JP4400166B2 - Method for removing non-metallic inclusion defect in metal strip - Google Patents

Description

  The present invention relates to a method for removing a defective portion based on defect information obtained by a flaw detection apparatus that continuously detects defects inherent in the metal band while conveying a band-shaped metal band such as a steel plate. The present invention can be applied to both a coil and a sheet in which the metal strip is loaded.

  Conventionally, defects inside a metal band such as fine non-metallic inclusion defects are detected, and a pass / fail judgment is made so that defective products are not shipped to customers.

  As a typical flaw detection apparatus that detects defects such as non-metallic inclusions in the metal band online, a flaw detection apparatus using a leakage magnetic flux method and a flaw detection apparatus using ultrasonic waves can be given.

  By the way, in the leakage magnetic flux method, when the metal band becomes thick, it becomes difficult for the magnetic flux to leak to the surface, and when it is applied to a steel plate that is a kind of metal band, it is impossible to inspect the plate thickness of about 0.5 mm or more. Has been. Moreover, since the magnetic flux leakage attenuates abruptly in inverse proportion to the distance from the steel plate surface, it is necessary to control the vertical fluctuation of the conveyance path line of the steel plate to within ± 0.1 mm and the gap between the detector and the steel plate surface. Must be controlled within 0.5 mm, and it is difficult to apply it to steel plates being transported, especially for continuous flaw detection with a high transport speed. There is also a problem that there are many noise factors.

  Below, a steel plate is illustrated and demonstrated as an object metal strip. As an example of the flaw detection apparatus, an example in which an ultrasonic method that can be easily applied even when the steel plate is thicker than the leakage magnetic flux method will be described. However, the present invention is widely applicable to metal bands in general, and it goes without saying that the flaw detection method may be a leakage magnetic flux method or the like.

  Here, examples of the ultrasonic flaw detection apparatus include a plate wave UT (Ultrasonic Testing) method, a focused beam UT method, a reflection type ultrasonic flaw detection method in a transmissive arrangement (hereinafter also referred to as an ultrasonic line sensor), and the like. .

  In the plate wave UT method, a tire type acoustic probe (detection unit) rolls and contacts the surface of the steel sheet to detect flaws, but has a dead zone in the thickness direction and is a contact type. The higher the conveyance speed of the steel sheet, the more disadvantageous it is, for example, that the tire contact pressure needs to be adjusted and the tire bounces. There is also a concern that the tires burst.

  In this respect, the focused beam UT method and the ultrasonic line sensor are advantageous in that they do not have the above-mentioned problems because they perform non-contact inspection, and are less affected by fluctuations in the pass line when the steel sheet is conveyed. Here, the focused beam UT method is used for defect inspection of thick plates and welds, and the theory has been established. However, compared with an ultrasonic line sensor, the ultrasonic beam is converged in a dot shape (for example, 1 mmφ), so the number of probes (detection units) corresponding to the flaw detection area is required, and the number of parts for flaw detection is small. As the number increases, the flaw detection efficiency deteriorates. In addition, there is a drawback that a dead zone is formed directly under the steel plate surface.

  For this reason, as an ultrasonic flaw detector that detects fine defects (non-metallic inclusions) inside a steel plate, the detection unit is non-contact and transmissive arrangement (the transmission unit and the reception unit are arranged across the steel plate) And using an ultrasonic line sensor that performs reflective flaw detection is suitably applied (see Patent Document 1 and the like).

  By the way, the non-metallic inclusion defect is particularly problematic in that the ratio of aluminum oxide is large. If the ratio of aluminum oxide is large, the angular shape remains almost unchanged even during slab solidification, and since the deformation resistance is large, it is not deformed even by hot rolling. Remaining as it is on the surface layer causes press cracks and the like.

