A method and device for measuring the metallurgical length of an arc-shaped continuous casting machine

Abstract

This invention relates to the field of metallurgical technology, and more particularly to a method and apparatus for measuring the metallurgical length of an arc-shaped continuous casting machine. The method includes setting the current and frequency of an electromagnetic stirring device to apply electromagnetic force to the continuous casting liquid; processing the solidified billet into a low-magnification sample; immersing and etching the low-magnification sample in an acid pickling solution at a set temperature and ratio; rinsing and drying the surface of the bright white band on the low-magnification sample, measuring the position of the bright white band, and obtaining the billet shell thickness; and calculating the comprehensive solidification coefficient and metallurgical length of continuous casting using solidification theory. This invention solves the problems of the inherent danger and high implementation difficulty of existing methods for measuring the shell thickness of continuously cast billets.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method and device for measuring the metallurgical length of an arc-shaped continuous casting machine. Background Technology

[0002] Steel materials are widely used in mechanical engineering, automotive transportation, tool structures, and other fields. According to statistics from the World Steel Association, over 90% of steel is produced through continuous casting. With the rapid development of the national economy and modern technology, the performance requirements for mechanical materials and special steels are constantly increasing. As the first step in material forming, continuous casting greatly affects the quality and performance of materials and their downstream products. Therefore, ensuring the quality of continuously cast billets during the continuous casting production process is of great significance.

[0003] Accurately determining the solidified shell thickness, comprehensive solidification coefficient, and metallurgical length at specific locations in continuous casting is of great significance for optimizing the setting of final electromagnetic stirring (F-EMS) and final light reduction parameters, maximizing the role of F-EMS and final light reduction in reducing center segregation and center porosity. At the same time, the solidified shell thickness can be used to analyze the causes of casting defects, the rationality of the secondary cooling water distribution system, and to measure the potential for increasing continuous casting speed.

[0004] Currently, the main methods for determining the thickness of the solidified shell of a cast billet include the nail shot test, the shell piercing test, and the isotope method. The nail shot test, as the most widely used detection method, has been gradually phased out due to its inherent dangers. The shell piercing test requires damaging the cast billet, which can easily cause production accidents. The isotope method uses radioactive metals and has potential radiation risks. Summary of the Invention

[0005] To address the shortcomings of existing methods, this invention solves the problems of danger and high implementation difficulty in existing continuous casting billet shell thickness measurement methods.

[0006] The technical solution adopted in this invention is: a method and device for measuring the metallurgical length of an arc-shaped continuous casting machine, comprising the following steps:

[0007] Step 1: Set the current and frequency of the electromagnetic stirring device to apply electromagnetic force to the continuous casting liquid through electromagnetic stirring;

[0008] Furthermore, the current range is 10A-1000A, and the frequency range is 0.1Hz-100Hz.

[0009] Furthermore, the electromagnetic stirring method can be either alternating or continuous.

[0010] Step 2: After the billet solidifies, the billet is processed into a low-magnification sample.

[0011] Step 3: Immerse and etch the low-magnification sample of the cast billet using an acid pickling solution with a set temperature and ratio;

[0012] Furthermore, the temperature range is set to 60-80℃; the pickling solution is a mixture of industrial hydrochloric acid and water in a volume ratio of 1:1; and the soaking time ranges from 5 to 30 minutes.

[0013] Step 4: Rinse and dry the surface of the white bright band on the low magnification sample of the billet, measure the position of the white bright band, and obtain the thickness of the billet shell;

[0014] Furthermore, the formula for calculating the shell thickness δ is as follows:

[0015] δ=(δ1+δ2+δ3+δ4) / 4;

[0016] Among them, δ1 is the distance between the bright white band with the geometric center of the billet as the reference and the upper longitudinal edge of the billet, δ3 is the distance between the bright white band with the geometric center of the billet as the reference and the lower longitudinal edge of the billet, δ2 is the distance between the bright white band with the geometric center of the billet as the reference and the right longitudinal edge of the billet, and δ4 is the distance between the bright white band with the geometric center of the billet as the reference and the left longitudinal edge of the billet.

