Method for detecting metal outflow, system for detecting metal outflow, and refining method

Abstract

In a method for determining metal leakage during slag discharge, the invention enables the long-term use of equipment used for determining metal leakage, and also enables the determination of metal leakage even when metal is not present on the surface of the slag flow or when temperature variations occur. [Solution] The method for determining whether the ingot has leaked out involves analyzing images of the slag flow leaking out of the refining container to obtain an estimated value of the slag volume, directly weighing the slag that has leaked out of the refining container to obtain a measured value of the slag volume, and determining whether the ingot has leaked out of the refining container based on the estimated value and the measured value.

Description

[Technical Field]

[0001] This disclosure relates to a method for determining metal outflow, a system for determining metal outflow, and a refining method. [Background technology]

[0002] The converter refining process is a crucial process for reducing impurities such as silicon, phosphorus, and carbon in molten iron extracted from the blast furnace. In particular, phosphorus is known to significantly affect the crack susceptibility of steel by segregating at grain boundaries, leading to a substantial decrease in the mechanical properties of steel, including reduced low-temperature toughness and the development of abnormal structures in the central segregation area during continuous casting. Therefore, it is essential to stably reduce the phosphorus concentration in steel as much as possible. Some of these impurities are oxidized and removed into slag, whose basicity is adjusted by the addition of quicklime, by blowing high-pressure oxygen gas onto the molten iron. For example, phosphorus is oxidized to P2O5 and contained in the slag. However, if the temperature inside the refining vessel rises, such as during decarburization refining, the P2O5 is reduced and returns to the molten iron, resulting in rephosphorus. While it is possible to suppress rephosphorus by using large amounts of auxiliary materials such as quicklime, this increases the cost of auxiliary materials and consequently the amount of slag generated. Therefore, in typical molten iron pretreatment processes, the dephosphorization and decarburization processes are separated, and the slag generated between each process is separated from the molten iron to prevent impurity elements from returning to the molten iron.

[0003] Here, there are two methods for separating slag from molten iron: one is to tap only the molten iron into a separate container through the tapping hole and then discharge the entire amount of slag; the other is to tilt the refining vessel while keeping the molten iron in it and discharge the slag from the furnace opening. The former method provides good separation of molten iron and slag, but it requires transferring the molten iron to a separate container first, resulting in significant heat loss and reduced productivity. The latter method discharges the slag while keeping the molten iron in the refining vessel, resulting in less heat loss and better productivity. However, when slag is discharged from the furnace opening, molten iron may also be discharged at the same time, which leads to a decrease in iron yield. Therefore, it is necessary to suppress this as much as possible, and to stop the discharge of slag immediately when molten iron is discharged.

[0004] The following Patent Documents 1 to 3 describe methods for determining whether or not molten iron is leaking out during slag discharge.

[0005] Patent Document 1 discloses a method for detecting when molten iron has reached the metal outflow position by measuring the induced electromotive force, in which multiple coils are installed inside the furnace wall of a refining vessel.

[0006] Patent Document 2 discloses a method for determining the ratio of slag to molten iron in the slag flow by photographing the slag flow with an infrared camera and a visible light camera and referring to the brightness of each image.

[0007] Patent Document 3 discloses a method for determining the outflow of molten iron by photographing the slag flow using only a visible light camera and analyzing the brightness histogram of the obtained image. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2018-178209 [Patent Document 2] Japanese Patent Publication No. 2017-150034 [Patent Document 3] Japanese Patent Publication No. 2021-31688 [Overview of the project] [Problems that the invention aims to solve]

[0009] Incidentally, Patent Document 1 states that if the coil embedded in the furnace wall becomes exposed due to wear and tear of the refractory material in the furnace wall, it becomes difficult to use, posing challenges for long-term use and stability.

[0010] Patent documents 2 and 3 have problems such as difficulty in detecting molten iron when it is not present on the surface of the slag flow. In addition, although the brightness of the slag flow is analyzed by imaging, this brightness changes depending on the temperature, so there are problems that it is affected by variations in operation and temperature changes over time.

