JP7269484B2 - Cold tandem rolling equipment and cold tandem rolling method - Google Patents

Description

The present invention relates to a cold tandem rolling facility and a rolling method for continuously cold-rolling a hot-rolled steel strip (hot-rolled steel strip) in a steel plate manufacturing process. This relates to a cold tandem rolling facility and a cold tandem rolling method suitable for continuous cold rolling of hot-rolled strip in which the distribution of deformation resistance in the width direction is uneven in the longitudinal direction. .

Specific examples of the hot-rolled strip in which the distribution of deformation resistance in the width direction is uneven in the longitudinal direction include high-tensile steel sheets (high-tensile steel sheets), stainless steel sheets, electromagnetic steel sheets, etc. There is In addition, as a manufacturing process for hot-rolled steel strip (hot-rolled steel strip), a steel slab is hot-rolled by a rough rolling mill and a finishing rolling mill, wound into a coil, and the coil is cooled in the atmosphere. and a manufacturing process in which rough rolling is omitted, hot rolling corresponding to finish rolling is performed, coiling is performed, and the coil is cooled in the air. In addition, for thin cast slabs (thin slabs) produced by the twin roll continuous casting method known as thin plate continuous casting and rolling or the belt continuous casting method, it is equivalent to a finishing rolling mill immediately without rough rolling. A manufacturing process in which the steel is rolled down by an inline mill, wound into a coil, and then cooled in the air. Furthermore, continuous casting, hot rough rolling, and hot finish rolling are performed continuously without interruption. There is also a process.

Hereafter, as an example, a steel slab is hot-rolled by a rough rolling mill and a finishing rolling mill, wound into a coil, and the coil is further cooled in the atmosphere to cold-roll the strip coil. A case of manufacturing a non-oriented electrical steel sheet will be described as an example.

For example, in Patent Document 1, in mass%, C ≤ 0.008, 2 ≤ Si + Al ≤ 3, 0.02 ≤ Mn ≤ 1.0, S ≤ 0.003, N ≤ 0.002, Ti ≤ 0.003 , 0.001 ≤ REM ≤ 0.02, and 0.3 ≤ Al/(Si + Al) ≤ 0.5. Hot finish rolling is performed in a temperature range in which the interfinishing rolling temperature is 1050 ° C. or higher, the subsequent no water injection time is 1 second or more and 7 seconds or less, and the coiling is performed at 700 ° C. or less by water injection cooling. A manufacturing method is disclosed in which a cooling process after hot finish rolling replaces the hot-rolled plate annealing process.

JP 2010-242186 A JP-A-60-46804 JP-A-2002-239617 Japanese Patent Application Laid-Open No. 2003-340510 JP-A-3-60810 JP 2014-8520 A JP-A-10-128421

"Illustrated Electromagnetic Steel Sheet" (Shin Nippon Steel Co., Ltd., 1994), p.67

However, as shown in Patent Document 1, for example, self-annealing coils for non-oriented electrical steel sheets, which are wound into coils by omitting the hot coil annealing process due to self-annealing in the cooling process after continuous hot rolling, It has been recognized that there are the following problems when pickling and continuously cold-rolling with a cold tandem rolling mill.

1) A hot-rolled steel strip after hot rolling is usually coiled at, for example, 700° C. or less, and then cooled in the atmosphere while still in the coil state. In such a cooling process, the cooling rate varies depending on the position of the material within the coil. Specifically, the cooling rate of the outer peripheral part of the coil is higher than the cooling rate of the inner peripheral part, and the cooling rate of the end (edge part) in the strip width direction is lower than that of the central part in the strip width direction. speed increases.
Due to such variations in the cooling rate in the coil, non-uniformity of the material in the longitudinal direction and the width direction of the plate, particularly non-uniformity in strength, and thus non-uniformity in cold deformation resistance occur. . Such coils are referred to herein as self-annealed coils. The material (steel type) of the self-annealed coil is not limited to the non-oriented electromagnetic plate described above. It means a steel type that causes non-uniform deformation resistance in the cold.