[0017] Step 5: Calculate the overall solidification coefficient and metallurgical length of continuous casting using solidification theory;

[0018] Furthermore, the formula for calculating the overall solidification coefficient is as follows:

[0019]

[0020] Where K is the overall solidification coefficient, δ is the billet shell thickness, L is the distance from the location where the billet shell thickness is measured to the meniscus, and v is the drawing speed.

[0021] Furthermore, the formula for calculating the metallurgical length is:

[0022]

[0023] Among them, L e Where is the metallurgical length, K is the comprehensive solidification coefficient, v is the casting speed, and D is the billet thickness.

[0024] The metallurgical length measuring device for the arc-shaped continuous casting machine includes: a tundish, a crystallizer, and an electromagnetic stirring device. The tundish is used to pour molten steel into the crystallizer. The electromagnetic stirring device uses an induction coil to electromagnetically treat the continuously cast billet, causing the billet to form a segregated bright white band after solidification.

[0025] Furthermore, the electromagnetic stirring device is positioned 0.1-8.0m below the secondary cooling zone.

[0026] Furthermore, it also includes a control cabinet, which controls the sensing and excitation characteristics of the electromagnetic stirring device.

[0027] The beneficial effects of this invention are:

[0028] Electromagnetic stirring is applied at the end of the continuous casting solidification process. Electromagnetic stirring is often used to improve the solidification structure, while this invention is used to form local negative segregation in the solidification region, which is used to address the white bright band that appears in low-magnification pickling. The pickling process is used to etch the billet at low magnification, which can clearly and accurately determine the thickness of the billet shell. Based on the thickness of the billet shell, the comprehensive solidification coefficient and metallurgical length of continuous casting are calculated by solidification theory. The measurement accuracy of the metallurgical length value is high. This invention does not damage the billet and has high safety. Attached Figure Description

[0029] Figure 1 This is a flowchart of the metallurgical length measurement method for the arc-shaped continuous casting machine of the present invention;

[0030] Figure 2 This is a schematic diagram of the installation of the electromagnetic stirring device of the present invention;

[0031] Figure 3 (a) and Figure 3 (b) is a low-magnification microstructure diagram of the continuously cast billet under different test parameters of the present invention;

[0032] Figure 4 This is a diagram showing the simulation calculation results of the billet shell thickness under the continuous casting process parameters set in this invention;

[0033] Figure 5 This is a schematic diagram illustrating the calculation of the blank thickness value according to the present invention;

[0034] Figure 2 In the middle, 1. intermediate ladle, 2. crystallizer, 3. electromagnetic stirring device, 4. control cabinet, 5. control console, 6. continuous casting billet. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments. The drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0036] like Figure 1 As shown, a method for measuring the metallurgical length of an arc-shaped continuous casting machine includes the following steps:

[0037] Step 1: Using the electromagnetic stirring device installed at the end of the solidification zone of the continuous casting machine billet, set the electromagnetic stirring parameters at the end of the continuous casting according to the steel grade and continuous casting process parameters, including current and frequency, to enhance the stirring treatment of the continuous casting liquid core and make the billet show a bright white band.

[0038] The electromagnetic stirring device 3 is positioned at a point where 20%-30% of the billet is not yet solidified. Depending on the billet cross-section, specific steel grade, and production speed process parameters, the electromagnetic stirring device 3 is positioned 0.1-8.0m below the secondary cooling zone. The current range is 10A-1000A, and the frequency range is 0.1Hz-100Hz. The stirring method is either alternating or continuous. It utilizes its electromagnetic stirring effect to form a bright white band of segregation after the billet solidifies.

[0039] The essence of electromagnetic stirring is to enhance the movement of molten steel in the liquid phase cavity by using the electromagnetic force induced in the liquid phase cavity of the billet. The area that the end electromagnetic stirring can stir is the liquid phase region other than the billet shell thickness. When the electromagnetic stirring force is too large, it will cause local negative segregation in the solidification area. This negative segregation is the white bright band that appears in low-magnification pickling.

