Three-spray cooling system for horizontal continuous casting and control method

Abstract

The application relates to the technical field of horizontal continuous casting, in particular to a three-time spray cooling system and a control method for horizontal continuous casting, which specifically comprises the following steps: analyzing a heat exchange coefficient between cast iron profiles and cooling water, constructing a correlation between the heat exchange coefficient and turbidity of the cooling water, and calculating a heat exchange coefficient change amount at each moment; analyzing a cooling speed error at each moment based on a temperature before cooling and a temperature after cooling, combining the heat exchange coefficient change amount, and calculating a water quality change error at each moment; calculating a system change error at each moment based on a water spraying pressure, a water spraying flow and a change amount of the cooling speed; and then determining an adaptive feedback gain coefficient at each moment, and combining a self-disturbance control device to control the water spraying pressure; the application avoids the problem that a fixed feedback gain coefficient of a traditional self-disturbance control device leads to deviation of an actual cooling speed from an expected cooling speed, and then influences a cooling effect of the cast iron profiles, and improves stability of a cooling process of the cast iron profiles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of horizontal continuous casting, in particular to a three-time spray cooling system for horizontal continuous casting and a control method. BACKGROUND

[0002] Horizontal continuous casting is a casting method for continuously casting high-temperature molten metal into a profile or a blank. In this process, the molten metal flows out of the furnace and continuously solidifies into a solid product with a certain shape and size through specific devices and processes. The cast iron profile produced by the horizontal continuous casting process is divided into two categories: pearlite matrix and ferrite matrix. The performance of the cast iron profile with a pearlite matrix is higher. In order to change the matrix structure to pearlite during the horizontal continuous casting process, three-time spray cooling can be performed when the profile temperature is close to the eutectoid transformation, so that the matrix structure of the profile can be transformed into pearlite or a structure mainly composed of pearlite after non-equilibrium eutectoid transformation under a larger supercooling degree.

[0003] In order to increase the pearlite content in the matrix of the cast iron profile, an active disturbance rejection control (ADRC) can be used to control the spray cooling process parameters to achieve the desired cooling effect. The cooling water used for spray cooling in three-time spray cooling is usually recycled. During the recycling process, the evaporation of cooling will cause the concentration of minerals, thereby causing changes in water quality. Even if the circulating water is filtered in the recovery tank through a filter, the change in water pressure may disturb the water in the tank, thereby causing a sudden decrease in water quality. The decrease in water quality will reduce the heat transfer coefficient, thereby reducing the cooling effect. However, the traditional active disturbance rejection control uses a fixed feedback gain coefficient, which may cause a cooling out-of-control phenomenon when the water quality suddenly changes, because the fixed feedback gain coefficient cannot increase the control input in time to compensate, thereby causing the cooling speed to slow down and causing the pearlite content in the matrix structure of the cast iron profile to decrease. SUMMARY

[0004] In order to solve the above technical problems, the purpose of the present application is to provide a three-time spray cooling system for horizontal continuous casting and a control method. The technical solutions adopted are as follows:

[0005] In the first aspect, the embodiments of the present application provide a three-time spray cooling control method for horizontal continuous casting, which comprises the following steps:

[0006] Collecting the temperature before cooling and the temperature after cooling of the cast iron profile at each time, and the turbidity, water pressure and water flow of the cooling water at each time;

[0007] For the heat transfer coefficient between cooling water and cast iron profiles, the correlation between the heat transfer coefficient and the turbidity of cooling water is analyzed by measuring the heat transfer coefficient at various cooling water turbidity levels. Combined with the cooling water turbidity at each time point, the change in heat transfer coefficient at each time point is calculated. Based on the temperature before cooling and the temperature after cooling, the actual cooling rate at each time point is calculated, the cooling rate error at each time point is analyzed, and combined with the change in heat transfer coefficient, the water quality change error at each time point is calculated.

[0008] The system variation error at each moment is calculated based on the changes in water spray pressure, water spray flow rate and the actual cooling rate at adjacent moments.

[0009] The adaptive feedback gain coefficient at each moment is calculated based on the water quality change error and the system change error.

[0010] Based on the adaptive feedback gain coefficient and the correlation between the cooling rate of the cooling water and the spray pressure, the control law of the active disturbance rejection controller at the current moment is determined, and the spray pressure is controlled by the active disturbance rejection controller.