[0011] Therefore, the present disclosure aims to provide a method for determining metal outflow during slag discharge that enables long-term use of the equipment used for determining metal outflow, and that enables the determination of metal outflow even when there is no metal on the surface of the slag flow or when temperature variations occur. [Means for solving the problem]

[0012] The first aspect of the present disclosure provides a method for determining whether ingots have leaked out of the refining container, which involves analyzing images of the slag flow leaking out of the refining container to obtain an estimated value of the slag volume, directly weighing the slag that has leaked out of the refining container to obtain a measured value of the slag volume, and determining whether ingots have leaked out of the refining container based on the estimated value and the measured value.

[0013] The second aspect of the present disclosure's method for determining ingot leakage is the method for determining ingot leakage in the first aspect, wherein if the difference between the estimated value and the weighed value exceeds a predetermined threshold, it is determined that ingot has leaked out of the refining container.

[0014] A third aspect of the present disclosure is a method for determining ingot outflow, in which, in the method for determining ingot outflow in the second aspect, the standard deviation of the difference between the estimated value and the weighed value from the start of slag removal is used as the threshold.

[0015] The method for determining the outflow of molten metal according to the fourth aspect of the present disclosure is the method for determining the outflow of molten metal according to any one of the first to third aspects, and determines the outflow of molten metal from the refining vessel on the condition that the slag discharge progress exceeds 50%. Here, the "slag discharge progress" is obtained by expressing, as a percentage, the elapsed time with respect to the standard time required for slag discharge in normal operation in advance. The standard time required for slag discharge is the average time from the point when the refining vessel is tilted and slag discharge starts to the point when the tilting of the refining vessel starts to be returned to end the slag discharge.

[0016] The method for determining the outflow of molten metal according to the fifth aspect of the present disclosure is the method for determining the outflow of molten metal according to any one of the first to third aspects, and determines the outflow of molten metal from the refining vessel on the condition that the slag discharge progress exceeds 80%.

[0017] The molten metal outflow determination system according to the sixth aspect of the present disclosure includes a photographing device that photographs the slag discharge flow flowing out from the refining vessel, a weighing device that directly weighs the slag discharged from the refining vessel, analyzes the photographed image to obtain an estimated value of the slag discharge amount, and based on the estimated value and the weighed value weighed by the weighing device, executes a process for determining the outflow of molten metal from the refining vessel, and a control device.

[0018] The molten metal outflow determination system according to the seventh aspect of the present disclosure is the molten metal outflow determination system according to the sixth aspect, and includes a notification device. When the control device determines that molten metal has flowed out from the refining vessel, it uses the notification device to notify the outside of the outflow of molten metal.

[0019] The refining method according to the eighth aspect of the present disclosure uses the method for determining the outflow of molten metal according to any one of the first to fifth aspects to determine the outflow of molten metal from the refining vessel. When molten metal is flowing out, the outflow amount of molten metal is obtained based on the difference between the estimated value of the slag discharge amount and the weighed value of the slag discharge amount. Based on the outflow amount, the amount and composition of the slag in the refining vessel are determined, and at least one of the input amount of the auxiliary raw material and the acid feeding amount is adjusted.

Advantages of the Invention

[0020] According to this disclosure, the method for determining metal outflow during slag discharge enables the long-term use of the equipment used for determining metal outflow, and also allows for the determination of metal outflow even when there is no metal on the surface of the slag flow or when temperature variations occur. [Brief explanation of the drawing]

[0021] [Figure 1] This is a longitudinal cross-sectional view of a refining vessel used in a metal outflow determination system according to one embodiment of the present disclosure, showing a state in which slag flow is flowing out from a tilted refining vessel. [Figure 2] This is a diagram showing the configuration of the control device. [Figure 3] This is a diagram showing the debris flow. [Figure 4] This figure shows (a) the relationship between the direct weighing and the estimated amount obtained by image analysis, and (b) the difference between the direct weighing and the estimated amount obtained by image analysis, and the change in its standard deviation over time, when no metal outflow is determined using the comparative example's metal outflow determination method. [Figure 5] When a metal outflow determination is made using the metal outflow determination method of one embodiment of this disclosure, the following are the relationship between the direct weighing and the estimated amount obtained by image analysis, and the change over time of the difference between the direct weighing and the estimated amount obtained by image analysis, and its standard deviation. [Modes for carrying out the invention]