  Here, the configuration and principle of the ultrasonic line sensor are those disclosed by the present inventors in Patent Document 2 and Patent Document 3, etc., and a band-shaped ultrasonic beam focused in one direction is transmitted from the transmission unit. The beam is received by a receiving unit composed of a plurality of strip type ultrasonic transducers arranged in the width direction of the steel plate. That is, the line focus type transmission array probe (transmission unit) and the line focus type reception array probe (reception unit) are opposed to each other across the steel plate to be conveyed (the direction of arrangement is the plate width direction of the steel plate as the test material). The internal defects of the test material are detected by receiving the reflected waves from the internal defects generated by the ultrasonic waves transmitted from the transmitting array probe by the receiving array probe arranged opposite to the transmitting array probe. The detection is performed without a direct sneaking zone (see FIGS. 3 and 4).

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

  As shown in FIG. 2, the ultrasonic flaw detector 10 is disposed between the tension leveler 3 and the exit side bridle roll 5. The tension leveler 3 corrects and flattens the plate shape of the steel plate 1 before flaw detection. Further, the bridle rolls 2 and 5 in front of and behind the ultrasonic flaw detector 10 apply a tensile force in the longitudinal direction (corresponding to the conveying direction) to the steel plate 1 at the flaw detection position to flatten the plate portion at the flaw detection position. It has a function and also serves as a shape correction means for flaw detection.

  A first transport roll 11 is arranged on the entrance side of the water tank 20 of the ultrasonic flaw detector 10, and the transport path of the steel plate 1 is formed by the first transport roll 11 and the second transport roll 12 that is completely submerged in water. For example, it is changed vertically downward and guided into the water in the water tank 20. In addition, the water 21 in the water tank 20 may be added with a rust preventive agent or the like for preventing the steel plate 1 from being rusted.

  The steel sheet 1 immersed in the water is bent in the horizontal direction by the second and third transfer rolls 12 and 13 that are fully immersed in water, and then positioned above the third transfer roll 13 and the water surface. The fourth transport roll 14 is bent in the transport direction in the vertical direction and exits from the water tank 20. Subsequently, the steel plate 1 is guided to the downstream bridle roll 5 side by the fourth transport roll 14.

  An ultrasonic line sensor 22 that is a detection unit of the ultrasonic flaw detector 10 is disposed between the second transport roll 12 and the third transport roll 13. The flaw detection method of the ultrasonic line sensor 22 is based on the principle described in Patent Document 2 and the like. As shown in FIG. 3 which is a conceptual diagram, the transmitter 22a and the receiver each composed of a one-dimensional array probe are used. The portion 22b is disposed opposite to the steel plate 1 with the steel plate 1 interposed therebetween. In FIG. 3, reference numeral 23a indicates a line-focused transmission ultrasonic beam, and reference numeral 23b indicates a reception ultrasonic beam.

  As shown in FIG. 4, a plurality of ultrasonic line sensors 22 (22a, 22b) configured as described above are continuously arranged and arranged along the width direction of the steel sheet 1, and the transmitter 22a and the receiver are arranged. 22b is supported by a line sensor mount 25 which is a U-shaped frame. Thereby, it is possible to detect the defect of the full width of the steel plate 1 with a small number of detection units. Here, the transmission units 22a and the reception units 22b are arranged in a staggered manner, so that the entire surface in the width direction of the steel sheet 1 can be inspected while avoiding unnecessary interference between the adjacent ultrasonic line sensors 22. It is to do.

  Each ultrasonic line sensor 22 is connected to a flaw detection signal processing device 24. When the detection signal is equal to or higher than a predetermined level, the inclusion defect is detected as a defect reflected wave.

By adopting the above flaw detection equipment, full-width continuous flaw detection is possible even under high-speed conveyance at a conveyance speed of about 300 to 1000 m / min. In the above description, the water immersion method is employed to increase the detection accuracy, but flaw detection may be performed in the air. Further, an ultrasonic flaw detector using the focused beam UT method may be employed instead of the ultrasonic line sensor.
Japanese Unexamined Patent Publication No. 2000-210717 JP 7-253414 A Japanese Patent Laid-Open No. 11-83815

  By the way, the criteria for pass / fail judgment that has been applied in the above-described flaw detection equipment are not so clear and are trial and error, and are not non-metallic inclusions so as not to ship defective products to customers. Detection was also determined as non-metallic inclusions. For this reason, there is a tendency that a steel plate, which is originally a good product, is determined as a defective product.

