Nozzle blockage condition monitoring device and monitoring method, and steel manufacturing method

Abstract

Provided are a nozzle blockage condition monitoring device and monitoring method, as well as a steel manufacturing method. The nozzle blockage condition monitoring device comprises: an acquisition unit (160) that acquires a first value and a second value as newest data, said first value being the value of a flow meter that is provided to piping attached to manufacturing equipment having a spray nozzle, and said second value being the value of at least one among a pressure gauge and valve openness; a setting unit (162) that sets, over time, a threshold value for the second value with respect to the first value, on the basis of past data for the first value and the second value; and a determination unit (163) that determines that nozzle blockage has occurred when the newest data falls outside the range of the threshold value.

Description

Device and method for monitoring nozzle clogging status, and steel manufacturing method

[0001] The present invention relates to a device and a method for monitoring a nozzle clogging state, and a method for manufacturing steel.

[0002] In continuous casting of steel using a continuous casting machine, cooling water is sprayed onto the cast slab from a spray nozzle (nozzle) to cool the slab (secondary cooling). Conventionally, in such equipment, a pressure gauge has been installed in the piping to monitor for clogging of the spray nozzle, and an abnormality has been detected when the pressure value relative to the reference flow rate exceeds a preset threshold.

[0003] Patent Document 1 describes a secondary cooling method for continuous casting in which cooling water is supplied to the peripheral surface of a cast slab while monitoring whether the supply pressure and / or the flow rate per unit time of cooling water supplied from a nozzle falls within a certain range along the supply pressure-flow rate curve of the nozzle.

[0004] Furthermore, Patent Document 2 describes a method for determining 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 pattern, and determining that there is an abnormality in the nozzle if either or both of the average value of the back pressure difference and the difference between the average value of the valve opening are equal to or greater than a predetermined value.

[0005] JP 2001-179141 A Japanese Patent No. 3373007 A

[0006] However, the methods described in Patent Documents 1 and 2 both continue monitoring based on preset thresholds. Therefore, even after replacing parts due to malfunctions or end of life, the water volume and back pressure values ​​may change due to individual differences in the replaced parts. In such cases, even if there are no operational abnormalities with new parts, the data may indicate an abnormality, often resulting in failure to achieve the intended purpose of monitoring for clogging. When an abnormality is detected, the line must be stopped and checked, resulting in overdetection of abnormalities and a significant decrease in operational efficiency. On the other hand, if the pressure after replacement is lower than the model originally expected, even if pressure clogging occurs more than before, it is not detected as an abnormality unless the clogging progresses, resulting in major problems.

[0007] The present invention has been made in light of the above-mentioned problems, and has an object to provide a monitoring device and monitoring method for the nozzle clogging state, and a steel manufacturing method, which are capable of accurately detecting the occurrence of clogging in the spray nozzle of a continuous casting machine.

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

[0009] (2) In the nozzle clogging status monitoring device described in (1) above, the setting unit sets the threshold value from the most recent past data when the amount of variation in the most recent past data is equal to or less than a predetermined value.

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

[0011] (4) According to one aspect of the present invention, there is provided a method for producing steel by continuously casting steel using a continuous casting machine, wherein, during continuous casting, nozzle clogging of the spray nozzles of the continuous casting machine is monitored using the method for monitoring a nozzle clogging state described in (3) above.

[0012] According to one aspect of the present invention, there are provided a device and a method for monitoring the nozzle clogging state, and a method for producing steel, which are capable of accurately detecting the occurrence of clogging in the spray nozzle of a continuous casting machine.

[0013] FIG. 1 is an explanatory diagram showing a continuous casting machine according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a secondary cooling zone. FIG. 3 is a schematic diagram showing the relationship between a model and upper and lower limit values. FIG. 4 is a graph explaining standardization in change pattern 2. FIG. 5 is a graph showing the relationship between flow rate and back pressure (spray back pressure) before and after equipment replacement in an example. FIG. 6 is a graph showing the relationship between flow rate and valve opening before and after equipment replacement in an example. FIG. 7 is a graph showing the detection status and occurrence status of nozzle clogging in an example.

