Devices and methods for monitoring nozzle blockage and methods for manufacturing steel

Abstract

The present invention provides a device and method for monitoring nozzle blockage, as well as a method for manufacturing steel. The device for monitoring nozzle blockage includes: an acquisition unit (160) that acquires a first value as the value of a flow meter installed on a pipe attached to a manufacturing equipment having a spray nozzle, and a second value as the value of at least one of a pressure gauge and a valve opening, as the latest data; a setting unit (162) that sets a threshold value of the second value relative to the first value over time from past data of the first and second values; and a determination unit (163) that determines that nozzle blockage has occurred when the latest data is outside the range of the threshold value.

Description

[Technical Field]

[0001] This invention relates to a device and method for monitoring nozzle blockage and a method for manufacturing steel. [Previous Technology]

[0002] In the continuous casting of steel using a continuous casting machine, cooling water is sprayed from a spray nozzle onto the casting sheet to cool it (two-stage cooling). In this equipment, in the past, in order to monitor the blockage of the spray nozzle, a pressure gauge was installed on the piping, and an abnormality was determined when the pressure value relative to the reference flow rate exceeded a preset threshold value.

[0003] Patent Document 1 describes a two-stage cooling method for continuous casting, in which cooling water is supplied to the circumferential surface of the casting while monitoring whether the supply pressure and / or flow rate of the cooling water supplied from the nozzle is within a certain range along the supply pressure-flow rate curve of the nozzle.

[0004] Furthermore, Patent Document 2 describes a method that calculates the difference between the measured values ​​of the back pressure of the spray nozzle and the valve opening of the flow regulating valve and each reference mode. When either or both of the average value of the back pressure difference and the average value of the valve opening exceed a predetermined value, it is determined that the nozzle has malfunctioned. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2001-179141 [Patent Document 2] Japanese Patent Publication No. 3373007 [Summary of the Invention]

[0006] [Problem to be Solved by the Invention] However, the methods described in Patent Documents 1 and 2 all involve continuous monitoring based on pre-set threshold values. Therefore, sometimes, after parts are replaced due to malfunction or lifespan, the water volume or back pressure values ​​change due to individual differences in the replaced parts. In such cases, sometimes even with brand-new parts and no operational abnormalities, the data may still classify it as abnormal, frequently resulting in situations where the original purpose of monitoring for blockages cannot be achieved. When an abnormality is detected, the production line must be stopped immediately for confirmation, thus significantly reducing operational efficiency due to excessive detection of abnormalities. On the other hand, when the pressure after replacement is lower than the initially assumed model, even if pressure blockages would normally occur, they are not classified as abnormal because no blockages have occurred, leading to significant problems.

[0007] Therefore, the present invention was developed with regard to the above-mentioned problems, and its object is to provide a monitoring device and method for accurately detecting nozzle blockage in the spray nozzle of a continuous casting machine, as well as a method for manufacturing steel. [Technical means for solving the problems]

[0008] (1) According to one aspect of the present invention, a nozzle clogging monitoring device is provided, comprising: an acquisition unit that acquires a first value as the value of a flow meter installed on a pipe attached to a manufacturing apparatus having a spray nozzle, and a second value as the value of at least one of a pressure gauge and a valve opening, as the latest data; a setting unit that sets a threshold value of the second value relative to the first value over time from past data of the first value and the second value; and a determination unit that determines that nozzle clogging has occurred when the latest data is outside the range of the threshold value.

[0009] (2) In the nozzle blockage monitoring device described in (1) above, when the change in the closest past data is below a predetermined value, the setting unit sets the threshold value based on the closest past data.

[0010] (3) According to one aspect of the present invention, a method for monitoring nozzle blockage is provided, comprising: an acquisition step, which acquires a first value as the value of a flow meter installed on a pipe attached to a manufacturing device having a spray nozzle, and a second value as the value of at least one of a pressure gauge and a valve opening, as the latest data; a setting step, which sets a threshold value of the second value relative to the first value over time from past data of the first value and the second value; and a determination step, which determines that nozzle blockage has occurred when the latest data is outside the range of the threshold value.

