Induction heating system and control method thereof, and continuous casting machine

Abstract

The present invention discloses an induction heating system, a control method thereof, and a continuous casting machine. The system includes a first induction heating unit, a second induction heating unit, a first power supply, a second power supply, and a control device. The first power supply is connected to the first induction heating unit, the second power supply is connected to the second induction heating unit, and the control device is connected to the first and second power supplies. The control device calculates the shell thickness of the cast slab at the first and second induction heating units and controls the frequency of the first and second power supplies based on the shell thickness, thereby controlling the skin depth of the induced current generated by the first and second induction heating units. The present invention solves the problem of cracking during the cast slab deformation process and the problem of low temperature control accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of continuous casting billet heating, and in particular relates to an induction heating system applied to a continuous casting machine, a control method thereof, and a continuous casting machine. Background Art

[0002] Steel production generally includes traditional die casting, semi-continuous casting, and continuous casting. Since the production efficiency of die casting and semi-continuous casting is much lower than that of continuous casting, a considerable portion of steel products have been converted from die casting and semi-continuous casting to continuous casting. After converting to continuous casting, cracks during bending and straightening have become a major problem that needs to be solved urgently.

[0003] In continuous casting production lines, molten steel is poured vertically into billets that are ultimately transported horizontally, forcing them to pass through curved sections. The billets undergo two bending and straightening stages, both when they pass from the vertical section into the curved section and when they pass from the curved section into the horizontal section. The overall temperature distribution of the billet during these two bending and straightening stages is characterized by lower surface temperatures and higher core temperatures. These bending and straightening stages occur at different stages, resulting in different states and forms. When the billet passes from the vertical section into the curved section, the overall temperature is relatively high, the shell is thinner, and the proportion of molten steel in the cross-section is higher. When the billet passes from the curved section into the horizontal section, the overall temperature is lower, and the shell increases due to the continuous solidification of the molten steel, reducing the proportion of molten steel in the cross-section. Furthermore, the slower the casting speed during production (for a given production capacity, the larger the cross-sectional specifications of the billet, the slower the casting speed), the lower the overall temperature and the thicker the shell. During the continuous casting stage, the temperature of the billet decreases continuously from the front to the back of the casting line, while the shell thickness increases continuously until the central molten steel completely solidifies, forming a fully solid billet. Before bending and straightening the billet, a certain shell thickness must be maintained to prevent steel leakage during the bending and straightening process due to an excessively thin shell, which could cause serious safety accidents. Furthermore, if the shell is too thick, the billet temperature will be lower, resulting in greater forces required for bending and straightening, requiring more powerful mechanical equipment. Furthermore, when the shell is thicker and the temperature is lower, defects such as surface cracking are more likely to occur during the bending and straightening process due to insufficient plasticity.

[0004] Since the 21st century, the rapid development of domestic industries such as wind power generation, high-speed rail, and construction machinery has driven demand for raw materials to become increasingly demanding, with a focus on scale, large-scale production, and high-end production. This has led to a growing demand for larger, more reliable, and more stable cross-section billets (such as wind turbine flanges). The production of large-section billets requires lower drawing speeds, thicker shells before bending and straightening, and greater deformation, which can easily lead to surface cracking.

[0005] At present, the main means of temperature control in the continuous casting process is full water cooling, mist cooling or natural cooling, and the ingots are kept warm by using a heat shield. There is no supplementary heating method or equipment, and traditional supplementary heating equipment is almost impossible to place on the production line. This temperature control method has the following drawbacks:

[0006] On the one hand, although the thickness of the billet shell and the temperature of the ingot can be guaranteed (the surface temperature of the ingot can be lowered) by adjusting the amount of cooling medium, the temperature control accuracy is low; on the other hand, when producing different steel grades, different cross-sectional specifications and different production processes, the control of the cooling medium needs to be constantly adjusted. The control is complex and difficult, and quality defects (such as cracks) often occur due to inaccurate control of the cooling medium amount. It is difficult to ensure that the same amount of cooling medium can be controlled to ensure the production of ingots at different times, different steel grades and different production processes.

[0007] Electromagnetic induction heating offers a range of advantages, including fast heating and high production efficiency; minimal oxidation damage and high steel yield; precise temperature control; utilizing the workpiece's own eddy currents to generate heat, requiring no fuel or pollution; and a compact system with a small footprint. Due to its inherent advantages and compatibility with steel metallurgy, electromagnetic induction heating technology is poised to become a trend in heating ingots prior to bending and straightening. Currently, a small number of international steel companies are using induction heating technology for billet bending and straightening, but this area remains largely unexplored in China. Summary of the Invention

[0008] The purpose of the present invention is to provide an induction heating system and its control method, and a continuous casting machine, so as to solve the problem of low temperature control accuracy caused by adjusting the cooling medium to ensure the temperature of the casting in the casting process, and the problem of not being able to ensure high-quality production of castings under different times, different steel grades and different production processes by controlling the same cooling medium.

[0009] The present invention solves the above technical problems through the following technical solutions: an induction heating system is applied to a continuous casting machine, wherein the machine curve of the continuous casting machine includes a vertical section, a curved section, an arc section and a straightening section in sequence, and the induction heating system comprises:

[0010] a first induction heating unit provided at the end of the vertical section or the front end of the curved section, the first induction heating unit being used to heat the billet before it enters the curved section from the vertical section;

[0011] A second induction heating unit is provided at the end of the arc segment or the front end of the straightening segment, and the second induction heating unit is used to heat the billet before it enters the straightening segment from the arc segment;

[0012] a first power supply device for supplying power to the first induction heating unit, wherein the power modules in the first power supply device correspond one-to-one to the induction heaters in the first induction heating unit;

[0013] a second power supply device for supplying power to the second induction heating unit, wherein the power modules in the second power supply device correspond one-to-one to the induction heaters in the second induction heating unit;

[0014] a control device connected to the first power supply device and the second power supply device respectively, wherein the control device is used to calculate the shell thickness of the ingot at the first induction heating unit and the second induction heating unit, and control the frequency of the first power supply device and the second power supply device according to the shell thickness of the ingot, thereby controlling the skin depth of the induced current generated by the first induction heating unit and the second induction heating unit.