[0014] In the following detailed description, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, identical or similar parts are designated by identical or similar reference numerals, and redundant explanations will be omitted. The drawings are schematic and may differ from the actual product. Furthermore, the embodiments shown below exemplify devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not specify the materials, structure, arrangement, etc. of component parts as described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

[0015] <Continuous Casting Machine and Device for Monitoring Nozzle Clogging Status> As shown in Fig. 1 , a device 16 for monitoring nozzle clogging status according to this embodiment of the present invention is provided in a continuous casting machine 1. The continuous casting machine 1 continuously casts steel to produce a slab 3. The type of continuous casting machine 1, such as a curved bending type or a vertical bending type, is not particularly limited. In this embodiment, the continuous casting machine 1 produces, as the slab 3, a slab having a rectangular cross section, which is the shape of a cross section perpendicular to the longitudinal direction.

[0016] The continuous casting machine 1 includes a ladle 10, a tundish 11, a mold 12, a plurality of rolls 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 ladle 10 is supplied to the tundish 11, which is an intermediate container, and then supplied from the tundish 11 to the mold 12. The molten steel 2 supplied to the mold 12 is cooled (primary cooling) in the mold 12 to form a solidified shell. This solidified shell is then extracted and further cooled (secondary cooling) in the secondary cooling zone 14 to produce a slab 3. The slab 3 is then cut to a predetermined length by a cutting device 15.

[0017] The secondary cooling zone 14 is an area where the slab 3 is cooled by spraying cooling water from spray nozzles. The secondary cooling zone 14 is made up of multiple cooling zones, and in the example shown in FIG. 1 , it consists of three cooling zones 14a to 14c. Each cooling zone in the secondary cooling zone 14 is made up of multiple zones arranged in the casting direction and the strip width direction, and approximately 20 to 60 spray nozzles are provided in each zone. The casting direction is the direction in which the slab 3 moves within the continuous casting machine 1 (the longitudinal direction of the slab 3 from the mold 12 toward the cutting device 15 in FIG. 1 ), and the strip width direction is the width direction of the slab 3 (the front-to-rear direction in FIG. 1 ).

[0018] FIG. 2 is an explanatory diagram illustrating the secondary cooling zone 14, showing a plan view from the casting direction at a position between adjacent rolls 13 in the casting direction. As shown in FIG. 2, multiple spray nozzles 141 are provided in the gaps between adjacent rolls 13 in the casting direction. The spray nozzles 141 are water spray nozzles, air mist spray nozzles, or the like, and spray cooling water 142 onto the cast slab 3. The cooling water 142 supplied to the spray nozzles 141 is supplied to each cooling zone via piping (not shown), and the flow rate is adjusted by a flow control valve (not shown) provided in the piping. The flow rate is adjusted by adjusting the opening (valve opening) of the flow control valve. Each piping is also provided with a flow meter (not shown) for measuring the flow rate of the supplied cooling water 142 and a pressure gauge (not shown) for measuring the pressure (water pressure) of the supplied cooling water 142.

[0019] The monitoring device 16 is a device for monitoring the nozzle clogging status, which monitors whether clogging has occurred in the spray nozzle 141, and includes an acquisition unit 160, a storage 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 having an arithmetic processing function, and is configured with a ROM, a RAM, a CPU, etc. The monitoring device 16 executes various dedicated programs stored in advance in the ROM, etc., thereby realizing the functions of the acquisition unit 160, the storage unit 161, the setting unit 162, and the determination unit 163, which will be described later, in software.

