Steel plate manufacturing method and steel plate manufacturing equipment

Abstract

To provide a manufacturing method and a facility for a steel plate capable of reducing occurrence of a stop mark.SOLUTION: A manufacturing method for steel plates includes performing manufacturing operation while correcting a steel plate shape by a roll unit disposed in a steel plate conveyance direction. In this method, when regulating an open / draft elevating speed for the roll unit steel plate as X, a push-in amount of the steel plate by the roll unit as Y, an adjustable speed rate of the line on which the plate is conveyed as Z and a set value of a line speed of starting opening operation of the steel plate-drafting roll unit as α, a control device decides the set value α in response to a value of Z×Y / X, and makes the opening operation of the roll unit start when the current line speed reaches the set value α.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a steel sheet and a steel sheet manufacturing facility. [Background technology]

[0002] A shape straightening device is installed in steel plate processing facilities such as continuous annealing lines and finishing lines, and is a facility in which units with different roles for straightening the shape (local elongation and warpage) of a steel plate are arranged in the conveying direction (pass line direction) of the steel plate. This shape straightening device straightens the shape of the steel plate by pressing straightening rolls against the front and back sides of the steel plate.

[0003] The shape straightening device is used to improve unevenness and warpage in the conveying direction and the sheet width direction caused by local elongation (ununiform elongation) of the steel sheet. However, when the conveying of the steel sheet is interrupted for, for example, inspection of the steel sheet while the shape straightening device is in use (while the steel sheet is being pressed down), a pressing mark, i.e., a "stop mark (also called a roll mark, etc.)" may occur on the contact part of the steel sheet with the straightening roll. In order to avoid or reduce the occurrence of such stop marks, for example, Patent Documents 1 to 3 disclose the following techniques.

[0004] Patent Document 1 discloses a method for controlling the rolling load or reduction position and the rolling tension, either alone or in combination, according to the rolling speed of the shape straightening device (=line speed) when the line is decelerated and temporarily stopped during shape straightening of a steel plate and then the line is accelerated again to resume shape straightening.

[0005] Patent Document 2 discloses a method of changing the bending force according to the plate thickness and shape of the steel plate after it has passed through a shape straightening device, by utilizing bending means for imparting roll bending (IMR: intermediate roll, BUR: backup roll) that is installed in the same unit as the straightening roll (WR: work roll) that comes into direct contact with the steel plate.

[0006] Patent Document 3 discloses a method for controlling the straightening rolls so as not to cause slip defects on the surface of the steel plate or on the straightening rolls when the straightening rolls are pressed down or released while traveling during shape straightening of the steel plate (while the line is operating). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 2573459 [Patent Document 2] Japanese Patent Application Publication No. 6-47415 [Patent Document 3] JP 2014-58001 A Summary of the Invention [Problem to be solved by the invention]

[0008] The methods disclosed in Patent Documents 1 and 2 are intended to reduce the occurrence of stop marks while performing shape straightening on a steel sheet, but the steel sheet is continuously pressed down by the straightening rolls throughout the shape straightening process. Therefore, if the straightening rolls are released when the transport of the steel sheet is interrupted (temporarily stopped) and then pressed down again by the straightening rolls when the transport is resumed, this is not sufficient to reduce the occurrence of stop marks during the re-pressing process.

[0009] The method disclosed in Patent Document 3, unlike Patent Documents 1 and 2, releases and reduces the straightening rolls while the steel plate is running during shape straightening. The command calculation device that controls the release and reduction in Patent Document 3 has a feature of executing calculations when the rolling speed of the steel plate during shape straightening is less than 30 (mpm).

[0010] However, in the method disclosed in Patent Document 3, depending on the steel sheet to be shape-straightened, the set value of the push-in amount required for shape straightening may be large. In this case, if the straightening rolls are released at less than 30 (mpm), the release is not yet complete when the conveyance of the steel sheet is stopped, and stop marks are formed until the release is completely completed.

[0011] The present invention has been made in view of the above, and has an object to provide a steel plate manufacturing method and steel plate manufacturing equipment that can reduce the occurrence of stop marks. [Means for solving the problem]

[0012] In order to solve the above-mentioned problems and achieve the object, the manufacturing method of steel sheet according to the present invention is a manufacturing method of steel sheet in which the steel sheet is manufactured while correcting the shape of the steel sheet by a roll unit arranged in the conveying direction of the steel sheet, in which, assuming that the opening / reduction lifting speed of the roll unit with respect to the steel sheet is X, the amount of pushing of the steel sheet by the roll unit is Y, the acceleration / deceleration rate of the line along which the steel sheet is conveyed is Z, and a set value of the line speed at which the opening operation of the roll unit pressing down the steel sheet is started is α, a control device determines the set value α in accordance with the value of Z×Y / X, and starts the opening operation of the roll unit when the current line speed reaches the set value α.