[0011] In one embodiment, the process of obtaining the change in heat transfer coefficient at each time point is as follows:

[0012] The linear fitting equation between heat transfer coefficient and turbidity was determined by measuring the heat transfer coefficient when the cooling water was at various turbidity levels.

[0013] Let the change in heat transfer coefficient at time t be denoted as , The expression is: In the formula, k is the slope of the linear fitting equation. Let t be the turbidity of the cooling water at time t.

[0014] In one embodiment, the process of obtaining the cooling rate error at each moment is as follows:

[0015] Calculate the difference between the temperature before cooling and the temperature after cooling at each moment, and take the ratio between the difference and the cooling time of the cast iron profile as the actual cooling rate of the cast iron profile at each moment; take the absolute value of the difference between the actual cooling rate and the preset expected cooling rate as the cooling rate error at each moment.

[0016] In one embodiment, the process of obtaining the water quality change error at each time point is as follows:

[0017] By combining the energy conservation equation and the convective heat transfer formula, the relationship between the cooling rate v and the heat transfer coefficient h is obtained. Based on this relationship, the change in cooling rate when the heat transfer coefficient changes by a unit amount is determined. The change in cooling rate when the heat transfer coefficient changes by a unit amount at time t is denoted as... ;based on The heat exchange coefficient variation quantity and the cooling speed error calculate the water quality variation error at each time.

[0018] In one embodiment, the expression of the water quality variation error is:

[0019] In the formula, is the water quality variation error at time t; represents the heat exchange coefficient variation quantity at time t; represents the cooling speed error at time t.

[0020] In one embodiment, the expression of the system variation error at each time is:

[0021] In the formula, represents the system variation error at time t, 、 and respectively represent the cooling speed variation quantity, the water spraying pressure variation quantity and the water spraying flow variation quantity between time t and time t-1.

[0022] In one embodiment, the expression of the adaptive feedback gain coefficient at each time is:

[0023] In the formula, represents the adaptive feedback gain coefficient at time t+1, represents the adaptive feedback gain coefficient at time t, represents the water quality variation error at time t, represents the system variation error at time t, represents a normalization function.

[0024] In one embodiment, the water spraying pressure control is performed in combination with the active disturbance rejection controller based on the adaptive feedback gain coefficient, specifically:

[0025] A linear fitting equation between the water spraying pressure and the cooling speed is determined by the cooling speed corresponding to various water spraying pressures under the current state, and is denoted as a first fitting equation; a control law at the current time is calculated based on the slope and the intercept of the first fitting equation, the error between the current cooling speed and the expected cooling speed, and the adaptive feedback gain coefficient at the next time calculated based on the data collected at the current time;

[0026] The heat conductivity coefficient of the cast iron profile, the initial heat exchange coefficient, and various parameters of the initial time of the cooling water are taken as initial inputs of the active disturbance rejection controller, wherein the control law of the current time is taken as the control law of the active disturbance rejection controller, and a control signal for adjusting the water spraying pressure is output; the opening of the valve is controlled by the pressure regulating valve based on the control signal, and the water spraying pressure is adjusted.

[0027] In one embodiment, the expression of the control law of the current time is as follows:

[0028] , wherein, and are the slope and the intercept of the first fitting equation respectively, represents the expected cooling speed; represents the error between the current cooling speed and the expected cooling speed; is the derivative of ; is the adaptive feedback gain coefficient of the next time calculated based on the data collected at the current time; represents the preset differential gain of the active disturbance rejection control algorithm, is the unknown disturbance in the observer of the active disturbance rejection controller.

[0029] In a second aspect, the embodiments of the present application also provide a three-time spraying cooling system for horizontal continuous casting, which comprises a memory, a processor, and a computer program stored in the memory and running on the processor, and the processor implements the steps of the method according to any one of the above embodiments when executing the computer program.

