Square billet continuous casting dynamic piecewise function type soft reduction control method for inhibiting temperature fluctuation influence

Abstract

The invention relates to a square billet continuous casting dynamic piecewise function type soft reduction control method for inhibiting temperature fluctuation influence, which belongs to the technical field of continuous casting and comprises the following steps: S1, adopting a dynamic secondary cooling model to calculate a temperature field and a center solid fraction of a continuous casting billet along a throwing direction in real time on line; s2, establishing a reduction model by adopting finite element stress-strain simulation, coupling a temperature field into the reduction model, calculating theoretical optimal reduction under soft reduction under different center solid fractions, and fitting a piecewise function of the theoretical optimal reduction Y under soft reduction along with the center solid fractions; s3, on the basis of the piecewise function, the dynamic soft reduction model extracts the center solid fraction corresponding to the reduction roller from the dynamic secondary cooling temperature calculation model in real time, the real-time theoretical reduction is calculated, and the final set reduction is obtained through a dynamic reduction fluctuation suppression algorithm and judgment of a threshold value n; and S4, if the segregation problem of the casting blank still exists, the rolling reduction is set for a soft reduction experiment, the piecewise function is corrected, and the casting blank is put into use again.

Description

Technical Field

[0001] The invention belongs to the technical field of continuous casting, and relates to a dynamic piecewise functional soft reduction control method for continuous casting of square billets for suppressing the influence of temperature fluctuations. Background Art

[0002] For the continuous casting process of square billet, segregation, shrinkage and shrinkage cavity are important factors that lead to quality problems of the billet. At present, in the field of continuous casting technology, light pressure reduction is the main means to solve segregation, and heavy pressure reduction is the main means to solve shrinkage and shrinkage cavity. They are all to prevent the generation of billet defects by carrying out appropriate pressure reduction at the appropriate solid phase ratio position of the billet center. For the pressure reduction technology itself, it is generally believed that the more pressure is pressed, the better the effect, but too high a pressure reduction will cause internal cracks, so it is very important to determine the limit pressure reduction when no cracks are generated (theoretical optimal pressure reduction). The mechanical properties of the material determine the maximum deformation that it can withstand when no cracks are generated. Since the billet temperature is continuously cooled and lowered in the direction of the billet drawing, the mechanical properties of the billet are continuously changed in space, so the appropriate pressure reduction at different solid phase ratios of the billet center is also different. At present, there is a method that can express the relationship between the theoretical optimal pressure reduction and the solid phase ratio of the center through a function, such as patent CN116652143A. The solid phase ratio at the center of the billet is obtained in real time through the dynamic secondary cooling temperature calculation model, and the appropriate reduction at different center solid phase ratios is determined according to the stress-strain simulation. However, in the actual continuous casting production process, the center solid phase ratio at the pressure reduction roller may fluctuate slightly for the following reasons: 1. The small fluctuations caused by the pulling speed control lead to fluctuations in the heat transfer calculation; 2. The dynamic secondary cooling temperature calculation continuously adjusts the water volume according to the target temperature of the billet. When the pulling speed changes, the original heat transfer steady state will be broken, and the water volume will be adjusted. During this adjustment process, the calculated temperature will fluctuate around the target temperature until it reaches the target temperature. During the water volume adjustment process, the center solid phase ratio of the billet also fluctuates continuously within a small range; 3. Fluctuations caused by the water volume control of the water nozzle. Especially after the equipment ages or the nozzle is scaled, the water volume control is not as accurate as before, resulting in water volume fluctuations and temperature fluctuations. The above reasons will cause the center solid phase ratio of the billet corresponding to the pressure reduction roller to fluctuate, which in turn causes the set pressure reduction calculated by the dynamic pressure reduction model to fluctuate, causing the pressure reduction roller to continuously move a small amount, which causes the load on the hydraulic system of the equipment and reduces the life of the equipment. At the same time, since the ingot has not been completely solidified in the light pressure reduction area, the strength of its solidification front and the nearby shell is very low. The continuous deformation of the low-strength area caused by this fluctuation may also increase the probability of internal cracks. However, in the patents or literature related to pressure reduction research, most of the focus is on the optimal design of the pressure reduction position or pressure reduction amount during the steady-state continuous casting process, and the dynamic pressure reduction amount fluctuation problem under the actual continuous casting state is not considered in the pressure reduction calculation model. In addition, since only the theoretical optimal pressure reduction amount can be determined through simulation, the actual pressure reduction effect still needs to be finally determined by experiment, which requires that the pressure reduction amount control function can be flexibly changed to adapt to the experiment and modify it. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a dynamic piecewise functional light reduction control method for continuous casting of square billet to suppress the influence of temperature fluctuations. The method is based on the dynamic secondary cooling temperature field calculation, combined with the dynamic reduction model, and the theoretical reduction of each roller is calculated in real time according to the reduction piecewise function, and then the final set reduction is determined by the dynamic reduction fluctuation suppression algorithm. This method avoids the change of reduction caused by temperature fluctuations, which is conducive to the stability of the reduction equipment and the quality of the billet. At the same time, the piecewise functional reduction mathematical model is highly flexible, and different corrections can be made to the reduction in each reduction interval according to field tests.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A dynamic piecewise functional soft reduction control method for continuous casting of square billet for suppressing the influence of temperature fluctuations comprises the following steps:

