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; and a friction coefficient difference providing part which provides a friction coefficient difference to a friction coefficient of one of the cradle rolls against the coil and a friction coefficient of the other cradle roll against the coil. The friction coefficient difference providing part sets the friction coefficient of the one cradle roll to 5 to 70% of the friction coefficient of the other cradle roll.SELECTED DRAWING: Figure 6

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 controlling the friction state between the coil and the cradle roll is effective in suppressing the rotation of the coil about the vertical axis, which is the trigger for the coil slippage.

[0015] The present invention is a coil unwinding device having a coil crown, comprising a pair of cradle rolls that load the coil and unwind the coil, and a friction coefficient difference imparting unit that imparts a friction coefficient difference between the friction coefficient of one of the cradle rolls relative to the coil and the friction coefficient of the other cradle roll relative to the coil, and is characterized in that the friction coefficient difference imparting unit makes the friction coefficient of one of the cradle rolls 5 to 70% of the friction coefficient of the other cradle roll.

[0016] The friction coefficient difference imparting section may be configured to provide a surface roughness difference between one of the cradle rolls and the other of the cradle rolls.

[0017] The friction coefficient difference imparting section may include a lubricant supplying device that supplies a lubricant to one or both of the cradle rolls.

[0018] The friction coefficient difference imparting unit may make the friction coefficient of the cradle roll located upstream in the rotation direction of the coil smaller than the friction coefficient of the cradle roll located downstream.

[0019] The present invention also provides a method for unwinding a coil having a coil crown, characterized in that the coil is loaded onto a pair of cradle rolls that unwind the coil, and the coefficient of friction of one of the cradle rolls relative to the coil is set to 5 to 70% of the coefficient of friction of the other cradle roll relative to the coil.

[0020] The unwinding may be performed by making the coefficient of friction of the cradle roll located upstream relative to the direction of rotation of the coil smaller than the coefficient of friction of the cradle roll located downstream. [Effects of the Invention]

[0021] 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]

[0022] [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] 1 is a schematic explanatory diagram of a coil unwinding device according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0023] 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.

[0024] <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.

[0025] 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.

[0026] 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.

[0027] <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).

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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).

[0035] In the coil positioner 20 having the above configuration, the positive side in the Z direction is the work side (WS), and the negative side in the Z direction is the drive side (DS). The configuration of the coil unwinding device 10 (coil positioner 20) described above is a basic configuration, and it may include components with various other functions. For example, it may include lubricant supply devices 40a, 40b (not shown in FIGS. 1 and 2) for lubricating between the cradle rolls 30a, 30b and the coil C, as described below.

[0036] <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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] <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.

[0041] 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.

[0042] (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.

[0043] 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.

[0044] 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).

[0045] 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.

[0046] (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.

[0047] 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).

[0048] (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.

[0049] 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).

[0050] 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.

[0051] 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.

[0052] <Method for preventing coil misalignment> In the present invention, (1) we focus on the coil misalignment caused by the coil crown of the coil C and suppress the coil misalignment. As described above, the presence of the coil crown reduces the contact area between the coil C and each of the cradle rolls 30a, 30b. This weakens the constraint on the coil by the cradle rolls 30a, 30b, causing the coil C to rotate around the Y axis, increasing the skew of the coil C and accelerating the coil misalignment.

[0053] Therefore, the inventors studied ways to strengthen the restraining force of the coil C by the cradle rolls 30a, 30b, and came up with the idea of ​​controlling the friction state between each of the pair of cradle rolls 30a, 30b and the coil C, thereby suppressing the skew of the coil C.

[0054] In order to change the force acting on the coil C from the cradle rolls 30a, 30b, it is sufficient to appropriately adjust the coefficient of friction of each cradle roll 30a, 30b with respect to the coil C. When the coil C is unwound, frictional force is generated between the cradle rolls 30a, 30b and the coil C due to minute irregularities present on the surfaces of the cradle rolls 30a, 30b. In order to adjust this frictional force, the coefficient of friction of each cradle roll 30a, 30b with respect to the coil C is adjusted, thereby controlling the magnitude of the frictional force acting on the coil C from each cradle roll 30a, 30b. This changes the relative slip between the cradle rolls 30a, 30b, thereby suppressing skew of the coil C and thereby suppressing coil misalignment.