[0013] Furthermore, in the method for manufacturing a steel plate according to the present invention, in the above-mentioned invention, the control device determines the value of Z×Y / X as the set value α when the yield strength of the steel plate is within a predetermined range, and determines a value smaller than the value of Z×Y / X as the set value α when the yield strength of the steel plate is higher than the predetermined range.

[0014] In addition, in the manufacturing method of steel plate according to the present invention, in the above invention, the control device starts an opening operation of the roll unit based on the current line speed and the set value α when the transportation of the steel plate stops, and starts a pressing operation of the steel plate by the roll unit so that the predetermined push-in amount Y is reached when the transportation of the steel plate is resumed.

[0015] In order to solve the above-mentioned problems and achieve the object, the steel plate manufacturing equipment of the present invention is provided with a roll unit that is arranged in the conveying direction of the steel plate and corrects the shape of the steel plate, and a control device, in which, assuming that the opening / reduction lifting speed of the roll unit with respect to the steel plate is X, the amount of pushing of the steel plate by the roll unit is Y, the acceleration / deceleration rate of the line along which the steel plate is conveyed is Z, and a set value of the line speed at which the opening operation of the roll unit that is pressing down the steel plate is started is α, the control device determines the set value α in accordance with the value of Z×Y / X, and starts the opening operation of the roll unit when the current line speed reaches the set value α. Effect of the Invention

[0016] According to the present invention, the set value α is determined based on the opening / reduction lifting speed X, the push-in amount Y, and the acceleration / deceleration rate Z, and the opening operation of the roll unit is started based on the set value α, so that the opening of the roll unit can be completed when the conveyance of the steel sheet stops. This makes it possible to reduce the occurrence of stop marks on the steel sheet. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a shape correction device in a steel plate manufacturing facility according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a state before the work rolls are released when the conveyance on the line is interrupted in the steel sheet manufacturing method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A method for manufacturing a steel sheet and a steel sheet manufacturing facility according to an embodiment of the present invention will be described with reference to the drawings. Note that the components in the following embodiments include those that are easily replaceable by a person skilled in the art, or those that are substantially the same.

[0019] FIG. 1 shows an example of the configuration of a shape correction device 1 included in a steel sheet manufacturing facility according to this embodiment. The shape correction device 1 is for correcting the shape of the steel sheet S by a plurality of roll units arranged in the conveying direction of the steel sheet S. As shown in the figure, this shape correction device 1 includes a local elongation correction unit 10, a first warpage correction unit 20, a second warpage correction unit 30, and a control device 40. In the following, the local elongation correction unit 10, the first warpage correction unit 20, and the second warpage correction unit 30 are also referred to as "roll units".

[0020] Here, in FIG. 1, a shape correction device 1 consisting of a total of three units is shown as an example, but the manufacturing method of the steel sheet according to this embodiment can be applied to other shape correction devices than the shape correction device 1 shown in the figure. For example, instead of the three units (one local elongation correction unit and two warp correction units) shown in the figure, the shape correction device may be composed of two units (one local elongation correction unit and one warp correction unit) or four units (two local elongation correction units and two warp correction units). Furthermore, the manufacturing method of the steel sheet according to this embodiment can be applied to shape correction devices having configurations other than those described above, as long as they have at least a function of transporting the steel sheet S while applying tension and a function of correcting the shape of the steel sheet S by a work roll.

[0021] The local elongation correcting unit 10 is for correcting local elongation (non-uniform elongation) of the steel sheet S. This local elongation correcting unit 10 includes a plurality of work rolls (straightening rolls) 11, a plurality of intermediate rolls 12, and a plurality of backup rolls 13.

[0022] The first warp correction unit 20 is for correcting warp of the steel sheet S. This first warp correction unit 20 includes a work roll 21, a plurality of intermediate rolls 22, a plurality of backup rolls 23, and a plurality of deflector rolls 24.