[0011] (4) According to one aspect of the present invention, a method for manufacturing steel is provided, which is a method for continuously casting steel using a continuous casting machine. During continuous casting, the nozzle clogging monitoring method described in (3) above is used to monitor the nozzle clogging of the spray nozzle of the continuous casting machine. [Effects of the Invention]

[0012] According to one aspect of the present invention, a monitoring device and monitoring method for detecting nozzle blockage with high accuracy in the spray nozzle of a continuous casting machine, as well as a method for manufacturing steel, are provided.

Implementation Method

[0014] In the following detailed description, embodiments of the present invention are described with reference to the drawings. In the drawings, identical or similar parts are indicated by identical or similar symbols, and repeated descriptions are omitted. The drawings are illustrative and may sometimes differ from actual embodiments. Furthermore, the embodiments shown below are examples of apparatus or methods used to embody the technical concept of the present invention; the technical concept of the present invention does not specify the materials, structures, or arrangements of the constituent parts as described below. Various modifications can be made to the technical concept of the present invention within the technical scope defined in the claims.

[0015] <Monitoring Device for Continuous Casting Machine and Nozzle Blockage> As shown in FIG1, the nozzle blockage monitoring device 16 of this embodiment of the present invention is installed in the continuous casting machine 1. The continuous casting machine 1 continuously casts steel to manufacture the casting sheet 3. There is no particular limitation on the type of continuous casting machine 1, such as bending die or vertical bending die. Furthermore, in this embodiment, the continuous casting machine 1 manufactures a flat steel billet with a rectangular cross-sectional shape orthogonal to the long side direction as the casting sheet 3.

[0016] The continuous casting machine 1 includes: a hopper 10, a feed trough 11, a mold 12, multiple rollers 13, a secondary cooling zone 14, a cutting device 15, and a monitoring device 16. In this continuous casting machine 1, molten steel 2 contained in the hopper 10 is fed to the feed trough 11, which serves as an intermediate container, and then fed from the feed trough 11 to the mold 12. The molten steel 2 supplied to the mold 12 is cooled in the mold 12 (primary cooling) to form a solidified shell. Then, while pulling out this solidified shell, it is further cooled in the secondary cooling zone 14 (secondary cooling) to produce a casting sheet 3. The casting sheet 3 is then cut to a predetermined length by the cutting device 15.

[0017] The secondary cooling zone 14 is a region where cooling water is sprayed from nozzles to cool the casting sheet 3. The secondary cooling zone 14 is composed of a plurality of cooling zones; in the example shown in FIG1, it is composed of three cooling zones 14a to 14c. Furthermore, each cooling zone of the secondary cooling zone 14 is composed of a plurality of zones arranged in the casting direction and the plate width direction, in which approximately 20 to 60 nozzles are provided in one zone. The casting direction, within the continuous casting machine 1, is the direction in which the casting sheet 3 moves (from the mold 12 in FIG1 toward the long side of the casting sheet 3 towards the cutting device 15), and the plate width direction is the width direction of the casting sheet 3 (the front-back direction in FIG1).

[0018] Figure 2 is a top view from the casting direction, showing the position between adjacent rollers 13 in the casting direction, as an explanatory diagram of the secondary cooling zone 14. As shown in Figure 2, a plurality of spray nozzles 141 are provided in the gap between adjacent rollers 13 in the casting direction. The spray nozzles 141 are water spray nozzles or mist spray nozzles, etc., and spray cooling water 142 onto the casting sheet 3. In addition, the cooling water 142 supplied to the spray nozzles 141 is supplied to each zone of each cooling zone through piping (not shown in the figure), and the flow rate is adjusted by a flow regulating valve (not shown in the figure) provided in this piping. The flow rate adjustment by the flow regulating valve is performed by adjusting the opening degree (valve opening) of the flow regulating valve. Furthermore, each piping is provided with a flow meter (not shown in the figure) for measuring the flow rate of the supplied cooling water 142, and a pressure gauge (not shown in the figure) for measuring the pressure (water pressure) of the supplied cooling water 142.

[0019] The monitoring device 16 is a device for monitoring whether the spray nozzle 141 is blocked, and includes: an acquisition unit 160, a memory unit 161, a setting unit 162, and a determination unit 163. The monitoring device 16 is, for example, a computer system such as a personal computer with arithmetic processing capabilities, and is configured with ROM, RAM, CPU, etc. The monitoring device 16 implements the functions of the acquisition unit 160, memory unit 161, setting unit 162, and determination unit 163 in software by executing various dedicated programs pre-stored in ROM, etc.

