Method for estimating warpage shape of metal strip, method for determining qualification of metal strip, method for manufacturing metal strip, and device for estimating warpage shape of metal strip

Abstract

Provided are a method for estimating the warpage shape of a metal strip, a method for determining whether or not a metal strip is qualified, and a device for estimating the warpage shape of a metal strip, with which it is possible to estimate the warpage shape in the plate width direction caused by rapid cooling of a metal strip on the basis of the warpage shape in the plate width direction in a state in which tension is applied in the longitudinal direction. The warpage shape in the plate width direction in a state in which the tension is removed is estimated. A method for estimating the warpage shape of a metal strip, which estimates the warpage shape in the plate width direction of the metal strip in a tension-free state in which tension is removed from the shape in the plate width direction of the metal strip in a tension-applied state in which the tension in the longitudinal direction is applied, comprises: a plate width direction shape measurement step for measuring the shape in the plate width direction; measuring the shape distribution of the metal strip in the plate width direction in the tension applying state; an approximate curve calculation step for calculating an approximate curve obtained by approximating the shape distribution in the plate width direction measured in the plate width direction shape measurement step by a quadratic curve or an arc; and a warping shape estimation step in which the warping shape of the metal strip in the plate width direction in the tension-free state is estimated using the shape distribution in the plate width direction and the approximation curve.

Description

Technical Field

[0001] The present invention relates to a method for estimating the warping shape of a metal strip conveyed by a continuous annealing device or the like, a method for determining whether the metal strip is acceptable, a method for manufacturing the metal strip, and an apparatus for estimating the warping shape of the metal strip. Background Art

[0002] In continuous annealing equipment for treating metal strips, it is important to control heat treatment conditions such as heating and cooling in order to give the metal strips the desired mechanical properties. In particular, in the manufacture of high-strength steel sheets, from the viewpoint of improving stamping formability, the cooling rate of the heated metal strip is accelerated, and the metal strip after reheating and cooling is tempered.

[0003] The continuous annealing equipment is equipped with a heating zone, a soaking zone and a cooling zone. The cooling methods in the cooling zone include liquid quenching, roller cooling, water-gas mixing (mist) cooling, gas jet cooling, etc. The cooling method is appropriately selected in order to control the material of the metal strip. The liquid quenching method has the fastest cooling speed among these methods. The liquid quenching method can reduce the addition of alloy elements used to increase the strength of the metal strip, so it is suitable for the manufacture of high-strength steel plates. The liquid quenching method immerses the heated metal strip in liquid while spraying cooling liquid onto the metal strip from a slit nozzle set in the liquid for rapid cooling.

[0004] When the metal strip is rapidly cooled, the metal strip may have shape defects due to the influence of the volume expansion caused by the thermal contraction of the metal strip and the phase change of the metal structure. Regarding the shape defects caused by the rapid cooling of the metal strip, when tension is applied in the longitudinal direction for conveying the metal strip, the warping in the longitudinal direction is apparently suppressed by the tension. However, due to the potential residual stress (residual moment), the warping in the longitudinal direction is generated as warping in the plate width direction. In this case, the faster the cooling rate of the metal strip is in the plate width direction, the warping is not only formed in the shape of a quadratic curve or an arc, but also in the shape of a concave-convex shape that can be approximated by a W-shape or a high-order function.

[0005] In addition, in the quality inspection related to the shape of the metal strip, the tension applied by the metal strip is removed, and the pass or fail is determined based on the warpage amount measured by cutting the metal strip into a plate shape. However, in the continuous annealing equipment for manufacturing the metal strip, the warpage amount measured during the conveyance of the metal strip is not necessarily the same as the warpage amount measured after the tension applied by the metal strip is removed and the metal strip is cut into a plate shape. Therefore, in the continuous annealing equipment for manufacturing the metal strip, it is difficult to perform the quality inspection related to the warpage shape with high accuracy during the conveyance of the metal strip. Assuming that the conveyance of the metal strip is temporarily stopped in the continuous annealing equipment, the tension is removed, and the warpage amount is measured in the case of performing the quality inspection related to the warpage shape with high accuracy, the production efficiency is reduced. Alternatively, it is necessary to perform the quality inspection of the metal strip after conveying the metal strip to an inspection production line different from the continuous annealing equipment, resulting in an additional process for quality inspection, resulting in a reduction in production efficiency and an increase in cost.

[0006] In this regard, Patent Document 1 discloses a flatness control device for controlling the temperature of a metal strip in the width direction of the sheet in a cooling section of a continuous annealing device in order to improve the flatness of the metal strip in a tension-free state. Patent Document 1 discloses a method of comparing the shape of the metal strip in the width direction in a state where tension is applied to the metal strip with the shape of the metal strip in the width direction in a state where the tension is removed, and controlling the temperature of the metal strip in the width direction based on the comparison result.

[0007] Patent Document 2 discloses a method for estimating residual bending moments generated in the length direction and the width direction of a metal strip using the warpage in the sheet width direction of a metal strip under a tension applied thereto and the applied tension. Patent Document 2 further discloses a method for calculating the warpage in the length direction and the warpage in the sheet width direction of a cut sheet under a tension-free state by using a relational expression representing elastic deformation using the estimated residual bending moment.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2-66125

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 6-102036 Summary of the invention

[0012] Problems to be solved by the invention

[0013] However, in the flatness control device for a metal strip described in Patent Document 1, it is necessary to collect actual data on both the shape of the metal strip in the width direction when tension is applied to the metal strip and the shape of the metal strip in the width direction when tension is removed. In this case, in order to collect actual data corresponding to the thickness, width, steel grade, etc. of the metal strip, it is necessary to repeatedly stop the production line and remove tension during the manufacture of the continuous annealing equipment, resulting in a decrease in the production efficiency of the continuous annealing equipment. In addition, as described in Patent Document 1, Figure 2 As shown in FIG. 1 , the shape of the metal strip described in Patent Document 1 refers to the steepness represented by the ratio of the displacement distance in the vertical direction to the displacement width in the longitudinal direction. That is, the shape of the metal strip in Patent Document 1 refers to the wave shape such as the side wave and the middle wave generated in the metal strip. Therefore, the shape of the metal strip in Patent Document 1 is different from the warping shape in the plate width direction which is the inspection object of the quality inspection of the metal strip. Therefore, it is difficult to apply the structure described in Patent Document 1 to the warping shape in the plate width direction of the metal strip.

[0014] In addition, the method described in Patent Document 2 is a method of using a relational expression representing elastic deformation to calculate the warping amount in the length direction and the warping amount in the plate width direction of the metal strip in a state where tension is removed based on the estimated residual bending moment. The relational expression representing elastic deformation can be expressed by a high-order function such as a fourth-order function or a sixth-order function relative to the coordinates within the plane of the metal strip. However, in Patent Document 2, it is assumed that the residual bending moment of the metal strip is generated uniformly (evenly) within the plane of the metal strip, and therefore it cannot be applied to the case where the residual bending moment is unevenly distributed. That is, the method described in Patent Document 2 cannot be applied to the case where uneven residual stress is generated within the plane due to rapid cooling of the metal strip, forming an uneven warping shape. Assuming that the method is applied to a metal strip having an uneven warping shape, there is a problem of reduced accuracy in estimating the warping shape.