[0030] The embodiments of the present application have at least the following beneficial effects:

[0031] The present application calculates the change amount of the heat exchange coefficient by the change of the turbidity in the cooling water, obtains the theoretical cooling speed by combining the heat balance formula and the convection heat transfer formula, and obtains the change amount of the cooling speed when the unit amount of the heat exchange coefficient changes by taking the partial derivative of the heat exchange coefficient, and then calculates the water quality change error in combination with the actual cooling speed error; considering that the water quality change also affects the water spraying pressure and the water spraying flow, the system change error is calculated; further, the adaptive feedback gain coefficient is obtained, and the water spraying pressure is controlled based on the adaptive feedback gain coefficient in combination with the active disturbance rejection controller. The problem that the actual cooling speed deviates from the expected cooling speed caused by the use of the fixed feedback gain coefficient in the traditional active disturbance rejection control, thereby affecting the cooling effect, is avoided, and the stability of the cooling process is improved. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0033] Figure 1 A step flow chart of a three-time spray cooling control method for horizontal continuous casting provided by an embodiment of the present application is shown in

[0034] Figure 2 A schematic diagram of the acquisition process of the cooling speed error at each time is shown in DETAILED DESCRIPTION

[0035] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined purpose of the application, the specific embodiments, structures, features and effects of the three-time spray cooling system and control method for horizontal continuous casting according to the present application are described in detail as follows in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0037] The specific scheme of the three-time spray cooling system and control method for horizontal continuous casting provided by the present application is described in detail below in combination with the accompanying drawings.

[0038] Please refer to Figure 1 A step flow chart of a three-time spray cooling control method for horizontal continuous casting provided by an embodiment of the present application is shown in the figure, and the method comprises the following steps:

[0039] In step S1, the temperature before cooling and the temperature after cooling of the cast iron profile at each time, and the turbidity, water pressure and water flow of the cooling water at each time are collected.

[0040] The three-time spray cooling device comprises an inlet pipe, three square water tanks and a water recovery tank. The cast iron profile passes through the middle of the three square water tanks, and each square water tank has four spray heads surrounding the cast iron profile for spray cooling.

[0041] A pressure regulating valve is arranged at the inlet pipe to regulate the water pressure of the square water tank. Turbidity sensor, temperature sensor, flow sensor and pressure sensor are arranged respectively at 2cm behind the pressure regulating valve to measure the turbidity, temperature, flow and pressure of the cooling water.

[0042] A temperature sensor 1 is arranged on the support of the first square water tank and a temperature sensor 2 is arranged on the support of the third square water tank. The temperature sensor 1 and the temperature sensor 2 are used to measure the temperature before cooling and the temperature after cooling of the cast iron profile respectively.

[0043] For the data collection of each sensor, the data collection frequency of each sensor is set to 10Hz in the embodiment of the present application. As other embodiments of the present application, the implementer can set the data collection frequency according to the actual situation. All collected data is cleaned to remove outliers, and the cleaned data is supplemented with a data interpolation algorithm. The data cleaning and data interpolation algorithm are both known technologies, and the specific process will not be described again.

[0044] In step S2, for the heat exchange coefficient between the cooling water and the cast iron profile, the heat exchange coefficient under each cooling water turbidity is measured, the correlation between the heat exchange coefficient and the cooling water turbidity is analyzed, the heat exchange coefficient change at each time is calculated combined with the cooling water turbidity at each time, the actual cooling speed at each time is calculated based on the cooling before temperature and the cooling after temperature, the cooling speed error at each time is analyzed, and the water quality change error at each time is calculated combined with the heat exchange coefficient change.

[0045] The cast iron profile with pearlite matrix has higher mechanical properties. In order to make the cast iron profile have higher pearlite content, three times of water spray cooling can be carried out when the profile approaches the eutectoid transformation temperature, causing a larger cooling speed, so that the matrix structure of the profile becomes pearlite or mainly pearlite after non-equilibrium eutectoid transformation under a larger undercooling degree.

[0046] In the horizontal continuous casting process, the cooling speed has a key influence on the formation of pearlite. When the cooling speed is too fast, the diffusion of carbon atoms cannot be fully carried out, in which case the austenite may be transformed into non-pearlite structure such as bainite or martensite. When the cooling speed is too slow, the residence time is too long at the high temperature stage, and the carbon atoms have enough time to diffuse, which may lead to an increase in the amount of proeutectoid ferrite. With the precipitation of proeutectoid ferrite, the carbon content in the austenite increases relatively, and when the eutectoid transformation occurs, the amount of pearlite formed will decrease.

[0047] The water spraying pressure is a key factor affecting the cooling speed. By controlling the water spraying pressure, the heat transfer intensity between the cooling water and the cast blank can be adjusted, and thus the cooling speed can be controlled. Therefore, using the active disturbance rejection control algorithm to control the water spraying pressure to keep it at a suitable value can control the cooling speed.

