An experimental device and method for simulating the solidification structure of a continuous casting billet

Abstract

The application discloses an experimental device for simulating solidification structure of continuous casting billets, which comprises a crystallization unit and a temperature monitoring unit. The crystallization unit can enclose a crystallization cavity. A cooling channel is arranged in the water-cooled wall of the crystallization unit. The cooling channel is connected with a cooling medium source. The cooling intensity of the slab in the continuous casting production is simulated by controlling the temperature and flow rate of the cooling medium. The test element of the temperature monitoring unit can monitor the temperature of the cooling medium in the crystallization cavity in real time, so as to accurately restore the solidification process of the continuous casting billets. The application also discloses an experimental method for simulating solidification structure of continuous casting billets. The target unit is selected, and the cooling medium flow rate parameter is set to restore the change process of the cooling intensity of the surface of the continuous casting billets with time, and the heat flow density of the solidification process is analyzed. After the solidification is completed, the simulation unit is obtained, and the solidification structure of the simulation unit is analyzed. The application can accurately simulate the change process of the heat flow density of the surface of the slab in the continuous casting process, and provides convenience for the solidification structure research of the continuous casting billets.

Description

Technical Field

[0001] This invention relates to the field of continuous casting production technology, and in particular to an experimental apparatus and method for simulating the solidification structure of continuously cast billets. Background Technology

[0002] Continuous casting significantly improves billet production efficiency, shortens the time from molten steel to billet, and is easily automated. However, during solidification, continuously cast billets often exhibit problems such as coarse dendrites and severe central segregation. These solidification defects greatly affect the rollability and mechanical properties of the billet, reducing product yield. However, due to the high temperature, opacity, and complex multiphysics field within the billet during continuous casting, studying the influence of continuous casting process parameters on the billet's solidification structure is extremely difficult.

[0003] To investigate the influence of continuous casting process parameters on solidification microstructure, three main methods were developed: industrial experiments, numerical simulation, and physical simulation. While industrial experiments can accurately explain the influence of continuous casting process parameters on the solidification process of the billet, their high cost limits widespread implementation. Numerical simulation can predict the solidification microstructure of the billet at low cost, but its limitations in solidification theory and computer computing power require numerous assumptions, leading to discrepancies between simulation results and actual conditions. Physical simulation offers the advantages of low cost and accurate experimental results. Using a small amount of molten steel to simulate the solidification process of the continuously cast billet effectively reduces the cost of industrial experiments. Furthermore, using molten steel with the same composition as the billet allows for accurate simulation of the solidification process, resulting in a solidification microstructure closer to the actual billet. However, because the billet passes sequentially through the crystallizer and secondary cooling zone during continuous casting, the surface cooling intensity changes over time. Few physical simulation devices or methods can accurately reproduce the dynamic cooling process of the continuously cast billet and obtain a solidification microstructure close to reality.

[0004] Therefore, how to simulate the dynamic cooling process of continuous casting plates, thereby facilitating the study of the solidification structure of continuous casting billets, has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide an experimental apparatus and method for simulating the solidification structure of continuously cast billets, so as to solve the problems existing in the prior art, and enable the experimental apparatus to simulate the dynamic cooling process of continuously cast billets, thus providing convenient conditions for the study of the solidification structure of continuously cast billets.

[0006] To achieve the above objectives, the present invention provides the following solution: The present invention provides an experimental apparatus for simulating the solidification structure of continuously cast billets, comprising:

[0007] A crystallization unit, the crystallization unit comprising a water-cooled wall and a base;

[0008] When simulating continuous casting slab, the crystallization unit also includes a heat-insulating wall. There are two sets of water-cooled walls and two sets of heat-insulating walls. The two sets of water-cooled walls are arranged in parallel and are arranged parallel to the side with the larger area of ​​the simulated continuous casting slab. The two sets of heat-insulating walls are arranged in parallel and are perpendicular to the water-cooled walls. The base is located at the bottom of the water-cooled walls and the heat-insulating walls. The water-cooled walls, the heat-insulating walls and the base form a crystallization cavity that can accommodate the melt.

[0009] When simulating continuous casting of square billet, there are four sets of water-cooled walls, adjacent water-cooled walls are perpendicular to each other, the base is located at the bottom of the structure formed by the water-cooled walls, and the water-cooled walls and the base form a crystallization cavity that can accommodate the melt.

[0010] The water-cooled wall is provided with a cooling channel, which is connected to a cooling medium source. The insulation wall and the base are both provided with an insulation layer on the side near the crystallization cavity.

[0011] A temperature monitoring unit, comprising a testing element capable of monitoring the temperature of the water-cooled wall and the cooling medium within the cooling channel.

[0012] Preferably, the water-cooled wall includes a copper plate and a water jacket, the copper plate has a U-shaped groove, the copper plate is connected to the water jacket, the water jacket and the U-shaped groove form the cooling channel, the insulation layer includes refractory bricks and insulation boards, and the copper plate and the refractory bricks form the inner wall of the crystallization cavity.

[0013] Preferably, the cooling channels are parallel to the height direction of the crystallization cavity, and there are multiple cooling channels arranged at equal intervals; all the cooling channels are connected to the cooling medium source, and a pressure equalization chamber is provided between the cooling channels and the cooling medium source; valves and water pumps are also provided between the cooling channels and the cooling medium source.

[0014] Preferably, the cooling channel has a rectangular cross-section, the length of the cross-section is 8mm to 15mm, the width of the cross-section is 4mm to 8mm, and the spacing between adjacent cooling channels is 10mm to 16mm.

[0015] Preferably, when simulating continuous casting of a slab, the distance between the two insulation walls is the length of the crystallization cavity, the distance between the two water-cooled walls is the width of the crystallization cavity, and the distance between the top of the water-cooled wall and the insulation wall and the top of the base is the height of the crystallization cavity.

[0016] When simulating continuous casting of a square billet, the maximum distance between two water-cooled walls arranged opposite each other is the length of the crystallization cavity, the minimum distance between two water-cooled walls arranged opposite each other is the width of the crystallization cavity, and the distance between the top of the water-cooled wall and the top of the base is the height of the crystallization cavity.

[0017] The length L of the crystallization cavity is 80mm to 500mm, the width W of the crystallization cavity is 80mm to 500mm, and the height H of the crystallization cavity is 200mm to 800mm.

[0018] Preferably, the temperature monitoring unit further includes a paperless recorder, the test element is connected to the paperless recorder, the test element is a thermocouple, and the number of test elements is multiple sets.

[0019] Preferably, the insulation layer consists of multiple layers, each including refractory bricks and insulation boards, and adjacent insulation layers are detachably connected.

[0020] Preferably, the experimental apparatus for simulating the solidification structure of continuously cast billets further includes a control unit, and both the crystallization unit and the temperature monitoring unit are connected to the control unit.

[0021] The present invention also provides an experimental method for simulating the solidification structure of a continuously cast billet, comprising the following steps: selecting a target unit, setting the cooling medium flow rate parameters to recreate the change process of cooling intensity on the surface of the continuously cast billet over time, analyzing the heat flux density during the solidification process, obtaining a simulation unit after solidification, and analyzing the solidification structure of the simulation unit.

[0022] Preferably, the experimental method for simulating the solidification structure of continuously cast billets of the present invention includes the following steps:

[0023] Step 1: Adjust the internal dimensions of the crystallizer in the simulation device.

[0024] Select a target unit on the continuously cast billet and determine the length L of the target unit. u ', Width W u '、and height H u ';

[0025] When the target unit is a continuously cast slab, the length L of the target unit is... u = 100mm~420mm, width W u The width W' of the continuously cast slab is equal to that of the slab, and the height H is equal to that of the slab. u =50mm~650mm; A simulation unit is set inside the crystallization chamber, and the size of the simulation unit is controlled to be the same as the size of the target unit, that is, the length L of the simulation unit is... u =L u ', width W u=W u ', height H u =H u '; Make the inner length of the crystallization cavity L = L u +80mm~150mm, so that the inner width W of the crystallization cavity is W=W u The inner cavity height H of the crystallization cavity is made equal to H. u +150mm~200mm;

[0026] When the target unit is a continuously cast square billet, the length L of the target unit is... u 'The length L is equal to that of the continuously cast billet on site, and the width W' u The width W of the billet is equal to that of the continuously cast billet, and the height H is equal to that of the billet. u =50mm~650mm; A simulation unit is set inside the crystallization chamber, and the size of the simulation unit is controlled to be the same as the size of the target unit, that is, the length L of the simulation unit is... u =L u ', width W u =W u ', height H u =H u '; Make the inner length of the crystallization cavity L = L u Width W = W u Height H = H u +150mm~200mm;

[0027] Step 2: Set the cooling medium flow rate parameters and monitoring element parameters.

