Roller grinding pass / fail judgment device, roll grinding pass / fail judgment method, and metal strip rolling method

Abstract

The device for determining whether roller grinding is acceptable or not according to the present invention comprises: a vibration meter data acquisition unit, which uses a vibration meter installed in the roller grinder to acquire vibration meter data when the roller is ground using the roller grinder; a vibration information acquisition unit, which acquires vibration information during roller grinding by frequency analysis of the vibration meter data; a spectrum upper limit setting unit, which sets a specific frequency band and a spectrum upper limit value determined based on the usage method in the rolling mill using the roller; and a grinding acceptance determination unit, which determines whether the roller grinding is acceptable or not based on the spectrum value in the specific frequency band of the vibration information and the spectrum upper limit value.

Description

Technical Field

[0001] The present invention relates to a device for determining whether the grinding of a rolling mill is qualified or not, a method for determining whether the grinding of a rolling mill is qualified or not, and a method for rolling a metal strip. Background Art

[0002] Metal strips, such as steel sheets, used in automobiles and beverage cans, undergo continuous casting, hot rolling, and cold rolling before undergoing annealing and electroplating to become finished products. The cold rolling process is the final step, determining the thickness of the finished metal strip. In recent years, the thickness of the electroplating has been reduced. The surface properties of the metal strip before electroplating can affect the surface properties of the finished product after electroplating, leading to an increasing need to prevent surface defects.

[0003] One of the surface defects that occurs during the cold rolling process is chatter marks. These are linear marks that appear in the width direction of the metal strip, and are surface defects that appear periodically in the length direction of the metal strip. Chatter marks occur due to the vibration of the rolling mill (hereinafter referred to as chatter). Very mild chatter marks are sometimes not detected during visual inspection or plate thickness measurement after the cold rolling process, but are first detected after the electroplating process. Therefore, a large number of surface defects that occur during this process are not noticed, resulting in a decrease in the product yield and becoming a major factor that seriously hinders productivity. In addition, it is also known that in thin materials such as can steel plates and electromagnetic steel plates, due to the rapid changes in the thickness and tension of the metal strip caused by chatter, problems such as metal strip breakage sometimes occur, which hinders productivity.

[0004] Against this backdrop, methods for suppressing chatter have been proposed. For example, Patent Document 1 describes a method in which a vibration detector is installed in a rolling mill to collect vibration information during rolling. Furthermore, the method obtains rolling operation parameters such as rolling load and interstand tension, and then analyzes these frequencies to determine the occurrence of chatter. Patent Document 1 also describes a method in which the natural vibration frequency of the rolling mill and inherent vibration frequencies caused by bearing defects and roll defects are pre-identified, and the cause of chatter marks is determined by comparing these frequencies with the vibration information during rolling.

[0005] Meanwhile, while not specifically targeting chatter vibration, Patent Document 2 describes a method for detecting roll chatter (Japanese: ビビリマーク) in a roll grinding device using a vibration sensor installed at least on the grinding stone table. Frequency analysis is used to calculate the vibration value level, and the value is compared with a predetermined threshold value to detect roll chatter. In this context, roll chatter is a type of grinding defect, a periodic, pattern-like defect that develops on the roll surface. Chatter can be visually identified by applying a thin layer of chalk to the ground roll. Furthermore, chatter is transferred to the metal strip as rolling progresses.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 2964887

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 11-77532 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] However, the method described in Patent Document 1 cannot detect the occurrence of vibration unless abnormal vibration of a certain magnitude occurs. Therefore, with the method described in Patent Document 1, chatter marks have already formed on a portion of the metal strip by the time chatter vibration is detected, resulting in a reduction in product yield. Meanwhile, chatter marks, while not detectable visually or by chalk application during roll grinding, differ from chatter marks in that they become apparent during the cold rolling process due to mill vibration. Therefore, even if chatter marks are detected during roll grinding to determine the quality of the rolls, the method described in Patent Document 2 cannot prevent the occurrence of chatter marks during rolling.

[0012] The present invention has been completed in view of the above-mentioned problems, and its object is to provide a grinding acceptance determination device and grinding acceptance determination method for a roll that can suppress the occurrence of chatter marks during metal strip rolling. Furthermore, another object of the present invention is to provide a metal strip rolling method that can suppress the occurrence of chatter marks during metal strip rolling, thereby improving the metal strip manufacturing yield.

[0013] Means for solving problems

[0014] The device for determining whether the grinding of a rolling mill roll according to the present invention comprises: a vibration meter data acquisition unit, which uses a vibration meter installed in a roll grinder to acquire vibration meter data when the roll grinder is used to grind the rolling mill roll; a vibration information acquisition unit, which acquires vibration information when the rolling mill roll is ground by frequency analysis of the vibration meter data; a spectrum upper limit setting unit, which sets a specific frequency band and a spectrum upper limit value determined based on the usage method in the rolling mill using the rolling mill roll; and a grinding compliance determination unit, which determines whether the grinding of the rolling mill roll is satisfactory based on the spectrum value in the specific frequency band of the vibration information and the spectrum upper limit value.

[0015] The vibration information during the roll grinding acquired by the vibration information acquisition unit may be vibration information of one or more grinding passes selected from among the grinding passes in the rough grinding process of the roll.

[0016] The spectrum upper limit setting unit may set the specific frequency band based on a chattering frequency of a rolling mill using the rolls.

[0017] The method for determining whether the grinding of a rolling mill is qualified or not according to the present invention includes: a vibration meter data acquisition step, which uses a vibration meter installed in a roller grinder to obtain vibration meter data when the roller is ground using the roller grinder; a vibration information acquisition step, which obtains vibration information when the roller is ground by frequency analysis of the above-mentioned vibration meter data; a spectrum upper limit setting step, which sets a specific frequency band and a spectrum upper limit value determined based on the usage method in the rolling mill using the above-mentioned roller; and a grinding qualified or not determination step, which determines whether the grinding of the above-mentioned rolling mill is qualified or not based on the spectrum value in the above-mentioned specific frequency band of the above-mentioned vibration information and the above-mentioned spectrum upper limit value.

[0018] The vibration information during the roll grinding acquired in the vibration information acquisition step may be vibration information of one or more grinding passes selected from the grinding passes in the rough grinding process of the roll.

