Method and system for predicting liquid nitrogen content of steel in VD refining process

Abstract

The invention provides a method and system for predicting the liquid nitrogen content of steel in the VD refining process. The method comprises the steps that technological parameters of the VD vacuum degassing process are obtained, and a nitrogen content prediction model is constructed to output a target nitrogen content prediction value according to the technological parameters. In the prediction model, a first calculation module is used for calculating an activity coefficient of a nitrogen element in molten steel, a second calculation module is used for calculating a dissolution equilibrium constant, a third calculation module is used for calculating a mass percentage of the nitrogen element in the molten steel when the dissolution equilibrium is reached, and a fourth calculation module is used for calculating a ratio of an interface reaction area to a molten pool volume. The correction module is used for acquiring a corrected mass transfer coefficient, and the fifth calculation module is used for calculating a target nitrogen content predicted value. Calculation is carried out by adopting the thermodynamic principle through the constructed prediction model, the nitrogen content in the molten steel in the vacuum degassing process can be predicted, the problem that the nitrogen content cannot be obtained in the degassing process is solved, the nitrogen content prediction value is calculated through the corrected mass transfer coefficient, and the accuracy of the calculation result can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of calculation of nitrogen content in molten steel, and in particular to a method and system for predicting nitrogen content in molten steel during a VD refining process. Background Art

[0002] VD (Vacuum Degassing) vacuum refining technology is a vacuum degassing process. This technology can not only effectively remove harmful gases such as hydrogen and oxygen from molten steel, but also has the comprehensive functions of desulfurization, fine-tuning alloy composition, uniform molten steel composition and temperature control. It is used to manufacture steels with extremely high performance requirements such as pipeline steel, heavy rail steel, and cord steel. However, due to the continuous improvement of steel quality requirements, especially in the production of specific steels with strict upper and lower limits on nitrogen content, VD refining technology still has many problems.

[0003] Due to the complex environment in the VD furnace, which involves high temperature, high pressure and a variety of physical and chemical reactions, and the limitations of detection methods, it is impossible to detect the nitrogen content of the steel liquid by sampling during the vacuum degassing process, and it is difficult to monitor in real time. Therefore, it mainly relies on manual experience to control the vacuum degree and degassing time. Since this process relies on manual judgment, the accuracy of the degassing process is low. And for steel types with upper and lower limits on nitrogen content, it is necessary to wait until the degassing process is over before sampling to determine the nitrogen content. At this time, if the nitrogen content is unqualified, it is necessary to re-evacuate or add nitrogen, which makes the operation cumbersome, time-consuming and labor-intensive, thereby reducing the overall efficiency of VD refining and reducing economic benefits. Summary of the invention

[0004] The present application provides a method and system for predicting nitrogen content in molten steel during a VD refining process, so as to solve the problem that the nitrogen content cannot be obtained during the vacuum degassing process.

[0005] The first aspect of the present application provides a method for predicting nitrogen content in liquid steel during a VD refining process, comprising:

[0006] Obtaining process parameters of the VD vacuum degassing process, wherein the process parameters include molten steel temperature, interaction coefficient, mass percentage of elements in the molten steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, bottom blowing gas type and bottom blowing gas flow rate per unit time; the interaction coefficient is the interaction coefficient of the elements in the molten steel to the nitrogen element;

[0007] A nitrogen content prediction model is constructed to output a predicted value of a target nitrogen content in the molten steel according to the process parameters; the prediction model comprises:

[0008] A first calculation module, used for calculating the activity coefficient of nitrogen in the molten steel according to the interaction coefficient and the mass percentage of the element in the molten steel;

[0009] A second calculation module is used to calculate the dissolution equilibrium constant of nitrogen in the molten steel according to the temperature of the molten steel;

[0010] a third calculation module, configured to calculate a first nitrogen content according to the partial pressure of nitrogen in the nitrogen bubbles, the activity coefficient and the dissolution equilibrium constant, wherein the first nitrogen content is a mass percentage of nitrogen when the nitrogen element reaches dissolution equilibrium in the molten steel;

[0011] a fourth calculation module, configured to calculate a first ratio according to the vacuum chamber pressure and the bottom blowing gas flow rate per unit time, wherein the first ratio is a ratio of an interface reaction area to a molten pool volume;

[0012] A correction module, used for correcting the model parameters of the prediction model according to the initial mass transfer coefficient to obtain a corrected mass transfer coefficient;

[0013] The fifth calculation module is used to calculate the second nitrogen content in the molten steel according to the first nitrogen content, the modified mass transfer coefficient, the bottom blowing gas type and the first ratio, and output the second nitrogen content as a predicted value of the target nitrogen content.