[0048] Since the cooling water is recycled, the cooling water after spray cooling will be evaporated to cause the concentration of minerals to change the water quality. When the content of suspended solids in the cooling water is high, i.e., the water quality is poor, the heat transfer coefficient will decrease. If the water spraying pressure is unchanged, the cooling speed will decrease. Moreover, the suspended solids in the cooling water can block the spray head, which reduces the water flow and causes the cooling speed to decrease.

[0049] Therefore, the influence of the change in water quality on the pearlite content in the cast iron profile base body needs to be considered. The traditional active disturbance rejection control algorithm uses a fixed feedback gain coefficient, which cannot respond in time when the water quality suddenly changes, which can cause the cooling speed to deviate from the expected cooling speed and cause the pearlite content to decrease. Therefore, by adjusting the feedback gain coefficient, the cooling speed can be quickly adjusted to keep it near the expected cooling speed when the water quality changes.

[0050] In the active disturbance rejection control algorithm, there are two feedback gain coefficients, which are and , wherein mainly acts on the proportional link in the algorithm, which directly adjusts the control input according to the error size, and the adjustment effect is proportional to the error size. The greater the feedback gain coefficient , the greater the change range of the water spraying pressure, i.e., the faster the cooling speed is adjusted when the water quality changes, so that the cooling speed quickly approaches the expected cooling speed. On the contrary, the smaller the feedback gain coefficient , the smaller the change range of the water spraying pressure, and when the water quality changes to cause the cooling speed error, the adjustment of the water spraying pressure is relatively moderate to avoid excessive adjustment to cause the cooling speed to frequently fluctuate near the ideal value, thereby keeping the system stable.

[0051] (1) The heat transfer coefficient refers to the heat transferred through a unit area per unit time per unit temperature difference, which is a physical quantity for measuring the difficulty of heat transfer between two different temperature objects. In the embodiments of the present application, the two different temperature objects refer to the cooling water and the cast iron profile. When the cooling water contains a large amount of mineral ions, the evaporation will form suspended solids and scale, which increases the thermal resistance of heat transfer, making it more difficult for heat to transfer from the cast iron profile to the cooling water, thereby reducing the heat transfer coefficient. When the turbidity of the cooling water is 0, the heat transfer coefficient between the cooling water and the cast iron profile is , which is denoted as the initial heat transfer coefficient. The acquisition method of the initial heat transfer coefficient is a known technology, and the specific process is not described herein.

[0052] To analyze the relationship between the turbidity of cooling water and the heat exchange coefficient, the expression of the relationship between the heat exchange coefficient and the turbidity is recorded as: wherein h is the current heat exchange coefficient, is the initial heat exchange coefficient, k is the relationship coefficient, is the turbidity of the current cooling water.

[0053] For the relationship coefficient k, which is a coefficient representing the degree of influence of turbidity on the heat exchange coefficient, the corresponding heat exchange coefficient of the water sample with different turbidity is measured, and then the fitting equation is obtained by linear fitting of the measurement results, so that the relationship coefficient k is obtained according to the slope of the fitting equation. In the embodiment of the present application, the value of the relationship coefficient k is . The method for obtaining the fitting equation is a known technology, and the specific process will not be described again.

[0054] Further, the heat exchange coefficient change amount at each time is calculated according to the change of the impurity content in the cooling water at each time, which represents the change of the heat exchange capacity, and the expression is:

[0055]

[0056] wherein represents the heat exchange coefficient change amount at time t; k represents the relationship coefficient; represents the turbidity of the cooling water at time t.

[0057] The smaller the value of the heat exchange coefficient change amount, the lower the turbidity of the cooling water at this time, that is, the larger the heat exchange coefficient, and then the heat exchange capacity of the cooling water in the cooling system at this time is stronger. It may be that the new cooling water is added to the water supply tank, resulting in the reduction of suspended solids in the cooling water and the improvement of water quality. At this time, the feedback gain coefficient should be reduced to reduce the change range of the water spraying pressure, so as to be closer to the expected cooling speed and avoid frequent fluctuations of the cooling speed. On the contrary, it means that the water quality is deteriorated, that is, the feedback gain coefficient should be increased to quickly adjust the water spraying pressure and avoid slow cooling speed.

