Uncoiling device and uncoiling method

Abstract

To provide an uncoiling device which can inhibit coil deviation when uncoiling a coil with a pair of cradle rolls, and to provide an uncoiling method.SOLUTION: An uncoiling device for a coil having a coil crown, includes a pair of cradle rolls which uncoils the coil placed thereon. In the paired cradle rolls, a surface roughness of any one of the cradle rolls is set to be not smaller than 36 μm and not larger than 100 μm when represented by a maximum height Ry and be not smaller than 9 μm and not larger than 25 μm when represented by an arithmetic mean roughness.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a coil unwinding device and a coil unwinding method using a pair of cradle rolls. [Background technology]

[0002] In a continuous processing line for steel strips (strip steel sheets), a coiled steel strip is discharged by a payoff reel, and the steel strip is continuously subjected to predetermined processing. In order to stably perform such continuous processing of steel strips, it is important to properly unwind the coil and discharge the steel strip. Therefore, various methods have been devised for unwinding the coil.

[0003] For example, in the coil unwinding method disclosed in Patent Document 1, an opener is used to open the tip of a coil attached to a payoff reel. At this time, a pressure roll, which is used to prevent bending of the unwound steel strip, is used to straighten the curl of the tip of the coil opened by the opener.

[0004] Also, for example, in the coil unwinding method disclosed in Patent Document 2, a pressure roll is used to straighten the curl of the tip of the coil that has been unwound by an opener, similar to the method disclosed in Patent Document 1. Furthermore, in the method disclosed in Patent Document 2, after unwrapping the tip of the coil, the opener moves away from the payoff reel in synchronization with the feed speed of the coil caused by the rotation of the payoff reel.

[0005] In addition, for example, in a steel strip unwinding device disclosed in Patent Document 3, after the outer periphery of the coil is pressed by a pressure roll, the pressure of the pressure roll is reduced to bring side guides into contact with both widthwise ends of the steel strip, and the steel strip is paid out from the pay-off reel. In such a case, the upward displacement of the steel strip is regulated by the pressure roll, and the widthwise displacement is regulated by the side guide, thereby stabilizing the running state of the steel strip paid out from the pay-off reel. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5212191 [Patent Document 2] Patent No. 5435121 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-266121 Summary of the Invention [Problem to be solved by the invention]

[0007] In a continuous processing line, the steel strip is usually paid off from the coil by a pay-off reel as described above, but when unwinding the coil, in order to shorten the handling time and improve throughput, the tip of the coil may be paid off before the coil is inserted into the pay-off reel. Specifically, the coil is loaded on a pair of rolls (hereinafter referred to as "cradle rolls"), and the cradle rolls are rotated to rotate the coil and unwind it.

[0008] In such cases, the rotation of the coil can cause a skew (a slight cross) between the coil and the cradle roll. This skew can then cause the coil to move axially due to the thrust force. If the coil moves and shifts on the cradle roll, it can become difficult to insert the coil into the payoff reel. Furthermore, the coil may fall over on the cradle roll, potentially causing damage to the equipment.

[0009] The main cause of coil misalignment is a faulty cradle roll equipment. However, due to its nature, faulty cradle roll equipment is difficult to correct. The causes of coil misalignment will be described in detail later.

[0010] Furthermore, in order to suppress coil slippage, it is sufficient to reduce the amount of coil rotation; however, depending on the arrangement of equipment in the continuous processing line, restrictions are imposed on the amount of steel strip discharged from the tip of the coil, and there are limits to controlling the amount of coil rotation. For example, when the distance between the coil and the equipment upstream of the continuous processing line is large, it is difficult to suppress the amount of coil rotation. In other words, suppressing coil slippage poses a potential problem in that it also leads to restrictions on the configuration of the continuous processing line.

[0011] It should be noted that all of the methods disclosed in Patent Documents 1 to 3 relate to methods for unwinding a coil inserted into a payoff reel, and are not methods for unwinding a coil before inserting it into a payoff reel. Therefore, Patent Documents 1 to 3 do not address the problem of coil misalignment on the cradle roll, and naturally do not mention any method for solving this problem.

[0012] The present invention has been made in consideration of these points, and aims to provide a coil unwinding device and a coil unwinding method that can suppress coil misalignment when unwinding a coil using a pair of cradle rolls. [Means for solving the problem]

[0013] As mentioned above, the mechanism by which coil misalignment occurs on the cradle roll is that the coil moves due to the thrust force caused by the skew between the coil and the cradle roll. However, the inventors further investigated the causes of coil misalignment and found that the influence of coil crown is significant. The presence of coil crown causes the coil and cradle roll to come into near-point contact (almost the same as one-point contact, but with a contact area that is slightly larger than the one-point contact point), reducing the contact area. This weakens the constraint on the coil by the cradle roll, causing the coil to rotate around its vertical axis (horizontal rotation), increasing the coil skew and accelerating coil misalignment.

