Device for continuously monitoring thickness of continuous casting liquid covering slag layer and using method

Abstract

The invention discloses a device for continuously monitoring the thickness of a continuous casting liquid casting powder layer and a using method, and belongs to the technical field of continuous casting billet manufacturing in the steelmaking process, the device is characterized in that a probe 1 of the device is an inverted right triangle cavity object, and the inner wall of the bevel edge of a temperature sensing cavity 7 is a temperature sensing surface 8; the infrared temperature measuring instrument 2 directly irradiates on the temperature sensing surface 8, and the thickness of the covering slag layer can be continuously detected according to the positions of the temperature boundary of the molten slag and the liquid slag and the temperature boundary of the liquid slag and the molten steel on the temperature sensing surface 8 measured by the infrared temperature measuring instrument 2.

Description

Technical Field

[0002] The invention relates to the technical field of continuous casting billet manufacturing in a steelmaking process of the iron and steel metallurgical industry, and in particular to a device and a method for continuously monitoring the thickness of a slag layer of a continuous casting liquid protective slag. Background Art

[0003] At present, in the actual production of steelmaking and continuous casting, in order to prevent the secondary oxidation of molten steel, it is necessary to continuously add solid protective slag to the surface of the molten steel in the crystallizer. After it gradually melts into liquid protective slag, it can isolate the molten steel from the air. At the same time, the liquid protective slag can also play the following roles: (1) heat insulation and heat preservation, reducing the heat loss of molten steel; (2) absorbing inclusions and purifying molten steel; (3) forming a lubricating slag film between the ingot shell and the crystallizer to reduce friction resistance. It can be seen that the role of liquid protective slag is very prominent and indispensable.

[0004] After solid granular protective slag (hereinafter referred to as solid slag) is added to the crystallizer, it will continuously absorb the heat of molten steel, turn the granular solid slag into molten protective slag (hereinafter referred to as molten slag) and then into liquid protective slag (hereinafter referred to as liquid slag). The problem is that too much solid slag will cause the thickness of the liquid slag to increase, and casting slag will easily occur, thereby increasing the solid particle inclusions in the molten steel, resulting in a decrease in the quality qualification rate of the steel billet; but when the slag layer thickness of the liquid slag is less than a certain value, the liquid slag will form a solid slag ring around the inner wall of the crystallizer due to its rapid cooling by the crystallizer, blocking the channel between the steel body that has formed a crystal shell after cooling and the cooling wall of the crystallizer, so that the liquid protective slag cannot flow smoothly between the steel body crystal shell and the crystallizer, and the crystal shell and the surface of the crystallizer cannot form a uniform slag film, which leads to cracks on the surface of the corresponding slab. Therefore, it is very important to accurately measure the slag layer thickness of the continuous casting liquid slag so that it can be controlled within a certain thickness range.

[0005] At present, the method often used in the industry to measure the thickness of the slag layer of continuous casting liquid protective slag is the double-wire measurement method, that is, using two metal wires with different melting points, where the melting point of the first metal wire is lower than the melting point of molten steel, but higher than the melting point of liquid slag, and the melting point of the second metal wire is lower than the melting point of liquid slag. The two metal wires are inserted into the crystallizer at a certain depth at the same time. The first and second metal wires will be melted at the same time in the molten steel. In the liquid slag, the first metal wire will not be melted because its melting temperature is higher than the melting point of liquid slag, but the second metal wire will be melted by the liquid slag. After the liquid slag, the molten protective slag and solid slag will be intact due to the low temperature. In this way, as long as the two metal wires are quickly pulled out of the crystallizer and the residual length difference of the two metal wires inserted into the crystallizer is measured, the thickness of the slag layer of the liquid slag can be accurately measured. It can be seen that this measurement method is relatively reliable, but the disadvantages are that it is relatively cumbersome, requires plugging and unplugging once for each measurement, and the accuracy is not high. Secondly, it cannot be used for online dynamic continuous measurement. Therefore, it cannot meet the requirements of dynamic monitoring and real-time control. Summary of the invention

[0006] In order to solve the difficult problem that the existing liquid protective slag layer cannot realize continuous online measurement of the liquid slag layer thickness, this application invents a device and a method for monitoring the thickness of the continuous casting liquid protective slag layer by using temperature gradient changes, thereby realizing effective real-time measurement of the liquid protective slag layer thickness.