[0022] Hereinafter, embodiments for carrying out the technology of this disclosure will be described with reference to the drawings. Components indicated by the same reference numerals in each drawing are the same or similar components. In the embodiments described below, descriptions and reference numerals that are repeated may be omitted. Furthermore, the drawings used in the following description are all schematic, and the dimensional relationships and ratios of each element shown in the drawings do not necessarily correspond to reality. Also, the dimensional relationships and ratios of each element do not necessarily correspond between multiple drawings.

[0023] First, the converter 20 used in the metal outflow determination method of this embodiment will be described. Note that the converter 20 is an example of a refining vessel in this disclosure.

[0024] As shown in Figure 1, the converter 20 comprises a bottom 20A, a furnace wall 20B, a furnace opening 20C, and a steel tap hole 20D provided in the furnace wall 20B. The converter 20 is also configured to tilt by a tilting mechanism 24 (see Figure 2). When the converter 20 is tilted, the slag flow SF flows out from the furnace opening 20C. The discharged slag flow SF is received by the slag pan 22.

[0025] Next, the metal outflow determination system using the converter 20 of this embodiment (hereinafter referred to as the "determination system" as appropriate) will be described. The determination system of this embodiment is a system that, during intermediate slag discharge, determines an estimated value M of the slag amount (slag mass) by image analysis, determines the weighed value W of the slag amount by direct weighing, and determines the outflow of metal from the converter 20 based on the estimated value M and the weighed value W. This determination system comprises an imaging device 40, a weighing device 41, and a computer 42 as an example of a control device. In addition, in this embodiment, the determination system is equipped with a notification device 60 as an example.

[0026] The imaging device 40 is a device that has the function of imaging the slag flow SF flowing out of the converter 20. Specifically, as shown in Figure 1, the imaging device 40 is positioned in front of the converter 20 and images the slag flow SF flowing out (flowing down) from the furnace opening 20C of the converter 20, which has tilted during intermediate slag discharge, toward the slag pot 22. Here, positioning the imaging device 40 in front of the converter 20 means that, in a plan view (viewed from above), the imaging device 40 is positioned on the opposite side of the converter 20 from the slag pot 22. It is preferable to position the imaging device 40 such that the optical axis OA is a straight line passing through the center of the converter 20 in a plan view. Note that the arrow UP shown in Figures 1 and 3 points upward. In this embodiment, one imaging device 40 is positioned in front of the converter 20.

[0027] Furthermore, it is preferable that the imaging device 40 be positioned at a height that is less susceptible to the effects of the sedation flame. The term "sedation flame" here refers to the flame generated by the reaction between the slag in the waste disposal pot 22 and the slag sedation material.

[0028] For example, a CCD camera or a CMOS camera may be used as the imaging device 40.

[0029] The imaging device 40 is connected to the computer 42 by wire or wireless connection. Image information captured by the imaging device 40 is transmitted to the computer 42. The image information transmitted from the imaging device 40 may be still image information captured at predetermined time intervals (for example, every second) or video image information.

[0030] The imaging device 40 may also be equipped with a limiting filter (for example, a neutral density filter) or a bandpass filter to limit the amount of incident light so that the brightness of the slag flow SF, which is a high-luminance substance, does not saturate in the captured image.

[0031] The weighing device 41 is a device that has the function of directly weighing the slag flow SF that has flowed out from the converter 20. Specifically, the weighing device 41 is a device that measures the mass of the slag received in the slag pan 22. In this embodiment, as an example, it is installed on the slag trolley 23 on which the slag pan 22 is placed.

[0032] For the weighing device 41, for example, a load cell or various types of scales may be used.