2) As described above, in the self-annealed coil, non-uniformity of the material in the longitudinal direction and the sheet width direction in the coil is caused near the outer periphery of the self-annealed coil and near the edge (width direction end of the wound hot-rolled steel strip). ), but the unevenness is remarkable in the area 150 mm to 250 mm inward from the end (edge portion) in the sheet width direction in 2 to 3 turns on the outer peripheral side of the self-annealing coil. In the region, the strength of the widthwise ends of the strip may be higher than the strength of the widthwise central portion by about 10% to 20%.

3) When the self-annealed coil having non-uniformity in material as described above is welded into a continuous strip, pickled and cold-tandem rolled, the above-mentioned coil is placed in the first stand of the cold tandem rolling mill. Since the difference in deformation resistance at the non-uniform material portion, that is, the deformation resistance at both ends in the width direction of the plate is greater than the deformation resistance at the central portion in the width direction, the shape of the rolled plate becomes medium elongation, which is the so-called Squeezing may occur and plate breakage may occur.

4) If sheet breakage occurs due to drawing due to medium elongation, damage to the work rolls in the rolling stand in the cold tandem rolling mill often occurs. In that case, rolling must be stopped and work rolls must be replaced, resulting in a significant drop in productivity.

5) Furthermore, when sheet breakage due to drawing is severe (in the case of sheet breakage due to severe middle elongation), it is necessary to replace not only the work rolls but also the intermediate rolls or backup rolls in contact with the work rolls. Become.

6) Especially during high-speed rolling, sheet breakage due to drawing is severe, and it may take a long time of about 10 hours to recover, resulting in a significant decrease in productivity.

As described above, in the subsequent cold tandem rolling of the self-annealed coil, sheet breakage due to drawing is likely to occur, and the actual situation is that there is a strong possibility that productivity will be hindered.
Therefore, in cold tandem rolling of self-annealed coils, a cold tandem rolling facility and a rolling method capable of preventing plate breakage have been strongly desired.

In general, it is known to control the plate shape during rolling in order to prevent drawing from occurring in the rolling mill. That is, a shape detector is installed on the delivery side of the rolling mill to measure the shape of the rolled strip, and the shape control end of the rolling mill (for example, the workpiece It is known to control the roll bender force) (for example, US Pat. Such shape control is generally performed at the final stand.

Further, Patent Document 3 proposes a method of controlling the shape by installing a shape detector on the delivery side of the rolling mill in the first stand of the cold tandem rolling mill to measure the shape of the rolled strip. Furthermore, Patent Document 4 proposes a method for controlling the shape by installing a shape detector on the delivery side of the rolling mill in the first stand and the second stand of the cold tandem rolling mill to measure the shape of the rolled strip. ing. Further, Patent Document 5 proposes a method of installing a shape detector on the delivery side of the rolling mill in all the stands of the cold tandem rolling mill, measuring the shape of the rolled strip, and controlling the shape.

On the other hand, Patent Literature 6 discloses a shape control method when there is uneven deformation resistance distribution in the plate width direction. That is, in Patent Document 6, the yield stress in the width direction of the hot-rolled steel strip is measured in advance at the positions of the tip, center, and tail in the longitudinal direction of the hot-rolled steel strip, and the deformation resistance distribution pattern is investigated. A method of presetting the shape of the rolling mill based on the results (performing different shape presets at the front end, center, and tail end positions of the hot-rolled steel strip in the longitudinal direction) is disclosed.

The shape control methods disclosed in Patent Documents 2 to 5 above measure the plate shape by a shape detector installed on the delivery side of one or more rolling mill stands, and the measured plate shape is the target. It is a method of feedback-controlling the shape control end of the rolling mill stand so that it conforms. Although this method is effective for hot-rolled steel strips in which drawing does not easily occur even if the plate shape changes, and for relatively gradual changes such as thermal crown, self-annealing is the main object of the present invention. It is recognized that coils are not always effective.

The reason for this is that the self-annealed coil, in which the hot coil annealing process is omitted, has a large non-uniform deformation resistance distribution and abrupt change in the longitudinal direction. However, in the shape control methods by feedback control as shown in Patent Documents 2 to 5, there is dead time between the hot-rolled steel strip from a certain rolling mill stand to the shape detector on the delivery side of the rolling mill stand. There is Therefore, when the shape change is large and sudden, the feedback control is not in time.