[0055] Based on the above-mentioned idea, the present inventors performed an FEM analysis to verify how to control the coefficient of friction of each of the cradle rolls 30a, 30b with respect to the coil C. As a result, they discovered that it would be sufficient to provide a difference in the coefficient of friction (friction coefficient difference) between the coil C of the two cradle rolls 30a and 30b while maintaining the rotation direction of each of the cradle rolls 30a, 30b in the same direction. As an example, the coefficient of friction of one cradle roll with respect to the coil C may be set to 5 to 70% of the coefficient of friction of the other cradle roll when unwinding the coil C.

[0056] If the coefficient of friction of one cradle roll with respect to coil C is more than 70% of the coefficient of friction of the other cradle roll, the degree of force acting on coil C from each of the pair of cradle rolls 30a, 30b does not change significantly, and skew of coil C cannot be sufficiently suppressed, making it impossible to suppress coil misalignment that occurs in coil C. By setting the coefficient of friction of one cradle roll with respect to coil C to 70% or less of the coefficient of friction of the other cradle roll, it is possible to sufficiently change the degree of force acting on coil C from each of the pair of cradle rolls 30a, 30b, and sufficiently suppress skew of coil C. As a result, it is possible to suppress coil misalignment that occurs in coil C.

[0057] The coefficient of friction of one cradle roll with respect to the coil C is preferably smaller than the coefficient of friction of the other cradle roll, and may be preferably 60% or less, more preferably 50% or less.

[0058] On the other hand, in a pair of cradle rolls 30a, 30b, it may be difficult to make the friction coefficient of one cradle roll with respect to the coil C less than 5% of the friction coefficient of the other cradle roll by only processing, lubrication, and surface materials for the cradle rolls, as described below.

[0059] Furthermore, when providing a difference in the coefficient of friction between the pair of cradle rolls 30a, 30b as described above, there is no particular restriction as to which cradle roll should have a higher (lower) coefficient of friction. However, as shown in the following verification example, it is more preferable to make the coefficient of friction of the cradle roll located upstream in the direction of rotation of the coil C (i.e., the upstream cradle roll 30a) smaller than the coefficient of friction of the cradle roll located downstream (i.e., the downstream cradle roll 30b). This makes it possible to further suppress the occurrence of coil misalignment of the coil C.

[0060] <Friction coefficient difference applying section> In the pair of cradle rolls 30a, 30b, any means may be used to impart a difference in the friction coefficient (friction coefficient difference) between the coils C of the two cradle rolls 30a, 30b. An example of the friction coefficient difference imparting unit will be described below.

[0061] (Cradle roll processing) By changing the surface roughness of one or both of the cradle rolls 30a and 30b, a difference in surface roughness can be created between them. That is, a difference can be created in the coefficient of friction between the coils C of the two cradle rolls 30a and 30b. Any means can be used to change the roll surface roughness, and examples include machining, polishing, thermal spraying, shot blasting, electrical discharge texturing, and laser texturing.

[0062] Here, the parameter representing the surface roughness of the cradle rolls 30a, 30b may be "arithmetic mean roughness" Ra. For example, when unwinding the same coil C during operation, Ra may be reduced only in the upstream cradle roll 30 to create a difference in the coefficient of friction between the coil C on the two cradle rolls 30a and 30b.

[0063] (Lubrication for cradle rolls) Furthermore, by lubricating either one or both of the cradle rolls 30a and 30b, a difference in the coefficient of friction between the coils C of the two cradle rolls 30a and 30b can be created. Any means of lubrication can be used, and examples of lubricants include lubricating oil and solid lubricants. Examples of lubricating oil include oil only, emulsion-type lubricating oil, and air-atomized lubricating oil. Examples of solid lubricants include oils, fats, mica, and salt. Furthermore, sand may be supplied as a means of increasing the coefficient of friction.