[0015] The control device of the present invention calculates the shell thickness of the ingot for different steel grades at different continuous casting line positions, and controls the frequency of the first power supply device and the second power supply device according to the shell thickness of the ingot, thereby controlling the skin depth of the induced current generated by the first induction heating unit and the second induction heating unit. When the ingot is inductively heated, the influence of eddy current heat on the temperature of the molten steel and the production process of the entire production line can be reduced or avoided, thereby avoiding the problem of cracks in the deformation process of the ingot, and ensuring the high-quality production of the ingot at different times, different steel grades and different production processes.

[0016] Furthermore, the second induction heating unit includes N induction heaters, and the widths of the N induction heaters are from small to large, wherein the first induction heater is close to the arc segment and has the smallest width, and the Nth induction heater is close to the straightening segment and has the largest width.

[0017] Furthermore, the width of the induction heater in the first induction heating unit is smaller than the width of the first induction heater in the second induction heating unit.

[0018] Furthermore, the induction heating system further comprises:

[0019] a first temperature detection unit provided at the front end of the first induction heating unit and used to detect the temperature of the billet before it enters the bending section;

[0020] a second temperature detection unit provided at the front end of the second induction heating unit and used to detect the temperature of the billet before it enters the straightening section;

[0021] The control device is connected to the first temperature detection unit and the second temperature detection unit, and is further used to control the first induction heating unit to be turned on according to the steel grade information of the cast billet, and to control the operating power of the first induction heating unit through the first power supply device according to the temperature detected by the first temperature detection unit and the first target temperature, and to control the operating power of the second induction heating unit through the second power supply device according to the temperature detected by the second temperature detection unit and the second target temperature;

[0022] The front end of the first induction heating unit refers to an end close to the vertical segment, and the front end of the second induction heating unit refers to an end close to the arc segment.

[0023] Furthermore, the second temperature detection unit includes N temperature sensors, the N temperature sensors correspond one-to-one to the N induction heaters in the second induction heating unit, and each temperature sensor is provided at the front end of the corresponding induction heater;

[0024] The control device is further configured to control the operating power of the corresponding induction heater in the second induction heating unit according to the second target temperature and the temperature detected by each temperature sensor.

[0025] Furthermore, the induction heating system also includes a cooling water device, which includes multiple cooling units. The number of cooling units is equal to the sum of the number of induction heaters in the first induction heating unit and the second induction heating unit, and the number of power modules in the first power supply device and the second power supply device. The cooling unit is used to cool the corresponding induction heater or power module.

[0026] Based on the same inventive concept, the present invention further provides a control method for the induction heating system as described above, comprising the following steps:

[0027] Calculating the shell thickness of the casting slab at the first induction heating unit and the second induction heating unit;

[0028] The frequencies of the first power supply device and the second power supply device are controlled according to the thickness of the cast billet shell, thereby controlling the skin depth of the induced current generated by the first induction heating unit and the second induction heating unit.

[0029] Furthermore, the shell thickness of the ingot is the smaller value between the theoretical thickness and the predicted thickness. The predicted thickness is predicted by the continuous casting solidification model. The calculation formula of the theoretical thickness is:

[0030]

[0031] Wherein, δ1 is the theoretical thickness, K is the solidification coefficient, t is the solidification time, l is the distance from the meniscus to the first induction heating unit or the second induction heating unit, and v is the billet drawing speed.

[0032] Furthermore, the relationship between the skin depth of the induced current and the frequency of the first power supply device or the second power supply device is:

[0033]

[0034] Among them, δ0 is the skin depth of the induced current, μ0 is the relative magnetic permeability of air, and μ r is the relative magnetic permeability of the ingot, σ is the electrical conductivity of the ingot, ω is the angular frequency of the first power supply device or the second power supply device, and f is the operating frequency of the first power supply device or the second power supply device.

[0035] Furthermore, the skin depth of the induced current is smaller than the shell thickness of the ingot.

[0036] Furthermore, the control method further includes:

[0037] Acquire steel grade information of the ingot and temperatures detected by the first temperature detection unit and the second temperature detection unit;

[0038] Controlling the first induction heating unit to start according to the steel grade information of the ingot, and controlling the operating power of the first induction heating unit through the first power supply device according to the temperature detected by the first temperature detection unit and the first target temperature;

[0039] The operating power of the second induction heating unit is controlled by the second power supply device according to the temperature detected by the second temperature detection unit and the second target temperature.

[0040] Furthermore, the calculation formula for the operating power of the first induction heating unit or the second induction heating unit is:

[0041]

[0042] Wherein, P is the operating power or heating power of the first induction heating unit or the second induction heating unit; C is the specific heat capacity of the ingot; m is the mass of the ingot transmitted per unit time, and the mass of the ingot refers only to the mass of the ingot within the skin depth of the induced current generated by the first induction heating unit or the second induction heating unit; ΔT is the difference between the target temperature and the initial temperature, the target temperature is the first target temperature or the second target temperature, and the initial temperature is the temperature detected by the first temperature detection unit or the second temperature detection unit; η is the heating efficiency; ε is the skin depth coefficient.

[0043] Furthermore, the specific process of sequentially controlling the operating power of the N induction heaters in the second induction heating unit is as follows:

[0044] When the second target temperature T 2m The temperature T detected by the first temperature sensor 21When the difference is greater than the temperature that can be raised by the first induction heater running at full power, the first induction heater runs at full power; when the second target temperature T 2m The temperature T detected by the first temperature sensor 21 When the difference is less than or equal to the temperature that can be raised by the first induction heater at full power, the first induction heater will raise the billet from the temperature T 21 Heating to the second target temperature T 2m Power required to operate;

[0045] When the second target temperature T 2m The temperature detected by the second temperature sensor T 22 When the difference is greater than the temperature that can be raised by the second induction heater running at full power, the second induction heater runs at full power; when the second target temperature T 2m The temperature detected by the second temperature sensor T 22 When the temperature is less than or equal to the temperature that can be raised by the second induction heater at full power, the second induction heater will raise the billet from the temperature T 22 Heating to the second target temperature T 2m Power required to operate;

[0046] Similarly, when the second target temperature T 2m The temperature T detected by the i-th temperature sensor 2i When the difference is greater than the temperature that can be raised by the full power operation of the i-th induction heater, the i-th induction heater operates at full power until the second target temperature T 2m The temperature T detected by the i-th temperature sensor 2i Less than or equal to the temperature that can be raised by the i-th induction heater running at full power; when the second target temperature T 2m The temperature T detected by the i-th temperature sensor 2i When the temperature is less than or equal to the temperature that can be raised by the full power operation of the i-th induction heater, the i-th induction heater will raise the billet from the temperature T 2i Heating to the second target temperature T 2m Power required to operate;

[0047] Among them, the first induction heater refers to the induction heater close to the arc segment.