[0014] Therefore, the present inventors have come to the knowledge that in order to suppress the rotation of the coil about the vertical axis, which may cause the coil to slip, it is effective to quantitatively control the surface roughness of the pair of cradle rolls 30a, 30b and set it within a suitable range.

[0015] According to one aspect of the present invention, there is provided an apparatus for unwinding a coil having a coil crown, comprising a pair of cradle rolls for loading the coil and unwinding the coil, wherein the surface roughness of at least one of the pair of cradle rolls is set to 36 μm or more and 100 μm or less when expressed in terms of maximum height Ry, and 9 μm or more and 25 μm or less when expressed in terms of arithmetic mean roughness Ra.

[0016] In the coil unwinding device, the surface profile of at least one of the pair of cradle rolls is measured and frequency analysis is performed, and the surface roughness of the cradle roll may be configured so that the wave height of the lowest frequency in the surface profile is 32 μm or more and 100 μm or less.

[0017] In the coil unwinding device, when the surface roughness of at least one of the pair of cradle rolls is expressed by a maximum height Ry, the surface profile of at least one of the cradle rolls may be configured so that the angle θ formed by the wave pitch at the maximum height Ry is 4 degrees or more and 23 degrees or less.

[0018] In the coil unwinding device, the range in which the specified surface roughness is imparted to the pair of cradle rolls may be a range of ±200 mm or less in the width direction from the center of installation of the coil on the cradle rolls.

[0019] According to another aspect of the present invention, there is provided a method for unwinding a coil having a coil crown, which comprises measuring the surface roughness of a predetermined range of the surface profile of at least one of a pair of cradle rolls on which the coil is loaded and unwinded at a maximum height Ry, determining that the roughness is normal if it is 40 to 100 μm, caution if it is 36 to 40 μm, and danger if it is less than 36 μm, and carrying out repairs. [Effects of the Invention]

[0020] According to the present invention, by controlling the friction coefficients between a pair of cradle rolls and the coil to be different from each other, it is possible to suppress the thrust force caused by the skew between the coil and the cradle roll, and to suppress the coil misalignment on the cradle roll. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is an explanatory diagram showing an outline of the configuration of a continuous processing line. [Figure 2] FIG. 1 is a perspective view showing an outline of the basic configuration of a coil unwinding device (coil positioner). [Figure 3] FIG. 10 is a graph showing the relationship between the coil crown amount and the coil misalignment amount. [Figure 4] FIG. 10 is a diagram illustrating parallelism misalignment of the cradle roll. [Figure 5] FIG. 10 is a diagram illustrating horizontal misalignment of a cradle roll. [Figure 6] FIG. 1 is a schematic diagram showing an example of a surface profile to be verified in a cradle roll. [Figure 7] 10 is a graph showing an example of surface displacement used in frequency analysis. [Figure 8] 10 is a graph showing the results of frequency analysis. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0023] <Configuration of continuous processing line> First, the configuration of a continuous processing line in which a coil unwinding device according to this embodiment is implemented will be described with reference to Figure 1. In this embodiment, a case will be described in which the continuous processing line 1 is a cold rolling line, as an example. In the continuous processing line 1, a coil C produced in a hot rolling process is unwound, and a steel strip S is delivered, and predetermined processes such as welding and rolling are continuously performed on the steel strip S.

[0024] Fig. 1 is an explanatory diagram showing the outline of the configuration of a continuous processing line 1. As shown in Fig. 1, the continuous processing line 1 is equipped with a coil unwinding device 10, deflector rolls 11, pinch rolls 12, a leveler 13, and a welding machine 14. Note that the continuous processing line 1 is further equipped with devices such as a rolling mill downstream of the welding machine 14 in the conveying direction, but for the sake of explanation, Fig. 1 does not show the entire continuous processing line 1, but shows the configuration from the coil unwinding device 10 to the welding machine 14.

[0025] The coil unwinding device 10 unwinds the coil C and delivers the steel strip S toward the welding machine 14. The deflector roll 11 changes the direction of the steel strip S so that the steel strip S delivered from the coil C is transported to the welding machine 14. The pinch rolls 12 are provided as a pair, one above the other, and sandwich the steel strip S between them to transport it to the welding machine 14. The leveler 13 has a plurality of work rolls arranged in a staggered pattern above and below along the transport direction of the steel strip S, and corrects the shape of the steel strip S. The welding machine 14 welds the rear end of the preceding steel strip S to the front end of the following steel strip S.