[0023] The second warp correction unit 30 is for correcting warp of the steel sheet S. This second warp correction unit 30 includes a plurality of work rolls 31, a plurality of intermediate rolls 32, and a plurality of backup rolls 33.

[0024] The control device 40 is for controlling the operation of each roll unit (the local elongation correction unit 10, the first warp correction unit 20, and the second warp correction unit 30). The control device 40 controls the pressing operation and the releasing operation of each roll unit.

[0025] The "rolling down operation" refers to the operation of bringing the work rolls 11, 21, 31 of each roll unit close to the steel sheet S on the conveying line (hereinafter referred to as the "line") and rolling down the steel sheet S to a desired pressing amount. The "releasing operation" refers to the operation of moving the work rolls 11, 21, 31 that are rolling down the steel sheet S away from the steel sheet S and releasing the rolling down.

[0026] The control device 40 controls the pressing operation and the releasing operation so that they are performed simultaneously by the work rolls 11, 21, and 31 of each roll unit. In addition, in the shape correction device 1 shown in Fig. 1, the control device 40 changes the amount of pressing into the steel sheet S by fixing the unit arranged on the upper side among the roll units and raising and lowering the unit arranged on the lower side.

[0027] When the transportation of the steel sheet S is stopped, for example, for inspection of the steel sheet S, the control device 40 starts the opening operation of the work rolls 11, 21, 31 based on the current line speed and a set value of the line speed at which the opening of the work rolls 11, 21, 31 of each roll unit starts (hereinafter referred to as the "opening start speed set value"). On the other hand, when the transportation of the steel sheet S is resumed, the control device 40 starts the pressing operation of the steel sheet S by the work rolls 11, 21, 31 of the roll unit so as to achieve a preset push-in amount. The current line speed is constantly measured by a measuring device (not shown) and is input to the control device 40 every time it is measured.

[0028] In this way, while the line is suspended (temporarily stopped), the control device 40 releases the work rolls 11, 21, 31 to a position where the work rolls 11, 21, 31 just contact the steel sheet S (a position where the push-in amount is 0 (mm)), and keeps them on standby until the line is resumed. Then, at the same time as the line is resumed, the control device 40 increases the input tension of the shape correction device 1 from a relief tension (a tension when the shape correction device 1 is not in use) to a high tension when the shape correction device 1 is in use, and starts pushing the work rolls 11, 21, 31 to a preset push-in amount. This makes it possible to perform shape correction of the steel sheet S by light reduction without generating unstraightened parts. In other words, after the set value of the push-in amount is reached, the desired roll-in amount has been secured, and normal shape correction is performed.

[0029] 2 is a diagram showing a state before the work rolls (work rolls 11, 21, 31) are released when transportation on the line is interrupted in the steel sheet manufacturing method according to this embodiment. As shown in the figure, in this embodiment, the release / pressure reduction lifting speed of the work rolls of the roll unit relative to the steel sheet S is X (mm / s), the amount of pressing of the steel sheet S by the work rolls is Y (mm), and the acceleration / deceleration rate of the line along which the steel sheet S is transported is Z (mpm / s).

[0030] The release / reduction lifting speed X is a value indicating how fast the work rolls lift and lower per unit time, and is set in advance for each manufacturing facility of the steel sheet S. The push-in amount Y is set according to the size of the shape (local elongation and warpage) of the steel sheet S to be corrected, etc. The acceleration / deceleration rate Z is a value indicating how fast the line accelerates / decelerates per unit time, and is set in advance for each manufacturing facility of the steel sheet S.

[0031] In this case, the control device 40 calculates the value of "Z×Y / X" and, according to this value, determines (sets) the opening start speed set value α (mpm) of the work rolls that are rolling down the steel sheet S. Then, the control device 40 starts the opening operation of the work rolls when the current line speed reaches the opening start speed set value α.

[0032] The value of "Z×Y / X" means a value such that, on a line set at an acceleration / deceleration rate Z (mpm / s), the opening of the work roll at the opening / pressure reduction lifting speed X (mm / s) is completed before the push-in amount Y (mm) becomes 0. In this way, by making it possible to set the line speed at which the opening of the work rolls begins (opening start speed set value α) and starting the opening operation of the work rolls based on this opening start speed set value α, it is possible to complete the opening of the work rolls when the transport of the steel sheet S stops.