[0020] <Method for Monitoring Nozzle Blockage Condition> [Acquisition Step] Next, the method for monitoring the nozzle blockage condition of the spray nozzle 141 using the monitoring device 16 will be described. In the method for monitoring the nozzle blockage condition, firstly, the acquisition unit 160 acquires: a first value as the value of the flow meter (measured flow rate) installed on the piping attached to the continuous casting machine 1, and a second value as the value of at least one of the pressure gauge and valve opening installed on the piping (measured pressure or valve opening). The first and second values ​​are acquired in each zone of each cooling zone. In addition, the second value can be the value of either the pressure gauge or the valve opening, but from the point of view of the accuracy of detecting nozzle blockage, it is preferable to be the value of both. Furthermore, in the acquisition step, the acquired first and second values ​​are stored in the memory unit 161.

[0021] In the memory unit 161, in addition to the latest data that serves as the first and second values ​​obtained, the memory unit also stores past data that serves as the first and second values ​​in past operations. The memory unit 161 stores at least the past data for the first period described later, and when storing the latest data, the past data can be deleted starting from the oldest.

[0022] [Setting Process] Furthermore, in the nozzle clogging monitoring method of this embodiment, the setting unit 162 sets a threshold value of the second value relative to the first value over time from past data stored in the memory unit 161 (setting process). The threshold value is set as a lower limit and an upper limit value representing a predetermined range relative to a model (relationship) representing the relationship between the first value and the second value. This upper limit and lower limit value can also be set as a ±5σ check value of the relationship (model) obtained from past data. This check value is not limited to a ±5σ value, and can be arbitrarily set in a way that an abnormality can be detected when nozzle clogging occurs, or can be set in a range of, for example, 3σ to 6σ. In addition, the threshold value can also be set based on the measured value when nozzle clogging occurs. In this case, when a device that causes nozzle blockage is installed, the difference between the measured value when the nozzle is not blocked and the measured value when the nozzle is blocked is calculated in the device to set the upper and lower limits as the threshold values.

[0023] Furthermore, when the second value contains both pressure and valve opening, two threshold values ​​are set based on two models: a pressure-to-flow model and a valve opening-to-flow model. For example, when the threshold value is set based on a pressure-to-flow model from past data, as shown in Figure 3, the upper and lower threshold values ​​are set respectively by ±5σ relative to the model representing the relationship between flow rate and pressure. Moreover, the threshold value can also be set differently for each zone. In this case, for example, for zones with more nozzle blockage, it is preferable to set the threshold value based on the measured values ​​when nozzle blockage occurs.

[0024] In the setting process, the model is calculated from historical data of a predetermined period to set the threshold value. This predetermined period is also called the first period, and it is set in a way that ensures sufficient accuracy of the model, taking into account the usage conditions of the equipment, etc. For example, if it is a typical continuous casting machine 1, the first period can be set to 1 week.

[0025] The setting process is performed independently of the acquisition process. Furthermore, in the setting process, the setting of the threshold value is performed over time. That is, the threshold value changes over time. Moreover, the change of the threshold value can be performed under either change mode 1 or change mode 2 as described below.

[0026] (Change Mode 1) In Change Mode 1, the change of the threshold value is performed by the passage of a second period, which is a predetermined period. The second period is not particularly limited and can be set to, for example, a period of 1 day to 1 week. For example, when the second period is 1 week, after 1 week has passed since the previous setting of the threshold value, the setting unit 162 obtains the past data of the most recent first period stored in the memory unit 161, and sets the threshold value based on the obtained past data. In addition, the past data used for setting the threshold value can be the acquisition timing corresponding to the acquisition process, or it can be a time average of the data obtained from the acquisition process within 1 hour.

[0027] (Change Mode 2) In the case of Change Mode 2, the change of the threshold value is carried out not only through the same second period as in Change Mode 1, but also based on the change in the closest past data. That is, in Change Mode 2, the decision to change the threshold value is made based on the change in the closest past data in each second period.

