JP2000210717A - Manufacture of steel sheet and manufacturing device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacturing method for steel sheets by which defects of the steel sheet is detected at an early stage and a countermeasure for removing these defective parts is easily worked out. SOLUTION: By providing an ultrasonic test equipment 20 on the inlet side of a pickling tank 8 in a pickling stage after hot rolling, flaw detection is continuously executed about the defects of the hot rolled steel sheet 15 during conveying, stamp (marking) is executed on the surface of the steel sheet in defective parts with marking devices 50 (50a, 50b). In the hot rolled steel sheet 15 after pickling, the stamp is read with a reader 13c and the defective parts on the hot rolled steel sheet 15 are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of a hot-rolled steel sheet or a cold-rolled steel sheet, and more particularly to a method for producing a steel sheet characterized by flaw detection of the steel sheet and use of defect information by the flaw detection.

[0002]

2. Description of the Related Art Conventionally, flaw detection during the production of a cold-rolled steel sheet is carried out while continuously transporting (passing) a steel strip unwound in a refining process, for example, a processing line after cold rolling. Had been The reason why the process is performed in the processing line after cold rolling is that the inspection can be performed immediately before the product is shipped, so that the shipping decision can be made.In other words, the emphasis was on quality assurance of the final product, and the surface generated in the cold rolling process etc. This is to enable detection of defects and the like.

[0003] A steel sheet having a predetermined defect or more is treated as a scrap material.

[0004]

However, after the cold rolling, the flow of the logistics is divided depending on the type of plating method and the like, so that it becomes necessary to install a flaw detector for each corresponding cold rolling processing line. This will increase costs. It is also conceivable to install a flaw detector on the exit side of the cold rolling mill before being divided into each processing line, but it is difficult to achieve a detection reaction by the flaw detector because the transport speed of the cold-rolled steel sheet is too fast. .

On the other hand, defect inspection in the production of hot rolling is conventionally sufficient by conducting a survey from a hot-rolled product for quality assurance. The necessity and advantage of conducting defect inspections were not particularly pointed out. (This is because until recently, flaw detection methods that enable high-precision full-width, full-length, high-speed inspection of hot-rolled steel sheets were not provided until recently. Also play a role). However, the demand for more efficient and trouble-free operation of hot-rolled steel sheets has been increasing among consumers, and a means has been provided to eliminate defective parts by full inspection instead of probable guarantee. Is considered desirable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method of manufacturing a steel sheet in which a defect of the steel sheet is found at an early stage and a countermeasure for removing the defective portion can be easily established. And

[0007]

Means for Solving the Problems In order to solve the above problems, the invention according to claim 1 relates to a method for manufacturing a hot-rolled steel sheet or a cold-rolled steel sheet with respect to a hot-rolled steel sheet after hot rolling. Continuous inspection of defects while transporting hot-rolled steel sheet,
The position of the detected internal defect is recorded on the hot-rolled steel sheet or in the steel sheet information, and downstream from the flaw detection position, a method for manufacturing a steel sheet, comprising: removing a defect-containing portion of the steel sheet based on the record. To provide.

It is preferable that the flaw detection is performed in the pickling step in a facility having a pickling step after hot rolling, in contrast to the structure described in the first aspect. Further, it is preferable that the shape of the hot-rolled steel sheet at the position where the flaw detection is performed is corrected to be flat. Preferably, the flaw detection is performed by an ultrasonic flaw detector.

Next, the invention as set forth in claim 2 is directed to a manufacturing facility for hot-rolled steel sheets or cold-rolled steel sheets, in which a process equipment for processing hot-rolled steel sheets after hot rolling is provided. An object of the present invention is to provide a steel plate manufacturing facility comprising: a flaw detection device for flaw detection of a defect; and a marking device for marking a steel sheet surface at a defect position based on a signal from the flaw detection device.

[0010] Next, a third aspect of the present invention provides a defect removing device for removing a marked steel plate portion downstream from the installation position of the marking device. It is characterized by having.
Next, the invention described in claim 4 detects defects of the hot-rolled steel sheet during transportation to the process equipment for processing the hot-rolled steel sheet after hot rolling in the manufacturing equipment of the hot-rolled steel sheet or the cold-rolled steel sheet. A flaw detector is provided, and recording means for recording defect position tracking information on the steel sheet based on a signal from the flaw detector, and a steel sheet based on the defect position tracking information from the recording means downstream from the flaw detector installation position. And a defect removing device for removing a defect-containing portion.

