Method for transverse cutting a metal strip and rolling machine with shears for transverse cutting a metal strip

Abstract

The invention relates to a method for cutting a metal strip to length by means of at least one cutter (1), comprising the following steps: A) determining at least one target cutting time at a cutting site of the rolling mill according to a target length of the metal strip; B) determining the shear strength of the metal strip at the cutting site at the target cutting time; C) triggering a cutting action at the target cutting time if the shear strength of the metal strip at the cutting site at a target cutting time is less than or equal to a threshold shear strength of the metal strip specified for the cutter; or D) blocking the cutting action at the target time if the shear strength of the metal strip at the target cutting time at the cutting site is greater than the threshold shear strength.

Description

[0001] The invention relates to a method for cutting a metal strip transversely using at least one shear in a rolling mill.

[0002] The invention further relates to a rolling plant comprising means for cutting to length and rolling a metal strip in at least one rolling line with at least one rolling device, at least one shear designed for cutting the metal strip into sections of predetermined length, and at least one higher-level process control for automating the plant.

[0003] The rolling mill is specifically designed as a so-called CSP ®< plant (Compact Strip Production) for the quasi-continuous casting and rolling of slabs.

[0004] The CSP® process developed by the applicant is a method in which liquid steel is cast into slabs in a continuous casting machine. The cast strand is cut into slabs by a shear and homogenized in a furnace to rolling temperature, and if necessary, heated, before being rolled in a hot rolling mill. The shear, which cuts individual slabs from the strand continuously exiting the machine, is designed to allow the hot strand to be cut even under demanding process conditions, i.e., at low temperatures, when processing high-strength material, and with large cutting widths. Depending on the cutting conditions, the shear may be subject to increased wear. Under the most unfavorable conditions, the shear can be damaged, leading to failure.

[0005] It is known in the prior art to improve the wear behavior of plant components by guiding the process.

[0006] Such a method for improving the wear behavior of plant components during the further processing of high-alloy steels, as well as a plant for processing these high-alloy steels, is known, for example, from DE 10 2016 109 489 A1. The method known from this publication provides for controlling the cooling of the casting product in such a way that the highest temperature in the cross-section of the casting product falls below the zero-toughness temperature at the end of the casting machine and before the first forming step, but at least before any mechanical cutting of the casting product by means of shears, at least temporarily for the respective processing step. In particular, it is provided that the secondary cooling of the metal strip is specifically controlled so that the strand is not in the range of the zero-toughness temperature during shearing. This protects the shears, in particular, from premature wear.

[0007] A method for slitting a metal strip is also known, for example, from EP 3 177 412 B1. This method also relates to setting a specific temperature profile at the strip head and strip foot before slitting a metal strip.

[0008] DE 10 2019 217839 A1 discloses a method for cutting a metal strip transversely using at least one cutting device. The method described in this document involves calculating the actual value of a characteristic parameter for a longer section of the metal product to be manufactured, where the characteristic parameter represents the metal product's resistance to cutting or forming processes. Only if the actual value of the metal product's characteristic parameter is less than the threshold value, i.e., if the device's capacity is sufficient to cut or form the metal product, does the cutting or forming process actually take place. This makes it possible to avoid momentary overloading or damage to the cutting or forming device.The invention is based on the objective of providing a method for cutting a metal strip of the type mentioned at the outset across its width, which also contributes to improving the wear behavior of the scissors.

[0009] The invention further aims to provide a rolling mill designed in such a way as to ensure low-wear operation of the shear.

[0010] The problem is solved by providing a method with the features of claim 1 and by providing a rolling mill with the features of claim 5. Advantageous embodiments of the invention are set forth in the dependent claims.

[0011] One aspect of the invention relates to a method for cutting a metal strip transversely using at least one shear in a rolling mill, comprising the following process steps: A) Determining at least one target cutting time at a cutting point of the rolling mill as a function of a target length of the metal strip, B) Determining the shear strength of the metal strip at the cutting point at the target cutting time, C) Triggering a cut at the target cutting time if the shear strength of the metal strip at the cutting point at a target cutting time is less than or equal to a limit shear strength of the metal strip given for the shear, or D) Blocking the cut at the target cutting time if the shear strength of the metal strip at the cutting point at the target cutting time is greater than the limit shear strength.

[0012] The shears used in the process can be designed as pendulum shears, crank shears, drum shears or the like.