[0028] Using flow rate calculation formulas, the cooling medium flow rate for the simulation experiment was determined based on the water flow rate at each cooling stage of the continuously cast billet. Using cooling time calculation formulas for each cooling stage, the cooling time for the simulation experiment was determined based on the billet pulling speed, crystallizer height, and secondary cooling section length of the continuously cast billet. The water flow rate was controlled as Q0 from 0 to t0s after casting, Q1 from t0 to t1s, Q2 from t1 to t2s, Q3 from t2 to t3s, and so on, until t...t... n-1 ~t n The water flow rate of s is Q n The formulas for calculating the water flow rate in each cooling stage are as follows:

[0029] In the crystallizer stage, Q0 = k0 × Q0' × S / S'

[0030] In the second cooling phase, Q1 = k1 × Q1' 0.89 ×W / W'+40

[0031] Two cooling stages, Q2 = k1 × Q2' 0.89 ×W / W'+40

[0032] Two cooling stages, Q3 = k1 × Q3' 0.89 ×W / W'+40

[0033] ...

[0034] In the second cooling phase n, Q n =k1×Q n ' 0.89 ×W / W'+40

[0035] The formulas for calculating the cooling time of each cooling stage are as follows:

[0036] In the crystallizer stage, t0 = H0' / V'

[0037] Second cooling phase 1, t1=H1' / V'

[0038] Two cooling stages, t2 = H2' / V'

[0039] Two cooling stages, t3 = H3' / V'

[0040] ...

[0041] Second cooling n-stage, t n =H n ' / V'

[0042] Where Q0 is the cooling medium flow rate during the crystallizer stage of the simulation experiment, in L·min -1 k0 is the correction coefficient for the crystallizer stage, with a value ranging from 0.36 to 0.42; Q0' is the cooling medium flow rate of the on-site continuous casting crystallizer, in L·min. -1 S and S' represent the cooling area of ​​the molten steel in the simulation experiment and the cooling area of ​​the molten steel in the on-site continuous casting mold, respectively, in meters (m²). 2 Q1, Q2, Q3...Q n These represent the cooling medium flow rates for the simulated cooling stages one, two, three, ... n, in L·min. -1 k1 is the correction coefficient for the secondary cooling stage, with a value ranging from 3.45 to 3.55; Q1', Q2', Q3'...Q n These are the cooling medium flow rates for the first, second, third, ... nth stages of continuous casting, expressed in L·min. -1 t0 is the cooling time of the simulated crystallizer stage, in seconds; H0' is the height of the on-site continuous casting crystallizer, in meters; V' is the on-site continuous casting billet pulling speed, in meters per second. -1 ;t1, t2, t3……t nThese represent the cooling times for the simulated second-cooling-first stage, second-cooling-second stage, second-cooling-third stage, ..., second-cooling-nth stage, in seconds; H1', ​​H2', H3'...H n 'These are the lengths of the first cooling stage, the second cooling stage, the third cooling stage, ... the nth cooling stage of the on-site continuous casting machine, in meters;

[0043] Cooling water with a flow rate of Q0 is introduced into the crystallization cavity;

[0044] Step 3: Simulate the solidification process of the continuously cast billet on site

[0045] According to the steel composition requirements, molten steel is smelted, and the composition and superheat of the molten steel are controlled to be consistent with the continuous casting billet on site. After the target tapping temperature is reached, the molten steel is poured into the inner cavity of the crystallization cavity.

[0046] Step 4: Analyze the heat flux density during the solidification process.

[0047] The heat flux density was calculated and recorded in real time according to the heat flux density formula to obtain the heat flux density curve. The influence of different process parameters on the surface heat flux density during the solidification process of the continuously cast billet was obtained by analyzing the heat flux density curve. The heat flux density formula is:

[0048]

[0049] Where q is the heat flux density (J·m -2 ·s -1 T1, T2, T3, T4, T5, and T6 represent the temperatures at different locations within the crystallization cavity, in °C; λ is the thermal conductivity of the crystallization cavity, in W·m. -1 ·℃ -1 x1, x2, x3, and x4 represent the temperature measurement distances at different locations within the crystallization cavity, where the measurement distance is the distance between the measurement location and the contact surface between the molten steel and the crystallization cavity, expressed in meters (m). c represents the specific heat of the cooling water, expressed in J·kg⁻¹. -1 ·℃ -1 ρ is the density of cooling water, in kg·m³. -3 ;

[0050] Step 5: Analyze the solidification structure of the simulation unit.

[0051] After the ingot has solidified, it is removed, cut, and the simulation unit is obtained. By detecting the macrostructure, microstructure, and element segregation of the simulation unit, the influence of different process parameters on the solidification structure of the continuously cast billet is obtained.

[0052] Compared with the prior art, the present invention achieves the following technical advantages: The experimental device for simulating the solidification structure of continuously cast billets of the present invention has a crystallization unit that can form a crystallization cavity, and a cooling channel is set inside the water-cooled wall. The cooling channel is connected to a cooling medium source. By controlling the temperature and flow rate of the cooling medium, the cooling intensity of the slab in continuous casting production is simulated. The testing element of the temperature monitoring unit can monitor the temperature of the cooling medium in the crystallization cavity in real time to accurately reproduce the solidification process of the continuously cast billet. At the same time, the experimental device for simulating the solidification structure of continuously cast billets of the present invention has a simple structure and is easy to operate. It uses a small amount of molten steel to simulate the solidification process of large slabs, reducing experimental costs by more than 90% compared with industrial experiments, and avoiding safety risks such as steel leakage and nozzle blockage in industrial experiments.

[0053] This invention also discloses an experimental method for simulating the solidification structure of continuously cast billets. A target unit is selected, and the flow rate parameters of the cooling medium are set to recreate the change in surface cooling intensity of the continuously cast billet over time. The heat flux density during solidification is analyzed, and the simulated unit is obtained after solidification. The solidification structure of the simulated unit is then analyzed. This experimental method for simulating the solidification structure of continuously cast billets can accurately simulate the change in surface heat flux density of the continuously cast billet during continuous casting, ensuring that the difference between the heat flux density of the simulated ingot and the heat flux density of the on-site continuously cast billet is less than 9%. The obtained billet has essentially the same surface heat flux density, macrostructure, microstructure, and segregation as the continuously cast billet, providing convenience for the study of the solidification structure of continuously cast billets. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of the experimental apparatus for simulating the solidification structure of continuously cast billets according to the present invention;

[0056] Figure 2 This is a top view schematic diagram of a portion of the experimental apparatus for simulating the solidification structure of continuously cast billets according to the present invention.

[0057] Figure 3 This is a schematic diagram showing the distribution of test elements in the experimental apparatus for simulating the solidification structure of continuously cast billets according to the present invention.

[0058] Figure 4 This is a schematic diagram of the simulation unit distribution of the experimental method for simulating the solidification structure of continuously cast billets according to the present invention;

[0059] Figure 5This is a schematic diagram of heat flux density statistics in an embodiment of the experimental method for simulating the solidification structure of continuously cast billets of the present invention.

[0060] Figure 6 This is a schematic diagram of the statistical results of the crystal zone ratio in an embodiment of the experimental method for simulating the solidification structure of a continuously cast billet of the present invention.

[0061] Figure 7 This is a schematic diagram of the statistical results of secondary dendrite spacing in an embodiment of the experimental method for simulating the solidification structure of continuously cast billets of the present invention.

[0062] Figure 8 This is a schematic diagram of the statistical results of Mo element distribution in an embodiment of the experimental method for simulating the solidification structure of continuously cast billets according to the present invention.