When the inventors of the present invention investigated the data of the plate breakage of the first stand due to drawing of the self-annealed coil, it was found that at a rolling speed of 200 m / min at the first stand, the edge elongation with a steepness of 1% was obtained in about 2 seconds. It has been confirmed that the elongation changes from 1 to 2%, and as a result, the drawing occurs and the plate breaks. In this case, since the shape detector is installed 3m away from the exit of the roll bite of the 1st stand (it is impossible to make it less than 3m due to space considerations), it takes about 1 second to detect the shape. Even if the shape control is started after that, it takes about 1 second. Therefore, it takes about 2 seconds of wasted time until the shape control is actually performed after leaving the roll bite. Therefore, it is difficult to prevent plate breakage in time for the sudden change in shape. At this time, if the rolling speed at the first stand is reduced to 100 m/min, the relative rolling length at which shape control starts will be shortened by half, but the dead time until the shape is detected will be doubled. Therefore, it is difficult to prevent sheet breakage even if the rolling speed is reduced.

On the other hand, disclosed in Patent Document 6, the yield stress in the width direction of the material at the tip, center, and tail in the longitudinal direction of the original plate coil was measured in advance to investigate the deformation resistance distribution pattern, and the investigation results ( The method of performing shape presetting (feedforward control) in the rolling mill stand based on the prediction result) is effective for reproducible materials for each coil of hot-rolled steel strip. However, the self-annealed coil, which is the object of the present invention, is affected by changes in the sheet shape during cold rolling, depending on the sheet shape and scale after hot rolling and the coil cooling conditions after winding (coil arrangement position, seasonal factors, etc.). The situation is very different. For this reason, there is a large variation in prediction results, and it cannot be said that there is practical reproducibility. That is, it is difficult to pattern the deformation resistance distribution over the entire length of the coil based on predictive research. By the way, if an inappropriate pattern is input, there is a risk that it will promote medium elongation and induce strip breakage.

In addition, without predicting the deformation resistance distribution pattern as described above, it is also conceivable to preset the rolling mill stand to an end-elongated shape so that the intermediate elongation does not occur even if the deformation resistance distribution changes. In this method, the deformation resistance distribution of the hot-rolled steel strip is not so large, the deformation resistance does not change much in the length direction of the hot-rolled steel strip, and there is no variation in each coil of the hot-rolled steel strip. is effective to some extent. However, in the self-annealed coil, which is the main object of the present invention, the distribution of deformation resistance in the width direction of the hot-rolled steel strip varies greatly in the length direction. Therefore, in order to prevent middle elongation, if you preset so that edge elongation occurs even at points with uneven deformation resistance distribution (hard plate edges), edge elongation can be achieved at points with uniform deformation resistance distribution (hard plate edges). becomes too large, conversely, constriction occurs due to excessive edge elongation, which may induce plate breakage.

As described above, conventionally, when cold tandem rolling is performed on a coil such as a self-annealed coil that has large non-uniform deformation resistance distribution in the longitudinal direction and width direction of the hot-rolled steel strip, the occurrence of strip breakage is reliably prevented. The actual situation is that a control method for controlling the vibration has not yet been established.

By the way, in the cold tandem rolling, a tension meter is installed between each rolling mill stand, and the plate tension between the stands is constantly monitored during rolling to detect the tension change, and the tension-free state is reached. In the past, it has been practiced to recognize the breakage of the strip and stop the rolling immediately (see, for example, Patent Document 7).
However, even if the occurrence of strip breakage is detected by the tension between the stands and the rolling is stopped urgently, the broken part jumps abruptly along with the strip breakage, or the broken part is bent and the two sheets get caught. The work rolls, backup rolls, or intermediate rolls are often damaged at the stand where the break occurred and at each stand through which the subsequent broken portion passed. Therefore, as already mentioned, it takes a long time to replace work rolls and the like, and it also takes a considerable amount of time to treat strip breakage in the rolling mill. As a result, it takes an extremely long time to resume (restart) rolling after detecting a breakage and making an emergency stop, which inevitably leads to a significant drop in productivity.