[0015] The present invention has been completed in view of the above situation, and its purpose is to provide a method for estimating the warping shape of a metal strip, a method for judging the quality of a metal strip, a method for manufacturing a metal strip, and a device for estimating the warping shape of a metal strip, which can estimate the warping shape in the width direction of the plate caused by rapid cooling of the metal strip based on the warping shape in the width direction of the plate under a state in which tension is applied in the length direction, and estimate the warping shape in the width direction of the plate under a state in which tension is removed.

[0016] Means for solving problems

[0017] The gist of the present invention for solving the above-mentioned problems is as follows.

[0018] [1] A method for estimating the warping shape of a metal strip, which estimates the warping shape of the metal strip in the plate width direction in a tension-free state after the tension is removed, based on the shape of the metal strip in the plate width direction in a tension-applied state in which tension in the length direction is applied, wherein the method for estimating the warping shape of the metal strip comprises: a plate width direction shape measurement step, in which the plate width direction shape distribution of the metal strip is measured in the tension-applied state; an approximate curve calculation step, in which an approximate curve is calculated by approximating the plate width direction shape distribution measured in the plate width direction shape measurement step using a quadratic curve or a circular arc; and a warping shape estimation step, in which the plate width direction shape distribution and the approximate curve are used to estimate the warping shape of the metal strip in the tension-free state.

[0019] [2] The warpage shape estimation method of a metal strip according to [1], wherein, in the plate width direction shape measurement step, the plate width direction shape distribution of the metal strip is measured by a distance measurement method or a light section method.

[0020] [3] The warpage shape estimating method of a metal strip according to [1] or [2], wherein the plate width direction shape measuring step is performed after the metal strip is cooled by a cooling section of a continuous annealing device and before it is wound on a coiler of the continuous annealing device.

[0021] [4] A method for determining whether a metal strip is acceptable or not, wherein the determination of whether the metal strip is acceptable or not is performed based on the warping shape of the metal strip in the tension-free state estimated by the warping shape estimation method for the metal strip described in any one of [1] to [3].

[0022] [5] A method for manufacturing a metal strip, wherein the metal strip is judged to be acceptable by using the method for judging the acceptability of the metal strip described in [4], and the metal strip judged to be acceptable is manufactured.

[0023] [6] A device for estimating the warping shape of a metal strip, which estimates the warping shape of the metal strip in the plate width direction in a tension-free state after the tension is removed, based on the shape of the metal strip in the plate width direction in a tension-applied state in which a tension in the length direction is applied, wherein the device for estimating the warping shape of the metal strip has: a plate width direction shape measuring device, which measures the plate width direction shape distribution of the metal strip in the tension-applied state; and a metal strip warping shape estimating device, which estimates the warping shape of the metal strip in the plate width direction in the tension-free state, wherein the metal strip warping shape estimating device has: an acquisition unit, which acquires the plate width direction shape distribution of the metal strip from the plate width direction shape measuring device; an approximate curve calculation unit, which calculates an approximate curve obtained by approximating the plate width direction shape distribution measured in the plate width direction shape measuring device using a quadratic curve or a circular arc; and a warping shape estimation unit, which uses the plate width direction shape distribution and the approximate curve to estimate the warping shape of the metal strip in the plate width direction in the tension-free state.

[0024] [7] The warpage shape estimation device of the metal strip according to [6], wherein the plate width direction shape measurement device measures the plate width direction shape distribution of the metal strip by a distance measurement method or a light section method.

[0025] [8] The warping shape estimation device for a metal strip according to [6] or [7], wherein the plate width direction shape measuring device is arranged between a cooling section and a coiler of a continuous annealing device that performs heat treatment on the metal strip.

[0026] Effects of the Invention

[0027] According to the present invention, the warping shape in the sheet width direction caused by rapid cooling of the metal strip can be estimated from the warping shape in the sheet width direction in a state where tension is applied in the longitudinal direction, without tension. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [ Figure 1 ] Figure 1 It is a schematic side view showing an example of a continuous annealing facility.

[0029] [ Figure 2 ] Figure 2 It is a side schematic diagram showing an example of a cooling unit.

[0030] [ Figure 3 ] Figure 3 This is a simplified functional block diagram of a warpage shape estimation device.

[0031] [ Figure 4 ] Figure 4 This is a diagram simply showing a state where a metal strip is measured using a laser rangefinder.

[0032] [ Figure 5 ] Figure 5 This is a diagram simply showing a state where a metal strip is measured by a plurality of laser distance meters.

[0033] [ Figure 6 ] Figure 6 This is a diagram showing an example of the warping shape in the plate width direction of a metal strip measured by a plate width direction shape measuring device.

[0034] [ Figure 7 ] Figure 7 This is a diagram schematically showing the strain generated on the inner surface of the metal strip when the metal strip is bent in the longitudinal direction.

[0035] [ Figure 8 ] Figure 8 This is a diagram showing an example of an approximate curve calculated by the approximate curve calculation unit.

[0036] [ Fig. 9 ] Fig. 9 This is a diagram showing another example of the approximate curve calculated by the approximate curve calculation unit.

[0037] [ Fig.10 ] Fig.10 This is a diagram showing an example of a warpage shape in a tension-free state estimated using a shape distribution in the sheet width direction in a tension-applied state and an approximate curve.

[0038] [ Fig.11 ] Fig.11 This is a diagram showing an example of comparison between an estimated warp shape and an actually measured value of the warp shape in a tension-free state.

[0039] [ Fig.12 ] Fig.12 This is a diagram showing another example of the warpage shape in the tension-free state estimated using the shape distribution in the sheet width direction in the tension-applied state and the approximate curve.

[0040] [ Fig.13 ] Fig.13 This is a diagram showing another example of comparison between the estimated warp shape and the actually measured value of the warp shape in a tension-free state. DETAILED DESCRIPTION

[0041] Hereinafter, the present invention will be described by taking a continuous annealing device for a metal strip as a processing object as an example through the embodiments of the present invention. Here, each of the drawings is schematic and sometimes different from the actual objects. In addition, the following embodiments illustrate the device and method for implementing the technical idea of ​​the present invention, and do not specify the following contents. That is, the technical idea of ​​the present invention can be subjected to various changes within the technical scope described in the claims.

[0042] The continuous annealing equipment is a device for heat treating a metal plate that has been thickened to a specified plate thickness by a hot rolling process, a pickling process, and a cold rolling process. After the hot rolling process, the metal plate is wound into a coil shape and then heat treated, etc., so in this embodiment, the metal plate is recorded as a "metal strip". The continuous annealing equipment is mainly used for the heat treatment of steel plates, so the metal strip mainly refers to the steel strip. When the steel strip is cooled, it is easy to form a warp in a concave and convex shape that can be approximated by a W-shaped or high-order function in the plate width direction. In particular, since it is easy to form a warp in a concave and convex shape in a high-strength steel plate, it is preferred to use a high-strength steel plate with a tensile strength of more than 980MPa as the object. Regarding the metal strip, it is preferred that the plate thickness is 0.4~3.2mm, the plate width is 700~1800mm, and the length is 600~4000m.

