maximum carbon content C _{tot max} , the maximum content of organic compounds Vor _max , the maximum carbon monoxide content COmax, and / or the maximum carbon dioxide content CO2 max is limited.

7. The method according to claim 5 or 6, characterized in that in the furnace atmosphere (11) and / or in the process exhaust gas (12) the carbon _{gradient C total degree} , the gradient of the content of organic compounds VorgGrad, the carbon monoxide gradient COcrad and / or the Carbon dioxide gradient CO2 degree is limited.

8. The method according to any one of claims 5 to 7, characterized in that the before _g content by an FID analyzer, preferably an on-line FID analyzer, the CO content by a CO analyzer, preferably an on line CO analyzer, the C0 ₂ content by a C0 ₂ analyzer preferably, an on-line analyzer C0 _2, and / or the C _tot content by an FID analyzer, and a CO analyzer and optionally a C0 ₂ analyzer is determined.

9. The method according to any one of claims 1 to 8, characterized in that the heat treatment at a temperature of 80 to 120 ° C or more than 200 ° C, preferably more than 220 ° C, particularly preferably more than 300 ° C is carried out.

10. The method according to any one of claims 1 to 9, characterized in that

Aluminum or aluminum alloy strips or foils are treated.

11. Device for the heat treatment of metal strips or foils (1) in the form of tape or foil coils (2) for performing a method according to one of claims 1 to 10, characterized in that the device has at least one means (8) for determining the Content of at least one evaporation and / or oxidation product in the furnace atmosphere (11) and / or in the process exhaust gas (12) while the heat treatment is being carried out and at least one means (9) for controlling or regulating the heat treatment depending on the content of at least one evaporation and / or oxidation product in the furnace atmosphere (11) and / or in the process exhaust gas (12), which are designed such that the Dynamics of the removal of rolling residues on the metal strips or foils during the heat treatment is controlled or regulated.

12. The device according to claim 11, characterized in that the device has at least one means (9) for controlling or regulating the furnace temperature, the furnace temperature gradient, des

Process air exchange volume and / or the circulation volume of process air depending on the content of at least one evaporation and / or oxidation product in the furnace atmosphere (11) and / or in the process exhaust gas

(12).

13. The device according to claim 11 or 12, characterized in that the device has at least one means (9) for controlling or regulating the furnace temperature gradient depending on the gradient of the content of at least one evaporation and / or oxidation product in the furnace atmosphere (11) and / or in the process exhaust gas (12).

14. Device according to one of claims 11 to 13, characterized in that the device has at least one controllable means (13) for influencing the heat treatment.