By the way, if the occurrence of fracture is predicted at an early stage (that is, the sign of fracture is detected) and rolling is stopped urgently, it is possible to minimize the decrease in productivity due to fracture. . However, as already described (for example, as shown in Patent Document 7), the tension between each stand is monitored, and when the tension becomes zero, a breakage is detected and an emergency stop is performed. It was an emergency stop after the fracture occurred, and it was not possible to predict the occurrence of the fracture at an early stage.

The present invention has been made in view of the above problems. Even in tandem rolling, the possibility of strip breakage is predicted before strip breakage occurs, and rolling can be stopped urgently at that timing. It is an object of the present invention to provide a cold tandem rolling facility and a cold tandem rolling method capable of minimizing the decrease.

When the inventors of the present invention investigated the state of strip breakage in cold tandem rolling of self-annealed coils with a large uneven distribution of deformation resistance, it was found that the breakage of the strip does not occur suddenly, but rather a relatively small hole-shaped breakage portion. (Hole-like hollow portions that have not yet broken) are generated, and then, as rolling progresses, the strip breaks from the vicinity of the broken portions. Therefore, it is recognized that if the occurrence of a broken part before the break is detected and rolling is stopped urgently, the damage caused by the break (roll damage) can be minimized and a significant decrease in productivity can be suppressed. As a result, the present invention has been completed.

Specific embodiments of the cold tandem rolling equipment and the cold tandem rolling method of the present invention are shown below.

The cold tandem rolling equipment of the basic aspect (first aspect) of the present invention includes:
Of the plurality of rolling mill stands in a cold tandem rolling mill in which a plurality of rolling mill stands are arranged in series, at least on the delivery side of the first rolling mill stand located on the most upstream side, the strip to be rolled, A broken part detection device is provided to detect the occurrence of a broken part that has not yet broken, and an emergency stop device is provided to stop the rolling operation of the cold tandem rolling mill based on the detection result of the broken part detection device. It is characterized by

In addition, the cold tandem rolling equipment of the second aspect of the present invention is
In the cold tandem rolling equipment of the first aspect,
The broken part detection device is characterized by being an optical detection device.

Furthermore, the cold tandem rolling equipment of the third aspect of the present invention is
In the cold tandem rolling equipment of the first aspect,
The broken part detection device is characterized by being an acoustic detection device.

Further, the cold tandem rolling method of the fourth aspect of the present invention is
In cold rolling the strip with the cold tandem rolling equipment according to any one of the first to third aspects,
The rolling is stopped by operating the emergency stop device when the broken portion is detected by the broken portion detection device.

According to the cold tandem rolling equipment and the cold tandem rolling method of the present invention, a hot rolled steel strip in which the distribution of deformation resistance in the width direction is uneven in the longitudinal direction, such as a self-annealed coil, is cold rolled. Even when rolling with a tandem rolling mill, by detecting a broken part that does not break the plate at least on the delivery side of the first rolling mill stand on the most upstream side and stopping rolling early, the roll after the emergency stop It simplifies and shortens the replacement work and eliminates the need to treat the broken portion in the rolling mill, thereby minimizing the decrease in productivity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of a production line for non-oriented electrical steel sheets incorporating cold tandem rolling equipment according to an embodiment of the present invention;

<Embodiment of cold tandem rolling equipment>
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
FIG. 1 shows an example of an electrical steel sheet production line incorporating a cold tandem rolling facility according to an embodiment of the present invention.

In FIG. 1, coils C1 and C2 are hot-rolled sheets for non-oriented electrical steel sheets (self-annealed coils) obtained by omitting the hot coil annealing process, for example, by self-annealing in the cooling process of continuous hot rolling. It is wound up.

Here, the chemical composition of the hot-rolled sheet for non-oriented electrical steel sheet and the cooling conditions after hot rolling for self-annealing are basically not limited. Even if the steel sheet is produced by the method, the chemical composition and cooling conditions may be such that the performance as a non-oriented electrical steel sheet is finally secured. For example, the chemical composition and cooling conditions described in Patent Document 1 are suitable. be.

