Non-ferrous metal light wave smelting furnace and intelligent temperature control method thereof

Abstract

The application provides a non-ferrous metal light wave smelting furnace and an intelligent temperature control method thereof, and belongs to the technical field of non-ferrous metal smelting equipment. The non-ferrous metal light wave smelting furnace comprises a light wave emitting device, a graphene heating film, a temperature detection unit, a current detection unit and a controller. The controller is configured to perform three control loop coupling cooperative control. The three control loops comprise: a temperature control loop, which adjusts the heating power of the light wave emitting device and the graphene heating film according to the deviation between the temperature fed back by the temperature detection unit and the target temperature; a power grid balancing loop, which redistributes three-phase current according to the three-phase current fed back by the current detection unit; and a cooperative heating loop, which dynamically adjusts the power distribution ratio between the light wave emitting device and the graphene heating film according to the smelting stage. The application fundamentally breaks through the skin effect limitation of traditional electromagnetic induction heating through the non-contact volume heating principle of infrared light waves, and realizes the overall uniform heating of metal ingot materials.

Description

Technical Field

[0001] This invention belongs to the technical field of non-ferrous metal smelting equipment, specifically a non-ferrous metal light wave smelting furnace and its intelligent temperature control method. Background Technology

[0002] In the non-ferrous metals processing industry, electromagnetic induction melting furnaces have long been widely used as the core equipment for melting metal ingots in the zinc alloy die-casting field. The physical principle of electromagnetic induction heating is based on Faraday's law of electromagnetic induction: when an alternating current passes through an induction coil, an alternating magnetic field is generated inside the metal charge. This magnetic field induces eddy currents inside the conductive metal, and the eddy currents generate Joule heat under the action of the metal material's resistance, thereby achieving metal heating and melting.

[0003] However, electromagnetic induction heating suffers from an inherent physical phenomenon—the skin effect—which is the fundamental physical bottleneck limiting its heating uniformity and thermal efficiency. The skin effect manifests as follows: eddy current density is highest at the metal surface and decreases exponentially along the depth direction, with heat mainly concentrated within a thin layer of a certain thickness on the metal surface. For non-ferromagnetic materials such as zinc alloys, the skin depth is typically only a few millimeters to ten millimeters under power frequency induction heating conditions. This means that heat generation is concentrated on the metal surface, and heat transfer within the metal ingot relies entirely on thermal conduction. Due to the limited thermal conductivity of zinc alloys, heat conduction from the surface to the core takes a long time, and a significant temperature gradient forms radially. This "externally hot, internally cold" heating mode leads to the following technical drawbacks:

[0004] The electromagnetic induction melting furnace has low thermal efficiency and high energy consumption. The Joule heat generated by a large amount of electrical energy is first concentrated in the thin surface area, and then diffuses into the interior through heat conduction. During this process, a large amount of heat is lost to the environment through the furnace wall. In actual operation, the thermal efficiency of the electromagnetic induction melting furnace is only 60%~70%, and the power consumption for melting 1 ton of zinc alloy is as high as 800~1000 kWh.

[0005] Electromagnetic stirring effect leads to severe oxidation and burn-off of metal. The Lorentz force generated by electromagnetic induction drives the molten metal to generate strong electromagnetic stirring in the molten metal pool, causing the high-temperature molten metal surface to come into violent contact with air, accelerating the oxidation reaction of zinc alloy. Active elements in zinc alloy (such as aluminum and magnesium) are preferentially oxidized under high-temperature stirring conditions, forming a large number of oxide inclusions, resulting in a waste slag rate as high as 22%~24%, which seriously reduces the utilization rate of raw materials.

[0006] The temperature control is crude and the product quality is unstable. Because the heating source is concentrated on the surface, the temperature sensor is difficult to accurately reflect the overall temperature of the molten pool. In addition, the temperature fluctuation caused by electromagnetic stirring results in an actual temperature control accuracy of only ±15℃~±20℃, which is far from meeting the requirements of precision die casting process for the stability of molten liquid temperature. Large temperature fluctuations can also lead to alloy composition segregation, affecting the mechanical properties and surface quality of die castings.

