Method for heat treatment of a metal strip

Abstract

The invention relates to a method for heat treatment of a metal strip where the metal strip is exposed to a heating section and subsequently exposed to a cooling section, wherein in the heating step flames from a burner are directed towards the surface of the metal strip so as to impinge on the surface of the metal strip, and wherein in the cooling step the metal strip is exposed to at least one jet of cooling gas and at least one jet of a liquified gas.

Description

[0001] P40214-EP

[0002] 09.10.2025 - Dr. Bernd Gellner

[0003] 1

[0004] Method for heat treatment of a metal strip

[0005] The present invention relates to a method for heat treatment of a metal strip wherein the metal strip is exposed to a heating step and wherein the metal strip is subsequently exposed to a cooling step, wherein in the heating step flames from a burner are directed towards the surface of the metal strip so as to impinge on the surface of the metal strip, and wherein in the cooling step the metal strip is exposed to at least one jet of a liquified gas and to at least one jet of a cooling gas

[0006] Currently, it is difficult to process aluminium strips without annealing due to the hardening of the material during production and processing. Whether intermediate annealing or finished product annealing, annealing is a time-consuming and energy- intensive process. The intermediate annealing process is especially time-consuming, leading to a large volume of occupied aluminium on work sites, creating environmental and production scheduling issues. The use of electric heat sources in the annealing process also contributes to the high energy costs associated with aluminium processing.

[0007] There is a need to develop a more suitable method for continuous heat treatment of non-steel metal strips, especially of aluminium strips, capable of reducing energy consumption and operating costs. Additionally, the existing batch annealing furnaces suffer from slow processing speeds and non-uniform heating across the width and length of the strip.

[0008] Therefore, the objective of this invention is to provide a new continuous heat treatment method for metal strips, with faster heating and cooling, reducing the carbon footprint, lowering heat treatment time, and accommodating shorter production lines.

[0009] This objective is achieved by a process for heat treatment of a metal strip where the metal strip is exposed to a heating step and subsequently exposed to a cooling step, wherein in the heating step flames from a burner are directed towards the surface of the metal strip so as to impinge on the surface of the metal strip, and wherein in the cooling step the metal strip is exposed to at least one jet of a liquified gas and to at least one jet of a cooling gas and wherein the jet of the cooling gas is applied so close to the jet of the liquified gas that a turbulence is caused. P40214-EP

[0010] 09.10.2025 - Dr. Bernd Gellner

[0011] 2

[0012] A metal strip may be understood as a thin flexible sheet of metal, usually less than 3mm or less than 1 mm thick, for example with a thickness between 50 and 500 micrometer, preferably with a thickness between 100 to 200 micrometer. The process comprises exposing the metal strip to a heating step and subsequently exposing it to a cooling step. In the heating step flames from a burner are directed towards the surface of the metal strip, so as to impinge on the surface of the metal strip and to heat it up rapidly. The flames directly impinge on the surface of the metal strip so that a very fast heating is achieved. The heating step is preferably carried out in a heating section which comprises at least one burner, preferably an oxyfuel burner.

[0013] During the cooling step the metal strip is exposed to one or more jets of a cooling gas and to one or more jets of a liquified gas.

[0014] One advantage of this arrangement is that it greatly improves the homogeneity of heating and cooling. The inventive method combines very fast heating by using direct flame impingement with ultrafast cooling by means of the liquified gas. The direct flame impingement alters the properties of the metal material and allows to achieve a specific material microstructure. The subsequent ultrafast cooling freezes the specific material microstructure. The use of a liquified gas ensures high accuracy and efficiency of cooling, which leads to better thermal homogeneity along the width and the length of the metal strip.

[0015] In the prior art heat treatment process the metal strip is first annealed in conventional heat treating furnaces, for example in an annealing furnace, which do not provide such fast and homogenuous heating of the metal strip as the invention. The inventive method combines very fast heating with a very homogenuous heating across the whole width of the metal strip. Thereby, it is possible to achieve a well-defined metal microstructure in short time.

[0016] In conventional air cooling the hot metal strip is cooled down relative slow. During that slow cooling process the remaining heat in the material can affect the material microstructure and unwanted modifications of the grain structure might be created. By using the inventive cooling step the microstructure produced in the heating step is frozen. This allows to precisely manipulate the mechanical properties of the metal strip, P40214-EP

[0017] 09.10.2025 - Dr. Bernd Gellner

[0018] 3 such as hardness, strength, elasticity and ductility. The invention avoids unwanted growth of the grain size. On the contrary, fine and even grain size can be created. The material quality is improved.