[0043] Reference Figure 1 , the structure of the continuous annealing equipment 100 is described. Figure 1 1 is a schematic side view of the continuous annealing device 100. Figure 1 In the embodiment, the metal strip 1 is transported in a transport direction A.

[0044] The continuous annealing equipment has an input side device 20, a furnace body device 21 and an output side device 24. The input side device 20 has an unwinder 2, a welding machine 3 and an input side looper 4. The furnace body device 21 has an annealing device 22 and a reheating device 23. The annealing device 22 has a preheating zone 5, a heating zone 6, a soaking zone 7 and a cooling zone 8. The setting of the preheating zone 5 can be arbitrarily performed. The reheating device 23 has a reheating zone 9, an over-aging zone 10 and a final cooling zone 11. The reheating zone 9 has an induction heating device. The output side device 24 has an output side looper 12, a shape correction device 13, an inspection table 14 and a coiler 15.

[0045] The annealing process of the metal strip 1 performed by the continuous annealing equipment 100 is a process of heating the metal strip 1 from a temperature near room temperature, maintaining it at a predetermined temperature, and then lowering the temperature to near room temperature. The continuous annealing equipment 100 performs the annealing process using at least the heating zone 6, the soaking zone 7, and the cooling zone 8. The reheating process is a process of over-aging the metal strip 1 that has passed through the cooling zone 8. The continuous annealing equipment 100 performs the reheating process in the reheating zone 9, the over-aging zone 10, and the final cooling zone 11.

[0046] The heating zone 6 has a device for increasing the temperature of the metal strip 1. The metal strip 1 is heated to a preset temperature in the range of 600 to 900° C. in the heating zone 6 according to the composition of the metal strip 1. The heating zone 6 has a direct fire or radiation burner. The soaking zone 7 is a device for maintaining the metal strip 1 at a predetermined temperature.

[0047] The metal strip 1 is cooled to a predetermined temperature in the cooling zone 8. As a cooling method, the cooling zone 8 implements liquid cooling, gas jet cooling, roll cooling, spray cooling (gas-liquid mixed cooling), etc. In this embodiment, Figure 1 As shown, liquid cooling is performed. Liquid cooling cools the metal strip 1 by cooling with water (water quenching). Liquid cooling cools the metal strip 1 by immersing it in an immersion water tank. Gas jet cooling cools the metal strip 1 by blowing gas from a nozzle onto the surface of the metal strip 1. Roll cooling cools the metal strip 1 by bringing it into contact with a water-cooled roll. Spray cooling cools the metal strip 1 by spraying water into a fine mist and absorbing its heat of vaporization. Spray cooling makes the size of the sprayed water droplets 0.1 to 1 mm.

[0048] The reheating device 23 is arranged on the downstream side of the cooling zone 8. The reheating device 23 has an induction heating device that heats the metal strip 1 in the reheating zone 9. The reheating device 23 uses the induction heating device to reheat the metal strip 1 cooled to a specified temperature in the cooling zone 8 to a temperature of 300 to 400°C. The overaging zone 10 is a device for performing an overaging treatment by holding the reheated metal strip 1 for a specified time. The final cooling zone 11 is a device for finally cooling the metal strip 1 that has undergone the overaging treatment to a temperature near room temperature. In the continuous annealing equipment, the setting of the reheating device 23 is arbitrary.

[0049] The output side looper 12 is a device for temporarily storing the metal strip 1 in order to adjust the conveying speed of the metal strip 1 in the furnace body device 21 and the processing speed in the output side device 24. The shape correction device 13 is a device for flattening the shape of the metal strip 1. The shape correction device 13 has one or both of a skin-pass rolling mill and a tension leveler. The inspection station 14 is a device for performing quality inspection on the metal strip 1. The inspection station 14 performs quality inspections on the size, shape (flatness, warpage shape), surface quality, etc. of the metal strip 1. The quality inspection of the metal strip 1 is performed while the metal strip 1 is being conveyed, but it can also be performed in a state where the inspector slows down the conveying speed of the metal strip 1 as needed. In addition, in the past, when inspecting the shape of the metal strip 1, the conveying in the inspection station 14 was temporarily stopped, and the tension applied to the metal strip 1 was removed before performing the quality inspection. The coiler 15 is a device for winding the metal strip 1 into a coil. The metal strip wound into a coil is sometimes shipped as a product coil. The coiled metal strip is sometimes sent to a recoiling line to adjust the size and weight of the metal strip, collect samples for quality inspection, inspect the shape and size, and rewind it as a coil. In addition, the coiled metal strip is sometimes sent to a surface treatment facility for plating to perform surface treatment.

[0050] The quality inspection related to the shape of the metal strip 1 in the inspection station 14 is accompanied by temporarily stopping the conveyance of the metal strip 1 to remove the tension applied to the metal strip 1, so there is a problem of reduced production efficiency of the continuous annealing equipment. Therefore, there is also a case where the conveyance of the metal strip 1 is not stopped in the continuous annealing equipment, but the metal strip 1 is formed into a coil by the winder 15 and then sent to the rewinding line, and the quality inspection related to the shape of the metal strip is performed in the rewinding line. However, in this case, since the manufacturing process of the metal strip is added, there is a problem of increased production cost.

[0051] In contrast, in the present embodiment, the continuous annealing equipment 100 can estimate the warping shape in the sheet width direction in a state where the tension is removed (hereinafter, also referred to as a "tension-free state") for the metal strip 1 conveyed in a state where the tension is applied in the longitudinal direction (hereinafter, also referred to as a "tension-applied state"). Therefore, it is not necessary to stop the conveyance of the metal strip 1, nor is it necessary to perform a quality inspection related to the shape of the metal strip conveyed in a coiled state by a rewinding line.

[0052] The cooling zone 8 has a cooling part 40 for cooling the metal strip 1 to a predetermined temperature by liquid cooling. The cooling of the metal strip 1 preferably adopts a cooling method of liquid cooling. Liquid cooling is performed by immersing the metal strip 1 in an immersion water tank, and the metal strip 1 can be rapidly cooled. Liquid cooling can adjust the cooling speed of the metal strip 1 by changing the conveying speed of the metal strip 1. Therefore, liquid cooling can reduce the addition of alloy elements for improving the strength of the metal strip 1 by adjusting the cooling speed of the metal strip 1, and is suitable for the manufacture of high-strength steel sheets.

[0053] The cooling unit 40 cools the metal strip 1 heated to a temperature higher than the recrystallization temperature or the austenite transformation start temperature (AC3) in the heating zone 6. The cooling unit 40 cools the metal strip 1 heated in the heating zone 6 to a temperature lower than the martensite transformation start temperature (Ms) or the bainite transformation start temperature (Bf).

