A large-tonnage dual-frequency coreless induction melting electric furnace

Abstract

This invention relates to a large-tonnage dual-frequency coreless induction melting furnace, belonging to the field of induction furnace technology. It includes a medium-frequency circuit, a low-frequency circuit, and a molten pool. The medium-frequency and low-frequency circuits are respectively connected to the molten pool and used to generate alternating current around the inner cavity of the molten pool. It also includes a control module, which is electrically connected to both the medium-frequency and low-frequency circuits and controls their start and stop. When the control module is in the first stage, it commands the medium-frequency circuit to start and the low-frequency circuit to stop. When the control module is in the second stage, it commands the medium-frequency circuit to stop and the low-frequency circuit to start. It also includes a detection module for detecting the temperature of the metal to be processed in the molten pool and uploading it to the control module. The control module determines whether the metal temperature has reached a threshold and switches from the first stage to the second stage if the determination result is yes. It features a good balance between melting temperature and stirring intensity adjustment, resulting in excellent melting performance.

Description

Technical Field

[0001] This invention belongs to the field of induction furnace technology, specifically relating to a large-tonnage dual-frequency coreless induction melting electric furnace. Background Technology

[0002] Melting is an essential process for using metals, which involves heating the metal to a molten state and then shaping it into the desired form. Traditional furnaces driven by combustion energy consume a lot of resources and cause serious pollution. Traditional furnaces that utilize the electrothermal effect are limited to resistance heating elements, and excessive current can easily damage the circuit. Therefore, induction furnaces, which use relatively low current and less pollution, generate eddy currents in the metal to be processed by an alternating electric field to generate heat, are widely used.

[0003] A typical induction furnace design, such as the high-uniformity heating induction furnace disclosed in Chinese patent application CN218002172U, includes a feeding device, a feed pipe, an induction holding furnace, a discharge pipe, and a receiving device connected in sequence. The induction holding furnace includes a furnace wall and a furnace tube located within the furnace wall. Two or more inductors are arranged along the length of the furnace tube within the furnace wall, each with its own power supply. All inductors are located outside the furnace tube. By using multiple parallel inductors, each connected to a separate power supply for control, the problem of inconsistent heating effects at the front and back of the coil due to excessively long induction coils, which affects product quality, is effectively avoided. This ensures uniform temperature across all sections of the furnace tube, thereby guaranteeing product quality. Furthermore, by setting the power supply frequency of each inductor, the heating efficiency of each section can be adjusted to adapt to product processing with special process requirements, enhancing the adaptability of the induction furnace.

[0004] However, the above-mentioned solutions can only adjust the heating temperature of each section by adjusting the power frequency of each section. They only have the function of differentiating the heating temperature in different sections of the furnace tube along the furnace tube axis, or making the temperature in different sections of the furnace tube consistent. However, during the smelting process, the molten steel needs to be stirred to accelerate heat transfer and improve the uniformity of the molten steel. Furthermore, for vacuum refining, special alloys, post-additives, or refractory materials, a strong stirring force is required. However, the above-mentioned structure can only adjust the heating efficiency and smelting temperature, but does not have the function of adjusting both the smelting temperature and the stirring force. Therefore, a large-tonnage dual-frequency coreless induction furnace that can adjust both the smelting temperature and the stirring force and has a good smelting effect is needed. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a large-tonnage dual-frequency coreless induction melting furnace, which features both adjustable melting temperature and stirring intensity, resulting in excellent melting performance.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A large-tonnage dual-frequency coreless induction melting furnace includes a medium-frequency circuit, a low-frequency circuit, and a molten pool. The medium-frequency circuit and the low-frequency circuit are respectively connected to the molten pool and are used to pass an alternating current around the inner cavity of the molten pool. The current frequency of the medium-frequency circuit is higher than the current frequency of the low-frequency circuit.

