A control method for a rotary electromagnetic stirrer of a continuous casting machine

Abstract

The present invention relates to a control method for a rotating electromagnetic stirrer of a continuous casting machine, and belongs to the technical field of metallurgical automation control methods. The technical solution of the present invention is: using a frequency converter or variable frequency power supply device with a vector control function, after an identification process to adapt to changes in the metallurgical process and equipment environment, matching the operating parameters, driving the electromagnetic stirrer to output a stirring frequency and stirring torque that meet the process requirements, and at the same time controlling the upper limit of the torque current, limiting the excitation current component to avoid oversaturation of the magnetic circuit, thereby achieving precise control of the operating parameters of the electromagnetic stirrer. The beneficial effects of the present invention are: avoiding blindly increasing the voltage and current of the electromagnetic stirrer to cause additional power loss and equipment overheating, etc., to achieve energy-saving and efficient operation; it can also provide auxiliary criteria for changes in the risk level of steel leakage during the steel drawing process of the continuous casting machine.

Description

Technical Field

[0001] The invention relates to a control method for a rotary electromagnetic stirrer of a continuous casting machine, belonging to the technical field of metallurgical automation control methods. Background Art

[0002] exist Continuous Casting Technology In the field, with the continuous development of technology and the increasing competition in the steel industry market,

[0003] The quality of ingots has gradually become a key limiting factor in continuous casting production and has received increasing attention from users and manufacturers, especially when producing high-quality steel and special-purpose steel, which places higher requirements on the quality of continuous casting ingots.

[0004] In continuous casting technology, the molten steel is cooled inside the crystallizer and forms a solidified shell of a certain thickness.

[0005] After the crystallizer, the inside of the billet is still in liquid state, forming a long liquid core. In the secondary cooling stage, the billet is cooled for the second time, and the solidified billet shell gradually becomes thicker until the core of the billet is completely solidified. The continuous casting process is the process of gradual solidification of the liquid core of the billet.

[0006] Continuous casting electromagnetic stirring The essence of the process is to strengthen the movement of molten steel in the liquid phase hole by means of the electromagnetic force induced in the liquid phase hole of the billet, thereby strengthening the convection, heat transfer and mass transfer process of the molten steel, thereby controlling the solidification process of the billet, which has a positive effect on improving the quality of the billet. The convection movement of molten steel in the liquid phase hole of the continuous casting billet has a significant impact on eliminating overheating, improving the solidification structure and component segregation of the billet. The driving force for the flow of molten steel comes from the kinetic energy of the casting stream and external force. The former is related to the pouring method, and the latter can be applied to any position of the liquid phase hole. That is, electromagnetic stirring is used, and the influence of the latter is far greater than the former.

[0007] The electromagnetic stirrers used in the continuous casting process are of the following types according to their installation positions in the arc section of the casting machine:

[0008] (1) Crystallizer electromagnetic stirrer MEMS: It is a device applicable to all kinds of continuous casting machines. It has a significant effect on improving the surface quality of the ingot, refining the grains, and reducing the inclusions and center looseness inside the ingot. It is the most widely used. In order not to affect the use of the liquid level automatic control device, it is generally installed at the bottom of the crystallizer.

[0009] (2) Second cooling section electromagnetic stirrer SEMS: It can be divided into second cooling section electromagnetic stirrer S1EMS and second cooling section electromagnetic stirrer S2EMS. S1EMS is installed at the foot roller of the first section of the crystallizer. Its function is similar to MEMS. The two are not reused. Since it is easy to replace and maintain, its investment and operating costs are relatively economical. S2EMS is an effective means to promote grain refinement of the ingot and is generally used together with MEMS or S1EMS.

[0010] (3) FEMS electromagnetic stirrer at the end of solidification: It is generally used when pouring high-carbon steel grades that have strict requirements on carbon segregation. To ensure the stirring effect, its installation position should be close to the end of solidification and allow adjustment.

[0011] The magnetic field motion characteristics of electromagnetic stirrers can be summarized into four categories: rotating magnetic field type, traveling wave magnetic field type, spiral magnetic field type and constant magnetic field type.

