JP3617423B2 - Method for estimating constrained breakout - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention determines that an abnormality occurs when changes in temperature measurement values by a plurality of thermocouples attached to a continuous casting mold satisfy a predetermined condition, and estimates the occurrence of a restrictive breakout based on the determination result. On how to do.
[0002]
[Prior art]
A constraining breakout is when seizure occurs between the mold and slab due to poor lubrication due to poor flow of mold powder between the mold and slab during continuous casting, and the slab is pulled downward. It means that the molten steel in the mold leaks to the outside when the solidified shell of the baked portion is broken and the broken portion is exposed from the lower end of the mold.
[0003]
By the way, if this constraining breakout occurs during continuous casting, the casting will be interrupted and the equipment will be damaged, resulting in a decrease in productivity. Measures are taken such as detecting abnormalities in changes in temperature measurement values due to thermocouples, estimating the occurrence of restrictive breakout based on the detection results, issuing an alarm, etc., and slowing down the casting speed.
[0004]
As a specific example of the method of estimating the occurrence of the constraining breakout, for example, as shown in FIG. 8, a plurality of thermocouple arrays a and b are embedded in the upper and lower two stages on the inner surface of the mold 1 to periodically change the temperature. sampled, change in temperature measurement values of one of the thermocouple a _n of the top row is determined to be abnormal, and a thermocouple in the lower row of the portion corresponding to the thermocouple abnormality determined as the top row a _n b Some estimate the occurrence of a restrictive breakout when it is determined that the change in the temperature measurement value of _n is abnormal. At this time, the abnormality determination of the temperature measurement value change of each thermocouple is normally determined by T _i , the latest value of the temperature measurement value for each thermocouple sampling periodically, T _i-1 , and the threshold value. When the value is ΔT, the condition of T _i −T _i−1 ≧ ΔT is satisfied.
[0005]
[Problems to be solved by the invention]
However, when the abnormality of the temperature measurement value change is determined when the condition of T _i −T _i−1 ≧ ΔT is satisfied in this way, the abnormality is determined because the responsiveness varies for each thermocouple. It is necessary to match the threshold value ΔT to a thermocouple with insensitive response, and as a result, erroneous detection (overdetection) occurs in a sensitive thermocouple, and the threshold value ΔT is a fixed value. For this reason, there is an inconvenience that erroneous detection occurs even when the temperature change of the inner surface of the mold (copper plate) due to a change in casting conditions, depletion of a slab, or the like is large.
[0006]
In addition, if the threshold value corresponding to the responsiveness is individually set for a plurality of thermocouples, and the threshold value is continuously changed according to the casting situation, the above-mentioned inconvenience is solved. However, setting such a threshold is too complicated and impractical.
The present invention has been made in view of such a technical background, and can improve the reliability of the constraining breakout estimation by making it possible to accurately and easily perform an abnormality determination of a temperature measurement value change by a temperature measuring device. An object of the present invention is to provide a method for estimating a constraining breakout that can be performed.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the method of estimating a constraining breakout according to the present invention is abnormal when a change in temperature measured by a plurality of temperature measuring devices attached to a continuous casting mold satisfies a predetermined condition. determined that, the determination result in a method for estimating the occurrence of restricted breakout based, the latest value of the temperature measurement values of the temperature measuring device which periodically samples T _i, the previous value T _{i −1} , where T _i ≧ F (σ) and T _i −, where ΔT is a threshold value, and F (σ) is a function with the standard deviation σ of the temperature measurement value of the temperature measuring device for a certain period of time as a variable. When both conditions of T _i-1 ≧ ΔT are satisfied, it is determined that the change in the measured temperature value is abnormal.
Here, F (σ) = T (avg) + kσ.
However, T (avg) : Average value of temperature measurement values in the past certain period including the previous value T _i-1 before the latest temperature measurement value T _i
σ: Standard deviation of temperature measurement values in the past certain period including the previous value T _i-1 before the latest temperature measurement value T _i
k: a constant determined empirically from the relationship between the measured temperature value and the breakout mark, etc.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram for explaining a method for estimating a constraining breakout as an example of an embodiment of the present invention, and FIG. 2 is a temperature measurement for each of a responsive sensitive thermocouple and a responsive insensitive thermocouple. FIG. 3 is a graph showing the relationship between values and time, FIG. 3 is a graph showing the relationship between each F (σ) value of a responsive sensitive thermocouple and a responsive insensitive thermocouple, and FIG. 4 is a controller. FIG. 5 is a flow chart for explaining the operation of FIG. 5, FIG. 5 is a graph showing abnormality determination in a sensitive thermocouple and a sensitive thermocouple when using the method of the present invention, and FIG. FIG. 7 is a graph showing a comparison of the number of alarms due to overdetection in the present invention example and the conventional example. FIG. 7 is a graph showing an abnormality determination in a sensitive thermocouple having a responsiveness and a thermocouple having an insensitive response. .