[0048] Furthermore, when the n induction heaters make the temperature of the billet reach the second target temperature T 2m , and when n<N, (n+1) to (N-1) induction heaters are controlled not to work, and the Nth induction heater is controlled to perform temperature compensation on the ingot.

[0049] Furthermore, the control method further includes:

[0050] Obtain the inlet and outlet water temperatures of each cooling unit, the power of each induction heater or each power module;

[0051] The inlet and outlet water flow of the cooling unit is controlled according to the inlet and outlet water temperatures of the cooling unit and the power of the corresponding induction heater or power module. The specific control formula is:

[0052] P w (1-η w )·ζ=C 水 m 水 (T 出 -T 进 )

[0053] Among them, P w is the power of the induction heater or power module; η w is the heating efficiency or power supply efficiency; ζ is the safety factor; C 水 is the specific heat capacity of water, m 水 T is the water flow per unit time; 出 is the outlet water temperature of the cooling unit; T 进 is the inlet water temperature of the cooling unit.

[0054] Based on the same inventive concept, the present invention further provides a continuous casting machine, which includes the induction heating system as described above.

[0055] Beneficial effects

[0056] Compared with the prior art, the advantages of the present invention are:

[0057] The present invention provides an induction heating system, a control method thereof, and a continuous casting machine. The frequencies of the first power supply device and the second power supply device are controlled according to the shell thickness of the ingot of different steel grades at different positions on the continuous casting line, thereby controlling the skin depth of the induced current generated by the first induction heating unit and the second induction heating unit. When the ingot is inductively heated, the influence of eddy current heat on the temperature of the molten steel and the production process of the entire production line can be reduced or avoided, thereby avoiding the problem of shell cracks in the ingot during the deformation process, improving the product qualification rate and product quality, and ensuring the high-quality production of the ingot at different times, different steel grades, and different production processes.

[0058] The present invention accurately controls the operating power of the first induction heating unit and the second induction heating unit according to the temperatures detected by the first temperature detection unit and the second temperature detection unit, thereby realizing heating temperature control for different steel grades and different positions, greatly improving the temperature control accuracy, ensuring the required temperature during the deformation process of the ingot, further avoiding the problem of shell cracks in the ingot during the deformation process, and at the same time ensuring the effective use of electric energy, saving heating costs, and having green and environmentally friendly characteristics.

[0059] The control method of the present invention is relatively simple, has high controllability and convenience, and improves the stability of the continuous casting process. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0061] Figure 1 1 is a schematic structural diagram of an induction heating system applied to a continuous casting machine according to an embodiment of the present invention;

[0062] Figure 2 1 is a layout diagram of the first induction heating unit and the second induction heating unit on the model curve in an embodiment of the present invention;

[0063] Figure 3 1 is a control circuit diagram of an induction heating system according to an embodiment of the present invention, wherein the double-dotted line is a control line and the dotted line is a powered cable;

[0064] Figure 4 Schematic diagram of the mass m of the cast billet transferred per unit time in an embodiment of the present invention;

[0065] Figure 5 1 is a schematic structural diagram of an induction heater according to an embodiment of the present invention;

[0066] FIG6( a ) is a front view of an induction heater according to an embodiment of the present invention;

[0067] FIG6( b ) is a side view of the induction heater according to an embodiment of the present invention;

[0068] FIG6( c ) is a top view of the induction heater according to an embodiment of the present invention;

[0069] Figure 7 is a structural diagram of an induction coil of an induction heater in an embodiment of the present invention;

[0070] Figure 8 1 is a control flow chart of the induction heating system in an embodiment of the present invention.

[0071] Among them, 1-first power supply device, 2-control device, 3-second temperature detection unit, 4-second power supply device, 5-cooling water device, 6-second induction heating unit, 61-first induction heater in the second induction heating unit, 611-annular shell, 612-first energized busbar / second energized busbar, 613-insulating plate, 614-water inlet box / water outlet box, 615-casting material, 616-induction coil, 7-casting billet, 8-first induction heating unit, 81-induction heater in the first induction heating unit. DETAILED DESCRIPTION

[0072] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0073] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0074] During the continuous casting process, the billet enters the curved section from the initial vertical section, and then from the curved section to the horizontal section. During these two transition stages, the billet must undergo plastic deformation to ensure it can be turned from a vertical to a horizontal orientation. When the vertical section enters the curved section, the billet's temperature is higher and its plasticity is better, making it easier to bend the billet. However, for some highly crack-sensitive steel grades, surface cracking or fissures are more likely to occur during this stage. When the billet enters the horizontal section from the curved section, the billet's temperature is lower and its plasticity is poorer, requiring greater mechanical force for straightening. The most difficult to avoid is surface cracking or fissures during the straightening process. This is especially true when producing billets with large cross-sections, where the likelihood and frequency of surface cracks are greater.

[0075] Currently, in continuous casting production, the bending deformation and straightening temperature of the ingot are mainly controlled by water cooling, mist cooling, natural air cooling, and related insulation devices (insulation covers), without any heating or supplemental heat methods or equipment. Water cooling requires high control of the total water volume. The amount of water directly acting on the ingot and performing the cooling function cannot be controlled at every point, making precise temperature control impossible. Furthermore, the existing temperature control methods are also affected by the ambient temperature. The amount of cooling medium and related production processes must be adjusted according to the ambient temperature, making the operation complex and uncontrollable.

[0076] Based on the above technical issues, such as Figures 1 to 3As shown, an embodiment of the present invention provides an induction heating system for a continuous casting machine, wherein the machine curve of the continuous casting machine includes a vertical section, a curved section, an arc section and a straightening section (such as Figure 2 As shown), the induction heating system includes a first induction heating unit 8, a second induction heating unit 6, a first power supply device 1, a second power supply device 4 and a control device 2; the first power supply device 1 is connected to the first induction heating unit 8, the second power supply device 4 is connected to the second induction heating unit 6, and the control device 2 is connected to the first power supply device 1 and the second power supply device 4.