[0019] The grinding stone cutting depth per grinding pass in the rough grinding step may be 30 to 200 μm.

[0020] The current value of the grindstone rotating motor in the rough grinding step may be 1.0 to 1.6 A per 1 mm of the grindstone width.

[0021] The frequency spectrum upper limit setting step may include the step of setting the specific frequency band based on a chattering frequency of a rolling mill using the rolls.

[0022] The rolling mill may be the final stand of a tandem rolling mill or a stand upstream of the final stand, and the rolls may be backup rolls of the rolling mill.

[0023] The metal strip rolling method according to the present invention includes: a roll determination step, which uses the roll grinding qualification judgment method according to the present invention to determine the rolls installed on the rolling mill; and a rolling step, which uses the rolling mill equipped with the rolls determined by the aforementioned roll determination step to roll the metal strip.

[0024] Effects of the Invention

[0025] According to the present invention, a device and method for determining the grinding quality of a roll that can suppress chatter marks during metal strip rolling can be provided. Furthermore, according to the present invention, a method for rolling a metal strip can be provided that can suppress chatter marks during metal strip rolling, thereby improving the metal strip manufacturing yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a diagram showing the configuration of a roll grinding machine as one embodiment of the present invention.

[0027] Figure 2 This is a diagram showing the configuration of a roll grinding acceptance determination device according to one embodiment of the present invention.

[0028] Figure 3 This is a diagram showing an example of vibration information during roll grinding.

[0029] Figure 4 This is a diagram showing an example of the current value of the grindstone rotating motor when a grindstone having a grindstone width of 100 mm is used for roll grinding.

[0030] Figure 5 This is a diagram showing the configuration of a rolling mill using rolls in which grinding is performed using a grinding device according to one embodiment of the present invention. DETAILED DESCRIPTION

[0031] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0032] The abnormal vibration of the rolling mill during the cold rolling process of the metal strip is called chattering, and the periodic pattern formed on the surface of the metal strip due to chattering is called chatter mark. In this embodiment, the chatter marks with an amplitude of about 0.5 to 10 μm formed on the surface of the metal strip are treated as the object of treatment. They are mostly caused by the thickness fluctuation of the metal strip. Such chatter marks with tiny uneven surfaces are mostly difficult to detect by the thickness gauge installed on the exit side of the cold rolling mill. In addition, the surface of the metal strip after cold rolling is also difficult to judge by visual observation. Such mild chatter marks are mostly detected after surface treatment such as electroplating, or are first detected after the metal strip is press-formed.

[0033] Until now, it was generally believed that the chattering vibration that causes chatter marks is caused by the shaking of the bearings, meshing of gears, couplings, etc. that constitute the rolling mill. In this case, the vibration data obtained from the vibration meter installed in the rolling mill is analyzed, and when the magnitude of the vibration in a specific frequency band is greater than a pre-set threshold value, the chattering vibration can be detected. However, the inventors of the present application discovered that one of the causes of chatter marks is caused by the grinding of the rolls. In addition, it was discovered that the grinding state of the rolls by the roll grinder before the rolls are installed in the rolling mill causes tiny bumps on the surface of the rolls. If such rolls are used for the cold rolling process, the vibration of the rolling mill will be increased by combining with specific rolling conditions. The present invention was completed based on this discovery.

[0034] It should be noted that this can be considered to be a result of some unevenness occurring on the rolls during roll grinding. However, unlike chatter marks, which are roll grinding defects that can be identified visually, chatter marks differ from roll chatter marks in that they are caused by a combination of unevenness caused by roll grinding and the rolling mill or rolling conditions in which the rolls are used. Furthermore, chatter marks are a defect caused by the transfer of the roll pattern onto the surface of the metal strip being rolled, so they target defects encountered during grinding of work rolls that come into direct contact with the metal strip. In contrast, chatter marks are caused by vibrations that occur while the rolls are mounted in the rolling mill, so the focus is on unevenness during grinding of heavy backup rolls or intermediate rolls.

[0035] Roller grinding machine

[0036] Figure 1 1 is a diagram showing the structure of a roller grinding machine as one embodiment of the present invention. Figure 1 As shown, the roll grinder used in this embodiment is configured using a cylindrical grinding stone. After being used in the rolling mill, the rolls 1 used in the roll grinder are transported to the roll shop using a crane or other means. The rolls 1 are then removed from the bearing housing, cooled to room temperature by natural cooling, and then placed one by one in the roll grinder.

[0037] The roll grinding machine includes: a grinding head 3 that supports a grinding stone 2; a biaxial table 4 that drives the grinding head 3 to move in the axial direction and approach direction of the roll 1; and a roll supporting device (roll chuck 5, roll rotation motor 6, tailstock 7, support 8) that supports the roll 1 and rotates it.

[0038] The roll support device includes a roll chuck 5 that supports the roll 1 from one axial end; a roll rotation motor 6 that rotates the roll 1 at a predetermined rotational speed; a tailstock 7 that supports the roll 1 from the other axial end; and a support 8 that supports the roll 1 with its neck. The tailstock 7 aligns the axis of the roll 1 with the axis of the rotation shaft of the roll rotation motor 6. The portion of the tailstock 7 that contacts the roll 1 is conical in shape, and the tip of the cone is pressed into a countersink or a countersink of a fixture at the center of the axial end of the roll 1, allowing the seat position to be finely adjusted to extend the core. The rotational speed of the roll 1 during grinding is controlled by a controller 23 for controlling the roll grinder.

[0039] The dual-axis table 4 is constructed to move on guides 9a and 9b. The table 4 moves laterally along guides 9a, which are arranged parallel to the axial direction of the roll 1. Furthermore, the grinding stone 2 moves perpendicularly to the axis of the roll 1 along guides 9b. The movement of the dual-axis table 4 along guides 9a and 9b is controlled by a servo motor, thereby controlling the grinding position and depth of the grinding stone 2. During grinding, the roll 1 is ground from one axial end toward the other, and then from the other end toward one. This reciprocating motion of the grinding stone 2 is called a traverse. The typical grinding process is divided into rough grinding, which involves a large grinding depth, and fine grinding, which involves finishing the surface of the roll 1. Generally speaking, the number of traverses for rough grinding is about 80 to 150 times, and the number of traverses for fine grinding is about 5 to 15 times.

