JP4428249B2 - Metal strip manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a metal strip that can be effectively diverted even when it is not sufficient in terms of quality and cannot be used for a specific application when producing a metal strip for a specific application that requires high quality. is there.

  Due to the sophistication of the quality level required for metal products in recent years, for example, there is an increasing demand for high-strength steel strips and metal strips with less harmful defects such as surface defects (steel plates, stainless steel plates, aluminum plates, etc.). Yes. For example, steel sheets for special applications such as cold rolled steel sheets and plated steel sheets for automobiles and cans have high quality requirements, and specifications such as plate thickness, plating type, and steel type are generally available. It is often a special specification that is different from a steel plate.

  As a specific example (Example 1) in which high quality is required with respect to defects, in cold-rolled steel sheets used for automobiles, non-metallic inclusions mixed in the steel at the steel making stage or the like at the hot rolling stage Surface defects may occur due to biting of foreign matter. Some of them can be confirmed with the naked eye even after painting, which can be a big problem in appearance.

  Another example (Example 2) is a plated steel sheet for automobiles. The plated steel sheet for automobiles is manufactured through a steelmaking process, a hot rolling process, a pickling process, a cold rolling process, a plating process, and the like, and further becomes a member for an automobile through a pressing process and a painting process. One of the serious defects in plated steel sheets for automobiles is commonly called hege, and in automobiles that are the final product, the defects appear to be clearly different from other healthy parts, causing problems that impair the appearance, or If it becomes extremely severe, it will cause damage such as damage to the press machine during press molding.

This shave is present in all manufacturing processes, such as when non-metallic inclusions that occur in the steelmaking process have causes, or when there is a cause of the inclusion of oxides in the steel in the steelmaking process and hot rolling process. Among them, it is said that it originates from the upper process side. After the steel making process, the surface defect is manifested as a hege by undergoing hot rolling, cold rolling, and plating treatment.
In order to manufacture high-quality products such as those with few defects or those that require high strength as in the above example, it is important to take various manufacturing measures Needless to say. Appropriate manufacturing conditions so that a product with no quality problems can be produced, or if it is found that there is a quality problem as disclosed in Patent Document 1, for example, the manufacturing conditions are set in a subsequent process. A recovery method of correcting the value is conceivable.

However, even by such a method, a steel strip that cannot be used as a high-quality product may be formed due to variations in manufacturing conditions. In that case, even if the steel strip does not become as high quality as originally planned, it is necessary to devise effective use of the steel strip as high in value as possible. For example, if you tried to make the first superlative product but it was not sufficient in quality in the final shipment stage inspection, you could take measures such as reducing the grade or diverting it to another special purpose steel strip. May be taken. By adopting such a manufacturing method, for example, steel strips can be sold at a higher price compared to the case where the steel strips are not sufficient in quality compared to scrap, etc. The total manufacturing cost of the product group can be reduced.
JP 2002-161316 A

However, the above-described prior art has the following two problems.
(1) As mentioned above, it is only necessary for the customer to place an order for a “grade-reduced steel strip for another specific use”, but when considering various specifications such as steel grade, thickness, and width. In general, the appropriate timing is not always the appropriate timing. In addition, it is necessary to store until a suitable order is received, the storage cost is high, and the long-term demand for “graded” steel strip matches the amount of steel strip generated in this way. Since it is unclear whether or not to do so, it is often difficult in practice.
(2) In the conventional technology, the inspection is performed near the final shipment stage after the necessary manufacturing process, and when the destination is changed at the stage where it is found that there is a problem in quality, the action that can be taken is extremely limited.

  The present invention has been made in view of the above circumstances, and although it was planned to be manufactured for a specific application, it is insufficient in terms of quality. An object of the present invention is to provide a method for manufacturing a metal strip that makes the diversion practical by increasing the degree of freedom of action and making it a more general diversion destination.