[0014] Optionally, the solubility equilibrium constant of nitrogen in molten steel can be calculated by the following formula:

[0015]

[0016] Among them, K N is the dissolution equilibrium constant, and T is the temperature of the molten steel.

[0017] Optionally, the first nitrogen content is calculated by the following formula:

[0018]

[0019] Where, [%N] eq is the first nitrogen content, K N is the solubility equilibrium constant, is the partial pressure of nitrogen in the nitrogen bubble, P θ is standard atmospheric pressure, f N is the activity coefficient.

[0020] Optionally, the first ratio is calculated by the following formula:

[0021]

[0022] Wherein, B is the first ratio, Q is the bottom blowing gas flow rate per unit time, P1 is the vacuum chamber pressure, and Δt is the time change.

[0023] Optionally, the step of correcting the model parameters of the prediction model according to the initial mass transfer coefficient to obtain a corrected mass transfer coefficient includes:

[0024] Obtaining an initial mass transfer coefficient, where the initial mass transfer coefficient is a continuous value within a preset range;

[0025] Dividing the initial mass transfer coefficient according to a preset step size to obtain a plurality of mass transfer coefficients;

[0026] Acquire historical data, wherein the historical data is the actual measured value of nitrogen content in the molten steel after the degassing process is completed;

[0027] Calculating a first nitrogen content prediction value according to the mass transfer coefficient, wherein the first nitrogen content prediction value is a prediction value of nitrogen content in the molten steel after the degassing process is completed;

[0028] Calculating a mean absolute error based on the historical data and the first nitrogen content prediction value;

[0029] The mass transfer coefficients are traversed to obtain the mass transfer coefficient corresponding to the minimum mean absolute error, and the mass transfer coefficient is output as the modified mass transfer coefficient.

[0030] Optionally, calculate the mean absolute error by:

[0031]

[0032] Among them, MAE is the mean absolute error, is the first nitrogen content prediction value, y i It is the actual measured value of nitrogen content in molten steel after the degassing process is completed.

[0033] Optionally, the bottom blowing gas includes nitrogen and argon, and the calculating the second nitrogen content in the molten steel according to the first nitrogen content, the modified mass transfer coefficient, the type of the bottom blowing gas and the first ratio includes:

[0034] When the bottom blowing gas is nitrogen, the second nitrogen content is calculated by the following formula:

[0035] [%N]2=[%N]1-η×A×B×([%N]1-[%N] eq )×Δt1;

[0036] When the bottom blowing gas is argon, the second nitrogen content is calculated by the following formula:

[0037] [%N]2=[%N]1-A×B×([%N]1-[%N] eq )×Δt1;

[0038] Wherein, [%N]2 is the second nitrogen content, [%N]1 is the predicted value of the nitrogen content in the molten steel at the initial moment of the preset time, η is a dimensionless number, A is the modified mass transfer coefficient, B is the first ratio, and Δt1 is the preset time.

[0039] Optionally, when the initial moment of the preset time period is the start moment of degassing, the predicted value of the nitrogen content in the molten steel is the actual measured value of the nitrogen content in the molten steel.

[0040] Optionally, the method further includes:

[0041] If the degassing process is not finished, continuing to calculate the dissolution equilibrium constant according to the molten steel temperature by the second calculation module;

[0042] Calculating the first nitrogen content according to the partial pressure of nitrogen in the nitrogen bubbles, the activity coefficient and the solubility equilibrium constant by the third calculation module;

[0043] Calculating the first ratio according to the vacuum chamber pressure and the bottom blowing gas flow rate per unit time by the fourth calculation module;

[0044] Calculating the second nitrogen content by the fifth calculation module according to the first nitrogen content, the modified mass transfer coefficient, the bottom blowing gas type and the first ratio;

[0045] Until the degassing process is completed, the second nitrogen content is output as the predicted value of the target nitrogen content.