[0040] Here, rough grinding is a grinding process that removes the surface of the roll 1 by cutting to remove the fatigue layer and micro cracks. On the other hand, finish grinding is a weak grinding process for adjusting the surface roughness of the roll to a predetermined range.

[0041] The grinding head 3 supports the grinding stone 2, the grinding stone rotation motor 10, and the pulley 11 and conveyor belt 12 that transmit the grinding power. However, the grinding stone 2 may be directly rotated by the grinding stone rotation motor 10, rather than by the pulley 11 and conveyor belt 12. The grinding stone cut-in amount refers to the distance between the surface of the roller 1 during grinding and the axial center of the grinding stone 2, based on the contact state between the roller 1 and the grinding stone 2 before each transverse movement. However, it is sometimes difficult to detect the contact between the grinding stone 2 and the roller 1 using sensors or the like. Therefore, during the initial grinding (first transverse movement) of the rough grinding process or the fine grinding process, the operator confirms the contact state between the grinding stone 2 and the roller 1, and in subsequent transverse movements, the current consumption value of the grinding stone rotation motor 10 is sometimes set to the same grinding conditions as the current consumption value during the first transverse movement. Alternatively, grinding may be performed by using the current consumption value of the grindstone rotating motor 10 as a set value without using the grindstone cutting depth.

[0042] The grinding stone's penetration is controlled by controlling the position of the grinding stone 2 using an NC unit employing a servo motor. Generally, the greater the grinding stone's penetration, the greater the amount of grinding per traverse, thus shortening the time required for roller grinding. On the other hand, when the grinding stone's penetration is large, the load on the grinding stone rotation motor 10 becomes excessive, sometimes causing pattern-like defects on the surface of the roll 1. Furthermore, a dressing device for the grinding stone 2 is sometimes attached to the grinding head 3. This device restores the sharpness of the grinding stone 2 by bringing the abrasive grains forming the surface of the grinding stone 2 into contact with diamond or other materials.

[0043] Here, in Figure 1 The roll grinding machine shown is equipped with a roll grinding machine control computer 21. The roll grinding machine control computer 21 obtains information related to the roll 1's usage status in the rolling mill, such as the dimensional information of the roll 1 to be ground, the grinding amount, and the target surface finish roughness value, from a business computer 22, which serves as a host computer. The computer sets the grinding conditions for the roll grinding machine and transmits the information to the roll grinding machine control controller 23.

[0044] The grinding conditions of a roller grinder include at least three settings: the roller rotation speed during grinding, the grinding stone rotation speed, and the grinding stone penetration (or the set current value of the grinding stone rotation motor 10). These settings are set for each traverse from rough grinding to finish grinding. However, these roller grinder grinding conditions are sometimes appropriately modified by the operator while confirming the grinding state of the roll 1. In this case, the modified roller grinder grinding conditions are transmitted to the roller grinder control computer 21. Furthermore, when setting the aforementioned operating conditions as grinding conditions for the roller grinder, a setting table is sometimes provided that takes into account factors such as the diameter of the roll 1 being ground, the surface hardness, and the surface roughness before grinding. On the other hand, the grinding conditions for the grinding stone 2 include factors such as the grit size of the grinding stone 2, the grinding stone diameter (initial grinding stone diameter, current grinding stone diameter), the accumulated grinding time of the grinding stone 2, and the total grinding distance (total grinding distance) after dressing by the dressing device.

[0045] Here, the initial grindstone diameter refers to the grindstone diameter of the grinding stone 2 after it is manufactured and before it is first used in roller grinding. The current grindstone diameter refers to the grindstone diameter measured before grinding the roller 1 being ground. The grindstone diameter is measured using a micrometer at multiple locations on the outer periphery of the grinding stone 2. Alternatively, the grindstone diameter can be determined by pre-marking the side of the grinding stone 2 with radial spacing of 1 to 5 mm and reading the grindstone diameter from these markings. The grinding stone 2 is discarded when its initial grindstone diameter is approximately 850 to 950 mm and its outer diameter is approximately 450 to 600 mm.

[0046] The control controller 23 of the roller grinder controls each machine in the following manner: relative to the control target value of the operating condition of the roller grinder set by the control computer 21 of the roller grinder, the roller speed during grinding, the grinding stone speed and the grinding stone penetration amount (or the current value of the grinding stone rotation motor 10) for each traverse from the start of grinding to the end of grinding are made the control target value. In addition, the control controller 23 of the roller grinder obtains the actual value of the motor current value of the grinding stone 2 when driving the grinding. It should be noted that when the actual values ​​of the roller speed, grinding stone speed and grinding stone penetration amount during grinding can be measured, the control controller 23 of the roller grinder obtains their actual values. The data thus obtained are sent to the control computer 21 of the roller grinder as data for analyzing the operating status of the roller grinding. It should be noted that, Figure 1 The roller grinding machine control computer 21 and the roller grinding machine control controller 23 may be configured by a single control computer.

[0047] Table 1 shows an example comparing the grinding conditions of the rough grinding process and the fine grinding process in roller grinding. The rough grinding process has 80 to 150 grinding passes from start to finish, while the fine grinding process has 1 to 20 grinding passes from start to finish. The fine grinding process is a grinding process used to adjust the surface roughness of the roller, so the number of grinding passes can be small. The set value of the grinding stone cutting depth per grinding pass is 30 to 200 μm in the rough grinding process and 1 to 29 μm in the fine grinding process. This is based on the following difference: the rough grinding process aims to remove the surface of the roller and adjust the surface profile to the target shape, while the fine grinding process aims to adjust the surface roughness. Furthermore, the feed speed of the grinding stone in the longitudinal direction of the roll during the grinding passes is 500 to 1000 mm / min during the rough grinding process and 100 to 300 mm / min during the finish grinding process. Thus, in the finish grinding process, grinding is performed at a low feed speed to adjust the surface roughness and prevent grinding defects such as chatter. It should be noted that the rotational speed and peripheral speed of the grinding stone are set to approximately the same values ​​in both the rough and finish grinding processes.