[0058] (2) To analyze the error caused by the change of water quality, the expected cooling speed in the embodiment of the present application is , as other embodiments of the present application, the implementer can set the expected cooling speed according to the actual situation; and for the actual cooling speed, the temperature of the cast iron profile before and after spraying can be calculated according to the temperature measured by the temperature sensor, that is:

[0059] The time taken by the cast iron profile to be pulled from the temperature sensor 1 to the temperature sensor 2 is recorded as the cooling time ; then, taking t time as an example, the temperature of temperature sensor 1 at t time is collected, which is recorded as the pre-cooling temperature at t time; the temperature of temperature sensor 2 at t time is collected, which is recorded as the post-cooling temperature at t time; the difference between the pre-cooling temperature and the post-cooling temperature at t time is calculated, and the ratio of the difference to the cooling time is taken as the actual cooling speed of the cast iron profile at t time.

[0060] Further, the cooling speed error at t time is the absolute value of the difference between the expected cooling speed and the actual cooling speed of the cast iron profile at the time.

[0061] The greater the cooling speed error at t time, the more inappropriate the cooling speed at the time, and the faster the water quality change, i.e. the feedback gain coefficient should be increased to respond faster; on the contrary, the smaller the cooling speed error at t time, the closer the cooling speed at the time to the expected cooling speed, i.e. the feedback gain coefficient should be reduced to reduce the change range of the water spraying pressure and maintain the stability of the cooling process.

[0062] (3) Since the change of the heat transfer coefficient will directly affect the cooling speed, and the error between the cooling speed and the expected cooling speed is calculated from the data measured by the sensor, which contains the error of the sensor and the error caused by other reasons, if it is directly used, it may lead to a large estimated error. In order to determine the influence of water quality change, the water quality change error at each time can be calculated according to the heat transfer coefficient change and the cooling speed error, and the expression is:

[0063]

[0064] In the formula, represents the water quality change error at t time; represents the heat transfer coefficient change at t time; represents the cooling speed error at t time; represents the change of the cooling speed when the heat transfer coefficient changes by a unit amount at t time, which quantifies the influence of the heat transfer coefficient change at the time on the cooling speed. Wherein, The process of obtaining is as follows:

[0065] First, the cooling speed is obtained, and the relationship expression between the cooling speed and the heat transfer coefficient h is as follows: based on the principle of heat balance, the heat released by the cast iron profile in a unit time is equal to the heat absorbed by the cooling water, which is recorded as , and the heat absorbed by the cooling water is recorded as , wherein, can be calculated by the formula = , and according to the convective heat transfer formula, , the relationship expression of the theoretical cooling speed v and the heat exchange coefficient h can be obtained. Then, the partial derivative of h is calculated to obtain the calculation expression of the partial derivative , wherein the formula for calculating the heat released by the cast iron profile and the formula for calculating the heat absorbed by the cooling water are known, and in the formula, , the density of the cast iron profile is 7200 in the embodiment; V represents the volume of the cast iron profile in contact with water; , the specific heat capacity of the cast iron profile is 500 in the embodiment; A represents the surface area of the cast iron profile in contact with water; , the surface temperature of the cast iron profile is the average of the temperature of the current temperature sensor 1 and the temperature of the temperature sensor 2 in the embodiment; , the temperature of the current cooling water, i.e. the water spraying temperature. The values of the above parameters at the current time are brought into the calculation expression of the partial derivative , and the calculation result represents the change amount of the cooling speed per unit change of the heat exchange coefficient. The heat balance principle and the formula for convective heat exchange are known technologies, and the specific process is not described herein.

[0066] By multiplying the change amount of the heat exchange coefficient and the partial derivative of the cooling speed with respect to the heat exchange coefficient, the change amount of the cooling speed caused by the change of the heat exchange coefficient can be obtained, and the proportion of the error caused by the change of the heat exchange coefficient can be obtained by dividing the cooling speed error. The error caused by the change of the water quality can be regarded as the error caused by the change of the heat exchange coefficient.

[0067] The greater the water quality change error is, the greater the cooling speed error caused by the change of the water quality is, and the feedback gain coefficient should be increased to achieve the purpose of fast response; on the contrary, the smaller the part of the cooling speed error caused by the change of the water quality is, and the error may be caused by the sensor error or other reasons, i.e. the feedback gain coefficient should be reduced to maintain the stability of the cooling process.

[0068] In step S3, the system change error at each time is calculated based on the water spraying pressure, the water spraying flow and the change amount of the actual cooling speed at the adjacent time.