[0006] S1: The dynamic secondary cooling model is used to calculate the temperature field and the central solid fraction f of the continuous casting billet along the billet drawing direction in real time online. s ;

[0007] S2: The finite element stress-strain simulation software is used to establish a reduction model, and the temperature field is coupled to the reduction model to calculate the theoretical optimal reduction under light pressure at different central solid fractions. Then, the theoretical optimal reduction Y under light pressure is fitted with the central solid fraction f. s Piecewise function of ;

[0008] S3: Based on the piecewise function, the dynamic soft reduction model extracts the central solid phase ratio corresponding to the reduction roller from the dynamic secondary cooling temperature calculation model in real time, thereby calculating the real-time theoretical reduction amount, and then obtains the final set reduction amount through the dynamic reduction fluctuation suppression algorithm and the judgment of the threshold value n;

[0009] S4: If the segregation problem of the ingot still exists when the theoretical optimal reduction amount piecewise function of light reduction is actually used, the reduction amount is manually set to conduct a light reduction experiment to determine the appropriate reduction amount, and then the piecewise function is corrected and used again.

[0010] Further, in step S1, the temperature field and the center solid fraction f of the billet along the billet drawing direction are obtained through the real-time dynamic secondary cooling temperature field model. s .

[0011] Further, in step S2, the piecewise function is:

[0012]

[0013] Soft reduction is implemented in the ingot region near the solidification endpoint; the expression form of each segment of the piecewise function is not limited, and the principle is to fit the numerical variation law of the theoretical optimal reduction with the center solid phase ratio.

[0014] Furthermore, in step S2, the theoretical optimal reduction under different central solid fractions is determined by finite element stress-strain simulation, and is fitted into a piecewise function curve of the reduction with respect to the central solid fraction; the more segmentations of the total solid fraction interval, the higher the fitting accuracy.

[0015] Furthermore, in step S2, when the total light reduction amount is constant, the roller with the larger reduction amount is preferentially pressed down until the total reduction amount is met.

[0016] Further, in step S3, the judgment logic of the pressure fluctuation suppression algorithm is:

[0017] Taking a single reduction roll as the object, let the calculated reduction amount of the dynamic reduction model at the current moment and the actual reduction amount be Y 0 , take it as the initial value, and then record the calculated pressure Y for each T real-time calculation after this moment 1 , Y 2 ...Y T , get the minimum value Y min ;

[0018] Before the Tth real-time calculation, the pressing amount is always Y 0 ; In the Tth real-time calculation, if |Y 0 -Y min |≤threshold n, then in the Tth real-time calculation, Y T =Y 0 , implement Y 0 Press down; otherwise, Y T =Y min , implement Y min The amount of pressure reduction;

[0019] Then, Y T As the initial amount, it enters the next cycle, that is, the subsequent T times of real-time calculation until the pouring is completed.