In the invention according to claim 1 of the present invention, in producing a metal band for a specific application that requires high quality , the surface layer portion of the metal band before the treatment in the manufacturing process after the hot rolling process is AC magnetized, Measure changes in AC magnetic flux caused by the properties of the surface layer, select candidate portions for surface abnormalities based on the measured amplitude information of AC magnetic flux, and determine the depth based on the phase information of the selected candidate portions Estimating the position, predicting whether or not the candidate part will appear as a defect after processing in the manufacturing process based on the amplitude information, depth position, and manufacturing information of the candidate part , and based on this prediction result, the initial plan The metal band is characterized in that it is determined whether to leave it for the specific application as usual or to change the application to a general standard specification product, and to determine the processing conditions in the manufacturing process in accordance with this determination. Manufacturing method It is.

The invention according to claim 2 of the present invention is the method of manufacturing a metal strip according to claim 1, wherein the manufacturing process is a cold rolling process, and the metal strip before the treatment in the cold rolling process is processed. At the same time that the surface layer part is AC magnetized, the change in the AC magnetic flux caused by the properties of the surface layer part is measured, and the candidate part for the surface layer abnormality is selected based on the measured amplitude information of the AC magnetic flux. The depth position is estimated based on the phase information, and it is predicted whether or not the candidate part will appear as a defect after processing in the cold rolling process by the amplitude information, depth position, and manufacturing information of the candidate part. Based on this prediction result, when processing in the cold rolling process, it is determined whether to make the plate thickness as originally planned or a general standard plate thickness in the vicinity thereof. Is the method.

The invention according to claim 3 of the present invention is the method of manufacturing a metal strip according to claim 1, wherein the manufacturing process is a plating process, and the surface layer portion of the metal strip before the treatment in the plating process is exchanged with an alternating current. At the same time as magnetizing, the change in AC magnetic flux caused by the properties of the surface layer part is measured, the candidate part of the surface layer abnormality is selected based on the measured amplitude information of the AC magnetic flux, and the phase information of the selected candidate part is also obtained. The depth position is estimated, and whether or not the candidate part becomes apparent as a defect after processing in the plating process is predicted based on the amplitude information, the depth position, and the manufacturing information of the candidate part. The metal strip manufacturing method is characterized in that at the time of processing in the plating process, it is determined whether to use a plating type as originally planned or a general plating type.

The invention according to claim 4 of the present invention is the method of manufacturing a metal strip according to claim 1, wherein the manufacturing process is a hot rolling process, and the metal strip before the processing in the hot rolling process is performed . At the same time that the surface layer part is AC magnetized, the change in the AC magnetic flux caused by the properties of the surface layer part is measured, and the candidate part for the surface layer abnormality is selected based on the measured amplitude information of the AC magnetic flux. The depth position is estimated based on the phase information, and it is predicted whether or not the candidate part will appear as a defect after processing in the hot rolling process by the amplitude information, depth position, and manufacturing information of the candidate part. Based on this prediction result, when processing in the hot rolling process, it is determined whether to make the plate thickness as originally planned or a general standard plate thickness in the vicinity thereof. Is the method.

  In the present invention, by predicting in advance the quality after metal strip processing in a certain manufacturing process, it is possible to judge whether it is suitable for the high quality material originally planned. Since it is determined that there is a grade, the degree of freedom to take an action convenient for diversion increases when diverting the grade to another application, and as a result, a product with a general specification that is easy to divert can be obtained. Therefore, the metal strip can be used more effectively than when scrapping.

  An example of manufacturing a cold-rolled steel sheet will be described below with reference to the drawings. When manufacturing a cold-rolled steel sheet, the quality of the steel strip is evaluated before manufacturing the cold-rolled steel sheet. For example, the following two cases can be considered.

  [Case 1]: From the result of the sensor for measuring the quality of the steel strip installed in at least one location before the production of the cold-rolled steel sheet such as the steelmaking process, hot rolling line, pickling line, etc. Evaluate quality. FIG. 1 is a diagram showing an example of a processing flow (case 1) in the present invention. In this example, the quality of a steel strip is measured by a pickling line. At that time, not only the measurement results by sensors, but also the actual production data such as steelmaking and hot rolling stages (actual values of steel components, casting speed, nozzle status in the mold, temperature during hot rolling, etc.) It is also effective to make a judgment in consideration of some or all. Based on the quality evaluation results, when cold rolling is performed as it is, the quality such as whether surface defects occur or not is measured by past results (sensor measurement results, manufacturing result parameters and other means). Correlation data with quality).