  For example, the steel sheet for DRD cans (Drawn and Redrawn Can) used in tuna cans is subjected to secondary cold rolling with a rolling reduction of 20 to 30% after primary cold rolling and annealing, resulting in high strength and thickness of 0.170 mm. Finish as a steel sheet for ultra-thin cans. That is, twice rolling and DR (double cold-reducing) rolling are performed, and the steel sheet for the high strength and ultrathin can is finished by a twice pressing method. In this iron making method, for example, even if one can out of a steel plate of 500 kg (the weight of one DRD can is about 22 g), if a defect is detected, all the lots become scrap. . The lot weight is about 10 tons, and when it comes to scrap in lot units, the economic and delivery time disadvantages are very large.

  The present inventors sampled the detection of the various defects described above, and as a result of repeating various analysis investigations including microscopic observation of the cross section of the detection unit, the position detected as the defect is non-metallic intervening. In addition to physical defects, it was clarified that various pseudo signals were detected as defects, or harmless defects were detected.

In particular, center cracks (holes) and large dents on the surface of the steel sheet that are harmless in the final process due to re-rolling in the downstream process, etc., coincide with the longitudinal direction of the metal strip. Defect signal that is continuously detected in the rolling direction and the 90-degree rolling direction that coincides with the width direction of the metal strip, that is, a defect signal that is continuously detected in the longitudinal direction by a predetermined length or more, illustratively 0.1 to several meters, and / or It becomes a defect signal that is continuously detected in the width direction by a predetermined length or more, for example, 1 to several tens of millimeters continuously, and apparently increases the defect density (pieces / m ² ) in the metal band despite harmlessness. It becomes defective and leads to downgrade, diversion or scrapping. For this reason, there is a need to meet the delivery date by, for example, expediting arrangements for manufacturing slabs again. In addition, the process disruption becomes severe, and further, the impact on the delivery date of other steel sheets that are delayed in the process progress is great, and the economic impact is immeasurable.

  The present invention aims to solve the above-mentioned problems, and when detecting a fine non-metallic inclusion defect with a flaw detection device, the detection result that is not a non-metallic inclusion is erased, and the determination agreed with the customer The metal band that passed the pass / fail judgment process according to the standard is further processed to remove the defective part, that is, the quality of the metal band is improved while correcting the occurrence of excessive rejects and satisfying the customer's required quality. Can be provided.

  The present invention has solved the above problems by a method for removing a defect portion of a nonmetallic inclusion described below.

That is, a non-metallic inclusion defect portion of a metal strip is removed based on development information corresponding to the longitudinal position and width direction position of the defect in the metal strip , and the detected non-metal When the defect signal of the inclusion defect continues in the longitudinal direction and / or the width direction of the metal strip for a predetermined length or more, the defect signal is erased. Otherwise, it is determined as a non-metallic inclusion defect. In the step of editing the defect signal into the development view information, the step of judging the acceptance / rejection of the metal band in comparison with the development plan information and the judgment standard agreed with the customer, In the process of making a rejected product and the pass / fail judgment step, in the case of a pass, the following (A) to (C) any one of the following steps is adopted and processed. Removal method.
(A) A step of marking the position of the corresponding defect, reading the marking mark, removing the corresponding defective portion, and shipping to the customer.
(B) A step of marking and shipping at the position of the corresponding defect and reading the mark of the marking on the customer side or removing the corresponding defective portion based on the development view information.
(C) A step of providing the developed map information to the customer and shipping it, and removing the corresponding defective portion on the customer side based on the developed map information.