[0009]
In FIG. 1, reference numeral 1 is a continuous casting mold, 2 is a thermocouple (temperature measuring device) embedded in a plurality of upper and lower stages on the inner surface (copper plate) of the mold 1, and a temperature measurement value T by each thermocouple 2. Are sampled by the controller 3 at a predetermined cycle, and processing by a predetermined program is executed.
The controller 3 includes F (σ) calculation means 4, abnormality determination means 5 and alarm generation means 6. For convenience of explanation, the abnormality determination unit 5 will be described first.
[0010]
The abnormality determination means 5 determines whether or not the change in the measured temperature value is abnormal for each thermocouple 2, and when both conditions of the following expressions (1) and (2) are satisfied: It is determined that the change in temperature measurement value is abnormal.
T _i ≧ F (σ) (1)
T _i −T _i−1 ≧ ΔT (2)
However, F (σ): F (σ) is a value given by the calculation means 4 and a threshold value (variation value) for T _i .
T _i : Latest temperature measurement value T _i-1 : Previous temperature measurement value ΔT: Threshold value (fixed value: about 2 to 3 times the minimum temperature measurement unit of thermocouple) F (σ) calculating means 4 is intended to calculate the temperature value T _i previous past predetermined period (e.g., 10) function the standard deviation sigma and the variable temperature measurement values of F a (sigma) for each thermocouple every two and a sampling period, the following Calculated by equation (3).
[0011]
F (σ) = T (avg) + kσ (3)
However, T (avg): the average value of the measured values in the past fixed period (for example, 10 points) including the previous value T _i-1 before the latest measured value T _i (for example, point A in FIG. 2 is the latest measured value). If temperature value T _i , average of temperature measurement values of 10 points in B range)
σ: Standard deviation of temperature measurement values in a past fixed period (for example, 10 points) including the previous value T _i-1 before the latest temperature measurement value T _i (for example, point A in FIG. 2 is the latest temperature measurement value T _i ). Then, the standard deviation of the temperature measurement values of 10 points in B range)
k: a constant determined empirically from the relationship between the temperature measurement value and the breakout mark, and in this embodiment, it is set to k = 3.
[0012]
FIG. 3 shows the value of F (σ) calculated by the F (σ) calculating means 4 based on each temperature measurement value for two thermocouples 2 having different responsiveness. As can be seen from the figure, F (σ) is changed according to the responsiveness of the thermocouple 2 and is updated every sampling period and fluctuates according to the casting condition.
The alarm generating means 6 has a change in the measured temperature value of any one of the upper thermocouples 2 determined to be abnormal by the abnormality determining means 5 and a lower part of the part corresponding to the upper thermocouple 2 determined to be abnormal. When a change in the measured temperature value of the thermocouple 2 is determined to be abnormal by the abnormality determining means 5, the occurrence of a restrictive breakout is estimated, an alarm is displayed on a monitor screen or an alarm sound is generated.
[0013]
Next, the operation of the controller 3 will be described with reference to FIG. In FIG. 4, step S2 corresponds to the F (σ) calculating means 4, steps S3 to S5 correspond to the abnormality determining means 5, and steps S6 to S8 correspond to the alarm generating means 6, respectively.
First, the temperature measurement value T by each thermocouple 2 was periodically sampled in step S1, the standard deviation of the temperature measurement values of the latest temperature measurement value T _i previous past predetermined period (e.g., 10) sigma in step S2 The function F (σ) as a variable is calculated by the above formula (3) for each thermocouple 2 and for each sampling period, and the process proceeds to step S3.
[0014]
In step S3, the latest temperature measurement value _Ti and the function F (σ) are compared for each thermocouple 2, and if the above equation (1) is satisfied, the process proceeds to step S4.
In step S4, (latest measured temperature value T _i -previous measured temperature value T _i-1 ) and a threshold value ΔT are compared, and if the above equation (2) is satisfied, it is determined that the change in measured temperature value is abnormal. (Step S5).
[0015]
In step S6, it is determined whether or not the abnormality determination in step S5 has been made for the upper thermocouple 2. If the abnormality determination has been made for the upper thermocouple 2, the process proceeds to step S7.
In step S7, it is determined whether or not the abnormality determination in step S5 has been performed on the lower thermocouple 2 in the region corresponding to the upper thermocouple 2 determined in step S6, and the abnormality determination is performed on the upper thermocouple 2. If it is made for the lower thermocouple 2 of the corresponding part, the process proceeds to step S8 on the assumption that a restrictive breakout occurs.
[0016]
In step S8, an alarm signal is output to an output device such as a monitor screen or a voice, and measures such as slowing down the casting speed when the alarm is recognized are taken.