  [Case 2]: The quality of the cold-rolled steel strip is predicted based on the past results only from the manufacturing parameters in the steelmaking and hot rolling stages. FIG. 2 is a diagram showing an example of a processing flow (case 2) in the present invention, and is different from the case 1 of FIG. 1 only in that the quality of the steel strip is not measured in the pickling line. After predicting the quality by the method of [Case 1] or [Case 2], if that results in the prediction that a steel strip for a specific application can be manufactured, the manufacturing conditions as originally planned If cold rolling is not expected, but it is expected that the quality will be insufficient even if it is manufactured as it is, the cold rolling parameters (sheet thickness) are generally sold in large quantities as standard. Change to specifications and manufacture.

  As shown in Fig. 1 and Fig. 2, although production was started with the intention of initially cold rolling to a thickness of 0.765mm, sufficient quality was ensured after cold rolling by prediction based on quality evaluation before cold rolling. If it is determined that it is not possible, the production conditions (sheet thickness) are changed, and cold rolling is performed to a standard sheet thickness (0.800 mm in this example). In this example, the thickness is changed to a thickness near the initially planned thickness. This is more convenient because various rolling conditions (roll type, rolling force, etc.) can be made similar, and there is a merit that a minimum change is required.

  In the method shown in FIG. 1, when “quality” to be maintained is to reduce the number of surface defects after cold rolling or to reduce the density, it is suitable as a quality sensor for realizing the above method. The details will be described in detail below.

  Such a quality sensor has a surface defect that is the quality to be evaluated after cold rolling, so it is exposed to the surface before cold rolling as well as the detection of the surface defect before cold rolling. The surface layer (surface + subsurface: including the area inside the metal strip at a depth near the surface and the surface) that cannot be judged as a harmful level even if it is not exposed is first required to be detected . In addition to detection, (1) Steel before cold rolling, such as the properties of the detection part (size, depth, etc.), steel type, manufacturing conditions in the hot rolling process, manufacturing conditions in the steel making process, etc. It is necessary to be able to predict and determine whether or not a surface defect will occur after cold rolling in consideration of the state of the belt and (2) manufacturing conditions planned for cold rolling.

  For example, even if it is a surface defect before cold rolling, small and shallow defects can be reduced by cold rolling and can be harmless, and there is an abnormality in the surface layer part before cold rolling. However, when it exists only in the deep position, since it may not manifest as a defect on the surface by cold rolling, the function to predict is required.

  Specifically, as already described, since the defective portion to be detected exists on the surface layer (not necessarily exposed on the surface), (1) it is inappropriate to detect only the change in surface properties. Yes (Optical defect detection method is inappropriate), (2) It is only necessary to detect defects existing in the surface layer (about 100 μm from the surface), and it is not necessary to investigate deep inside (3) Boundary surface (surface ) And the detection site must be close to each other (it is difficult due to the presence of a surface dead zone in a general ultrasonic flaw detection method used online).

  For the above reason, the quality sensor is preferably a system in which the surface layer portion of the steel strip measuring surface is AC magnetized and the change in AC magnetic flux caused by the properties of the surface layer portion is measured. FIG. 3 is a diagram illustrating an example of the configuration of the surface layer property measuring apparatus. An AC magnetic flux 4 is applied from the outside of the steel strip 1 by the excitation device 3 of the quality sensor, and the AC magnetic field detected by the magnetic detection sensor 5 changes due to the presence of the surface layer property abnormality portion 2 in the steel strip 1 (the subject's magnetic field). The magnetic detection sensor 5 measures the state (including the influence on the magnetic flux path as a ferromagnetic material and the electromagnetic induction effect of the subject).