Although there are many types of defects in steel sheets, extrinsic defects that occur after the completion of hot rolling include abrasions, indentations,
It is limited to surface defects such as biting of dust or discoloration, and can be detected only by surface inspection after cold rolling (annealing). Therefore, the flaw inspection for a steel sheet in a hot-rolled steel sheet can be sufficiently substituted for the flaw detection after cold rolling. The defects targeted by the present invention include internal defects due to inclusions and the like, inclusions such as slivers, scabs, scale flaws, and gouges, or inclusions including inclusions (including iron oxide). Mainly refers to surface defects that are included. Although all of these defects can be detected by the method of the present invention, it goes without saying that the inspection may be limited to a specific defect. It is needless to say that an object that can be detected even on a surface flaw or the like may be a target.

Based on such knowledge, the present invention detects defects in a hot-rolled steel strip between hot rolling and cold rolling before cold rolling, and records defect position information. . This allows for one-site focused flaw detection,
Internal defects and surface defects such as most inclusions can be detected and recorded. In addition, between the hot rolling step and the cold rolling step, there is usually a pickling step of a hot-rolled steel sheet. In this pickling step, the conveying speed of the steel sheet is controlled by a hot rolling step or a cold rolling step. In view of the fact that the transfer speed is slower than the transfer speed and the degree of freedom of the transfer speed is relatively large, the pickling step is preferable as the installation position of the flaw detector. Furthermore, if the flaw detection device is configured to perform flaw detection in water, that is, to perform flaw detection in water, the entrance side of the pickling tank is suitable because the steel plate immersed in water does not need to be dried.

Further, by correcting the shape of the steel plate to be flat prior to the flaw detection, the flaw detection is continuously performed on the flat steel plate, so that the detection accuracy over the entire width is improved. In addition, since the scale and deposits on the brittle outermost surface of the hot-rolled steel strip usually fall off by a forcing means such as a tension leveler, there is also an effect that foreign matter is less likely to be deposited on a water tank for flaw detection. Further, when the flaw detection is performed in a state where the tension is applied, the flatness of the steel plate at the time of the flaw detection is further improved, and the fluctuation of the pass line hardly occurs, so that the detection accuracy is further improved.

Further, as a flaw detector capable of continuously detecting a steel sheet (steel strip) that is rewound and continuously conveyed over the entire width, there are a flaw detector using a leakage magnetic flux method and a flaw detector using ultrasonic waves. Conceivable. However, despite the fact that the hot-rolled steel sheet is thicker than the cold-rolled sheet,
When the steel sheet becomes thicker, the ratio of (defect cross-sectional area / steel cross-sectional area) becomes smaller, and it becomes difficult for magnetic flux to leak to the surface. In addition, since the leakage magnetic flux attenuates rapidly in inverse proportion to the distance from the surface of the steel sheet, it is necessary to control the vertical fluctuation of the pass line of the steel sheet to within ± 0.1 mm. Must be controlled within 0.5 mm, and it is difficult to apply continuous flaw detection in a steel sheet being transported, particularly in a state where the transport speed is high. Further, there is a problem that there are many noise factors.

For this reason, the flaw detection for the hot-rolled steel sheet may be made thicker, and in the case of the non-contact type, the gap between the steel sheet surface and the detecting portion can be made wider than the leakage magnetic flux method. An ultrasonic flaw detector is preferred. Here, examples of the ultrasonic flaw detection apparatus include a plate wave UT method, a focused beam UT method, and a reflection type flaw detection method in a transmission type arrangement (hereinafter, also referred to as an ultrasonic line sensor).

The plate wave UT method detects a flaw by rolling a tire-type acoustic probe (detection unit) into contact with the surface of a steel sheet, but has a dead zone in the thickness direction and is a contact type. The higher the transport speed of the steel sheet, the more disadvantageous it is that the contact pressure of the tire on the surface needs to be adjusted or the tire bounces. Also, there is a fear that the tires burst.

In this regard, the focused beam UT method and the ultrasonic line sensor do not have the above-mentioned problem because the inspection is performed in a non-contact manner. That is, the influence of the pass line fluctuation when the steel sheet is conveyed is small and advantageous. . Here, the focused beam UT method is used for defect detection of a thick plate or a welded part, and the theory has been established. However, as compared with an ultrasonic line sensor, an ultrasonic beam is converged in a point shape (for example, 1 mmφ), so that a number of probes (detection units) corresponding to a flaw detection area is required, and the number of parts for flaw detection is reduced. As the number increases, the flaw detection efficiency decreases. Another drawback is that a dead zone is formed immediately below the steel sheet surface.