That is, in mass %, C≦0.008%, 2%≦(Si+Al)≦3, 0%. 02%≤Mn≤1.0%, S≤0.003%, N≤0.002%, Ti≤0.003%, 0.001%≤REM≤0.02%, and 0.001%≤REM≤0.02%. Satisfying the relationship of 3% ≤ Al / (Si + Al) ≤ 0.5%, using a slab for non-oriented electrical steel sheet containing the balance Fe and inevitable impurities, hot finish rolling temperature is 1050 ° C. or higher It is preferable to use a self-annealed coil in which hot finish rolling is performed in a temperature range of 1 to 7 seconds without water injection, and the coil is wound at 700° C. or less by water injection cooling.

In FIG. 1, self-annealed coils C1 and C2 as described above are supplied to a coil dispensing machine 1. As shown in FIG. The strips discharged from the self-annealed coils C1 and C2 by the coil discharger 1 are welded by the welding machine 2 at the tail end of the plate from the preceding coil and the front end of the plate from the following coil to form a continuous strip. It becomes (self-annealed strip) S and is sent to the looper 3 . In the following. The self-annealed strip S discharged from the self-annealed coils C1 and C2 and made continuous is sometimes simply referred to as a strip or a self-annealed plate.
The looper 3 is controlled so that there is no stagnation of strip supply in the downstream process even when there is no payout during coil joining in the welding machine 2 (that is, when the running of the strip is stopped). The self-annealing coils C1 and C2 supplied to the coil dispensing machine 1 may be heated in advance to a temperature of 60° C. or higher using a hot bath or the like.

The self-annealed strip S that has passed through the looper 3 is supplied to the pickling facility 4 . In this pickling equipment 4, the surface scale of the self-annealed coil is removed (scraped). In order to increase the cutting efficiency before pickling, a rolling mill for cracking the surface of the self-annealed strip S, a leveler or tension leveler, shot blasting (dry or wet), or a grinder may be installed.

The self-annealed strip S, which has been pickled to remove surface scales, is sent to a cold tandem rolling mill 7 and rolled to a thinner thickness.

In this embodiment, the cold tandem rolling mill 7 is composed of five rolling mill stands 7a to 7e arranged in series. (4Hi mil).
Furthermore, in the cold tandem rolling mill 7, although not shown, rolling lubricating oil called coolant is mixed with water and made into an emulsion, which is supplied at the entrance and exit sides of each stand. . The supplied coolant is collected in a tank (not shown), and is again supplied to each stand for resuscitation lubrication.

In the cold tandem rolling mill 7, for example, a self-annealed strip for non-oriented electrical steel sheet having a thickness of 2.3 mm and a width of 1200 mm is rolled to a thickness of 0.3 mm. As the coolant, for example, rolling lubricating oil based on synthetic ester (hindered complex ester) is supplied to each stand at a concentration of 2% and a temperature of 60° C. at a rate of 1 to 3 m ³ /min (on the inlet side and the outlet side). total), providing rolling lubrication and work roll cooling.

The work roll diameter of each rolling mill stand 7a to 7e is, for example, 500 mm to 700 mm, the backup roll diameter is, for example, 1,300 mm to 1,600 mm, and the barrel length is, for example, 2,000 mm.

On the delivery side of the first rolling mill stand 7a of the cold tandem rolling mill 7, there is a breakage sensor for detecting a broken portion (hole-shaped space) caused by drawing or the like by rolling of the first rolling mill stand 7a. A part detection device 5 is installed.

Here, the broken portion means a hole-shaped portion penetrating in the thickness direction of the strip within the width of the strip. In other words, it penetrates in the thickness direction of the strip in a state (non-broken state) where the front portion of the strip in the rolling direction and the rear portion of the strip in the rolling direction are not completely divided (broken) during rolling. means part. The shape and size of the broken part are various, but the planar shape of the broken part due to drawing is usually crescent, semicircle, circle, ellipse, or fissure. It is about 10 mm×20 mm on average.

Although the specific configuration of the broken portion detection device 5 is not particularly limited, an optical or acoustic detector can be used. In this embodiment, the optical detector detects light passing through the broken portion. It is used as a detector. That is, in this embodiment, as shown in FIG. 1, from one plate surface side of the strip S, a light source 5A that radiates light to the plate surface over the entire width of the strip and a broken portion within the width of the strip. A broken portion detecting device 5 is constituted by a light receiver 5B for receiving the passing light on the other plate surface side of the strip.