[0033] The weighing device 41 is connected to the computer 42 by wired or wireless connection. The weighed value W measured by the weighing device 41 is transmitted to the computer 42.

[0034] Computer 42 is a device that has the function of determining an estimated value M of the slag volume based on the image captured by the imaging device 40, and the function of determining the outflow of metal from the converter 20 based on the estimated value M and the weighed value W. Specifically, computer 42 analyzes the image captured by the imaging device 40 to determine an estimated value M of the slag volume, and executes a process to determine the outflow of metal from the converter 20 based on the estimated value M and the weighed value W measured by the weighing device 41.

[0035] Furthermore, one method for obtaining an estimated value M of the amount of debris discharged by analyzing the image of the debris discharge flow SF captured by the imaging device 40 using the computer 42 is to estimate the amount of debris discharged by determining the width L of the debris discharge flow SF from the image of the debris discharge flow SF. As such a method for estimating the amount of debris discharged, for example, the method for estimating the amount of debris discharged described in PCT / JP2023 / 028351 may be used, or other estimation methods may be used. In this embodiment, as an example, the amount of debris discharged is estimated from the image of the debris discharge flow SF using the estimation method described in PCT / JP2023 / 028351.

[0036] Furthermore, as shown in Figure 2, the computer 42 includes a CPU (Central Processing Unit) 43, a main memory 44 that provides temporary storage, an auxiliary storage device 45 that provides non-volatile storage, and an input / output interface (I / F) 46. The CPU 43, main memory 44, auxiliary storage device 45, and input / output I / F 46 are connected to each other via a bus 47.

[0037] The auxiliary storage device 45 can be implemented using a Hard Disk Drive (HDD), Solid State Drive (SSD), flash memory, etc. The auxiliary storage device 45 stores a determination program 48 that causes the computer 42 to function as a metal outflow determination device in the converter 20. The CPU 43 reads the determination program 48 from the auxiliary storage device 45, loads it into the main memory 44, and executes the processes described in the determination program 48 sequentially, thereby functioning as a metal outflow determination device in the converter 20.

[0038] The input / output interface 46 is connected to the imaging device 40 and the weighing device 41 via wired or wireless connections. This configuration allows image information captured by the imaging device 40 to be stored in the auxiliary storage device 45 via the input / output interface 46 and analyzed by the CPU 43. In this embodiment, as an example, the input / output interface 46 is also connected to the notification device 60 via wired or wireless connections.

[0039] As shown in Figure 2, the computer 42 receives sequential image information of the slag flow SF captured by the camera 40. The computer 42 analyzes the received image information to determine the width L of the slag flow SF. Here, if the image information transmitted from the camera 40 is still images, the computer 42 analyzes each still image. On the other hand, if the image information transmitted from the camera 40 is video, the computer 42 extracts still images from the video at predetermined time intervals (for example, every second) and analyzes each extracted still image. In order to improve the accuracy of estimating the slag flow SF, the computer 42 may, for example, have the camera 40 capture 10 or more still images per second and analyze each captured still image, or it may extract 10 or more still images per second from the video captured by the camera 40 and analyze each extracted still image.

[0040] In the still image analysis performed by computer 42, the still image is first binarized. Then, the length of the high-luminance portion of the slag flow SF within the pre-defined analysis area is measured as the apparent length. As shown in Figure 3, the length of the high-luminance portion of the slag flow SF corresponds to the width L of the slag flow SF.

[0041] The computer 42 also calculates the flow velocity V (m / s) from the captured images. The flow velocity V (m / s) of the debris flow SF at the measurement position with width L (the position shown by the dashed line in Figure 3) is calculated by assuming the debris flow SF is in free fall (2gH). 0.5Alternatively, the moving distance of the slag discharge flow SF may be obtained by pattern matching from at least two or more images, and the moving distance of the slag discharge flow SF may be obtained by dividing the moving distance by the difference (s) in the shooting times of the images for which the moving distance has been obtained. When assuming the free fall of the slag discharge flow SF for the flow velocity V (m / s), the computer 42 obtains, by image analysis from the captured still image, the distance H (m) from the measurement position of the width L to the start position of the outflow of the slag discharge flow SF from the furnace mouth 20C. Regarding the outflow position from the furnace mouth 20C, since the converter 20 rotates about its axis, the furnace mouth 20C (the slag discharge outflow position) can be geometrically obtained from the tilting angle.