[0008] It also includes a control module, which is electrically connected to the intermediate frequency circuit and the low frequency circuit respectively and controls the start and stop of the intermediate frequency circuit and the low frequency circuit. When the control module is in the first stage, it instructs the intermediate frequency circuit to start and instructs the low frequency circuit to shut down. When the control module is in the second stage, it instructs the intermediate frequency circuit to shut down and instructs the low frequency circuit to start.

[0009] The control module is electrically connected to a detection module. The detection module is used to detect the temperature of the metal to be processed in the molten pool and upload it to the control module. The control module is used to determine whether the metal temperature has reached a threshold, and when the determination result is yes, it switches from the first stage to the second stage.

[0010] As a preferred embodiment of the present invention, the control module is used to determine whether the metal temperature has reached a threshold, and when the determination result is yes, it switches from the first stage to the second stage after a delay. The control module determines whether the threshold exceeds a standard value. When the threshold exceeds the standard value, the control module increases the delay. When the threshold is lower than the standard value, the control module decreases the delay.

[0011] As a preferred technical solution of the present invention, the control module is pre-inputting standard values ​​Y0, t0, c and threshold Y. The control module calculates the delay t, and switches from the first stage to the second stage after a delay t when it is determined that the metal temperature has reached the threshold, where t = Y / Y0 × t0 × c.

[0012] As a preferred embodiment of the present invention, the detection module includes a temperature sensor array, which includes several temperature sensors. The several temperature sensors are used to detect the temperature of the metal to be processed in different parts of the molten pool and upload several temperature data to the control module. After receiving several temperature data, the control module removes outliers and selects the minimum value among the several temperature data after removing outliers as the metal temperature.

[0013] As a preferred technical solution of the present invention, the control module calculates the variance after receiving a number of temperature data and determines whether the variance exceeds the variance threshold. When the determination result is yes, the data with the largest deviation is found and removed as an outlier. The variance of the remaining temperature data after removing the outlier is recalculated until the determination result is no.

[0014] As a preferred embodiment of the present invention, the control module is pre-inputting a standard value of variance threshold F0. After receiving several temperature data w, the control module calculates the mean value wj and the variance threshold F, where F = wj / w0 × F0 × d, and D is a pre-input constant.

[0015] As a preferred embodiment of the present invention, it further includes a control panel electrically connected to the control module, the control panel being used to input the values ​​of Y0, t0, c, F0, d and Y.

[0016] As a preferred embodiment of the present invention, the intermediate frequency circuit includes an intermediate frequency capacitor, the low frequency circuit includes a low frequency capacitor, the control module adjusts the connection and disconnection of the low frequency capacitor and the low frequency circuit by switching on and off the vacuum contactor, and the control module adjusts the connection and disconnection of the intermediate frequency capacitor and the intermediate frequency circuit by switching on and off the vacuum contactor.

[0017] The beneficial effects of this invention are as follows:

[0018] (1) By setting a detection module to detect the temperature of the metal to be processed in the molten pool, and switching from medium frequency operation to low frequency operation when the temperature reaches the threshold, the control of the molten steel temperature and the retention of trace elements during the medium frequency operation in the heating and melting stage, as well as the stirring force in the subsequent stirring stage;

[0019] (2) The temperature of the metal to be processed in the molten pool is detected by the detection module, and the operation is switched from medium frequency to low frequency when the temperature reaches the threshold. The automatic switching of the stage is completed to avoid the situation where the metal is switched from the medium frequency mode with strong heating capacity to the low frequency mode with strong stirring capacity before it is completely melted into molten steel, resulting in incomplete melting. When the metal is switched too late, the metal is not switched and stirred even after it is completely melted into molten steel, resulting in poor efficiency.

[0020] (3) By using the control module to determine whether the metal temperature has reached the threshold, and switching from the first stage to the second stage after a delay when the determination result is yes, and increasing the delay when the threshold exceeds the standard value, and decreasing the delay when the threshold is below the standard value, the delay is increased when the threshold is large, the melting point of the metal to be melted is high, and the probability that the metal inside the furnace has not fully reached the threshold is high, and a longer delay is required to switch from the first stage to the second stage; when the threshold is small, the melting point of the metal to be melted is low, and the probability that the metal inside the furnace has not fully reached the threshold is low, and a longer delay is not required to switch from the first stage to the second stage, the delay is decreased, so as to ensure the melting effect while taking into account the work efficiency.