[0048] Table 1

[0049]

[0050] On the other hand, the difference in grinding conditions between the rough grinding step and the finish grinding step can be determined by the current value of the grindstone rotating motor. Figure 4 The figure shows an example of the current value of the grindstone rotating motor when a grindstone with a grindstone width of 100 mm is used for roller grinding. This example shows the actual measured value of the current value of the grindstone rotating motor when the grinding passes of the rough grinding process are set to 80 traverses and the grinding passes of the fine grinding process are set to 15 traverses. It should be noted that the curve in the figure shows the average value of the current value for each traverse. Figure 4 As shown in the figure, during the rough grinding process, while the current value tends to decrease slightly with each grinding pass, there is almost no significant change in the current value throughout the rough grinding process. In contrast, during the finish grinding process, the current value decreases with each grinding pass, and the current value is roughly halved between the start and end of the finish grinding process. This is because the finish grinding process aims to adjust the surface roughness, so the grinding conditions are gradually reduced towards the final pass to prevent the occurrence of grinding defects such as chatter.

[0051] In the grinding process described above, the roll 1, having completed finish grinding, is moved to the finished roll storage area and returned to the roll changing device in order to be installed in the rolling mill. Furthermore, the roll grinder of this embodiment includes a vibration meter 13. The vibration meter 13 can be installed at any location that can measure vibrations during grinding. However, it is preferably installed at either the grinding head 3 or the roll support device. It is more preferably installed near the grinding stone 2 of the grinding head 3 of the roll grinder. This is because it facilitates the detection of vibrations occurring at the contact point between the grinding stone 2 and the roll 1.

[0052] [Roll grinding qualification determination device]

[0053] Figure 2 This is a block diagram illustrating the configuration of a roll grinding acceptance determination device according to one embodiment of the present invention. The roll grinding acceptance determination device of this embodiment determines the acceptance of the grinding condition of the roll 1 after the roll 1 has been ground by a roll grinder or during the grinding process. This acceptance determination determines whether the ground roll 1 is suitable for installation in a rolling mill to roll a metal strip.

[0054] like Figure 2 As shown, the roll grinding pass / failure determination device 31 of this embodiment includes a vibration meter data acquisition unit 31a that acquires vibration data acquired by the vibration meter 13; a vibration information acquisition unit 31b that converts the acquired vibration meter data into vibration information; a spectrum upper limit setting unit 31c that sets a specific frequency band and a spectrum upper limit value based on the usage of the roll 1 in the rolling mill; and a grinding pass / failure determination unit 31d that determines the grinding pass / failure of the roll 1. The roll grinding pass / failure determination device 31 determines the spectrum value in the specific frequency band from the vibration information acquired by the vibration information acquisition unit 31b and compares it with the spectrum upper limit value set by the spectrum upper limit setting unit 31c to determine the grinding pass / failure of the roll 1.

[0055] Here, the roll grinding acceptance determination device 31 can be realized by a processing device such as a personal computer or a workstation, and has, for example, a CPU, a ROM, and a RAM as main components.

[0056] 〔Vibration meter data acquisition unit〕

[0057] The vibrometer data acquisition unit 31a acquires vibration data from the vibrometer 13 installed in the roller grinder. The signal detected by the vibrometer 13 is vibration displacement, vibration velocity, or vibration acceleration. Vibration displacement can be calculated by integrating the vibration velocity over time, and vibration velocity can be calculated by integrating the vibration acceleration over time. Therefore, the output of the vibrometer 13 can be any signal, which is converted into appropriate vibration information in the vibration information acquisition unit 31b described below.

[0058] The sampling frequency of the signal detected by the vibrometer 13 is 100 Hz or more, preferably 400 Hz or more. More preferably, it is 1000 Hz or more. For example, when the vibration acceleration of the grinding head 3 is obtained as the signal detected by the vibrometer 13, the data collected by the vibrometer 13 is the acceleration data of the time series obtained at the above sampling frequency. In order to remove the noise of the acceleration data of the time series obtained from the vibrometer 13, the vibrometer data acquisition unit 31a performs averaging processing on the vibration acceleration every specified data time (for example, 1.0 second). This is the function of the vibrometer data acquisition unit 31a. It should be noted that for the above sampling frequency and data specific time, even when the signal detected by the vibrometer 13 is vibration displacement or vibration velocity, it can be obtained under the same conditions.

[0059] 〔Vibration Information Acquisition Unit〕

[0060] The vibration information acquisition unit 31b converts the time-series data from the vibrometer 13, after being averaged in the vibrometer data acquisition unit 31a, into vibration information representing the relationship between spectral values. These spectral values ​​represent the vibration frequency and its intensity during roller grinding. For example, when the vibrometer 13 is collecting vibration acceleration data and vibration velocity is used as vibration information, the vibration information acquisition unit 31b performs a time-integration on the averaged time-series vibration acceleration data from the vibrometer 13 to convert it into time-series vibration velocity data. The vibration information acquisition unit 31b then performs a high-speed Fourier transform frequency analysis on the converted time-series vibration velocity data to obtain the frequency components contained in the vibration signal and their spectral values ​​as vibration information during roller grinding.

[0061] It should be noted that vibration information obtained by processing the vibration displacement using the same method instead of the vibration velocity can also be used as vibration information during the grinding of the roll 1. The vibration displacement can be calculated by integrating the vibration velocity over time. The calculated vibration displacement can be Fourier transformed to obtain the frequency components and their spectral values, which can be used as vibration information during the grinding of the roll 1. Alternatively, the vibration acceleration obtained through measurement can be used directly. In this case, the relationship between the frequency components and their spectral values ​​obtained by Fourier transforming the acceleration data collected by the vibration meter data acquisition unit 31a can be used. Figure 3 This figure shows an example of vibration information during roll grinding obtained by frequency-analyzing time-series data of vibration acceleration.

[0062] In the present embodiment, with respect to the vibration information obtained as described above during the grinding of the roll 1, it is particularly preferred to use the vibration information of the roll 1 during the grinding of 5 to 10 lateral shifts (grinding passes) before the end of the rough grinding process. In addition, it is preferred to set one or more grinding passes selected from the rough grinding process and use the vibration information in the set grinding passes. However, it is also possible to set multiple grinding passes of the rough grinding process and use the average value of the vibration information in these grinding passes. Fine grinding is a process for final adjustment of the surface roughness of the roll 1. This is because most of the micro-concave and convex parts formed on the surface of the roll 1 have been formed at the time when the rough grinding process is roughly completed, and the micro-concave and convex parts imparted in the rough grinding process affect the occurrence of chatter during rolling. As described above, the vibration information of the roll 1 during grinding obtained by the vibration information acquisition unit 31b is sent to the grinding pass / fail judgment unit 31d.