In view of the above, of the ultrasonic flaw detector, the ultrasonic line for performing the reflection type flaw detection in a non-contact and transmissive arrangement (the transmission section and the reception section are interposed between steel plates) in the detection section. Those using a sensor are preferable. Here, the configuration and principle of the ultrasonic line sensor are disclosed by the present inventors in Japanese Patent Application Laid-Open No. Hei 7-253414, Japanese Patent Application No. 9-240932, and the like. A band-like ultrasonic beam is transmitted, and the beam is received by a receiving unit including a plurality of rectangular ultrasonic transducers arranged in the width direction of the band. That is, a line-focus type transmission array probe (transmission unit) with the steel strip conveyed in between
And the line focus type receiving array probe (receiving unit) are arranged in an opposed arrangement (the direction of the arrangement is the width direction of the test material), and an internal defect caused by the ultrasonic wave transmitted from the transmitting array probe. By receiving the reflected wave by the receiving array probe arranged opposite to the transmitting array probe, the internal defect of the test material is detected without the dead band immediately below the front and back surfaces (see FIGS. 3 and 4). The reflection type flaw detection in the transmission type arrangement is performed by transmitting a 0.5 round-trip transmitted wave T1 transmitted from the transmission array probe and arriving at the reception array probe by reciprocating 0.5 times of the test material, and the test material approximately 1.5 times. The reflected waves F1 and F2 from the defect appearing between the 1.5-reciprocal transmitted wave reciprocating and arriving at the receiving array probe are extracted by a gate circuit. This is to detect internal defects (see FIG. 5).

Further, since the line sensor has a wide range in which a single detecting section can detect a flaw, it is preferable for detecting a steel sheet being conveyed. Note that the flaw detection by the ultrasonic flaw detector is preferably performed in a liquid in order to maintain good acoustic coupling between the ultrasonic probe and the steel plate, that is, to increase detection accuracy.

The present invention also relates to a process from the hot rolling to before the cold rolling (after hot rolling in the case of producing a hot-rolled steel sheet), that is, in the upper process and before the distribution is divided, Defects are detected at the stage of the rolled steel sheet. Therefore, in order to detect internal defects and surface defects at an early stage, it is not necessary to remove a steel plate portion which becomes a defective portion at the final stage at an early stage and perform unnecessary cold rolling.

Further, by performing flaw detection for a defect before cold rolling where each cold-rolled steel sheet is diverted, even if the above-mentioned defective part is removed in a processing line after cold rolling based on the record of the defect, There is no need to separately install a flaw detector in a plurality of cold-rolled steel sheet processing lines after cold rolling.

[0022]

Next, a first embodiment of the present invention will be described with reference to the drawings. The present embodiment relates to a facility for manufacturing a cold-rolled steel sheet. The equipment, from the upstream side,
Blast furnace-Converter-(Degassing equipment)-Continuous casting equipment-(Slab storage)-Hot rolling-Pickling process of hot rolled steel sheet-Cold rolling process-Continuous annealing process-Temper rolling process-Refining process The processing line after the cold rolling (continuous annealing step-temper rolling step-refining step) is divided into a plurality of processing lines according to the final product. The processing line after the cold rolling is an example, and depending on the type of the cold rolled steel sheet, for example, there may be steps such as box annealing, secondary cold rolling, and a plating step.

In the pickling step of the hot-rolled steel sheet, for example, as shown in FIG. 1, the payoff reel 1, the shear 2, the welding machine 3, the entrance looper 4, the entrance bridle roll 5, the tension leveler 6 are arranged from the upstream side. Outlet bridle roll 7, pickling tank 8, rinsing tank 9, drying device 10, outlet looper 11,
Each equipment is arranged in the order of the trimmer 12, the shearing device 13 (defect removing device), and the coiler 14, and the hot-rolled hot-rolled steel sheet is rewound to perform the pickling treatment.

In this embodiment, as shown in FIGS. 2 and 6, between the tension leveler 6 and the outgoing bridle roll 7 on the entrance side of the pickling tank 8, an ultrasonic flaw detector 20 and a marking are provided. An apparatus 50 is provided. Here, the tension leveler 6 has a function of cracking the surface of the hot-rolled steel sheet 15 to promote the cleaning with an acid in the pickling tank 8, and corrects the shape of the hot-rolled steel sheet 15 before flaw detection. It has the function of flattening, and also serves as shape correction means for flaw detection. Further, the bridle rolls 5 and 7 in front and behind the flaw detector 20 have a function of applying a tensile force in the longitudinal direction to the hot-rolled steel sheet 15 at the flaw detection position and correcting the steel plate portion at the flaw detection position to be flat. For shape correction. That is, the tension leveler 6 and the bridle rolls 5 and 7 form a part of the flaw detection equipment together with the ultrasonic flaw detection apparatus 20.