[0026] <Basic configuration of coil unwinding device> Next, the basic configuration of the coil unwinding device 10 will be described with reference to Figures 1 and 2. Figure 2 is a perspective view showing an outline of the basic configuration of part of the coil unwinding device 10 (coil positioner 20).

[0027] The coil unwinding device 10 is provided with a coil positioner 20 that loads the coil C and moves it to a predetermined position, and a payoff reel 21 that pays off the steel strip S from the coil C.

[0028] The coil positioner 20 is configured to be able to move the coil C horizontally and vertically, and moves the coil C sequentially to a coil receiving position P1, a leading edge feeding position P2, and a payoff reel insertion position P3. The coil positioner 20 includes cradle rolls 30a, 30b, stands 31a, 31b, motors 32a, 32b, and a moving frame 33.

[0029] Each cradle roll 30a, 30b extends in the Z direction and is arranged side by side in the X direction. That is, the pair of cradle rolls 30a, 30b is arranged substantially parallel. Each cradle roll 30a, 30b is arranged horizontally. Each cradle roll 30a, 30b is configured to be able to load a coil C so that the axial direction of the coil C faces the Z direction. Each cradle roll 30a, 30b is configured to be rotatable, and the coil C is rotated to unwind. In the example shown in FIG. 2, the cradle rolls 30a, 30b are rotated counterclockwise, and the coil C is rotated clockwise.

[0030] In the following description, the cradle roll 30a on the upstream side (entry side) of the rotation direction of the coil C (unwinding direction of the coil C) is referred to as the upstream cradle roll 30a, and the cradle roll 30b on the downstream side (exit side) of the rotation direction of the coil C is referred to as the downstream cradle roll 30b. In the example shown in Fig. 2, the rotation direction of the coil C is clockwise, the upstream cradle roll 30a is disposed on the positive side of the X direction, and the downstream cradle roll 30b is disposed on the negative side of the X direction.

[0031] The base 31a supports the upstream cradle roll 30a. The base 31a may have any configuration. For example, the base 31a supports both ends of the central axis 34a of the upstream cradle roll 30a in the X direction, is disposed below the upstream cradle roll 30a with a gap therebetween, and extends in the Z direction. The base 31b has a similar configuration to the base 31a, and supports the central shaft 34b of the downstream cradle roll 30b.

[0032] The motor 32a is provided below the upstream cradle roll 30a and on the negative Z-direction side of the stand 31a. The motor 32a rotates the upstream cradle roll 30a via a gear (not shown). The motor 32b has a configuration similar to that of the motor 32a, and is provided below the downstream cradle roll 30b and on the negative Z-direction side of the base 31b. The motor 32b rotates the downstream cradle roll 30b.

[0033] The moving frame 33 supports the mounts 31a and 31b. The moving frame 33 is configured to be movable in the horizontal and vertical directions by a moving mechanism (not shown).

[0034] In the coil positioner 20 having the above configuration, the positive Z-direction side is the working side (WS: work side), and the negative Z-direction side is the driving side (DS: drive side). The configuration of the coil unwinding device 10 (coil positioner 20) described above is a basic configuration, and may include components with various other functions.

[0035] <Continuous processing method> In the continuous processing line 1 having the above-described configuration, first, at the coil receiving position P1, the coil C is delivered to the coil positioner 20 and loaded onto the pair of cradle rolls 30a, 30b.

[0036] Next, the coil positioner 20 is moved to the leading end feed position P2. At the leading end feed position P2, the pair of cradle rolls 30a, 30b are rotated to rotate the coil C. As a result, the coil C is unwound and the leading end of the steel strip S is paid out.

[0037] The steel strip S unwound from the coil C passes through a deflector roll 11, a pinch roll 12, and a leveler 13, and is transported to a welding machine 14. In the welding machine 14, the leading end of the steel strip S is welded to the trailing end of the preceding steel strip S.

[0038] In the welding machine 14, while the rear end of the preceding steel strip S is being welded to the front end of the following steel strip S (the paid-out steel strip S), the coil positioner 20 is moved to the pay-off reel insertion position P3. At the pay-off reel insertion position P3, the pay-off reel 21 is inserted into the coil C by a moving mechanism (not shown). Thereafter, the steel strip S is paid out from the coil C inserted into the pay-off reel 21.

[0039] <Mechanism of coil misalignment> In the coil unwinding device 10 of the continuous processing line 1, from the time when unwinding of the coil C begins at the leading end feed position P2 until the payoff reel 21 is inserted into the coil C at the payoff reel insertion position P3, the coil C loaded on the pair of cradle rolls 30a, 30b moves approximately in the Z direction, which may cause coil misalignment on the cradle rolls 30a, 30b. The mechanism of coil misalignment will be explained below.

[0040] The main causes of the coil misalignment include (1) the coil crown of the coil C, (2) misalignment in parallelism of the cradle rolls 30a and 30b, and (3) misalignment in horizontality of the cradle rolls 30a and 30b.