  According to the present invention, it has become possible to correct the occurrence of an excessively rejected product, which has been a problem in the conventional detection of non-metallic inclusion defects in a metal strip, and to satisfy the customer's required quality. Furthermore, it has become possible to provide a high-quality metal strip that does not contain harmful non-metallic inclusion defects.

  According to FIG. 1, pass / fail judgment and removal of defective portions of non-metallic inclusion defects of the present invention (unless otherwise noted, non-metallic inclusions are simply referred to as inclusions and non-metallic inclusion defects are simply referred to as inclusion defects). The flow will be described.

In FIG. 1, first, a flaw detection signal from a flaw detection apparatus represented by an ultrasonic line sensor is input and stored in an inclusion determination processing apparatus which is a flaw detection signal processing apparatus of the flaw detection apparatus (110).

In the inclusion determination processing apparatus, the defect signal detected from the stored flaw detection signal is a signal that continues for a predetermined length (αm) or more in the longitudinal direction of the metal band, and / or is a predetermined length (βmm) or more in the width direction. It is determined whether the signal is continuous (120). If so, it is determined that the defect is not an inclusion defect, and the detected defect signal is erased (140). On the other hand, if not, it is determined as an inclusion defect and the subsequent processing is performed.

Here, if it is determined that the defect is an inclusion defect, the defect signal is further edited to be developed view information (150). Specifically, at least the information on the longitudinal position and the width direction position of the defect in the metal band, and preferably the width, length, thickness, thickness direction position of the defect, and the like are edited. More specifically, it may include calculating the defect density (inclusions / m ² ) of inclusion defects in the target metal band.

  The above development map information is stored (accumulated) in the customer database (220).

Next, the pass / fail judgment of the metal strip is performed in comparison with the judgment standard (210) (160). The criterion (210) is a criterion that is pre-registered in the customer database and agreed with the customer, and specifically includes the allowable density of inclusion defects (unit: pieces / m ² ). When the defect density of the inclusion defect exceeds the allowable density, it is judged as rejected (NG), and the metal band is rejected (170).

  On the other hand, if it is acceptable (OK), it is transferred to the final inspection line of the next process as it is.

  In the final inspection line, the flow is divided according to whether the shipment is a coil or a sheet (310).

  First, the case where the shipment form is a sheet will be described. First, development map information corresponding to the sheet already stored in the customer database is provided to the final inspection line (320). In the developed view, the position of the inclusion defect on the sheet is clarified, and at the same time, detailed information such as the size of the inclusion defect is linked.

  Subsequently, based on the development information, defect marking such as engraving is performed at the position of the inclusion defect on the sheet (330). The marking position is a position where a defect is detected or an end portion on the sheet corresponding to the same position, and the same applies to a coil described later. Then, the defect mark is continuously read by the mark reading device (340), and the defective portion is removed (350). In the removal, the part where the defect is detected may be punched out by punching or the like, or may be removed with a shear over the entire width of the sheet. The same applies to coils described later.

  In this way, the inclusion defect in each sheet is removed and the product is shipped to customer A (410). Needless to say, in removing the inclusion defect, only the development information may be used without marking the sheet. However, FIG. 1 does not show a flow using only the development map information. In the above method, the product from which the inclusion defect is removed not only passes the pass / fail judgment such as the inclusion density, but also the inclusion defect portion is removed, so that the quality is very high.

  Next, a case where the shipment form is a coil will be described. FIG. 1 shows a specific example in which the processing flow differs depending on whether or not the customer has a mark reading device (360). In the example described here, it is assumed that customer B has a mark reading device and customer C does not.

  When shipping to a customer B with a mark reading device, first, based on the coil development information (370) created in the same manner as in the case of the above sheet, the same defect marking as in the case of the sheet is performed (380), Ship to customer.