[0063] 〔Spectrum upper limit setting unit〕

[0064] The spectrum upper limit setting unit 31c sets a specific frequency band and spectrum upper limit value based on the usage of the roll 1 in the rolling mill. Here, "usage in the rolling mill" refers to the way the roll 1 is installed in the rolling mill and used for rolling, and includes information on the roll type and the applicable stand. The roll type distinguishes whether the roll 1 is a work roll or a backup roll, and refers to the distinction based on the function or configuration when used in the stand. It should be noted that in the case of a six-high rolling mill, intermediate rolls can also be added as a distinction. Furthermore, it is also possible to distinguish between top and bottom rolls. This is because the degree of influence on the occurrence of chatter varies depending on where the roll 1 is used within the rolling mill stand.

[0065] On the other hand, the application stand refers to the stand used in a tandem mill. Stands can be identified by stand numbers. Generally, chatter is more likely to occur in the subsequent stands, and the degree of impact on chatter varies depending on the application stand. Furthermore, information related to the mill's usage may include information such as the planned rolling cycle for the grinding roll 1. This is because the rolling cycle includes information that can distinguish the type of metal strip being rolled, such as whether the metal strip being rolled is thin or thick, hard or soft, and these conditions influence the likelihood of chatter.

[0066] Here, the rolling mill using the rolls of the present embodiment is mainly targeted at a continuous cold rolling mill, and mainly targeted at a tandem rolling mill of 4 to 6 stands. Figure 5 1 is a diagram showing the structure of a rolling mill using rollers for grinding using a grinding device according to an embodiment of the present invention. Figure 5As shown, the rolling mill has the 1st to 4th (#1 to #4) stands in order from the inlet side in the plate passing direction. It should be noted that other devices attached to the rolling mill (for example, the uncoiler, welding machine and ringing machine on the inlet side, and the cutting machine and winding machine on the outlet side) are omitted in the figure. Figure 5 The rolling mill shown is a four-high mill with upper and lower working rolls and upper and lower backup rolls. In the figure, symbol S represents a steel plate, symbol 41 represents a working roll, symbol 42 represents a backup roll, symbol 43a represents a tensiometer roll, symbol 43b represents a deflector roll, symbol 44 represents a drive device including an electric motor, and symbol 45 represents a housing. It should be noted that, if necessary, a vibrometer for detecting chatter can also be installed in housing 45. As a vibrometer, a piezoelectric element-type vibration sensor is preferred, but other types of vibrometers can also be used. This is because the installation of a vibrometer makes it easier to determine the vibration frequency of chatter occurring in the rolling mill.

[0067] A rolling load detector, consisting of a load cell 47, is installed above the backup rolls on the upper side of each stand. Each stand is also equipped with a roll speed controller, which is an electric motor that changes the circumferential speed of the work rolls, and a roll gap controller that changes the roll gap. Furthermore, a tension gauge 43a between each stand is installed with a tension gauge to measure the tension of the steel sheet S. Furthermore, a thickness gauge 48 is installed at the exit of the first and fourth stands to measure the thickness of the steel sheet S. The rolling mill is equipped with a roll changing device. The roll changing device includes a trolley that can move along rails in the axial direction of the rolls. The roll changing device removes used rolls and replaces ground rolls. Used rolls, with bearing boxes attached, are transported to the roll shop using a crane and a transport trolley.

[0068] Furthermore, all rolls 1 to be ground are assigned roll numbers. This roll number allows the roll grinding operation status to be linked to its usage in the rolling mill. Specifically, the roll number identifies the roll type and the applicable stand of each roll 1 when used in the rolling mill. Newly purchased rolls 1 may sometimes be assigned a different stand after a certain period of use. However, at least when grinding a roll 1 in a roll grinder, the stand and other usage characteristics of the roll 1 when installed in the rolling mill are fixed.

[0069] Furthermore, the spectrum upper limit setting unit 31c sets the specific frequency band and the spectrum upper limit value based on the usage of the roll 1 in the rolling mill, as determined above. The specific frequency band refers to the frequency band of interest during roll grinding, based on the usage of the roll 1 in the rolling mill. In this embodiment, the specific frequency band is set based on the usage of the roll 1 in the rolling mill for the following reasons.

[0070] Specifically, in a continuous rolling mill, since the rolling speed increases from the first stand to the final stand, the corresponding rolls 1 are used with the subsequent stands rotating at a higher speed than the preceding stands. Furthermore, since the diameters of intermediate and backup rolls are generally larger than those of work rolls, the work rolls are used at a higher speed than the backup rolls. Therefore, the speed of the rolls 1 used in a continuous rolling mill varies depending on the roll type and the stand used, such as the roll type. It should be noted that for a tandem rolling mill consisting of at least three continuous rolling stands, it is preferable to determine the roll usage in the mill based on the final stand or one of the stands upstream of the final stand. This is because chatter vibration is more likely to occur in the subsequent stands of a tandem rolling mill. Furthermore, it is more preferable to perform roll acceptance assessment based on the backup rolls installed in the rolling mill. This is because the back rolls have a greater mass than the work rolls, significantly increasing the effect of mill vibration. Similarly, in the case of a six-high rolling mill, it is more preferable to perform the acceptance / failure determination of the rolls on the backup rolls or the intermediate rolls, which have a larger mass than the work rolls.

[0071] On the other hand, chatter vibration occurs at a frequency roughly consistent with the natural vibration frequency of the rolling mill and does not vary significantly depending on the stand. Therefore, the rotation angle of the roll 1 during rotation, corresponding to one vibration cycle of the rolling mill caused by chatter vibration, is larger in the later stands at higher rolling speeds, and smaller in the earlier stands at lower rolling speeds. Furthermore, the rotation angle is larger for work rolls with smaller roll diameters, while it is smaller for backup rolls with larger roll diameters. However, the roll rotation speed during grinding of the roll 1 by a roll grinder is typically set in advance by the roll grinder's control computer 21 or commercial computer 22, without taking into account such mill usage.