[0020] <Method for Monitoring Nozzle Clogging> [Acquisition Step] A method for monitoring the nozzle clogging state of the spray nozzle 141 using the monitoring device 16 will be described. In the method for monitoring the nozzle clogging state, the acquisition unit 160 first acquires a first value, which is a value (a measured value of flow rate) from a flow meter provided on a piping attached to the continuous casting machine 1, and a second value, which is a value (a measured value of pressure or valve opening) from a pressure gauge provided on the piping (a measured value of pressure or valve opening). The first and second values ​​are acquired for each zone in each cooling zone. The second value may be either a value from the pressure gauge or a value from the valve opening, but from the viewpoint of accuracy in detecting nozzle clogging, it is more preferable that the second value be both values. Furthermore, in the acquisition step, the acquired first and second values ​​are stored in the memory unit 161.

[0021] In addition to the latest data, which are the acquired first and second values, past data, which are the first and second values ​​in past operations, are also stored in the storage unit 161. The storage unit 161 may store at least past data for a first period, which will be described later, and the past data may be deleted, starting with the oldest, every time the latest data is stored.

[0022] [Setting Step] In the nozzle clogging status monitoring method of this embodiment, the setting unit 162 sets a threshold value for the second value relative to the first value over time based on past data stored in the storage unit 161 (setting step). The threshold value is set as a lower limit value and an upper limit value within a predetermined range for a model (relational equation) showing the relationship between the first value and the second value. The upper limit value and the lower limit value may be set as a test value of ±5σ of the relational equation (model) obtained from past data. The test value is not limited to ±5σ and can be set arbitrarily so that the occurrence of nozzle clogging can be detected as an abnormality, for example, in the range of 3σ to 6σ. The threshold value may also be set based on the actual value when nozzle clogging occurs. In this case, the difference between the actual value when the equipment in which the nozzle clogging occurred was installed, i.e., when the equipment in question was not experiencing nozzle clogging, and the actual value when nozzle clogging occurred is calculated, and the upper limit value and the lower limit value are set as threshold values.

[0023] Furthermore, when the second value includes two values, pressure and valve opening, two thresholds are set based on two models: a model of pressure relative to flow rate, and a model of valve opening relative to flow rate. For example, when the threshold is set based on a model of pressure relative to flow rate in past data, as shown in FIG. 3, values ​​of ±5σ are set as upper and lower threshold values ​​for the model, which is a relationship between flow rate and pressure. Furthermore, different threshold values ​​may be set for each zone. In this case, for example, for a zone where nozzle clogging frequently occurs, it is preferable to set a threshold based on the actual value when the above-mentioned nozzle clogging occurred.

[0024] In the setting step, a threshold value is set by calculating a model from past data for a predetermined period. This predetermined period is also referred to as a first period, and is set depending on the equipment usage status, etc., so that the accuracy of the model is sufficient. For example, in the case of a general continuous casting machine 1, the first period may be set to one week.

[0025] The setting step is performed independently of the acquisition step. In addition, in the setting step, the threshold is set over time. That is, the threshold is changed over time. Furthermore, the threshold may be changed under the conditions of change pattern 1 or change pattern 2 described below.

[0026] (Change Pattern 1) In the case of change pattern 1, the threshold is changed when a second period, which is a predetermined period, elapses. The second period is not particularly limited, and can be set, for example, as a period of one day to one week. For example, if the second period is one week, when one week has elapsed since the previous threshold was set, the setting unit 162 acquires past data for the most recent first period stored in the storage unit 161 and sets the threshold from the acquired past data. Furthermore, the past data used to set the threshold may be data corresponding to the acquisition timing in the acquisition process, or may be data acquired in the acquisition process that is averaged over one hour.

[0027] (Change Pattern 2) In change pattern 2, the threshold is changed according to the amount of change in the most recent past data, in addition to the passage of the second period as in change pattern 1. In other words, in change pattern 2, whether or not to change the threshold is determined for each second period according to the amount of change in the most recent past data.