[0041] (1) Coil crown of coil C The coil C transported to the continuous processing line 1, which is a cold rolling line, was previously produced in a hot rolling process. In the hot rolling process, when a steel plate is rolled with a rolling roll, the rolling roll undergoes elastic deformation, causing the thickness of the steel plate to increase in the center of the width direction and decrease at both ends. When the steel plate rolled in this way is wound into a coil, the plate crown of the steel plate overlaps, giving the coil C an outer shape like a barrel, with the coil diameter increasing in the center of the width direction and decreasing at both ends. The difference between the coil radius of this coil C at the center and the coil radius at the ends is the coil crown.

[0042] If the coil C has a coil crown, the coil C and the upstream cradle roll 30a will be in approximately point contact, reducing the contact area, and the coil C and the downstream cradle roll 30b will be in approximately point contact, reducing the contact area. This weakens the restraint of the coil C by the cradle rolls 30a and 30b. Furthermore, depending on the parallelism and horizontality of the cradle rolls 30a and 30b (described later) and the method of loading the coil C onto the cradle rolls 30a and 30b, the axial direction of the coil C may be tilted relative to the axial direction of each cradle roll 30a and 30b (hereinafter referred to as "coil tilt"). This coil tilt creates a difference in peripheral speed between the coil C and the upstream cradle roll 30a and also between the coil C and the downstream cradle roll 30b. In other words, relative slip occurs due to the difference in diameter between the contact surfaces caused by the coil crown, generating a rotational moment around the Y-axis in the coil C. Furthermore, because the restraint of the coil C by the cradle rolls 30a and 30b is weak, the coil C becomes more rotatable.

[0043] When the rotation moment is generated, the coil C moves, resulting in a skew (slight cross) between the coil C and each of the cradle rolls 30a and 30b. Then, the thrust force caused by this skew moves the coil C in the axial direction (approximately the Z direction).

[0044] The inventors conducted an FEM analysis to verify the influence of coil misalignment due to coil crown. In this analysis, the parallelism (described below) of the cradle rolls 30a and 30b was set to 4 mm and the horizontality (described below) was set to 0 (zero) mm as equipment-related disturbances that could cause coil misalignment. Figure 3 shows the results of this analysis, showing the relationship between the amount of coil crown (horizontal axis) and the amount of coil misalignment (vertical axis). Referring to Figure 3, when there was no coil crown, almost no coil misalignment occurred. In contrast, as the amount of coil crown increased, the amount of coil misalignment increased. It is presumed that the reason for the increased coil misalignment when there was coil crown is the geometric constraint of the coil C by the cradle rolls 30a and 30b, as described above. As described above, it was verified that coil misalignment occurs due to coil crown.

[0045] (2) Parallelism misalignment of the cradle rolls 30a and 30b Typically, the cradle rolls 30a and 30b are arranged parallel to one another. However, due to equipment design issues, there is a certain degree of error, and the arrangement of the cradle rolls 30a and 30b is not completely parallel. That is, as shown in FIG. 4, the center-to-center distance Lws in the X direction on the positive Z-direction side (WS side) of the cradle rolls 30a and 30b is different from the center-to-center distance Lds in the X direction on the negative Z-direction side (DS side) of the cradle rolls 30a and 30b. In the example of FIG. 4, the center-to-center distance Lws is greater than the center-to-center distance Lds, and the cradle rolls 30a and 30b are arranged in a V-shape in plan view. In the following description, the absolute value of the difference between the center-to-center distance Lws on the WS side of the cradle rolls 30a and 30b and the center-to-center distance Lds on the DS side is referred to as parallelism (=|Lws - Lds|). The state in which the cradle rolls 30a, 30b are parallel to each other and are not parallel to each other is called parallelism misalignment.

[0046] If there is misalignment in the parallelism of the cradle rolls 30a, 30b, skew occurs between the coil C and the cradle rolls 30a, 30b, and the thrust force caused by this skew generates a rotational moment about the Y axis in the coil C. When this rotational moment occurs, the skew between the coil C and the cradle rolls 30a, 30b is further accelerated, and the thrust force also increases. Then, the thrust force caused by this skew causes the coil C to move in the axial direction (approximately the Z direction).