[0013] A metal strip within the meaning of the invention is understood to be a flat metal product that, as a semi-finished product in the form of slabs, blocks, or billets, is fed continuously or discontinuously to a rolling mill and is to be cut before and / or during processing in a rolling mill. The term "metal strip" also includes intermediate products and pre-products, such as hot-rolled strip or cast strands that emerge from the outlet of a continuous casting machine connected to the rolling mill and are cut into slabs in the rolling mill and further rolled into strip.

[0014] The process applies in particular to the transverse cutting of metal strips at a temperature of more than 300 degrees C.

[0015] The rolling mill according to the present invention is preferably one for producing strips of a final thickness of 0.6 to 25.4 mm from cast slabs, which may, for example, have a thickness of 40-180 mm, preferably 50 to 150 mm and a width of 800-2500 mm.

[0016] A key aspect of the invention is the machine protection of the shears by a preferably continuous calculation of the hot shear strength of the metal strip at the cutting point. If the shear strength of the metal strip at a target cutting time at the cutting point is greater than a defined limit shear strength, the cutting action of the shears is blocked according to the invention, preferably until the shear strength of the metal strip is less than or equal to a limit shear strength specified for the shears.

[0017] The process can be carried out using models and rules. Unlike methods known in the prior art, the temperature profile before the metal strip is cut is not influenced; instead, the shear strength of the metal strip is continuously calculated, where the shear strength is a function of the temperature, the material composition of the metal strip, its thickness, and its width.

[0018] The method according to the invention provides for setting a new target cutting time if the cutting is blocked due to exceeding the limit shear strength of the metal strip.

[0019] The shear strength of the metal strip at the cutting point at the target cutting time can be determined as a function of the temperature of the metal strip at the cutting point at the target cutting time.

[0020] For this purpose, it may be possible to continuously determine the temperature at the cutting point at the target cutting time based on a measured temperature and / or a calculated temperature profile over at least a partial length of the metal strip.

[0021] According to the invention, the target cutting time is calculated using at least one computer-implemented algorithm for cutting length optimization, which is, for example, part of a higher-level process control system.

[0022] The shear strength of the metal strip at the target cutting time and location is preferably determined as a function of the strip's temperature, thickness and / or width, and material composition. An online process model can calculate the temperature profile of the metal strip. In a CSP® system, for example, the online process model can calculate the temperature profile from a casting machine to the point where the strip enters a downstream furnace or heating unit. The material composition can be derived from the analysis of the rolled material and stored in the process control or automation system.

[0023] Shear strength is understood to be the shear strength of the metal strip in kN / mm 2< especially at elevated temperature, where shear strength is understood to be the resistance that a solid body offers, especially to tangential shear forces.

[0024] If unfavorable process conditions lead to high hot shear strength in the metal strip, the automation can lock the shear in critical areas of the rolling process or any upstream process step to prevent damage. These critical areas can also be visualized in Level 1 or Level 2 automation, which can issue corresponding warnings to the operator. Using a model-based calculation for cutting length optimization, the originally planned target cut can be repositioned to minimize process disruption.

[0025] According to one aspect of the invention, a rolling mill is provided which includes means for cutting to length and rolling a metal strip in at least one rolling line with at least one rolling device, wherein at least one shear is preferably arranged directly behind a continuous casting plant, wherein the shear is designed to cut the metal strip into sections of predetermined length, wherein the rolling mill includes a higher-level process control for automation, wherein the process control includes means for controlling the at least one shear according to the method described above.

[0026] The shear can be located directly behind a continuous casting plant and in front of one of the furnaces upstream of at least one rolling mill. The furnace can, for example, be a tunnel furnace.

[0027] The rolling mill according to the invention can in particular have a process control system which includes means for calculating a temperature profile and / or a temperature distribution of the metal strip between the continuous casting plant and a heating device which is located upstream of a first rolling mill.

[0028] The process control includes means for at least approximately determining the shear strength of the metal strip as a function of the temperature, the thickness and / or width of the metal strip and / or its material composition at an entry point of the metal strip into a cutting area of ​​the shears, as well as means for blocking the shears if a shear-specific limit shear strength of the metal strip is exceeded.

[0029] Furthermore, the process control includes a device for optimizing the cutting length of the metal strip, which is designed to determine a modified target cutting time for the shears if a cutting trigger is blocked. The cutting length optimization is preferably model-based. The model can be based on machine learning methods, in particular artificial neural networks and the like.