[0063] Wherein, 1 is a crystallization unit, 101 is a water-cooled wall, 102 is an insulation wall, 103 is a base, 104 is a cooling channel, 105 is a copper plate, 106 is a water jacket, 107 is a refractory brick, 108 is an insulation board, 109 is a pressure equalization chamber, 110 is a water pump, 111 is a valve, and 112 is a cooling medium source.

[0064] 2 is the temperature monitoring unit, 201 is the test element, C-1, C-2, C-3, C-4, C-5, and C-6 are all thermocouples, and 202 is the paperless recorder;

[0065] 3 is the control unit. Detailed Implementation

[0066] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] The purpose of this invention is to provide an experimental apparatus and method for simulating the solidification structure of continuously cast billets, so as to solve the problems existing in the prior art, and enable the experimental apparatus to simulate the dynamic cooling process of continuously cast billets, thus providing convenient conditions for the study of the solidification structure of continuously cast billets.

[0068] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0069] Please refer to Figure 1-8 ,in, Figure 1 This is a schematic diagram of the experimental apparatus for simulating the solidification structure of continuously cast billets according to the present invention. Figure 2 This is a top view schematic diagram of a portion of the experimental apparatus for simulating the solidification structure of continuously cast billets according to the present invention. Figure 3 This is a schematic diagram showing the distribution of test elements in the experimental apparatus for simulating the solidification structure of continuously cast billets according to the present invention. Figure 4 This is a schematic diagram of the simulation unit distribution of the experimental method for simulating the solidification structure of continuously cast billets according to the present invention. Figure 5 This is a schematic diagram of heat flux density statistics in an embodiment of the experimental method for simulating the solidification structure of continuously cast billets according to the present invention. Figure 6 This is a schematic diagram showing the statistical results of the crystal zone proportion in an embodiment of the experimental method for simulating the solidification structure of continuously cast billets according to the present invention. Figure 7 This is a schematic diagram showing the statistical results of secondary dendrite spacing in an embodiment of the experimental method for simulating the solidification structure of continuously cast billets according to the present invention. Figure 8 This is a schematic diagram of the statistical results of Mo element distribution in an embodiment of the experimental method for simulating the solidification structure of continuously cast billets according to the present invention.

[0070] This invention provides an experimental apparatus for simulating the solidification structure of a continuously cast billet, comprising a crystallization unit 1 and a temperature monitoring unit 2. The crystallization unit 1 includes a water-cooled wall 101 and a base 103. When simulating a continuously cast slab, the crystallization unit 1 further includes an insulating wall 102. There are two sets of both the water-cooled wall 101 and the insulating wall 102, arranged in parallel, with the water-cooled wall 101 parallel to the side of the simulated continuously cast billet with the larger area (i.e.,...). Figure 4 H u 'and W u In the simulated continuous casting of a square billet, there are four sets of water-cooled walls 101, with adjacent water-cooled walls 101 perpendicular to each other. The base 103 is located at the bottom of the water-cooled wall 101 and the insulation wall 102. The water-cooled wall 101, the insulation wall 102, and the base 103 form a crystallization cavity that can accommodate the melt. When simulating continuous casting of a square billet, there are four sets of water-cooled walls 101, with adjacent water-cooled walls 101 perpendicular to each other. The base 103 is located at the bottom of the structure formed by the water-cooled walls 101. The water-cooled walls 101 and the base 103 form a crystallization cavity that can accommodate the melt. A cooling channel 104 is provided inside the water-cooled wall 101. The cooling channel 104 is connected to the cooling medium source 112. The insulation wall 102 and the base 103 are provided with insulation layers on the side near the crystallization cavity. The temperature monitoring unit 2 includes a test element 201, which can monitor the temperature of the cooling medium in the water-cooled wall 101 and the cooling channel 104.

[0071] The experimental apparatus for simulating the solidification structure of continuously cast billets of the present invention includes a crystallization unit 1 that forms a crystallization cavity. A cooling channel 104 is provided within the water-cooled wall 101, and the cooling channel 104 is connected to a cooling medium source 112. By controlling the temperature and flow rate of the cooling medium, the cooling intensity of the continuously cast billet during continuous casting production is simulated. The testing element 201 of the temperature monitoring unit 2 can monitor the temperature of the cooling medium within the crystallization cavity in real time to accurately reproduce the solidification process of the continuously cast billet. Furthermore, the experimental apparatus for simulating the solidification structure of continuously cast billets of the present invention has a simple structure and is easy to operate. It uses a small amount of molten steel to simulate the solidification process of large continuously cast billets, reducing experimental costs by more than 90% compared to industrial experiments, and avoiding safety risks such as steel leakage and nozzle blockage associated with industrial experiments.

[0072] The water-cooled wall 101 includes a copper plate 105 and a water jacket 106. The copper plate 105 has a U-shaped groove and is connected to the water jacket 106. The water jacket 106 and the U-shaped groove form a cooling channel 104. A cooling medium source 112 is used to supply cooling medium into the cooling channel 104 to control the cooling intensity within the crystallization cavity. The insulation layer includes refractory bricks 107 and insulation boards 108. The copper plate 105 and refractory bricks 107 form the inner wall of the crystallization cavity. It should be noted that the thickness of the refractory bricks 107 is 10mm to 18mm, and the material can be selected from high-alumina bricks, dolomite bricks, magnesia-chrome bricks, silicon carbide bricks, or other refractory materials. The thickness of the insulation board 108 is 40mm to 60mm, and the material can be selected from ceramic fiberboard and glass fiberboard, or other insulation materials.

[0073] Specifically, the cooling channels 104 are parallel to the height direction of the crystallization chamber, and there are multiple cooling channels 104 arranged at equal intervals. All cooling channels 104 are connected to the cooling medium source 112. A pressure equalization chamber 109 is provided between the cooling channels 104 and the cooling medium source 112, with pressure equalization chambers 109 at both the cooling medium inlet and outlet to improve cooling uniformity. A valve 111 and a water pump 110 are also provided between the cooling channels 104 and the cooling medium source 112 to facilitate control of the cooling medium flow rate. In actual operation, cooling water can be selected as the cooling medium. During the experiment, water can be pre-circulated into the cooling channels 104 to expel gas, and pre-circulation of water can also avoid experimental errors caused by unstable water flow during the start-up phase of the water pump 110.

[0074] In this specific embodiment, the cross-section of the cooling channel 104 is rectangular, the length of the cross-section of the cooling channel 104 is 8mm to 15mm, the width of the cross-section of the cooling channel 104 is 4mm to 8mm, and the spacing between adjacent cooling channels 104 is 10mm to 16mm. When the simulated object is a continuously cast slab, the spacing between the two insulation walls 102 is the length of the crystallization cavity, and the spacing between the two water-cooled walls 101 is the width of the crystallization cavity; when the simulated object is a continuously cast square billet, the spacing between the two water-cooled walls 101 with a larger spacing is the length of the crystallization cavity, and the spacing between the two water-cooled walls 101 with a smaller spacing is the width of the crystallization cavity; the distance between the top of the water-cooled wall 101 and the top of the base 103 is the height of the crystallization cavity, the length L of the crystallization cavity is 80mm to 500mm, the width W of the crystallization cavity is 80mm to 500mm, and the height H of the crystallization cavity is 200mm to 800mm.

[0075] More specifically, the temperature monitoring unit 2 also includes a paperless recorder 202. The test element 201 is connected to the paperless recorder 202 to facilitate recording the temperature measured by the test element 201. The test element 201 is a thermocouple, and there are multiple sets of test elements 201 to enable temperature measurement at multiple points. In this specific embodiment, the test elements 201 are in two sets, symmetrically arranged on two water-cooled walls 101. Each set of test elements 201 includes 6 thermocouples. Thermocouple C-1 is inserted into copper plate 105, with the insertion point located at the intersection of the diagonals of copper plate 105. Thermocouple C-2 is located 1 / 12H directly below thermocouple C-1. Thermocouple C-3 is located 1 / 12H horizontally to the right of thermocouple C-1. Thermocouple C-4 is located 1 / 12H horizontally to the right of thermocouple C-2. Thermocouple C-5 is inserted into the inlet equalization chamber 109, and thermocouple C-6 is inserted into the outlet equalization chamber 109. The temperature measurement distances of thermocouples C-1, C-2, C-3, and C-4 are 3mm~5mm, 6mm~8mm, 9mm~11mm, and 12mm~14mm, respectively. The thermocouple assembly can measure the temperature of the copper plate 105, the cooling water in the inlet pressure equalization chamber 109, and the cooling water in the outlet pressure equalization chamber 109 in real time. Additionally, it should be noted that in this specific embodiment, the inlet of the cooling medium is located below the outlet of the cooling medium, extending the contact time between the cooling medium and the copper plate 105, thereby improving heat exchange efficiency and ensuring the accuracy of temperature control within the crystallization chamber.