[0007] The measuring device invented is based on the principle that there are different temperature gradients from top to bottom in the continuous casting crystallizer from the solid slag to the molten steel interface, where the lowest temperature is the position where the solid slag is just added, which is close to the room temperature range, followed by the molten protective slag range temperature, the liquid slag range temperature and the molten steel temperature. If these temperature ranges can be directly measured vertically, the thickness of different slag materials or slag layers can be obtained. However, direct vertical measurement is almost impossible, so the inventor thought of using an object with a cavity, passing it from top to bottom through the solid slag, molten slag, liquid slag until it reaches the molten steel, and measuring the temperature gradient on the surface of the cavity object, which can also achieve the aforementioned invention purpose.

[0008] Based on the above invention concept, the present invention designs a device for continuously monitoring the thickness of the continuous casting liquid protective slag layer, and its structure is as shown in the attached figure. Figure 1 As shown in FIG. 1 , it is mainly composed of a probe 1, an infrared temperature measuring instrument 2, a fixing bracket 3, a protective cover 4, a protective gas pipeline 5, and a pipeline bracket 6, wherein: the probe 1 is as shown in the attached Figure 2As shown, it is an inverted right-angled triangular cavity object with a certain wall thickness L, an open upper end, and a sealed lower end. The cavity of the right-angled triangular cavity object is called a temperature sensing cavity 7; the probe 1 is made of a material with fast thermal conductivity and stable physical and chemical properties at high temperatures, such as refractory materials such as carbon, magnesium carbon, and aluminum carbon; the long right-angled side of the probe 1 is perpendicular to the surface of the molten steel in the continuous casting crystallizer, and the short right-angled side of the probe 1 is the open end of the temperature sensing cavity 7. The open end of the probe 1 is installed and fixed on the protective cover 4 in a quick replacement manner. The inner wall of the hypotenuse of the temperature sensing cavity 7 of the probe 1 is an inclined surface, which is called a temperature sensing surface 8 for sensing the steel The temperature of water, liquid slag, molten slag and solid slag, the long right-angle side of the temperature sensing cavity 7 in the probe 1 and the hypotenuse form an angle α; an infrared temperature measuring instrument 2 fixed to the side wall of the protective cover 4 by a fixing bracket 3 is provided directly above the probe 1, and the infrared temperature measuring instrument 2 directly irradiates the aforementioned temperature sensing surface 8, and the infrared temperature measuring instrument 2 is connected to the data processing display 11 through a transmission cable 10, and a transmission cable protection tube 5 is provided on the outside of the transmission cable 10, and the measuring instrument protection cover 4 is fixed on the transmission cable protection tube 5, and the transmission cable protection tube 5 is fixed to the crystallizer cover 9 through a pipe bracket 6; Attached Figure 3 This is an enlarged top view of the probe 1. When the probe 1 is inserted into the molten steel, Figure 3 The parallel lines in the figure represent the invisible temperature boundaries of different solid and molten bodies on the temperature sensing surface 8 of the temperature sensing cavity 7 of the probe 1, wherein the aa line is the upper surface temperature line of the solid slag on the temperature sensing surface 8 of the probe 1, the bb line is the temperature boundary line between the solid slag and the molten slag on the temperature sensing surface 8, the cc line is the temperature boundary line between the molten slag and the liquid slag on the temperature sensing surface 8, the dd line is the temperature boundary line between the liquid slag and the molten steel on the temperature sensing surface 8, and the ee line and the ff line are the bottom square edge lines in the temperature sensing cavity 7.

[0009] When steel production is relatively stable, molten steel and solid slag are also relatively stable, the liquid level of continuous casting molten steel is relatively fixed, and the temperature of molten steel, liquid slag, and molten slag are all stable values. Then, the invisible temperature dividing line on the temperature sensing surface 8 can be displayed on the data processing display 11 of the infrared temperature measuring instrument 2, so as to accurately determine the location of the aa, line, bb, line, cc, line, and dd, line, where the vertical interval distance Y between the cc and dd lines is the thickness of the liquid slag. When the angle α between the long right-angled side of the temperature sensing cavity 7 in the probe 1 and the hypotenuse is determined, the liquid slag layer thickness Y can be accurately determined by calculating the plane distance X between the cc and dd lines measured by the infrared temperature measuring instrument 2 using trigonometric functions.