[0028] The change in the closest historical data is the change in data for each of the plurality of the closest historical data periods that constitute a third period of a certain period. Here, the historical data used when setting the threshold value of the closest second value relative to the first value is referred to as the first data, and the historical data used in the calculation of the change in the third period is referred to as the second data. The change in data for each third period is obtained by measuring the distance between the second data and the first data in the third period in which the change is obtained. Specifically, the distance is the distance between the second data and the first data in the coordinate system represented by the first value and the second value. For example, as shown in Figure 4, the distance is obtained using a coordinate system with the flow rate value as the first value on the horizontal axis and the pressure (spray back pressure) value as the second value on the vertical axis. In this scenario, for each data point in the second data set, which consists of multiple data points, the distance to the nearest data point in the first data set is calculated. For example, as shown in Figure 4, when calculating the distance to a data point t in the second data set, the distance d between the nearest data point s in the first data set and data point t is calculated. Then, the distances to all data points constituting the second data set are calculated, and the average of each calculated distance is calculated. The standard deviation σ of the average distances calculated in each of the multiple third periods is then calculated as the variation. Next, it is determined whether each of the average values ​​of the multiple third periods falls within the range of "the overall average value of the multiple third periods ± 2σ", preferably within the range of "the overall average value of the multiple third periods ± 1σ". If the result of the determination is that all values ​​fall within this range, the threshold value is updated; otherwise, the threshold value is maintained.

[0029] One example is using the most recent 1 to 2 weeks of historical data as the most recent historical data, and setting the third period as 1 day. In this case, the change in the threshold value is determined by judging whether the standard deviation of the average distance of the above data over each day of the most recent 1 to 2 weeks is below a predetermined value.

[0030] [Judgment Process] After the acquisition process, if the latest data obtained by the judgment unit 163 in the acquisition process is outside the range of the latest threshold value set in the setting process, it is determined that a nozzle blockage has occurred in the spray nozzle 141 of the judged area. If the latest data is within the range of the threshold value, it is determined that no nozzle blockage has occurred. If it is determined that a nozzle blockage has occurred, the operator is notified that a nozzle blockage has occurred, and countermeasures such as inspection are taken as necessary.

[0031] In the method for monitoring nozzle blockage in this embodiment, the acquisition process is repeated at predetermined time intervals, and the determination process is repeated at the same frequency as or less than the acquisition process, thereby continuously monitoring the nozzle blockage during continuous casting.

[0032] Here, during the operation of the continuous casting machine 1, the nozzle orifice of the spray nozzle 141 is blocked due to the adhesion of scale and the like. The ease of blockage varies depending on the installation location, so cleaning is performed approximately once every 1 to 6 months depending on the blockage situation. The cleaning operation takes about 1 to 3 hours depending on the location, so it is difficult to increase the cleaning frequency. In addition, due to the individual differences between the new parts before and after replacement, the water volume and back pressure of the cooling water after replacement are sometimes significantly different from those before replacement. However, according to this embodiment, the water volume and back pressure of the cooling water in each zone after part replacement are monitored for a certain period of time, and the threshold value is changed when a stable stage is reached, so the influence of the value change at the time of part replacement can be eliminated. Therefore, the occurrence of blockage can be detected with high accuracy in the spray nozzle 141 of the continuous casting machine 1.

[0033] <Modifications> The present invention has been described above with reference to specific embodiments, but it is not intended to limit the invention by such description. By referring to the description of the present invention, the practitioner can understand other embodiments of the present invention containing various modifications in addition to the disclosed embodiments. Therefore, it should be understood that the embodiments of the invention described in the claims also include embodiments that individually or in combination contain the modifications described in this specification.

[0034] For example, in the above embodiment, the continuous casting machine 1 is configured to manufacture flat steel billets as casting sheets 3, but the present invention is not limited to this example. For example, the continuous casting machine 1 can also manufacture casting sheets with other cross-sectional shapes such as blocks or blanks.

[0035] Furthermore, when manufacturing flat steel billets of various widths on the continuous casting machine 1, the model or limit value can be set in multiple ways depending on the width of the flat steel billet.

[0036] Furthermore, in the above embodiments, a continuous casting machine is used as an example to illustrate the manufacturing equipment to which the present invention is applicable; however, the present invention is not limited to this example. Any manufacturing equipment to which the present invention is applicable can be a manufacturing device with a spray nozzle, such as a steel rolling mill or other manufacturing equipment. [Example]

[0037] Next, the embodiments performed by the inventors will be described. In the embodiments, similar to the above-described embodiments, when continuously casting steel in the continuous casting machine 1, a monitoring device 16 is used to monitor the nozzle blockage status. Then, the number of nozzle blockages detected is compared with the number of nozzle blockages that actually caused the abnormality.