[0012] Rotary electromagnetic stirrer The operating principle is similar to that of an asynchronous motor. The electromagnetic stirrer body is equivalent to the stator of the motor, and the molten metal is equivalent to the rotor. The rotating magnetic field generated by the stirrer acts on the molten metal to generate an induced current in it. This current interacts with the magnetic field generated by the stirrer to generate an electromagnetic force, which drives the molten metal to rotate.

[0013] Vector Control The basic principle of implementation is to measure and control the stator current vector of the asynchronous motor, and control the excitation current and torque current of the asynchronous motor respectively according to the magnetic field orientation principle, so as to achieve the purpose of controlling the torque of the asynchronous motor.

[0014] Motor Identification Process: Before the inverter or drive is officially put into operation, a voltage / current signal of a certain frequency and amplitude is injected into the motor winding based on a specific algorithm and operation process, and then some electrical information reflected by the motor (including the motor, cable, electrical contact, etc.) is detected online, so as to calculate the model parameters of the motor, so as to identify the motor, configure higher-level parameters for the motor, and optimize the operation control.

[0015] Magnetic saturation It is a physical property of magnetic materials. It means that due to the limitation of physical structure, the magnetic flux passing through the magnetic material cannot be infinitely increased, so it is kept at a certain amount. After the magnetic circuit reaches saturation, even if the excitation current is greatly increased, the increase in magnetic flux is very small, which will only cause the excitation coil and the magnetic circuit core components to heat up.

[0016] As an important process equipment of the continuous casting machine in steel mills, the continuous casting electromagnetic stirrer has been widely used because it has a good stirring effect on the molten steel and is of great benefit to improving the quality of the continuous casting billet. However, the current operating parameters (current, frequency, stirring mode, etc.) of the electromagnetic stirrer in the application of steel mills are set by the process personnel of the continuous casting line of the steel mill according to experience. In fact, most of these are just empirical data and cannot guarantee that they are the best parameters for the electromagnetic stirrer. Due to the large changes in the parameters of the molten steel on site, such as the temperature of the molten steel in the tundish, the composition of the molten steel, the cooling formula and other parameters will affect the state of the molten steel (such as the liquid phase ratio, etc.) and the magnetic circuit parameters at the actual working position of the electromagnetic stirrer, thereby affecting the effect of the electromagnetic stirrer. After the magnetic circuit reaches saturation, the result of blindly increasing the current is often not to improve the stirring effect, but to increase the heating of the electromagnetic stirrer equipment, resulting in energy waste, deterioration of the equipment operating environment, and accelerated equipment aging. Summary of the invention

[0017] The purpose of the present invention is to provide a control method for a rotating electromagnetic stirrer of a continuous casting machine. By combining and applying mature vector control technology, the excitation current and stirring force are measured and controlled in real time, the stirring force is directly controlled, the electromagnetic stirring effect is improved, and the blind increase of the voltage and current of the electromagnetic stirrer causing additional energy loss and equipment overheating is avoided, thereby achieving energy-saving and efficient operation. It can also provide auxiliary criteria for changes in the risk level of steel leakage during the steel drawing process of the continuous casting machine, effectively solving the above-mentioned problems existing in the background technology.

[0018] The technical solution of the present invention is: a control method for a rotary electromagnetic stirrer of a continuous casting machine, comprising the following steps:

[0019] (1) After the casting process begins, the electromagnetic parameter identification of the electromagnetic stirrer is started multiple times to obtain and save the identification data corresponding to different liquid phase ratios of the ingot;

[0020] (2) Each time the new identification data is compared with the previous one, the identification process is stopped when the identification data is stable, that is, the liquid phase ratio is fixed, and the electromagnetic stirrer is started to run at the frequency required by the process; the operating parameters of the electromagnetic stirrer are measured and recorded through the PLC and the host computer;

[0021] (3) The vector control function is used to achieve the stirring frequency required by the output process, control the upper limit of the torque current, and limit the excitation current component to avoid oversaturation of the magnetic circuit;

[0022] (4) In the case of continuous casting of different steel grades or changing the cooling system, a candidate operation is provided: suspending the operation of the electromagnetic stirrer - restarting the identification process - restarting the operation of the electromagnetic stirrer;

[0023] (5) Provide auxiliary judgment criteria for changes in the risk level of steel leakage based on the operating data of the electromagnetic stirrer.

[0024] In the step (1), the identification data includes impedance parameters and time constants in a conventional motor identification process; for electromagnetic stirring at the end of solidification and electromagnetic stirring in the second cooling stage, corresponding identification data of the completely solidified ingot is obtained and saved for comparison.