[0047] (3) Horizontal misalignment of the cradle rolls 30a and 30b Typically, the cradle rolls 30a, 30b are arranged horizontally. However, due to equipment design issues, there is a certain degree of error, and the arrangement of the cradle rolls 30a, 30b is not completely horizontal. That is, as shown in FIG. 5 , with a horizontal axis passing through the center of the width direction of the upstream cradle roll 30a as a reference, there is a vertical distance Hws in the Y direction from the horizontal on the positive Z-direction side (WS side) of the upstream cradle roll 30a, and there is also a vertical distance Hds in the Y direction from the horizontal on the negative Z-direction side (DS side) of the upstream cradle roll 30a. In the following description, the absolute value of the difference between the vertical distance Hws on the WS side of the upstream cradle roll 30a and the vertical distance Hds on the DS side is referred to as the horizontality (=|Hws-Hds|). Similarly, for the downstream cradle roll 30b, the absolute value of the difference between the vertical distance Hws on the WS side and the vertical distance Hds on the DS side is referred to as the horizontality. Furthermore, the state in which the cradle rolls 30a and 30b are not horizontal is called horizontal misalignment.

[0048] If there is misalignment in the horizontality of each of the cradle rolls 30a, 30b, the thrust force due to gravity will cause the coil C to move in the axial direction (approximately in the Z direction).

[0049] As described above, the main causes of coil misalignment include (1) the coil crown of the coil C, (2) misalignment in parallelism of the cradle rolls 30a and 30b, and (3) misalignment in horizontality of the cradle rolls 30a and 30b. Analysis by the present inventors has revealed that the amount of coil misalignment caused by (3) misalignment in horizontality of the cradle rolls 30a and 30b is extremely small compared to the amount of coil misalignment caused by (1) the coil crown of the coil C and (2) misalignment in parallelism of the cradle rolls 30a and 30b.

[0050] Therefore, in the present invention, the following factors are considered to cause coil misalignment: (1) the coil crown of the coil C and (2) the parallelism misalignment of the cradle rolls 30a, 30b. Note that (1) the coil crown of the coil C inevitably occurs in the pre-treatment hot rolling process. Furthermore, errors in the equipment design of the cradle rolls 30a, 30b cannot be avoided, and (2) the parallelism misalignment of the cradle rolls 30a, 30b also inevitably occurs. Moreover, since the parallelism of the cradle rolls 30a, 30b increases during operation due to wear and tear on the equipment, it is difficult to control in terms of productivity and work efficiency.

[0051] <Method for preventing coil misalignment> In the present invention, (2) we focus on coil misalignment caused by misalignment in the parallelism of the cradle rolls 30a, 30b and suppress the coil misalignment. As described above, if there is misalignment in the parallelism of the cradle rolls 30a, 30b, skew occurs between the coil C and the cradle rolls 30a, 30b, and the thrust force caused by this skew generates a rotational moment about the Y axis in the coil C. When this rotational moment is generated, the skew between the coil C and the cradle rolls 30a, 30b is accelerated, and the thrust force also increases. As a result, the thrust force caused by this skew causes the coil C to move in the axial direction (approximately the Z direction).

[0052] Therefore, the inventors have studied methods for strengthening the restraining force of the coil C by the cradle rolls 30a, 30b, and have specified specific conditions for quantitatively controlling the surface roughness of the pair of cradle rolls 30a, 30b and suppressing the skew of the coil C.

[0053] (Surface roughness control by Ry and Ra) According to the inventor's investigations, it was found that coil slippage can be suppressed by increasing the roughness of the cradle rolls 30a, 30b at the stage when coil slippage begins. It was also found that when controlling the roughness of the cradle rolls 30a, 30b to suppress coil slippage, it is preferable to control it using the arithmetic mean roughness Ra and the maximum height Ry, that the influence of geometric friction when the coil surface bites into the coil C is greater than that of dynamic Coulomb friction, and that the range of surface roughness to be controlled and imparted should be within a predetermined range of the cradle rolls 30a, 30b. Regarding the roughness control of the cradle rolls 30a, 30b, the definitions of the arithmetic mean roughness Ra and the maximum height Ry are based on JIS B0601.

[0054] Based on the above idea, the inventors performed FEM analysis to examine the relationship between the surface roughness of each cradle roll 30a, 30b and the displacement of the coil C. That is, in each of the cradle rolls 30a, 30b, roughness was imparted to the surface to affect the geometric friction force, and the conditions required for the profile were examined. Figure 6 is a schematic diagram showing an example of the surface profile examined for each of the cradle rolls 30a, 30b, where (a) shows the surface before roughness was imparted, and (b) shows the surface after roughness was imparted. The surface roughness can be imparted by any method, such as thermal spraying or shot blasting.

[0055] In the surface profile shown in FIG. 6(a), Ra is 6 to 8 μm, and the maximum height is Ry=30 μm. In this case, the analysis results showed that coil misalignment occurred. On the other hand, in the surface profile shown in FIG. 6(b), Ra is 10 to 12 μm, and the maximum height is Ry=60 μm. In this case, the analysis results showed that coil misalignment did not occur. From these results, it is preferable that the surface roughness of the cradle rolls 30a, 30b according to this embodiment is 9 μm or more and 12 μm or less, expressed as arithmetic mean roughness Ra. However, from the results of the examples described later, it may also be 9 μm or more and 25 μm or less.