[0064] The lubrication of the cradle rolls 30a, 30b may be performed continuously when the coil C is unwound, or may be performed intermittently as long as the lubricating effect continues.

[0065] Fig. 6 is a perspective view showing an outline of the configuration of the coil unwinding device 10 according to this embodiment, which is equipped with a lubricant supply device for changing the coefficient of friction between the cradle rolls 30a, 30b and the coil C. As shown in Fig. 6, the coil unwinding device 10 according to this embodiment is equipped with lubricant supply devices 40a, 40b that can supply lubricant to one or both of the two cradle rolls 30a and 30b.

[0066] The lubricant supplying devices 40a, 40b may have any configuration. For example, when supplying a liquid lubricant, they may have nozzles or injection ports that inject the lubricant onto the circumferential surfaces of the cradle rolls 30a, 30b. Furthermore, the lubricant supplying devices 40a, 40b may include a control unit (not shown) that controls the amount, timing, and duration of lubricant supply.

[0067] (Cradle roll surface material) Furthermore, by changing the surface material of each of the cradle rolls 30a and 30b, it is possible to create a difference in the coefficient of friction between the coils C on the two cradle rolls 30a and 30b. The material of the rolls is arbitrary, and for example, the cradle roll located on the upstream side may be a cast iron roll and the cradle roll located on the downstream side may be a urethane-lined roll, thereby creating a difference in the coefficient of friction between the coils C on the two cradle rolls 30a and 30b.

[0068] <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.

[0069] 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.

[0070] In the coil unwinding method according to this embodiment, when the coil is unwound as described above, the coefficient of friction between one of the pair of cradle rolls 30a, 30b and the coil C is set to 10 to 70% of the coefficient of friction between the other cradle roll and the coil C. This changes the degree of force applied to the coil C from each cradle roll 30a, 30b, and the constraint of the coil C by each cradle roll 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 cradle roll 30a, 30b. As a result, axial movement of the coil C is suppressed, and coil misalignment can be suppressed.

[0071] In this case, as mentioned earlier, it is more preferable to make the friction coefficient of the cradle roll 30a located upstream in the rotation direction of the coil C smaller than the friction coefficient of the cradle roll 30b located downstream.

[0072] 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.

[0073] <Action and effect> According to the above embodiment, even if there is a misalignment in the parallelism of the cradle rolls 30a and 30b when unwinding the coil C, by imparting a difference in the friction coefficient between the coil C on the two cradle rolls 30a and 30b, it is possible to suppress the rotation and skew of the coil C about the Y-axis caused by the coil crown of the coil C, and to suppress the coil misalignment.

[0074] 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.

[0075] 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]

[0076] 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 6.

[0077] In this test, the maximum coil misalignment was measured when 20 m of each of ten coils with outer diameters of 1.2 m to 2.0 m and widths of 1.0 m to 1.6 m was unwound. The diameter of each cradle roll was 350 mm, the roll width (body length) was 1 m, and the distance between the axes of the WS side of the pair of cradle rolls was 830 mm. In this case, the 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 on the pair of cradle rolls. The coil crown of a 1.5 m wide coil was measured to be 3 mm.

[0078] In this verification, the conditions of Comparative Example 1 were used as the basic conditions, and the case where the friction coefficient between both coils of the pair of cradle rolls was reduced was used as Comparative Example 2. Then, under each of the conditions of Examples 1 to 7, the friction coefficient between one of the cradle rolls and the coil was fixed, and the friction coefficient between the other cradle roll and the coil was changed to perform the verification.

[0079] The distance between the axes of the WS end of the pair of cradle rolls was 4 mm larger than the distance between the axes of the DS end of the pair of cradle rolls. In other words, the pair of cradle rolls were arranged non-parallel (in a V-shape), causing parallelism misalignment.