[0033] Here, when the yield strength of the steel sheet S is within a predetermined range (e.g., 200 to 350 (MPa)), the control device 40 determines the value of Z×Y / X as the opening start speed set value α. When the yield strength of the steel sheet S is higher than the predetermined range (e.g., 450 to 1000 (MPa)), the control device 40 determines a value smaller than the value of Z×Y / X as the opening start speed set value α. In this way, by setting the opening start speed set value α according to the yield strength of the steel sheet S, it is possible to reduce the occurrence of stop marks in the steel sheet S regardless of the material.

[0034] The yield strength (MPa) of the steel plate S can be evaluated, for example, by taking a JIS No. 5 tensile test piece along the rolling direction and conducting a tensile test in accordance with "JIS Z 2241." The yield strength can be evaluated at the upper yield point or, if no upper yield point is observed, at the 0.2% proof stress.

[0035] In the steel plate manufacturing method and steel plate manufacturing equipment according to this embodiment as described above, as a countermeasure for the case where a certain amount of contact time between the work rolls 11, 21, 31 and the steel plate S may occur due to an interruption (pause) of line operation while the steel plate S is being reduced by the work rolls 11, 21, 31, the work rolls 11, 21, 31 are released when the line operation is interrupted, and the steel plate S is reduced again when the line operation is resumed.

[0036] At that time, the opening start speed set value α (mpm) is determined based on the opening / reduction lifting speed X, the push-in amount Y and the acceleration / deceleration rate Z, and the opening operation of the work rolls 11, 21, 31 is started based on the opening start speed set value α (mpm), thereby completing the opening of the work rolls 11, 21, 31 when the transport of the steel sheet S stops. This makes it possible to reduce the occurrence of stop marks on the steel sheet S.

[0037] Furthermore, according to the steel plate manufacturing method and steel plate manufacturing equipment of this embodiment, the work rolls 11, 21, 31 can be automatically switched between open (used) and reduced (unused) in the shape straightening device 1, thereby minimizing the occurrence of stop marks both when the line is stopped and when it is restarted. Furthermore, according to the steel plate manufacturing method and steel plate manufacturing equipment of this embodiment, when the work rolls 11, 21, 31 are opened / reduced during transport, the open / reduced parts during transport can be treated as lightly reduced parts to perform shape straightening without generating unstraightened parts of the steel plate S.

[0038] Furthermore, compared to releasing the work rolls 11, 21, 31 after the conveyance of the steel sheet S has completely stopped, the occurrence of stop marks is reduced when the work rolls 11, 21, 31 are released during conveyance. Therefore, assuming a process production, it is possible to reduce the possibility that stop marks will cause shape defects that will prevent the product from being made. EXAMPLES

[0039] An example of the steel sheet manufacturing method and steel sheet manufacturing equipment according to the present embodiment will be described. In this example, shape straightening of a steel sheet was performed using the shape straightening device according to the present invention in a finishing line after cold annealing.

[0040] The steel plates used had a thickness of 0.4 to 1.6 mm and a width of 800 to 1600 mm. The shape correction device used was a three-unit type similar to that shown in Figure 1. The yield strength (MPa) of the steel plates was evaluated by taking JIS No. 5 tensile test pieces along the rolling direction and conducting a tensile test in accordance with "JIS Z 2241". The yield strength was evaluated at the upper yield point or 0.2% proof stress when no upper yield point was observed.

[0041] In order to correct the "local elongation" and "warping" of the steel plate, the tension of the steel plate at the entrance and exit of the shape straightening device and the pressing amount Y of the work roll of each roll unit against the steel plate were adjusted. As a result, the height of the local elongation, which was a maximum of approximately 10 (mm) before shape straightening (= the height of the steel plate floating vertically above the plate when the tension of the steel plate is cut and the steel plate is hanging down on the plate), could be corrected to a maximum of 0 (mm) by shape straightening. In addition, when the edge of the steel plate after shape straightening was cut and measured, the warping of the steel plate was also corrected to 0 (mm).

[0042] In this example, the variables used were the release / pressure lifting speed X (mm / s) of the work rolls of the roll unit relative to the steel sheet S, the push-in amount Y (mm) of the steel sheet by the work rolls, and the acceleration / deceleration rate Z (mpm / s) of the line along which the steel sheet is transported.

[0043] Consider the case where the steel plate is mild steel (low carbon steel), the product thickness is 2.4 (mm), and the yield strength is 240 (MPa). In this case, if X = 5.0 (mm / s), Y = 8.0 (mm), and Z = 15.0 (mpm / s), the time it takes for the work roll to be released from the push-in amount Y to the position where the steel plate and the work roll just come into contact is "Y / X = 1.6 (s)".