[0046] The second aspect of the present application provides a system for predicting nitrogen content in liquid steel during a VD refining process, which is applied to the method described in the first aspect, and the system comprises:

[0047] Acquisition module: used to acquire the process parameters of the VD vacuum degassing process, the process parameters including molten steel temperature, interaction coefficient, mass percentage of elements in the molten steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, bottom blowing gas type and bottom blowing gas flow rate per unit time; the interaction coefficient is the interaction coefficient of the elements in the molten steel to the nitrogen element;

[0048] A first calculation module: used for calculating the activity coefficient of nitrogen in the molten steel according to the interaction coefficient and the mass percentage of the element in the molten steel;

[0049] A second calculation module: used for calculating the dissolution equilibrium constant of nitrogen in the molten steel according to the molten steel temperature;

[0050] A third calculation module: used to calculate a first nitrogen content according to the partial pressure of nitrogen in the nitrogen bubbles, the activity coefficient and the dissolution equilibrium constant, wherein the first nitrogen content is the mass percentage of nitrogen element when the dissolution equilibrium is reached in the molten steel;

[0051] A fourth calculation module: used to calculate a first ratio according to the vacuum chamber pressure and the bottom blowing gas flow rate per unit time, wherein the first ratio is a ratio of an interface reaction area to a molten pool volume;

[0052] Correction module: used for correcting the model parameters of the prediction model according to the initial mass transfer coefficient to obtain a corrected mass transfer coefficient;

[0053] The fifth calculation module is used to calculate the second nitrogen content in the molten steel according to the first nitrogen content, the modified mass transfer coefficient, the bottom blowing gas type and the first ratio, and output the second nitrogen content as a predicted value of the target nitrogen content.

[0054] The present application provides a method and system for predicting nitrogen content in molten steel during a VD refining process, the method comprising: obtaining process parameters of a VD vacuum degassing process, constructing a nitrogen content prediction model to output a target nitrogen content prediction value according to the process parameters. The first calculation module in the prediction model is used to calculate the activity coefficient of nitrogen in molten steel, the second calculation module is used to calculate the solubility equilibrium constant, the third calculation module is used to calculate the mass percentage of nitrogen when the nitrogen reaches solubility equilibrium in the molten steel, the fourth calculation module is used to calculate the ratio of the interface reaction area to the molten pool volume, the correction module is used to obtain the corrected mass transfer coefficient, and the fifth calculation module is used to calculate the target nitrogen content prediction value. The constructed prediction model uses thermodynamic principles for calculation, and the nitrogen content in the molten steel during the vacuum degassing process can be predicted, solving the problem that the nitrogen content cannot be obtained during the vacuum degassing process, and the nitrogen content prediction value is calculated by the corrected mass transfer coefficient, which can improve the accuracy of the calculation result. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0056] Figure 1 A schematic diagram of a method for predicting nitrogen content in liquid steel during a VD refining process provided in an embodiment of the present application;

[0057] Figure 2 A schematic flow chart of a method for obtaining a corrected mass transfer coefficient provided in an embodiment of the present application;

[0058] Figure 3 A schematic diagram of the prediction model workflow provided in the embodiment of the present application;

[0059] Figure 4 This is a schematic diagram of the structure of a system for predicting nitrogen content in liquid steel during a VD refining process provided in an embodiment of the present application. DETAILED DESCRIPTION

[0060] The following embodiments are described in detail, and examples thereof are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following embodiments do not represent all implementations consistent with the present application. They are only examples of systems and methods consistent with some aspects of the present application as detailed in the claims.

[0061] Due to the complex environment in the VD furnace, which involves high temperature, high pressure and a variety of physical and chemical reactions, it is impossible to detect the nitrogen content of the steel liquid by sampling during the vacuum degassing process, and it is difficult to monitor in real time. Therefore, the vacuum degree and degassing time are mainly controlled by manual experience. Since this process relies on manual judgment, the accuracy of the degassing process is low. And for steel types with upper and lower limits of nitrogen content, it is necessary to wait until the degassing process is over before sampling to determine the nitrogen content. At this time, if the nitrogen content is unqualified, it is necessary to re-evacuate or add nitrogen, which makes the operation cumbersome, time-consuming and labor-intensive, thereby reducing the overall efficiency of VD refining and reducing economic benefits.

[0062] In order to solve the problem that the nitrogen content cannot be obtained during vacuum degassing, some embodiments of this application first provide a method for predicting the nitrogen content of molten steel during VD refining process, see Figure 1 , methods include:

[0063] S100: Acquire process parameters of the VD vacuum degassing process.

[0064] After the refining furnace enters the blowing station, degassing begins. The process parameters of the vacuum degassing process obtained before degassing begins include molten steel temperature, interaction coefficient, mass percentage of elements in molten steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, bottom blowing gas type and bottom blowing gas flow rate per unit time, among which the interaction coefficient is the interaction coefficient of the elements in the molten steel to the nitrogen element, the interaction coefficient of the elements in the molten steel to the nitrogen element is a parameter that can be obtained through query, the molten steel temperature, the mass percentage of elements in the molten steel, and the partial pressure of nitrogen in nitrogen bubbles can be obtained through actual measurement, and the vacuum chamber pressure, bottom blowing gas type and bottom blowing gas flow rate per unit time are the process parameters set before degassing.