[0054] Here, use Figure 2 The cooling method and cooling structure in the cooling unit 40 will be described. Figure 2 The schematic side view of the cooling unit 40 is shown. The cooling unit 40 includes a water cooling nozzle unit 41, an immersion water tank 43, a press roll 45, deflector rolls 46 and 47, a dewatering roll 48, and a drying oven 49. In the cooling unit 40, the press roll 45 is arbitrarily provided.

[0055] The water cooling nozzle unit 41 has a water spray nozzle. The pressing roller 45 prevents the metal strip 1 from shaking (wobbling). The dehydrating roller 48 removes water attached to the metal strip 1 passing through the immersion water tank 43. The drying furnace 49 dries the metal strip 1 from which the water has been removed by the dehydrating roller 48. After being dried by the drying furnace 49, the metal strip 1 is conveyed to the reheating zone 9.

[0056] The immersion water tank 43 is formed in a container shape so as to store cooling water 44 for immersing and cooling the metal strip 1. The immersion water tank 43 may have a cooling machine (cooling water circulation device) that circulates the cooling water 44 to maintain the temperature in order to suppress the temperature rise of the stored cooling water 44 and control the temperature of the cooling water 44 within a predetermined range.

[0057] The water cooling nozzle unit 41 sprays cooling water onto the metal strip 1 to cool it. In order to spray cooling water onto the surface and back of the conveyed metal strip 1, the water cooling nozzle unit 41 provides a pair of water spray nozzles on the surface and back of the metal strip 1 in multiple stages along the conveying direction A of the metal strip 1. The water cooling nozzle unit 41 can spray cooling water onto the surface and back of the metal strip 1 using multiple stages of water spray nozzles to cool the metal strip 1 passing through the heat soaking zone 7.

[0058] Next, use Figure 3 The warp shape estimation device 30 that estimates the warp shape of the metal strip 1 will be described. Figure 3 A simplified functional block diagram of the warpage shape estimation device 30 is shown. The warpage shape estimation device 30 includes a plate width direction shape measurement device 31 and a warpage shape estimation device 32. The warpage shape estimation device 32 is a general-purpose computer such as a workstation or a personal computer, and includes an acquisition unit 33, an approximate curve calculation unit 34, and a warpage shape estimation unit 35. The plate width direction shape measurement device 31 measures the shape distribution in the plate width direction of the metal strip 1 (hereinafter also referred to as "plate width direction shape distribution") in a tensioned state of the metal strip 1. The acquisition unit 33 acquires the plate width direction shape distribution of the metal strip 1 from the plate width direction shape measurement device 31. The approximate curve calculation unit 34 uses the plate width direction shape distribution acquired by the acquisition unit 33 to calculate an approximate curve obtained by approximating the shape distribution with a quadratic curve or a circular arc. The warpage shape estimation unit 35 estimates the warpage shape in the plate width direction of the metal strip 1 in a tension-free state using the plate width direction shape distribution acquired by the acquisition unit 33 and the approximate curve calculated by the approximate curve calculation unit 34. The output unit 36 ​​may also output the estimated result of the warping shape in the plate width direction of the metal strip 1 in the tension-free state estimated by the warping shape estimating device 32. The output unit 36 ​​may be, for example, a display screen such as a liquid crystal. By displaying the estimated result of the warping shape in the plate width direction in the tension-free state of the metal strip 1 on the output unit 36, an inspector who performs a quality inspection of the metal strip 1 can determine whether the warping shape of the metal strip 1 is acceptable.

[0059] In addition, by using the warpage shape estimation device 30, the warpage shape estimation method of the metal strip of the present invention can be implemented. Specifically, the plate width direction shape measurement device 31 performs a plate width direction shape measurement step of measuring the plate width direction shape distribution of the metal strip 1 under a tension state. The approximate curve calculation unit 34 performs an approximate curve calculation step in which an approximate curve obtained by approximating the plate width direction shape distribution measured in the plate width direction shape measurement step by a quadratic curve or an arc is calculated. The warpage shape estimation unit 35 performs a warpage shape estimation step of estimating the warpage shape in the plate width direction of the metal strip 1 in a tension-free state using the plate width direction shape distribution and the approximate curve.

[0060] The plate width direction shape measuring device 31 can be arranged at any position of the conveying path of the metal strip 1 in the continuous annealing equipment 100. The plate width direction shape measuring device 31 is preferably arranged in the conveying path downstream of the cooling section 40 of the cooling zone 8. This is because the metal strip 1 cooled by the cooling section 40 undergoes volume expansion accompanied by thermal contraction and phase change, and becomes a complex shape with non-uniform shape distribution in the plate width direction. In addition, when the output side device 24 of the continuous annealing equipment 100 is equipped with a shape correction device 13, the plate width direction shape measuring device 31 is more preferably arranged in the conveying path downstream of the shape correction device 13. This is because, although the non-uniform shape in the plate width direction generated in the metal strip 1 by passing through the cooling section 40 is reduced to some extent by passing through the shape correction device 13, even after being conveyed to the downstream side of the shape correction device 13, a lot of non-uniform shape distribution will remain. Moreover, the plate width direction shape measuring device 31 is preferably arranged at the inspection table 14 of the continuous annealing equipment 100. This is because, by estimating the warping shape in the tension-free state using the plate width direction shape measuring device 31 together with the inspection of the size and surface quality of the metal strip 1, it is possible to omit the determination of the shape quality of the warping shape in the rewinding line. In addition, the metal strip 1 passing through the conveying path provided with the plate width direction shape measuring device 31 is preferably conveyed in a state where a tension of 10 MPa to 100 MPa is applied in the longitudinal direction.

[0061] As long as the plate width direction shape measuring device 31 can measure the plate width direction shape distribution of the metal strip 1, various measuring devices can be applied. The plate width direction shape measuring device 31 can apply a distance measurement method, which uses a laser rangefinder to measure the distance between each position in the plate width direction of the metal strip 1 and the measuring device, and determines the plate width direction shape distribution based on the measured distance. In the distance measurement method, in addition to a laser rangefinder that uses a straight laser to measure the distance, a laser scanning rangefinder that scans the laser in a fan shape to measure the distance between each position in the plate width direction of the metal strip 1 can also be used. In the case of using a straight laser rangefinder, the plate width direction shape measuring device 31 is configured with multiple laser rangefinders relative to the plate width direction of the metal strip 1 to measure the warping shape at each position. In this case, the number of laser rangefinders configured along the plate width direction of the metal strip 1 is preferably set to a number of more than 3 and less than 100. More preferably, it is 10 to 20. Furthermore, when the number of laser rangefinders arranged in the plate width direction of the metal strip 1 is less than 3, it is difficult to accurately determine the shape distribution in the plate width direction of the metal strip 1. In addition, this is because even if the number of laser rangefinders arranged in the plate width direction of the metal strip 1 exceeds 100, the measurement accuracy of the shape distribution in the plate width direction does not change.