[0007] It has a serious impact on the power grid. High-power induction furnaces (usually hundreds of kilowatts to several megawatts) are single-phase or two-phase loads. When connected to the workshop's three-phase power grid, they cause serious three-phase imbalance, with the imbalance often exceeding 15%. At the same time, the induction furnace has a low power factor (usually 0.6~0.7), generating a large amount of harmonic pollution, which affects the normal operation of other precision equipment in the workshop. It is necessary to configure expensive reactive power compensation and harmonic control devices.

[0008] Infrared radiation heating is a technology that utilizes the interaction between electromagnetic waves in the infrared band and matter to achieve heating. Unlike electromagnetic induction heating, infrared radiation heating is a "volume heating" mode. Its energy transfer does not rely on the eddy current effect in a conductive medium, but is based on the interaction between photons and lattice vibrations (phonons) and free electrons in matter, directly converting light energy into heat energy. In the field of materials processing, infrared radiation heating has been widely used in the heat treatment of semiconductor materials, curing and drying of polymer materials, food processing, wood processing, and some metal heat treatment processes.

[0009] However, in the field of non-ferrous metal smelting, the application research of infrared radiation heating technology is relatively lagging behind, and mature industrial equipment has not yet been developed. Although there are experimental reports on infrared-assisted metal heating in existing public literature, they generally suffer from the following problems: insufficient matching between the infrared emission source and the absorption characteristics of specific metals, resulting in low energy utilization; lack of effective constant temperature control methods, leading to large temperature fluctuations; failure to consider the impact of high-power smelting equipment on the power grid; and failure to integrate with automated liquid supply systems, making continuous production impossible.

[0010] In summary, the non-ferrous metal die-casting industry urgently needs a new smelting technology that fundamentally overcomes the physical limitations of electromagnetic induction heating. This technology should simultaneously meet the following requirements: achieving true "volume heating," eliminating the skin effect, and significantly improving thermal efficiency; avoiding electromagnetic stirring, significantly reducing metal oxidation and burn-off; achieving high-precision constant temperature control (within ±3℃) to ensure stable molten metal quality; actively balancing the three-phase load of the power grid to improve power quality; and integrating automated molten metal supply to achieve integrated continuous production of smelting and molten metal supply. This invention is a complete technical solution proposed to address the aforementioned industry needs. Summary of the Invention

[0011] In view of the shortcomings of the prior art, the technical problem to be solved by the embodiments of the present invention is to provide a non-ferrous metal light wave melting furnace and its intelligent temperature control method.

[0012] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0013] A non-ferrous metal light wave melting furnace, comprising:

[0014] Furnace body;

[0015] A light wave emitting device is installed on the top of the furnace body to emit infrared light waves into the furnace chamber;

[0016] A graphene heating film is wrapped around the outer wall of the furnace body;

[0017] Temperature detection unit, used to collect temperature data at multiple locations inside the furnace in real time;

[0018] The current detection unit is used to detect the three-phase current of the power grid in real time.

[0019] The controller is connected to the light wave emitting device, the graphene heating film, the temperature detection unit, and the current detection unit, respectively. The controller is configured to perform three-loop coupled and coordinated control, wherein the three control loops include:

[0020] The temperature control loop adjusts the heating power of the light wave emitting device and the graphene heating film based on the deviation between the temperature fed back by the temperature detection unit and the target temperature.

[0021] The power grid balancing circuit calculates the three-phase imbalance based on the three-phase current fed back by the current detection unit, and redistributes the power when the three-phase imbalance exceeds a preset threshold.

[0022] The collaborative heating circuit dynamically adjusts the power distribution ratio between the light wave emitting device and the graphene heating film according to the melting stage.

[0023] As a further improvement: the inner wall of the furnace is provided with an inner lining, and the surface of the inner lining is coated with an infrared reflective coating.