[0021] (4) By setting up several temperature sensors to detect the temperature of the metal to be processed in different parts of the molten pool and uploading several temperature data to the control module, and after receiving several temperature data, the control module removes abnormal values ​​and selects the minimum value among several temperature data after removing abnormal values ​​as the metal temperature, thus avoiding the situation where the temperature detection is inaccurate due to setting up a single temperature sensor, and the control module switches stages according to whether the temperature has reached the threshold, resulting in inaccurate switching timing.

[0022] (5) At the same time, after receiving a number of temperature data, the control module removes outliers and selects the minimum value among the temperature data after removing outliers as the metal temperature. This avoids the situation where one or more temperature sensors deviate significantly from the other values ​​under the influence of random factors, resulting in inaccurate temperature detection. Consequently, when the control module switches stages based on whether the temperature has reached the threshold, the switching timing may be inaccurate.

[0023] (6) By having the control module calculate the median wj after receiving several temperature data w, and calculate the variance threshold F=wj / w0×F0×d, the variance threshold is increased when the overall temperature is high and the heat exchange in each part is relatively intense, and the standard for whether the variance is too large needs to be relaxed, so as to prevent the rejection of normal data; when the overall temperature is low and the heat exchange in each part is not relatively intense, and there is no need to relax the standard for whether the variance is too large, the variance threshold is reduced and the standard for whether the variance is too large is tightened to improve the accuracy of temperature detection. Attached Figure Description

[0024] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of the structure of the present invention;

[0026] Figure 2 This is a schematic diagram illustrating the steps of the control module of the present invention when switching between the first stage and the second stage;

[0027] Description of main component symbols:

[0028] In the diagram: 1. Molten pool; 2. Coil. Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0030] Please see Figure 1-2A large-tonnage dual-frequency coreless induction melting electric furnace includes a medium-frequency circuit, a low-frequency circuit, and a molten pool 1. The medium-frequency circuit and the low-frequency circuit are respectively connected to the molten pool 1 and are used to pass an alternating current around the inner cavity of the molten pool 1. The current frequency of the medium-frequency circuit is higher than the current frequency of the low-frequency circuit.

[0031] Specifically, the induction melting furnace includes at least one outer shell, with a molten pool 1 disposed within the outer shell. In this embodiment, the furnace body is a hollow cylindrical shape placed perpendicular to the ground. The furnace body is used to contain the metal to be melted. A coil 2 is arranged around the furnace body with its axis perpendicular to the ground. The bottom of the coil 2 is flush with the bottom of the furnace body, and the top of the coil 2 is lower than the top of the furnace body. The intermediate frequency circuit and the low frequency circuit can be separately connected to the coil 2. The control module controls the disconnection or connection of the intermediate frequency circuit and the low frequency circuit with the coil 2. When the control module commands the intermediate frequency circuit to connect with the coil 2, it simultaneously commands the low frequency circuit to disconnect from the coil 2. At this time, the intermediate frequency circuit and the coil 2 form a loop, and the coil 2 and the induction furnace operate at the intermediate frequency. Similarly, when the control module commands the low frequency circuit to connect with the coil 2, the low frequency circuit and the coil 2 form a loop, and the coil 2 and the induction furnace operate at the low frequency.

[0032] During the smelting process, reducing the frequency will increase the electromagnetic stirring force. When the power supply frequency decreases, the time of the alternating electromagnetic field in the induction coil 2 becomes longer, resulting in an increase in the size of the eddy current, which in turn increases the electromagnetic stirring force. Higher frequencies are used to increase surface heating and melting speed, while lower frequencies are used to increase penetration depth and overall stirring effect. In addition, during the smelting process, it is necessary to stir the molten steel to accelerate heat transfer and improve the uniformity of the molten steel. Furthermore, strong stirring force is required for vacuum refining, special alloys, post-additives, or refractory materials. However, if the heating and smelting effect is ensured by increasing the power density during the heating and smelting stage, the temperature of the molten steel will rise rapidly, leading to the destruction of trace elements and making it difficult to control the temperature of the molten steel.