[0065] S200: constructing a nitrogen content prediction model to output a predicted value of a target nitrogen content in the molten steel according to the input process parameters.

[0066] The prediction model includes a first calculation module, a second calculation module, a third calculation module, a fourth calculation module, a correction module and a fifth calculation module.

[0067] The first calculation module is used to calculate the activity coefficient of nitrogen in the molten steel according to the interaction coefficient and the mass percentage of the element in the molten steel. In some embodiments, the activity coefficient of nitrogen in the molten steel can be calculated by the following formula:

[0068] lgf N =∑e j N w j ;

[0069] Among them, f N is the activity coefficient, e j N is the interaction coefficient of the elements in the molten steel to the nitrogen element; w j is the mass percentage of the element in the molten steel. In the embodiment of the present application, the elements in the molten steel mainly include nitrogen, carbon, silicon, manganese, phosphorus and sulfur. After respectively obtaining the interaction coefficients of nitrogen, carbon, silicon, manganese, phosphorus and sulfur with nitrogen, the activity coefficient of nitrogen in the molten steel is calculated.

[0070] The second calculation module is used to calculate the dissolution equilibrium constant of nitrogen in the molten steel according to the temperature of the molten steel. In some embodiments, the dissolution equilibrium constant of nitrogen in the molten steel can be calculated by the following formula:

[0071]

[0072] Among them, K N is the dissolution equilibrium constant, and T is the temperature of the molten steel.

[0073] The third calculation module is used to calculate the first nitrogen content according to the partial pressure of nitrogen in the nitrogen bubbles, the activity coefficient and the solubility equilibrium constant. The first nitrogen content is the mass percentage of nitrogen when it reaches solubility equilibrium in the molten steel. When the nitrogen reaches solubility equilibrium in the molten steel, the vacuum degassing process reaches equilibrium, that is, the degassing equilibrium. The degassing equilibrium means that under the current parameter conditions, the nitrogen content in the molten steel reaches the minimum value. Without changing the environmental parameters, the nitrogen content cannot be further reduced. It is the theoretical equilibrium moment in thermodynamics. In order to achieve degassing, the degassing reaction must meet the thermodynamic requirements, that is, the limiting equilibrium value is low enough, otherwise it is difficult to meet the degassing requirements even if the time is extended. Therefore, it is necessary to calculate the mass percentage of nitrogen when it reaches solubility equilibrium in the molten steel, and predict the nitrogen content in the molten steel by the mass percentage of nitrogen when it reaches solubility equilibrium in the molten steel. In some embodiments, the first nitrogen content can be calculated by the following formula:

[0074]

[0075] Where, [%N] eq is the first nitrogen content, K N is the solubility equilibrium constant, is the partial pressure of nitrogen in the nitrogen bubble, P θ is standard atmospheric pressure, f N is the activity coefficient.

[0076] The fourth calculation module is used to calculate the first ratio according to the vacuum chamber pressure and the bottom blowing gas flow rate per unit time. The first ratio is the ratio of the interface reaction area to the molten pool volume. In some embodiments, the first ratio can be calculated by the following formula:

[0077]

[0078] Among them, B is the first ratio, Q is the bottom blowing gas flow rate per unit time, P1 is the vacuum chamber pressure, and Δt is the time change. It should also be noted that the nitrogen bubbles generated during the degassing process escape from the molten steel. When the internal pressure of the bubble is equal to the external pressure, the degassing process reaches a balanced state. The external pressure of the bubble is the vacuum chamber pressure, and the pressure inside the bubble is the nitrogen partial pressure. Therefore, it can be considered that the nitrogen partial pressure in the nitrogen bubble is P N2 Equal to the vacuum chamber pressure P1.

[0079] The correction module is used to correct the model parameters of the prediction model according to the initial mass transfer coefficient to obtain the corrected mass transfer coefficient. Figure 2 In some embodiments, correcting the model parameters of the prediction model according to the initial mass transfer coefficient to obtain the corrected mass transfer coefficient comprises the following steps:

[0080] S251: Obtain the initial mass transfer coefficient.

[0081] The initial mass transfer coefficient is a continuous value within a preset range. The initial mass transfer coefficient is set to A0, then A0∈[0.005, 0.1].

[0082] S252: Divide the initial mass transfer coefficient according to a preset step length to obtain a plurality of mass transfer coefficients.