[0010] Since the probe 1 of the device of the present invention can be inserted into the molten steel all the time during its effective life, the infrared temperature measuring instrument 2 can continuously measure the plane distance X between the cc, line and the dd, line on the temperature sensing surface 8, and calculate the slag layer thickness Y of the liquid slag in real time, thereby effectively realizing continuous monitoring of the slag layer thickness Y of the liquid slag, thereby effectively solving the problem of continuous measurement of the slag layer thickness of the liquid slag, thereby achieving the purpose of the present invention.

[0011] The present invention also discloses a method for using the aforementioned device. The specific steps are as follows:

[0012] The tip of the probe 1 of the device is directly inserted downward into the crystallizer 12, passing through the solid slag 13, the molten slag 14, the liquid slag 15 and reaching the molten steel 16; 2. Turn on the infrared temperature measuring instrument 2 and the data processing display 11, receive the infrared signal radiated by the temperature sensing surface 8 in the temperature sensing cavity 7 to measure the temperature, and determine the respective temperatures and positions of the temperature boundary line cc between the molten slag and the liquid slag and the temperature boundary line dd between the liquid slag and the molten steel on the temperature sensing surface 8; 3. When the temperature line on the temperature sensing surface 8 is relatively stable, compare the temperatures of the cc line and the dd line measured in step 1, measure the horizontal distance X between the two, and use trigonometric functions to calculate the thickness Y value of the liquid protective slag, Y=X / tgα.

[0013] According to the standard thickness range of liquid slag given by the big data model and compared with the real-time thickness Y of the liquid protective slag obtained in step 3, the amount of solid slag added is controlled to ensure that the slag layer thickness of the liquid protective slag is always within the standard thickness range.

[0014] The biggest advantage of this invention over the previous double-wire measurement method for measuring the thickness of liquid slag is that it can realize the real-time and continuous measurement process. According to the measurement results, the thickness of the liquid protective slag can be adjusted in real time by adding solid slag, which provides an important guarantee for the rapid production of high-quality continuous casting billets. The four major functions of continuous casting protective slag are maximized, among which the surface qualification rate of steel ingots reaches 99.00~99.80%, which is 1.5 percentage points higher than before, and the billet drawing speed is increased by 15~20. It also liberates the operator from manual measurement, saving manpower, and no longer needs to carry out double-wire measurement in the high-temperature environment in front of the crystallizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] There are 3 drawings in this application, including: Figure 1 This is a schematic diagram of the structure of the liquid slag thickness measuring device. Figure 11 is a probe, 2 is an infrared temperature measuring instrument, 3 is a fixing bracket, 4 is a protective cover, 5 is a transmission cable protection tube, 6 is a pipe bracket, 7 is a temperature sensing chamber, 9 is a crystallizer cover, 10 is a transmission cable, 11 is a data processing display, and 12 is a crystallizer.

[0016] Figure 2 It is a schematic diagram of the longitudinal cross-sectional structure of the probe 1 of the liquid slag thickness measuring device. Figure 2 In the figure, 8 is the temperature sensing surface, 13 is the solid slag layer, 14 is the molten slag layer, 15 is the liquid slag layer, and 16 is the molten steel; point a is the position of the upper surface temperature line aa of the solid slag on the temperature sensing surface 8 in the temperature sensing cavity 7, point b is the position of the temperature boundary line bb between the solid slag and the molten slag on the temperature sensing surface 8 in the temperature sensing cavity 7, point c is the position of the temperature boundary line cc between the molten slag and the liquid slag on the temperature sensing surface 8 in the temperature sensing cavity 7, point d is the position of the temperature boundary line dd between the liquid slag and the molten steel on the temperature sensing surface 8 in the temperature sensing cavity 7, point e and point f are the positions of the two edge lines of the bottom square frame in the temperature sensing cavity 7 respectively, point O is the position of the top edge oo of the temperature sensing surface 8, L is the thickness of the probe 1, Y is the thickness of the liquid slag layer, and α is the angle between the long right-angled side of the temperature sensing cavity 7 in the probe 1 and its hypotenuse.

[0017] Figure 3 This is an enlarged top view of the probe of the liquid slag thickness measuring device.