[0076] In addition, there are multiple insulation layers, and adjacent insulation layers can be detached and connected. In practical applications, the height of the crystallization chamber can be adjusted by changing the number of insulation layers set on the base 103.

[0077] In addition, the experimental device for simulating the solidification structure of continuously cast billets also includes a control unit 3, a crystallization unit 1, and a temperature monitoring unit 2, all of which are connected to the control unit 3. This facilitates the control of experimental parameters, improves the experimental accuracy of the device, and reduces the operational burden on experimental personnel.

[0078] Furthermore, the present invention also provides an experimental method for simulating the solidification structure of a continuously cast billet. A target unit is selected, and the flow rate parameters of the cooling medium are set to recreate the change process of the cooling intensity of the surface of the continuously cast billet over time. The heat flux density of the solidification process is analyzed, and the simulated unit is obtained after solidification. The solidification structure of the simulated unit is then analyzed.

[0079] The experimental method for simulating the solidification structure of continuously cast billets of the present invention includes the following steps:

[0080] Step 1: Adjust the internal dimensions of the crystallizer in the simulation device.

[0081] Select the target element on the continuously cast billet in the field and determine the length L of the target element. u ', Width W u '、and height H u ';

[0082] When the target element is a continuously cast slab, the length L of the target element is... u = 100mm~420mm, width W u The width W' of the continuously cast slab is equal to that of the slab, and the height H is equal to that of the slab. u =50mm~650mm; A simulation unit is set inside the crystallization chamber, and the size of the simulation unit is controlled to be the same as the size of the target unit, that is, the length L of the simulation unit. u =L u ', width W u =W u ', height H u =H u '; Make the inner length of the crystallization cavity L = L u +80mm~150mm, so that the inner width of the crystallization cavity W=W u ; Make the inner cavity height H of the crystallization chamber = H u +150mm~200mm;

[0083] When the target element is a continuously cast square billet, the length L of the target element is... u 'The length L is equal to that of the continuously cast billet on site, and the width W' u The width W of the billet is equal to that of the continuously cast billet, and the height H is equal to that of the billet. u =50mm~650mm; A simulation unit is set inside the crystallization chamber, and the size of the simulation unit is controlled to be the same as the size of the target unit, that is, the length L of the simulation unit. u =L u ', width Wu =W u ', height H u =H u '; Make the inner length of the crystallization cavity L = L u Width W = W u Height H = H u +150mm~200mm;

[0084] Step 2: Set the cooling medium flow rate parameters and monitoring element parameters.

[0085] Using flow rate calculation formulas, the cooling medium flow rate for the simulation experiment was determined based on the water flow rate at each cooling stage of the continuously cast billet. Using cooling time calculation formulas for each cooling stage, the cooling time for the simulation experiment was determined based on the billet pulling speed, crystallizer height, and secondary cooling section length of the continuously cast billet. The water flow rate was controlled as Q0 from 0 to t0s after casting, Q1 from t0 to t1s, Q2 from t1 to t2s, Q3 from t2 to t3s, and so on, until t...t... n-1 ~t n The water flow rate of s is Q n The formulas for calculating the water flow rate at each cooling stage are as follows:

[0086] In the crystallizer stage, Q0 = k0 × Q0' × S / S'

[0087] In the second cooling phase, Q1 = k1 × Q1' 0.89 ×W / W'+40

[0088] Two cooling stages, Q2 = k1 × Q2' 0.89 ×W / W'+40

[0089] Two cooling stages, Q3 = k1 × Q3' 0.89 ×W / W'+40

[0090] ...

[0091] In the second cooling phase n, Q n =k1×Q n ' 0.89 ×W / W'+40

[0092] The formulas for calculating the cooling time of each cooling stage are as follows:

[0093] In the crystallizer stage, t0 = H0' / V'

[0094] Second cooling phase 1, t1=H1' / V'

[0095] Two cooling stages, t2 = H2' / V'

[0096] Two cooling stages, t3 = H3' / V'

[0097] ...

[0098] Second cooling n-stage, t n =H n ' / V'

[0099] Where Q0 is the cooling water flow rate during the simulated crystallizer stage, in L·min. -1 k0 is the correction coefficient for the crystallizer stage, ranging from 0.36 to 0.42; Q0' is the cooling water flow rate of the on-site continuous casting crystallizer, in L·min. -1 S and S' represent the cooling area of ​​the molten steel in the simulation experiment and the cooling area of ​​the molten steel in the on-site continuous casting mold, respectively, in meters (m²). 2 Q1, Q2, Q3...Q n These represent the cooling water flow rates for the simulated secondary cooling stage 1, secondary cooling stage 2, secondary cooling stage 3, ..., secondary cooling stage n, in L·min. -1 k1 is the correction coefficient for the secondary cooling stage, with a value ranging from 3.45 to 3.55; Q1', Q2', Q3'...Q n These are the cooling water flow rates for the first, second, third, ... nth stages of the continuous casting process, expressed in L·min. -1 t0 is the cooling time in the crystallizer stage of the simulated device, in seconds; H0' is the height of the on-site continuous casting crystallizer, in meters; V' is the on-site continuous casting billet pulling speed, in meters per second. -1 ;t1, t2, t3……t n These are the cooling times for the simulated cooling stages one through two, two through two, three through two…n, in seconds; H1', ​​H2', H3'…H… n 'These are the lengths of the first cooling stage, the second cooling stage, the third cooling stage, ... the nth cooling stage of the on-site continuous casting machine, in meters;

[0100] Cooling water with a flow rate of Q0 is introduced into the crystallization chamber;

[0101] Step 3: Simulate the solidification process of the continuously cast billet on site

[0102] The molten steel is smelted according to the steel grade composition requirements, and the composition and superheat of the molten steel are controlled to be consistent with the continuous casting billet on site. After the target tapping temperature is reached, the molten steel is poured into the inner cavity of the crystallization chamber.

[0103] Step 4: Analyze the heat flux density during the solidification process.

[0104] The heat flux density was calculated and recorded in real time according to the heat flux density formula to obtain the heat flux density curve. The influence of different process parameters on the surface heat flux density during the solidification process of the continuously cast billet was obtained by analyzing the heat flux density curve. The heat flux density formula is:

[0105]

[0106] Where q is the heat flux density (J·m -2 ·s -1 T1, T2, T3, T4, T5, and T6 represent the temperatures at different locations within the crystallization cavity, in °C; λ is the thermal conductivity of the crystallization cavity, in W·m. -1 ·℃ -1 x1, x2, x3, and x4 represent the temperature measurement distances at different locations within the crystallization chamber, respectively. These distances are the distances between the measurement location and the contact surfaces of the molten steel and the crystallization chamber, expressed in meters (m). c represents the specific heat of the cooling water, expressed in J·kg⁻¹. -1 ·℃ -1 ρ is the density of cooling water, in kg·m³. -3 ;

[0107] Step 5: Analyze the solidification structure of the simulation unit.

[0108] After the ingot has solidified, it is removed, cut, and a simulation unit is obtained. By detecting the macrostructure, microstructure, and element segregation of the simulation unit, the influence of different process parameters on the solidification structure of the continuously cast billet is obtained.

[0109] The experimental method for simulating the solidification structure of continuously cast billets of the present invention can accurately simulate the change process of heat flux density on the surface of the billet during continuous casting, so that the difference between the heat flux density of the simulated ingot and the heat flux density of the on-site continuously cast billet is less than 9%. The surface heat flux density, macrostructure, microstructure and segregation of the obtained billet are basically consistent with those of the continuously cast billet, which provides convenience for the study of solidification structure of continuously cast billets.