[0056] Furthermore, the roughness of the surface profile that can suppress coil displacement is 36 μm or more and 100 μm or less in terms of maximum height Ry. More preferably, it may be 40 μm or more and 100 μm or less. This numerical range is determined based on the results of the examples described below.

[0057] (Surface roughness control through frequency analysis) When roughness is imparted to each cradle roll 30a, 30b, if the surface profile has periodicity, a frequency analysis may be performed to determine the range of suitable roughness based on the smallest low frequency, i.e., the wave height of the largest wave pitch. Figure 7 is a graph showing an example of the surface displacement used in the frequency analysis, and Figure 8 is a graph showing the results of the frequency analysis.

[0058] As shown in Figure 8, by measuring the surface displacement of the cradle roll and performing frequency analysis, the wave pitch and amplitude of the roughness can be determined. From the results shown in Figure 8, it can be seen that the peak amplitude is 100 μm (= 0.1 mm) and the wave pitch of the largest wave is 1 mm. In this way, if the surface profile is periodic, frequency analysis can be performed and the upper and lower limits of the wave height of the surface roughness can be designed based on the value of the wave pitch of the lowest frequency (largest wave). As an example, the surface profile of the cradle roll can be measured and frequency analysis can be performed to set the wave height of the lowest frequency (largest wave) to be between 32 μm and 100 μm.

[0059] (The angle between the wave height and the wave pitch when the maximum height Ry is used) As described above, the preferred range of surface profile roughness for suppressing coil displacement, expressed in terms of maximum height Ry, is 36 μm or more and 100 μm or less. The inventors focused on the angle θ formed by the wave pitch at the maximum height Ry and also investigated the preferred conditions for this angle θ.

[0060] When the wave pitch is 1000 μm at 36 μm, which is the lower limit of the maximum height Ry, the angle θ formed by the wave pitch at the maximum height Ry is given by the following formula (1). θ=tan -1 {36 / (1000 / 2)}=4.1deg ···(1) Furthermore, when the wave pitch is 1000 μm at the upper limit of the maximum height Ry of 100 μm, the angle θ formed by the wave pitch at the maximum height Ry is given by the following formula (2). θ=tan -1 {100 / (1000 / 2)}=11.3deg ···(2) That is, the angle θ formed by the wave pitch at the maximum height Ry may be set to be equal to or greater than 4.1 degrees and equal to or less than 11.3 degrees.

[0061] Furthermore, the measured values ​​of the surface profile shown in Figure 6(b) show that the maximum height Ry was 100 μm when the arithmetic mean roughness Ra was 12 μm. Therefore, based on the upper limit of the arithmetic mean roughness Ra, which is 25 μm, the upper limit of the maximum height Ry can be assumed to be 100 × 25 / 12 ≒ 208 μm, and the upper limit of the angle θ formed by the wave pitch at the maximum height Ry can be determined as shown in the following formula (3). θ=tan -1 {208 / (1000 / 2)}=22.5deg ···(3) That is, the angle θ formed by the wave pitch at the maximum height Ry may be set to 4.1 degrees or more and 22.5 degrees or less. For easier management, the angle θ formed by the wave pitch at the maximum height Ry may be set to 4 degrees or more and 23 degrees or less.

[0062] <Roughness range> As described above, the coil C has a coil crown, and it is known that the coil C and each cradle roll 30a, 30b are in approximately point contact with each other, resulting in a small contact area. From this perspective, when roughness is imparted to each cradle roll 30a, 30b, the range may be within ±200 mm or less in the width direction (Z direction in FIG. 2) from the center position of the coil C installed on the cradle rolls 30a, 30b. The contact width between the cradle rolls 30a, 30b and the coil C is, for example, 50 mm to 100 mm, or ±25 mm to 50 mm from the center position of the coil C. Furthermore, when the coil C is loaded on the cradle rolls 30a, 30b, the respective center positions may not coincide. Therefore, the above range of ±200 mm or less may be determined by adding ±150 mm as a tolerance for deviation to ±25 mm to 50 mm.

[0063] In addition, when imparting roughness to the surfaces of a pair of cradle rolls 30a, 30b as described above, there is no particular requirement as to which cradle roll surface should be roughened, and it is sufficient to impart a predetermined roughness to the surface of at least one of the cradle rolls.

[0064] (How to unwind the coil) As shown in FIG. 1, in the coil unwinding device 10, first, at the coil receiving position P1, the coil C is delivered to the coil positioner 20 and loaded onto a pair of cradle rolls 30a, 30b.

