JPH07248222A - Method for measuring shape of hot-rolled steel plate - Google Patents

Abstract

PURPOSE:To provide a method for measuring a shape of a hot-rolled steel plate after being cooled. CONSTITUTION:A surface temperature in a widthwise direction of a steel plate cooled after being hot rolled is continuously measured at least at three points of a central part and both end parts. An average temperature at each measuring point within a reference measuring time DELTAt is calculated every moment. The measuring point showing the highest value among the calculated average temperature is selected and a temperature difference delta between the maximum and minimum values of the measured temperature at the selected position is obtained. If the temperature difference delta is equal to or larger than a preset reference temperature difference deltaS, the steel plate is judged to be improper in shape. When the average temperature at the central part is higher than the average temperature at both end parts, the steel plate is judged to form wave in the middle part. When the average temperature of each of both end parts is higher than that of the central part, the steel plate is judged to have waves in both edges. Meanwhile, when the average temperature at one end part is lower than that at the central part, a wave in one edge is judged. Moreover, when the average temperature of the left end part is higher than that at the right end part, a wave in the left edge is determined. To the contrary, if the average temperature at the right end part is higher than that at the left end part, the steel plate is judged to have a wave in the right edge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the shape of a hot rolled steel sheet, and more particularly to a method for measuring the shape of the hot rolled steel sheet after cooling.

[0002]

2. Description of the Related Art In general, manufacturing a hot-rolled steel sheet having a good shape not only ensures the quality of rolled products, but also makes it possible to perform rolling on a rolling mill and winding on a coiler stably, which is high. It is also important for maintaining the yield. Conventionally, the steel plate shape in the hot rolling line is measured by, for example, using a shape meter attached to the exit side of the finishing stand, or visually determined by an operator, and based on the information, a work roll bender or the like is used. Rolling was being performed while being adjusted.

On the other hand, the development of measuring technology in recent years has been remarkable, and attempts are being made to introduce a shape measuring apparatus into a hot rolling line. As one of them, there is known a method in which a plurality of laser rangefinders are arranged on the exit side of the finishing stand in the width direction of the steel sheet and the distance to the steel sheet is measured to determine the shape. There is also a technique for determining the shape by measuring the tension distribution in the width direction of the steel sheet between the finishing stands.

Further, even if the shape after finish rolling is good, if the cooling is not performed uniformly in the width direction, the steel sheet is distorted by thermal stress during cooling and the shape is deteriorated, so that the winding is stable. There is a problem that you can not do it. Therefore, the steel sheet needs to be cooled uniformly in the width direction, which is important for obtaining a uniform material. As cooling equipment used for cooling such a steel sheet, nozzles for supplying cooling water are usually arranged at equal intervals, and a masking device for preventing excessive cooling of the end portion of the steel sheet is provided. What is installed (for example,
59-24511).

For the steel sheet after cooling, the surface temperature at the center in the width direction is measured by, for example, a radiation thermometer, and in order to obtain the target winding temperature, the amount of cooling water supplied from the cooling equipment is adjusted by control such as feedback. To be done. In this case, in addition to the thermometer, a radiation thermometer capable of measuring the temperature in the width direction is often installed. However, a device that directly measures the shape of the steel sheet after passing through the cooling equipment, that is, before winding, is rarely installed, and the shape is usually only visually determined through a television monitor.

The minimum thickness of hot-rolled steel sheet that can be manufactured by the conventional technique was about 1.2 mm, but the sheet thickness has been improved by the increase of rolling speed, the adoption of endless rolling, and the progress of stripping stabilization technology. It is becoming possible to manufacture hot-rolled steel sheets with a thickness of 0.8 to 1.0 mm. As a result, the number of product types that can omit the cold rolling process that has always been passed through has been increased, and it is possible to significantly reduce the manufacturing cost.

[0007]

However, in the prior art as described above, the shape measuring device for the steel sheet after passing through the cooling equipment is not installed, and the shape defect caused by the uneven cooling in the width direction is caused. The only way to monitor was to make a visual judgment through a TV monitor.
There is a problem that it is inevitable that the load of the operator's shape monitoring work during product manufacturing increases.

Further, as described above, when manufacturing a product having a thinner plate thickness than the conventional one, even a slight cooling unevenness in the width direction leads to a defective shape. Therefore, the cooling should be stabilized while measuring the shape after cooling. Setting conditions is becoming more important. On the other hand, a method of installing a plurality of X-ray distance meters in the width direction of the steel plate on the outlet side of the cooling equipment to measure the shape is also conceivable, but the equipment cost is high. It is difficult to implement because of problems.