[0110] The experimental method for simulating the solidification structure of a continuously cast billet using the experimental apparatus of the present invention specifically includes the following steps:

[0111] Step 1: Adjust the internal dimensions of the crystallizer in the simulation device.

[0112] Select a target unit on the continuously cast billet and determine its length Lu', width Wu', and height Hu'. When the simulated object is a continuously cast slab, the target unit's length Lu' = 100mm to 420mm, its width Wu' is equal to the width W' of the continuously cast slab, and its height Hu' = 50mm to 650mm. Set a simulation unit inside the crystallization cavity of this invention, controlling the size of the simulation unit to be the same as the target unit's size, i.e., the simulation unit's length Lu = Lu', width Wu = Wu', and height Hu = Hu'. Adjust the spacing between the two insulation walls 102 so that the inner cavity length L of the crystallization cavity of this invention is Lu' + 80mm to 150mm, and adjust the spacing between the water-cooled walls 101 so that the inner cavity width W of the crystallization cavity of this invention is Wu. Adjust the bottom insulation. The height of wall 102 makes the inner cavity height H of the crystallization cavity of the present invention equal to Hu + 150mm to 200mm; when the simulated object is a continuously cast billet, the length Lu' of the target unit is equal to the length L' of the on-site continuously cast billet, the width Wu' is equal to the width W' of the on-site continuously cast billet, and the height Hu' is 50mm to 650mm; a simulation unit is set in the crystallization cavity of the present invention, and the size of the simulation unit is controlled to be the same as the size of the target unit, that is, the length Lu = Lu', the width Wu = Wu', and the height Hu = Hu' of the simulation unit; the spacing of the water-cooled walls 101 is adjusted so that the inner cavity length L = Lu and the width W = Wu of the crystallization cavity of the present invention is adjusted, and the height of the bottom insulation wall 102 is adjusted so that the inner cavity height H of the crystallization cavity of the present invention is Hu + 150mm to 200mm.

[0113] Step 2: Set water flow rate parameters and thermocouple parameters

[0114] Using the water flow calculation formula, the water flow rate of the simulation device is determined based on the water flow rate of each cooling stage of the continuously cast billet on site. Using the cooling time calculation formula for each cooling stage, the cooling time of the simulation device is determined based on the billet pulling speed, crystallizer height, and secondary cooling section length of the continuously cast billet on site. The power supply of control unit 3 is turned on, and the water flow rate control program is set on the dedicated control software built into control unit 3. The water flow rate from 0 to t0s after casting is controlled as Q0, the water flow rate from t0 to t1s is Q1, the water flow rate from t1 to t2s is Q2, the water flow rate from t2 to t3s is Q3, and so on. n-1 ~t n The water flow rate of s is Q n The formulas for calculating the water flow rate at each cooling stage are as follows:

[0115] In the crystallizer stage, Q0 = k0 × Q0' × S / S'

[0116] In the second cooling phase, Q1 = k1 × Q1' 0.89 ×W / W'+40

[0117] Two cooling stages, Q2 = k1 × Q2'0.89 ×W / W'+40

[0118] Two cooling stages, Q3 = k1 × Q3' 0.89 ×W / W'+40

[0119] ...

[0120] In the second cooling phase n, Q n =k1×Q n ' 0.89 ×W / W'+40

[0121] The formulas for calculating the cooling time of each cooling stage are as follows:

[0122] In the crystallizer stage, t0 = H0' / V'

[0123] Second cooling phase 1, t1=H1' / V'

[0124] Two cooling stages, t2 = H2' / V'

[0125] Two cooling stages, t3 = H3' / V'

[0126] ...

[0127] Second cooling n-stage, t n =H n ' / V'

[0128] Where Q0 is the cooling medium flow rate during the crystallizer stage of the simulation experiment, in L·min -1 k0 is the correction coefficient for the crystallizer stage, with a value ranging from 0.36 to 0.42; Q0' is the cooling medium flow rate of the on-site continuous casting crystallizer, in L·min. -1 S and S' represent the cooling area of ​​the molten steel in the simulation experiment and the cooling area of ​​the molten steel in the on-site continuous casting mold, respectively, in meters (m²). 2 Q1, Q2, Q3...Q n These represent the cooling medium flow rates for the simulated cooling stages one, two, three, ... n, in L·min. -1 k1 is the correction coefficient for the secondary cooling stage, with a value ranging from 3.45 to 3.55; Q1', Q2', Q3'...Q n These are the cooling medium flow rates for the first, second, third, ... nth stages of continuous casting, expressed in L·min. -1 t0 is the cooling time of the simulated crystallizer stage, in seconds; H0' is the height of the on-site continuous casting crystallizer, in meters; V' is the on-site continuous casting billet pulling speed, in meters per second. -1 ;t1, t2, t3……t nThese represent the cooling times for the simulated second-cooling-first stage, second-cooling-second stage, second-cooling-third stage, ..., second-cooling-nth stage, in seconds; H1', ​​H2', H3'...H n 'These are the lengths of the first, second, third, ... nth stages of the continuous casting machine, in meters.'

[0129] Input the temperature measurement distances of thermocouples C-1, C-2, C-3, and C-4 in the thermocouple group (C) in the dedicated control software built into the control unit 3; the temperature measurement distance is the distance between the thermocouple temperature measurement point and the hot surface of the copper plate 105.

[0130] It should be explained that thermocouples C-5 and C-6 are inserted into the inlet and outlet pressure equalization chambers 109, respectively. The temperature of the cooling water is uniform, and the measured temperature data is independent of the measurement distance. Therefore, it is not necessary to input the measurement distance in the dedicated control software built into the control unit 3. The thermocouple groups on the left and right sides are symmetrically distributed on both sides of the crystallizer cavity, and the measurement distance is the same. Therefore, it is only necessary to input the measurement distance of thermocouples C-1, C-2, C-3, and C-4.

[0131] Turn on the power to the water pump 110 and use the dedicated control software built into the control unit 3 to control the solenoid valve 111 to pre-feed cooling water with a flow rate of Q0 to the two water-cooled walls 101.

[0132] Turn on the power to the paperless recorder 202, so that the dedicated control software built into the control unit 3 and the paperless recorder 202 are in the pre-recording preparation state.

[0133] It should be emphasized that the water flow rate calculation for each cooling stage is based on the heat exchange area between the molten steel and the copper plate 105, the air gap thickness between the molten steel and the copper plate 105, and the influence of changes in continuous casting cooling conditions on heat transfer. This can accurately reproduce the change process of cooling intensity on the surface of the continuously cast billet over time.

[0134] In addition, pre-flushing with water is to remove gas from the crystallizer and improve experimental safety. Pre-flushing with water also avoids experimental errors caused by unstable water flow during the startup phase of water pump 110.

[0135] Step 3: Simulate the solidification process of the continuously cast billet on site

[0136] The molten steel is smelted according to the steel grade composition requirements. The composition and superheat of the molten steel are controlled to be consistent with the continuous casting billet on site. After the target tapping temperature is reached, the molten steel is poured into the inner cavity of the simulation device. At the same time, the pre-set water flow control program is run on the dedicated control software built into the control unit 3, and the real-time temperature data is recorded by the paperless recorder 202.

[0137] Step 4: Analyze the heat flux density during the solidification process.

[0138] The control unit 3 calculates and records the real-time heat flux density according to the heat flux density formula, obtaining a heat flux density curve. Analysis of the heat flux density curve reveals the influence of different process parameters on the surface heat flux density during the solidification process of the continuously cast billet. After solidification, the heat flux density curve can be compared with the heat flux density of the continuously cast billet on-site to confirm the accuracy of the simulation experiment. The heat flux density formula is:

[0139]

[0140] Where q is the heat flux density (J·m -2 ·s -1 T1, T2, T3, T4, T5, and T6 are the temperatures of thermocouples C-1, C-2, C-3, C-4, C-5, and C-6, respectively, in °C; λ is the thermal conductivity of copper, in W·m³. -1 ·℃ -1 x1, x2, x3, and x4 are the temperature measuring distances of thermocouples C-1, C-2, C-3, and C-4, respectively, in meters (m); c is the specific heat of the cooling water, in J·kg⁻¹. -1 ·℃ -1 ); ρ is the density of cooling water, (kg·m³) -3 ).