[0077] The first induction heating unit 8 is provided at the end of the vertical section or the front end of the curved section, and is used to heat the billet before it enters the curved section from the vertical section. Since the overall temperature of the billet at the end of the vertical section or the front end of the curved section is higher and the billet shell is thinner, the first induction heating unit 8 is mainly used to heat crack-sensitive steel grades, and a smaller number of induction heaters can be used. The second induction heating unit 6 is provided at the end of the circular arc section or the front end of the straightening section, and is used to heat the billet before it enters the straightening section from the circular arc section. Since the overall temperature of the billet at the end of the circular arc section or the front end of the straightening section is lower, and the closer the billet shell is to the end of the circular arc section, the thicker the billet shell is, one, two or more induction heaters of different sizes or the same size can be matched according to different billet steel grades.

[0078] In this embodiment, the first induction heating unit 8 includes one induction heater, and the second induction heating unit 6 includes N induction heaters (N=4).

[0079] The first power supply device 1 is used to supply power to the first induction heating unit 8, and the second power supply device 4 is used to supply power to the second induction heating unit 6. To independently supply power to the induction heaters in the first induction heating unit 8 and the second induction heating unit 6, the first power supply device 1 includes the same number of power modules as the number of induction heaters in the first induction heating unit 8, and the second power supply device 4 includes the same number of power modules as the number of induction heaters in the second induction heating unit 6. In this embodiment, the first power supply device 1 includes one power module (corresponding to the one induction heater in the first induction heating unit), and the second power supply device 4 includes N power modules (corresponding to the N induction heaters in the second induction heating unit), each of which independently supplies power to its corresponding induction heater.

[0080] The control device 2 is used to calculate the shell thickness of the ingot at the first induction heating unit 8 and the second induction heating unit 6, and control the frequency of the first power supply device 1 and the second power supply device 4 according to the shell thickness of the ingot, thereby controlling the skin depth of the induced current generated by the first induction heating unit 8 and the second induction heating unit 6.

[0081] In order to reduce or avoid the impact of eddy current heat on the temperature of the molten steel and the production process of the entire production line when the ingot is induction heated, and to avoid the problem of ingot cracks, the thickness of the ingot shell is the smaller value between the theoretical thickness δ1 and the predicted thickness δ2, wherein the predicted thickness δ2 is predicted by the continuous casting solidification model stored in the control device 2. The continuous casting solidification model is designed during the production of the continuous casting line, and the specific design process is the existing technology. According to the continuous casting solidification model, the shell thickness of different steel grades, different casting speeds and different continuous casting line positions can be predicted. In this embodiment, the calculation formula for the theoretical thickness of the ingot shell is:

[0082]

[0083] Wherein, δ1 is the theoretical thickness, K is the solidification coefficient, t is the solidification time, l is the distance from the meniscus to the first induction heating unit 8 or the second induction heating unit 6, and v is the casting speed.

[0084] The meniscus refers to the location where the continuous casting slab begins to solidify and form the primary shell, typically located at the front end of the vertical section. For example, to calculate the theoretical thickness of the slab shell at the induction heater in the first induction heating unit 8, the distance from the meniscus to the induction heater in the first induction heating unit 8 is used; to calculate the theoretical thickness of the slab shell at the first induction heater 61 in the second induction heating unit 6, the distance from the meniscus to the first induction heater 61 in the second induction heating unit 6 is used.

[0085] The smaller of the theoretical thickness δ1 and the predicted thickness δ2 is used as a basis for controlling the operating frequency of the first power supply unit 1 or the second power supply unit 4 to ensure that the skin depth δ0 of the induced current generated by the induction heater is less than the smaller of the theoretical thickness δ1 and the predicted thickness δ2. This reduces or eliminates the effect of eddy current heat on the temperature of the molten steel during induction heating of the ingot. In this embodiment, the skin depth δ0 of the induced current is 1 / 2 to 4 / 5 of the shell thickness of the ingot.

[0086] The installation position of the induction heater is different, and the thickness of the billet shell is different. The operating frequency of the induction heater corresponding to different billet shell thicknesses is different. The thicker the billet shell thickness, the lower the corresponding operating frequency of the induction heater, and the thinner the billet shell thickness, the higher the corresponding operating frequency of the induction heater. In order to avoid cracking problems, the depth of action of the induced current generated by the induction heater (i.e., the skin depth) is controlled to ensure that the skin depth δ0 is 1 / 2 to 4 / 5 of the billet shell thickness. The relationship between the skin depth of the induced current generated by the induction heater and the frequency of the corresponding power module in the first power supply device 1 or the second power supply device 4 is:

[0087]

[0088] Right now

[0089] Among them, δ0 is the skin depth of the induced current, μ0 is the relative magnetic permeability of air, and μ r is the relative magnetic permeability of the ingot, σ is the electrical conductivity of the ingot, ω is the angular frequency of the first power supply unit 1 or the second power supply unit 4, and f is the operating frequency of the first power supply unit 1 or the second power supply unit 4. For example, δ0 is the skin depth of the induced current generated by the first induction heater 61 in the second induction heating unit 6, and f is the operating frequency of the power module corresponding to the induction heater. Since the induction heater is controlled by the power module, the power module and the corresponding induction heater have the same frequency.

[0090] The closer to the solidification end of the billet, the thicker the billet shell thickness and the lower the billet temperature. In order to ensure the heating power or operating power of the induction heater and the heating time of the billet, the closer to the solidification end of the billet, the wider the induction heater, that is, the closer to the solidification end, the more turns of the induction heater coil. Conversely, the farther away from the solidification end, the fewer turns of the induction heater coil. Figure 1 As shown, the widths of the N induction heaters in the second induction heating unit 6 are arranged in ascending order, with the first induction heater 61 being close to the arc section and having the smallest width, and the Nth induction heater being close to the straightening section and having the largest width. The width of the induction heater 81 in the first induction heating unit 8 is smaller than the width of the first induction heater 61 in the second induction heating unit 6. The fewer turns of the induction heater coil, the higher the frequency output can be at the required power. The higher the frequency, the better it satisfies the relationship between skin depth and billet shell thickness, the better it can adapt to billet shell thickness, and the better it can match the required frequency with the power output.

[0091] After determining the operating frequency of the induction heater based on the thickness of the billet shell, the number of turns in each induction heater's induction coil must ensure the required operating power or heating power output within the known operating frequency range. As the billet shell thickens as it approaches the horizontal section, a lower operating frequency is required to ensure that the induction current heats the billet shell at a certain skin depth. This can be achieved by increasing the number of turns in the induction coil. This not only allows for matching the rated power, but also increases the width of the induction heater, thereby increasing the heating time of the billet and ensuring a temperature increase.