[0080] The conditions for the friction coefficient and the amount of coil displacement in Comparative Examples 1 and 2 and Examples 1 to 7 are as shown in Table 1 below.

[0081] [Table 1]

[0082] As shown in Table 1, it is possible to reduce the amount of coil slippage by fixing the coefficient of friction between one of the cradle rolls and the coil and reducing the coefficient of friction between the other cradle roll and the coil. For example, when comparing Comparative Example 1 with any of Examples 1 to 7, the amount of coil slippage is smaller in Examples 1 to 7.

[0083] Furthermore, in Comparative Example 2, the coefficient of friction between the coil and both of the inlet and outlet cradle rolls was reduced by 0.05 compared to Comparative Example 1, resulting in a smaller amount of coil slippage. On the other hand, in Examples 2 and 5, the coefficient of friction between only one of the cradle rolls and the coil was reduced by 0.05, resulting in a smaller amount of coil slippage compared to Comparative Example 2. In other words, even when the friction coefficient is reduced by the same amount, it is clear that the amount of coil slippage can be reduced by reducing the coefficient of friction between the coil and one of the cradle rolls rather than both cradle rolls.

[0084] In addition, in Examples 1 to 3 or Examples 4 to 6, the coefficient of friction between one cradle roll and the coil is set to 70 to 10% of the coefficient of friction between the other cradle roll and the coil. As shown in Table 1, the lower the coefficient of friction between either one of the cradle rolls and the coil, the more effective it is in suppressing the amount of coil misalignment.

[0085] Furthermore, when Examples 1 to 3 are compared with Examples 4 to 6, even if the friction coefficient is reduced by the same amount, the amount of coil slippage is smaller when the friction coefficient between the inlet cradle roll and coil is reduced than when the friction coefficient between the outlet cradle roll and coil is reduced. Furthermore, in Example 7, the friction coefficient between one cradle roll and coil is set to 5% of the friction coefficient between the other cradle roll and coil, and it was confirmed that the amount of coil slippage was also suppressed in this case.

[0086] From the above verification, it was confirmed that the amount of coil misalignment can be suppressed by controlling the friction state between the coil and the cradle roll in a pair of cradle rolls. [Industrial Applicability]

[0087] The present invention is useful when unwinding a coil using a pair of cradle rolls. [Explanation of symbols]

[0088] 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 40a, 40b Lubricant supply device 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 that load the coil and unwind the coil; a friction coefficient difference imparting unit that imparts a friction coefficient difference between the friction coefficient of one of the cradle rolls relative to the coil and the friction coefficient of the other cradle roll relative to the coil, A coil unwinding device, characterized in that the friction coefficient difference imparting unit sets the friction coefficient of one of the cradle rolls to 5 to 70% of the friction coefficient of the other cradle roll.

2. The coil unwinding device according to claim 1, characterized in that the friction coefficient difference imparting section provides a difference in surface roughness between one of the cradle rolls and the other of the cradle rolls.

3. The coil unwinding device according to claim 1, characterized in that the friction coefficient difference imparting unit comprises a lubricant supplying device that supplies a lubricant to one or both of the cradle rolls.

4. The coil unwinding device according to any one of claims 1 to 3, characterized in that the friction coefficient difference imparting unit makes the friction coefficient of the cradle roll located upstream in the rotation direction of the coil smaller than the friction coefficient of the cradle roll located downstream.

5. 1. A method for unwinding a coil having a coil crown, comprising: A coil unwinding method characterized in that the coil is loaded onto a pair of cradle rolls, and the unwinding is performed by setting the coefficient of friction of one of the cradle rolls against the coil to 5 to 70% of the coefficient of friction of the other cradle roll against the coil.

6. 6. A coil unwinding method as described in claim 5, characterized in that unwinding is performed by making the friction coefficient of the cradle roll located upstream in the direction of rotation of the coil smaller than the friction coefficient of the cradle roll located downstream.

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