[0072] As described above, the frequency band of vibration frequencies that should be considered during roll grinding should vary depending on how the roll 1 is used in the rolling mill. In this embodiment, a specific frequency band for roll grinding is set based on how the roll 1 is used in the rolling mill. This allows for the correlation between chatter vibrations that occur during rolling and the vibration behavior during roll grinding. Specifically, in roll grinding, methods have traditionally been known that focus on vibrations that occur during grinding due to factors such as the rigidity of the roll grinder, targeting chatter lines and the like. This is a problem with the vibrations of the roll grinder itself, resulting from vibrations during grinding that coincide with the natural vibrations of the roll grinder. In contrast, this embodiment focuses on vibrations that coincide with the natural vibrations of the rolling mill in which the roll is mounted during roll grinding, and addresses the question of whether vibrations at frequencies corresponding to these natural vibrations of the rolling mill are generated during roll grinding.

[0073] Meanwhile, in this embodiment, the reason for setting the upper limit of the spectrum based on the usage of the roll 1 in the rolling mill is as follows. Specifically, when the roll 1 is a heavy backup roll, the effect of maintaining mill vibration is strong, so when grinding the roll 1, the allowable unevenness during grinding is small. Therefore, it is necessary to suppress vibration in the roll grinder to a low level. On the other hand, when the roll 1 is a light work roll, the effect of maintaining mill vibration is weak, so when grinding the roll 1, even a large degree of unevenness during grinding is allowable.

[0074] Furthermore, since chatter vibrations are less common in the front stand of a continuous rolling mill, the backup rolls used in the front stand can tolerate a relatively large degree of unevenness imparted during grinding of the roll 1. However, since chatter vibrations are more likely to occur in the rear stand, the tolerated unevenness during grinding of the roll 1 is smaller. Therefore, in this embodiment, the upper limit of the permissible frequency spectrum for vibrations during roll grinding is set based on the manner in which the roll 1 is used in the rolling mill.

[0075] The usage pattern of the roll 1 in the rolling mill is stored in the business computer 22 as a host computer based on the roll number of the roll 1 and is sent to the spectrum upper limit setting unit 31 c directly or via the control computer 21 of the roll grinder.

[0076] Here, the specific frequency band and the spectrum upper limit value set in the spectrum upper limit setting unit 31c can be set based on past actual operations in the rolling mill using the roll 1 being ground. For example, after determining the roll type and applicable stand (e.g., the upper backup roll of the third stand) as the usage pattern in the rolling mill, actual data on the relationship between vibration information during roll grinding of the roll 1 used therein and the occurrence of chatter in the rolling mill can be accumulated in advance. The spectrum upper limit value can be set based on the vibration information during roll grinding of the roll 1 that is causing chatter. Furthermore, the specific frequency band can be set based on the rolling speed at the time of chatter.

[0077] This method allows specific frequency bands and spectrum upper limits to be stored in the spectrum upper limit setting unit 31c for each roll type and applied stand based on past actual operations in the rolling mill. The spectrum upper limit setting unit 31c then obtains information about the roll type and applied stand of the grinding target roll 1 from the host computer, sets the specific frequency band and spectrum upper limit based on this information, and transmits this information to the grinding pass / fail determination unit 31d.

[0078] It should be noted that any frequency band can be selected as a specific frequency band from the spectrum distribution obtained as grinding information of the roller grinder. It is also possible to set two or more frequency bands as the selected frequency bands. In this case, the corresponding spectrum upper limit value can be set separately for each specific frequency band, or the same spectrum upper limit value can be used. As for the bandwidth of the frequency of the specific frequency band, any bandwidth can also be selected. In the roller 1 used in the front stand of the rolling mill and the roller 1 used in the rear stand, for the specific frequency band, the latter selects a higher frequency band, but it is also possible to select a partially overlapping frequency band as their range.

[0079] [Grinding Acceptance Judgment Department]

[0080] The grinding pass / fail determination unit 31d determines the spectral value within the specific frequency band based on the vibration information during grinding of the roller grinder, compares the spectral value with the spectral upper limit, and determines the grinding pass / failure if the determined spectral value exceeds the spectral upper limit; otherwise, the grinding pass / failure is determined. It should be noted that when two or more specific frequency bands are set, a determination of pass / failure may be made if the spectral value within any specific frequency band exceeds the spectral upper limit, or if the spectral value within any specific frequency band exceeds the spectral upper limit. This determination can be appropriately made based on past actual operation of the rolling mill.

[0081] For rolls 1 that have been judged as acceptable, the suitability of final grinding is determined by comparing the rolls 1 with other inspection criteria, such as the presence of visual defects, inspection of finished surface roughness, and inspection of chatter marks, and then the rolls 1 are mounted on the rolling mill for use. On the other hand, rolls 1 that have been judged as unacceptable by the grinding acceptance determination unit 31d are reground.

[0082] [Specified frequency band settings]

[0083] In this embodiment, the specific frequency band in the spectrum upper limit setting unit 31c is preferably set based on the chatter frequency of the rolling mill using the grinding roll 1. This can be done by converting the chatter frequency in the rolling mill into the frequency during grinding in the roll grinder.

[0084] Specifically, a vibration meter is installed on the housing of a rolling mill using the roll 1. Preferably, the vibration meter is installed on each stand of a continuous rolling mill. The stand where chattering occurs is then identified based on the output of the vibration meter installed on the rolling mill. The vibration frequency of the stand where chattering occurs and the rotational speed of the roll 1 at that time are then determined. In this case, the vibration frequency of the rolling mill when chattering occurs is referred to as the chattering frequency.

[0085] For example, if the chatter frequency is Q (Hz) and the rotational speed of the roll 1 in the mill where the chatter occurs is V (mm / s), periodic unevenness may occur on the roll 1 at intervals of V / Q (mm). In this case, the specific frequency ω (Hz) that should be paid attention to when grinding the roll 1 can be calculated using the roll rotation speed Ω (1 / s) and the roll diameter D (mm) during grinding of the roll 1 using the following formula (1).

[0086] ω=Ω·D / (V / Q)…(1)

[0087] However, because there are statistical variations in the chatter frequency and the rotational speed of the roll 1 in the stand where chatter occurs, it is preferable to set the value calculated using formula (1) to have a certain bandwidth as the specific frequency band. Specifically, a bandwidth of approximately ±25% of the specific frequency ω calculated using formula (1) is set as the specific frequency band. It should be noted that the bandwidth can be appropriately set based on past actual operations.