[0025] In the step (2), the stability of the identification data refers to the range of ±5% of the variation amplitude; the operating parameters of the electromagnetic stirrer include the values ​​of voltage, current, frequency, active power and reactive power, as well as the excitation current component and torque current component and their variation trends.

[0026] In the step (3), the electromagnetic stirrer is driven by a frequency converter or variable frequency power supply device with a vector control function. The vector control function is a mature technology applied to variable frequency speed regulation devices.

[0027] In the step (5), an auxiliary criterion for the change in the risk level of steel leakage is provided based on the operating data of the electromagnetic stirrer, and the judgment is based on the following: when the arc position of the electromagnetic stirrer remains unchanged, the change in the torque current component during operation means that the liquid phase of the casting billet changes. An increase in the torque current indicates that the shell of the continuous casting billet becomes thinner, there is a problem with cooling, and the risk of steel leakage increases.

[0028] The beneficial effects of the present invention are: by combining and applying mature vector control technology, the excitation current and stirring force are measured and controlled in real time, the stirring force is directly controlled, the electromagnetic stirring effect is improved, and the blind increase of the voltage and current of the electromagnetic stirrer causing additional energy loss and equipment overheating is avoided, thereby achieving energy-saving and efficient operation, and can also provide auxiliary criteria for changes in the risk level of steel leakage during the steel drawing process of the continuous casting machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural block diagram of the present invention;

[0030] Figure 2 The work flow chart of the present invention;

[0031] The markings in the figure are as follows: stator support seat 1, rotor support seat 2, rotatable device 3, dummy shaft round tube 4, dummy shaft flange 5, stator 6, rotor 7, wire rope 8, stator moving direction 9. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the invention implementation cases clearer, the technical solutions in the implementation cases of the present invention will be clearly and completely described below in conjunction with the drawings in the implementation cases. Obviously, the implementation cases described are only a small part of the implementation cases of the present invention, rather than all the implementation cases. Based on the implementation cases in the present invention, all other implementation cases obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] A control method for a rotary electromagnetic stirrer of a continuous casting machine comprises the following steps:

[0034] (1) After the casting process begins, the electromagnetic parameter identification of the electromagnetic stirrer is started multiple times to obtain and save the identification data corresponding to different liquid phase ratios of the ingot;

[0035] (2) Each time the new identification data is compared with the previous one, the identification process is stopped when the identification data is stable, that is, the liquid phase ratio is fixed, and the electromagnetic stirrer is started to run at the frequency required by the process; the operating parameters of the electromagnetic stirrer are measured and recorded through the PLC and the host computer;

[0036] (3) The vector control function is used to achieve the stirring frequency required by the output process, control the upper limit of the torque current, and limit the excitation current component to avoid oversaturation of the magnetic circuit;

[0037] (4) In the case of continuous casting of different steel grades or changing the cooling system, a candidate operation is provided: suspending the operation of the electromagnetic stirrer - restarting the identification process - restarting the operation of the electromagnetic stirrer;

[0038] (5) Provide auxiliary judgment criteria for changes in the risk level of steel leakage based on the operating data of the electromagnetic stirrer.

[0039] In the step (1), the identification data includes impedance parameters and time constants in a conventional motor identification process; for electromagnetic stirring at the end of solidification and electromagnetic stirring in the second cooling stage, corresponding identification data of the completely solidified ingot is obtained and saved for comparison.

[0040] In the step (2), the stability of the identification data refers to the range of ±5% of the variation amplitude; the operating parameters of the electromagnetic stirrer include the values ​​of voltage, current, frequency, active power and reactive power, as well as the excitation current component and torque current component and their variation trends.

[0041] In the step (3), the electromagnetic stirrer is driven by a frequency converter or variable frequency power supply device with a vector control function. The vector control function is a mature technology applied to variable frequency speed regulation devices.

[0042] In the step (5), an auxiliary criterion for the change in the risk level of steel leakage is provided based on the operating data of the electromagnetic stirrer, and the judgment is based on the following: when the arc position of the electromagnetic stirrer remains unchanged, the change in the torque current component during operation means that the liquid phase of the casting billet changes. An increase in the torque current indicates that the shell of the continuous casting billet becomes thinner, there is a problem with cooling, and the risk of steel leakage increases.