[0083] In some embodiments, the preset step size may be 0.005, and after the initial mass transfer coefficient is divided according to the preset step size, several mass transfer coefficients A may be obtained. i , such as 0.005, 0.01, 0.015, 0.02…0.1.

[0084] S253: Acquire historical data, which is the actual measured value of nitrogen content in the molten steel after the degassing process is completed.

[0085] S254: Calculate a first nitrogen content prediction value according to the mass transfer coefficient.

[0086] The first nitrogen content prediction value is the nitrogen content prediction value in the molten steel after the degassing process is completed. When the bottom blowing gas is nitrogen, the first nitrogen content prediction value is calculated by the following formula:

[0087]

[0088] When the bottom blowing gas is argon, the first nitrogen content prediction value is calculated by the following formula:

[0089]

[0090] in, is the first nitrogen content prediction value, y i ' is the measured value of nitrogen content at the beginning of degassing, [%N] eq is the first nitrogen content, η is a dimensionless number, ranging from 0.3 to 0.8, A i is the mass transfer coefficient, B is the first ratio, and t is the degassing time.

[0091] S255: Calculate the average absolute error based on the historical data and the first nitrogen content prediction value.

[0092] In some embodiments, the mean absolute error may be calculated by the following formula:

[0093]

[0094] Among them, MAE is the mean absolute error, is the first nitrogen content prediction value, y i is the measured value of nitrogen content in the molten steel after the degassing process. Each historical data corresponds to a first nitrogen content prediction value, and the average absolute error can be calculated by the acquired historical data and the first nitrogen content prediction value calculated according to one of the mass transfer coefficients.

[0095] S256: Traverse the mass transfer coefficients to obtain the mass transfer coefficient corresponding to the minimum mean absolute error, and output the mass transfer coefficient as the modified mass transfer coefficient.

[0096] By correcting the model parameters, the accuracy of the model can be improved and the accuracy of the calculation results can be improved.

[0097] The fifth calculation module is used to calculate the second nitrogen content in the molten steel according to the first nitrogen content, the modified mass transfer coefficient, the type of bottom blowing gas and the first ratio, and output the second nitrogen content as a predicted value of the target nitrogen content.

[0098] For steel grades with low nitrogen content, if the nitrogen content in the molten steel is high at the beginning, in order to remove other gas components (hydrogen, oxygen, etc.) without increasing the nitrogen content, argon can be selected as the bottom blowing gas; for steel grades with upper and lower limits for nitrogen content, in order to remove other gas components (hydrogen, oxygen, etc.) while retaining nitrogen as much as possible, nitrogen can be selected as the bottom blowing gas, so the bottom blowing gas includes nitrogen and argon. The second nitrogen content in the molten steel is calculated by the fifth calculation module according to the first nitrogen content, the modified mass transfer coefficient, the type of bottom blowing gas and the first ratio, including:

[0099] In some embodiments, when the bottom blowing gas is nitrogen, the second nitrogen content is calculated by the following formula:

[0100] [%N]2=[%N]1-η×A×B×([%N]1-[%N] eq )×Δt1;

[0101] When the bottom blowing gas is argon, the second nitrogen content is calculated by the following formula:

[0102] [%N]2=[%N]1-A×B×([%N]1-[%N] eq )×Δt1;

[0103] Wherein, [%N]2 is the second nitrogen content, [%N]1 is the predicted value of the nitrogen content in the molten steel at the initial moment of the preset time, A is the modified mass transfer coefficient, B is the first ratio, and Δt1 is the preset time. The second nitrogen content is the predicted nitrogen content in the molten steel during the degassing process, that is, the predicted value of the target nitrogen content. It can be understood that when the initial moment of the preset time is the start moment of degassing, the predicted value of the nitrogen content in the molten steel is the actual measured value of the nitrogen content in the molten steel. In some embodiments, the preset time can be 1s or an integer greater than 1s.

[0104] See also Figure 3 In some implementations, the method further includes: if the degassing process is not over, continuing to calculate the dissolution equilibrium constant according to the molten steel temperature through the second calculation module; calculating the first nitrogen content according to the partial pressure, activity coefficient and dissolution equilibrium constant of nitrogen in the nitrogen bubbles through the third calculation module; calculating the first ratio according to the vacuum chamber pressure and the bottom blowing gas flow rate per unit time through the fourth calculation module; calculating the second nitrogen content according to the first nitrogen content, the corrected mass transfer coefficient, the bottom blowing gas type and the first ratio through the fifth calculation module; until the degassing process is over, the second nitrogen content is output as the predicted value of the target nitrogen content, and the prediction model stops at this time.