[0062] Regarding the plate width direction shape measuring device 31, use Figure 4 The state when using a laser scanning rangefinder is described. Figure 4 The following simply shows a state where the shape distribution in the sheet width direction of the metal strip 1 is measured using a laser scanning distance meter. By using a laser scanning distance meter, the shape distribution in the sheet width direction of the metal strip 1 can be measured using a single measuring device.

[0063] Next, use Figure 5 A description will be given of a case where a plurality of laser scanning distance meters are used as the plate width direction shape measuring device 31 . Figure 5 The state of the metal strip 1 is simply shown by measuring multiple laser scanning distance meters. Figure 5 As shown, the plate width direction shape measuring device 31 can also arrange multiple laser scanning distance meters in parallel along the plate width direction of the metal strip 1, and measure the warping shape of each position in the plate width direction in each zone of the metal strip 1 in the plate width direction.

[0064] The plate width direction shape measuring device 31 can also measure the warpage shape at each position in the plate width direction of the metal strip 1 by the light section method. The plate width direction shape measuring device 31 can use, for example, the LJ-X8000 series manufactured by KEYENCE or the Gocator manufactured by LMT Technologies to perform the warpage shape measurement based on the light section method. Here, the light section method is a method in which a laser beam that spreads in a fan shape toward the plate width direction of the metal strip 1 is irradiated, and reflected light from the metal strip 1 is captured by an image sensor, and the captured image is processed to thereby measure the displacement at each position on the surface of the metal strip 1.

[0065] The measurement accuracy of the warp shape of the plate width direction shape measuring device 31 is preferably 1 mm or less, more preferably 0.5 mm or less. In the continuous annealing equipment 100, the upper limit of the variation range of the warp shape of the manufactured metal strip 1 is set to 5 mm to 10 mm, so as to reliably perform quality assurance related to the warp shape of the metal strip 1.

[0066] The plate width direction shape measuring device 31 preferably measures (collects) the warping shape of the metal strip 1 in the plate width direction at intervals of less than 1 m along the length direction of the metal strip 1. The plate width direction shape measuring device 31 preferably has a measurement frequency of 10 Hz or more, and more preferably 20 Hz or more, for a continuously conveyed metal strip. This is because, in the output side device 24 of the continuous annealing device 100, the metal strip 1 is conveyed at a speed of more than 600 m / min, and can be measured (collected) at intervals of less than 1 m in the length direction of the metal strip 1. The plate width direction shape measuring device 31 can use the warping shape averaged in the range of 1 to 5 m in the length direction of the metal strip 1 as the measured value of the warping shape.

[0067] Next, use Figure 6 An example of the warping shape of the metal strip 1 measured by the strip width direction shape measuring device 31 will be described. Figure 6 It is a diagram showing an example of the warping shape in the plate width direction of the metal strip 1 measured by the plate width direction shape measuring device 31 .

[0068] Figure 6 The warping shape shown in FIG. 1 is a warping shape in the plate width direction obtained by measuring the high-strength steel plate by the plate width direction shape measuring device 31 after the high-strength steel plate is rapidly cooled by water quenching. When the high-strength steel plate having a tensile strength of 980 MPa or more is rapidly cooled by water quenching, as shown in FIG. Figure 6 As shown, the cross section of the metal strip 1 in the plate width direction is a W-shaped or concave-convex warp shape that can be approximated by a high-order function. Figure 6The warping shape shown is an example of the measurement of a high-strength steel plate with a thickness of 1.2 mm and a width of 1200 mm after the cooling process and the surface temper rolling process are completed. Figure 6 The warp shape shown represents the average value of the shape distribution measured at 20 locations at 100 mm intervals in the length direction of the metal strip 1. However, Figure 6 The warping shape shown is normalized by the difference (amplitude) between the maximum height and the minimum height in the board width direction.

[0069] In this embodiment, if Figure 6 As shown, the object is a metal strip 1 whose shape distribution in the sheet width direction under tension can be approximated by a curve of a W-shaped or a third-order or higher-order function (hereinafter also referred to as a "third-order approximation curve"). In other words, the object is to estimate the warping shape in the sheet width direction of the metal strip 1 in the tension-free state, which has a non-uniform residual stress (residual moment) in the plane due to rapid cooling of the metal strip 1 and has a non-uniform warping shape.

[0070] The approximate curve calculation unit 34 calculates an approximate curve obtained by approximating the shape distribution in the sheet width direction measured by the sheet width direction shape measuring device 31 and acquired by the acquisition unit 33 by a quadratic curve or an arc. The approximate curve approximated by the quadratic curve or the arc (hereinafter also referred to as a "quadratic arc approximate curve") is a curve symmetrical in the sheet width direction with the center portion in the sheet width direction of the metal strip 1 as the center, and is a curve having no inflection point in the sheet width direction. Here, the metal strip 1 generates a length warp (L warp) in the length direction of the metal strip 1 and a width warp (C warp) in the sheet width direction of the metal strip 1 in a tension-free state due to various residual stresses generated on the inner surface of the metal strip 1. The length warp of the metal strip 1 includes a warp shape that is in the shape of a quadratic arc approximation curve caused by uniform residual stress generated along the length direction. The width warp of the metal strip 1 includes a warp shape that is in the shape of a cubic approximation curve caused by non-uniform residual stress. In addition, the metal strip 1 conveyed by the continuous annealing equipment 100 is always conveyed in a state where tension is applied in the length direction (tension applied state) during conveyance. Therefore, the metal strip 1 being conveyed is conveyed in a manner that apparently has no length warpage in the length direction, but the influence of the residual stress that generates the length warpage (the shape of the quadratic arc approximation curve) does not disappear, but is converted into the width warpage in the plate width direction of the metal strip 1 and manifests itself. In other words, calculating the quadratic arc approximation curve for the plate width direction shape distribution measured by the plate width direction shape measuring device 31 helps to determine the influence of the length warpage of the metal strip 1.

[0071] Next, use Figure 7 The following describes strain generated on the inner surface of the metal strip 1 when the metal strip 1 is bent in the longitudinal direction. Figure 7 Schematically shows the strain generated on the inner surface of the metal strip 1 when the metal strip 1 is bent in the longitudinal direction. Figure 7 In the drawings, the upper surface of the metal strip 1 is referred to as the “upper surface”, and the lower surface of the metal strip 1 is referred to as the “lower surface”.