[0092] The solidification end of the ingot is the point where the front of the molten steel in the center of the cross section solidifies into a solid state during ingot production. The width of the induction heater is the axial length of the inductor bore, that is, the length of the ingot in the induction heater during the ingot conveying process.

[0093] During billet production, the pouring temperature of molten steel is low, and the billet shell that needs to be heated is thicker. When there is no need to match the skin depth, the width of the induction heater can be consistent, that is, the induction heaters can be interchangeable to simplify the composition of the equipment and system.

[0094] In a specific embodiment of the present invention, the induction heating system further includes a first temperature detection unit and a second temperature detection unit 3 ; the first temperature detection unit and the second temperature detection unit 3 are connected to the control device 2 respectively.

[0095] A first temperature detection unit is located at the front end of the first induction heating unit 8 and is used to detect the temperature of the billet before it enters the bending section. A second temperature detection unit 3 is located at the front end of the second induction heating unit 6 and is used to detect the temperature of the billet before it enters the straightening section. The control device 2 is further used to control the activation of the first induction heating unit 8 based on the steel grade information of the billet, and to control the operating power of the first induction heating unit 8 via the first power supply 1 based on the temperature detected by the first temperature detection unit and the first target temperature, and to control the operating power of the second induction heating unit 6 via the second power supply 4 based on the temperature detected by the second temperature detection unit 3 and the second target temperature. The front end of the first induction heating unit 8 refers to the end near the vertical section, and the front end of the second induction heating unit 6 refers to the end near the arc section. The first target temperature is the temperature required for the billet to avoid cracking or fissures during the first deformation stage (from vertical to bending), and the second target temperature is the temperature required for the billet to avoid cracking or fissures during the second deformation stage (from arc to straightening).

[0096] When the ingot is a crack-sensitive steel or the ingot temperature is too low to reach the target temperature for deformation without cracking, the first induction heating unit 8 is required for heating. In other cases, the first induction heating unit 8 does not heat. Regardless of the steel type, the second induction heating unit 6 needs to heat, but the heating power required varies depending on the ingot temperature. In this embodiment, the operating power of the first induction heating unit 8 or the second induction heating unit 6 is calculated as follows:

[0097]

[0098] Among them, P is the operating power or heating power of the first induction heating unit 8 or the second induction heating unit 6; C is the specific heat capacity of the ingot; m is the mass of the ingot transmitted per unit time, and the mass of the ingot only refers to the mass of the ingot of the skin depth part of the induced current generated by the first induction heating unit 8 or the second induction heating unit 6; ΔT is the difference between the target temperature and the initial temperature, the target temperature is the first target temperature or the second target temperature, and the initial temperature is the temperature detected by the first temperature detection unit or the temperature detected by the second temperature detection unit 3; η is the heating efficiency; ε is the skin depth coefficient.

[0099] Exemplarily, P is the operating power or heating power of the second induction heating unit 6, and ΔT is the difference between the second target temperature and the temperature detected by the second temperature detection unit 3. The second induction heating unit 6 includes N induction heaters, and the temperature detected by the second temperature detection unit 3 is the temperature at the front end of the first induction heater 61 in the second induction heating unit 6. Then, P is the sum of the operating power or heating power of the N induction heaters.

[0100] m is the mass of the cast billet transferred per unit time, and the mass of the cast billet refers only to the mass of the cast billet within the skin depth of the induced current generated by the first induction heating unit 8 or the second induction heating unit 6, such as Figure 4 The black filled area shown is shown in Figure 1, where H1 is the outer diameter of the ingot, H2 is the outer diameter of the molten steel area, and δ is the shell thickness of the ingot. m is related to the ingot drawing speed, which is in turn related to the width of the induction heater, i.e., L = νt, where L is the width of the induction heater, ν is the ingot drawing speed (the speed at which the ingot moves within the induction heater), and t is the heating time within the corresponding induction heater. The higher the required heating temperature and the faster the drawing speed, the more induction heaters operating in the second induction heating unit 6, the greater the heating power, and the wider the induction heaters.

[0101] The number of temperature sensors in the first temperature detection unit is the same as the number of induction heaters in the first induction heating unit 8, and the number of temperature sensors in the second temperature detection unit 3 is the same as the number of induction heaters in the second induction heating unit 6. In this embodiment, if the number of induction heaters in the first induction heating unit 8 is 1, then the number of temperature sensors in the first temperature detection unit is 1; if the number of induction heaters in the second induction heating unit 6 is N, then the number of temperature sensors in the second temperature detection unit 3 is N. Each temperature sensor is located at the front end of its corresponding induction heater.

[0102] The full power or rated power of the induction heater in the first induction heating unit 8 should be greater than or equal to the power required to heat the cast billet from the temperature detected by the first temperature detection unit to the first target temperature; the sum of the full power or rated power of the N induction heaters in the second induction heating unit 6 should be greater than or equal to the power required to heat the cast billet from the temperature detected by the first temperature sensor in the second temperature detection unit 3 to the second target temperature. The control device 2 can also control the operating power of the corresponding induction heater in the second induction heating unit 6 based on the second target temperature and the temperature detected by each temperature sensor in the second temperature detection unit 3.

[0103] In a specific embodiment of the present invention, the induction heating system further includes a cooling water device 5, which includes a plurality of cooling units. The number of cooling units is equal to the sum of the number of induction heaters in the first induction heating unit 8 and the second induction heating unit 6, and the number of power modules in the first power supply device 1 and the second power supply device 4. The cooling unit is used to cool the corresponding induction heater or power module.

[0104] In this embodiment, the first induction heating unit 8 includes one induction heater, the second induction heating unit 6 includes N induction heaters, the first power supply device 1 includes one power module, and the second power supply device 4 includes N power modules. Therefore, the number of cooling units is 2N+2. In this embodiment, the control device 2 controls the inlet and outlet water flow of the cooling unit based on the inlet and outlet water temperature of the cooling unit and the power of the corresponding induction heater or power module. The specific control formula is:

[0105] P w (1-η w )·ζ=C 水 m 水 (T 出 -T 进 ) (5)

[0106] Among them, P w is the power of the induction heater or power module; η w is the heating efficiency or power supply efficiency; ζ is the safety factor; C 水 is the specific heat capacity of water, m 水 T is the water flow per unit time; 出 is the outlet water temperature of the cooling unit; T 进 is the inlet water temperature of the cooling unit.