[0044] When the line is decelerating at an acceleration / deceleration rate Z (mpm / s), the line stops exactly after 1.6 (s) (0 (mpm)), and Z (mpm / s) × Y (mm) / X (s) = 24.0 (mpm). In this case, by setting the threshold line speed value at which the switch from rolling to releasing is activated, that is, the release start speed setting value α of the work rolls rolling the steel plate, to 24.0 (mpm), the work rolls are released at the same time as the line stops. In addition, when α = 24.0 (mpm), the length of the light pressing lower part is 24.0 (mpm) × 1.6 (s) / 60 (s / min) × 1 / 2 = 0.3 (m). The "length of the light pressing lower part" refers to the length of the part where the work rolls are in contact with the steel plate until the line decelerates and the release of the work rolls is completed.

[0045] In this way, when the yield strength of the steel sheet S is within a predetermined range (for example, 200 to 350 (MPa)), the value of Z×Y / X (=24.0 (mpm)) is set as the opening start speed set value α. In this case, if the opening start speed set value α is set to less than the value of Z×Y / X (=24.0 (mpm)), the occurrence of unstraightened portions can be prevented. However, because the opening of the work rolls is not completed even after the line is stopped, stop marks are generated for the time that the work rolls are pressing down the steel sheet until the opening of the work rolls is completed.

[0046] Also, if the release start speed setting value α is set to be greater than the value of Z×Y / X (=24.0 (mpm)), the occurrence of stop marks can be prevented. However, since the work roll release is completed before the line stops, unstraightened parts are generated, and the shape cannot be guaranteed.

[0047] Here, the technology of the conventional Patent Document 3 (JP Patent Publication 2014-58001 A) (see claim 3) is applied to this embodiment. For example, as in the above, when X=5.0 (mm / s), Y=8.0 (mm), and Z=15.0 (mpm / s), α is set to 27.0 (mpm). In this case, the technology of Patent Document 3 sets α to less than 30.0 (mpm) so that no shape defects are generated, but an unstraightened portion is generated. On the other hand, in the present invention, by setting α≦Z×Y / X according to the yield strength of the steel plate from the generalized X, Y, and Z, the present invention is not limited to "less than 30.0 (mpm)" as in Patent Document 3, and can be applied to any other shape straightening device specifications.

[0048] For example, consider the case where the steel plate is soft steel (low carbon steel), the product thickness is 2.4 (mm), the yield strength is 240 (MPa), and X = 5.0 (mm / s), Y = 16.0 (mm), and Z = 15.0 (mpm / s). In this case, by setting α to 48.0 (mpm), it is possible to suppress the occurrence of unstraightened areas and stop marks.

[0049] The above calculation example is an example assuming mild steel, which is prone to stop marks even if the line stop time until the work rolls are released is relatively short. On the other hand, in the case of hard steel, even if the work rolls press the steel plate for a certain period of time when the line is stopped, it is considered that the higher the yield strength of the steel plate, the less likely stop marks will occur. For example, consider the case where X = 5.0 (mm / s), Y = 16.0 (mm), and Z = 15.0 (mpm / s) when the steel plate is hard steel (high Mn steel), the product thickness is 1.6 (mm), and the yield strength is 530 (MPa). In this case, even if α is set to a value smaller than 48.0 (mpm), stop marks are less likely to occur compared to the case of mild steel.

[0050] Table 1 shows the results of an investigation into the occurrence of stop marks and unstraightened areas for several steel plates under the above-mentioned assumptions. As shown in Table 1, the occurrence of both stop marks and unstraightened areas was evaluated as "X", and the absence of both was evaluated as "O".

[0051] [Table 1]

[0052] In Table 1, Nos. 1 to 4 are comparative examples in which a reference material (soft steel) was used, Nos. 5 to 7 are examples (invention examples) in which the reference material (soft steel) was used, No. 8 is an example in which a material harder than the reference material (hard steel) was used, No. 9 is a comparative example in which a material harder than the reference material (hard steel) was used, and Nos. 10 and 11 are comparative examples in which a material softer than the reference material was used.