[0072] like Figure 7 As shown in FIG. 1 , when the metal strip 1 is bent in the longitudinal direction, an extension strain in the longitudinal direction is generated on the upper surface of the metal strip 1, and a compression strain in the longitudinal direction is generated on the lower surface. When extension strain and compression strain are generated in the longitudinal direction of the metal strip 1, strain is also generated in the width direction of the plate due to Poisson's ratio deformation. Figure 7 In the example shown, compressive strain is generated in the upper surface of the metal strip 1 in the plate width direction, and tensile strain is generated in the lower surface in the plate width direction. Therefore, in the plate width direction of the metal strip 1, the upper surface side contracts and the lower surface side extends, thereby generating warpage in the plate width direction. In the case where the metal strip 1 has length warpage in a tension-free state, the same Poisson's ratio deformation will occur even in a state where the length warpage is apparently eliminated when tension is applied. In addition, Figure 7 In the example shown, the bending strain in the length direction of the metal strip 1 is generated uniformly in the plate width direction, so the strain in the plate width direction accompanying the Poisson's ratio deformation is also generated uniformly along the plate width of the metal strip. That is, even in a state where the length warping is apparently eliminated by applying tension, a uniform strain in the plate width direction is generated along the plate width direction of the metal strip 1, so the length warping converted into the warping in the plate width direction has the shape of a quadratic arc approximation curve. As described above, the approximate curve calculation unit 34 of the present embodiment calculates an approximate curve obtained by approximating the plate width direction shape distribution measured by the plate width direction shape measurement device 31 with a quadratic curve or an arc, and determines the influence of the length warping converted into the warping in the plate width direction.

[0073] Here, the warping shape generated in the metal strip is specifically described together with the wave shape generated in the metal strip in the same manner. The shape defects of the metal strip are also manifested as wave-shaped shape defects called so-called side waves and intermediate corrugations. The wave shape is distributed in the plate width direction by the extension (strain) in the length direction of the metal strip, so that the stress in the plane generated in the length direction of the metal strip cannot be maintained in the plane of the metal strip, and it is displaced out of the plane due to buckling. The warping shape and the wave shape are the same in that the out-of-plane deformation occurs due to buckling. However, the direction of the residual stress that causes the buckling is different depending on whether it is in the plate width direction or the length direction. Therefore, the displacement of the shape of the surface of the wave shape in the length direction of the metal strip changes periodically, while the warping shape does not produce periodic displacement of the shape of the surface in the length direction of the metal strip. In addition, although the warping shape has the characteristic that the warping in the length direction and the warping in the plate width direction are converted into each other, the wave shape does not undergo such mutual conversion.

[0074] Next, use Figure 8 An example of the approximate curve calculated by the approximate curve calculation unit 34 will be described. Figure 8 is a diagram showing an example of an approximate curve calculated by the approximate curve calculation unit 34. However, Figure 8 The warping shape shown is normalized by the difference (amplitude) between the maximum height and the minimum height in the width direction of the plate under tension. Figure 9~Figure 13 The warping shape shown is also normalized by the difference (amplitude) between the maximum height and the minimum height in the sheet width direction under tension.

[0075] Figure 8 This is an example of using a quadratic curve to approximate the shape distribution in the plate width direction (warping shape) measured by the plate width direction shape measuring device 31 under a tension of 15 kN for a high-strength steel plate with a plate thickness of 1.0 mm and a plate width of 1220 mm. When a quadratic curve is used as the approximate curve, the relationship between the position x in the plate width direction and the warping shape y is expressed by the functional expression shown in the following equation (1) with a, b, and c as constants. Specifically, the error between the plate width direction shape distribution as a measured value and the warping shape y obtained by equation (1) is calculated in such a way as to determine the constant that becomes the minimum in the plate width direction.

[0076] [Mathematical formula 1]

[0077]

[0078] in addition, Fig. 9This is an example of using an arc to approximate the shape distribution in the plate width direction (warping shape) measured by the plate width direction shape measuring device 31 under a tension of 15 kN for a high-strength steel plate having a plate thickness of 1.0 mm and a plate width of 1220 mm as described above. When an arc is used as an approximation curve, the relationship between the position x in the plate width direction and the warping shape y is expressed by the functional expression shown in the following equation (2) with d, e, and r as constants. Specifically, when an arc is approximated, the error between the shape distribution in the plate width direction as a measured value and the warping shape y obtained by equation (2) is also calculated in a manner to determine a constant that becomes the minimum in the plate width direction.

[0079] [Mathematical formula 2]

[0080]

[0081] The warpage shape estimation unit 35 estimates the warpage shape in the plate width direction of the metal strip 1 in the tension-free state using the plate width direction shape distribution of the metal strip 1 measured by the plate width direction shape measurement device 31 and the approximate curve calculated by the approximate curve calculation unit 34. Specifically, the warpage shape estimation unit 35 subtracts the approximate curve calculated by the approximate curve calculation unit 34 from the plate width direction shape distribution measured by the plate width direction shape measurement device 31, thereby estimating the warpage shape in the plate width direction of the metal strip 1 in the tension-free state. That is, the warpage shape value at the corresponding plate width direction position of the approximate curve calculated by the approximate curve calculation unit 34 is subtracted from the warpage shape value at each position in the plate width direction measured by the plate width direction shape measurement device 31, thereby determining the warpage shape in the tension-free state.

[0082] Here, use Fig.10 An example in which the warpage shape estimation unit 35 estimates the warpage shape in the tension-free state in the board width direction using the board width direction shape distribution in the tension-applied state measured by the board width direction shape measurement device 31 and the approximate curve (quadratic curve) calculated by the approximate curve calculation unit 34 will be described. Fig.10 This is a diagram showing an example of a warping shape in the sheet width direction in a tension-free state estimated using a sheet width direction shape distribution in a tension-applied state and an approximate curve (quadratic curve).

[0083] like Fig.10As shown in FIG. 1 , the warp shape estimated by the warp shape estimation unit 35 in the tension-free state (estimated warp shape) has a slightly larger difference between the maximum and minimum values ​​of the warp shape in the plate width direction and a smaller difference in height between the peak of the warp shape and the valley in the plate width center portion than the warp shape measured in the state where a tension of 15 kN is applied. This is because the longitudinal warp of the metal strip 1 is converted into the warp in the plate width direction, thereby increasing the amplitude of the warp height mainly near the plate width center portion.

[0084] Next, use Fig.11 The estimated warp shape (refer to Fig.10 ) is compared with the actual measured value of the warping shape in the tension-free state. Fig.11 This is a diagram showing an example of comparison between an estimated warp shape and an actually measured value of the warp shape in a tension-free state.

[0085] like Fig.11 As shown, it was confirmed that when the warping shape in the sheet width direction in the tension-free state was estimated based on the sheet width direction shape distribution measured in the tension-applied state, the estimated warping shape had good estimation accuracy.

[0086] In addition, use Fig.12 An example of estimating the warping shape in the sheet width direction in a tension-free state using the sheet width direction shape distribution in a tension-applied state and an approximate curve obtained by approximating the shape distribution with a circular arc will be described. Fig.12 It shows the shape distribution and approximate curve of the plate width direction under tension (refer to Fig. 9 ) is an example of the estimated warping shape in the width direction of the plate in the tension-free state. Fig.12 As shown in FIG. 1 , when the approximate curve approximated by a circular arc is used, the estimated warping shape also has a slightly larger difference between the maximum and minimum values ​​of the warping shape in the plate width direction, and a smaller difference in height between the peak of the warping shape and the valley in the center of the plate width, compared to the warping shape measured under a tension of 15 kN. Fig.13 As shown, even when the estimated warp shape estimated using the approximate curve by arc approximation is compared with the actual measured value of the warp shape in the tension-free state, it is confirmed that the estimation accuracy of the estimated warp shape is good.