  Next, after the signal is amplified by the amplifier 6, synchronous detection is performed by the synchronous detector 7, and the amplitude and phase information of the AC magnetic flux is obtained. At this time, information regarding the depth of the defect can be obtained from the obtained phase information. Further, based on the obtained amplitude information, the surface defect revealing predicted site primary candidate detection apparatus 8 selects a candidate part, and then determines the depth position of the abnormal part based on the phase information of the candidate part. The position is estimated by the position estimation device 10.

  From the manufacturing condition results obtained from the manufacturing information holding device 16 holding the amplitude information, depth position information, manufacturing information, etc. of the candidate portion, the candidate portion after cold rolling is obtained by the surface defect occurrence prediction device 12 after cold rolling. Is estimated as a defect and the density on the steel strip, etc., and the extent to which the surface defect of the steel strip becomes apparent after cold rolling is evaluated. At that time, in advance what the sensor output value, keep looking to see become surface defects when manufacturing conditions result values, it is necessary to determine it as a reference. Then, the process computer 17 for cold rolling control decides whether to manufacture a high-grade steel material as originally planned or a steel strip having a general specification, and the thickness value corresponding to the rolling steel ( (Not shown)

  Moreover, when it is necessary to evaluate quality in a certain range in the steel strip width direction, quality sensors are arrayed and arranged in the width direction. Hereinafter, a more specific example of a quality sensor particularly suitable for use in the present invention will be described with reference to FIG. The steel sheet 1 has a surface property abnormal portion 2 that is minute in the width direction and long in the length direction (direction perpendicular to the paper surface) (extended by rolling). An alternating current is supplied to the coil of the excitation device 3 by the alternating current excitation power source 11 to magnetize the surface layer portion of the steel plate 1 in a concentrated manner. In FIG. 4, magnetization is performed such that the magnetic flux is formed in the width direction of the steel sheet 1. However, considering the form of the defect as described above, it is preferable to perform such magnetization as much as possible.

  Then, the magnetic flux existing outside the steel plate 1 is detected by the two magnetic detection sensors 5a and 5b. In this case, since the surface layer property abnormality portion 2 exists under the magnetic sensor 5a, magnetic flux and eddy current are less likely to pass through the surface layer property abnormality portion. As a result, the magnetic sensor 5b detects the magnetic flux detected by the magnetic sensor 5a. More than the detected magnetic flux, the output of the magnetic sensor 5a becomes larger than the output of the magnetic sensor 5b. Therefore, these outputs are differentially guided to the amplifier 6 (hereinafter the same as FIG. 3 and omitted in FIG. 4), and the output is input to the phase detector 7 and synchronized with the waveform of the magnetizing power source 3. (Phase may be shifted.) When phase detection is performed using a signal, a signal corresponding to the size of the surface layer property abnormality portion 2 is obtained. This output is guided to the surface property abnormal portion level discriminator 8 and compared with a predetermined threshold value, whereby the level of the surface property abnormal portion 2 is determined.

  The surface property abnormal portion 2 is very small in the C cross section of the steel sheet (cross section when the width direction steel strip is cut), but is long in the length direction, so the E-type coil is arranged in the direction as shown in FIG. As a result, the width of the magnetic path to be blocked is increased, and a large surface layer abnormal portion signal is obtained. In addition, since the surface layer abnormal portion is discriminated based on the differential signals of the outputs of the two sensors, noise common to the steel sheet 1 (change in magnetic permeability, etc.) and external noise are canceled out, and the surface layer has a good S / N ratio. It is possible to detect abnormal properties. Here, in order to obtain information only on the surface layer, the excitation frequency is set to 100 kHz or more. In addition, although the sensor with an E-shaped core was explained in full detail here as an example, it cannot be overemphasized that various things can be used if it is a sensor using an alternating current magnetic flux.