[0105] It should be noted that, due to the different supply pressures of nitrogen and argon, the order of bottom blowing gas during the degassing process is to blow nitrogen first and then blow argon. For molten steel with different initial nitrogen contents, when different bottom blowing gases are used for vacuum degassing, the calculated nitrogen content prediction values ​​are shown in Tables 1 and 2, respectively.

[0106] Table 1 shows the predicted value of nitrogen content in liquid steel during degassing when the initial nitrogen content is high

[0107]

[0108]

[0109] In Table 1, the measured value of the initial nitrogen content of the molten steel is 337ppm, which is the initial value [%N]1 of the molten steel content predicted for the next preset time (i.e., the 1st second). It can be seen from Table 1 that at the 1465th second, the bottom blowing gas changes, and at the 1781st second, the vacuum degassing process ends. At this time, the nitrogen content in the molten steel predicted at the 1781st second is 135.4ppm, and the degassing process ends at this time. The nitrogen content in the molten steel actually measured after the degassing process ends is 131ppm. It can be seen that the difference between the measured value and the predicted value of the nitrogen content after the degassing process ends is about 4.4ppm.

[0110] Table 2 shows the predicted value of nitrogen content in liquid steel during degassing when the initial nitrogen content is low

[0111]

[0112] In Table 2, the measured value of the initial nitrogen content of the molten steel is 281ppm, which is the initial value [%N]1 of the molten steel content predicted for the next preset time (i.e., the 1st second). As can be seen from Table 2, at the 2333rd second, the bottom blowing gas changes, and at the 2662nd second, the vacuum degassing process ends. At this time, the nitrogen content in the molten steel predicted at the 2662nd second is 103.2ppm, and the degassing process ends at this time. The nitrogen content in the molten steel actually measured after the degassing process ends is 101ppm. It can be seen that the difference between the measured value and the predicted value of the nitrogen content after the degassing process ends is 2.2ppm. It can be seen from the results in Tables 1 and 2 that the error between the calculated predicted value of the nitrogen content and the measured value of the nitrogen content is small, and the calculated predicted value of the nitrogen content can be used as the actual value of the nitrogen content in the molten steel during the degassing process.

[0113] The method provided in the present application can predict the nitrogen content in the molten steel during the vacuum degassing process by using the thermodynamic principle to calculate through the constructed prediction model, thereby solving the problem that the nitrogen content cannot be obtained during the vacuum degassing process, and the predicted value of the nitrogen content is calculated by the corrected mass transfer coefficient, thereby improving the accuracy of the calculation result. Since the predicted value of the nitrogen content in the degassing process calculated by the above method has a small error, it can provide theoretical guidance for actual production and better monitor the change of the nitrogen content in the molten steel during the vacuum process. For low-nitrogen steel, the degassing qualified rate can be improved to avoid re-extraction; for high-nitrogen steel, it helps to avoid too low nitrogen content in the molten steel and improve the intelligence level of the refining process.

[0114] Based on the above prediction method, some embodiments of the present application also provide a VD refining process steel liquid nitrogen content prediction system, which is applied to the method provided in the above real-time example, see Figure 4 , the system includes:

[0115] Acquisition module: used to acquire the process parameters of the VD vacuum degassing process; the process parameters include molten steel temperature, interaction coefficient, mass percentage of elements in the molten steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, bottom blowing gas type and bottom blowing gas flow rate per unit time, wherein the interaction coefficient is the interaction coefficient of the elements in the molten steel to the nitrogen element.

[0116] The first calculation module is used to calculate the activity coefficient of nitrogen in the molten steel according to the interaction coefficient and the mass percentage of the element in the molten steel;

[0117] The second calculation module is used to calculate the dissolution equilibrium constant of nitrogen in the molten steel according to the temperature of the molten steel;

[0118] The third calculation module is used to calculate the first nitrogen content according to the partial pressure, activity coefficient and dissolution equilibrium constant of nitrogen in the nitrogen bubbles, wherein the first nitrogen content is the mass percentage of nitrogen element when the dissolution equilibrium is reached in the molten steel;

[0119] A fourth calculation module: used to calculate a first ratio according to the vacuum chamber pressure and the bottom blowing gas flow rate per unit time, wherein the first ratio is a ratio of the interface reaction area to the molten pool volume;

[0120] Correction module: used to correct the model parameters of the prediction model according to the initial mass transfer coefficient to obtain the corrected mass transfer coefficient;

[0121] The fifth calculation module is used to calculate the second nitrogen content in the molten steel according to the first nitrogen content, the modified mass transfer coefficient, the type of bottom blowing gas and the first ratio, and output the second nitrogen content as a predicted value of the target nitrogen content.