[0088] It should be noted that since the chatter frequency is roughly consistent with the natural vibration frequency of the rolling mill, even if the chatter frequency generated during rolling is not directly measured, the previously identified natural vibration frequency of the rolling mill can be used as the chatter frequency and the specific frequency band can be set using the above-mentioned method. In this regard, the present embodiment is characterized in that, unlike conventional techniques, the focus is not on the natural vibration frequency of the roll grinder during the roll finish grinding process, but rather on the natural vibration frequency of the rolling mill using the ground rolls. Furthermore, the present embodiment is characterized in that the vibration frequency to be considered during roll grinding is determined based on how the rolls are used in the rolling mill. Furthermore, the present embodiment performs a roll acceptance assessment before the rolls are installed in the rolling mill. This reduces the need to replace defective rolls during rolling operations, thereby improving the mill's strip production efficiency.

[0089] Example

[0090] [Example 1]

[0091] As Example 1, in a five-stand continuous cold rolling mill consisting of a four-high rolling mill, the acceptance of the roll grinding of the support rolls of the fourth stand was evaluated. The dimensions of the rolls to be ground were: diameter 1260-1451 mm, barrel length 1750 mm, and total length including the shaft 2300 mm. The grinding stone of the roll grinder used an alumina-based grindstone, with a grindstone diameter of 480-915 mm and a grindstone width of 100 mm. The grinding stone rotation speed was set to 510 rpm, and the grinding stone penetration was set so that the current value of the motor rotating the grinding stone was 140 A during rough grinding and 80 A during the first pass of the fine grinding process during fine grinding, and the amount of grinding stone penetration was gradually reduced with the number of grinding passes.

[0092] The rough grinding process is performed in a reciprocating manner across the entire barrel, with 120 passes in the rough grinding and 8 passes in the fine grinding. As for the transmission speed, it is 1000 mm / min in the rough grinding, gradually decreases from 300 mm / min in the fine grinding, and is 100 mm / min in the final traverse. In addition, the vibration of the roller grinder is measured by an accelerometer installed in the grinding head at a sampling frequency of 1000 Hz. It should be noted that in the vibration information acquisition unit 31b, vibration information related to vibration acceleration is obtained from the vibration meter data during the final 5 passes of the rough grinding process. In addition, the specific frequency band determined by the use of the rolling mill of the rolling mill object is 40 Hz, so the bandwidth is set to ±10 Hz, thereby setting the specific frequency band to 30 to 50 Hz. On the other hand, for the upper limit of the spectrum, based on past actual operations, the vibration acceleration in the specific frequency band is set to 0.1 m / sec. 2 .

[0093] During this process, the rolls were ground multiple times, resulting in acceleration exceeding the upper limit of the frequency spectrum at frequencies near 34 Hz, a specific frequency band. In these cases, the grinding pass / failure determination unit determined the rolls to be unqualified. For rolls that were determined to be unqualified, the depth of cut during the rough grinding process was reduced by approximately 20%, and the rolls were reground. The grinding pass / failure determination unit then re-determined the rolls, resulting in a pass / fail result.

[0094] In this example, the quality of the rolls was determined in this manner, and only the qualified rolls were installed as the backup rolls of the fourth stand of the continuous cold rolling mill, thereby performing cold rolling. The rolling conditions were ordinary steel with a thickness of 0.6 to 1.2 mm and a width of 950 to 1300 mm. All metal strips were cold rolled at a maximum rolling speed of 1100 mpm or higher. As a result, no chatter vibration was detected during the cold rolling of the target metal strips.

[0095] On the other hand, in a comparative example where the grinding pass / failure determination device was not used and acceptance was determined by visual inspection, chattering occurred at approximately one-third of the rolling depth, which served as the benchmark for backup roll replacement. Consequently, rolling was interrupted and backup roll replacement was performed. This resulted in defective portions of the metal strip due to thickness variations and surface defects, and the urgent replacement of backup rolls resulted in a decrease in productivity.

[0096] [Example 2]

[0097] As Example 2, an example of applying the present invention to rolls used in a four-stand continuous cold rolling mill consisting of a four-high rolling mill is shown. The mill of this Example differs from the mill of Example 1. While the roll diameter used in the mill of Example 1 is approximately the same, the rolls used have a shorter barrel length than those used in Example 1. In this Example, the back-up rolls of the third stand of this four-stand continuous cold rolling mill are used as the target, and acceptance is determined during roll grinding.

[0098] The grinding stone used for roller grinding has a diameter of 480 to 915 mm and a width of 100 mm. The grinding stone's rotational speed is set at 510 rpm. The current drawn by the motor rotating the grinding stone is set to 135 A during rough grinding and 70 A during the first pass of the fine grinding process. The depth of the grinding stone is gradually reduced with each grinding pass. The roller's rotational speed is maintained at a constant 6 rpm from rough grinding to fine grinding.

[0099] Here, the rolls used as grinding targets had a diameter of 1355 mm and a diameter of 1420 mm. In this example, the same roll grinder was used to grind them. In this case, due to the different roll diameters, the roll weights also differed. Therefore, when the rolls were loaded on the roll grinder and rotated, the natural vibration frequency of the roll grinder remained unchanged at 40 Hz in all cases. However, in the roll grinder used in this example, the natural vibration frequency of the roll grinder sometimes varied depending on conditions such as the type and weight of the rolls being ground, or the diameter of the grinding stone. In this case, the natural vibration frequency of the roll grinder was confirmed to be in the range of 30 to 50 Hz.

[0100] Meanwhile, both rolls were mounted on the same stand of the rolling mill. In this stand, chatter was observed to occur at a rolling speed of 900 m / min (the peripheral speed of the work rolls in this stand), which is the natural frequency of the rolling mill, between 620 and 700 Hz. Thus, based on the natural frequency of the rolling mill obtained from past actual operation of the rolling mill, the rolling speed at which chatter occurs, and the diameter of each roll, the specific frequency band of each roll was calculated using the rotational speed during roll grinding. The specific frequency band for the 1355 mm diameter roll was 17.7 to 19.9 Hz, and for the 1420 mm diameter roll, it was 18.5 to 20.9 Hz.