[0024] As a further improvement: when smelting zinc alloy, the infrared light emitted by the light emitting device has a wavelength range of 2μm-10μm.

[0025] As a further improvement: when smelting zinc alloy, the wavelength range of the infrared light emitted by the light emitting device is preferably 3μm-5μm.

[0026] As a further improvement, the graphene heating film is divided into multiple independently controllable zones.

[0027] As a further improvement: the graphene heating film is divided into a bottom region and multiple sidewall regions distributed along the height of the sidewalls, with each region being independently powered and controlled.

[0028] As a further improvement, the temperature control loop adopts a composite control strategy combining PID control and fuzzy control, and outputs power adjustment signals for the graphene heating film in each zone based on the weighted fusion value of multi-point temperature.

[0029] As a further improvement: the collaborative heating circuit is configured as follows:

[0030] During the heating phase, the light wave emitting device is controlled to heat at the dominant power, while the graphene heating film is heated at the auxiliary power.

[0031] During the constant temperature phase, the light wave emitting device is controlled to reduce to a maintenance power or shut down, and precise temperature control is dominated by the graphene heating film.

[0032] As a further improvement, an automatic liquid supply system is also included, the automatic liquid supply system comprising:

[0033] An automatic feeding mechanism is installed on the upper side of the furnace body;

[0034] The molten pool located at the bottom of the furnace;

[0035] A metering pump connected to the molten pool;

[0036] And a delivery pipe connecting the metering pump to an external die-casting machine, the outer wall of which is wrapped with a graphene heating film for heat preservation.

[0037] This invention also provides an intelligent temperature control method for a non-ferrous metal light wave melting furnace, the method comprising the following steps:

[0038] Real-time acquisition of temperature at multiple locations within the furnace and three-phase current from the power grid;

[0039] Based on the deviation between the collected temperature and the target temperature, the heating power of each section of the light wave emitting device and the graphene heating film is adjusted through a temperature control loop.

[0040] The three-phase imbalance is calculated based on the collected three-phase current. When the three-phase imbalance exceeds a preset threshold, the power of each section of the graphene heating film is redistributed among the three-phase power grid through the power grid balancing circuit.

[0041] Based on the current smelting stage, the power distribution ratio between the light wave emitting device and the graphene heating film is dynamically adjusted through a synergistic heating circuit.

[0042] Compared with existing technologies, the beneficial effects of this invention are as follows: By using the non-contact body heating principle of infrared light waves, it fundamentally breaks through the skin effect limitation of traditional electromagnetic induction heating, achieving uniform heating of the entire metal ingot, significantly improving thermal efficiency and significantly reducing smelting energy consumption; at the same time, since no electromagnetic stirring is generated during the heating process, the oxidation and burning loss of the molten metal is effectively suppressed, improving the purity of the melt and the utilization rate of raw materials; combined with the active constant temperature compensation of the graphene heating film and multi-point temperature detection and composite control algorithm, high-precision and stable control of furnace temperature is achieved, significantly improving the uniformity of melt temperature and the consistency of product quality; in addition, by organically coupling the temperature control system with the three-phase balance control of the power grid, the power distribution of each heating unit in the three-phase power grid can be dynamically optimized, actively improving the power quality of the power grid, without the need for additional reactive power compensation devices. Attached Figure Description

[0043] Figure 1 A schematic diagram of the overall structure of the light wave melting furnace;

[0044] Figure 2 A diagram showing the partitioned arrangement of the graphene heating film;

[0045] Figure 3 This is a flowchart of the three-control-loop coupled and coordinated control logic.

[0046] Figure 4 The graphs show the energy consumption and temperature control performance of the present invention and existing electromagnetic induction melting technology. (a) shows the temperature rise curves, (b) shows the energy consumption comparison bar chart, (c) shows the waste slag rate comparison, and (d) shows the three-phase balance comparison.