[0033] Therefore, medium-frequency melting is required first. Medium-frequency operation has a higher melting temperature, which is used to heat and melt the metal to be melted. It can also ensure the control of the molten steel temperature and the retention of trace elements. After the steel block is completely melted into molten steel, it needs to be stirred. At this time, it is switched to a low-frequency mode with stronger stirring force.

[0034] To facilitate switching control, a control module is also included. The control module is electrically connected to the intermediate frequency circuit and the low frequency circuit respectively and controls the start and stop of the intermediate frequency circuit and the low frequency circuit. When the control module is in the first stage, it instructs the intermediate frequency circuit to start and instructs the low frequency circuit to shut down. When the control module is in the second stage, it instructs the intermediate frequency circuit to shut down and instructs the low frequency circuit to start.

[0035] During smelting, medium-frequency smelting is used first. The smelting temperature of medium-frequency operation is higher and it is used to smelt the metal to be smelted. After the steel block is completely melted into molten steel, it needs to be stirred. At this time, the control module command switches to a low-frequency mode with stronger stirring force.

[0036] Given a fixed circuit structure, operating power, and furnace induction coil 2, the frequency of the equipment can be changed by altering the capacitance value. Therefore, the intermediate frequency circuit includes an intermediate frequency capacitor, and the low frequency circuit includes a low frequency capacitor. The control module adjusts the connection and disconnection of the low frequency capacitor and the low frequency circuit by switching the vacuum contactor on and off. The control module also adjusts the connection and disconnection of the intermediate frequency capacitor and the intermediate frequency circuit by switching the vacuum contactor on and off.

[0037] Specifically, the vacuum contactor is configured such that when it is disconnected, the intermediate frequency capacitor is connected to coil 2 and the low frequency capacitor is disconnected from coil 2; when it is connected, the low frequency capacitor is connected to coil 2 and the intermediate frequency capacitor is disconnected from coil 2.

[0038] When actually switching between intermediate frequency circuits and low frequency circuits, the control module additionally checks whether the switching conditions are met to prevent circuit failures caused by forced switching.

[0039] When operating at medium frequency, the control module first issues a command to automatically reduce the power supply and stop the inverter. Then, it checks whether the switching conditions are met. If the condition is "no", the vacuum contactor will not disconnect, and the control panel will display a switching frequency abnormality message. The vacuum contactor can only be disconnected after the abnormality is resolved and the switching conditions are met. If the condition is "yes", the vacuum contactor will disconnect, the low-frequency operating capacitor will be disconnected, and the induction furnace will enter the medium-frequency melting operation. If the vacuum contactor disconnection is abnormal, the control panel will display a switching frequency abnormality message.

[0040] When operating at low frequency, the control module first issues a command to automatically reduce the operating power of the power supply and then stop the inverter. Then, it checks whether the switching conditions are met: if the condition is "no", the vacuum contactor is not connected, and the control panel will display a switching frequency abnormality message. The vacuum contactor can only be connected after the abnormality is resolved and the switching conditions are met; if the condition is "yes", the vacuum contactor is connected, the low-frequency operating capacitor is engaged, and the induction furnace enters low-frequency melting operation. If the vacuum contactor engagement is abnormal, the control panel will display a switching frequency abnormality message.

[0041] In the above-mentioned smelting process, if the switch is made too early, the medium-frequency mode with strong heating capacity will be switched to the low-frequency mode with strong stirring capacity before the steel is completely melted, resulting in incomplete smelting. If the switch is made too late, the steel will be completely melted but the stirring will not be switched, resulting in poor efficiency.

[0042] Therefore, the switching timing needs to be precisely adjusted. For this purpose, the control module is electrically connected to the detection module. The detection module is used to detect the temperature of the metal to be processed in the molten pool 1 and upload it to the control module. The control module is used to determine whether the metal temperature has reached the threshold and switch from the first stage to the second stage when the determination result is yes.