[0042] Further, the computer 42 obtains the slag discharge amount (or rather, the estimated value of the slag discharge amount) M by the following formula (I). The following formula (I) is a calculation formula used in the slag discharge amount estimation method described in PCT / JP2023 / 028351. This formula (I) is a calculation formula when the slag discharge flow SF does not branch. When the slag discharge flow SF branches, the calculation formula for the case where the slag discharge flow SF branches, which is used in the slag discharge amount estimation method described in PCT / JP2023 / 028351, may be used.

[0043]

Equation

[0044] The bulk density ρ of the slag is the effective furnace volume V of the converter 20 at the time when the slag starts to flow out from the furnace mouth 20C of the tilted converter 20 DS , the volume of molten iron is V M , the volume of slag is V S As, the volume V of slag S is V S = V DS - V MThe mass of the slag is calculated as M. S Therefore, bulk density ρ = M S / V S You can also calculate it this way. Note V S +V M This can also be determined from the drawing of the converter 20 using CAD or geometric calculations, once the tilt angle of the converter 20 is determined. Also, V M Since the mass of molten steel is approximately equal to the mass of the main raw materials (molten iron + scrap), it can also be calculated by multiplying the density of molten steel by the mass of the main raw materials (actual results). The shape of the converter 20 is the internal shape of the furnace. The internal shape of the furnace includes the inner surface shape of the furnace wall 20B and the inner surface shape of the bottom 20A.

[0045] Furthermore, the bulk density ρ of the slag is calculated by determining the gas phase fraction φ using the formula φ = (h0-h) / h0 × 100, where h0 is the slag height (m) in the refining vessel at the start of refining, h is the slag height (m) when measuring the width L of the slag discharge flow, and φ is the gas phase fraction in the slag. Then, the density of the uniform liquid phase slag is calculated as ρ. L (kg / m 3 ) and bulk density ρ = ρ L It can also be calculated as ×(100-φ) / 100.

[0046] Furthermore, parameter α is a correction coefficient for the cross-sectional shape of the slag flow SF, and if the cross-sectional shape of the slag flow SF is a perfect circle, α becomes 1 / 4.

[0047] The computer 42 then determines whether metal has leaked out of the converter 20 based on the estimated value M obtained and the weighed value W transmitted from the weighing device 41. Specifically, it determines that metal has leaked out of the converter 20 when the difference between the estimated value M and the weighed value W exceeds a preset threshold T. In this embodiment, as an example, the standard deviation of the difference between the estimated value M and the weighed value W from the start of slag discharge in the converter 20 is used as the threshold T. However, this disclosure is not limited to this configuration, and the ratio of the estimated value M and the weighed value W from the start of slag discharge in the converter 20 may be used as the threshold T. Furthermore, the threshold T may be determined experimentally or empirically, or it may be determined as a theoretical measurement error that can be considered in relation to the equipment configuration. Furthermore, the maximum value of the difference between the estimated value M and the weighed value W may be used as the threshold T, or the absolute average value of the difference between the estimated value M and the weighed value W may be used.

[0048] Furthermore, the computer 42 may determine that metal has flowed out of the converter 20 when the slag removal progress exceeds 50%. In addition, the computer 42 may determine that metal has flowed out of the converter 20 when the slag removal progress exceeds 80%. The term "slag removal progress" here refers to the elapsed time as a percentage of the standard time required for slag removal in normal operation. The standard time required for slag removal is the average time from the point when the converter 20, as a refining vessel, is tilted and slag removal begins, to the point when the tilt of the converter 20 is reversed to end the slag removal.