[0019] Another benefit of the inventive method is that the cooling section where the cooling step is carried out is shorter than prior art cooling sections such that less space is needed.

[0020] It has been found that spraying the liquified gas alone does not provide the same good results and benefits as described above. It is assumed that after spraying the liquified gas will remain on the metal surface for some time, form a kind of insulation and thereby reduce the cooling effect. Thus, the inventors propose to additionally apply one or more jets of a cooling gas onto the metal strip. The jet of cooling gas is applied so close to the jet of liquified gas that it will cause a turbulence which improves the cooling effect. Thereby, the consumption of liquified gas can be significantly reduced.

[0021] The term “turbulence” shall in particular mean that the cooling gas jet interacts with the liquified gas so that at the surface of the metal strip the resulting mixture of liquified gas and cooling gas shows a swirling or fluctuating behaviour and I or that the liquified gas and the cooling gas are strongly mixed. Any kind of Leidenfrost phenomenon is effectively prevented.

[0022] The term “cooling gas” shall mean a fluid in its gaseous state. It comprises any gas which has a temperature which is below the temperature of the hot metal strip after it has been passed through the heating section. Preferably, the cooling gas has a temperature below 100°C or preferably around ambient temperature or below ambient temperature. Preferred cooling gases are air, gaseous nitrogen and I or gaseous carbon dioxide.

[0023] The invention relates to a continuous heat treatment process. The metal strip is continuously passed through a heating section where the heating step is carried out and through a cooling section where the cooling step is carried out.

[0024] In an embodiment of the invention the metal strip is provided as a coil. The metal strip is then uncoiled, passed through the heating section and through the cooling section P40214-EP

[0025] 09.10.2025 - Dr. Bernd Gellner

[0026] 4 and finally coiled again. During the whole process of uncoiling, passing through the heating section and the cooling section and final re-coiling the tension of the metal strip may be detected and controlled.

[0027] In an embodiment of the invention, the maximum distance between the jet of liquified gas and at least one jet of cooling gas is between 100 mm and 1000 mm, between 100 mm and 500 mm or between 100 mm and 300 mm. The main direction of the jet of liquified gas and the main direction of the jet of cooling gas are preferably parallel lines and the distance between these lines is between 100 mm and 1000 mm, between 100 mm and 500 mm or between 100 mm and 300 mm. If the main direction of the jet of liquified gas and the main direction of the jet of cooling gas are not parallel, the distance between the jet of liquified gas and at least one jet of cooling gas shall be the distance of the respective impingement points on the metal strip. In any case, at the surface of the metal strip the liquified gas and the cooling gas shall be in so close proximity that they affect each other and that a turbulence is caused.

[0028] Typically more than one jet of liquified gas is directed to the metal strip. In that case it is preferred that each of the jets of liquified gas is so close to a jet of cooling gas that a turbulence is caused. Preferably, the maximum distance between any of the jets of liquified gas and at least one of the jets of cooling gas is 1000 mm or 500 mm or 300 mm. In other words, no jet of liquified gas is more than 1000 mm or 500 mm or 300 mm away from a jet of cooling gas. Thereby, it is ensured that each jet of liquified gas becomes turbulent at the surface of the metal strip.

[0029] In an embodiment several jets of liquified gas and several jets of cooling gas are directed to the metal strip.

[0030] In one embodiment the metal strip is alternately exposed to jets of cooling gas and jets of liquified gas. The cooling section may comprise one or more rows of cooling gas jets and rows of liquified gas jets. The rows of cooling gas jets and rows of liquified gas jets are preferably arranged perpendicular to the direction of metal strip movement. The distance between two rows is preferably between 100 mm and 500 mm or between 100 mm and 300 mm. The first and / or the last row is preferably a row of cooling gas jets. The cooling gas jets would not only support the cooling effect but additionally block outside air from entering the cooling section. P40214-EP

[0031] 09.10.2025 - Dr. Bernd Gellner

[0032] 5

[0033] Another advantage of this arrangement is that it is capable of handling continuous materials. Continuous metal strip can be continuously transported through the heating section and the cooling section which improves the production speed, reduces the production time and guarantees more uniform heating rate and cooling rate along the width and the length of the moving strip.

[0034] In addition, the ability to connect multiple heating and cooling sections, in series, but not necessarily in direct contact with the continuous metal strip, enables continuous heat treatment of surface-sensitive materials. The rapid cooling of the metal strip using a liquified gas prevents oxidation and surface damage during the heat treatment process. This arrangement can be used for preheating and annealing, solid solution heat treatment, and degreasing of metal and metal matrix composite material strips.