[0030] The invention is explained below with reference to an embodiment shown in the drawings.

[0031] They show: Figure 1 shows a casting and rolling mill according to the invention, and Figure 2 shows a hot rolling mill according to the invention.

[0032] In Figure 1Figure 1 schematically shows a part of a rolling mill according to the invention, which is designed as a casting and rolling mill 1. The casting and rolling mill 1 comprises a continuous casting plant 2, a shear in the form of a pendulum shear 3 arranged downstream of the continuous casting plant 2, a heating device in the form of a tunnel furnace 4 arranged downstream of the pendulum shear 3, and rolling stands (not shown) arranged in at least one rolling line.

[0033] The continuous casting plant 2 comprises a ladle (not shown) and a mold 5. The casting strand 6 exiting the mold 5 is deflected via a strand guide 7 and cut into slabs downstream of the strand guide 7 by the pendulum shear 3 upstream of the tunnel furnace 4. The slabs, or the casting strand 6, can have a thickness of 40–180 mm and a width of 800–2500 mm upstream of the pendulum shear 3. The mean temperature of the casting strand 6 at the inlet to the pendulum shear 3 should be approximately 1000 °C, i.e., approximately 900 °C on the outside and approximately 1200 °C in the core. The casting strand 6 is preferably fed to the pendulum shear 3 at a velocity of 2–7 m / s. The pendulum shear 3 is controlled by a control and regulating device 8, which triggers a cut at a target cutting time depending on a target length of the slabs.

[0034] The method according to the invention comprises a continuous calculation of the shear strength of the casting strand 6 or the metal strip to be separated as a function of the temperature of the casting strand, the material composition of the casting strand, and the thickness and width of the casting strand.

[0035] The shear strength, or hot shear strength, of the casting strand 6 is crucial for determining the shear or cutting force that the pendulum shear 3 must apply parallel to the cutting surface. In particular, if the temperature of the casting strand 6 falls below a certain level at the inlet to the pendulum shear 3, this can result in increased hot shear strength. The pendulum shear 3 is designed for a specific shear or cutting force, so it can be assumed that if a limit shear strength of the casting strand 6 is exceeded, the pendulum shear 3 will be damaged or subject to increased wear. The method according to the invention provides for the continuous calculation of the shear strength of the casting strand 6 based on a temperature profile of the casting strand 6 up to the inlet of the tunnel furnace 4. The method includes determining a target cutting time for the pendulum shear 3 as a function of a predetermined target length of the casting strand 6.The target length of the metal strip or slab to be cut is specified by a process control unit 9. Furthermore, the control unit 8 receives a control impulse from the monitoring of the hot shear strength of the casting strand 6. This impulse is derived from a comparison of the shear strength of the casting strand 6 with the specified limit shear strength. If the shear strength of the casting strand 6 in the area of ​​the pendulum shear 3's entry point is greater than the limit shear strength at a given time, the pendulum shear 3 is locked or blocked. Based on a model for optimizing the cutting length, the process control unit 9 instructs the control unit 8 to position a new slab cut.

[0036] In Figure 2Figure 10 schematically depicts a part of a hot rolling mill 10 according to a second embodiment of the invention. A continuous casting plant 2 does not necessarily have to be connected upstream of this hot rolling mill 10. Identical components are designated with the same reference numerals in this embodiment. The hot rolling mill 10, to which a hot strip 12 is fed continuously or discontinuously, comprises several heating devices, namely an induction heating device 13 and two tunnel furnaces 4, two rolling mills with rolling stands 11, and several shears 14 designed for different strip thicknesses. For the sake of simplicity, the illustration and listing of other known components are omitted. The number of shears in the rolling mill can vary, as can their position within the plant.

[0037] The hot strip 12 is fed to one of the drum shears 14. The drum shears 14 are each controlled by a control and regulating device 8, which triggers a cut at a target cutting time depending on a target length of the strip.

[0038] The method according to the invention comprises a continuous calculation of the shear strength of the hot strip 12 or the cast strand 6 to be separated (see Figure 1 ) as a function of the temperature of the material, the material composition, as well as the thickness and width of the hot strip 12 or the cast strand 6.