The optical break detection device 5 is not limited to the method of detecting light passing through the break as described above, and may be configured to detect the break by image processing, for example. That is, using a moving image capturing device (video camera) that continuously captures the surface of the strip (within the width of the strip) or a still image capturing device (still camera) that captures intermittent images, the captured image is immediately processed (for example, binarization), and the broken portion is detected from the binarized image. The light source is not limited to visible light, and infrared rays, X-rays, or γ-rays may be used.

In addition, as the acoustic break detection device 5, a gas such as compressed air is blown to the surface of the strip over almost the entire width of the strip to generate minute vibrations in the strip. It is possible to use a device configured to detect a broken portion by frequency analysis of sound (vibration sound). That is, if the frequency analysis of the vibration sound by blowing compressed air or the like on the strip as described above is performed, the present inventor found that when there is a broken portion, a peak appears in a different frequency band than when there is no broken portion. etc. have been confirmed.

Specifically, when there is no broken portion, vibration occurs at a frequency in the middle to high frequency band, and a relatively high-pitched vibration sound is generated. On the other hand, if there is a broken portion, low-frequency vibration is added to the middle-to-high-frequency vibration, and relatively low-pitched sounds are mixed. Therefore, for example, a sound generation source (for example, a compressed air generator) is installed facing the plate surface of the strip and a sound collector is installed to collect the vibration sound, and the collected sound is analyzed by a frequency analysis device. As a result, it can be determined that there is a broken portion when a low-frequency sound exceeding a predetermined level (threshold value) is included.

In the case of self-annealed strips, in which multiple self-annealed coils are welded together continuously, punch holes are formed near the welds or smooth arc-shaped In some cases, a notch is formed in the sheet and subjected to cold tandem rolling in that state. In that case, when the punched hole or the cut portion passes through the broken portion detection device, it is expected that the punched hole or the cut portion may be misidentified as a broken portion. In order to avoid this, it is possible to track the positions of the punched holes and cuts during continuous rolling and perform signal processing so as to ignore the detection signals when these parts pass through the broken part detection device. preferable.

Furthermore, the cold tandem rolling mill 7 is provided with an emergency stop device 6 for emergency stopping the cold tandem rolling mill 7 based on the detection signal when the broken portion detection device 5 detects a broken portion. If the emergency stop device 6 is configured to control the cold tandem rolling mill 7 so as to urgently stop the rolling of the strip S by the cold tandem rolling mill 7 when the detection signal of the broken portion is given. Often, for example, the rotation of the work rolls of the rolling mill stands 7a to 7e of the cold tandem mill 7 is stopped by the detection signal of the broken portion, and the strip threading is stopped (then each rolling mill stand 7a to 7e is released). As an emergency stop method in this case, for example, as disclosed in Patent Document 7, the strip is threaded while adjusting the tension of the strip between the stands of the rolling mills so that it becomes the steady tension during threading. preferably stopped.

In some cases, the emergency stop device 6 may perform control to immediately release the rolling force of the work rolls of the rolling mill stands 7a to 7e in response to the detection signal of the broken portion.

A cutting machine 8 for cutting the continuously rolled self-annealed strip is provided downstream of the cold tandem rolling mill 7, and a carousel for winding the continuously rolled self-annealed strip downstream thereof. A reel 9 is provided. Although not shown, the coil wound by the carousel reel 9 and cut is discharged from the roll, placed on a conveyor, and transported to a factory or the like for the next process.

Next, an embodiment of the cold tandem rolling method of the present invention will be described.

<Embodiment of cold tandem rolling method>
The cold tandem rolling method of the embodiment basically uses cold tandem rolling equipment such as that shown in FIG. In rolling, when a broken portion is detected by the broken portion detection device, the emergency stop device is operated to stop rolling.