[0035] The inventive process is preferably used for the heat treatment of metals other than steel. A non-steel metal strip may be understood as a metal strip comprising a metal other than steel. Examples of non-steel metals include but are not limited to aluminium, copper, titanium, nickel, and their alloys and their cladding material, like Cu / AI or stainless steel / AI. The thickness of the metal strip is typically less than 3mm, for example between 10 micrometer and 500 micrometer.

[0036] It may be provided that liquid nitrogen is sprayed onto the surface of the metal strip. By spraying liquid nitrogen onto the surface of the metal strip, the heat treatment process is able to achieve a rapid and homogeneous cooling. The use of liquid nitrogen also prevents oxidation and surface damage during the heat treatment process, resulting in a better product quality. The cooling of the metal strip may also be achieved by using liquid carbon dioxide as the liquified gas.

[0037] Preferably, the temperature of the liquified gas is below -160 °C. The low temperature ensures a rapid cooling so that the desired material microstructure is achieved. The cooling section can be significantly shorter than conventional cooling sections based on air cooling.

[0038] It may be provided that the liquified gas is sprayed through a plurality of nozzles or slots. For example, a liquid storage tank and a pressure regulating valve group are P40214-EP

[0039] 09.10.2025 - Dr. Bernd Gellner

[0040] 6 connected to the nozzles. This arrangement ensures that the liquified gas, for example liquid nitrogen, is evenly distributed across the surface of the metal strip, further enhancing the thermal homogeneity along the width and the length of the metal strip.

[0041] In an embodiment the cooling gas is sprayed through a plurality of nozzles or slots. The nozzles and I or slots are preferably arranged in close proximity to the jet or jets of the liquified gas. Thereby, a turbulent gas layer or gas flow is created across the whole width of the metal strip and the liquified gas is distributed across the metal strip as good as possible. This can be achieved by selecting an appropriate number of nozzles or slots and I or by designing the nozzles and I or slots accordingly. In any case, the distance between the jet of cooling gas and the jet of liquified gas is so small that the liquified gas is affected by the jet of the cooling gas.

[0042] The nozzles or slots for the liquified gas and the nozzles or slots for the cooling gas are preferably arranged such that the jets of liquified gas and cooling gas, respectively, are directed at an angle between 60° and 120° towards the metal strip. In one embodiment the angle is between 75° and 105° towards the metal strip. Preferably, the nozzles and slots are adjustable so that their spraying angle can be set according to the type of material, the material thickness, the metal strip speed and surface requirements.

[0043] The distance between two nozzles or slots for the cooling gas is preferably between 50 mm and 500 mm, between 100 mm and 300 mm or between 150 mm and 250 mm.

[0044] The nozzles or slots for the cooling gas are preferably arranged in one or more rows perpendicular to the direction of metal strip movement.

[0045] The distance between two nozzles or slots for the liquified gas is preferably between 50 mm and 500 mm, between 100 mm and 300 mm or between 150 mm and 250 mm.

[0046] The nozzles or slots for the liquified gas are preferably arranged in one or more rows perpendicular to the direction of metal strip movement.

[0047] The distance between a nozzle for the liquified gas and the closest nozzle for the cooling gas is preferably between 50 mm and 500 mm, between 100 mm and 300 mm or between 150 mm and 250 mm. P40214-EP

[0048] 09.10.2025 - Dr. Bernd Gellner

[0049] 7

[0050] In a preferred embodiment the inventive method is used for heat treatment of a metal strip made of a composite material. The term composite material shall mean a material which is made from two or more different constituent materials. These constituent materials have different chemical and I or physical properties and are merged to create a material with properties different from the individual constituent materials. Within the metal strip the individual constituents shall remain separate and distinct and provide specific properties. Therefore, it is essential that during the heating step and during the cooling step no material diffuses from one of these constituent materials into the other constituent material. Otherwise, the properties of both materials would be mixed. By using the very fast heating step and the very fast cooling step according to the invention such diffusion is avoided or at least minimized.

[0051] The invention is preferably useful for heat treatment of two layer or multi layer composites, for example a metal strip made up out of two or more layers of different material. This comprises but is not limited to composites comprising one or more layers of aluminium, copper, steel, nickel, magnesium, lithium or their alloys. Examples are aluminium I steel composites, aluminium I steel I aluminium composites, steel I aluminium I steel composites, magnesium alloy strips, lithium alloy strips, nickel strips, AI / AI strips, Al / Cu strips, Al / Mg strips and so on.