[0047] Figure 5 A physical picture of the skin effect in electromagnetic induction;

[0048] Figure 6 Physical image of heating an infrared light source;

[0049] Figure 7 The infrared absorption spectrum of zinc alloy in the 3μm-5μm band is shown.

[0050] Figure 8 This diagram shows the signal connection relationships between the three-phase current transformer, PLC controller, and graphene heating film in each section.

[0051] Figure 9 Here is the flowchart for the balancing algorithm;

[0052] In the diagram: 1. Light wave emitting device; 2. Furnace chamber; 3. Ceramic fiber lining; 4. Graphene heating film; 5. Molten pool; 6. Temperature sensor; 7. Automatic feeding mechanism; 8. Quantitative liquid supply pump; 9. Conveying pipeline; 10. Three-phase current transformer; 11. PLC controller; 12. Infrared reflective coating; 21. First area; 22. Second area; 23. Third area; 24. Fourth area; 25. Fifth area. Detailed Implementation

[0053] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0054] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0055] Please see Figure 1 , Figure 2 In one embodiment, a non-ferrous metal light wave melting furnace includes:

[0056] Furnace body;

[0057] An infrared light emitting device 1 is installed on the top of the furnace body and is used to emit infrared light waves into the furnace chamber 2.

[0058] A graphene heating film 4 is wrapped around the outer wall of the furnace body;

[0059] Temperature detection unit, used to collect the temperature at multiple locations inside furnace 2 in real time;

[0060] The current detection unit is used to detect the three-phase current of the power grid in real time.

[0061] The controller is connected to the light wave emitting device 1, the graphene heating film 4, the temperature detection unit, and the current detection unit, respectively. The controller is configured to perform three-loop coupled and coordinated control, wherein the three control loops include:

[0062] The temperature control loop adjusts the heating power of the light wave emitting device 1 and the graphene heating film 4 based on the deviation between the temperature fed back by the temperature detection unit and the target temperature.

[0063] The power grid balancing circuit calculates the three-phase imbalance based on the three-phase current fed back by the current detection unit, and redistributes the power when the three-phase imbalance exceeds a preset threshold.

[0064] The collaborative heating circuit dynamically adjusts the power distribution ratio between the light wave emitting device 1 and the graphene heating film 4 according to the melting stage.

[0065] In this embodiment, the light wave emitting device 1 is located on the top of the furnace body and emits infrared light waves into the furnace chamber 2. The graphene heating film 4 is wrapped around the outer wall of the furnace chamber 2, and the temperature detection unit is a temperature sensor 6, which uses a K-type thermocouple and is arranged at multiple points inside the furnace chamber 2 to collect temperature data of each area in real time.

[0066] The current detection unit uses a three-phase current transformer 10 and is installed on the workshop power grid bus to monitor the three-phase current in real time.

[0067] The controller uses a PLC controller 11 as the core control unit, receives signals from the temperature sensor 6 and the three-phase current transformer 10, executes the three-control loop coupled cooperative control algorithm, and outputs the power adjustment signal of the light wave emitting device 1 and the power adjustment signal of each zone of the graphene heating film 4 respectively.

[0068] The physical nature of the infrared light wave used in this invention to heat non-ferrous metals is completely different from that of electromagnetic induction heating. Infrared light waves belong to the electromagnetic wave family, and their energy quanta are called photons. When infrared photons are incident on the metal surface, they interact with free electrons and lattice phonons in the metal. The photon energy is absorbed and converted into lattice vibration energy, which macroscopically manifests as an increase in the metal temperature.

[0069] The absorption of infrared radiation by metals follows the Bouguer-Lambert Law, and the attenuation of radiation intensity along the penetration depth is as follows:

[0070]

[0071] In the formula, Intensity of the incident light wave Let z be the light intensity at depth z. λ represents the absorption coefficient of the metal at wavelength λ. For zinc alloys (Zn-Al system), experimental measurements show that the absorption coefficient in the mid-infrared band of 3μm-5μm is... The corresponding radiation penetration depth is approximately 20μm-100μm.