[0049] In this embodiment, the computer 42, when it determines that metal has leaked out of the converter 20, uses the notification device 60 to notify the outside of the metal leak. This notification device 60 is, for example, a device that emits sound, light, vibration, or a combination thereof, and its operation is controlled by the computer 42. When the computer 42 determines that metal has leaked out of the converter 20, the notification device 60 emits, for example, sound, light, or vibration to notify the outside of the metal leak.

[0050] Next, a method for determining metal outflow using the converter 20 of this embodiment will be described. The metal outflow determination method of this embodiment is a method in which, during intermediate slag discharge, an estimated value M of the amount of slag discharged (mass of slag discharged) is obtained by image analysis, the weighed value W of the amount of slag discharged is obtained by direct weighing, and the outflow of metal from the converter 20 is determined based on the estimated value M and the weighed value W.

[0051] First, the slag flow SF flowing out from the furnace opening 20C of the converter 20 is photographed. Specifically, as shown in Figure 1, the slag flow SF flowing out (downward) from the furnace opening 20C of the converter 20, which has tilted during intermediate slag discharge, toward the slag pot 22 is photographed by the photography device 40.

[0052] Next, the width of the slag flow SF is determined from the image captured by the imaging device 40. Specifically, the image information of the slag flow SF captured by the imaging device 40 is received by the computer 42, and the computer 42 performs image analysis to determine the width L of the slag flow SF.

[0053] Next, the flow velocity V (m / s) is determined from the captured images. Specifically, the computer 42 calculates the flow velocity V (m / s) of the debris flow SF at the measurement position of the width of the debris flow SF by assuming free fall of the debris flow SF (2gH) 0.5 Alternatively, the distance traveled by the slag flow SF can be determined by pattern matching from at least two images, and the flow velocity V (m / s) can be determined by dividing the distance traveled by the slag flow SF by the difference (s) in the timestamps of the images used to determine the distance traveled.

[0054] Next, we use equation (1) above to estimate the amount of waste M.

[0055] Furthermore, the mass of the slag that flows out from the furnace opening 20C of the tilted converter 20 into the slag pot 22 is directly weighed using a weighing device 41. This allows the weighed value W to be determined.

[0056] Next, the outflow of metal from the converter 20 is determined based on the estimated value M and the weighed value W. Specifically, if the difference between the estimated value M and the weighed value W exceeds a predetermined threshold T, it is determined that metal has flowed out of the converter 20.

[0057] Alternatively, the outflow of metal from the converter 20 may be determined when the slag removal progress exceeds 50%, or the outflow of metal from the refining vessel may be determined when the slag removal progress exceeds 80%.

[0058] In this embodiment, when it is determined that metal has leaked out of the converter 20, the notification device 60 notifies the outside that metal has leaked out. When the notification device 6 notifies the outside that metal has leaked out, for example, the operator of the converter 20 stops the discharge of slag from the converter 20.

[0059] Furthermore, if metal is leaking out, the amount of metal leaking out can be determined based on the difference between the estimated value M and the weighed value W. Based on the determined amount of leaking metal, the amount and composition of slag in the converter 20 can be determined (recalculated), and at least one of the input amount of auxiliary materials and the amount of acid supplied can be adjusted. In this way, it becomes possible to produce metal of stable quality.

[0060] Next, the effects and advantages of this embodiment will be described. The Disclosers discovered that metal outflow associated with slag discharge often occurs when the tilt of the converter 20, which serves as the refining vessel, is increased towards the end of the slag discharge process. Therefore, they considered that the accuracy of metal outflow determination for the slag flow SF could be improved by excluding periods when metal outflow is minimal. Furthermore, if the density of the slag is set as the slag density during slag discharge, then in the case of estimating the amount of slag by image analysis, the estimated mass of the slag remains constant regardless of whether metal outflow occurs, provided that the volume of the slag flow is the same. On the other hand, when weighing the slag directly, the weighed value changes accordingly when metal, which has a higher density than slag, flows out. By utilizing this, the Disclosers considered that it would be possible to determine that metal outflow has occurred when the difference between the weighed value W obtained by direct weighing and the estimated value M obtained by image analysis exceeds a predetermined threshold T. Furthermore, for the estimated value M obtained by image analysis of the slag and the weighed value W obtained by direct weighing, information on the temperature and brightness of the slag flow is unnecessary. Therefore, the disclosers believe that even if there are variations in operation or temperature changes over time, it will not affect the accuracy of the metal outflow determination in this disclosure. Taking these factors into consideration, in one embodiment of this disclosure, the outflow of metal from the converter 20 is determined based on the estimated amount M of slag obtained by analyzing images of the slag flow SF and the weighed value W obtained by directly weighing the slag. Compared to a configuration in which the equipment used for metal outflow determination is installed in the converter, this allows for long-term use of the equipment used and enables metal outflow determination even when there is no metal on the surface of the slag flow SF or when there are temperature variations.