[0087] As described above, by using the warpage shape estimation method of the metal strip in the present embodiment, it is possible to estimate the warpage shape in the sheet width direction in a tension-free state from the shape distribution in the sheet width direction in a tension-applied state. The warpage shape estimation method of the metal strip 1 is preferably applied to the cooled metal strip 1 in view of the fact that the metal strip 1 cooled by the cooling zone 8 of the continuous annealing equipment 100 includes a warpage shape that is a quadratic arc approximation curve shape and a warpage shape that is a cubic approximation curve shape. In this case, the sheet width direction shape measurement device 31 is preferably arranged between the cooling section 40 and the coiler 15 of the continuous annealing equipment 100. In addition, the warpage shape measurement step using the sheet width direction shape measurement device 31 is preferably performed after the metal strip 1 is cooled by the cooling section 40 and before it is coiled by the coiler 15 of the continuous annealing equipment 100. This is because, in the continuous annealing equipment 100, the warpage shape in a tension-free state can be estimated without stopping the conveyance of the metal strip 1.

[0088] It is preferable to perform a pass / fail judgment of the metal strip 1 as a quality inspection based on the result of estimating the warping shape of the metal strip 1 in a tension-free state using the warping shape estimation method of the metal strip 1 described above. This is because by performing a quality inspection related to the warping shape during the conveyance of the metal strip 1 (online), it is possible to easily and quickly judge whether the warping shape of the metal strip 1 meets the quality standard. In addition, it is also because an additional process for performing a quality inspection of the warping shape can be omitted. Regarding the pass / fail judgment of the warping shape (pass / fail judgment method), the case where the warping amount exceeds a preset upper limit (for example, 10 mm) in the plate width direction may be regarded as unqualified, and the case where the warping amount is below the upper limit value may be regarded as qualified. In addition, the upper limit of the warping amount as the quality standard may be changed each time according to the number of concave and convex parts or the number of pitches of the warping shape estimated by the warping shape estimation unit 35. This is because, when the number of concave and convex parts of the warping shape in a tension-free state is large and the pitch is short, even when the warping amount is small, processing defects are likely to occur in secondary processing such as stamping. Here, the “warping amount” refers to the difference between the maximum value and the minimum value of the warping shape.

[0089] Furthermore, it is preferable to use the above-mentioned method for estimating the warping shape of the metal strip to determine whether the metal strip 1 is qualified, and to ship the metal strip determined to be qualified, etc. (metal strip manufacturing method). This is because, by manufacturing the metal strip 1 whose warping shape is less than the pre-set reference value of poor quality, an additional process for quality inspection of the warping shape is not required, and the metal strip can be manufactured at low cost. In this case, it is preferable to estimate the warping shape of the metal strip 1 in the plate width direction in the tension-free state at intervals of 5m to 20m in the length direction of the metal strip 1, and only manufacture the qualified part as the metal strip 1. This is because it is guaranteed that the warping shape meets the quality standard throughout the entire length of the metal strip 1 that becomes the product.

[0090] Example

[0091] Hereinafter, an example performed using the warpage shape estimation method of a metal strip according to the present embodiment will be described.

[0092] In this embodiment, Figure 1 In the continuous annealing equipment 100 shown, a plate width direction shape measuring device 31 is arranged on the inspection table 14 of the output side equipment 24 for implementation. When the metal strip 1 passes through the plate width direction shape measuring device 31, a tension of 20MPa to 60MPa is applied to the metal strip 1. The metal strip 1 manufactured by the continuous annealing equipment 100 is a high-strength steel plate with a plate thickness of 1.0 to 1.8mm, a plate width of 800 to 1250mm, and a tensile strength of 1310 to 1470MPa. The total weight of the high-strength steel plate used in the embodiment is 15,000 tons.

[0093] The cooling zone 8 of the continuous annealing equipment 100 is provided with Figure 2 The cooling section 40 of the water cooling method shown in the figure is provided with a water cooling nozzle unit 41, and the water cooling nozzle unit 41 has a plurality of nozzles for spraying water as a cooling fluid from the surface side and the back side of the metal strip 1. In this embodiment, as the cooling conditions in the cooling section 40, the cooling start temperature of the metal strip 1 is controlled to 740°C, and the cooling end temperature is controlled to 30°C. The flow rate of the cooling water sprayed from the water cooling nozzle unit 41 is 1000m 3 / hr, and the water temperature is 30° C. In this case, the high-strength steel sheet (metal strip 1 ) used in this example has a warpage shape distribution that can be approximated by a cubic approximation curve in the sheet width direction due to the influence of thermal contraction and phase transformation in the cooling section 40 .

[0094] The plate width direction shape measuring device 31 arranged on the inspection table 14 is composed of a laser scanning distance meter that measures the warpage shape by a distance measurement method. In addition, two laser scanning distance meters are arranged in parallel along the plate width direction of the metal strip 1. The shape distribution in the plate width direction of the metal strip 1 (plate width direction shape distribution) is measured by scanning the laser along the plate width direction of the metal strip 1. The measurement frequency of the plate width direction shape measuring device 31 is set to 20Hz. Therefore, under the condition that the maximum conveying speed of the metal strip 1 in the output side equipment 24 of the continuous annealing equipment 100 is 600m / min, the measurement data of the warpage shape is collected at a pitch of 1m in the length direction of the metal strip 1.

[0095] The approximate curve calculation unit 34 calculates an approximate curve approximated by a quadratic curve in the sheet width direction of the metal strip 1 for each position in the length direction of the metal strip 1, based on the measurement result of the sheet width direction shape distribution of the metal strip 1 in the tension-applied state measured by the sheet width direction shape measurement device 31. The warp shape estimation unit 35 estimates the warp shape (estimated warp shape) in the sheet width direction of the metal strip 1 in the tension-free state for each position in the length direction of the metal strip 1 by subtracting the calculated approximate curve from the measurement result of the sheet width direction shape distribution.

[0096] In this embodiment, a pass / fail judgment unit related to the warping shape of the metal strip 1 is provided, and the upper limit of the pass / fail judgment of the warping amount (the difference between the maximum value and the minimum value of the warping shape) of the warping shape in the plate width direction is set to 10 mm. It should be noted that the warping amount is calculated from the warping shape in the plate width direction of the metal strip 1 except for the plate width end 10 mm. This is because, in this case, trimming (cutting) is performed on the rewinding line within the range of 10 mm from the plate width end of the metal strip 1, and it will not become a product. In the pass / fail judgment unit, it is judged whether the warping amount of the warping shape is below the upper limit value for each position in the length direction of the metal strip 1. In the pass / fail judgment, the case where the warping amount is below the upper limit value at each position in the length direction of the metal strip 1 is considered to be passed, and the case where the warping shape is estimated to exceed the upper limit value at at least any position is considered to be unqualified.