[0040] The solidification heat transfer model is based on the principles of heat transfer and uses ANSYS software to calculate the shell thickness under set conditions. The solid fraction and liquid fraction inside the continuously cast billet at different distances from the meniscus are calculated using ANSYS software, forming a distribution map of liquidus and solidus lines that varies with the distance from the meniscus. The thickness of the solidified shell is obtained by measuring at a certain unstirred position from the meniscus. The measurement method of the bright band is basically consistent with the simulation calculation of the solidification heat transfer model.

[0041] The following assumptions are made when ANSYS software is used to simulate and build physical models:

[0042] (1) Ignoring heat transfer in the direction of continuous casting billet pulling, the model is simplified to a two-dimensional unsteady heat conduction model;

[0043] (2) The continuous casting speed is constant and the heat transfer is in a stable state;

[0044] (3) The latent heat of solid-state phase change is much smaller than the latent heat of solidification, so the effect of solid-state phase change is ignored;

[0045] (4) The solidus and liquidus temperatures of the steel are constants;

[0046] (5) The phase density of the steel grade is constant;

[0047] (6) The heat transfer of convection in the liquid core of the continuously cast billet is simulated by the effective thermal conductivity.

[0048] The governing equations are two-dimensional unsteady heat conduction differential equations:

[0049]

[0050] In the formula: T is temperature, °C; t is time, s; λ is thermal conductivity, W / (m·℃); ρ is density, kg / m³ 3 ;f s denoted as solid fraction.

[0051] Initial conditions:

[0052] At t=0, the temperature inside crystallizer 2 is the same as the pouring temperature.

[0053] Boundary conditions:

[0054] Surface of continuously cast billet:

[0055] Crystallizer:

[0056] Second cold zone: q w =α(t) w -t c (4)

[0057] Insulation boundary conditions at the center of the billet:

[0058] In the formula, q w Heat flux density, W / m 2 A and B are constants; t w t represents the surface temperature of the cast billet, in °C. c The value is the cooling water temperature, in °C.

[0059] Step 2: After the billet solidifies, the billet is processed into a low-magnification sample using a machining tool.

[0060] Step 3: Etching the low-magnification sample of the cast billet with an acid pickling solution at a set temperature and ratio can clearly reveal the low-magnification structure of the cast billet, including the length and thickness of columnar crystals, equiaxed crystal regions, and possible bright white band features. This allows inspectors to perform defect analysis and rating of the low-magnification cast billet, easily making a preliminary judgment on the quality of the cast billet.

[0061] The corrosion conditions are: a set temperature of 60-80℃; and immersion in a 1:1 mixture of industrial hydrochloric acid and water for 5-30 minutes.

[0062] Step 4: Rinse the low-magnification sample of the billet clean and blow dry the surface where the white bright band is located. Measure the position of the white bright band and obtain the billet shell thickness value.

[0063] If a bright white band appears after hot hydrochloric acid etching, measure the distance from the bright white band to the edge of the billet using calipers. After multiple measurements, select the geometric centerline positions of the billet's transverse and longitudinal directions as reference data values, calculate the average value, and finally determine the billet shell thickness. Figure 5As shown, the billet shell thickness value = (δ1+δ2+δ3+δ4) / 4, where δ1 is the distance between the bright band based on the geometric center of the billet and the upper longitudinal edge of the billet, δ3 is the distance between the bright band based on the geometric center of the billet and the lower longitudinal edge of the billet, δ2 is the distance between the bright band based on the geometric center of the billet and the right longitudinal edge of the billet, and δ4 is the distance between the bright band based on the geometric center of the billet and the left longitudinal edge of the billet.

[0064] Step 5: Based on the measured billet shell thickness, calculate the comprehensive solidification coefficient and metallurgical length of continuous casting using solidification theory.