[0028] The amount of variation in the most recent past data is the amount of variation in the data for each third period, which is a plurality of fixed periods, in the most recent past data. Here, the past data used when setting the threshold value of the second value for the most recent first value is referred to as the first data, and the past data for the third period used to calculate the amount of variation is referred to as the second data. The amount of variation in the data for each third period is calculated as the distance from the first data to the second data for the third period for which the amount of variation is being calculated. Specifically, the calculated distance is the distance between the second data and the first data in a coordinate system represented by the first value and the second value. For example, as shown in FIG. 4, the distance is calculated using a coordinate system in which the horizontal axis represents the flow rate value, which is the first value, and the vertical axis represents the pressure (spray back pressure), which is the second value. In this case, for each piece of second data consisting of multiple pieces of data, the distance to the closest piece of first data consisting of multiple pieces of data is calculated. For example, as shown in FIG. 4, when the distance is calculated for data t, which is one of the second data, the distance d between data s, which is the closest piece of first data, and data t is calculated. Then, distances are calculated for all data constituting the second data, and an average value is calculated for each calculated distance. The standard deviation σ of the average distances calculated for each of the plurality of third periods is then determined as the amount of fluctuation. It is then determined whether each of the average values ​​for the plurality of third periods falls within the range of "the average value for all of the plurality of third periods ±2σ," preferably within the range of "the average value for all of the plurality of third periods ±1σ." If the result of the determination is that all values ​​fall within the range, the threshold is updated; otherwise, the threshold remains unchanged.

[0029] As an example, the most recent past data may be data from the most recent one to two weeks, and the third period may be one day. In this case, whether the average value of the distances of the data for each day of the most recent one to two weeks is equal to or less than a predetermined standard deviation value for the one to two weeks is used to determine whether the threshold should be changed.

[0030] [Determination Process] After the acquisition process, if the latest data acquired in the acquisition process is outside the range of the most recent threshold set in the setting process, the determination unit 163 determines that a nozzle clog has occurred in the spray nozzle 141 of the determined zone. If the latest data is within the threshold, it is determined that a nozzle clog has not occurred. If it is determined that a nozzle clog has occurred, the operator is notified of the occurrence of the nozzle clog, and appropriate measures such as inspection are taken as necessary.

[0031] In the method for monitoring the nozzle clogging status according to this embodiment, the acquisition process is repeated at predetermined time intervals, and the determination process is repeated at the same frequency as the acquisition process or at a lower frequency than the acquisition process, thereby continuously monitoring the nozzle clogging status while continuous casting is being performed.

[0032] During operation of the continuous casting machine 1, the nozzle holes of the spray nozzle 141 become clogged due to the adhesion of scale and other substances. The susceptibility of nozzle hole clogging varies depending on the location of the equipment, and cleaning work is performed approximately once every one to six months depending on the clogging occurrence situation. Because cleaning work takes approximately one to three hours depending on the location, it is difficult to increase the frequency of cleaning. Furthermore, due to individual differences between new parts before and after replacement, the cooling water volume and back pressure after replacement may differ significantly from the cooling water volume and back pressure before replacement. However, according to this embodiment, the cooling water volume and back pressure of each zone after part replacement are monitored for a certain period of time and the thresholds are changed when they become stable, thereby eliminating the influence of value changes during part replacement. This allows for accurate detection of clogging in the spray nozzle 141 of the continuous casting machine 1.

[0033] <Modifications> Although the present invention has been described above with reference to specific embodiments, it is not intended that the invention be limited by these descriptions. By referring to the description of the present invention, other embodiments of the present invention that include various modifications in addition to the disclosed embodiments will be apparent to those skilled in the art. Therefore, it should be understood that the embodiments of the invention described in the claims also encompass embodiments that include these modifications described herein, either alone or in combination.

[0034] For example, in the above embodiment, the continuous casting machine 1 produces a slab as the cast piece 3, but the present invention is not limited to this example. For example, the continuous casting machine 1 may produce a cast piece having another cross-sectional shape, such as a bloom or a billet.

[0035] Furthermore, when the continuous casting machine 1 produces slabs of various widths, multiple models and thresholds may be set according to the width of the slabs.