[0122] It can be seen from the above technical solutions that the embodiment of the present application provides a method and system for predicting the nitrogen content of molten steel in a VD refining process, and the method includes: obtaining the process parameters of the VD vacuum degassing process, constructing a nitrogen content prediction model, and outputting the target nitrogen content prediction value in the molten steel according to the process parameters. The first calculation module in the prediction model is used to calculate the activity coefficient of the nitrogen element in the molten steel, the second calculation module is used to calculate the solubility equilibrium constant, the third calculation module is used to calculate the mass percentage of the nitrogen element when the dissolution equilibrium is reached in the molten steel, the fourth calculation module is used to calculate the first ratio, the correction module is used to obtain the corrected mass transfer coefficient, and the fifth calculation module is used to calculate the target nitrogen content prediction value. The method uses the thermodynamic principle to calculate the constructed prediction model, and can predict the nitrogen content in the molten steel during the vacuum degassing process, solve the problem that the nitrogen content cannot be obtained during the vacuum degassing process, and calculate the nitrogen content prediction value by the corrected mass transfer coefficient, which can improve the accuracy of the calculation result.

[0123] Similar parts between the embodiments provided in this application can be referenced to each other. The specific implementation methods provided above are only a few examples under the general concept of this application and do not constitute a limitation on the protection scope of this application. For those skilled in the art, any other implementation methods expanded based on the scheme of this application without creative work belong to the protection scope of this application.

Claims

1. A method for predicting nitrogen content in liquid steel during VD refining process, characterized in that: include: Obtaining process parameters of the VD vacuum degassing process, wherein the process parameters include molten steel temperature, interaction coefficient, mass percentage of elements in the molten steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, bottom blowing gas type and bottom blowing gas flow rate per unit time; the interaction coefficient is the interaction coefficient of the elements in the molten steel to the nitrogen element; Constructing a nitrogen content prediction model to output a predicted value of a target nitrogen content in the molten steel according to the process parameters; The prediction model includes: A first calculation module, used for calculating the activity coefficient of nitrogen in the molten steel according to the interaction coefficient and the mass percentage of the element in the molten steel; A second calculation module is used to calculate the dissolution equilibrium constant of nitrogen in the molten steel according to the temperature of the molten steel; a third calculation module, configured to calculate a first nitrogen content according to the partial pressure of nitrogen in the nitrogen bubbles, the activity coefficient and the dissolution equilibrium constant, wherein the first nitrogen content is a mass percentage of nitrogen when the nitrogen element reaches dissolution equilibrium in the molten steel; a fourth calculation module, configured to calculate a first ratio according to the vacuum chamber pressure and the bottom blowing gas flow rate per unit time, wherein the first ratio is a ratio of an interface reaction area to a molten pool volume; A correction module, used for correcting the model parameters of the prediction model according to the initial mass transfer coefficient to obtain a corrected mass transfer coefficient; The fifth calculation module is used to calculate the second nitrogen content in the molten steel according to the first nitrogen content, the modified mass transfer coefficient, the bottom blowing gas type and the first ratio, and output the second nitrogen content as a predicted value of the target nitrogen content.

2. The method for predicting nitrogen content in liquid steel during VD refining process according to claim 1, characterized in that: The solubility equilibrium constant of nitrogen in molten steel is calculated by the following formula: Among them, K N is the dissolution equilibrium constant, and T is the temperature of the molten steel.

3. The method for predicting nitrogen content in liquid steel during VD refining process according to claim 2, characterized in that: The first nitrogen content is calculated by the following formula: Where, [%N] eq is the first nitrogen content, K N is the solubility equilibrium constant, is the partial pressure of nitrogen in the nitrogen bubble, P θ is standard atmospheric pressure, f N is the activity coefficient.

4. The method for predicting nitrogen content in liquid steel during VD refining process according to claim 3, characterized in that: The first ratio is calculated by the following formula: Wherein, B is the first ratio, Q is the bottom blowing gas flow rate per unit time, P1 is the vacuum chamber pressure, and Δt is the time change.