[0052] It may be provided that an oxidant and a fuel are fed to the burner and that the oxidant contains at least 80% by volume oxygen. An oxidant containing at least 80% by volume oxygen ensures high combustion efficiency and enables high-temperature heat treatment. The use of such an oxyfuel burner enables rapid heating of the metal strip, resulting in a significantly faster heating rate compared to static coil annealing.

[0053] It may be provided that the burner has a burner outlet for the fuel, for the oxidant, and / or for the fuel / oxidant mixture and that the distance from the burner outlet to the metal strip is 50 to 300 millimeters. The burner outlet may be understood as the part of the burner that releases the fuel, oxidant, and / or fuel / oxidant mixture. The distance between the burner outlet and the metal strip ensures a high heating efficiency and homogeneity of the temperature field along the width and length of the metal strip. P40214-EP

[0054] 09.10.2025 - Dr. Bernd Gellner

[0055] 8

[0056] It may be provided that the total power applied by the burner is 200 KW to 1000 KW per meter metal strip. This arrangement enables the desired heating rate to be achieved while maintaining a high level of energy efficiency.

[0057] It may be provided that the metal strip is passed through the heating section at a speed of 150 to 200 meters / minute. By passing the metal strip through the heating section at a high speed, a significant reduction in production time can be achieved.

[0058] It may be provided that at least one parameter of the metal strip is online determined during the heat treatment process and that the heating step is dynamically adjusted depending on the determined parameter. The online parameter determination inspection may be understood that the parameter is determined during the heat treatment process, i.e. while the metal strip is passed through the heating section. By determining at least one parameter of the metal strip during the heat treatment process, the quality of the finished product can be improved. The heating section and I or the parameters of the heating step can be dynamically adjusted depending on the determined parameter, ensuring a uniform heating rate along the width and length of the metal strip.

[0059] It may be provided that the heating section and I or the heating step are adjusted by means of an Al control system. An Al control system may be understood as a control system that utilizes artificial intelligence and machine learning algorithms to optimize control parameters. This arrangement ensures that the heating temperature is precisely controlled, resulting in improved uniformity of processing and reduced energy consumption. An advantage of this arrangement is that the heat treatment process can be controlled to meet specific quality standards, resulting in a consistently high-quality finished product.

[0060] The invention is schematically illustrated using an exemplary embodiment as shown in the drawing: P40214-EP

[0061] 09.10.2025 - Dr. Bernd Gellner

[0062] 9

[0063] Figure 1 shows the heat treatment of a non-steel metal strip along a treatment line according to the invention

[0064] Figure 2 shows the inventive cooling section.

[0065] An aluminium strip 1 is provided as a coil 2. The aluminium strip 1 may have a width up to 2500 mm and a thickness between 10 micrometer and 3000 micrometer, preferably between 15 micrometer and 1500 micrometer. The length of the strip 1 may be several kilometers. The coil 2 may have an outer diameter up to 2000 mm and a weight up to 301.

[0066] The metal strip 1 is unwound or uncoiled from a coil 2 and passed through a heating section 3. The processing speed of the metal strip 1 is up to 300 m / min. During its passage through the heating section 3 the aluminium strip 1 is subjected to one or more direct flame heating devices 31 such as an oxyfuel heating device. In figure 1 the aluminium strip 1 is arranged in such a way that its surface is essentially horizontal. The heating devices 31 are arranged above and I or below the strip 1. In another embodiment not shown in the drawing the metal strip is vertically oriented. In that case the heating devices 31 would be provided on both sides of the surface of the metal strip.

[0067] The heating devices 31 are oxyfuel direct flame impingement (DFI) burners. Fuel 32 and oxygen 33 are provided from respective sources, for example a fuel tank and an oxygen tank, passed through a flowtrain 34 which controls the flow of fuel and oxygen to the DFI burners 31. Fuel 32 and oxygen 33 are combusted in the DFI burners 31. The DFI burners 31 are arranged so that the distance between the burner outlets and the passing metal strip is between 100 mm and 200 mm. Thereby, it is guaranteed that the metal strip 1 is directly exposed to the resulting flames of the DFI burners 31 and that the flames impinge onto the surface of the metal strip 1.