[0018] The several parallel lines in the figure are the temperatures or boundary lines of different solid and molten bodies, among which line aa is the upper surface temperature line of solid slag on the temperature sensing surface 8 in the temperature sensing cavity 7 of the probe 1, line bb is the temperature boundary line between solid slag and molten slag on the temperature sensing surface 8 in the temperature sensing cavity 7, line cc is the temperature boundary line between molten slag and liquid slag on the temperature sensing surface 8 in the temperature sensing cavity 7, line dd is the temperature boundary line between liquid slag and molten steel on the temperature sensing surface 8 in the temperature sensing cavity 7, line ee and line ff are the bottom box edge lines in the temperature sensing cavity 7, and line oo is the top edge line of the temperature sensing surface 8.

[0019] Example In order to better disclose this invention, the following description is given below regarding the implementation of the invention.

[0020] Example 1. A device for continuously monitoring the thickness of a continuous casting liquid mold slag layer, used for continuously monitoring the thickness of a liquid mold slag layer in a large slab crystallizer. The specific structure of the device is shown in the attached figure. Figure 1As shown, it mainly consists of a probe 1, an infrared temperature measuring instrument 2, a fixing bracket 3, a protective cover 4, a protective gas pipeline 5, a pipeline bracket 6, a temperature sensing cavity 7, a temperature sensing surface 8, a crystallizer cover 9, a transmission cable 10 and a data processing display 11, wherein: the probe 1 is an inverted right-angled triangle cavity object with a wall thickness of L=10mm, an upper end opening, a lower end sealing, and an opening width of the cavity object of 30mm. The long right-angled side of the probe 1 is 150mm. The angle α between the long right-angled side of the temperature sensing cavity 7 in the probe 1 and its hypotenuse is 30°. The probe 1 is made of aluminum-carbon refractory material; the long right-angled side of the probe 1 is perpendicular to the surface of the molten steel in the continuous casting crystallizer. 1 is the opening end of the cavity, the opening end of the probe 1 is installed and fixed on the protective cover 4 by means of pulling and inserting, the inner wall of the hypotenuse of the temperature sensing cavity 7 of the probe 1 is the temperature sensing surface 8, and there is an infrared temperature measuring instrument 2 fixed to the side wall of the protective cover 4 by a fixing bracket 3 directly above the probe 1, the infrared temperature measuring instrument 2 directly irradiates the aforementioned temperature sensing surface 8, the infrared temperature measuring instrument 2 is connected to the data processing display 11 through a transmission cable 10, a transmission cable protection tube 5 is provided on the outside of the transmission cable 10, the measuring instrument protection cover 4 is fixed on the transmission cable protection tube 5, and the transmission cable protection tube 5 is fixed on the crystallizer cover 9 through a pipe bracket 6.

[0021] The liquid protective slag layer thickness measuring device with the above structure is used to measure the liquid slag thickness. The specific operation steps are as follows:

[0022] The tip of the probe 1 of the device is directly inserted downward into the crystallizer 12 , passing through the solid slag 13 , the molten slag 14 , the liquid slag 15 and reaching the molten steel 16 .

[0023] Turn on the infrared temperature measuring instrument 2 and the data processing display 11 to receive the infrared signal radiated by the temperature sensing surface 8 in the temperature sensing cavity 7 to measure the temperature; 3. When the temperature line on the temperature sensing surface 8 is relatively stable, compare the previously measured temperatures of cc, line 1300°C and dd, line 1500°C, measure the horizontal distance X=m1 between the two lines, and calculate: Y=m1 / tg30° to get the thickness value of the liquid protective slag Y=1.732m1.

[0024] In the implementation of this project, it was measured in advance that the temperature of the molten steel zone 14 below the point line d was 1500°C; the temperature of the liquid slag temperature zone 13 above the point line d and below the point line c was 1300°C; the temperature of the molten slag temperature zone 12 above the point line c and below point b was 800°C; and above the point line b was the solid slag temperature zone 11.

[0025] The device was used to dynamically detect liquid slag for 100 consecutive heats, and the surface qualification rate of the steel ingots reached 99.68%, 1.2 percentage points higher than before, and the casting speed increased by 12.20%.