[0020] Furthermore, in step S3, the T value is related to the stability of the continuous casting process itself. If the process is stable, the T value is 1, and if the process is unstable, the T value increases according to demand.

[0021] Furthermore, the threshold n is determined according to the total light depression amount.

[0022] The beneficial effects of the present invention are as follows: the light reduction control method of the present invention has strong adaptability to actual continuous casting conditions, and at the same time reduces the unnecessary up and down movement frequency of the reduction roller during the dynamic light reduction of the square billet, reduces the workload of the reduction equipment, is beneficial to improving the service life of the equipment, and also avoids the billet quality problems that may be caused by reduction fluctuations.

[0023] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0025] Figure 1 It is a schematic diagram of a billet continuous casting machine;

[0026] Figure 2 This is a schematic diagram of the real-time online simulation of the casting strand temperature field;

[0027] Figure 3 This is a schematic diagram of finite element stress-strain simulation;

[0028] Figure 4 This is a schematic diagram of the piecewise function of the optimal reduction amount in light reduction theory fitted;

[0029] Figure 5 Schematic diagram of the roll gap calculated by the real-time online soft reduction model. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0031] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0032] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0033] like Figure 1 As shown, the present invention is applicable to the remote control of the reduction amount of the square billet continuous casting machine through the reduction amount calculation model.

[0034] The present invention provides a dynamic piecewise functional soft reduction control method for continuous casting of square billet for suppressing the influence of temperature fluctuation, comprising the following steps:

[0035] S1. Use the dynamic secondary cooling model to calculate the temperature field and center solid fraction f of the continuous casting billet along the billet drawing direction in real time online s ;like Figure 2 As shown in the figure, the temperature field and central solid fraction f of the billet along the drawing direction are obtained through the real-time dynamic secondary cooling temperature field model. s .

[0036] S2. Figure 3 As shown in the figure, the finite element stress-strain simulation software is used to establish the reduction model, the temperature field is coupled to the reduction model, the theoretical optimal reduction under light pressure at different center solid fractions is calculated, and then the theoretical optimal reduction Y (unit: mm) under light pressure is fitted with the center solid fraction f s A piecewise function of :

[0037]

[0038] Among them, light reduction should be implemented in the area of ​​the billet near the end of solidification. Generally speaking, f 0 =0.3, f n =1. The piecewise function Y=F(f s ) The expressions of each section are not limited to constants, multi-time functions and trigonometric functions. The principle is to accurately fit the numerical variation law of the theoretical optimal reduction with the central solid phase fraction.

[0039] S3. The piecewise function Y=F(f s ), the dynamic soft reduction model extracts the central solid phase ratio corresponding to the reduction roller from the dynamic secondary cooling temperature calculation model in real time, thereby calculating the real-time theoretical reduction amount, and then obtains the final set reduction amount through the dynamic reduction fluctuation suppression algorithm and the judgment of the threshold value n. The judgment logic of the reduction fluctuation suppression algorithm is: taking a single reduction roller as the object, assuming that the calculated reduction amount of the dynamic reduction model at the current moment and the actual reduction amount implemented are Y 0, which is used as the initial value, and then the calculated pressure Y for each real-time calculation within T times after this moment is recorded 1 , Y 2 ...Y T , get the minimum value Y min Before the Tth real-time calculation, the pressing amount is always Y 0 . In the Tth real-time calculation, if |Y 0 -Y min |≤threshold n, then in the Tth real-time calculation, Y T =Y 0 , implement Y 0 Press down; otherwise, Y T =Y min , implement Y min Then, Y T As the initial quantity, it enters the judgment of the next cycle (i.e. the subsequent T real-time calculations) until the pouring is completed.

[0040] The T value is related to the stability of the continuous casting process itself. If the process is stable, the T value can be 1. If the process is unstable, the T value increases according to demand. The judgment cycle should be less than 10s. The threshold value n is related to the total soft reduction and is generally less than 1mm.