[0068] After the heat treatment in the heating section 3 the metal strip 1 is passed to and through a cooling section 4. The cooling unit 4 is provided with a plurality of nozzles 41 and gas slots 45. A liquid nitrogen tank 42 is connected to the plurality of nozzles 41 via a flowtrain 44 which allows to control the flow of liquid nitrogen 42. A source of gaseous nitrogen 43 is connected to the plurality of slots 45 via a flowtrain 46 which allows to control the flow of gaseous nitrogen 43. The liquid nitrogen 42 is sprayed onto P40214-EP

[0069] 09.10.2025 - Dr. Bernd Gellner

[0070] 10 the surface of the metal strip 1 in order to rapidly cool down the metal strip 1. In addition, gaseous nitrogen 43 is sprayed onto the metal strip 1 through the slots 45.

[0071] The metal strip 1 after having left the cooling section 4 is coiled up on a coil 5.

[0072] During the heat treatment and during the cooling phase the metal strip 1 experiences changes in length and width due to thermal expansion. In order to compensate any thermally induced changes in the dimensions of the metal strip 1 tension frames may be provided which apply a pulling force onto the metal strip 1.

[0073] Monitoring devices 6 and 7 are provided downstream of the heating section 3 and downstream of the cooling section 4. The monitoring devices 6, 7 determine at least one parameter of the passing metal strip 1 after it has been heat treated and after it has been cooled, respectively. The determined parameters are sent to a control unit 8. The control unit 8 analyzes the parameters and I or compares the determined parameters with one or more preset values. Depending on the outcome of this analysis the control unit 8 controls one or more of the heating section 3, and especially the heating power, the cooling section 4, and in particular the cooling rate and the liquid and I or gaseous nitrogen flow, the speed of the metal strip and the tension of the metal strip.

[0074] Figure 2 shows the cooling section 4 in more detail. The metal strip 1 enters the cooling section 4 and a plurality of gas jets is directed onto the surface of the metal strip 1. The gas jets are provided from one row of gas slots 45 arranged above the metal strip 1 and from one row of gas slots 45 arranged below the metal strip 1. The gas slots 45 are equally distributed along the width of the metal strip 1. The gas slots 45 are connected to the source of gaseous nitrogen 43, for example a nitrogen gas cylinder, a gas cylinder bundle or a nitrogen tank. A flow train 46 allows to control the nitrogen flow to the gas slots 45. The nitrogen gas is sprayed through the slots 45 onto the metal strip 1. The angle of the spray direction to the surface of the metal strip 1 is between 80° and 100°, for example it is vertical to the surface of the metal strip 1.

[0075] The metal strip 1 is then passed through a plurality of jets of liquid nitrogen. The liquid nitrogen jets are provided from one row of nozzles 41 arranged above the metal strip 1 and from one row of nozzles 41 arranged below the metal strip 1. The nozzles 41 are P40214-EP

[0076] 09.10.2025 - Dr. Bernd Gellner

[0077] 11 equally distributed along the width of the metal strip 1. The nozzles 41 are connected to the source of liquid nitrogen 42, for example a liquid nitrogen tank. A flow train 44 allows to control the liquid nitrogen flow to the nozzles 41. The liquid nitrogen is sprayed through the nozzles 41 onto the metal strip 1. The angle of the spray direction to the surface of the metal strip 1 is between 80° and 100°, for example it is vertical to the surface of the metal strip 1.

[0078] The number of nozzles 41 and the design and size of the nozzles 41 can be chosen according to the heating profile of the metal strip 1 after passing the heating section 3. In the embodiment of figure 2 a homogenuous heating profile along the width of the metal strip 1 is assumed. Therefore, the nozzles 41 are arranged at equal distances from each other. If for example the heating profile of the heating section 3 is such that the center of the metal strip 1 is heated more than the edges of the metal strip 1 , more nozzles 41 and I or nozzles 41 of larger throughput are arranged near the center of the metal strip 1.

[0079] The number of nozzles 41 is designed according to the cooling capacity needed.

[0080] Thereby, the metal strip 1 is cooled as much as needed without over-cooling the metal strip 1. The rows of gas slots 45 and nozzles 41 are arranged alternating. The distance between a row of gas slots 45 and a row of nozzles 41 is preferably between 100 mm and 300 mm. Figure 2 shows a row of gas slots 45, a row of liquid nitrogen nozzles 41 and a row of gas slots 45 in the direction of movement of the metal strip 1. One skilled in the art will understand that the number of rows of gas slots 45 and nozzles 41 can be adapted to the cooling needs.