In the cold tandem rolling facility shown in FIG. 1, the broken portion detector 5 is installed on the delivery side of the first rolling mill stand 7a (upstream of the second rolling mill stand 7b). Therefore, at the time (timing) when the broken part caused by the drawing generated during rolling in the first rolling mill stand 7a reaches the delivery side of the first rolling mill stand 7a and reaches the broken part detection device 5 and is detected (timing), rolling is stopped. It will be an emergency stop.

Here, if the broken portion generated in the first rolling mill stand passes through each rolling mill stand in the latter stage (after the second rolling mill stand) without suddenly stopping rolling at the above timing, the broken portion rapidly expands and progresses, leading to plate fracture. As a result, in each stand after the second rolling mill stand, the work rolls and the like are severely damaged due to the sudden jumping of the broken portion and the double-roll jamming caused by the bending of the broken portion. However, in the case of the present embodiment, when a broken portion is detected on the exit side of the first rolling mill stand 7a (the entry side of the second rolling mill stand 7b), rolling is immediately stopped in an emergency. The work rolls of the stands after the stand 7b are prevented from being damaged by the broken portion of the plate.
Therefore, replacement of the work rolls of each stand after the second rolling mill stand becomes unnecessary, and the time required for roll replacement is eliminated or shortened. At the same time, it becomes unnecessary to process the strip broken portion in the cold tandem rolling mill. Therefore, the time required for resuming operation after an emergency stop (rolling stop time is also significantly shortened as a whole, and productivity can be greatly improved.

In the present embodiment, since a broken portion that occurs during rolling in the first rolling mill stand is detected on the delivery side of the first rolling mill stand and an emergency stop is made, the broken portion causes the first rolling stand to break. The work rolls (and possibly the work rolls of the second mill stand) can become damaged. However, even in that case, the work rolls of each stand after the first rolling mill stand (or after the second rolling mill stand) are often not damaged as described above, so after the emergency stop, the work rolls of the first rolling mill stand will not be damaged. Only the work rolls (or the work rolls of the first and second stands) need to be replaced. Therefore, compared to the case of replacing the rolls of each stand after the second rolling mill stand (or after the third rolling mill stand) in addition to the rolls of the first rolling mill stand (for example, all stands), after an emergency stop The work time required for roll replacement is greatly reduced. Further, the damage to the rolls of the first rolling mill stand due to the occurrence of the broken portion in the first rolling mill stand in the case of this embodiment is much lighter than the damage due to plate breakage. As a result, the backup rolls and intermediate rolls of the first rolling mill stand are less likely to be damaged, and this also contributes to shortening the roll replacement work after an emergency stop.

Examples (Example 1, Example 2) and comparative examples relating to the cold tandem rolling method of each embodiment of the present invention will be described below.
Each example and comparative example were carried out in cold tandem rolling equipment having the configuration shown in FIG. That is, the cold rolling mill consisted of first to fourth rolling mill stands, and each rolling mill stand consisted of a quadruple rolling mill (4Hi mill).

The strip subjected to tandem cold rolling in each example and comparative example was a self-annealed strip for non-oriented electrical steel sheets with a thickness of 2.3 mm and a width of 1200 mm, and C: 0.007% by mass. (Si + Al): 2.5%, Mn: 0.5%, S: 0.001%, N: 0.001%, Ti: 0.001%, REM: 0.01%, and further Al / (Si + Al): Hot finish rolling at a hot finish rolling temperature of 1090 ° C. using a slab for non-oriented electrical steel sheet that satisfies the relationship of 0.4% and contains the balance Fe and unavoidable impurities After that, the time without water injection was set to 6 seconds, and the winding was performed at 680° C. by cooling with water injection.

A strip discharged from such a coil (self-annealed coil) was made continuous by welding and rolled as a self-annealed strip to a thickness of 0.3 mm by the cold tandem rolling mill. As for the rolling speed, the rolling speed of the final stand at the time of coil change was set to 250 m/min, and the maximum rolling speed of the final stand was set to 1100 m/min. Further, as shown in Table 1 below, the tension between each stand was set to 50 to 250 MPa.

As the broken portion detection device, in Example 1, an optical detector that detects the passage of light through the broken portion as shown in FIG. 1 is used, and in Example 2, detection is performed by frequency analysis of the acoustic signal. An acoustic detector was used, and in both Example 1 and Example 2, a break detection device was installed between the exit side of the first rolling mill stand and the entry side of the second rolling mill stand. Oita.