[0061] Furthermore, in this embodiment, since it is determined that metal has leaked out of the converter 20 when the difference between the estimated value M and the weighed value W exceeds a preset threshold T, the accuracy of determining metal leakage is improved compared to, for example, a system that determines metal leakage when the estimated value M or the weighed value W exceeds a set threshold.

[0062] Furthermore, in this embodiment, since the standard deviation of the difference between the estimated value M and the weighed value W from the start of slag removal is used as the threshold T, accurate metal outflow detection can be performed even if there is a large variation in the difference between the estimated value M and the weighed value W.

[0063] Furthermore, in this embodiment, the outflow of metal from the converter 20 is determined based on the condition that the slag removal progress exceeds 50%, thereby improving the accuracy of metal outflow determination. In particular, the accuracy of metal outflow determination is further improved by determining the outflow of metal from the converter 20 based on the condition that the slag removal progress exceeds 80%.

[0064] Furthermore, in this embodiment, if a metal outflow is detected, the notification device 60 notifies the outside, making it easier for, for example, the operator of the converter 20 to recognize the metal outflow. This makes it possible for the operator to keep the amount of metal outflow low.

[0065] (Other embodiments) In the embodiments described above, the converter 20 is an example of a refining vessel, but the disclosure is not limited to this configuration. The refining vessel may be, for example, an electric furnace, a molten steel ladle, or a torpedo car.

[0066] (Examples) To verify the effectiveness of the technology disclosed herein, a test was conducted on an actual converter, combining weighed values ​​of slag volume and estimated values ​​obtained through image analysis. The steel type was ordinary steel, and the molten iron volume was 250 tons to 350 tons when converter-type molten iron pretreatment was performed. The amount of slag discharged was measured both by direct weighing using a load cell and by estimation using image analysis. The slag discharge progress was determined in advance from the slag discharge time under normal operation. In this embodiment, the threshold used to determine metal outflow during slag discharge was the standard deviation of the difference between the direct weighing and the estimated amount obtained by image analysis from the start of slag discharge. Metal outflow was determined when the difference between the direct weighing and the estimated amount obtained by image analysis exceeded the above threshold at the end of slag discharge when the slag discharge progress exceeded 80%.

[0067] Figure 4 shows the results when no metal outflow occurred. (a) shows the measurement results of the direct weighing value and the estimated value from image analysis relative to the slag removal progress, and (b) shows the difference between the direct weighing value and the estimated value from image analysis relative to the slag removal progress, and the standard deviation of the difference between the direct weighing value and the estimated value from image analysis since the start of slag removal. In Figure 4(a), it can be seen that the direct weighing value and the estimated value from image analysis are in good agreement. Furthermore, in Figure 4(b), the difference between the direct weighing value and the estimated value from image analysis at the end of slag removal, when the slag removal progress exceeds 80%, remained smaller than the standard deviation of the difference between the direct weighing value and the estimated value from image analysis since the start of slag removal. From this, it was determined that there was no metal outflow in the charge in question in this invention, and no metal outflow was actually observed.