5. The method for predicting nitrogen content in liquid steel during VD refining process according to claim 4, characterized in that: The step of correcting the model parameters of the prediction model according to the initial mass transfer coefficient to obtain a corrected mass transfer coefficient comprises: Obtaining an initial mass transfer coefficient, where the initial mass transfer coefficient is a continuous value within a preset range; Dividing the initial mass transfer coefficient according to a preset step size to obtain a plurality of mass transfer coefficients; Acquire historical data, wherein the historical data is the actual measured value of nitrogen content in the molten steel after the degassing process is completed; Calculating a first nitrogen content prediction value according to the mass transfer coefficient, wherein the first nitrogen content prediction value is a prediction value of nitrogen content in the molten steel after the degassing process is completed; Calculating a mean absolute error based on the historical data and the first nitrogen content prediction value; The mass transfer coefficients are traversed to obtain the mass transfer coefficient corresponding to the minimum mean absolute error, and the mass transfer coefficient is output as the modified mass transfer coefficient.

6. The method for predicting nitrogen content in liquid steel during VD refining process according to claim 5, characterized in that: The mean absolute error is calculated by the following formula: Among them, MAE is the mean absolute error, is the first nitrogen content prediction value, y i It is the actual measured value of nitrogen content in molten steel after the degassing process is completed.

7. The method for predicting nitrogen content in liquid steel during VD refining process according to claim 5, characterized in that: The bottom blowing gas includes nitrogen and argon, and the calculating the second nitrogen content in the molten steel according to the first nitrogen content, the modified mass transfer coefficient, the type of the bottom blowing gas and the first ratio includes: When the bottom blowing gas is nitrogen, the second nitrogen content is calculated by the following formula: [%N]2=[%N]1-η×A×B×([%N]1-[%N] eq )×Δt1; When the bottom blowing gas is argon, the second nitrogen content is calculated by the following formula: [%N]2=[%N]1-A×B×([%N]1-[%N] eq )×Δt1; Wherein, [%N]2 is the second nitrogen content, [%N]1 is the predicted value of the nitrogen content in the molten steel at the initial moment of the preset time, η is a dimensionless number, A is the modified mass transfer coefficient, B is the first ratio, and Δt1 is the preset time.

8. The method for predicting nitrogen content in liquid steel during VD refining process according to claim 7, characterized in that: When the initial moment of the preset time period is the degassing start moment, the predicted value of the nitrogen content in the molten steel is the actual measured value of the nitrogen content in the molten steel.

9. The method for predicting nitrogen content in liquid steel during VD refining process according to claim 1, characterized in that: The method further comprises: If the degassing process is not finished, continuing to calculate the dissolution equilibrium constant according to the molten steel temperature by the second calculation module; Calculating the first nitrogen content according to the partial pressure of nitrogen in the nitrogen bubbles, the activity coefficient and the solubility equilibrium constant by the third calculation module; Calculating the first ratio according to the vacuum chamber pressure and the bottom blowing gas flow rate per unit time by the fourth calculation module; Calculating the second nitrogen content by the fifth calculation module according to the first nitrogen content, the modified mass transfer coefficient, the bottom blowing gas type and the first ratio; Until the degassing process is completed, the second nitrogen content is output as the predicted value of the target nitrogen content.

10. A system for predicting nitrogen content in liquid steel during VD refining process, characterized in that: The method applied to any one of claims 1 to 9, wherein the system comprises: Acquisition module: used to acquire the process parameters of the VD vacuum degassing process, the process parameters including molten steel temperature, interaction coefficient, mass percentage of elements in the molten steel, partial pressure of nitrogen in nitrogen bubbles, vacuum chamber pressure, bottom blowing gas type and bottom blowing gas flow rate per unit time; the interaction coefficient is the interaction coefficient of the elements in the molten steel to the nitrogen element; A first calculation module: used for calculating the activity coefficient of nitrogen in the molten steel according to the interaction coefficient and the mass percentage of the element in the molten steel; A second calculation module: used for calculating the dissolution equilibrium constant of nitrogen in the molten steel according to the molten steel temperature; A third calculation module: used to calculate a first nitrogen content according to the partial pressure of nitrogen in the nitrogen bubbles, the activity coefficient and the dissolution equilibrium constant, wherein the first nitrogen content is the mass percentage of nitrogen element when the dissolution equilibrium is reached in the molten steel; A fourth calculation module: used to calculate a first ratio according to the vacuum chamber pressure and the bottom blowing gas flow rate per unit time, wherein the first ratio is a ratio of an interface reaction area to a molten pool volume; Correction module: used for correcting the model parameters of the prediction model according to the initial mass transfer coefficient to obtain a corrected mass transfer coefficient; The fifth calculation module is used to calculate the second nitrogen content in the molten steel according to the first nitrogen content, the modified mass transfer coefficient, the bottom blowing gas type and the first ratio, and output the second nitrogen content as a predicted value of the target nitrogen content.

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