[0065] Besides actual measurement, such as the nail-shooting method, lead-filling method, and isotope detection method, the second most common method for determining the thickness of the billet shell is computer simulation. Computer simulation has a lower cost and a shorter testing cycle, but the simulation calculation differs slightly from the actual measurement.

[0066] After measuring the thickness of the blank shell, according to the formula Calculate the overall solidification coefficient K value, in mm / min. 1 / 2 δ represents the billet shell thickness in mm; L represents the distance from the measurement point to the meniscus in m; v represents the casting speed in m / min; using the comprehensive solidification coefficient K, and then according to the formula... Calculate the metallurgical length L e , unit m; D is the billet thickness, unit mm; v is the casting speed, unit m / min.

[0067] The metallurgical length measuring device for the arc-shaped continuous casting machine includes: a tundish 1, a crystallizer 2, and an electromagnetic stirring device 3. During continuous casting production, molten steel is poured into the crystallizer 2 through the tundish 1, and a shell is formed in the continuously cast billet 6 inside the crystallizer 2. According to the characteristics of the steel grade, the processing parameters of the electromagnetic stirring device 3, including current and frequency, are set through the control console 5 in the main control room, and the parameters are transmitted to the control cabinet 4. The control cabinet 4 controls the induction and excitation characteristics of the electromagnetic stirring device 3. The electromagnetic stirring device 3 performs electromagnetic processing on the continuously cast billet 6 passing through the induction coil. The electromagnetic stirring device 3 can be model DJM2-370SNF.

[0068] Example 2:

[0069] like Figure 3 As shown in (a), taking the production of 45 steel with a cross-section of 220mm×260mm as an example, the tundish superheat is 25℃, the casting speed is 1.05m / min, the crystallizer water temperature difference is 7℃, the secondary cooling water flow rate is 0.25L / kg, the F-EMS current parameters are set to 400A, the frequency is 6Hz, the distance from the final stirring position to the meniscus is 10.15m, and the thickness δ of the billet shell after processing and pickling is 80mm; the final stirring position, casting speed, and solidified billet shell thickness data are substituted into the formula... The overall solidification coefficient K of the continuous casting machine under this cooling intensity was found to be 25.73 mm / min. 1 / 2 Substitute K into the expression The continuous casting metallurgical length L under this continuous casting process is obtained. e It is 22.68m.

[0070] Example 3:

[0071] like Figure 3 As shown in (b), taking the production of 45 steel with a cross-section of 220mm×260mm as an example, the tundish superheat is 28℃, the casting speed is 1.05m / min, the crystallizer water temperature difference is 7℃, the secondary cooling water flow rate is 0.20L / kg, the F-EMS current parameters are set to 400A, the frequency is 6Hz, the distance from the final stirring position to the meniscus is 10.15m, and the thickness δ of the billet shell after processing and pickling is 73mm; the final stirring position, casting speed, and solidified billet shell thickness data are substituted into the formula... The overall solidification coefficient K of the continuous casting machine under this cooling intensity was found to be 23.48 mm / min. 1 / 2 Substitute K into the equation The continuous casting metallurgical length L under this continuous casting process is obtained. e It is 27.24m.

[0072] Example 4:

[0073] like Figure 4 As shown, using 45 steel from an electric arc furnace steelmaking plant as the research steel grade and a 220mm x 260mm cross-section billet as the research object, a physical model was established. The superheating temperature of the tundish was 25℃, the casting speed was 1.05m / min, the temperature difference of the crystallizer water was 7℃, and the secondary cooling water flow rate was 0.25L / kg as the simulation model calculation parameters. The solid fraction and liquid fraction inside the continuously cast billet at different distances from the meniscus were calculated using ANSYS, and the corresponding values ​​were used to form liquidus and solidus distribution diagrams that vary with distance. The solidified billet shell thickness measured at the unstirred position 10.15m from the meniscus was 81.61mm, which is basically consistent with the simulation calculation.