[0043] Specifically, the threshold is determined by the operator based on the melting point of the metal to be melted in a certain batch of production. In actual use, the operator can set the threshold slightly higher than the melting point of the metal to be melted to prevent the temperature detected by the detection module from being lower than the actual temperature, which would lead to the judgment that the melting point has been reached when it has not been reached, and thus the mode switching would occur before the complete melting is completed.

[0044] When the melting process is underway, the temperature of the metal to be melted reaches the temperature threshold, which means that the temperature of the metal to be melted has reached the melting point. At this time, the process switches from the medium frequency mode with strong heating capacity to the low frequency mode with strong stirring capacity.

[0045] By setting a detection module to monitor the temperature of the metal to be processed in the molten pool 1, and switching from medium-frequency operation to low-frequency operation when the temperature reaches the threshold, the system ensures the control of the molten steel temperature and the retention of trace elements during the heating and melting stage. In addition, it automatically switches between stages while maintaining the stirring force during the subsequent stirring stage. This avoids situations where switching too early would result in incomplete melting, as the metal is not fully melted into molten steel before switching from the medium-frequency mode with strong heating capacity to the low-frequency mode with strong stirring capacity. Conversely, switching too late would result in inefficient operation, as the metal is fully melted into molten steel but no stirring is performed.

[0046] In the above process, for metals with higher melting points, the heating time or power required is greater, and there is a greater probability that when the temperature detected by the detection module reaches the threshold, the internal temperature has not been fully heated to the threshold. That is, when the control module judges that the metal temperature has reached the threshold based on the monitored temperature, the internal temperature has not fully reached the threshold. At this time, it is necessary to delay for a period of time after the detection module detects that the temperature has reached the threshold, so that the equipment runs in medium frequency mode for a longer period of time to ensure that all the metal in the furnace is melted before switching to low frequency mode. For metals with higher melting points, the delay required is greater. Therefore, the control module is used to judge whether the metal temperature has reached the threshold, and when the judgment result is yes, it switches from the first stage to the second stage after a delay. The control module judges whether the threshold exceeds the standard value. When the threshold exceeds the standard value, the control module increases the delay; when the threshold is below the standard value, the control module decreases the delay.

[0047] Specifically, the control module is pre-input with standard values ​​Y0, t0, c and threshold Y. The control module calculates the delay t, and switches from the first stage to the second stage after a delay t when it determines that the metal temperature has reached the threshold. Here, t = Y / Y0 × t0 × c.

[0048] Before a batch of production begins, the operator inputs a threshold Y. When the threshold Y is large, it means that the melting point of the metal to be melted is high. At this time, the probability that the metal inside the furnace has not completely reached the threshold is high. It is necessary to switch from the first stage to the second stage after a delay, and the required delay is long to ensure the melting effect. At this time, the value of t=Y / Y0×t0×c is large. When the control module determines that the metal temperature has reached the threshold, it switches from the first stage to the second stage after a delay t. This completes the process of increasing the delay of switching from the first stage to the second stage when the temperature of the metal to be melted is high.

[0049] When the threshold Y is small, it means that the melting point of the metal to be melted is low. At this time, the probability that the metal inside the furnace has not completely reached the threshold is low. There is no need to switch from the first stage to the second stage after a long delay, so as to ensure the efficiency of operation. At this time, the value of t=Y / Y0×t0×c is large. When the control module determines that the metal temperature has reached the threshold, it switches from the first stage to the second stage after a delay t. This completes the reduction of the delay in switching from the first stage to the second stage when the temperature of the metal to be melted is low.

[0050] The control module determines whether the metal temperature has reached a threshold. If the determination is yes, it switches from the first stage to the second stage after a delay. The delay is increased when the threshold exceeds the standard value and decreased when the threshold is below the standard value. When the threshold is large, the melting point of the metal to be melted is high, and the probability that the metal inside the furnace has not fully reached the threshold is high, requiring a longer delay before switching from the first stage to the second stage. Conversely, when the threshold is small, the melting point of the metal to be melted is low, and the probability that the metal inside the furnace has not fully reached the threshold is low, requiring no longer delay before switching from the first stage to the second stage, the delay is reduced. This approach ensures both melting effect and operational efficiency.