Modes of measurement and control in each example and comparative example are as follows.
・Comparative example: This is an example corresponding to the conventional general rolling method, and even if there is a deformation resistance distribution in the strip width direction, the self-annealed strip was rolled as it was without detecting the broken part and without the accompanying emergency stop. .
- Example 1: An optical broken part detection device was installed on the delivery side of the first stand, and when a broken part of the strip was optically detected, rolling was stopped urgently.
Example 2: An acoustic break detection device was installed on the delivery side of the first stand, and rolling was stopped urgently when a break in the strip was detected by frequency analysis.

As described above, 500 coils of self-annealed strips were rolled for each of the examples and the comparative examples. In each example, the occurrence of strip breakage and the time from emergency stop to restart (rolling stop time: mainly time required for roll replacement, but if strip breakage occurs, treatment of the broken part time required) were investigated. The results are as follows.

- Comparative example (prior art): Plate breakage occurred at a probability of about 3%. The rolling stop time was 4 hours to 18 hours. Here, in strip breakage during high-speed rolling, the surface of the backup roll may also be damaged. was also required, and a long time of about 18 hours was required.
- Examples 1 and 2: No plate breakage occurred. As a result, the treatment of the fractured portion was not required, and the rolling stop time was suppressed to within 30 minutes at the maximum. Here, there were few cases where the work rolls needed to be replaced, but in rare cases it was necessary to rearrange the work rolls of the first stand or the first stand and the second stand. Even in that case, the rolling stop time was about 30 minutes. In addition, the case where the surface of the backup roll was damaged was not recognized at all.

Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also naturally belong to the technical scope of the present invention.

For example, in the above embodiments, the self-annealed material of the non-oriented electrical steel sheet is targeted, but the present invention is not limited to such an example. For example, grain-oriented electrical steel sheets, other high-strength steels, stainless steel sheets, etc., may be used as objects, and not only self-annealed hot-rolled strips, but also large non-uniform deformation resistance in the length direction and width direction of the strip. It can be applied in some cases to prevent plate breakage during cold tandem rolling.

In the above example, a quadruple rolling mill (4Hi mill) is used as each rolling mill stand, but the present invention is not limited to this, and a six-fold rolling mill (6Hi mill), for example, may be used.

In the above-described embodiment, the broken portion detection device is provided only on the delivery side of the first rolling mill stand. Each stand (excluding the last stand) is equipped with a broken part detection device on the output side of one or more stands, and when one of the broken part detection devices detects a broken part, it detects it. The rolling may be stopped urgently based on the signal.

Preferred embodiments and experimental examples of the present invention have been described above, but these embodiments and experimental examples are merely examples within the scope of the present invention, and are within the scope of the present invention. , additions, omissions, substitutions, and other changes are possible. That is, the present invention is not limited by the foregoing description, but is limited only by the scope of the appended claims, and can of course be modified within the scope thereof.

C1, C2 Self-annealed coil S Self-annealed strip 1 Coil payout machine 2 Welder 3 Looper 4 Pickling equipment 5 Broken part detection device 5A Light source 5B Light receiver 6 Emergency stop device 7 Cold tandem rolling mill 7a, 7b, 7c, 7d , 7e rolling stand of cold tandem rolling mill 8 cutting machine 9 carousel reel

Claims (2)

Of the plurality of rolling mill stands in a cold tandem rolling mill in which a plurality of rolling mill stands are arranged in series, at least on the delivery side of the first rolling mill stand located on the most upstream side, the strip to be rolled, A broken part detection device is provided to detect the occurrence of a broken part that has not yet broken, and an emergency stop device is provided to emergency stop rolling by the cold tandem rolling mill based on the detection result of the broken part detection device. and
A cold tandem rolling facility , wherein the broken part detection device is an acoustic detection device . In cold rolling the strip by the cold tandem rolling equipment according to claim 1 ,
A cold tandem rolling method, wherein the emergency stop device is actuated to stop rolling when a broken portion is detected by the broken portion detection device.

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