The configuration of the flaw detection equipment will be described. From the upstream side to the downstream side, the upstream bridle roll 5, the tension leveler 6, the liquid tank 21 containing the water 22, the marking device 50, and the downstream bridle roll. 7 are arranged. In addition, a rust preventive or the like for preventing rust of the hot-rolled steel sheet 15 is added to the water 22 in the liquid tank 21.

On the entry side of the liquid tank 21, a first transport roll 22 is disposed, and the transport path of the hot-rolled steel sheet 15 is controlled by the first transport roll 22 and a second transport roll 23 that is completely submerged in water. Is changed vertically downward, for example, and guided into the water in the liquid tank 21. The transport direction of the hot-rolled steel sheet 15 immersed in water is bent in the horizontal direction by the second and third transport rolls 23 and 24 that are completely immersed in water, and subsequently the third transport roll 24 and the upper surface of the water are bent upward. The transport direction is bent in the vertical direction by the third transport roll 24 located, and the third transport roll 24 exits the water, that is, from the liquid tank 21. Subsequently, the hot-rolled steel sheet 15 is guided to the downstream bridle roll 7 side, that is, the pickling tank 8 side by the fourth transport roll 25. Here, the reason why the first and fourth transport rolls 22 and 25 are each composed of two rolls is that the height of the transport path of the hot-rolled steel sheet 15 is once increased and the first and fourth transport rolls 22 and 25 are guided into the liquid tank 21. It is possible, not necessarily two.

An ultrasonic line sensor 26 as a detection unit of the ultrasonic flaw detector 20 is disposed between the second transport roll 23 and the third transport roll 24. The flaw detection method of the ultrasonic line sensor 26 is disclosed in Japanese Patent Laid-Open No. 7-25341.
As shown in FIG. 3 which is a conceptual diagram based on the principle described in Japanese Patent Publication No. 4 and the like, a transmitting unit 26a and a receiving unit 26b each formed of a one-dimensional array type probe sandwich a hot-rolled steel plate 15 therebetween. The hot-rolled steel sheets 15 are arranged to face each other in the thickness direction. In FIG. 3, reference numeral 27 indicates a line focus beam, and reference numeral 28 indicates a reception beam.

The ultrasonic line sensor 2 having the above configuration
As shown in FIG. 4, a plurality of transmitters 26 a and receivers 26 b are continuously arranged along the width direction of the hot-rolled steel sheet 15, and the arranged transmitters 26 a and receivers 26 b are supported by the U-shaped frame 30. ing. Accordingly, it is possible to detect a defect in the entire width of the hot-rolled steel sheet 15 conveyed by a small number of detecting units. Here, the arrangement of the transmission units 26a and the reception units 26b in a staggered manner enables inspection of the entire width direction of the hot-rolled steel sheet 15 while avoiding unnecessary interference between the adjacent sensors 26. That's why. Note that the receiving unit 26b may be disposed on the upper side, and the transmitting unit 26a may be disposed on the lower side, or may be disposed upside down as appropriate.

Each sensor 26 is connected to the flaw detector main body 31. In the flaw detector main unit 31, the 0.5 reciprocating transmitted wave T1 transmitted from the transmitting unit 26a and reciprocating the hot-rolled steel plate 15 by 0.5 in the thickness direction to reach the receiving unit 26b and the hot-rolled steel plate 1
The gate circuit extracts the reflected waves F1 and F2 from the defect appearing between the transmitted wave 5 and the 1.5 reciprocating transmitted wave that reaches the receiving unit 26b by reciprocating approximately 1.5 in the thickness direction (see FIG. 5). If the level is equal to or higher than the predetermined level, it is determined that there is a defect reflected wave, and an internal defect is detected. And the flaw detector main body 3
1 supplies the detected defect position information to the marker controller 50a of the marking device 50.

Here, between the third transport roll 24 and the fourth transport roll 25, the steel plate 15 is located at a position close to the water surface.
A ringer roll 32 serving as a liquid squeezing means for squeezing water adhering to the ringer roll is provided.
Liquid receiver 33 for receiving the liquid falling from the hot-rolled steel sheet 15 between the water and the water surface to prevent the liquid from directly colliding with the water surface.
Is arranged. The liquid receiver 33 may be above the water surface 22a, or may be in contact with the water 22 in the liquid tank 21. Also, the water received in the liquid receiver 33 is gently transferred to the liquid tank 2.
It may be returned to the water 22 in the container 1, or may be discharged to the liquid tank 21. Further, in FIG. 2, a container-like liquid receiver 33 is shown, but a flat plate member such as a shielding plate may be used.