[0051] In practical use, if the detection module is equipped with a single temperature sensor to perform local temperature detection of the metal to be melted in the furnace, when the local temperature changes and deviates from the overall temperature in the furnace, the detected temperature will be inaccurate. This will lead to inaccurate switching timing of the control module when switching stages based on whether the temperature has reached the threshold. To improve the accuracy of temperature detection, the detection module includes a temperature sensor array, which includes several temperature sensors. These sensors are used to detect the temperature of the metal to be processed in different parts of the molten pool 1 and upload the temperature data to the control module.

[0052] By setting up a temperature sensor array to detect the temperature of the metal to be processed, compared with the solution of using a single temperature sensor to detect the local temperature of the metal to be melted, multiple temperature data are more representative of the temperature of the metal to be processed in the furnace, improving the accuracy of temperature detection, and thus improving the accuracy of the control module in switching stages based on whether the temperature has reached the threshold.

[0053] During the temperature detection process by several temperature sensors, after receiving several temperature data, the control module may find that one or more temperature sensors are inaccurate due to random factors. Outliers need to be removed, and the minimum value among the several temperature data after removing outliers is selected as the metal temperature.

[0054] Therefore, the temperature sensor array uploads several temperature data once per second. The control module records each set of temperature data as a group after receiving several temperature data, calculates the variance of this group of temperature data, and determines whether the variance exceeds the variance threshold.

[0055] When the judgment result is yes, it means that one or more temperature sensors have a large deviation from the other values ​​under the influence of random factors. This part of the temperature detection is inaccurate. At this time, the control module calculates the mean of this set of temperature data, finds the data with the largest deviation from the mean, and removes it as an outlier. After removal, the variance of several temperature data after removing the outlier is recalculated, and it is judged again whether the variance exceeds the variance threshold. The above process is repeated until the judgment result is no, and the removal of outliers is completed.

[0056] Subsequently, when the minimum value among several temperature data also reaches the threshold, it means that there is a high probability that the temperature of the metal to be processed in the furnace will reach the melting point. Therefore, the control module selects the minimum value among several temperature data after removing outliers as the metal temperature.

[0057] By setting up several temperature sensors to detect the temperature of the metal to be processed in different parts of the molten pool 1 and uploading several temperature data to the control module, the control module removes outliers after receiving several temperature data and selects the minimum value among several temperature data after removing outliers as the metal temperature. This avoids the situation where setting up a single temperature sensor would result in inaccurate temperature detection, which would lead to inaccurate switching timing when the control module switches stages based on whether the temperature has reached the threshold.

[0058] Meanwhile, the control module removes outliers after receiving a number of temperature data points and selects the minimum value among the remaining temperature data points after removing outliers as the metal temperature. This avoids situations where one or more temperature sensors deviate significantly from the other values ​​due to random factors, which could lead to inaccurate temperature detection.

[0059] During the above process, when the temperature is high, more intense heat exchange will occur in various parts, and the temperature fluctuation will be more drastic. At this time, the temperature of different parts of the metal to be processed is more likely to deviate significantly. It is normal for one data point to deviate significantly from the others in the data from different temperature sensors. When the variance threshold is small, the control module will reject the normal data. Therefore, when the temperature threshold is high, the variance threshold needs to be appropriately increased, and the standard for judging whether the variance is too large needs to be relaxed.

[0060] Therefore, the control module is pre-inputted with a standard value of variance threshold F0. After receiving several temperature data w, the control module obtains the median wj and calculates the variance threshold F, where F = wj / w0 × F0 × d, and D is a pre-input constant.

[0061] When the median is large, it indicates that the overall temperature is high and more intense heat exchange will occur in various parts. It is necessary to appropriately increase the variance threshold and relax the standard for whether the variance is too large. At this time, the value of F=wj / w0×F0×d is large. Therefore, when the temperature is high, the variance threshold should be increased and the standard for judging whether the variance is too large should be relaxed.