[0065] Next, the coil positioner 20 is moved to the leading end feed position P2. At the leading end feed position P2, the pair of cradle rolls 30a, 30b are rotated to rotate the coil C. As a result, the coil C is unwound and the leading end of the steel strip S is paid out.

[0066] In the coil unwinding method according to this embodiment, when a coil is unwound as described above, the surface roughness of at least one of the pair of cradle rolls 30a, 30b is measured and controlled to fall within the preferred range. For example, the surface roughness of the pair of cradle rolls 30a, 30b within a predetermined range is measured using the maximum height Ry. If it is 40 to 100 μm, it is determined to be "normal (GOOD)," if it is 36 to 40 μm, it is determined to be "causation (CAUSION)," and if it is less than 36 μm, it is determined to be "danger (DANGER)." The cradle rolls 30a, 30b may be repaired as necessary. If it is determined to be "normal (GOOD)," repair of the cradle rolls 30a, 30b is generally not required. If it is determined to be "causation (CAUSION)," an operator checks the condition of the cradle rolls 30a, 30b and determines whether repair is necessary. If it is determined to be "danger (DANGER)," repair of the cradle rolls 30a, 30b is generally required. This changes the degree of force acting on the coil C from each of the cradle rolls 30a, 30b, and the restraint of the coil C by each of the cradle rolls 30a, 30b becomes stronger. This suppresses rotation of the coil C about the Y axis, and reduces the thrust force caused by the skew between the coil C and each of the cradle rolls 30a, 30b. As a result, axial movement of the coil C can be suppressed, and coil misalignment can be suppressed.

[0067] Next, the coil positioner 20 is moved to the payoff reel insertion position P3. At the payoff reel insertion position P3, the payoff reel 21 is inserted into the coil C by a moving mechanism (not shown). Thereafter, the steel strip S is paid out from the coil C inserted into the payoff reel 21.

[0068] <Action and effect> According to the above embodiment, even if there is a misalignment in the parallelism of the cradle rolls 30a, 30b when unwinding the coil C, the surface roughness of at least one of the pair of cradle rolls 30a, 30b is measured and managed to be within the above-mentioned suitable range during unwinding, thereby suppressing rotation and skew of the coil C around the Y-axis caused by the coil crown of the coil C and suppressing coil misalignment.

[0069] While one embodiment of the present invention has been described above, the present invention is not limited to the illustrated embodiment. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0070] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects. [Example]

[0071] An experiment was conducted to verify the coil misalignment suppression effect of the present invention. This verification was carried out using a coil loaded on a pair of cradle rolls, similar to the coil positioner shown in Figure 2.

[0072] In this verification, the amount of coil misalignment (lateral misalignment) was measured when a 20-meter coil with an outer diameter of 1.2 to 2.0 meters and a width of 1.0 to 1.6 meters was unwound. The diameter of each cradle roll was 350 mm, the roll width (body length) was 1 meter, and the distance between the axes of the cradle rolls on the WS side was 830 mm. The amount of coil misalignment was measured as the absolute value of the amount of axial movement of the coil from the position of the coil when it was loaded onto the pair of cradle rolls. The coil crown of a 1.5-meter-wide coil was measured to be 3 mm. The allowable value for coil misalignment can be set arbitrarily depending on the operating conditions; for example, it can be set to 50 mm or less.

[0073] Example 1 In Example 1, within a predetermined range of each cradle roll (a range of ±200 mm or less in the width direction from the center position of the coil installation), the maximum height Ry was used as a parameter, and the roughness shown in Table 1 below was imparted to the surface, and unwinding was performed, and the amount of coil deviation (lateral deviation) was measured.

[0074] [Table 1]

[0075] As shown in Table 1, when the maximum height Ry of the roughness imparted to the cradle roll surface was 36 μm or more and 100 μm or less, the amount of coil slippage was kept low at 14 mm to 9 mm. On the other hand, when the maximum height Ry was 20 μm, the amount of coil slippage increased to 100 mm, and when the maximum height Ry was 120 μm, scratches occurred on the coil. From these results, the preferred range of the roughness of the surface profile of the cradle roll that can suppress coil slippage, expressed in terms of maximum height Ry, is determined to be 36 μm or more and 100 μm or less.

[0076] Similarly, using the arithmetic mean roughness Ra as a parameter, the roughness shown in Table 2 below was imparted to the surface, the coil was unwound, and the amount of coil misalignment (lateral misalignment) was measured.