[0107] The control device 2 monitors and adjusts the temperature at the front end of each induction heater and the water flow of the corresponding cooling unit, and compares the sum of the water volume of each cooling unit with the total water output of the cooling water system, and determines the water leakage situation of the water path; the control device 2 adjusts the water supply of the cooling unit based on the outlet water temperature of each cooling unit - when the outlet water temperature is too high, the water pump speed is increased, the water pressure is increased, and thus the water flow is increased; when the outlet water temperature is too low, the water pump speed is reduced, the water supply pressure is reduced, and thus the water flow is reduced. In this way, it is ensured that each power module and induction heater that needs to be cooled operates within the normal temperature range.

[0108] like Figures 5-7As shown, each induction heater includes an annular housing 611, an induction coil 616 wound within the housing 611, first and second copper bars 612 connected to the ends of the induction coil 616, and an insulating plate 613 positioned between the first and second copper bars. The induction coil has a spiral structure, with its inlet and outlet terminals connected via the first and second copper bars for connection to an external power source. The insulating plate 613 ensures insulation between the first and second copper bars. The induction coil 616 is secured to the annular housing 611 by a casting material 615, which also insulates the induction coil 616 from the annular housing 611. The annular housing 611 is also provided with a water inlet and outlet box 614, to which water pipes and connectors are welded for connection to corresponding cooling units to ensure water supply and cooling for the induction coil 616. Figure 6a In the figure, H is the width of the induction heater.

[0109] Based on the same inventive concept, Figure 8 As shown, an embodiment of the present invention further provides a control method for the induction heating system as described above, comprising the following steps:

[0110] Step 1: Calculate the shell thickness of the ingot at the first induction heating unit and the second induction heating unit;

[0111] Step 2: controlling the frequencies of the first power supply device and the second power supply device according to the thickness of the ingot shell, thereby controlling the skin depth of the induced current generated by the first induction heating unit and the second induction heating unit.

[0112] In order to reduce or avoid the impact of eddy current heat on the temperature of the molten steel and the entire production line production process during induction heating of the ingot, and to avoid the problem of ingot cracking, the thickness of the ingot shell is the smaller value of the theoretical thickness δ1 and the predicted thickness δ2, where the predicted thickness δ2 is predicted by the continuous casting solidification model stored in the control device. The continuous casting solidification model is designed during the continuous casting line production, and the specific design process is based on the existing technology. Based on the continuous casting solidification model, the shell thickness of the ingot can be predicted for different steel grades, different casting speeds, and different continuous casting line locations. In this embodiment, the calculation formula for the theoretical thickness of the ingot shell is shown in formula (1).

[0113] The smaller of the theoretical thickness δ1 and the predicted thickness δ2 is used as a basis for controlling the operating frequency of the first or second power supply unit to ensure that the skin depth δ0 of the induced current generated by the induction heater is less than the smaller of the theoretical thickness δ1 and the predicted thickness δ2. This reduces or eliminates the effect of eddy current heat on the temperature of the molten steel during induction heating of the ingot. In this embodiment, the skin depth δ0 of the induced current is 1 / 2 to 4 / 5 of the shell thickness of the ingot.

[0114] The installation position of the induction heater is different, and the thickness of the billet shell is different. The operating frequency of the induction heater corresponding to different billet shell thicknesses is different. The thicker the billet shell thickness, the lower the corresponding operating frequency of the induction heater, and the thinner the billet shell thickness, the higher the corresponding operating frequency of the induction heater. In order to avoid the crack problem, the action depth (i.e., skin depth) of the induced current generated by the induction heater is controlled to ensure that the skin depth δ0 is 1 / 2 to 4 / 5 of the billet shell thickness. The relationship between the skin depth of the induced current generated by the induction heater and the frequency of the corresponding power module in the first power supply device or the second power supply device is shown in equation (2) or (3).

[0115] In a specific embodiment of the present invention, the control method further includes:

[0116] Acquire steel grade information of the ingot and temperatures detected by the first temperature detection unit and the second temperature detection unit;

[0117] Controlling the first induction heating unit to start according to the steel grade information of the ingot, and controlling the operating power of the first induction heating unit through the first power supply device according to the temperature detected by the first temperature detection unit and the first target temperature;

[0118] The operating power of the second induction heating unit is controlled by the second power supply device according to the temperature detected by the second temperature detection unit and the second target temperature.

[0119] When the ingot is a crack-sensitive steel or the ingot temperature is too low to reach the target temperature for deformation without cracking, the first induction heating unit is required for heating. In other cases, the first induction heating unit does not heat. Regardless of the steel type, the second induction heating unit must heat, but the heating power required varies depending on the ingot temperature. In this embodiment, the operating power of the first or second induction heating unit is calculated as shown in formula (4).

[0120] The number of temperature sensors in the first temperature detection unit is the same as the number of induction heaters in the first induction heating unit, and the number of temperature sensors in the second temperature detection unit is the same as the number of induction heaters in the second induction heating unit. In this embodiment, if the number of induction heaters in the first induction heating unit is 1, then the number of temperature sensors in the first temperature detection unit is 1; if the number of induction heaters in the second induction heating unit is N, then the number of temperature sensors in the second temperature detection unit is N. Each temperature sensor is located at the front end of its corresponding induction heater.

[0121] The full power or rated power of the induction heater in the first induction heating unit should be greater than or equal to the power required to heat the cast billet from the temperature detected by the first temperature detection unit to the first target temperature. The sum of the full power or rated power of the N induction heaters in the second induction heating unit should be greater than or equal to the power required to heat the cast billet from the temperature detected by the first temperature sensor in the second temperature detection unit to the second target temperature. The control device controls the operating power of the corresponding induction heater in the second induction heating unit based on the second target temperature and the temperature detected by each temperature sensor in the second temperature detection unit.

[0122] In this embodiment, the specific process of sequentially controlling the operating power of the N induction heaters in the second induction heating unit is as follows:

[0123] When the second target temperature T 2m The temperature T detected by the first temperature sensor 21 When the difference is greater than the temperature that can be raised by the first induction heater running at full power, it means that even if the first induction heater runs at full power, the temperature of the billet cannot be raised from T 21 Heating to the second target temperature T 2m , so the first induction heater is controlled to run at full power.