[0038] In this embodiment, the setting process calculates the model from past data and sets the upper and lower limits as the threshold values ​​based on the ±5σ values ​​of the model. The first period for calculating the threshold value is set to 2 weeks. Furthermore, in the setting process, when changing the threshold value, the conditions of change mode 3 of the above embodiment are used. Specifically, in the closest 2-week period, the threshold value is changed when the variation of the daily average past data is between -5% and 5%. Furthermore, the first and second periods are set to 2 weeks. Moreover, in this embodiment, the back pressure and valve opening are used as the second value, and in the determination process, if either value exceeds the threshold value range, it is determined that nozzle blockage has occurred.

[0039] Figures 5 and 6 show the relationship between flow rate (first value), back pressure, and valve opening (second value) before and after equipment replacement, respectively. Figures 5 and 6 also show the data (first and second values) before and after equipment replacement, and the threshold values ​​determined by these data. In Figures 5 and 6, the data before equipment replacement is represented as model data, and the data after equipment replacement is represented as data at the time of equipment replacement. As shown in Figures 5 and 6, it can be confirmed that the model relating the first and second values ​​changes due to equipment replacement. Furthermore, it can be confirmed that even after equipment replacement, i.e., in the equipment without nozzle blockage, anomalies can sometimes be detected at the threshold values ​​before equipment replacement.

[0040] Figure 7 shows the number of nozzle blockages detected, the number of times nozzle blockages occurred, and the positive detection rate during periods A and B. The positive detection rate is the ratio of those detected to those that actually experienced nozzle blockage. Period A is the period during which the nozzle blockage status was monitored using conventional methods, and the threshold value was set based on the measured values ​​of the initially set equipment. Period B is the period during which the nozzle blockage status monitoring method of the aforementioned implementation type was used, and the threshold value was changed over time. Furthermore, period A is 8 months, and period B is 7 months. As shown in Figure 7, by changing the threshold value over time, the positive detection rate significantly increased from 33% to 75%, confirming a reduction in over-detection. [Simplified Explanation of the Diagram]

[0013] [Figure 1] is an explanatory diagram showing a continuous casting machine according to one embodiment of the present invention. [Figure 2] is a schematic diagram showing the secondary cooling zone. [Figure 3] is a schematic diagram showing the relationship between the model and the upper and lower limits. [Figure 4] is a graph illustrating the normalization in variation mode 2. [Figure 5] is a graph showing the relationship between flow rate and back pressure (spray back pressure) before and after equipment replacement in the embodiment. [Figure 6] is a graph showing the relationship between flow rate and valve opening before and after equipment replacement in the embodiment. [Figure 7] is a graph showing the detection and occurrence of nozzle blockage in the embodiment.

Claims

1. A nozzle clogging monitoring device comprising: an acquisition unit that acquires a first value as the value of a flow meter installed on a pipe attached to a manufacturing apparatus having a spray nozzle, and a second value as the value of at least one of a pressure gauge and a valve opening, as the latest data; a setting unit that sets a threshold value of the second value relative to the first value over time from past data of the first value and the second value; and a determination unit that determines that nozzle clogging has occurred when the latest data is outside the range of the threshold value.

2. The nozzle blockage monitoring device as described in claim 1, wherein when the change in the closest prior historical data is below a predetermined value, the aforementioned setting unit sets the aforementioned threshold value based on the closest prior historical data.

3. A method for monitoring nozzle blockage, comprising: an acquisition step, which acquires a first value as the value of a flow meter installed on a pipe attached to a manufacturing device having a spray nozzle, and a second value as the value of at least one of a pressure gauge and a valve opening, as the latest data; a setting step, which sets a threshold value of the second value relative to the first value over time from past data of the first value and the second value; and a determination step, which determines that nozzle blockage has occurred when the latest data is outside the range of the threshold value.

4. A method for manufacturing steel, wherein the steel is continuously cast by a continuous casting machine, wherein during continuous casting, a method for monitoring nozzle blockage as described in claim 3 is used to monitor the nozzle blockage of the spray nozzle of the aforementioned continuous casting machine.

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