[0077] [Table 2]

[0078] As shown in Table 2, when the arithmetic mean roughness Ra of the roughness imparted to the cradle roll surface was 9 μm or more and 25 μm or less, the amount of coil slippage was kept low at 14 mm to 9 mm. On the other hand, when the arithmetic mean roughness Ra was 5 μm, the amount of coil slippage increased to 100 mm, and when the arithmetic mean roughness Ra was 120 μm, scratches occurred on the coil. From these results, the suitable range of the roughness of the surface profile of the cradle roll that can suppress coil slippage is determined to be 9 μm or more and 25 μm or less, expressed in arithmetic mean roughness Ra.

[0079] Example 2 In Example 2, the surface profile was measured within a predetermined range of each cradle roll (a range of ±200 mm or less in the width direction from the center position of the coil installation), and the wave height of the lowest frequency (largest wave) obtained by frequency analysis was used as a parameter to impart the roughness shown in Table 3 below to the surface, and the roll was unwound and the amount of coil slippage (lateral slippage) was measured.

[0080] [Table 3]

[0081] As shown in Table 3, the coil misalignment amount tends to decrease as the wave height of the lowest frequency (largest wave) obtained by measuring the surface profile of the cradle roll and performing frequency analysis increases. However, when the wave height was 20 μm, the coil misalignment amount was 35 mm, which was a large value, although it was within the acceptable range. Furthermore, when the wave height was 120 μm, scratches occurred on the coil. Based on these results, the preferred range for the wave height of the lowest frequency (largest wave) obtained by measuring the surface profile and performing frequency analysis may be 32 μm or more and 100 μm or less.

[0082] Example 3 In Example 3, in a predetermined range of each cradle roll (a range of ±200 mm or less in the width direction from the center position of the coil installation), the surface profile was measured and frequency analysis was performed. When the wave height of the lowest frequency (largest wave) was 95 μm, the angle θ formed by the wave pitch at the maximum height Ry was used as a parameter to impart the roughness shown in Table 4 below to the surface, and the coil was unwound, and the amount of coil slippage (lateral slippage) was measured.

[0083] [Table 4]

[0084] As shown in Table 4, the larger the angle θ formed by the wave pitch at the maximum height Ry, the smaller the amount of coil misalignment tends to be. However, when the angle θ was 2°, the amount of coil misalignment was 25 mm, which was a large value, although it was within the acceptable range. Furthermore, when the angle θ was 25°, it was found that processing to impart roughness to the cradle roll was difficult and the roll life was short. From these results, the preferable range of the angle θ formed by the wave pitch at the maximum height Ry may be 4° or more and 23° or less.

[0085] From the above verification, it was confirmed that the amount of coil misalignment can be suppressed by quantitatively controlling the surface roughness of a pair of cradle rolls and setting it within a suitable range. [Industrial Applicability]

[0086] The present invention is useful when unwinding a coil using a pair of cradle rolls. [Explanation of symbols]

[0087] 1 Continuous processing line 10 Coil unwinding device 11 Deflector roll 12 Pinch Roll 13 Leveller 14 Welding machine 20 Coil Positioner 21 Payoff Reel 30a Upstream cradle roll 30b Downstream cradle roll 31a, 31b Mounting stand 32a, 32b motor 33 Moving Frame 34a, 34b center axis C coil P1 Coil receiving position P2 Lead edge feed position P3 Payoff reel insertion position S steel strip

Claims

1. 1. An unwinding device for a coil having a coil crown, comprising: a pair of cradle rolls for loading the coil and unwinding the coil; A coil unwinding device, characterized in that the surface roughness of at least one of the pair of cradle rolls is set to 36 μm or more and 100 μm or less when expressed in maximum height Ry, and to 9 μm or more and 25 μm or less when expressed in arithmetic mean roughness Ra.

2. The coil unwinding device according to claim 1, characterized in that the surface profile of at least one of the pair of cradle rolls is measured and frequency analysis is performed, and the surface roughness of the cradle roll is configured so that the wave height of the lowest frequency in the surface profile is 32 μm or more and 100 μm or less.

3. 2. The coil unwinding device according to claim 1, wherein, when the surface roughness of at least one of the cradle rolls in the pair is expressed by a maximum height Ry, the surface profile of at least one of the cradle rolls is configured such that an angle θ formed by a wave pitch at the maximum height Ry is 4 degrees or more and 23 degrees or less.

4. The coil unwinding device according to any one of claims 1 to 3, characterized in that the range in which the predetermined surface roughness is imparted to the pair of cradle rolls is a range of ±200 mm or less in the width direction from the installation center of the coil on the cradle rolls.

5. 1. A method for unwinding a coil having a coil crown, comprising: A pair of cradle rolls on which the coil is loaded and unwound, A coil unwinding method characterized by measuring the surface roughness in a predetermined range of the surface profile of at least one of the cradle rolls at a maximum height Ry, determining that it is normal if it is 40 to 100 μm, caution if it is 36 to 40 μm, and danger if it is less than 36 μm, and carrying out repairs.

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