[0053] In the present embodiment, the "reference material" refers to a material having a yield strength in the range of 200 to 350 (MPa), for example. The "material harder than the reference material" refers to a material having a yield strength in the range of 450 to 1000 (MPa), for example. The "material softer than the reference material" refers to a material having a yield strength in the range of 100 to 190 (MPa), for example. The investigation results in Table 1 will be described in detail below.

[0054] (No.1) No.1 has a yield strength of 225 (MPa), X = 5.0 (mm / s), Y = 8.0 (mm), Z = 15.0 (mpm / s), and Z × Y / X = 24.0 (mpm). In this case, when the opening start speed setting value α was set to "20.0 (mpm)" which is smaller than the value of Z × Y / X, no uncorrected parts were generated (evaluated as ◯), but stop marks were generated (evaluated as ×).

[0055] (No.2) No. 2 has a yield strength of 225 (MPa), X = 5.0 (mm / s), Y = 8.0 (mm), Z = 15.0 (mpm / s), and Z × Y / X = 24.0 (mpm). In this case, when the opening start speed setting value α was set to "28.0 (mpm)", which is larger than the value of Z × Y / X, no stop marks were generated (evaluated as ◯), but uncorrected areas were generated (evaluated as ×).

[0056] (No.3) No. 3 has a yield strength of 225 (MPa), X = 5.0 (mm / s), Y = 16.0 (mm), Z = 15.0 (mpm / s), and Z × Y / X = 48.0 (mpm). In this case, when the opening start speed setting value α was set to "28.0 (mpm)" which is smaller than the value of Z × Y / X, no uncorrected parts were generated (evaluated as ◯), but stop marks were generated (evaluated as ×).

[0057] (No.4) No. 4 has a yield strength of 225 (MPa), X = 10.0 (mm / s), Y = 8.0 (mm), Z = 15.0 (mpm / s), and Z × Y / X = 12.0 (mpm). In this case, when the opening start speed setting value α was set to "20.0 (mpm)" which is larger than the value of Z × Y / X, no stop marks were generated (evaluated as ◯), but uncorrected areas were generated (evaluated as ×).

[0058] (No.5) No. 5 has a yield strength of 225 (MPa), X = 5.0 (mm / s), Y = 8.0 (mm), Z = 15.0 (mpm / s), and Z × Y / X = 24.0 (mpm). In this case, when the opening start speed setting value α was set to 24.0 (mpm), which is the same as the value of Z × Y / X, no stop marks or uncorrected areas were generated (both were evaluated as ◯).

[0059] (No.6) No. 6 has a yield strength of 225 (MPa), X = 5.0 (mm / s), Y = 16.0 (mm), Z = 15.0 (mpm / s), and Z × Y / X = 48.0 (mpm). In this case, when the opening start speed setting value α was set to "48.0 (mpm)", which is the same as the value of Z × Y / X, no stop marks or uncorrected areas were generated (both were evaluated as ◯).

[0060] (No.7) No. 7 has a yield strength of 225 (MPa), X = 10.0 (mm / s), Y = 8.0 (mm), Z = 15.0 (mpm / s), and Z × Y / X = 12.0 (mpm). In this case, when the opening start speed setting value α was set to "12.0 (mpm)", which is the same as the value of Z × Y / X, no stop marks or uncorrected areas were generated (both were evaluated as ◯).

[0061] (No.8) No. 8 has a yield strength of 540 (MPa), X = 12.0 (mm / s), Y = 16.0 (mm), Z = 36.0 (mpm / s), and Z × Y / X = 48.0 (mpm). In this case, when the release start speed setting value α was set to 40.0 (mpm), which is smaller than the value of Z × Y / X, neither stop marks nor unstraightened areas were generated (both were evaluated as ◯). In this way, since the material of No. 8 is hard, if the contact between the work roll and the steel sheet is relatively short, stop marks will not be generated even if α is set smaller than the value of Z × Y / X.

[0062] (No.9) No.9 has a yield strength of 540 (MPa), X = 12.0 (mm / s), Y = 16.0 (mm), Z = 36.0 (mpm / s), and Z × Y / X = 48.0 (mpm). In this case, when the release start speed setting value α was set to "20.0 (mpm)" which is smaller than the value of Z × Y / X, no uncorrected parts were generated (evaluation ◯), but stop marks were generated (evaluation ×). In No.9, the difference between the value of Z × Y / X and α is larger than that of No.8. Therefore, when the difference between the value of Z × Y / X and α becomes a certain amount or more, the occurrence of stop marks cannot be ignored even if the material is hard.