[0041] S4. If the theoretical optimal pressure reduction amount piecewise function Y=F(f s ), if the segregation problem of the ingot still exists, a light pressure test can be conducted to actually determine the appropriate pressure reduction under one or more solid phase ratios, and then return to the modified piecewise function Y = F (f s ), transfer to S3 and put it into use again.

[0042] Example 1

[0043] A steel plant uses an arc-shaped large square billet continuous casting machine to produce billets with a cross-section of 420mm×530mm, the production steel type is X, the casting speed is 0.5m / min, the casting temperature is 1525℃, and the total soft reduction is 10mm. There are 10 reduction rollers in the casting machine, and the reduction is remotely controlled through the reduction calculation model.

[0044] The specific steps are as follows:

[0045] 1) During the production process of the casting machine, the secondary cooling temperature field simulation model is used to calculate the casting machine temperature field, and the temperature field of the area near the solid phase ratio of the center of the casting billet is obtained as the initial temperature field of the stress-strain simulation model;

[0046] 2) Establish a light reduction stress-strain model for 420mm×530mm ingot for simulation, determine the theoretical optimal reduction amount Y under multiple solid phase ratios, and fit it to a piecewise function. Figure 4As shown in the figure, the theoretical optimal reduction under different central solid phase ratios is determined by finite element stress-strain simulation, and the reduction is fitted into a piecewise function curve with respect to the central solid phase ratio. The total solid phase ratio range is generally 0.3-1.0, and the solid phase ratio range 0.3-1.0 is divided into 7 intervals, each with a span of 0.1. The theoretical optimal reductions Y1 to Y8 under 8 solid phase ratios in 0.3-1.0 are determined, and finally fitted into a piecewise function. When the total light reduction is certain, the roller with a large reduction is pressed first until the total reduction is met.

[0047] 3) Based on the real-time secondary cooling temperature field simulation model, the corresponding central solid phase ratio of each pressing roller is calculated. Then, the theoretical optimal pressing amount of each roller is calculated according to the fitted pressing amount piecewise function, and the pressing fluctuation suppression algorithm is introduced to finally obtain the final pressing amount of each pressing roller, such as Figure 5 .

[0048] 4) If the simulated theoretical optimal reduction piecewise function has a good effect on suppressing segregation, then this reduction curve is used. Otherwise, experiments are conducted to conduct single-roll reduction tests on the reductions at 8 solid phase ratios from 0.3 to 1.0, and the appropriate reduction at each solid phase ratio is determined, so as to return to the modified reduction piecewise function and use it again to ensure real-time control of the roll gap.

[0049] In the above embodiments, the description's reference to "this embodiment" indicates that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least some embodiments, but not necessarily all embodiments. Multiple occurrences of "this embodiment" do not necessarily all refer to the same embodiment.

[0050] In the above-described embodiments, although the invention has been described in conjunction with specific embodiments of the invention, many substitutions, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art based on the foregoing description. For example, other storage structures (e.g., dynamic RAM (DRAM)) may use the embodiments discussed. Embodiments of the invention are intended to encompass all such substitutions, modifications, and variations that fall within the broad scope of the appended claims.

[0051] This embodiment further provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, any one of the methods in this embodiment is implemented.

[0052] This embodiment also provides an electronic terminal, including: a processor and a memory;

[0053] The memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory, so that the terminal executes any one of the methods in this embodiment.

[0054] The computer-readable storage medium in this embodiment can be understood by ordinary technicians in this field: all or part of the steps of implementing the above-mentioned method embodiments can be completed by hardware related to the computer program. The aforementioned computer program can be stored in a computer-readable storage medium. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk and other media that can store program codes.

[0055] The electronic terminal provided in this embodiment includes a processor, a memory, a transceiver and a communication interface. The memory and the communication interface are connected to the processor and the transceiver and complete communication with each other. The memory is used to store computer programs, the communication interface is used to communicate, and the processor and the transceiver are used to run computer programs so that the electronic terminal executes each step of the above method.

[0056] In this embodiment, the memory may include a random access memory (RAM), and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0057] The above-mentioned processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0058] The present invention can be used in many general or special computing system environments or configurations, such as personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronic devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, and the like.