[0072] Although the penetration depth may seem small in terms of numerical value alone, the key lies in the fact that the photon energy of the infrared radiation precisely matches the energy range of the phonons vibrating in the lattice of the non-ferrous metal, which can efficiently excite the optical phonon mode and achieve strong photon-phonon coupling. This coupling effect allows the absorbed infrared energy to be rapidly and uniformly distributed throughout the lattice through phonon-phonon scattering, thereby achieving uniform heating throughout the entire volume.

[0073] Please see Figure 1 In one embodiment, the inner wall of the furnace 2 is provided with an inner lining, and the surface of the inner lining is coated with an infrared reflective coating 12.

[0074] In this embodiment, the inner lining is selected as a high-temperature resistant ceramic fiber inner lining 3, and the surface of the high-temperature resistant ceramic fiber inner lining 3 is coated with an infrared reflective coating 12 to reflect scattered infrared radiation back to the molten pool 5 region, thereby improving energy utilization.

[0075] In the actual smelting process, the light waves penetrate the metal surface not only once, but the infrared reflective coating 12 on the inner wall of the furnace 2 causes the scattered infrared radiation to undergo multiple reflections within the furnace 2 (Multi-pass Effect), significantly amplifying the equivalent penetration depth. Part of the infrared radiation emitted from the top of the light wave emitting device 1 directly enters the molten pool 5 surface, while the other part is reflected by the sidewall reflective coating and enters the molten pool 5 from different angles, forming a three-dimensional, surrounding radiation field that ensures uniform heating in all areas of the molten pool 5.

[0076] Please see Figure 7 In one embodiment, when smelting zinc alloy, the infrared light emitted by the light emitting device 1 has a wavelength range of 2μm-10μm, preferably 3μm-5μm, which matches the infrared absorption peak of zinc or zinc alloy in the molten state.

[0077] In this embodiment, the selection of light wavelength is a key technical parameter for achieving efficient bulk heating in this invention, and its scientific basis is based on the following three levels of theoretical analysis and experimental verification:

[0078] Infrared absorption spectroscopy analysis of zinc alloy: The experimentally measured infrared absorption spectrum of zinc alloy shows a significant strong absorption band in the 3μm-5μm infrared range. This absorption band originates from the electronic transitions between the lattice defect energy levels and the conduction band introduced by Al atoms in the Zn-Al alloy, as well as the enhanced phonon-photon coupling effect in the ZnO surface film. Within this band, the normal spectral emissivity of the zinc alloy... > 0.90, spectral absorbance .

[0079] Wien's Displacement Law and Temperature Matching: According to the theory of blackbody radiation, the peak wavelength of a thermal radiator... With absolute temperature Satisfies Wien's displacement law:

[0080] ;

[0081] In the formula, Let be the Wien displacement constant. The operating temperature range for zinc alloy smelting is 420℃-480℃, corresponding to an absolute temperature of approximately 693K-753K. Substituting into Wien's displacement law, the calculation is as follows:

[0082] ;

[0083] Calculation results show that the peak wavelength of blackbody radiation corresponding to the zinc alloy smelting working temperature is exactly around 3.85 μm, falling within the 3 μm-5 μm band. This means that the 3 μm-5 μm infrared radiation emitted by the light wave emitting device 1 matches the re-radiation wavelength of the zinc alloy molten liquid itself, achieving optimal overlap of the "emission-absorption" spectrum and maximizing the radiative heat transfer efficiency.

[0084] Overall Energy Conversion Efficiency Calculation: Considering both absorptivity and emissivity, the overall energy conversion efficiency of the light wave heating system can be estimated as follows:

[0085] ;

[0086] in The reflectivity coefficient of the infrared reflective coating 12 is shown. The overall efficiency can reach over 73%, far exceeding the 60%-70% of electromagnetic induction heating. If the heat recovery effect of the graphene isothermal system is further taken into account, the overall thermal efficiency of the system can exceed 85%.

[0087] Please see Figure 2 In one embodiment, the graphene heating film 4 is divided into multiple independently controllable partitions.