[0069] The water quality change error only considers the error caused by the change of the heat exchange coefficient caused by the change of the water quality, but the change of the water quality also affects the water spraying flow, because the suspended matter formed by the change of the water quality may block the water outlet of the nozzle to cause the water spraying flow to decrease in the same time, so that the cooling speed is slowed down and the error with the expected cooling speed occurs. In the case where the pressure regulating valve is not used to regulate the water spraying pressure, the decrease of the water spraying flow may cause the water spraying pressure in the square water bag to increase.

[0070] Therefore, the system change error except the error caused by the water quality change can be calculated according to the change of the water spraying flow and the water spraying pressure, and the expression is:

[0071]

[0072] In the expression, ΔQ(t) represents the water quality change error at the time t, and ΔQ(t) represents the system change error at the time t, , and respectively represent the actual cooling speed change amount, the water spraying pressure change amount and the water spraying flow change amount between the time t and the time t-1. The actual cooling speed change amount is the absolute value of the difference between the actual cooling speed at each time and the actual cooling speed at the time t-1. The water spraying pressure change amount and the water spraying flow change amount are calculated by using the same calculation method as the actual cooling speed change amount.

[0073] The system change error reflects the change of the control input, i.e. the change of the water spraying pressure and the water spraying flow. When the control input changes by one unit, the cooling speed changes by a certain degree. Therefore, when the control input changes due to the water quality change, the cooling speed also changes, and the feedback gain coefficient should be adjusted in time.

[0074] The greater the system change error, the greater the influence of the water quality change on the water spraying flow and the water spraying pressure, i.e. the feedback gain coefficient should be increased so that the controller can quickly respond and the water spraying pressure can be adjusted in time to make the cooling speed close to the expected cooling speed. On the contrary, the smaller the influence of the water quality change on the water spraying flow and the water spraying pressure, the smaller the feedback gain coefficient should be.

[0075] In step S4, the adaptive feedback gain coefficient at each time is calculated based on the water quality change error and the system change error.

[0076] The expected cooling speed in the embodiment is set according to the eutectoid temperature of the cast iron profile, and the actual cooling speed deviates from the ideal value due to the interference of the water quality change. The error between the actual cooling speed and the expected cooling speed reflects the deviation degree, and the purpose of the adaptive control is to reduce the error and make the actual cooling speed close to the expected cooling speed.

[0077] Therefore, the adaptive feedback gain coefficient at each time is calculated according to the water quality change error and the system change error at each time, and the expression is:

[0078]

[0079] In the expression, K(t+1) represents the adaptive feedback gain coefficient at the time t+1, K(t) represents the adaptive feedback gain coefficient at the time t, K(t) represents the adaptive feedback gain coefficient at the time t, This represents the error in water quality change at time t. This represents the system change error at time t. This represents the normalization function. Multiplying by 2 limits the adaptive adjustment range of the feedback gain coefficient. It should be noted that when t is 1, the initial feedback gain coefficient is used as the adaptive feedback gain coefficient at that moment. Preferably, in this embodiment, the initial feedback gain coefficient is set to 0.5; simultaneously, the product of the water quality change error and the system change error at that moment is set to 1. As other embodiments of this application, the implementer can set the product of the water quality change error and the system change error at that moment, as well as the initial feedback gain coefficient, according to actual conditions.

[0080] Step S5: Based on the adaptive feedback gain coefficient and the correlation between the cooling rate of the cooling water and the spray pressure, determine the control law of the active disturbance rejection controller at the current moment, and use the active disturbance rejection controller to control the spray pressure.

[0081] When using an active disturbance rejection controller to control the water spray pressure, the water spray pressure under the current state must first be determined. and cooling speed Specifically, in this embodiment, under the current spraying state, the cooling rate is measured at multiple preset spray pressures through experiments. All spray pressures and their corresponding measured cooling rates are used as inputs for least squares linear fitting. The resulting linear fitting equation is denoted as... ,in and These represent the slope and intercept of the linear fitting equation, respectively. The method for obtaining the linear fitting equation between water spray pressure and cooling rate, as well as the least squares linear fitting method, are well-known techniques, and their specific processes will not be elaborated upon here.