The marking device 50 includes a marker controller 5
0a and a defect position marker 50b. The marker controller 50a supplies a marking command to the defect position marker 50b based on the defect position information from the flaw detector main body 31, and makes a mark on the surface of the hot rolled steel plate 15 at the defect position with the defect position marker 50b. The position of the defect is recorded on the surface of the hot-rolled steel sheet 15. It is to be noted that the marking applied to the surface of the hot-rolled steel sheet 15 may be changed according to the defect level. Also,
Marking is not limited to engraving, and may be performed by adhesion of paint, but in the present embodiment, since flaw detection and marking processing are performed before pickling processing, engraving is easier than paint. The mark is reliably prevented from disappearing by pickling, which is good.

The shearing device 13 located in front of the coiler 14 also serves as a defect removing means, and as shown in FIG.
Is provided. The mark reading device 13c continuously and non-contactly inspects the surface of the conveyed hot steel plate 15 and supplies mark reading information to the shear controller 13b when an engraved mark is detected. The shear controller 13b supplies a shear command to the shear 13a based on the input mark reading information, and shears the hot-rolled steel sheet 15 at the defect-containing position.

However, when the mark reading device 13c continuously detects the mark at a pitch equal to or less than the predetermined interval, the mark reading device 13c does not output the mark reading information during the continuation, and when the mark is not detected, The mark reading information is supplied to the shear controller 13b. This processing is performed by the shear controller 13b.
It may be done on the side. Alternatively, when the defect position information is continuously input by the marking device 50, the marking process is stopped during the continuous input, and the hot-rolled steel sheet 15 is stopped when the continuous input of the defect position information is interrupted. May be configured to make a mark on the surface of the substrate, and to make a mark only before and after the position containing the internal defect.

In the above-described cold-rolled steel sheet manufacturing equipment, when pickling is performed on the hot-rolled steel sheet 15 after hot rolling, internal defects are continuously detected before the pickling. In other words, the hot-rolled steel sheet 15 before hot-rolling and before pickling is conveyed in a state where tension is applied in the longitudinal direction by the upstream bridle roll 5 and the downstream bridle roll 7, and the liquid tank 2
Before being immersed in the water 22 in 1, it is continuously flattened by the tension leveler 6. Subsequently, the hot-rolled steel sheet 15 is immersed in the water in the liquid tank 21 by the transport rolls 22 to 25, and while moving horizontally in the water, the line sensor 26 of the transmission type ultrasonic flaw detector 20 continuously detects internal defects. Inspection is performed, and a mark is made on the surface of the hot-rolled steel sheet 15 at the defect position to record the defect portion. Then, the hot rolling coiler having no defect can be obtained by being sheared at the defect position by the shearing device 13 after the pickling. Here, the internal defect usually exists continuously for a predetermined length in the longitudinal direction of the steel sheet.

Moreover, in the present embodiment, despite the fact that the internal defect is detected at one location, the target defect can be almost detected and removed before the cold rolling process. Unnecessary processing, that is, performing cold rolling on a steel sheet that is determined to be a scrap material at the stage of the final cold rolling refining process can be avoided. Further, since flaw detection for internal defects is performed at one location, there is no need to provide flaw detection devices individually for a plurality of cold rolling processing lines.

Here, in the above embodiment, a defect equal to or greater than a predetermined value is detected, a mark is formed on the surface of the hot-rolled steel sheet 15, and the hot-rolled steel sheet 15 is removed based on the mark. In the case where the marks are different depending on the level, only a portion having a mark indicating a defect of a predetermined level or more may be removed by the shearing device 13, and the minor defect level may not be removed.

In this case, the portion with the stamp is also cold-rolled to form a cold-rolled steel sheet, which is shipped as a cold-rolled coil. Since the defective portion can be easily recognized, the defective portion can be removed and used at the shipping destination. Further, the cold rolled steel sheet of the defective portion may be used at a place where the conditions are not severe at the shipping destination.

Further, in the above embodiment, the surface of the hot-rolled steel sheet 15 is once marked (marked), and the defective portion is removed by the shearing device 13 based on the mark. However, the present invention is not limited to this. For example, a configuration may be employed in which the defect position tracking information is directly supplied from the flaw detection apparatus main body 31 to the shear controller 13b, and the defect portion is removed by the shearing device 13 based on the tracking information.