[0081] In another embodiment not shown in the figures a row comprises gas slots 45 for the cooling gas and nozzles 41 for the liquified gas. Preferably, the gas slots 45 and the nozzles 41 are arranged alternately within one row.

[0082] The inventive combination of gas slots 45 and liquid cryogen nozzles 41 ensures that the metal strip 1 is cooled properly with a minimum of liquid nitrogen consumption. The jets of gaseous nitrogen support the cooling effect by creating a turbulence above the surface of the metal strip 1. The gaseous nitrogen and any evaporated liquid nitrogen further provide an inert atmosphere in the cooling section 4 which prevents oxidation of the hot metal strip 1 passed through the cooling section 4. P40214-EP

[0083] 09.10.2025 - Dr. Bernd Gellner

[0084] 12

[0085] By controlling the flowrate and / or velocity of liquid nitrogen and I or gaseous nitrogen and by arranging the number and orientation of the gas slots 45 and of the nozzles 41 the cooling can be controlled to get a flat metal strip 1 after the cooling step.

Claims

P40214-EP09.10.2025 - Dr. Bernd Gellner13Claims1. Method for heat treatment of a metal strip (1) wherein the metal strip (1) is exposed to a heating step (3) and wherein the metal strip (1) is subsequently exposed to a cooling step (4), wherein in the heating step (3) flames from a burner (31) are directed towards the surface of the metal strip (1) so as to impinge on the surface of the metal strip (1), and wherein in the cooling step (4) the metal strip (1) is exposed to at least one jet (41) of a liquified gas (42) and to at least one jet (45)of a cooling gas (43), characterized in that the jet (45) of the cooling gas (43) is applied so close to the jet (41) of the liquified gas (42) that a turbulence is caused.

2. Method according to claim 1, characterized in that the liquified gas (42) consists of or comprises liquid nitrogen or liquid CO2.

3. Method according to any of the preceding claims, characterized in that the cooling gas (43) consists of or comprises air, nitrogen and I or CO2.

4. Method according to any of the preceding claims, characterized in that the distance between the jet (41) of liquified gas (42) and the jet (45) of cooling gas (43) is between 100 mm and 1000 mm, between 100 mm and 500 mm or between 100 mm and 300 mm.

5. Method according to any of the preceding claims, characterized in that the metal strip (1) is exposed to more than one jet (41) of liquified gas (42) and to more than one jet (45) of cooling gas (43) and that the maximum distance between any of the jets of liquified gas and at least one jet of cooling gas is 1000 mm or 500 mm or 300mm.

6. Method according to any of the preceding claims, characterized in that the cooling step is carried out in a cooling section (3), that the metal strip (1) is passed through the cooling section (3) and that in its direction of passage the metal strip (1) is alternately exposed to a jet (45) of cooling gas (43) and to a jet (41) ofP40214-EP09.10.2025 - Dr. Bernd Gellner14 liquified gas (42).

7. Method according to any of the preceding claims, characterized in that the liquified gas and I or the cooling gas are sprayed through a plurality of nozzles or slots.

8. Method according to any of the preceding claims, characterized in that the liquified gas (42) has a temperature of less than -160 °C.

9. Method according to any of the preceding claims, characterized in that an oxidant (33) and a fuel (32) are fed to the burner (31) and that the oxidant (33) contains at least 80 % by volume oxygen.

10. Method according to any of the preceding claims, characterized in that the burner (31) has a burner outlet for the fuel, the oxidant and I or the mixture of fuel and oxidant and that the distance from the burner outlet to the metal strip (1) is 10 to 500 millimeters.

11. Method according to any of the preceding claims, characterized in that the total power applied by the burner is 50 KW to 5000 KW per meter metal strip.

12. Method according to any of the preceding claims, characterized in that the heating step is carried out in a heating section (3) and that the cooling step is carried out in a cooling section (4) and wherein the metal strip (1) is passed through the heating section (3) and through the cooling section (4) at a speed of 5 to 1000 meters / m inute.

13. Method according to any of the preceding claims, characterized in that at least one parameter of the metal strip (1) is online determined during the heat treatment method and that the heating step (3) and I or the cooling step (4) are dynamically adjusted depending on the determined parameter.

14. Method according to any of the preceding claims, characterized in that the metal strip (1) is made of a nonferrous metal, in particular of aluminium or an aluminiumP40214-EP09.10.2025 - Dr. Bernd Gellner15 alloy.

15. Method according to any of the preceding claims, characterized in that the metal strip (1) is made of a composite material, in particular that the metal strip comprises two or more layers of different material.

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