[0124] When the second target temperature T 2m The temperature T detected by the first temperature sensor 21 When the difference is less than or equal to the temperature that can be raised by the first induction heater running at full power, it means that even if the first induction heater runs at full power or lower than full power, the temperature of the billet can be raised from T 21 Heating to the second target temperature T 2m , so the first induction heater is controlled to heat the billet from temperature T 21 Heating to the second target temperature T 2m The required power is used to operate, and the first induction heater can achieve the temperature of the billet from T 21 Heating to the second target temperature T 2m , the second to Nth induction heaters do not work. In this case, the first induction heater operates at full power or less than full power (adaptive power).

[0125] When the second target temperature T 2m The temperature detected by the second temperature sensor T 22 When the difference is greater than the temperature that can be raised by the second induction heater running at full power, it means that even if the second induction heater runs at full power, the temperature of the billet cannot be raised from T 22 Heating to the second target temperature T 2m, so the second induction heater is controlled to run at full power. In this case, both the first and second induction heaters run at full power.

[0126] When the second target temperature T 2m The temperature detected by the second temperature sensor T 22 When the temperature is less than or equal to the temperature that can be raised by the second induction heater running at full power, it means that the second induction heater running at full power or less than full power can raise the temperature of the billet from T 22 Heating to the second target temperature T 2m , so the second induction heater is controlled to heat the billet from temperature T 22 Heating to the second target temperature T 2m The first and second induction heaters can achieve the temperature of the billet from T 21 Heating to the second target temperature T 2m , the 3rd to Nth induction heaters do not work. In this case, the 1st induction heater operates at full power, and the 2nd induction heater operates at full power or less than full power (adaptive power).

[0127] Similarly, when the second target temperature T 2m The temperature T detected by the i-th temperature sensor 2i When the difference is greater than the temperature that can be raised by the full power operation of the i-th induction heater, the i-th induction heater operates at full power until the second target temperature T 2m The temperature T detected by the i-th temperature sensor 2i Less than or equal to the temperature that can be raised by the full power operation of the i-th induction heater (i.e., the first i induction heaters can meet the requirement of heating the billet to the second target temperature). In this case, the first to i-th induction heaters are all operated at full power.

[0128] When the second target temperature T 2m The temperature T detected by the i-th temperature sensor 2i When the temperature is less than or equal to the temperature that can be raised by the full power operation of the i-th induction heater, the i-th induction heater will raise the billet from the temperature T 2i Heating to the second target temperature T 2m In this case, the 1st to the i-th induction heaters are operated at the required power. At this time, the 1st to the i-th induction heaters can heat the slab to the second target temperature, and the i+1th to the Nth induction heaters are not operated. In this case, the 1st to the i-1th induction heaters are all operated at full power, and the i-th induction heater is operated at full power or less than full power (adaptive power).

[0129] When the incoming temperature of the billet is high, the first n induction heaters (n<N) can heat the billet to the second target temperature. However, since the billet will inevitably experience a temperature drop when it is transported to the designated location (without heating), the billet temperature will be lower than the second target temperature. Therefore, temperature compensation is required for the billet. In this embodiment, when the n induction heaters make the billet temperature reach the second target temperature T 2m , and when n<N, (n+1) to (N-1) induction heaters are controlled not to work, and the Nth induction heater is controlled to perform temperature compensation on the ingot.

[0130] In this embodiment, the specific value of temperature compensation can be obtained from the temperature compensation database. The specific construction method of the temperature compensation database is as follows: when the ambient temperature is T h When the temperature drop of the billet from the nth induction heater to the specified position is measured, it is ΔT nN Based on this actual measurement, the temperature drop from different induction heaters to the designated location under different ambient temperatures is obtained and stored in the control device. Based on different situations, the control device controls the corresponding power module in the second power supply device to cause the Nth induction heater to output an appropriate power to compensate for the temperature drop of the billet when it is not heated, ensuring that the billet reaches the second target temperature again when it is transported to the designated location, that is, the target temperature before the billet is straightened.

[0131] In a specific embodiment of the present invention, the control method further includes:

[0132] Obtain the inlet and outlet water temperatures of each cooling unit, the power of each induction heater or each power module;

[0133] The inlet and outlet water flow rates of the cooling unit are controlled according to the inlet and outlet water temperatures of the cooling unit and the power of the corresponding induction heater or power module. The specific control formula is shown in formula (5).

[0134] The above disclosure is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or modifications within the technical scope disclosed in the present invention, and they should all be covered by the scope of protection of the present invention.

Claims

1. An induction heating system, applied to a continuous casting machine, wherein the machine curve of the continuous casting machine sequentially includes a vertical section, a curved section, an arc section and a straightening section, characterized in that: The induction heating system comprises: a first induction heating unit provided at the end of the vertical section or the front end of the curved section, the first induction heating unit being used to heat the billet before it enters the curved section from the vertical section; A second induction heating unit is provided at the end of the arc segment or the front end of the straightening segment, and the second induction heating unit is used to heat the billet before it enters the straightening segment from the arc segment; a first power supply device for supplying power to the first induction heating unit, wherein the power modules in the first power supply device correspond one-to-one to the induction heaters in the first induction heating unit; a second power supply device for supplying power to the second induction heating unit, wherein the power modules in the second power supply device correspond one-to-one to the induction heaters in the second induction heating unit; a control device connected to the first power supply device and the second power supply device, respectively, the control device being used to calculate the shell thickness of the ingot at the first induction heating unit and the second induction heating unit, and to control the frequency of the first power supply device and the second power supply device according to the shell thickness of the ingot, thereby controlling the skin depth of the induced current generated by the first induction heating unit and the second induction heating unit; The shell thickness of the ingot is the smaller value between the theoretical thickness and the predicted thickness. The predicted thickness is predicted by the continuous casting solidification model. The calculation formula of the theoretical thickness is: Wherein, δ1 is the theoretical thickness, K is the solidification coefficient, t is the solidification time, l is the distance from the meniscus to the first induction heating unit or the second induction heating unit, and v is the casting speed; The relationship between the skin depth of the induced current and the frequency of the first power supply device or the second power supply device is: Among them, δ0 is the skin depth of the induced current, μ0 is the relative magnetic permeability of air, and μ r is the relative magnetic permeability of the ingot, σ is the electrical conductivity of the ingot, ω is the angular frequency of the first power supply device or the second power supply device, and f is the operating frequency of the first power supply device or the second power supply device.