[0141] The heat flux density formula calculates the surface heat flux density of the ingot based on the temperatures of multiple temperature measuring points within the copper plate 105 and the cooling water temperature. This reduces measurement errors caused by uneven local temperatures, making the measured heat flux density more accurate.

[0142] Step 5: Analyze the solidification structure of the simulation unit.

[0143] After the ingot has solidified, it is removed, cut, and a simulation unit is obtained. By detecting the macrostructure, microstructure, and element segregation of the simulation unit, the influence of different process parameters on the solidification structure of the continuously cast billet is obtained.

[0144] In other specific embodiments of the present invention, the on-site continuous casting billet is a slab in the stable section of continuous casting production; when simulating continuous casting slab, the target unit is selected in the 1 / 6W' to 5 / 6W' region, thereby ensuring that the solidification structure of the target unit is not affected by the heat flow of the narrow face of the continuous casting billet.

[0145] In addition, the distance between the bottom surface of the simulation unit and the bottom surface of the crystallizer cavity of the simulation device is ≥50mm.

[0146] It should be emphasized here that in the ingots prepared by the present invention, only the solidification structure of the region where the simulation unit is located is the solidification structure of the continuous casting billet simulated by the present invention.

[0147] The experimental method for simulating the solidification structure of continuously cast billets according to the present invention will be further explained and illustrated below through specific embodiments.

[0148] Example 1

[0149] Simulate the solidification process of continuously cast billets

[0150] In the embodiments of this invention, molten steel was smelted in heats 1 to 4. Heats 1 and 2 were the implementation steel grade, 254SMO, prepared using the experimental apparatus and method of this invention for simulating the solidification structure of continuously cast billets. Heats 3 and 4 were the comparative steel grade, 254SMO, produced from an on-site industrial continuous casting machine. The implementation steel grade 1 simulated the continuous casting process parameters and solidification structure of the comparative steel grade 3, and the implementation steel grade 2 simulated the continuous casting process parameters and solidification structure of the comparative steel grade 4. The raw materials for the smelting of the implementation steel grade 1 were taken from the comparative steel grade 3, and the raw materials for the smelting of the implementation steel grade 2 were taken from the comparative steel grade 4.

[0151] The specific steps of the experiment are as follows:

[0152] Step 1: Adjust the internal dimensions of the crystallizer in the simulation device.

[0153] Select the target element on the continuously cast billet in the field and determine the length L of the target element. u ', Width W u '、and height H u When the simulated object is a continuously cast slab, the length L of the target element is... u = 100mm~420mm, width W u The width W' of the continuously cast slab is equal to that of the slab, and the height H is equal to that of the slab. u =50mm~650mm; In this specific embodiment, a simulation unit is set inside the crystallization cavity, and the size of the simulation unit is controlled to be the same as the size of the target unit, that is, the length L of the simulation unit is... u =L u ', width W u =W u ', height H u =H u '; Make the inner cavity length L of the crystallization cavity in this specific embodiment L = L u +80mm~150mm, so that the inner cavity width W of the crystallization cavity in this specific embodiment is W = W u The inner cavity height H of the crystallization cavity in this specific embodiment is H = H u +150mm~200mm; When the simulated object is a continuously cast square billet, the length L of the target unit is... u 'The length L is equal to that of the continuously cast billet on site, and the width W' u The width W of the billet is equal to that of the continuously cast billet, and the height H is equal to that of the billet. u=50mm~650mm; In this specific embodiment, a simulation unit is set inside the crystallization cavity, and the size of the simulation unit is controlled to be the same as the size of the target unit, that is, the length L of the simulation unit is... u =L u ', width W u =W u ', height H u =H u '; Make the inner cavity length L of the crystallization cavity in this specific embodiment L = L u Width W = W u Height H = H u +150mm~200mm;

[0154] Among them, L u '、L'、L u L represents the target unit length, the length of the on-site continuous casting slab or billet, the length of the simulated unit, and the inner cavity length of the crystallization chamber, respectively, in mm; W u '、W'、W u W, H, and W represent the target unit width, the width of the in-situ continuous casting plate or billet, the width of the simulated unit, and the inner cavity width of the crystallization chamber, respectively, in mm; u '、H u H and H represent the target unit height, the simulation unit height, and the inner cavity height of the crystallization cavity in this specific embodiment, respectively, in mm;

[0155] Table 1 Continuous casting production parameters and simulation device size parameters

[0156]

[0157] Step 2: Set water flow rate parameters and thermocouple parameters

[0158] The water flow rate of the simulation device is determined using the water flow rate calculation formula based on the water flow rate of each cooling stage in the on-site continuous casting process. The cooling time of the simulation device is determined using the cooling time calculation formula for each cooling stage based on the billet pulling speed, crystallizer height, and secondary cooling section length of the on-site continuous casting process. A water flow rate control program is set on the dedicated control software built into the control unit 4, controlling the water flow rate from 0 to t0s after casting as Q0, from t0 to t1s as Q1, from t1 to t2s as Q2, from t2 to t3s as Q3…t… n-1 ~t n The water flow rate of s is Q n The formulas for calculating the water flow rate at each cooling stage are as follows:

[0159] In the crystallizer stage, Q0 = k0 × Q0' × S / S'

[0160] In the second cooling phase, Q1 = k1 × Q1' 0.89×W / W'+40

[0161] Two cooling stages, Q2 = k1 × Q2' 0.89 ×W / W'+40

[0162] Two cooling stages, Q3 = k1 × Q3' 0.89 ×W / W'+40

[0163] ...

[0164] In the second cooling phase n, Q n =k1×Q n ' 0.89 ×W / W'+40

[0165] The formulas for calculating the cooling time of each cooling stage are as follows:

[0166] In the crystallizer stage, t0 = H0' / V'

[0167] Second cooling phase 1, t1=H1' / V'

[0168] Two cooling stages, t2 = H2' / V'

[0169] Two cooling stages, t3 = H3' / V'

[0170] ...

[0171] Second cooling n-stage, t n =H n ' / V'

[0172] Where Q0 is the cooling medium flow rate during the crystallizer stage of the simulation experiment, in L·min -1 k0 is the correction coefficient for the crystallizer stage, with a value ranging from 0.36 to 0.42; Q0' is the cooling medium flow rate of the on-site continuous casting crystallizer, in L·min. -1 S and S' represent the cooling area of ​​the molten steel in the simulation experiment and the cooling area of ​​the molten steel in the on-site continuous casting mold, respectively, in meters (m²). 2 Q1, Q2, Q3...Q n These represent the cooling medium flow rates for the simulated cooling stages one, two, three, ... n, in L·min. -1 k1 is the correction coefficient for the secondary cooling stage, with a value ranging from 3.45 to 3.55; Q1', Q2', Q3'...Q n These are the cooling medium flow rates for the first, second, third, ... nth stages of continuous casting, expressed in L·min. -1 t0 is the cooling time of the simulated crystallizer stage, in seconds; H0' is the height of the on-site continuous casting crystallizer, in meters; t1, t2, t3...tn These represent the cooling times for the simulated second-cooling-first stage, second-cooling-second stage, second-cooling-third stage, ..., second-cooling-nth stage, in seconds; H1', ​​H2', H3'...H n The lengths of the first, second, third, ... nth stages of the continuous casting machine are respectively, in meters; the water flow calculation parameters are shown in Table 2.

[0173] Table 2 Water Flow Parameters

[0174]

[0175] Input the temperature measurement distances of thermocouples C-1, C-2, C-3, and C-4 in the thermocouple group (C) into the dedicated control software built into the control unit 3; the temperature measurement distance is the distance from the thermocouple measuring point to the hot surface of the copper plate 105. The thermocouple arrangement parameters are shown in Table 3.

[0176] Table 3 Thermocouple Arrangement Parameters

[0177]

[0178] Turn on the power to the paperless recorder 202, so that the dedicated control software built into the control unit 3 and the paperless recorder 202 are in the pre-recording preparation state.