[0082] Subsequently, the thermal conductivity and initial heat transfer coefficient of the cast iron profile, as well as the initial spray pressure, initial spray temperature, initial spray flow rate, spray distance, and spray length of the cooling water, are used as the initial inputs to the controller. In this embodiment, the thermal conductivity of the cast iron profile is... The initial spray pressure, initial spray temperature, and initial spray flow rate of the cooling water can be measured by the sensor corresponding to the initial moment. The measurement method is a well-known technology, and the specific process will not be described in detail. The spray distance refers to the distance from the nozzle to the cast iron profile, and the spray length refers to the length of the cast iron profile covered by the spray range of the three square water jackets.

[0083] For the interference observer, an extended state observer is used, assuming... , Its state equation is , Where D represents unknown interference. , denotes the derivative of the state variable, , denotes the estimated value of the state variable, the initial estimated value and the initial disturbance value are 0, in the embodiment of the application, the estimated value is calculated by Euler method, , denotes the observer gain, preferably, in the embodiment, the value of is set to 100, and the value of is set to 20. As other embodiments of the application, the implementer can set the initial value of

[0084] State equation and is the derivative of the state variable, which describes the rate of change of the state variable with time. denotes the linear relationship part of the cooling speed based on the water injection pressure, embodies the influence of unknown disturbance on the rate of change of the cooling speed. and are the correction terms of the observer, wherein , are the observer gains, which play a role in adjusting the performance of the observer. is the error between the actual state and the estimated state, and the estimated value is continuously corrected through the error feedback, so that the observer can more accurately track the actual state.

[0085] It should be noted that for the calculation of the estimated value, the application only provides a calculation method, there are many existing methods for calculating the estimated value, and the implementer can also use other algorithms to calculate the estimated value, which is not specifically limited by the application.

[0086] Calculate the control law at the current time , the formula of which is , wherein denotes the expected cooling speed; denotes the error between the current cooling speed and the expected cooling speed; is the derivative of ; is the adaptive feedback gain coefficient at the next time calculated based on the data collected at the current time; denotes the derivative gain of the active disturbance rejection control algorithm. Preferably, in the embodiment of the application, the initial value of is set to 0.5, the initial value of is set to 0.1. As other embodiments of the application, the implementer can set the initial value of and the initial value of

[0087] according to actual conditions.Further, the control law at the current time is taken as the control law of the active disturbance rejection controller, the output of the active disturbance rejection controller is a control signal for adjusting the water spraying pressure, and then the control signal is sent to the actuator, the actuator controls the opening degree of the valve through the pressure regulating valve, so as to adjust the water spraying pressure.

[0088] The acquisition process of the cooling speed error at each time is shown in the schematic diagram as Figure 2

[0089] Based on the same inventive concept as the above method, the embodiments of the present application also provide a three-spray cooling system for horizontal continuous casting, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, and the processor implements the steps of any one of the above-mentioned methods for three-spray cooling control method for horizontal continuous casting when executing the computer program.

[0090] In summary, the embodiments of the present application provide a three-spray cooling control method for horizontal continuous casting, which calculates the change amount of the heat transfer coefficient by the change of the turbidity in the cooling water, obtains the theoretical cooling speed by combining the heat balance formula and the convective heat transfer formula, and then calculates the change amount of the cooling speed when the heat transfer coefficient changes by a unit amount by taking the partial derivative of the heat transfer coefficient, and then calculates the water quality change error by combining the actual cooling speed error; considering that the water quality change will also affect the water spraying pressure and the water spraying flow, the system change error is calculated again; further, the adaptive feedback gain coefficient is obtained, and the water spraying pressure is controlled based on the adaptive feedback gain coefficient and the active disturbance rejection controller. Avoid the problem that the actual cooling speed deviates from the expected cooling speed caused by the use of fixed feedback gain coefficient in traditional active disturbance rejection control, and improve the stability of the cooling process.

[0091] It should be noted that: the above-mentioned sequence of the embodiments of the present application is only for description, and does not represent the advantages and disadvantages of the embodiments. And the above-mentioned specific embodiments of the present application are described. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or may be advantageous.

[0092] Each embodiment in the present application is described in a progressive manner, and the same or similar parts of each embodiment can be referred to each other, and each embodiment mainly describes the difference from other embodiments.