By the way, when the shape of the steel sheet during cooling is disturbed and unevenness is generated, as shown in FIG. Ability decreases. Further, normally, on the outlet side of the cooling zone, the water (hereinafter referred to as “laden water”) staying on the upper surface of the steel plate is blown off to the side by side spray or the like.
Since water collects in the lower part, it may rest on the steel plate with a bad shape and remain.

In such a case, after this, the mounting water locally cools the water, and uneven cooling occurs in the longitudinal direction of the steel sheet. Therefore, during cooling, once the shape irregularity occurs due to the uneven cooling, this further expands the uneven cooling and becomes a vicious cycle in which the shape is further deteriorated. An object of the present invention is to provide a method for measuring the shape of a hot-rolled steel sheet, which solves the problems of the above-mentioned conventional techniques.

[0011]

A method for measuring the shape of a hot-rolled steel sheet according to the present invention is a method for measuring the shape of a hot-rolled steel sheet after cooling, and the surface temperature in the width direction of the water-cooled steel sheet after hot rolling. For continuously measuring at least three points at the center and both ends thereof, for calculating the average temperature within the reference measurement time Δt for each of the measurement points, and for each of the calculated average temperatures. The step of selecting the measurement position showing the highest value from among the values, the step of obtaining the temperature difference δ between the maximum value and the minimum value of the measured temperature at the selected measurement position, and this temperature difference δ was given in advance. Reference temperature difference δ
If it is equal to or larger than _S , it is determined that there is a defective shape, and if the temperature difference δ is smaller than the reference temperature difference δ _{S, the} shape is determined to be good.

Further, in the method for measuring the shape of a hot-rolled steel sheet of the present invention, following the step of determining that there is a defective shape, when the average temperature value of the central portion is higher than each average temperature value of both ends, an abdominal wave is generated. Judgment, and if it is small, the process of determining the ear extension,
After the step of determining the ear extension, it is determined as both ear waves when the average temperature at both ends is larger than the central portion, and when one of the end portions is smaller than the central portion, it is determined as one ear wave. It is characterized by being added.

[0013]

[Operation] According to the present invention, the shape of the steel sheet can be accurately determined by continuously measuring the surface temperature of the water-cooled steel sheet after hot rolling in three or more points in the width direction. . The principle of measuring the shape will be described in detail below. That is, in general, the portion where the temperature is high in the width direction of the steel sheet has a smaller heat shrinkage than the other portions, so that the substantial length of the steel sheet becomes long. However, the respective portions of the steel sheet are constrained to each other and cannot change in length in the width direction. For example, the thermal stress of compression works in a high temperature portion where the length of the steel sheet is substantially long. When this compressive stress becomes large to some extent, buckling occurs and unevenness (defective shape) occurs.

Once the unevenness occurs, the mounting water easily stays in the recessed portion and cools this portion. On the other hand, on the other hand, it becomes difficult for water to be deposited on the convex portions, so that the cooling capacity is significantly reduced as compared with other portions. As described above, in the place where there is unevenness, uneven cooling occurs not only in the width direction but also in the longitudinal direction. On the other hand, the resting water is uniformly accumulated in the portion having no unevenness, so that the stable cooling capacity can be maintained.

That is, the portion where buckling is likely to occur and unevenness is likely to occur is the highest temperature portion in the width direction, and here it can be considered that there is some temperature variation in the longitudinal direction as well. In addition, since there are generally three types of shape defects, an abdominal wave, both ear waves, and one ear wave, in order to distinguish and measure these, the temperature at least at the central portion of the steel plate and at three locations at both ends Measurement is required.

Next, the procedure of shape measurement according to the present invention will be described. Surface temperature T _C at each measurement point at three points of the central portion of the steel sheet and both left and right ends within a certain reference measurement time Δt,
Continuously measure T _LE and T _RE . The average temperatures T _C ^* , T _LE ^* , and T _RE ^* at each measurement point are calculated moment by moment. A measurement position showing the highest value is selected from the calculated average temperature values. The temperature difference δ between the maximum value and the minimum value of the measured temperature at the selected measurement position is calculated. This temperature difference δ is a reference temperature difference δ given in advance.
_When it is equal to or larger than _S , it is determined that there is a defective shape, and in other cases, it is determined that the shape is good. When the average temperature value T _C ^{* of the} central portion is larger than the average temperature values T _LE ^* and T _RE ^{* of the} left and right ends, it is determined that the shape is an abdominal wave, and in other cases, it is determined that the shape is ear extension. Furthermore, if the average temperature values T _LE ^* and T _RE ^* at the left and right ends are greater than the average temperature value T _C ^{* at the} center after the determination of ear extension, then it is determined that the shape is binaural. In case of, it is judged as one ear wave.