As is clear from the above description, in this embodiment, in addition to the conventionally used threshold value ΔT, a threshold value corresponding to the response of the thermocouple 2 to the recently measured temperature value T _i , that is, Since the threshold value F (σ) reflecting the variation in the measured temperature value of each thermocouple 2 is set by calculation, overdetection by the sensitive thermocouple 2 and the insensitive thermocouple 2 are insensitive. In addition, the threshold value F (σ) is not only changed for each thermocouple 2 but also recalculated and updated every sampling period. It is possible to prevent false detection when there is a large temperature change on the mold inner surface (copper plate) due to changes in conditions or depletion of the slab. As a result, it is possible to accurately and easily determine abnormalities in temperature measurement changes by the thermocouple 2. Can be done, restraint breakout Certain reliability can be increased.
[0017]
In the above embodiment, the change in the measured temperature value of any one of the upper thermocouples 2 is determined to be abnormal by the abnormality determining means 5 and the part corresponding to the upper thermocouple 2 determined to be abnormal is determined. When the change in the temperature measurement value of the lower thermocouple 2 is determined to be abnormal by the abnormality determination means 5, the occurrence of the restrictive breakout is estimated, but this is not necessarily limited to this. The occurrence of a restrictive breakout may be estimated based on the abnormality determination result.
[0018]
Moreover, in the said embodiment, although the case where the several thermocouple 2 was embed | buried in the upper and lower two steps in the inner surface (copper plate) of the casting_mold | template 1 was taken as an example, it is not limited to this, It is only one step or three or more steps above and below The thermocouple 2 may be embedded.
[0019]
【Example】
For one thermocouple, the same conditions other than the abnormality judgment method are used in the same continuous casting machine, and the number of times of abnormality judgment when using the example of the present invention is shown in FIG. 5, before using the method of the present invention, that is, T _i − FIG. 6 shows the number of abnormality determinations when it is determined that there is an abnormality when the condition of T _i-1 ≧ ΔT is satisfied (conventional example). FIG. 7 shows a comparison of the number of occurrences / month of breakout alarms due to overdetection of the present invention example and the conventional example. As is apparent from the figure, the number of breakout alarms due to overdetection is significantly reduced in the example of the present invention compared to the conventional example, and the reliability of the constraining breakout estimation is increased.
[0020]
【The invention's effect】
As is clear from the above description, according to the present invention, the abnormality determination of the temperature measurement value change by the temperature measuring device can be performed accurately and easily, so that the reliability of the constraining breakout estimation can be increased. The effect is obtained.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram for explaining a constraining breakout estimation method which is an example of an embodiment of the present invention.
FIG. 2 is a graph showing the relationship between each measured temperature value and time of a thermocouple having a sensitive response and a thermocouple having an insensitive response;
FIG. 3 is a graph showing the relationship between each F (σ) value and time of a thermocouple having a sensitive response and a thermocouple having an insensitive response.
FIG. 4 is a flowchart for explaining the operation of the controller.
FIG. 5 is a graph showing abnormality determination in a thermocouple having a responsive sensitivity and a thermocouple having an insensitive response when the method of the present invention is used. FIG. 6 is a graph showing the responsiveness when using a conventional method. It is a graph which shows the abnormality determination in a sensitive thermocouple and a responsive insensitive thermocouple. [FIG. 7] It is a graph which shows the comparison of the alarm frequency by the overdetection of the example of this invention, and a prior art example.
FIG. 8 is an explanatory diagram for explaining a conventional method for estimating a constraining breakout.
[Explanation of symbols]
1 ... mold for continuous casting 2 ... thermocouple (temperature measuring device)
3 ... Controller 4 ... F (σ) computing means 5 ... Abnormality judging means 6 ... Alarm generating means

Claims (1)

In a method for determining the occurrence of a constraining breakout based on the determination result based on the determination result when a change in temperature measured by a plurality of temperature measuring devices attached to a continuous casting mold satisfies a predetermined condition. There,
The latest value of the temperature measurement value of the temperature measuring device that is periodically sampled is T _i , the previous value is T _i-1 , the threshold value is ΔT, and the standard deviation σ of the temperature measurement value of the temperature measurement device for a certain period in the past. When F (σ) is a function having a variable as a variable, a change in temperature measurement value is abnormal when both conditions of T _i ≧ F (σ) and T _i −T _i−1 ≧ ΔT are satisfied. A method for estimating a constraining breakout, characterized in that it is determined to be.
Here, F (σ) = T (avg) + kσ.
However, T (avg) : Average value of temperature measurement values in the past certain period including the previous value T _i-1 before the latest temperature measurement value T _i
σ: Standard deviation of temperature measurement values in the past certain period including the previous value T _i-1 before the latest temperature measurement value T _i
k: Constant determined empirically from the relationship between temperature measurement value and breakout mark

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