In this embodiment, in order to prevent the detection accuracy from deteriorating due to air bubbles, the hot-rolled steel sheet 15 enters the water perpendicular to the water surface and the generation of air bubbles when the hot-rolled steel sheet 15 is immersed. Hot-rolled steel sheet 15
The water adhering to the water is squeezed by the ringer roll 32 in the vicinity of the water surface, and the liquid is reliably dropped from the ringer roll 32 installation height and received by the liquid receiver 33 to avoid the dropped liquid from directly colliding with the water surface. In addition, the generation of bubbles due to the liquid falling from the hot-rolled steel plate 15 above the water surface is prevented. In addition, since the falling liquid is received by the liquid receiver 33, the ringer roll 32 is not always necessary. However, in order to prevent water from being transported to the downstream process together with the hot-rolled steel sheet 15, the drop height of the liquid is adjusted. By making the height lower, the effect of reducing the splash of the liquid that has collided with the liquid receiver 33 is obtained.

In the flaw detection using ultrasonic waves according to the present embodiment, since the detection unit 26 of the ultrasonic flaw detection apparatus 20 employs a non-contact and transmission type reflection type flaw detection method,
By eliminating the dead zone just below the surface, it is possible to detect defects of the hot-rolled steel sheet 15 being conveyed at a predetermined speed while securing predetermined detection accuracy, and by using the line sensor 26, the width direction of the hot-rolled steel sheet 15 can be detected. Even when the entire width is to be inspected, the number of the detection units (sensors 26) can be reduced.

Further, the detection accuracy is improved by performing the flaw detection in water, and the generation of bubbles due to the hot-rolled steel sheet 15 entering the water and moving upward from the water surface is minimized. Erroneous detection is prevented, and the detection accuracy is further improved. Since the transport rolls that are in contact with water are all submerged in water, the entrapment of bubbles due to the rotation of the transport rolls is reduced. Here, the flaw detector 20
Is not limited to the vertical direction, so that the transport path of the flaw detection position of the hot-rolled steel sheet 15 in water may not be horizontal. However, from the viewpoint of preventing adverse effects of air bubbles, it is preferable to detect flaws at the position farthest from the water surface.

Further, before the inspection, the hot-rolled steel sheet 15 is inspected in a state where the steel sheet is straightened and tension is applied.
The hot-rolled steel sheet 15 becomes flatter, and thus, the flaw detection of the defect of the hot-rolled steel sheet 15 is performed with higher accuracy. Here, the tension leveler 6 and the bridle rolls 5 and 7 are not necessarily required, but without the tension leveler 6 or the like, the flatness of the hot-rolled steel sheet 15 at the flaw detection position is deteriorated and the detection accuracy is reduced. to degrade. The shape correcting means is not limited to the tension leveler 6, and for example, a temper rolling mill or the like may be used. Also, if the bridle rolls 5 and 7 are manually provided with tension, other known means may be used. In this embodiment, the hot-rolled steel sheet 15 is immersed in water 22 in order to increase the detection accuracy of flaw detection. However, since it is on the entrance side of the pickling tank 8, there is no need for a means for particularly drying the hot-rolled steel sheet 15 after the flaw detection. When the flaw detector 20 is disposed on the entrance side of the pickling tank 8, the tension leveler 6 is usually disposed on the entrance side of the pickling tank 8 as described above, so that the flaw detector 20 is separately provided. It is not necessary to provide a shape correcting means for the purpose. Further, in the pickling step, the inlet side of the pickling tank 8 is the most suitable because the transport speed is the most stable.

By employing such a flaw detection equipment, full width continuous flaw detection becomes possible even under a high-speed sheet passing speed of about 300 to 1000 m / min. In the above embodiment, the water immersion method is used in combination to increase the detection accuracy. However, flaw detection may be performed in the atmosphere. Also, the line sensor 26
Instead, an ultrasonic flaw detector using the focused beam UT method may be employed. However, the number of probes (detection units) increases, which may complicate the device configuration and lower the detection accuracy.

In the above-described embodiment, an example in which flaw detection equipment is provided in the pickling process is described. However, the position between the hot rolling and the cold rolling, that is, the position where the hot-rolled steel sheet 15 is processed is described. If so, the flaw detection equipment and the defect removing device may be provided at other positions such as a trimmer and cold-rolling entrance equipment. Also,
Although the equipment of the present embodiment is a manufacturing equipment of a cold-rolled steel sheet, even when the hot-rolled steel sheet 15 before cold rolling is shipped as a product, the hot-rolled steel sheet from which the defective portion has been removed as described above. 1
5 can be shipped. This allows, for example,
There is no need to separately provide a flaw detection device or a defect removing device for the hot-rolled steel sheet in the refining process for the hot-rolled steel sheet.