[0059] The present invention may be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules may be located in local and remote computer storage media, including storage devices.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A dynamic piecewise functional soft reduction control method for continuous casting of square billet to suppress the influence of temperature fluctuation, characterized in that: The following steps are involved: S1: The dynamic secondary cooling model is used to calculate the temperature field and the central solid fraction f of the continuous casting billet along the billet drawing direction in real time online. s ; S2: The finite element stress-strain simulation software is used to establish a reduction model, and the temperature field is coupled to the reduction model to calculate the theoretical optimal reduction under light pressure at different central solid fractions. Then, the theoretical optimal reduction Y under light pressure is fitted with the central solid fraction f. s Piecewise function of ; S3: Based on the piecewise function, the dynamic soft reduction model extracts the central solid phase ratio corresponding to the reduction roller from the dynamic secondary cooling temperature calculation model in real time, thereby calculating the real-time theoretical reduction amount, and then obtains the final set reduction amount through the dynamic reduction fluctuation suppression algorithm and the judgment of the threshold value n; S4: If the segregation problem of the ingot still exists when the theoretical optimal reduction amount piecewise function of light reduction is actually used, the reduction amount is manually set to conduct a light reduction experiment to determine the appropriate reduction amount, and then the piecewise function is corrected and used again.

2. The dynamic piecewise functional soft reduction control method for continuous casting of square billet for suppressing the influence of temperature fluctuation according to claim 1, characterized in that: In step S1, the temperature field and the center solid fraction f of the billet along the billet drawing direction are obtained through the real-time dynamic secondary cooling temperature field model. s .

3. The dynamic piecewise functional soft reduction control method for continuous casting of billet for suppressing the influence of temperature fluctuation according to claim 1, characterized in that: In step S2, the piecewise function is: Soft reduction is implemented in the ingot region near the solidification endpoint; the expression form of each segment of the piecewise function is not limited, and the principle is to fit the numerical variation law of the theoretical optimal reduction with the center solid phase ratio.

4. The dynamic piecewise functional soft reduction control method for continuous casting of billet for suppressing the influence of temperature fluctuation according to claim 1, characterized in that: In step S2, the theoretical optimal reduction under different central solid fractions is determined by finite element stress-strain simulation, and is fitted into a piecewise function curve of the reduction with respect to the central solid fraction; the more segmentations of the total solid fraction interval, the higher the fitting accuracy.

5. The dynamic piecewise functional soft reduction control method for continuous casting of square billet for suppressing the influence of temperature fluctuation according to claim 1, characterized in that: In step S2, when the total light reduction amount is constant, the roller with the larger reduction amount is preferentially pressed down until the total reduction amount is met.

6. The dynamic piecewise functional soft reduction control method for continuous casting of billet for suppressing the influence of temperature fluctuation according to claim 1, characterized in that: In step S3, the judgment logic of the pressure fluctuation suppression algorithm is: Taking a single pressing roll as the object, let the calculated pressing amount of the dynamic pressing model at the current moment and the actual pressing amount implemented be Y0, which is used as the initial value, and then record the calculated pressing amount Y1, Y2...Y within T real-time calculations after this moment. T , get the minimum value Y min ; Before the Tth real-time calculation, the pressing amount is always Y0; at the Tth real-time calculation, if |Y0-Y min |≤threshold n, then in the Tth real-time calculation, Y T =Y0, implement Y0 pressing amount; otherwise, T =Y min , implement Y min The amount of pressure reduction; Then, Y T As the initial amount, it enters the next cycle, that is, the subsequent T times of real-time calculation until the pouring is completed.

7. The dynamic piecewise functional soft reduction control method for continuous casting of billet for suppressing the influence of temperature fluctuation according to claim 1, characterized in that: In step S3, the T value is related to the stability of the continuous casting process itself. If the process is stable, the T value is 1. If the process is unstable, the T value increases according to demand.

8. The dynamic piecewise functional soft reduction control method for continuous casting of square billet for suppressing the influence of temperature fluctuation according to claim 1, characterized in that: The threshold value n is determined according to the total light depression amount.

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