  On the customer B side, when the coil is rewound and processed, the defect mark is first read by the mark reading device (510), and the corresponding defective portion is removed (520). In this case, in order to prepare for troubles such as malfunction of the mark reading device, it is preferable to provide development map information to the customer B via a network.

  Finally, in the case of customer C who does not have a mark reading device at the customer, the coil is shipped without marking, and on the other hand, development map information is provided via a network (610). Then, on the customer C side, the defective portion of the coil is removed by shear cutting or the like based on the development information (620). This removal may be performed automatically, or may be performed manually by an operator.

  By doing so, it becomes possible to provide high-quality products based on the development map information to the customers B and C as well.

The method for removing a non-metallic inclusion defect portion of the present invention was applied to a hot-rolled steel plate (plate thickness: 2.0 mm, plate width: 1000 mm, length: 1000 m). In the present invention embodiment, a defect signal detected Ri by the ultrasonic line sensor are hot-rolled steel sheet longitudinally 0.15m or more, or to erase a flaw detection signal detected in the case of continuous or 30mm in width direction Treatment applied. And the comparison with the prior art example which does not perform such an erasure | elimination process of a defect signal was performed with respect to the same hot-rolled steel plate, and the defect density (piece / m < ² >) of both inclusion defects was contrasted.

As a result, in the example of the present invention, the defect density was 0.059 (pieces / m ² ), and compared with the analysis result of the detection part, there was almost no overdetection, whereas in the conventional example, the defect density was 0.209 (pieces / m ^2). In comparison with the analysis result of the detection part, the difference from the present invention was overdetected. The allowable defect density requested by the customer was 0.2 (pieces / m ² ).

  Subsequently, marking on the end of the steel plate and removal of the defective portion by the shear based on the development information were carried out before shipment.

  Therefore, in the quality inspection of the metal band, excessive reject products are generated in the conventional example, whereas in the present invention example, it is possible to provide a higher quality metal band while satisfying the quality required by the customer. .

It is a flowchart explaining the acceptance / rejection determination of this invention, and the removal method of a defective part. It is a side view of the flaw detection line to which the acceptance / rejection determination and defect removal method of the present invention is applied. It is a model arrangement drawing of an ultrasonic line sensor which detects a nonmetallic inclusion of a steel plate. It is an arrangement view of an ultrasonic line sensor in a flaw detection apparatus to which the pass / fail judgment method of the present invention is applied.

Explanation of symbols

1 Metal strip (steel plate)
2 Incoming bridle roll 3 Tension leveler 5 Outgoing bridle roll
10 Ultrasonic flaw detector
11-14 Transport roll
20 aquarium
21 water
22 Ultrasonic line sensor (detector)
22a Transmitter
22b Receiver
23a transmit ultrasonic beam
23b Receive ultrasonic beam
24 Inclusion determination processor (Flaw detection signal processor)
25 Line sensor mount

Claims (1)

It is a method of removing a non-metallic inclusion defect portion of a metal band based on development view information represented in correspondence with a longitudinal position and a width direction position of the defect in the metal band ,
When the defect signal of the detected nonmetallic inclusion defect is continuous for a predetermined length or more in the longitudinal direction and / or the width direction of the metal strip, the defect signal is erased. Otherwise, the nonmetallic inclusion defect is erased. A step of determining an object defect and editing the defect signal into the development view information;
A step of determining whether or not the metal band is accepted or not in comparison with the development plan information and a criterion agreed with the customer;
In the pass / fail judgment step, if it is rejected,
In the pass / fail judgment step, if it is acceptable, the following (A) to (C) any one of the steps (A) to (C) is adopted and processed.
(A) A step of marking the position of the corresponding defect, reading the marking mark, removing the corresponding defective portion, and shipping to the customer.
(B) A step of marking and shipping at the position of the corresponding defect and reading the mark of the marking on the customer side or removing the corresponding defective portion based on the development view information.
(C) A step of providing the developed map information to the customer and shipping it, and removing the corresponding defective portion on the customer side based on the developed map information.

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