[0097] In this embodiment, after the metal strip 1 is further wound by the coiler 15 of the continuous annealing equipment 100, the coiled metal strip is transported to the inspection line (rewinding line). Then, in the inspection line, the warping shape of the metal strip in the sheet width direction in a tension-free state is measured (measured warping shape).

[0098] As a result, the ratio (accuracy) of the number of metal strips whose judgment results of the pass / fail judgment unit and the actually measured warping shapes are both qualified and the number of metal strips whose judgment results of the pass / fail judgment unit and the actually measured warping shapes are both unqualified to the number of metal strips judged to be qualified is 88%.

[0099] In addition, the approximate curve calculation unit 34 also calculates an approximate curve approximated by an arc in the sheet width direction of the metal strip 1 for each position in the length direction of the metal strip 1 based on the measurement result of the sheet width direction shape distribution of the metal strip 1 in the tension state measured by the sheet width direction shape measurement device 31. Furthermore, when the arc is calculated as the approximate curve, the warpage shape estimation unit 35 also estimates the warpage shape in the sheet width direction of the metal strip 1 in the tension-free state for each position in the length direction of the metal strip 1 by subtracting the calculated approximate curve (arc) from the measurement result of the sheet width direction shape distribution.

[0100] As a result, the ratio (accuracy) of the number of metal strips whose judgment results of the pass / fail judgment unit and the actually measured warping shapes are both qualified and the total number of metal strips whose judgment results of the pass / fail judgment unit and the actually measured warping shapes are both unqualified to the number of metal strips subjected to pass / fail judgment is 85%.

[0101] On the other hand, as a comparative example, the pass / fail judgment was performed without estimating the warping shape in the plate width direction of the metal strip in the tension-free state using the plate width direction shape distribution of the metal strip in the tension-applied state measured by the plate width direction shape measuring device 31. That is, in the plate width direction shape distribution of the metal strip in the tension-applied state, it was judged whether the warping amount of the warping shape in the plate width direction was below the upper limit value, and compared with the pass / fail judgment result of the measured warping shape. As a result, in the comparative example, the ratio (accuracy) of the total number of metal strips whose plate width direction shape distribution and the measured warping shape were both pass and the number of metal strips whose plate width direction shape distribution and the measured warping shape were both unpass to the number of metal strips subjected to pass / fail judgment was 60%.

[0102] From the above, it can be confirmed that by using the warping shape estimation method of the metal strip of this embodiment, the warping shape in the width direction of the plate caused by the rapid cooling of the metal strip can be estimated based on the warping shape in the width direction of the plate in the state where tension is applied in the length direction.

[0103] Description of Reference Numerals

[0104] 1 Metal belt

[0105] 2 Unwinding machine

[0106] 3. Welding Machine

[0107] 4 Input side looper

[0108] 5 Preheating Zone

[0109] 6 Heating Zones

[0110] 7. Heat distribution area

[0111] 8 Cooling Zone

[0112] 9 Reheating Zone

[0113] 10 Expiration zone

[0114] 11 Final cooling zone

[0115] 12 Output side looper

[0116] 13 Shape Correction Equipment

[0117] 14. Examination Table

[0118] 15 Winding Machine

[0119] 20 Input side equipment

[0120] 21 Furnace equipment

[0121] 22 Annealing equipment

[0122] 23 Reheating equipment

[0123] 24 Output side equipment

[0124] 30 Warp shape estimation equipment

[0125] 31 Plate width direction shape measuring device

[0126] 32 Warp shape estimation device

[0127] 33 Acquisition

[0128] 34 Approximate curve calculation unit

[0129] 35 Warp shape estimation unit

[0130] 36 Output

[0131] 40 Cooling unit

[0132] 41 Water cooling nozzle unit

[0133] 43 Dipping Tank

[0134] 44 Cooling water

[0135] 45 Pressing roller

[0136] 46, 47 deflector roller

[0137] 48 Dewatering Roller

[0138] 49 Drying furnace

[0139] 100 Continuous annealing equipment

Claims

1. A method for estimating the warping shape of a metal strip, comprising estimating the warping shape of the metal strip in the plate width direction in a tension-free state after the tension is removed, based on the shape of the metal strip in the plate width direction in a tension-applied state in which the tension is applied in the length direction, wherein: The warping shape estimation method of the metal strip has the following features: a plate width direction shape measuring step, measuring the plate width direction shape distribution of the metal strip under the tension applied state; an approximate curve calculation step of calculating an approximate curve obtained by approximating the plate width direction shape distribution measured in the plate width direction shape measurement step using a quadratic curve or a circular arc; and The warping shape estimating step estimates the warping shape in the sheet width direction of the metal strip in the tension-free state using the sheet width direction shape distribution and the approximate curve.

2. The method for estimating the warpage shape of a metal strip according to claim 1, wherein: In the plate width direction shape measuring step, the plate width direction shape distribution of the metal strip is measured by a distance measurement method or a light section method.

3. The method for estimating the warped shape of a metal strip according to claim 1 or 2, wherein: The sheet width direction shape measuring step is performed after the metal strip is cooled by a cooling section of a continuous annealing facility and before it is wound by a coiler of the continuous annealing facility.

4. A method for determining whether a metal strip is qualified or not, wherein: The quality of the metal strip is determined based on the warping shape of the metal strip in the tension-free state estimated by the warping shape estimation method of the metal strip according to any one of claims 1 to 3.

5. A method for manufacturing a metal strip, wherein: The metal strip is judged to be acceptable by using the metal strip acceptance judgment method according to claim 4, and the metal strip judged to be acceptable is manufactured.

6. A warping shape estimation device for a metal strip, which estimates the warping shape of the metal strip in the plate width direction in a tension-free state after the tension is removed, based on the shape of the metal strip in the plate width direction in a tension-applied state in which the tension is applied in the length direction, wherein: The warpage shape estimation device of a metal strip has: A plate width direction shape measuring device, which measures the plate width direction shape distribution of the metal strip under the tension applied state; and A warping shape estimation device for a metal strip estimates the warping shape of the metal strip in the plate width direction in the tension-free state, The warping shape estimation device of the metal strip comprises: an acquisition unit, which acquires the plate width direction shape distribution of the metal strip from the plate width direction shape measuring device; an approximate curve calculation unit, which calculates an approximate curve obtained by approximating the plate width direction shape distribution measured in the plate width direction shape measuring device using a quadratic curve or a circular arc; and a warping shape estimation unit, which uses the plate width direction shape distribution and the approximate curve to estimate the warping shape in the plate width direction of the metal strip in the tension-free state.

7. The warpage shape estimation device of a metal strip according to claim 6, wherein: The plate width direction shape measuring device measures the plate width direction shape distribution of the metal strip by a distance measurement method or a light section method.

8. The warping shape estimation device of a metal strip according to claim 6 or 7, wherein: The plate width direction shape measuring device is disposed between a cooling section and a coiler of a continuous annealing facility that performs a heat treatment on the metal strip.

Images