[0043] In practical applications, the implementation of the present invention includes three aspects: hardware, software, and operation:

[0044] (1) Hardware: including the electromagnetic stirrer body (in compliance with the national standard GB / T 33546-2017); inverter or variable frequency power supply with vector control function; external parameter measurement instruments (current, power, etc., energy efficiency comparison); communication with the continuous casting machine automatic control system (obtaining operation instructions, tundish temperature, start and stop status of the casting strand, casting speed, cooling formula selection and other data; transmitting real-time data such as the working frequency, operating current, stirring intensity of the electromagnetic stirrer); communication with the quality inspection system (obtaining quality judgment results such as sulfur print data).

[0045] (2) Software: including but not limited to the following items: realizing real-time operation parameter monitoring and trend data query functions of electromagnetic stirrers; calculating the length of the ingot according to the casting state and the casting speed and automatically starting the identification according to the ingot length; realizing the preservation and comparison of identification data; automatically completing the system safety check (including insulation, cooling system, etc.) before starting the electromagnetic stirrer; automatically completing the intelligent judgment of the change of steel leakage risk level; completing the energy efficiency analysis of the electromagnetic stirrer (real-time power and accumulated electric energy data stage comparison) and providing the historical data of the electromagnetic stirrer operation for quality improvement effect evaluation and analysis (compared with the continuous casting ingot quality inspection data).

[0046] (3) Operation: including providing remote and machine-side operation interfaces; setting the identification process (including: a. whether to set the identification before pouring: for the electromagnetic stirrer in the second cooling section and the end of solidification, there are rigid or flexible guide rods in the stirrer; for the electromagnetic stirrer of the crystallizer, the identification before pouring cannot be started because there is cold material in the crystallizer at this time. b. setting the identification after pouring: set according to the casting length to ensure that the time interval between two adjacent identifications is more than 2 minutes); restart the identification as needed; restart the operation, etc.

[0047] Finally, it should be noted that the above description is 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, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A control method for a rotary electromagnetic stirrer of a continuous casting machine, characterized in that The following steps are involved: (1) After the casting process begins, the electromagnetic parameter identification of the electromagnetic stirrer is started multiple times to obtain and save the identification data corresponding to different liquid phase ratios of the ingot; (2) Each time the new identification data is compared with the previous one, the identification process is stopped when the identification data is stable, that is, the liquid phase ratio is fixed, and the electromagnetic stirrer is started to run at the frequency required by the process; the operating parameters of the electromagnetic stirrer are measured and recorded through the PLC and the host computer; (3) The vector control function is used to achieve the stirring frequency required by the output process, control the upper limit of the torque current, and limit the excitation current component to avoid oversaturation of the magnetic circuit; (4) In the case of continuous casting of different steel grades or changing the cooling system, a candidate operation is provided: suspending the operation of the electromagnetic stirrer - restarting the identification process - restarting the operation of the electromagnetic stirrer; (5) Provide auxiliary criteria for changes in the risk level of steel leakage based on the operating data of the electromagnetic stirrer; In the step (1), the identification data includes impedance parameters and time constants in the conventional motor identification process; for the electromagnetic stirring at the end of solidification and the electromagnetic stirring at the second cooling stage, the corresponding identification data of the completely solidified ingot is obtained and saved for comparison; In the step (2), the stability of the identification data refers to the range of ±5% of the variation amplitude; the operating parameters of the electromagnetic stirrer include the values ​​of voltage, current, frequency, active power and reactive power, and the excitation current component and torque current component and their variation trends; In the step (5), an auxiliary criterion for the change in the risk level of steel leakage is provided based on the operating data of the electromagnetic stirrer, and the judgment is based on the following: when the arc position of the electromagnetic stirrer remains unchanged, the change in the torque current component during operation means that the liquid phase of the casting billet changes. An increase in the torque current indicates that the shell of the continuous casting billet becomes thinner, there is a problem with cooling, and the risk of steel leakage increases.

2. The control method of a rotary electromagnetic stirrer of a continuous casting machine according to claim 1, characterized in that: In the step (3), the electromagnetic stirrer is driven by a frequency converter or variable frequency power supply device with a vector control function. The vector control function is a mature technology applied to variable frequency speed regulation devices.

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