[0063] (No.10) For No.10, the yield strength is 150 (MPa), X = 10.0 (mm / s), Y = 12.0 (mm), Z = 20.0 (mpm / s), and Z×Y / X = 24.0 (mpm). In this case, when the opening start speed setting value α was set to "30.0 (mpm)", which is larger than the value of Z×Y / X, both a stop mark and an uncorrected portion occurred (both were evaluated as ×). Thus, since the material of No.10 is soft, even when it is opened during conveyance, a stop mark may occur.

[0064] (No.11) For No.11, the yield strength is 150 (MPa), X = 10.0 (mm / s), Y = 12.0 (mm), Z = 20.0 (mpm / s), and Z×Y / X = 24.0 (mpm). In this case, when the opening start speed setting value α was set to "40.0 (mpm)", which is larger than the value of Z×Y / X, no stop mark occurred (evaluated as 〇), but an uncorrected portion occurred (evaluated as ×).

[0065] As described above, it was found that by setting "α = Z×Y / X" for the reference material and "α < Z×Y / X" for materials harder than the reference material, the occurrence of both stop marks and uncorrected portions can be suppressed.

[0066] As described above, the method for manufacturing a steel sheet and the manufacturing equipment for a steel sheet according to the present invention have been specifically described by the embodiments and examples for carrying out the invention. However, the gist of the present invention is not limited to these descriptions and must be broadly interpreted based on the descriptions in the claims. Also, it goes without saying that various changes, modifications, etc. based on these descriptions are also included in the gist of the present invention.

Explanation of Signs

[0067] 1 Shape correction device 10 Local elongation correction unit 11 Work roll (correction roll) 12 Intermediate roll 13 Backup Role 20 First warping unit 21 Work roll (straightening roll) 22 Intermediate roll 23 Backup Role 24 Deflor (Deflector Roll) 30 Second warping unit 31 Work roll (straightening roll) 32 Intermediate roll 33 Backup Role 40 Control device S steel plate

Claims

1. A method for producing a steel sheet, in which a shape of the steel sheet is corrected by a roll unit arranged in a conveying direction of the steel sheet while the steel sheet is being produced, When the opening / reduction lifting speed of the roll unit with respect to the steel sheet is X, the pushing amount of the steel sheet by the roll unit is Y, the acceleration / deceleration rate of the line along which the steel sheet is transported is Z, and a set value of the line speed at which the opening operation of the roll unit pressing down the steel sheet is started is α, The control device, A set value α is determined according to the value of Z×Y / X, and when the current line speed reaches the set value α, an opening operation of the roll unit is started; When the yield strength of the steel plate is within a predetermined range, the value of Z×Y / X is determined as the set value α; When the yield strength of the steel plate is higher than the predetermined range, a value smaller than the value of Z×Y / X is determined as the set value α. Manufacturing method of steel plate.

2. The control device, When the conveyance of the steel sheet is stopped, an opening operation of the roll unit is started based on a current line speed and the set value α; When the conveyance of the steel sheet is resumed, a pressing operation of the steel sheet by the roll unit is started so that the pressing amount becomes a preset pressing amount Y. A method for producing the steel sheet according to claim 1.

3. A steel plate manufacturing facility including a roll unit arranged in a conveying direction of the steel plate and correcting a shape of the steel plate, and a control device, When the opening / reduction lifting speed of the roll unit with respect to the steel sheet is X, the pushing amount of the steel sheet by the roll unit is Y, the acceleration / deceleration rate of the line along which the steel sheet is transported is Z, and a set value of the line speed at which the opening operation of the roll unit pressing down the steel sheet is started is α, The control device includes: A set value α is determined according to the value of Z×Y / X, and when the current line speed reaches the set value α, an opening operation of the roll unit is started; When the yield strength of the steel plate is within a predetermined range, the value of Z×Y / X is determined as the set value α; When the yield strength of the steel plate is higher than the predetermined range, a value smaller than the value of Z×Y / X is determined as the set value α. Steel plate manufacturing equipment.

4. The control device When the conveyance of the steel sheet is stopped, an opening operation of the roll unit is started based on a current line speed and the set value α; When the conveyance of the steel sheet is resumed, a pressing operation of the steel sheet by the roll unit is started so that the pressing amount becomes a preset pressing amount Y. A manufacturing facility for the steel sheet according to claim 3.

Images