[0068] Figure 5 shows the results when metal is released. (a) shows the measurement results of direct weighing values ​​and estimated values ​​from image analysis relative to the slag removal progress, and (b) shows the difference between the direct weighing values ​​and estimated values ​​from image analysis relative to the slag removal progress, and the standard deviation of the difference between direct weighing and estimated values ​​from image analysis since the start of slag removal. In Figure 5(a), the direct weighing value is larger than the estimated value from image analysis at the end of slag removal. This is because metal, which has a higher density than slag, was released. Also, in Figure 5(b), at the end of slag removal, when the slag removal progress exceeds 80%, the difference between direct weighing and estimated values ​​from image analysis became larger than the standard deviation of the difference between direct weighing and estimated values ​​from image analysis since the start of slag removal. Specifically, at a slag removal progress of 91%, the difference between direct weighing and estimated values ​​from image analysis exceeded the standard deviation of the difference between direct weighing and estimated values ​​from image analysis since the start of slag removal. Based on this, it was determined in this disclosure that the charge in question involved an outflow of bullion, and indeed, an outflow of bullion was observed.

[0069] In determining metal outflow, a threshold value of N times the standard deviation of the difference between the direct weighing from the start of slag discharge and the estimated amount obtained by image analysis (where N is a positive real number) may be used. In this example, metal outflow was determined with N=1.0, but by setting N<1.0, for example, metal outflow can be determined at an earlier stage and slag discharge can be terminated, which is effective when it is desired to minimize the amount of metal outflow. On the other hand, by setting N>1.0 to determine metal outflow, a relatively large amount of slag can be discharged. Therefore, when melting low-phosphorus steel or very low-phosphorus steel, it may be more cost-effective to increase the amount of phosphorus discharged from the furnace to reduce the dephosphorization load during blowing after slag discharge, compared to the cost increase due to deterioration of iron yield. Thus, the value of N may be changed depending on the type of steel, target composition, and actual operating conditions.

[0070] Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above, and it is of course possible to implement it in various other forms without departing from its spirit. [Explanation of symbols]

[0071] 20 Converter (an example of a smelting vessel) 40 Imaging device 41 Weighing device 42. Computer (an example of a control device) SF tailings flow

Claims

1. By analyzing images of the slag flowing out of the refining vessel, we can estimate the amount of slag. The amount of waste slag discharged from the aforementioned refining vessel is directly weighed to determine the weighed value of the waste slag. Based on the estimated value and the weighed value, the outflow of metal from the refining container is determined. Method for determining whether bullion is leaking out.

2. The method for determining whether ingot has flowed out of the refining container according to claim 1, wherein it is determined that ingot has flowed out of the refining container when the difference between the estimated value and the weighed value exceeds a predetermined threshold.

3. The method for determining metal outflow according to claim 2, wherein the threshold is the standard deviation of the difference between the estimated value and the weighed value from the start of slag discharge.

4. A method for determining the outflow of ingots from the refining vessel according to claim 1, wherein the outflow of ingots from the refining vessel is determined on the condition that the progress of slag removal exceeds 50%.

5. A method for determining the outflow of ingots from the refining vessel according to claim 1, wherein the outflow of ingots from the refining vessel is determined on the condition that the progress of slag removal exceeds 80%.

6. A camera for photographing the slag flow out of the refining vessel, A weighing device for directly weighing the waste material discharged from the aforementioned refining vessel, A control device that analyzes captured images to obtain an estimated value of the amount of waste, and performs a process to determine the outflow of ingots from the refining container based on the estimated value and the weighed value measured by the weighing device, A bullion outflow detection system having the following features.

7. It has a notification device, The metal outflow determination system according to claim 6, wherein the control device determines that metal has flowed out of the refining vessel and uses the notification device to notify the outside of the metal outflow.

8. The outflow of metal from the refining vessel is determined using the metal outflow determination method described in any one of claims 1 to 5. When the bullion is leaking out, the amount of bullion leaking out is determined based on the difference between the estimated amount of slag and the weighed amount of slag. A refining method comprising determining the amount and composition of slag in the refining vessel based on the aforementioned outflow amount, and adjusting at least one of the amount of auxiliary raw materials added and the amount of acid supplied.

Images