[0039] The shear strength, or hot shear strength, of the metal strip is crucial in determining the shearing or cutting force that the shears must apply parallel to the cutting surface. In particular, if the temperature of the hot strip 12 falls below a certain level at the point where it enters the shears, this can result in increased hot shear strength. The shears are each designed for a specific shearing or cutting force, so it can be assumed that if a limit shear strength of the hot strip 12 is exceeded, the shears in question will be damaged or subject to increased wear.

[0040] The method according to the invention provides for the continuous calculation of the shear strength of the hot-rolled strip 12 based on a temperature profile of the hot-rolled strip 12. This can be limited to a section of the hot-rolling mill 10 or applied to the entire hot-rolling mill 10. The method includes determining a target cutting time for the respective shear as a function of a predetermined target length of the hot-rolled strip 12. The target length of the hot-rolled strip 12 to be cut is specified by a process control 9. In addition, the control unit 8 receives a control pulse from the monitoring of the hot shear strength of the hot-rolled strip 12, which is derived from a comparison of the shear strength of the hot-rolled strip 12 with the predetermined limit shear strength. If the shear strength of the hot-rolled strip 12 in the entry area of ​​the respective shear is greater than the limit shear strength at the target cutting time, the shear is locked or...blocked. Based on a model for cutting length optimization, the process control 9 instructs the control and regulation unit 8 to place a new cut. Reference symbol list

[0041] 1 Casting mill 2 Continuous casting mill 3 Pendulum shear 4 Tunnel furnace 5 Mold 6 Casting strand 7 Strand guide 8 Control and regulating device 9 Process control 10 Hot rolling mill 11 Rolling stands 12 Hot strip 13 Induction heating device 14 Shears

Claims

1. Method of cutting a metal strip to length by means of at least one shears in a rolling plant (1) with use of at least one superordinate process control for automation of the rolling plant, wherein the method comprises the following method steps: A) determining at least one target cutting instant at a cut location of the rolling plant in dependence on a target length of the metal strip, B) determining the cutting resistance of the metal strip at the cut location at the target cutting instant, C) triggering a cut at the target cutting instant if the cutting resistance of the metal strip at the cut location at a target cutting instant is less than or equal to a limit cutting resistance, which is given for the shears, of the metal strip or D) blocking the cut at the target cutting instant if the cutting resistance of the metal strip at the target cutting instant at the cut location is greater than the limit cutting resistance, characterised in that the method comprises the following further step: E) fixing a new target cutting instant if the cut in accordance with method step D) was blocked, wherein the target cutting instant is calculated by means of at least one computer-implemented algorithm for cut length optimisation.

2. Method according to claim 1, characterised in that the cutting resistance of the metal strip at the cut location at the target cutting instant is determined in dependence on a temperature of the metal strip at the cut location at the target cutting instant.

3. Method according to one of claims 1 and 2, characterised in that the temperature at the cut location at the target cutting instant is determined continuously on the basis of a measured temperature and / or a calculated temperature plot over at least a sub-length of the metal strip.

4. Method according to any one of claims 1 to 3, characterised in that the cutting resistance of the metal strip at the target cutting instant at the cut location is determined in dependence on the temperature of the metal strip and the thickness thereof and / or the width thereof as well as in dependence on the material composition thereof.

5. Rolling plant (1) comprising means for cutting to length and rolling a metal strip in at least one rolling line with at least one rolling device (11), at least one shears arranged upstream and / or downstream of a rolling device (11) and configured for separating the metal strip into sections of predetermined length and at least one superordinate process control (9) for automation of the rolling plant, wherein the process control (9) comprises means for controlling the at least one shears in accordance with the method according to any one of claims 1 to 4 as well as means for at least approximate determination of the cutting resistance of the metal strip in dependence on the temperature, thickness and / or width of the metal strip and / or the material composition thereof at an entry of the metal strip into a cutting region of the shears as well as means for blocking the shears if a shears-specific limit cutting resistance of the metal strip is exceeded, and the process control (9) comprises a device for cut length optimisation of the metal strip, which is configured to determine a changed target cutting instant for the shears if triggering of a cut is blocked.

6. Rolling plant (1) according to claim 5, characterised in that the shears are arranged directly downstream of a continuous casting plant (2) and directly upstream of a heating device (4) upstream of at least one rolling device (11)7. Rolling plant (1) according to claim 6, characterised in that the process control (9) comprises means for calculation of a temperature profile and / or a temperature plot of the metal strip between the continuous casting plant (2) and the heating device (4) upstream of the at least one rolling device (11).

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