  As described above, as an example of the production of the metal strip, the case where the production of the cold rolled steel sheet is taken up and the quality of the metal strip is evaluated before the treatment in the cold rolling process (pickling line) has been described. The present invention is not limited to a steel strip having a cold rolling step and a plating treatment step after the hot rolling step, and can be applied to a manufacturing process of a metal strip such as an aluminum plate. For example, the application effect in the plating process, the hot rolling process, and the above-described cold rolling process is great.

It is a figure which shows an example of the processing flow (case 1) in this invention. It is a figure which shows an example of the processing flow (case 2) in this invention. It is a figure which shows an example of a structure of a surface layer part property measuring apparatus. It is a figure which shows the specific example of a quality sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel strip 2 Surface property abnormality 3 Excitation apparatus 4 AC magnetic flux 5, 5a, 5b Magnetic detection sensor 6 Amplifier 7 Synchronous detector 8 Surface defect manifestation expected primary part detection apparatus 9 Magnetic sensor with E-shaped core 10 Depth Position estimation device 11 AC excitation power supply 12 Surface defect revealing prediction device after cold rolling 16 Manufacturing information holding device (process computer, etc.)
17 Process computer for cold rolling control

Claims (4)

When manufacturing a metal strip for a specific application that requires high quality, the magnetic flux generated due to the properties of the surface layer at the same time as the surface layer of the metal strip is AC magnetized before the process in the manufacturing process after the hot rolling process. , Measure the surface flux anomaly based on the measured AC magnetic flux amplitude information, estimate the depth position based on the selected candidate phase information,
Predict whether or not the candidate part will be manifested as a defect after processing in the manufacturing process based on the amplitude information, depth position, and manufacturing information of the candidate part , and based on the prediction result, for the specific application as originally planned A method for producing a metal strip, wherein the method of determining whether to change the application to a general standard specification product is determined, and the processing conditions in the manufacturing process are determined in accordance with the determination. In the manufacturing method of the metal strip according to claim 1,
The manufacturing process is a cold rolling process, and at the same time, the surface layer portion of the metal strip before the treatment in the cold rolling process is AC magnetized, and at the same time, the change in AC magnetic flux caused by the properties of the surface layer portion is measured, Based on the measured AC magnetic flux amplitude information, select a candidate part of the surface layer abnormality, estimate the depth position based on the phase information of the selected candidate part,
Predict whether or not the candidate part will manifest as a defect after processing in the cold rolling process by the amplitude information, depth position, and manufacturing information of the candidate part , and based on this prediction result, in the cold rolling process A method for producing a metal strip, characterized in that, at the time of processing, it is determined whether the thickness is as originally planned or a general standard thickness in the vicinity thereof. In the manufacturing method of the metal strip according to claim 1,
The manufacturing process is a plating process, and the surface layer portion of the metal strip before the treatment in the plating process is AC magnetized, and at the same time, the change in AC magnetic flux caused by the properties of the surface layer portion is measured, and the measured AC magnetic flux is measured. Select the candidate part of the surface anomaly based on the amplitude information of, estimate the depth position based on the phase information of the selected candidate part,
It is predicted whether the candidate part will appear as a defect after processing in the plating process based on the amplitude information, depth position, and manufacturing information of the candidate part , and based on this prediction result, at the time of processing in the plating process, A method for producing a metal strip, characterized in that it is determined whether to use a plating type as planned or a general plating type. In the manufacturing method of the metal strip according to claim 1,
The manufacturing process is a hot rolling process, and the surface layer portion of the metal strip before the treatment in the hot rolling process is AC magnetized, and at the same time, the change in AC magnetic flux caused by the properties of the surface layer portion is measured, Based on the measured AC magnetic flux amplitude information, select a candidate part of the surface layer abnormality, estimate the depth position based on the phase information of the selected candidate part,
Predict whether or not the candidate part is manifested as a defect after processing in the hot rolling process by the amplitude information, depth position, and manufacturing information of the candidate part , and based on the prediction result, in the hot rolling process A method for producing a metal strip, characterized in that, at the time of processing, it is determined whether the thickness is as originally planned or a general standard thickness in the vicinity thereof.