The above procedure is shown in FIG. The reference measurement time Δt may be set to a time during which the steel sheet travels for about 4 to 5 m. This is because the unit length at which irregularities of the defective shape is repeated is at most 4 to 4.
This is because it is about 5 m. The reference temperature difference Δ _S, which is the criterion for determining the shape defect, is preferably about 20 ° C. This is because there is a slight temperature difference in the steel sheet in the longitudinal direction, but this may be erroneously determined as a defective shape, and it is not preferable to make δ _S very small. On the contrary, if δ _S is set to a large value of about 40 to 50 ° C, there is a possibility that even if there is a defective shape, it cannot be detected.

As described above, the portion having a high temperature in the width direction is detected, and the shape of the steel sheet is determined while checking the temperature variation in the longitudinal direction. Therefore, the measurement is performed very accurately. As a result, it is not necessary to separately install an expensive measuring device such as a laser range finder, and the shape monitoring work is not required, and labor can be saved. Further, by using the measured data, it is possible to manage the coil regarding the shape at the time of winding. Furthermore, by learning these data, it is possible to obtain an optimum cooling condition that is uniform in the width direction, so that it is possible to stabilize the shape.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic diagram showing an example in which the shape measuring apparatus of the present invention is applied to the cooling equipment outlet side of a hot rolling line. As shown in the figure, the steel sheet 1 rolled by the hot finish rolling mill 3 is wound by the coiler 5 while being cooled by the cooling equipment 4, and at that time, the inlet side of the cooling equipment 4 (hot finish rolling) is used. The X-ray plate thickness meter 6, the shape measuring device 7, and the entrance side radiation thermometer 8 installed on the exit side of the machine 3 measure the plate thickness, shape, and surface temperature, respectively.

The outlet side of the cooling equipment 4 (the inlet side of the coiler 5)
The surface temperature after cooling is measured by the emission radiation thermometer 9 provided in the. The emission side radiation thermometer 9 can continuously measure the temperature distribution in the width direction of the steel plate 1, and the measurement signal is input to the arithmetic unit 10. Then, the arithmetic unit 10 reads the temperatures at the central position and the left and right ends, and the data processing is performed by the above-described procedures (1) to (3).

Using the thus constructed apparatus, a steel sheet having a thickness of 4 mm and a width of 1000 mm made of low carbon steel has a target winding temperature of 550 ° C. and a width after cooling when traveling at a speed of 600 mpm. The directional temperature distribution was measured. At this time, the data sampling time was 0.05 sec, the reference measurement time Δt for determining the shape was 0.5 sec, and the reference temperature difference δ _S was 20 ° C.

Based on the results of these measurements, the arithmetic unit 8
In, the average value of the measured temperature at three points in the width direction is calculated,
The temperature fluctuations at each measurement point are
Reference temperature difference δ_SWhether to exceed
I went. That is, the measurement at the selected measurement position
The difference between the maximum and minimum temperature is δ_SEqual to or
When it was large, it was determined that the shape was defective. Also, the measured temperature
The difference between the maximum and the minimum of δ _SShape is better if smaller than
It was judged to be good. In addition, the criteria for determining the shape defect are
It was determined as shown in 1.

[0023]

[Table 1]

Next, a specific temperature pattern of the one determined to have a defective shape will be described. Figures 3 (a) and 3 (b) show the measurement patterns of the time variation of the steel plate temperature.
FIGS. 4A to 4E show measurement patterns of the temperature distribution in the width direction, and the correspondence between the measurement patterns of FIGS. 3 and 4 and the steel plate shape will be specifically described below. (1) In the case of an abdominal wave shape: The temperature distribution in the width direction of the steel sheet was the pattern of FIG. 4 (a) in which the central part was higher than both ends and the pattern of FIG. 4 (b) which was flat as a whole. At this time, the temperature change at the central portion in the width direction of the steel plate has a fluctuation of 20 ° C or more, as shown in the pattern in Fig. 3 (b). It looks like the pattern in Figure 3 (a), which is not. (2) When both ears are present; the temperature distribution in the width direction of the steel sheet is the pattern shown in Fig. 4 (b), which is generally smooth, and the pattern shown in Fig. 4 (c), in which both ends are higher than the center, is repeated. At this time, the change with time of the temperature at the central portion was as shown in the pattern of FIG. 3 (a) at the central portion in the width direction and at the respective left and right ends as shown in FIG. 3 (b). (3) In case of one ear wave (left end); the pattern of Fig. 4 (b) in which the temperature distribution in the width direction is generally smooth, and the pattern of Fig. 4 (d) in which the left end is higher than the center and the right end are repeated. The time-dependent change in temperature at the central portion and the right end is shown in FIG. 3 (a), and the change in temperature at the left end is shown in FIG. 3 (b). (4) In case of one ear wave (right end); the pattern of Fig. 4 (b) in which the temperature distribution in the width direction is generally smooth, and the pattern of Fig. 4 (e) in which the right end is higher than the center and the left end are repeated. The time-dependent change in temperature at the center and the left end is shown in FIG. 3 (a), and the change in temperature at the right end is shown in FIG. 3 (b).