In addition, the confirmation of the presence or absence of scratches after cold rolling is as follows.
As before, it may be performed before product shipment. The same applies when shipping as a hot-rolled steel sheet 15. (Example) In the above-mentioned cold rolled steel sheet manufacturing equipment, a steel sheet containing 0.3 inclusions per ton (0.005 per square meter) was inspected by the flaw detection equipment, and as a result, the recognition rate was almost 100%. It was confirmed that defect inclusions could be detected and removed at a ratio of.

Here, when the flaw detection is performed without applying the tension by the bridle rolls 5 and 7, the recognition rate is reduced to about 99.5%. When the tension leveler 6 is not used, the recognition rate is reduced. The rate dropped to about 99.0%. For comparison, a steel sheet containing 0.3 inclusions per ton as in the prior art without a flaw detection equipment in the above pickling process was used in a refining process before product shipment. When a defect was inspected by the flaw detection apparatus 20, the recognition rate of the defect was about 80 to 98% due to reasons such as the inability to distinguish it from electrical noise.

As described above, it can be understood that the defect can be detected with high accuracy by detecting the defect based on the present invention. In addition, it is possible to concentrate at one place and detect it at an early stage, thereby removing an internal defect portion. Next, a second embodiment will be described.
The second embodiment is a manufacturing facility for the hot-rolled steel sheet 15 and has the same apparatus configuration as the first embodiment up to the pickling step, but has a refinement step downstream of the pickling step. Is arranged. That is, blast furnace-converter-(degassing treatment equipment)-
It comprises continuous casting equipment-(slab storage)-hot rolling-pickling process of hot-rolled steel sheet-refinement process.

The other structures, operations and effects are the same as those of the first embodiment. That is, even when the hot-rolled steel sheet 15 is shipped as a product, the defect of the hot-rolled steel sheet 15 can be detected accurately and the defective portion is removed. It can be carried out. The installation of the flaw detection equipment is not limited to the pickling step, and may be separately provided between the pickling step and the refining step.

Next, a third embodiment will be described. In addition, the same reference numerals are given to the same facilities and devices as those in the above embodiments, and detailed description thereof will be omitted. The present embodiment relates to a cold-rolled steel sheet manufacturing facility having the same equipment as the first embodiment, and for example, manufactures a steel sheet for cans having strict quality as a target cold-rolled steel sheet. .

In this embodiment, as shown in FIG. 7, similarly to the first embodiment, a flaw detection equipment including a flaw detector 20 is provided before the pickling tank 8 in the pickling step A of the hot-rolled steel sheet 15. Are located. However, it does not have a marking device or a mark reading device. Instead, the flaw detector main body 31
Supplies the position of the detected internal defect as defect position tracking information to the management computer 51 that manages the entire cold rolling production facility. The management computer 51 records the defect position tracking information as steel sheet information. The management computer 51 also functions as a recording unit.

Here, in FIG. 7, reference numeral B denotes a cold rolling step, reference numeral C denotes an annealing step, reference numeral D denotes a tempering / refining step,
Symbol E represents a cold rolling processing line. Also,
Reference numeral 52 denotes a cold rolling mill, reference numeral 53 denotes a continuous annealing furnace, and reference numeral 54 denotes a temper rolling mill. Management computer 5
1 tracks a defect position through a cold rolling process B and an annealing process C, and appropriately sends the defect position tracking information to a defect removal shear controller 56 provided in a refining process D.
It can be supplied.

In the refining step D, as in the conventional case, there is a surface inspection chamber 55 for performing an inspection before forming a cold-rolled coil as a product. An inspection is performed to determine whether there is any flaw. If the inspection results in a defect, the surface defect information is supplied to the shear controller 56. And, like shearing the position just before the defective position,
A shear command is supplied from the shear controller 56 to the shear 57,
The cold-rolled steel plate 57 is configured to be sheared by the shear 57 in front of the defective position.

In this embodiment, as described above, the defect position tracking information on the internal defect obtained during the pickling of the hot-rolled steel sheet 15 is transmitted to the shear controller 56 of the refining step D via the management computer 51. As a result, the cold-rolled steel sheet 58 is sheared not only at the defective position such as the surface flaw but also immediately before the defective position due to the internal defect. As described above, in the present embodiment, since the internal defects are detected in one place in a concentrated manner, it is not necessary to provide flaw detection equipment for detecting the internal defects for each refining process of each cold rolling processing line E. Nevertheless,
It is possible to reliably remove the cold-rolled steel sheet 58 at the internal defect.