[0026] Embodiment 2. A device for continuously monitoring the thickness of a slag layer of liquid protective slag in continuous casting, the specific structure of which is basically the same as that of Embodiment 1, and is used for continuous monitoring of the thickness of a slag layer of liquid protective slag in a medium and thick plate crystallizer, wherein the wall thickness L of the probe 1 is 12 mm, the opening width of the cavity object is 40 mm, the long right-angled side of the probe 1 is 180 mm, the angle α between the long right-angled side of the temperature-sensing cavity 7 in the probe 1 and its hypotenuse is 30°, and the probe 1 is made of magnesium-carbon refractory material.

[0027] In this implementation, the temperature of the molten steel zone 14 below the point line d is measured in advance using the above-mentioned device to be 1530°C; the temperature of the liquid slag temperature zone 13 above the point line d and below the point line c is 1320°C.

[0028] According to the operating steps described in Example 1, when the temperature line on the temperature sensing surface 8 is relatively stable, compare with the pre-set cc line at 1320°C and dd line at 1530°C, measure the horizontal distance X=m2 between the two lines, and calculate: Y=m2 / tg30° to obtain the thickness value Y=1.732m2 of the liquid protective slag.

[0029] The device was used to conduct dynamic detection of liquid slag for 100 consecutive heats, and the surface qualification rate of the steel ingots reached 99.56%, which was 1.15 percentage points higher than before, and the casting speed was increased by 13.40%.

Claims

1. A device for continuously monitoring the thickness of a continuous casting liquid protective slag layer, characterized in that The device mainly consists of a probe 1, an infrared temperature measuring instrument 2, a fixed bracket 3, a protective cover 4, a protective gas pipeline 5, and a pipeline bracket 6, wherein: the probe 1 is an inverted right-angled triangular cavity object with a certain wall thickness L, an upper end opening, a lower end sealing, and the right-angled triangular cavity object is provided with a temperature sensing cavity 7, the long right-angled side of the probe 1 is perpendicular to the surface of the molten steel in the continuous casting crystallizer, the short right-angled side of the probe 1 is the open end of the temperature sensing cavity 7, the open end of the probe 1 is installed and fixed on the protective cover 4 by a quick replacement method, and the inner wall of the hypotenuse of the temperature sensing cavity 7 of the probe 1 is a temperature sensing surface 8; an infrared temperature measuring instrument 2 fixed to the side wall of the protective cover 4 by a fixed bracket 3 is provided directly above the probe 1, the infrared temperature measuring instrument 2 is directly irradiated on the temperature sensing surface 8, the infrared temperature measuring instrument 2 is connected to the data processing display 11 through a transmission cable 10, a transmission cable protection tube 5 is provided on the outer side of the transmission cable 10, the measuring instrument protection cover 4 is fixed on the transmission cable protection tube 5, and the transmission cable protection tube 5 is fixed on the crystallizer cover 9 through the pipeline bracket 6.

2. The device for continuously monitoring the thickness of the continuous casting liquid mold slag layer according to claim 1, characterized in that The probe 1 of the device is made of a material with fast heat conduction and stable physical and chemical properties at high temperatures.

3. A method for using the device for continuously monitoring the thickness of the continuous casting liquid mold slag layer as claimed in claim 1, characterized in that Follow the steps below: (1) directly inserting the tip of the probe 1 of the device downward into the crystallizer 12, passing through the solid slag 13, the molten slag 14, the liquid slag 15 and reaching the molten steel 16; (2) Turn on the infrared temperature measuring instrument 2 and the data processing display 11, receive the infrared signal radiated by the temperature sensing surface 8 in the temperature sensing chamber 7 to measure the temperature, and determine the respective temperatures and positions of the temperature boundary line cc between the molten slag and the liquid slag and the temperature boundary line dd between the liquid slag and the molten steel on the temperature sensing surface 8; (3) When the temperature line on the temperature sensing surface 8 is relatively stable, compare the temperatures of the cc line and the dd line measured in step 1, measure the horizontal distance X between the two, and use trigonometric functions to calculate the thickness Y of the liquid protective slag, Y=X / tgα. (4) Based on the standard thickness range of liquid slag given by the big data model and the real-time thickness Y of the liquid protective slag obtained in step 3, the amount of solid slag added is controlled to ensure that the slag layer thickness of the liquid protective slag is always within the standard thickness range.

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