[0101] Therefore, during roll grinding, the average value of the spectrum value in the specific frequency band corresponding to each roll is calculated based on the vibration information obtained by the vibration information acquisition unit and compared with the pre-set spectrum upper limit. The spectrum upper limit is set based on past chatter occurrences and sets the vibration acceleration to 0.1 m / sec for all rolls. 2 As a result, for the roll with a diameter of 1355 mm, the spectrum value in the specific frequency band was greater than the spectrum upper limit, so the grinding of this roll was judged as unqualified. On the other hand, for the roll with a diameter of 1420 mm, the spectrum value in the specific frequency band was less than the spectrum upper limit, so the grinding of this roll was judged as qualified.

[0102] Therefore, these rolls were installed in the stands at different rolling times, and cold rolling was performed on ordinary steel strips with a thickness of 0.6 to 1.2 mm and a width of 950 to 1300 mm, with all metal strips being cold rolled at a maximum rolling speed of 900 mpm. As a result, in this example, when using rolls that were deemed unqualified (diameter 1355 mm), chatter occurred in the rolling stand where these rolls were installed at the time of rolling one-fifth of the planned throughput (total weight of rolled steel strip), preventing the planned rolling from being completed. On the other hand, in this example, when using rolls that were deemed acceptable (diameter 1420 mm), chatter did not occur, and the full planned rolling was possible.

[0103] While the embodiments of the invention developed by the present inventors have been described above, the present invention is not limited to the description and drawings that constitute part of the disclosure of the present invention for these embodiments. In other words, other embodiments, examples, and application techniques created by those skilled in the art based on these embodiments are all encompassed within the scope of the present invention.

[0104] Industrial applicability

[0105] According to the present invention, a device and method for determining the grinding quality of a roll that can suppress chatter marks during metal strip rolling can be provided. Furthermore, according to the present invention, a method for rolling a metal strip can be provided that can suppress chatter marks during metal strip rolling, thereby improving the metal strip manufacturing yield.

[0106] Description of Reference Numerals

[0107] 1 Roller

[0108] 2 Grinding Stone

[0109] 3 Grinding head

[0110] 4-axis worktable

[0111] 5-roller chuck

[0112] 6-roller rotary motor

[0113] 7 Tailstock

[0114] 8 supports

[0115] 9a, 9b guides

[0116] 10 Grindstone Rotation Motor

[0117] 11 Pulley

[0118] 12 conveyor belt

[0119] 13 Vibration Meter

[0120] 21 Roller grinding machine control computer

[0121] 22 Business Computers

[0122] 23 Roller Grinding Machine Control Controller

[0123] 31 Roller grinding qualification judgment device

[0124] 31a Vibration meter data acquisition unit

[0125] 31b Vibration information acquisition unit

[0126] 31c Spectrum upper limit setting unit

[0127] 31d Grinding pass / fail judgment unit

[0128] 41 working rolls

[0129] 42 support rollers

[0130] 43a Tensiometer roller

[0131] 43b Deflector roller

[0132] 44 Drive unit

[0133] 45 shell

[0134] 47 Load Cell

[0135] 48 Thickness Gauge

[0136] S steel plate

Claims

1. A device for determining whether the grinding of a roll is acceptable or not, comprising: a vibration meter data acquisition unit that uses a vibration meter installed in the roll grinder to acquire vibration meter data when a roll is ground using the roll grinder; a vibration information acquisition unit that acquires vibration information during roll grinding by frequency analysis of the vibration meter data; a spectrum upper limit setting unit for setting a specific frequency band and a spectrum upper limit value determined based on the roll type and the applied stand of the roll; and A grinding pass / fail determination unit determines whether the grinding of the roll is pass / fail based on the spectrum value in the specific frequency band of the vibration information and the spectrum upper limit value.

2. The device for determining whether grinding of a roll is acceptable or not according to claim 1, wherein: The vibration information during the roll grinding acquired by the vibration information acquisition unit is vibration information selected from one or two or more grinding passes in a rough grinding process of the roll.

3. The device for determining whether grinding of a roll is acceptable or not according to claim 1 or 2, wherein: The spectrum upper limit setting unit sets the specific frequency band based on a chattering frequency of a rolling mill using the rolls.

4. A method for determining whether the grinding of a roll is qualified or not, comprising: a vibration meter data acquisition step of acquiring, using a vibration meter installed in the roll grinder, vibration meter data when a roll is ground using the roll grinder; a vibration information acquisition step of acquiring vibration information during roll grinding by frequency analysis of the vibration meter data; a frequency spectrum upper limit setting step of setting a specific frequency band and a frequency spectrum upper limit value determined based on the roll type and the applied stand of the roll; and The grinding pass / failure determination step is to determine whether the grinding of the roll is pass / fail based on the spectrum value in the specific frequency band of the vibration information and the spectrum upper limit value.

5. The method for determining whether grinding of a roll is acceptable or not according to claim 4, wherein: The vibration information during the roll grinding acquired in the vibration information acquisition step is vibration information selected from one or two or more grinding passes in the rough grinding process of the roll.

6. The method for determining whether grinding of a roll is acceptable or not according to claim 5, wherein: The grinding stone cutting depth per grinding pass in the rough grinding step is 30 to 200 μm.

7. The method for determining whether grinding of a roll is acceptable or not according to claim 5, wherein: The current value of the grindstone rotating motor in the rough grinding step is 1.0 to 1.6 A per 1 mm of the grindstone width.

8. The method for determining whether grinding of a roll is acceptable or not according to claim 4 or 5, wherein: The frequency spectrum upper limit setting step includes the step of setting the specific frequency band based on a chatter occurrence frequency of a rolling mill using the rolls.

9. The method for determining whether grinding of a roll is acceptable or not according to claim 8, wherein: The rolling mill is a rolling mill in either the final stand of a tandem rolling mill or a stand on one upstream side of the final stand, and the rolls are backup rolls of the rolling mill.

10. A method for rolling a metal strip, comprising: a roll determination step of determining a roll to be installed in a rolling mill using the roll grinding pass / fail determination method according to any one of claims 4 to 9; and A rolling step of rolling the metal strip using a rolling mill equipped with the rolls determined in the roll determination step.

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