As in the first embodiment, in the pickling step A of the hot-rolled steel sheet 15, the surface of the steel sheet 15 at the position of the internal defect is engraved with a marking device, and the surface is inspected in the surface inspection room. Internal defects as well as defects may be detected. Since the engraving is performed, the internal defect of the steel sheet can be detected with a detection rate equal to or higher than the surface defect.

Further, each tracking information or each marking may be shipped as a product, and the defective portion may be removed by the processor on the basis of the information.

[0056]

As described above, when the present invention is employed, although the internal defects of the cold-rolled steel sheet and the hot-rolled steel sheet can be accurately detected, the flow is divided into a plurality of cold rolling processes after the cold rolling. Since it is performed before, the internal defects can be detected in one place in a concentrated manner, and there is an effect that the steel plate at the defective portion can be efficiently removed.

Moreover, since the internal defect is detected at the stage of the hot-rolled steel sheet, there is an effect that unnecessary cold-rolling treatment is reduced if the defective steel sheet is removed at an early stage. Further, even in the case of shipping at the stage of a hot-rolled steel sheet, sufficient quality control can be performed in a cold-rolled steel sheet manufacturing facility.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing equipment for a pickling step according to an embodiment of the present invention.

FIG. 2 is a view showing a flaw detection equipment according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a line sensor according to the embodiment of the present invention.

FIG. 4 is a diagram related to an array of line sensors according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating the principle of a line sensor.

FIG. 6 is a conceptual diagram for explaining defect removal according to the embodiment of the present invention.

FIG. 7 is a conceptual diagram for explaining defect removal according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 5 Inlet bridle roll 6 Tension leveler 7 Outlet bridle roll 13 Shearing device 13a Shear 13b Shearing controller 13c Mark reading device 15 Hot-rolled steel plate 20 Flaw detector 21 Liquid tank 22 Water 22-25 Transport roll 26 Line sensor (detection unit) 31 flaw detection device main body 50 marking device 50a marker controller 50b defect position marker 51 management computer 55 surface inspection room 56 shear controller 57 shear 58 cold-rolled steel plate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidenori Miyake 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Chiba Works, Ltd. (72) Inventor Kazuhisa Hamami 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Inside Kawasaki Steel Corporation Chiba Works (72) Inventor Kazutaka Takada 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside Kawasaki Steel Research Institute (72) Inventor Yukio Obata 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Corporation Chiba Works (72) Inventor Hideo Kugminato 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Corporation Chiba Works F-term (reference) 2F068 AA49 BB05 BB23 CC15 FF11 FF12 JJ22 KK12 KK15 LL04 2F069 AA60 BB19 BB34 CC06 GG04 GG09 GG78 JJ13 KK08 QQ14 2G047 AA07 AB04 AD11 BA02 BB01 BB06 BC03 CB01 EA13 EA16 GB02 GE02

Claims (4)

[Claims] When producing a hot-rolled steel sheet or a cold-rolled steel sheet,
The hot-rolled steel sheet after hot rolling is continuously inspected for defects while transporting the hot-rolled steel sheet, and the position of the detected internal defect is recorded on the hot-rolled steel sheet or in the steel sheet information. A method for manufacturing a steel sheet, wherein a portion containing a defect of the steel sheet is removed based on the record at a position downstream of the position. 2. In a manufacturing facility for a hot-rolled steel sheet or a cold-rolled steel sheet, a process facility for processing a hot-rolled steel sheet after hot rolling is provided.
A steel plate manufacturing facility comprising: a flaw detector for flaw detection of a hot-rolled steel sheet being conveyed; and a marking device for marking a steel sheet surface at a defect position based on a signal from the flaw detector. 3. The steel plate manufacturing facility according to claim 2, further comprising a defect removing device that removes a marked steel plate portion downstream from an installation position of the marking device. 4. In a facility for manufacturing a hot-rolled steel sheet or a cold-rolled steel sheet, a process equipment for processing a hot-rolled steel sheet after hot rolling is provided with a flaw detection device for detecting flaws in the hot-rolled steel sheet being conveyed. Recording means for recording defect position tracking information on a steel sheet based on a signal from the flaw detection device; and a defect for removing a defect-containing portion in the steel sheet based on the defect position tracking information from the recording means downstream of the flaw detection device installation position. A steel plate manufacturing facility, comprising: a removing device.