[0062] When the median is low, it means that the overall temperature is low and there is no intense heat exchange in various parts. At this time, if a certain data deviates significantly from the other values, it is likely that a measurement error has occurred. There is no need to increase the variance threshold or relax the standard for whether the variance is too large. At this time, the value of F=wj / w0×F0×d is relatively large. Therefore, when the temperature is low, the variance threshold should be reduced and the standard for judging whether the variance is too large should be narrowed.

[0063] By having the control module calculate the median wj after receiving several temperature data points w, and then calculate the variance threshold F = wj / w0 × F0 × d, the system can improve the accuracy of temperature detection. When the overall temperature is high and there is significant heat exchange in various parts, requiring a more relaxed standard for whether the variance is too large, the variance threshold is increased to prevent the rejection of normal data. Conversely, when the overall temperature is low and there is no significant heat exchange in various parts, requiring a more relaxed standard for whether the variance is too large, the variance threshold is decreased to tighten the standard for whether the variance is too large.

[0064] To facilitate the input of values ​​for Y0, t0, c, F0, d, and Y, a control panel electrically connected to the control module is also included. The control panel is used to input the values ​​for Y0, t0, c, F0, d, and Y.

[0065] Working principle and usage process of this invention:

[0066] During the smelting process, the process first enters the first stage, which uses medium-frequency smelting. The smelting temperature of medium-frequency operation is higher, which is used to smelt the metal to be smelted. After the steel block is completely melted into molten steel, it needs to be stirred. At this time, the control module commands switch to the second stage, which uses a low-frequency mode with stronger stirring force.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A large-tonnage dual-frequency coreless induction melting electric furnace, characterized in that: It includes an intermediate frequency circuit, a low frequency circuit, and a molten pool. The intermediate frequency circuit and the low frequency circuit are respectively connected to the molten pool and are used to pass an alternating current around the inner cavity of the molten pool. The current frequency of the intermediate frequency circuit is higher than the current frequency of the low frequency circuit. It also includes a control module, which is electrically connected to the intermediate frequency circuit and the low frequency circuit respectively and controls the start and stop of the intermediate frequency circuit and the low frequency circuit. When the control module is in the first stage, it instructs the intermediate frequency circuit to start and instructs the low frequency circuit to shut down. When the control module is in the second stage, it instructs the intermediate frequency circuit to shut down and instructs the low frequency circuit to start. The control module is electrically connected to the detection module. The detection module is used to detect the temperature of the metal to be processed in the molten pool and upload it to the control module. The control module is used to determine whether the metal temperature has reached the threshold and switch from the first stage to the second stage when the determination result is yes. The control module is used to determine whether the metal temperature has reached the threshold, and when the determination result is yes, it switches from the first stage to the second stage after a delay. The control module determines whether the threshold exceeds the standard value. When the threshold exceeds the standard value, the control module increases the delay. When the threshold is lower than the standard value, the control module decreases the delay. The detection module includes a temperature sensor array, which includes several temperature sensors. These temperature sensors are used to detect the temperature of the metal to be processed in different parts of the molten pool and upload several temperature data to the control module. After receiving several temperature data, the control module removes outliers and selects the minimum value among the several temperature data after removing outliers as the metal temperature. After receiving several temperature data, the control module calculates the variance and determines whether the variance exceeds the variance threshold. If the determination result is yes, it finds the data with the largest deviation and removes it as an outlier. Then, it recalculates the variance of several temperature data after removing the outlier until the determination result is no. The intermediate frequency circuit includes an intermediate frequency capacitor, the low frequency circuit includes a low frequency capacitor, and the control module adjusts the connection and disconnection of the low frequency capacitor and the low frequency circuit by switching the vacuum contactor on and off. The control module also adjusts the connection and disconnection of the intermediate frequency capacitor and the intermediate frequency circuit by switching the vacuum contactor on and off.

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