[0074] When implementing this invention, applying end electromagnetic stirring at the end of the continuous casting solidification stage is simple, does not damage the billet, and is highly safe. Using a specific pickling process to etch at low magnification, the billet shell thickness can be clearly and accurately determined. Based on the billet shell thickness, the comprehensive solidification coefficient and metallurgical length of continuous casting are calculated through solidification theory, and the measurement accuracy of the metallurgical length value is high.

[0075] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method of measuring the metallurgical length of an arc furnace, characterized in that, It comprises the following steps: Step 1, setting the current and frequency of the electromagnetic stirring device, and applying electromagnetic force to the continuous casting liquid through electromagnetic stirring; Step 2, processing the casting blank into a casting blank macro sample after the casting blank is solidified; Step 3, soaking and eroding the casting blank macro sample with the pickling solution under the set temperature and proportion; Step 4, rinsing and blowing dry the surface of the white band of the casting blank macro sample, measuring the position of the white band, and obtaining the shell thickness; Using ANSYS software to calculate the shell thickness under the set conditions; calculating the solid phase rate and liquid phase rate inside the continuous casting blank at different distances from the meniscus by ANSYS software, forming the liquidus and solidus distribution diagram varying with the distance from the meniscus, and obtaining the solidified shell thickness at a certain final stirring position from the meniscus; Or measuring the distance from the white band to the side of the casting blank with a caliper to obtain the shell thickness δ, the formula is: δ=(δ1+δ2+δ3+δ4) / 4; Wherein, δ1 is the distance from the white band to the upper edge of the casting blank in the longitudinal direction with the geometric center of the casting blank as the reference, δ3 is the distance from the white band to the lower edge of the casting blank in the longitudinal direction with the geometric center of the casting blank as the reference, δ2 is the distance from the white band to the right edge of the casting blank in the longitudinal direction with the geometric center of the casting blank as the reference, and δ4 is the distance from the white band to the left edge of the casting blank in the longitudinal direction with the geometric center of the casting blank as the reference; Step 5, calculating the comprehensive solidification coefficient and metallurgical length of the continuous casting through the solidification theory.

2. The arc-shaped continuous caster metallurgical length measurement method according to claim 1, characterized by, The current range is 10A-1000A, and the frequency range is 0.1Hz-100Hz.

3. The arc-shaped continuous caster metallurgical length measurement method according to claim 1, characterized by, The electromagnetic stirring mode is alternating or continuous.

4. The arc-con caster metallurgical length measurement method of claim 1, wherein, The set temperature range is 60-80℃; the pickling solution under the proportion is a mixture of industrial hydrochloric acid and water with a volume ratio of 1:1; and the soaking time range is 5-30min.

5. The arc-con caster metallurgical length measurement method of claim 1 wherein, The formula for calculating the comprehensive solidification coefficient is: wherein, K is the integrated solidification coefficient, δ is the shell thickness, L is the length of the position at which the shell thickness is measured from the meniscus, v is the withdrawal rate.

6. The arc-concentrating continuous caster metallurgical length measurement method according to claim 1, characterized by, The formula for calculating the metallurgical length is: wherein, L e is the metallurgical length, K is the integrated solidification coefficient, v is the casting speed, D is the slab thickness.

7. An apparatus for measuring the metallurgical length of an arc furnace, according to any one of claims 1 to 6, characterized in that, It comprises: The tundish, the crystallizer and the electromagnetic stirring device, the tundish is used for pouring the molten steel into the crystallizer; The electromagnetic stirring device performs electromagnetic treatment on the continuous casting blank through the induction coil, so that the white band is formed after the casting blank is solidified.

8. The arc-concentrating continuous caster metallurgical length measuring device according to claim 7, characterized in that, The electromagnetic stirring device is arranged at 0.1-8.0m below the secondary cooling zone.

9. The arc-concentrating continuous caster metallurgical length measuring device according to claim 7, wherein It also comprises a control cabinet which controls the induction and excitation characteristics of the electromagnetic stirring device.

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