[0036] Furthermore, in the above embodiment, a continuous casting machine has been described as an example of manufacturing equipment to which the present invention is applied, but the present invention is not limited to such an example. The equipment to which the present invention can be applied may be any manufacturing equipment having a spray nozzle, and may be, for example, other manufacturing equipment such as a steel rolling equipment.

[0037] An example conducted by the present inventors will now be described. In the example, similar to the above embodiment, the nozzle clogging state was monitored using the monitoring device 16 when steel was continuously cast using the continuous casting machine 1. The number of cases in which nozzle clogging was detected and the number of cases in which nozzle clogging actually occurred as an abnormality were investigated.

[0038] In the example, in the setting process, a model was calculated from past data, and values ​​of ±5σ of the model were set as upper and lower threshold values. In this case, the first period for calculating the threshold was set to two weeks. Furthermore, in the setting process, the conditions of change pattern 3 in the above embodiment were used when changing the threshold. Specifically, the threshold was changed when the average daily fluctuation of past data over the most recent two-week period was between -5% and 5%. Furthermore, the first and second periods were set to two weeks. Furthermore, in the example, two values, back pressure and valve opening, were used as the second value, and in the determination process, it was determined that nozzle clogging had occurred if either value exceeded the threshold range.

[0039] 5 and 6 show the relationship between the flow rate (first value) and the back pressure and valve opening (second value) before and after the equipment replacement, respectively. FIGS. 5 and 6 show data (first and second values) before and after the equipment replacement, and thresholds based on these data. Note that in FIGS. 5 and 6, the data before the equipment replacement is shown as model data, and the data after the equipment replacement is shown as equipment replacement data. As shown in FIGS. 5 and 6, it was confirmed that the model, which is the relationship between the first value and the second value, changes due to the equipment replacement. It was also confirmed that the thresholds before the equipment replacement may sometimes detect an abnormality even after the equipment replacement, i.e., even when no nozzle clogging has occurred.

[0040] FIG. 7 shows the number of nozzle clog detections, the number of nozzle clog occurrences, and the correct detection rate for periods A and B. The correct detection rate is the percentage of nozzle clogs that actually occurred among the detected nozzle clogs. Note that period A was a period in which the nozzle clog status was monitored using a conventional method, with the threshold set based on the performance of the initially installed equipment. Period B was a period in which the nozzle clog status monitoring method according to the above embodiment was used, with the threshold changed over time. Furthermore, period A lasted eight months, and period B lasted seven months. As shown in FIG. 7 , it was confirmed that by changing the threshold over time, the correct detection rate significantly improved from 33% to 75%, and false detections were reduced.

[0041] REFERENCE SIGNS LIST 1 continuous casting machine 10 ladle 11 tundish 12 mold 13 roll 14 secondary cooling zone 141 spray nozzle 142 cooling water 15 cutting device 16 monitoring device 160 acquisition unit 161 memory unit 162 setting unit 163 determination unit 2 molten steel 3 cast piece

Claims

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

2. The nozzle clogging status monitoring device according to claim 1, wherein the setting unit sets the threshold value from the most recent past data when the amount of fluctuation in the most recent past data is equal to or less than a predetermined value.

3. A method for monitoring a nozzle clogging situation, comprising: an acquisition step of acquiring, as the latest data, a first value which is the value of a flow meter installed in a pipe attached to a manufacturing facility having a spray nozzle, and a second value which is the value of at least one of a pressure meter and a valve opening; a setting step of setting a threshold value for the second value relative to the first value over time based on past data of the first value and the second value; and a determination step of determining that a nozzle clogging has occurred when the latest data is outside the range of the threshold value.

4. A method for producing steel in which steel is continuously cast using a continuous casting machine, wherein nozzle clogging of the spray nozzles of the continuous casting machine is monitored during continuous casting using the method for monitoring nozzle clogging status described in claim 3.

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