2. The induction heating system according to claim 1, characterized in that: The second induction heating unit includes N induction heaters, and the widths of the N induction heaters are from small to large, wherein the first induction heater is close to the arc segment and has the smallest width, and the Nth induction heater is close to the straightening segment and has the largest width.

3. The induction heating system according to claim 2, wherein: The width of the induction heater in the first induction heating unit is smaller than the width of the first induction heater in the second induction heating unit.

4. The induction heating system according to any one of claims 1 to 3, characterized in that: The induction heating system further comprises: a first temperature detection unit provided at the front end of the first induction heating unit and used to detect the temperature of the billet before it enters the bending section; a second temperature detection unit provided at the front end of the second induction heating unit and used to detect the temperature of the billet before it enters the straightening section; The control device is connected to the first temperature detection unit and the second temperature detection unit, and is further used to control the first induction heating unit to be turned on according to the steel grade information of the cast billet, and to control the operating power of the first induction heating unit through the first power supply device according to the temperature detected by the first temperature detection unit and the first target temperature, and to control the operating power of the second induction heating unit through the second power supply device according to the temperature detected by the second temperature detection unit and the second target temperature; The front end of the first induction heating unit refers to an end close to the vertical segment, and the front end of the second induction heating unit refers to an end close to the arc segment.

5. The induction heating system according to claim 4, characterized in that: The second temperature detection unit includes N temperature sensors, the N temperature sensors correspond one-to-one to the N induction heaters in the second induction heating unit, and each temperature sensor is arranged at the front end of the corresponding induction heater; The control device is further configured to control the operating power of the corresponding induction heater in the second induction heating unit according to the second target temperature and the temperature detected by each temperature sensor.

6. The induction heating system according to any one of claims 1 to 3, characterized in that: The induction heating system also includes a cooling water device, which includes multiple cooling units. The number of cooling units is equal to the sum of the number of induction heaters in the first induction heating unit and the second induction heating unit, and the number of power modules in the first power supply device and the second power supply device. The cooling units are used to cool the corresponding induction heaters or power modules.

7. A control method for an induction heating system according to any one of claims 1 to 6, characterized in that: The following steps are involved: Calculating the shell thickness of the casting slab at the first induction heating unit and the second induction heating unit; The frequencies of the first power supply device and the second power supply device are controlled according to the thickness of the cast billet shell, thereby controlling the skin depth of the induced current generated by the first induction heating unit and the second induction heating unit.

8. The control method according to claim 7, characterized in that: The skin depth of the induced current is less than the shell thickness of the casting billet.

9. The control method according to claim 7 or 8, characterized in that: The control method further includes: Acquire steel grade information of the ingot and temperatures detected by the first temperature detection unit and the second temperature detection unit; Controlling the first induction heating unit to start according to the steel grade information of the ingot, and controlling the operating power of the first induction heating unit through the first power supply device according to the temperature detected by the first temperature detection unit and the first target temperature; The operating power of the second induction heating unit is controlled by the second power supply device according to the temperature detected by the second temperature detection unit and the second target temperature.

10. The control method according to claim 9, characterized in that: The calculation formula for the operating power of the first induction heating unit or the second induction heating unit is: Wherein, P is the operating power or heating power of the first induction heating unit or the second induction heating unit; C is the specific heat capacity of the ingot; m is the mass of the ingot transmitted per unit time, and the mass of the ingot refers only to the mass of the ingot within the skin depth of the induced current generated by the first induction heating unit or the second induction heating unit; ΔT is the difference between the target temperature and the initial temperature, the target temperature is the first target temperature or the second target temperature, and the initial temperature is the temperature detected by the first temperature detection unit or the second temperature detection unit; η is the heating efficiency; ε is the skin depth coefficient.

11. The control method according to claim 9, characterized in that: The specific process of sequentially controlling the operating power of the N induction heaters in the second induction heating unit is as follows: When the second target temperature T 2m The temperature T detected by the first temperature sensor 21 When the difference is greater than the temperature that can be raised by the first induction heater running at full power, the first induction heater runs at full power; when the second target temperature T 2m The temperature T detected by the first temperature sensor 21 When the difference is less than or equal to the temperature that can be raised by the first induction heater at full power, the first induction heater will raise the billet from the temperature T 21 Heating to the second target temperature T 2m Power required to operate; When the second target temperature T 2m The temperature detected by the second temperature sensor T 22 When the difference is greater than the temperature that can be raised by the second induction heater running at full power, the second induction heater runs at full power; when the second target temperature T 2m The temperature detected by the second temperature sensor T 22 When the temperature is less than or equal to the temperature that can be raised by the second induction heater at full power, the second induction heater will raise the billet from the temperature T 22 Heating to the second target temperature T 2m Power required to operate; Similarly, when the second target temperature T 2m The temperature T detected by the i-th temperature sensor 2i When the difference is greater than the temperature that can be raised by the full power operation of the i-th induction heater, the i-th induction heater operates at full power until the second target temperature T 2m The temperature T detected by the i-th temperature sensor 2i Less than or equal to the temperature that can be raised by the i-th induction heater running at full power; when the second target temperature T 2m The temperature T detected by the i-th temperature sensor 2i When the temperature is less than or equal to the temperature that can be raised by the full power operation of the i-th induction heater, the i-th induction heater will raise the billet from the temperature T 2i Heating to the second target temperature T 2m Power required to operate; Among them, the first induction heater refers to the induction heater close to the arc segment.

12. The control method according to claim 11, characterized in that: When the n induction heaters make the temperature of the billet reach the second target temperature T 2m , and when n<N, (n+1) to (N-1) induction heaters are controlled not to work, and the Nth induction heater is controlled to perform temperature compensation on the ingot.

13. The control method according to claim 7 or 8, characterized in that: The control method further includes: Obtain the inlet and outlet water temperatures of each cooling unit, the power of each induction heater or each power module; The inlet and outlet water flow of the cooling unit is controlled according to the inlet and outlet water temperatures of the cooling unit and the power of the corresponding induction heater or power module. The specific control formula is: P w (1st) w )·ζ=C 水 m 水 (T 出 -T 进 ) Among them, P w is the power of the induction heater or power module; η w is the heating efficiency or power supply efficiency; ζ is the safety factor; C 水 is the specific heat capacity of water, m 水 T is the water flow per unit time; 出 is the outlet water temperature of the cooling unit; T 进 is the inlet water temperature of the cooling unit.

14. A continuous casting machine, characterized in that: The continuous casting machine comprises the induction heating system according to any one of claims 1 to 6.

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