The results are summarized in Table 2.

[0026]

[Table 2]

As a result of the above measurement, the detection accuracy was almost the same as the accuracy of the conventional shape measuring apparatus using a plurality of laser distance meters, which was satisfactory. As a result, it is possible to reduce the operator's load of shape monitoring because it is not necessary to perform visual shape monitoring work that has been conventionally performed. In addition, coil management related to the shape at the time of winding can be automatically performed, and by learning these acquired data, operating conditions for uniform cooling in the width direction can be established. It is possible to significantly reduce the defective shape caused by the above.

In the above embodiment, the temperature distribution at three points in the width direction of the steel sheet was described as being measured using a radiation thermometer. However, the present invention is not limited to this, and for example, conventionally used winding You may measure the temperature by installing multiple thermometers that can measure the temperature of a specific area (such as only the central position of the steel plate) like the thermometer in the width direction,
Alternatively, the temperature may be measured at multiple points including the center position of the steel plate and the intermediate position between both ends, and the quarter wave may be determined.

In this embodiment, the thermometer capable of measuring the temperature distribution in the width direction is installed on the outlet side of the cooling equipment. However, this thermometer may be arranged at an intermediate position of the cooling equipment. In this case, the shape of the cooled steel sheet can be measured upstream of the installation location of the thermometer in the transport direction.

[0030]

As described above, according to the present invention,
Since the shape of the steel sheet can be determined by continuously measuring the temperature of the water-cooled steel sheet after hot rolling at three or more points in the width direction, it is necessary to perform a visual shape monitoring operation that has been conventionally performed. In addition, it is possible to reduce the load on the operator, and further, by adopting feedback control to the cooling equipment or the like, it is possible to reduce shape defects caused by uneven cooling.

[Brief description of drawings]

FIG. 1 is a flow chart showing a procedure of shape measurement according to the present invention.

FIG. 2 is a schematic diagram showing an example in which the shape measuring device of the present invention is applied to the cooling equipment outlet side of a hot rolling line.

3 (a) and 3 (b) are characteristic diagrams showing measurement patterns of changes over time in steel sheet temperature.

4 (a) to 4 (e) are characteristic diagrams showing a measurement pattern of a temperature distribution in the width direction.

FIG. 5 is a perspective view showing an uneven shape of a steel plate.

[Explanation of symbols]

 1 Steel Plate 2 Cooling Water 3 Hot Finishing Rolling Machine 4 Cooling Equipment 5 Coiler 6 X-Ray Plate Thickness Gauge 7 Shape Measuring Device 8 Inlet Radiation Thermometer 9 Outlet Radiation Thermometer 10 Computing Device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Kuwako 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Chiba Steel Works (72) Inventor Tokuharu Ishibashi, Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Works Co., Ltd. Chiba Steel Works (72) Inventor Norio Kanemoto 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Works Chiba Works

Claims (2)

[Claims] 1. A method for measuring the shape of a hot-rolled steel sheet after cooling, wherein the surface temperature in the width direction of a water-cooled steel sheet after hot rolling is continuously measured at least at three points in the center and both ends. A step of measuring, a step of momentarily calculating an average temperature within the reference measurement time Δt for each of the measurement points, and a step of selecting a measurement position showing the highest value from the calculated average temperature values. , The step of obtaining the temperature difference δ between the maximum value and the minimum value of the measured temperature at the selected measurement position, and the shape if the temperature difference δ is equal to or larger than the reference temperature difference δ _S given in advance. A method for measuring the shape of a hot-rolled steel sheet, comprising the step of determining that there is a defect and determining that the shape is good when the temperature difference δ is smaller than the reference temperature difference δ _S. 2. Following the step of determining that there is a defect in shape, a step of determining an abdominal wave if the average temperature value of the central portion is higher than the average temperature value of both ends, and determining an ear extension if it is smaller. Then, after the step of determining the ear extension, it is determined as both ear waves when the average temperature at both ends is larger than the center portion, and when one of the end portions is smaller than the center portion, it is determined as one ear wave. The method for measuring the shape of a hot-rolled steel sheet according to claim 1, further comprising: