JPH10230353A - Detection of flowing out of slag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the mixture of slag by quickly and surely detecting the slag flowed out into discharging stream of molten metal. SOLUTION: Brightness of the discharging stream of the molten metal is measured with a CCD camera to make a histogram of brightness signals and the histogram is smoothened, and after permuting into the frequency of the brightness level, the brightness value divided into the back ground and the brightness level of molten metal with a discriminating analyzing method is set as a threshold value (1) and the brightness value at high brightness side corresponding to 2σor 3σ as the normal distribution to the brightness distribution of the molten metal from the brightness of the molten metal is set as a threshold value (2) and the brightness value of [the threshold value (2)×2- the threshold value (1)] is set to a threshold value (3). Total frequency of the brightness distribution of [the threshold value (1) - the threshold value (2)], is calculated as the total frequency of the molten metal, total frequency of the brightness distribution of [the threshold value (2) - the threshold value (3)] is calculated as the total frequency of the slag and the brightness distribution of [the threshold value (3) - the max. brightness level] is calculated as the total frequency of abnormally high brightness part caused by disturbance. The slag mixed in the discharging stream of the molten metal is detected from the total frequency of the abnormally high brightness part, the variation of the total frequency ratio of the molten metal and the slang and whether the abnormally high brightness part exists or not.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slag outflow detecting method capable of quickly and accurately detecting a discharge flow of a molten metal, for example, slag mixed in molten steel discharged from a ladle during steel production.

[0002]

2. Description of the Related Art Steel is produced by melting a raw material such as scrap at a high temperature. However, impurities in the raw material and the added treating agent become slag and float on the molten steel due to a difference in specific gravity. . If this slag is mixed with steel, it will cause deterioration of steel quality, so slag mixed into molten steel is quickly detected,
Preventing slag contamination is extremely important for quality control.

Conventionally, the detection of mixed slag has been performed by a method of visual observation by a human. However, in this method, it is difficult to perform objective management because of a large factor depending on human skill and intuition. For this reason, a method for detecting slag using a difference in physical properties between molten steel and slag, for example, a difference in viscosity or electrical conductivity has been developed, but a sufficient result in terms of accuracy has not been obtained.

A method of optically detecting slag utilizing the difference in luminance between molten steel and slag has also been developed. For example, Japanese Patent Application Laid-Open No. 2-251362 discloses a method for measuring the radiant energy distribution in the width direction of molten metal. Then, the continuous maximum width portion of the measurement result is detected as the diameter of the molten metal flow, and the width of the diameter of the molten metal flow and its integral value are measured over time, and an increase in both values is detected. A slag outflow detection method for determining that slag has flowed out has been proposed. However,
Since the monitoring area to be measured is only one horizontal line in the width direction of the molten metal flow, if the outlet of the molten metal fluctuates up and down, it must deviate from the monitoring area and manually set the position each time. Has the disadvantage of having to
Furthermore, since the binarization process is performed using a fixed threshold value, the brightness changes depending on the type of molten metal, so it is necessary to set a threshold value for each type of target molten metal, resulting in lower detection accuracy and stability. There are also some drawbacks.

Japanese Patent Application Laid-Open No. Hei 7-260696 discloses a process in which the surface of a tapping stream flowing from a converter to a ladle is photographed by a television camera or a CCD camera, and the image is output to an image processing / analyzing apparatus at a constant period. In the image processing analysis device, every time there is an input image in the set monitoring area in the image, a gray level corresponding to the luminance is obtained for each pixel in the area, and then the average gray level in the monitoring area is calculated. A slag outflow detection method comprising the steps of: performing a comparison operation with a moving average value up to the previous time every time an average gray level is obtained, and determining a “slag outflow” when the difference exceeds a set value. It has been disclosed. However, this method obtains a gray level corresponding to the luminance for each pixel of the input image at a fixed period, calculates the average gray level in the monitoring area, and calculates the average gray level with the moving average value up to the previous time every time the average gray level is obtained. Since the difference is calculated, the average gray level, that is, the change in the average luminance level is compared.For example, when a small amount of slag is mixed, the change in the average luminance level is small, so that the detection becomes difficult. There is a problem that the slag outflow cannot be detected quickly and accurately, for example, the timing of detecting the slag outflow is delayed.

Further, when the temperature of a molten metal, for example, molten steel, has been lowered, oxygen is directly blown onto the molten steel to increase the temperature of the molten steel, or the molten steel outlet of the ladle or the molten steel inflow port of the tundish tends to be closed. Means such as blowing out oxygen to remove the adhered molten steel when this occurs are taken.However, the high-intensity light of the combustion flame due to the oxygen injection is reflected on the molten steel to increase the luminance. Is erroneously determined to be slag outflow. Further, a similar problem occurs when high-brightness light such as strobe light or splash light is reflected on the molten metal.

In order to solve the problems such as erroneous recognition of outflow slag or deterioration of detection accuracy due to these disturbances, the present inventors measured the luminance of the discharge flow of molten metal with a CCD camera and measured the luminance signal histogram. After the histogram is smoothed and replaced with the frequency of the luminance level, the low-temperature side threshold that is divided into the luminance level of the background and the molten metal by the discriminant analysis method, and the luminance distribution of the molten metal from the luminance of the molten metal The luminance value on the high luminance side corresponding to 2σ or 3σ as a normal distribution is set as the high temperature side threshold, and the total frequency ratio of the molten metal and the slag is calculated from the total frequency of the luminance distribution in each range separated by the threshold value. The slag detection method is characterized in that the slag is calculated and the slag mixed into the discharge stream of the molten metal is detected from the change in the total frequency ratio (Japanese Patent Application No. 8-81717).
No. 5).

[0008]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application No. Hei.
The slag detection method of No. 175 automatically sets a threshold value using a histogram of a luminance signal of a molten metal, calculates a frequency of a luminance distribution of a background, molten metal, slag, and the like from the histogram, and calculates a frequency ratio of the frequency ratio. Since the outflow of slag is detected from the change, the incorporation of slag can be detected with high accuracy. However, when the amount of oxygen to be blown is small and the brightness level is low, the improvement in brightness due to the blowing of oxygen may be erroneously determined as a slag brightness distribution.

In other words, in the slag detection method of Japanese Patent Application No. 8-18175, the luminance level due to disturbance such as oxygen blowing is set to 250 to 255 and the high temperature side threshold is set. Although there is no problem, when the amount of oxygen is small and the luminance level does not exceed 250, an increase in luminance due to oxygen blowing may be erroneously recognized as slag outflow. In addition, since the increase in the brightness level varies depending on the type of steel, if the high brightness level due to disturbance such as oxygen blowing is set within a certain range of 250 to 255, there is a problem that slag outflow cannot be detected with high accuracy.

As a result of further research for solving the above problems, the present inventors have automatically set a threshold value using a histogram of a luminance signal of a molten metal, By calculating the frequency of the luminance distribution of the abnormally high luminance part due to slag and disturbance, it was found that the mixing of the slag can be detected accurately from the change in the frequency ratio between the molten metal and the slag and the presence or absence of the abnormally high luminance part. .

The present invention has been developed on the basis of the above findings, and its object is to quickly and accurately detect slag flowing into a discharge flow of molten metal regardless of the level of an abnormally high luminance portion due to disturbance. It is an object of the present invention to provide a slag outflow detection method capable of performing the above.

[0012]

According to the present invention, there is provided a method for detecting slag outflow according to the present invention, comprising measuring a luminance of a discharge flow of a molten metal with a CCD camera, generating a histogram of a luminance signal, and generating a histogram of the luminance signal. Is smoothed and replaced by the frequency of the luminance level, and then the threshold is divided into the luminance level of the molten metal by the discriminant analysis method.
A luminance value on the high luminance side corresponding to σ is set as a threshold, and a luminance value of [threshold × 2−threshold] is set as a threshold. The frequency is calculated as the total frequency of the molten metal, the total frequency of the luminance distribution from the threshold to the threshold is calculated as the total frequency of the slag, and the luminance distribution from the threshold to the highest luminance level is calculated as the total frequency of the abnormally high luminance part due to disturbance. , Detecting the slag mixed into the discharge flow of the molten metal from the total frequency of the abnormally high luminance portion, the change in the total frequency ratio of the molten metal and the slag, and the presence or absence of the abnormally high luminance portion. .

[0013]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to
Observed by a CD camera, the luminance signal is input to an arithmetic processing unit having a histogram counter, and a histogram is obtained.
That is, the horizontal axis represents luminance, and the vertical axis represents frequency, and the luminance level is 0.
After creating a luminance distribution map of 255 to 255, in order to cut high-luminance disturbance light such as oxygen blowing, luminance levels 0 to 2
A threshold value and a threshold value are set in the range of 00, and a luminance level obtained by adding the threshold value to the difference between the threshold value and the threshold value is set as the threshold value. The threshold value thus set, the threshold value and the threshold value are divided into a luminance distribution of the background, a luminance distribution of the molten metal, a luminance distribution of the slag, and a luminance distribution of an abnormally high luminance portion due to disturbance. Slag is calculated from the total frequency of the abnormally high luminance part, the ratio of the total frequency of molten metal and slag, and the ratio of the total frequency, and the presence or absence of the abnormally high luminance part due to disturbances such as oxygen blowing. Is to be detected.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail by taking molten steel discharged from a ladle during the production of steel as molten metal as an example, but the slag outflow detection method of the present invention is not limited to molten steel.

FIG. 4 is a block diagram exemplifying an apparatus applied to the slag outflow detecting method of the present invention, wherein a discharge flow 2 of molten steel discharged from a ladle 1 is always observed by a CCD camera 3, and an observation area 4 is provided. A histogram indicating the frequency of the luminance levels 0 to 255 is created by the arithmetic processing device 5 having a built-in histogram counter, and the histogram is smoothed by the smoothing process. In the smoothing process, for example, an average frequency in a luminance range of −2 to +2 of the luminance level X of interest is obtained, and the average frequency is replaced with the frequency of the luminance level X. In this way, the luminance distribution diagrams illustrated in FIGS. 2 and 3 are created. FIG. 2 is a luminance distribution diagram of the molten steel discharge flow in a state where there is a disturbance, and FIG. 3 is a luminance distribution diagram when the slag flows out. Based on this luminance distribution map, the arithmetic processing unit 5
The slag flowing into the molten steel is detected in accordance with the following procedure by the arithmetic function programmed in the RAM and ROM.

FIG. 1 is a flowchart showing a processing procedure of the slag outflow detecting method of the present invention. First, a threshold value for dividing the luminance distribution of the background and the luminance distribution of the molten steel from the luminance distribution diagrams shown in FIGS. 2 and 3 is obtained by a discriminant analysis method. Assuming that the luminance level i is in the range of 0 to 200, the frequency of the luminance level i is n _i , and the total frequency is N, the probability variable P _i of the luminance level is expressed by equation (1), and P _i = n _i / N (1) The total average level μ _T of the image is represented by the following equation (1).

[0017]

(Equation 1)

The 0th-order average value ω (i) and the 1st-order average value μ (i) in the luminance distribution up to the luminance level i are as follows:
Can be expressed by the following equations (2) and (3), respectively: ω (i) = ω (i−1) + P _i (2) μ (i) = μ (i−1) + i * P _i ( 3) If the image is divided into two classes according to the luminance level, the variance between the classes is expressed by equation (4). sigma _B ² = _{[μ T * ω (i) -μ} (i) ] ² / [ω (i) * [1- ω (i)] ] ... (4)

Therefore, the optimum threshold value, that is, the threshold value, can be obtained from the following equation (6). i ^* = Note _{^{σ B 2 (i *) =}} max σ B 2 (i) ... (5), the luminance level i was in the range of 0 to 200, in addition to high-intensity part of the luminance levels 201 to 255 If the calculation range is set, an error occurs due to an abnormally high temperature portion of the molten steel, for example, an abnormally high temperature portion caused by oxygen injection, that is, an abnormally high luminance portion.

Next, the luminance distribution of the molten steel, that is, the threshold for dividing the luminance distribution of the molten steel and the luminance distribution of the slag, is calculated by the following procedure. 1. The luminance level having the highest frequency in the range of the threshold value to 200 is set as the provisional average value, and the luminance level is set in the range of the threshold value to the threshold value + (provisional average value−threshold value) × 2. Calculate the average value of the molten steel frequency. 2. Assuming that the luminance distribution of molten steel is a normal distribution, the luminance level is between threshold and threshold + (tentative average-threshold).
The standard deviation (σ) of the luminance distribution of the molten steel is calculated in the range of × 2. 3. To find the luminance distribution range of the molten steel, the average value + standard deviation x 2 (2σ) or the average value + standard deviation x 3 (3
σ) is calculated and used as a threshold value. Next, the luminance level is calculated as [threshold value + (threshold value-threshold value) x 1] or [threshold value + (threshold value-threshold value) x 2]. Threshold x
The threshold value for dividing the luminance value of [2-threshold] into an abnormally high luminance distribution due to blowing of oxygen or the like, that is, a luminance distribution of slag and an abnormally high luminance distribution due to disturbance is set. If the threshold value is larger than the luminance level 250, the threshold value is set to 250.

When detecting slag, an average value of the threshold values, for example, an average value of ten times is obtained, and the threshold values are determined as threshold values', ',', respectively. The brightness range of the threshold value '
The slag is detected by defining the luminance range of the threshold value 'to the threshold value' as the luminance distribution of the slag, and the luminance range of the threshold value 'to the luminance level 255 as the luminance distribution of the abnormally high luminance portion.

Based on the calculated and set threshold value ', threshold value', and threshold value ', slag flowing out into the molten steel is detected by the following procedure. (1) From the brightness distribution diagram of molten steel, the brightness level
し き い 値 (threshold value −1) in the luminance range, threshold value ′ to (threshold value −1) in the luminance range B,
And the total frequency C in the luminance range of the threshold value '-255. (2) When C is 0, it is determined that there is no abnormally high temperature part due to oxygen blowing or the like, that is, there is no abnormally high luminance part, and B / A
It is determined that the slag has been detected when the calculated value of is, for example, one or more calculated by two consecutive measurements. That is,
The time when the value of B / A becomes 1 or more is defined as the time when the outflow of slag into molten steel starts. (3) When C is 1 or more, it is determined that there is an abnormally high temperature portion due to disturbance such as oxygen blowing, that is, an abnormally high luminance portion, and the calculated value of B / A is, for example, 2 calculated by two consecutive measurements. In the above case, it is determined that the slag has been detected.
That is, the point in time when the value of B / A becomes 2 or more is determined to be the point in time when the outflow of slag into molten steel has started. The reason for using the value calculated by the two consecutive measurements is to prevent erroneous determination. In calculating the threshold value, when C is 1 or more and when B / A is 0.2 or more, the threshold value is not calculated.

The above-mentioned arithmetic processing is processed in real time by the arithmetic processing unit 5 to immediately determine whether or not slag has flowed out. When slag is detected, the alarm device 6 shown in FIG. It is possible to prevent slag from being mixed.

As described above, according to the slag outflow detection method of the present invention, the discharge flow of molten metal such as molten steel is observed by a CCD camera, and a luminance level and frequency histogram are created using the luminance signals of all the observation areas. The thresholds', 'and' are automatically set from the histogram according to a predetermined arithmetic program, and divided into a background luminance distribution, a molten metal luminance distribution, a slag luminance distribution and an abnormally high temperature part luminance distribution. Calculates the total frequency within each luminance distribution range, and detects the mixing of slag from the change in the total frequency ratio of molten metal and slag, so the threshold value can be automatically set appropriately. , And fully automatic detection is also possible.

Furthermore, since the observation area is designated as a plane, even if the outlet of the molten metal fluctuates up and down, it does not fall out of the object to be measured, and there is no need to adjust the position manually. In addition, when an abnormally high luminance portion occurs in the molten metal, for example, when the temperature of the molten steel decreases, a method of directly blowing oxygen to the molten steel to increase the temperature is employed. Even in the case of a sharp rise, slag can be detected without erroneous determination.

Since the creation of the luminance distribution diagram, the setting of the threshold value, and the calculation of the luminance distribution range are automatically obtained in this manner, it is possible to cope with the difference in the luminance level depending on the type of the molten metal. . The luminance signal from the CCD camera is visualized on a TV monitor, and the calculation is processed by a computer, so that the inflow slag can be detected accurately and quickly.

[0027]

As described above, according to the slag outflow detecting method of the present invention, it is possible to accurately detect the outflow point of the slag mixed in the molten metal discharge flow such as the molten steel discharge flow from the ladle. Therefore, it is possible to effectively prevent quality deterioration due to slag mixing. If the temperature of the molten steel decreases, measures such as blowing oxygen directly onto the molten steel to increase the temperature are taken. The mixed slag can be accurately detected without determination.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a processing procedure of a slag outflow detection method of the present invention.

FIG. 2 is a luminance distribution diagram of a molten steel discharge flow without slag outflow.

FIG. 3 is a luminance distribution diagram when only slag flows out.

FIG. 4 is a block diagram illustrating an apparatus applied to the slag outflow detection method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 ladle 2 molten steel discharge flow 3 CCD camera 4 observation area 5 arithmetic processing unit 6 alarm device

Claims (1)

[Claims] 1. A brightness of a discharge signal of a molten metal is measured by a CCD camera to create a histogram of a brightness signal, and the histogram is smoothed and replaced with a frequency of a brightness level.
A threshold value for dividing the luminance level of the background and the molten metal by the discriminant analysis method, a luminance value on the high luminance side corresponding to 2σ or 3σ as a normal distribution based on the luminance distribution of the molten metal from the luminance of the molten metal, and [ (Threshold value × 2−threshold value) is set as the threshold value,
The total frequency of the luminance distribution of the threshold is the total frequency of the molten metal, the total frequency of the threshold to the luminance distribution of the threshold is the total frequency of the slag, and the luminance distribution of the threshold to the highest luminance level is abnormally high due to disturbance. Calculate as the total frequency of the luminance portion, and detect the slag mixed into the discharge flow of the molten metal from the total frequency of the abnormally high luminance portion, the change in the total frequency ratio between the molten metal and the slag, and the presence or absence of the abnormally high luminance portion. A slag outflow detection method characterized by the above-mentioned.