[0179] Turn on the power to the water pump 110 and use the dedicated control software built into the control unit 3 to control the solenoid valve 111 to pre-feed cooling water with a flow rate of Q0 to the two water-cooled walls 101.

[0180] It is important to emphasize that pre-flushing with water is to remove gas from the crystallizer and improve experimental safety. At the same time, pre-flushing with water can also avoid experimental errors caused by unstable water flow during the startup phase of water pump 110.

[0181] Step 3: Simulate the solidification process of the continuously cast billet in the field.

[0182] Several steel blocks were cut from the No. 3 comparative steel grade and used to smelt the No. 1 implementation steel grade. Several steel blocks were cut from the No. 4 comparative steel grade and used to smelt the No. 2 implementation steel grade. The molten steel was smelted, and the casting superheat of the No. 1 implementation steel grade was controlled to be the same as the on-site continuous casting superheat of the No. 3 comparative steel grade. The casting superheat of the No. 2 implementation steel grade was also controlled to be the same as the on-site continuous casting superheat of the No. 4 comparative steel grade. After reaching the target tapping temperature, the molten steel was poured into the inner cavity of the simulation device. Simultaneously, the dedicated control software on the control unit 3 was activated, and the experiment was conducted according to the pre-set water flow control program and cooling time control program to begin the simulation. Real-time temperature data was recorded using a paperless recorder 202.

[0183] Step 4: Analyze the heat flux density during the solidification process

[0184] The control unit 3 calculates and records the real-time heat flux density of steel grades #1 and #2 according to the heat flux density formula, obtaining heat flux density curves. After solidification, the heat flux density curves are compared with the heat flux density of the continuously cast billet in the field. The heat flux density formula is:

[0185]

[0186] Where q is the heat flux density (J·m -2 ·s -1 T1, T2, T3, T4, T5, and T6 are the temperatures of thermocouples C-1, C-2, C-3, C-4, C-5, and C-6, respectively, in °C; λ is the thermal conductivity of copper, in W·m³. -1 ·℃ -1 x1, x2, x3, and x4 are the temperature measuring distances of thermocouples C-1, C-2, C-3, and C-4, respectively, in meters (m); c is the specific heat of the cooling water, in J·kg⁻¹. -1 ·℃ -1 ); ρ is the density of cooling water, (kg·m³) -3 ).

[0187] Step 5: Analyze the solidification structure of the simulation unit.

[0188] After the solidification of steel grades 1 and 2, they were removed and a cross-section at half the height of the simulation unit was cut using wire cutting. The ingot outside the area of ​​the simulation unit was removed to obtain the cross-section of the simulation unit. At the same time, cross-sections of the in-situ continuous casting billets were cut from steel grades 3 and 4. The cross-sections were then ground and etched with aqua regia to obtain the macrostructure, and the analysis of Example 3 was performed. Using wire cutting, a 10mm × 10mm metallographic sample was cut from the edge to the center of the cross-section. The metallographic sample was ground, polished, and electrolytically polished with aqua regia to obtain the microstructure. The microstructure at the location of the simulation unit was analyzed in Example 4. The cross-sections were analyzed using chemical analysis methods in Example 5.

[0189] Heat flux density detection

[0190] Macroscopic microstructure photographs obtained in Example 1 were taken using a digital camera. The proportions of equiaxed and columnar crystals in the macroscopic microstructure were statistically analyzed using IPP 6.0 software. The results are as follows: Figure 6 As shown, the equiaxed crystal ratios are almost identical for steel grade 1 and steel grade 3 (comparative), and almost identical for steel grade 2 and steel grade 4 (comparative). This demonstrates that the thermal simulation device and method of this invention are highly accurate and can accurately reflect the influence of process parameter changes on the macrostructure.

[0191] Microstructure detection

[0192] The microstructure obtained in Example 1 was photographed using metallographic microscopy, and the central secondary dendrite spacing was calculated using IPP 6.0 software. Figure 7 As shown, the variation trend of the secondary dendrite spacing of steel grade 1 is almost the same as that of the comparative steel grade 3; the variation trend of the secondary dendrite spacing of steel grade 2 is almost the same as that of the comparative steel grade 4. These results indicate that the ingots obtained using the apparatus and method of this invention have a microstructure almost identical to those of continuously cast billets, accurately reflecting the influence of process parameter variations on the microstructure.

[0193] Mo element detection

[0194] The Mo content from the edge to the center of the cross section in Example 1 was measured using chemical analysis, such as... Figure 8 As shown, the Mo content at the center of steel grade 1 and the comparative steel grade 3 are almost the same, and the Mo content at the center of steel grade 2 and the comparative steel grade 4 are almost the same. This indicates that the simulation device and method of the present invention can accurately simulate the Mo element distribution of the continuously cast billet after the steel strip 5 is fed in. The above results show that the ingot obtained using the device and method of the present invention has an almost identical compositional distribution to the continuously cast billet, and can accurately reflect the influence of process parameter changes on segregation.

[0195] For continuously cast slabs, heat transfer mainly occurs in the width direction, while the heat transfer conditions inside the slab in the width and height directions are approximately adiabatic. Therefore, based on the heat transfer characteristics of the slab, this invention selects a small-sized target unit to represent the continuously cast slab, and sets up simulation units of the same size in the simulation device. The width of the crystallizer in the simulation device is controlled to be the same as the width of the simulation unit, and cooling is applied through copper plate 105, so that the heat transfer conditions of the simulation unit in the width direction are the same as those of the target unit of the continuously cast slab in the field; the simulation unit is insulated in the width and height directions using refractory bricks 107 and insulation plates 108, so that the heat transfer conditions of the simulation unit in the width and height directions are approximately adiabatic, similar to the target unit slab of the continuously cast slab. For continuously cast square billets, heat transfer mainly occurs in the length and width directions. Therefore, based on the heat transfer characteristics of square billets, this invention selects a target unit with the same cross-sectional dimensions as the square billet to represent the continuously cast square billet, and sets up simulation units of the same size in the simulation device. Cooling is applied through copper plate 105 to make the heat transfer conditions of the simulated unit in the length and width directions the same as those of the target unit of the continuously cast billet in the field. At the same time, the present invention combines heat transfer calculations, taking into account the heat exchange area between the molten steel and copper plate 105, the air gap thickness between the molten steel and copper plate 105, and the influence of changes in continuous casting cooling conditions on heat transfer, and establishes the water flow calculation formula and cooling time calculation formula of the simulation device to accurately reproduce the change process of cooling intensity on the surface of the continuously cast billet over time.