[0093] The above-mentioned is only the preferred embodiment of the present application, and does not limit the present application, any modification, equivalent replacement, improvement, etc. made within the principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for controlling a tertiary spray cooling for horizontal continuous casting, characterized by, The method comprises the following steps: Collecting the temperature before cooling and the temperature after cooling of the cast iron profile at each time, and the turbidity, water spraying pressure and water spraying flow of the cooling water at each time; For the heat exchange coefficient between the cooling water and the cast iron profile, by measuring the heat exchange coefficient under each cooling water turbidity, analyzing the correlation between the heat exchange coefficient and the cooling water turbidity, combining the cooling water turbidity at each time, the heat exchange coefficient change amount at each time is calculated; based on the temperature before cooling and the temperature after cooling, the actual cooling speed at each time is calculated, the cooling speed error at each time is analyzed, the water quality change error at each time is calculated by combining the heat exchange coefficient change amount; Based on the change amount of the actual cooling speed, the system change error at each time is calculated; Based on the water quality change error and the system change error, the adaptive feedback gain coefficient at each time is calculated; Based on the adaptive feedback gain coefficient and the correlation between the cooling speed of the cooling water and the water spraying pressure, the control law of the current time self-disturbance control is determined, and the water spraying pressure control is performed by using the self-disturbance control; The acquisition process of the heat exchange coefficient change amount at each time is: The linear fitting equation between the heat exchange coefficient and the turbidity is determined by the heat exchange coefficient measured when the cooling water is at various turbidities; The heat exchange coefficient change amount at time t is denoted as , The expression of the heat exchange coefficient change amount is: , wherein k is the slope of the linear fitting equation, the turbidity of the cooling water at time t; The acquisition process of the water quality change error at each time is: The energy conservation equation and the convection heat exchange formula are combined to obtain a relationship expression of the cooling speed v and the heat exchange coefficient h. Based on the relationship expression, the change amount of the cooling speed when the heat exchange coefficient changes by a unit amount is determined, and the change amount of the cooling speed when the heat exchange coefficient changes by a unit amount at the time t is denoted as ; based on , the heat exchange coefficient change amount and the cooling speed error, the water quality change error at each time is calculated. The expression of the water quality change error is: wherein, is the water quality change error at time t; represents the heat exchange coefficient change amount at time t; represents the cooling speed error at time t; The expression of the system change error at each time is: wherein, denotes the system variation error at time t, , and denote the cooling speed variation, the water injection pressure variation and the water injection flow rate variation between time t and time t-1, respectively. The expression of the adaptive feedback gain coefficient at each time is: wherein, denotes the adaptive feedback gain coefficient at time t+1, denotes the adaptive feedback gain coefficient at time t, denotes the water quality variation error at time t, denotes the system variation error at time t, denotes a normalization function; Based on the adaptive feedback gain coefficient, the water spraying pressure control is performed by combining the self-disturbance control, specifically: The linear fitting equation between the water spraying pressure and the cooling speed is determined by the cooling speed corresponding to various water spraying pressures under the current state, which is recorded as the first fitting equation; based on the slope and intercept of the first fitting equation, combining the error between the current cooling speed and the expected cooling speed, and the adaptive feedback gain coefficient of the next time calculated based on the data collected at the current time, the control law of the current time is calculated; The heat conductivity coefficient of the cast iron profile, the initial heat exchange coefficient and various parameters of the cooling water at the initial time are taken as the initial input of the self-disturbance control, wherein the control law of the current time is taken as the control law of the self-disturbance control, and the output is the control signal for adjusting the water spraying pressure; based on the control signal, the opening of the valve is controlled by the pressure regulating valve to adjust the water spraying pressure; The expression of the control law of the current time is: , wherein and are the slope and the intercept of the first fitting equation, respectively, denotes the desired cooling speed; denotes the error between the current cooling speed and the desired cooling speed; is the derivative of ; is the adaptive feedback gain coefficient at the next time instant calculated based on the data collected at the current time instant; denotes the preset differential gain of the active disturbance rejection control algorithm, is the unknown disturbance in the observer of the active disturbance rejection controller, is the estimated value of .

2. The tertiary spray cooling control method for horizontal continuous casting according to claim 1, characterized by, The acquisition process of the cooling speed error at each time is: The difference between the temperature before cooling and the temperature after cooling at each time is calculated, and the ratio between the difference and the cooling time of the cast iron profile is taken as the actual cooling speed of the cast iron profile at each time; the absolute value of the difference between the actual cooling speed and the expected cooling speed is taken as the cooling speed error at each time.

3. A tertiary spray cooling system for horizontal continuous casting comprising a memory, a processor and a computer program stored in the memory and running on the processor, characterized in that, The processor executes the computer program to realize the steps of the method in any one of claims 1-2.

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