[0196] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. An experimental apparatus for simulating the solidification structure of continuously cast billets, characterized in that, Comprise: Crystallization unit, the crystallization unit includes water-cooled wall and base; When simulating continuous casting slab, the crystallization unit further comprises heat preservation wall, the number of the water-cooled wall and the heat preservation wall is two groups, two groups of the water-cooled wall are arranged in parallel, and the water-cooled wall is arranged parallel to the larger area side of the simulated continuous casting slab, two groups of the heat preservation wall are arranged in parallel and the heat preservation wall is perpendicular to the water-cooled wall, the base is located at the bottom of the water-cooled wall and the heat preservation wall, and the water-cooled wall, the heat preservation wall and the base form a crystallization cavity capable of containing melt; When simulating continuous casting billet, the number of the water-cooled wall is four groups, the adjacent water-cooled wall is perpendicular to each other, the base is located at the bottom of the water-cooled wall structure, and the water-cooled wall and the base form a crystallization cavity capable of containing melt; The water-cooled wall is provided with a cooling channel, the cooling channel is communicated with a cooling medium source, and the heat preservation layer is arranged on the side close to the crystallization cavity of the heat preservation wall and the base; Temperature monitoring unit, the temperature monitoring unit comprises a test element, and the test element can monitor the temperature of the water-cooled wall and the cooling medium in the cooling channel; The water-cooled wall comprises a copper plate and a water jacket, the copper plate is provided with a U-shaped groove, the copper plate is connected with the water jacket, the water jacket and the U-shaped groove form the cooling channel, the heat preservation layer comprises firebrick and heat preservation plate, and the copper plate and the firebrick form the inner wall of the crystallization cavity; The cooling channel is parallel to the height direction of the crystallization cavity, the number of the cooling channel is multiple, and the multiple cooling channels are arranged at equal intervals; Multiple cooling channels are communicated with the cooling medium source, and an equalizing chamber is arranged between the cooling channel and the cooling medium source, and a valve and a water pump are further arranged between the cooling channel and the cooling medium source; When simulating continuous casting slab, the distance between the two heat preservation walls is the length of the crystallization cavity, the distance between the two water-cooled walls is the width of the crystallization cavity, and the distance between the top of the water-cooled wall and the top of the base is the height of the crystallization cavity; When simulating continuous casting billet, the maximum distance between the two oppositely arranged water-cooled walls is the length of the crystallization cavity, the minimum distance between the two oppositely arranged water-cooled walls is the width of the crystallization cavity, and the distance between the top of the water-cooled wall and the top of the base is the height of the crystallization cavity; The number of the heat preservation layer is multiple, the heat preservation layer comprises firebrick and heat preservation plate, and adjacent heat preservation layers are detachably connected; The experimental device for simulating continuous casting slab solidification structure is used to carry out the experimental method for simulating continuous casting slab solidification structure, which comprises the following steps: selecting a target unit, setting a cooling medium flow parameter to restore the change process of the surface cooling intensity of the continuous casting slab with time, analyzing the heat flow density of the solidification process, obtaining a simulation unit after the solidification is completed, and analyzing the solidification structure of the simulation unit. Specifically, the following steps are included: Step one, adjusting the size of the crystallizer cavity of the simulation device selecting a target cell on a strand u width W u and height H u ; When the target unit is a continuously cast slab, the length L of the target unit is... u = 100mm~420mm, width W u The width W' of the continuously cast slab is equal to that of the slab, and the height H is equal to that of the slab. u =50mm~650mm; A simulation unit is set inside the crystallization chamber, and the size of the simulation unit is controlled to be the same as the size of the target unit, that is, the length L of the simulation unit is... u =L u ', width W u =W u ', height H u =H u '; Make the inner length of the crystallization cavity L = L u +80mm~150mm, so that the inner width W of the crystallization cavity is W=W u The inner cavity height H of the crystallization cavity is made equal to H. u +150mm~200mm; When the target unit is a continuously cast square billet, the length L of the target unit is... u 'The length L is equal to that of the continuously cast billet on site, and the width W' u The width W of the billet is equal to that of the continuously cast billet, and the height H is equal to that of the billet. u =50mm~650mm; A simulation unit is set inside the crystallization chamber, and the size of the simulation unit is controlled to be the same as the size of the target unit, that is, the length L of the simulation unit is... u =L u ', width W u =W u ', height H u =H u '; Make the inner length of the crystallization cavity L = L u Width W = W u Height H = H u +150mm~200mm; Step two, setting the cooling medium flow parameter and the monitoring element parameter The cooling medium flow of the simulation experiment is determined according to the water flow of each cooling stage of the on-site continuous casting blank by using a flow calculation formula; the cooling time of each cooling stage is calculated according to the casting speed, the mold height and the length of the secondary cooling section of the on-site continuous casting blank; the water flow from 0 to t0s after the end of casting is Q0, the water flow from t0 to t1s is Q1, the water flow from t1 to t2s is Q2, the water flow from t2 to t3s is Q3, and so on. n-1 n n The water flow calculation formula of each cooling stage is as follows:​​ Crystallizer stage, Q0=k0×Q0'×S / S' Two cooling stages, Q1 = k1 x Q1' 0.89 x W / W' + 40 Two cooling two stages, Q2 = k1 x Q2' 0.89 x W / W' + 40 Two cold three stages, Q3 = k1 x Q3' 0.89 x W / W' + 40 …… Two cooling n stage, Q n = k1 x Q n 0.89 x W / W' + 40​ The cooling time calculation formula of each cooling stage is as follows: Crystallizer stage, t0=H0' / V' Two cooling first stage, t1=H1' / V' Two cooling second stage, t2=H2' / V' Two cooling third stage, t3=H3' / V' …… Two cold n stages, t n = H n 'V' Q0' = k0 * S' * Q0 / S + Q1' + Q2' + Q3' + … + Qn' (2) -1 ; k0 is the crystallizer stage correction coefficient, the value range is 0.36-0.42; Q0' is the cooling medium flow of the field continuous casting crystallizer, the unit is L·min -1 ; S and S' are the molten steel cooling area of the simulation experiment and the field continuous casting crystallizer respectively, the unit is m 2 ; Q1, Q2, Q3 … Q n n stage are the cooling medium flow of the simulation experiment two cooling first stage, two cooling second stage, two cooling third stage … two cooling n stage respectively, the unit is L·min -1 ; k1 is the two cooling stage correction coefficient, the value range is 3.45-3.55; Q1', Q2', Q3' … Q n ' are the cooling medium flow of the field continuous casting two cooling first stage, two cooling second stage, two cooling third stage … two cooling n stage respectively, the unit is L·min -1 ; t0 is the cooling time of the simulation experiment crystallizer stage, the unit is s; H0' is the field continuous casting crystallizer height, the unit is m; V' is the field continuous casting billet casting speed, the unit is m·s -1 ; t1, t2, t3 … t n n stage are the cooling time of the simulation experiment two cooling first stage, two cooling second stage, two cooling third stage … two cooling n stage respectively, the unit is s; H1', H2', H3' … H n ' are the length of the field continuous casting machine two cooling first stage, two cooling second stage, two cooling third stage … two cooling n stage respectively, the unit is m; The cooling water with a flow rate of Q0 is introduced into the crystallization cavity; Step three, simulate the solidification process of the on-site continuous casting billet According to the steel grade composition requirements, the molten steel is smelted, the molten steel composition and superheat are controlled to be consistent with the on-site continuous casting billet, and after reaching the target tapping temperature, the molten steel is poured into the inner cavity of the crystallization cavity; Step four, analyze the heat flux density of the solidification process According to the heat flux density formula, the real-time heat flux density is calculated and recorded, and the heat flux density curve is obtained; by analyzing the heat flux density curve, the influence of different process parameters on the surface heat flux density of the continuous casting billet during the solidification process is obtained; the heat flux density formula is: wherein q is heat flux, (J·m -2 ·s -1 ), T1, T2, T3, T4, T5, T6 are temperatures at different positions of the crystallization cavity in sequence, in units of ℃; λ is the thermal conductivity of the crystallization cavity, in units of W·m -1 ·℃ -1 ; x1, x2, x3, x4 are the temperature measurement distances at different positions of the crystallization cavity, where the temperature measurement distance is the distance between the temperature measurement position and the contact surface between the molten steel and the crystallization cavity, in units of m; c is the specific heat of cooling water, in units of J·kg -1 ·℃ -1 ; ρ is the density of cooling water, in units of kg·m -3 ; Step five, analyze the solidification structure of the simulation unit After the ingot is solidified, it is taken out, cut, and the simulation unit is obtained; by detecting the macroscopic structure, microscopic structure, and element segregation of the simulation unit, the influence of different process parameters on the solidification structure of the continuous casting billet is obtained.

2. The experimental apparatus for simulating the solidification structure of a continuously cast slab according to claim 1, characterized by: The cross section of the cooling channel is rectangular, the length of the cross section of the cooling channel is 8mm-15mm, the width of the cross section of the cooling channel is 4mm-8mm, and the distance between adjacent cooling channels is 10mm-16mm.

3. The experimental device for simulating the solidification structure of a continuous casting billet according to claim 1, characterized in that: The length L of the crystallization cavity is 80mm-500mm, the width W of the crystallization cavity is 80mm-500mm, and the height H of the crystallization cavity is 200mm-800mm.

4. The experimental apparatus for simulating the solidification structure of a continuously cast slab according to claim 1, characterized by: The temperature monitoring unit further comprises a paperless recorder, the test element is connected to the paperless recorder, the test element is a thermocouple, and the number of test elements is multiple groups.

5. The experimental set-up for simulating the solidification structure of a continuously cast billet according to any one of claims 1 to 4, characterized in that: Further comprising a control unit, the crystallization unit and the temperature monitoring unit are connected to the control unit. Further comprising a control unit, the crystallization unit and the temperature monitoring unit are connected to the control unit.

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