[0088] In this embodiment, a partitioned layout structure is adopted (e.g., Figure 2 As shown in the figure, it includes the bottom area and the side wall area, and each zone is independently powered and controlled.

[0089] Please see Figure 1 , Figure 2 In one embodiment, the graphene heating film 4 is divided into a bottom region and multiple sidewall regions distributed along the height direction of the sidewalls, and each region is independently powered and independently regulated.

[0090] In this embodiment, Figure 2The diagram shows the 4-partition layout of the graphene heating film. The diagram details the five partitions of the graphene heating film 4: the first region 21 is the bottom region, the second region 22 is the lower part of the sidewall, the third region 23 is the middle and lower part of the sidewall, the fourth region 24 is the upper and middle part of the sidewall, and the fifth region 25 is the upper part of the sidewall.

[0091] Please see Figures 5 to 9 In one embodiment, the temperature control loop adopts a composite control strategy combining PID control and fuzzy control, and outputs power adjustment signals for each partition of the graphene heating film 4 based on the weighted fusion value of multi-point temperature.

[0092] In this embodiment, the temperature of the molten pool 5 is taken as the controlled object, and the power of each zone of the graphene heating film 4 is taken as the execution variable. A composite control strategy of PID + fuzzy control is adopted.

[0093] The composite control strategy includes: using PID control as the basic algorithm, performing proportional-integral-derivative calculations based on the deviation between the target temperature and the actual temperature, and outputting the basic heating power of each zone's heating unit; when the temperature deviation exceeds a preset threshold, fuzzy control algorithm is activated, and the PID control parameters or the power allocation weights of each zone's heating unit are dynamically adjusted according to the magnitude and trend of the temperature deviation.

[0094] Temperature sensors 6 are arranged at 9 points inside furnace 2. The collected temperature data is processed by a weighted fusion algorithm to obtain the comprehensive temperature of the molten pool 5. :

[0095] , ;

[0096] Among them, the weighting coefficient The settings are based on the geometric position of each temperature measuring point relative to the center of the molten pool 5 and the distribution of the heat flow field, with the bottom central region having the highest weight. The upper region of the sidewall has the smallest weight. ).

[0097] Temperature deviation The deviation change rate is used as the input variable of the fuzzy controller. The target temperature is set for the process. The fuzzy controller uses the Mamdani inference mechanism and a 7×7 rule base is designed. Based on the fuzzy control output, the PID controller performs fine compensation.

[0098] The power grid balancing circuit uses the three-phase current of the workshop power grid as the monitoring object and the power redistribution between the three phases in each section of the graphene heating film 4 as the control means.

[0099] The three-phase current transformer 10 collects three-phase current in real time. , , Calculate the three-phase unbalance factor:

[0100] ;

[0101] in, The average current is used, and a power redistribution algorithm is triggered when β > 5%. Constraints include: temperature in each zone within ±3℃ of the target temperature; power in each zone within its upper and lower limits; and total power conservation.

[0102] In one embodiment, the synergistic heating circuit is configured as follows:

[0103] During the heating phase, the light wave emitting device 1 is controlled to heat at the main power, and the graphene heating film 4 is heated at the auxiliary power.

[0104] During the constant temperature stage, the light wave emitting device 1 is controlled to reduce to the maintenance power or turn off, and the graphene heating film 4 is responsible for precise temperature control.

[0105] In this embodiment, the collaborative heating circuit adopts a master-slave control strategy, which dynamically allocates the heating power of light waves and graphene based on the deviation between the current temperature of the molten pool 5 and the set temperature.

[0106] Heating phase (ΔT > 20℃): Light wave power dominates heating, with graphene as an auxiliary agent. Transition phase (10℃ < ΔT ≤ 20℃): Light wave power decreases, graphene power increases, and the two work in a smooth transition. Isothermal phase (ΔT ≤ 10℃): Light wave power is reduced to maintenance power or turned off, and graphene dominates precise temperature control.

[0107] Figure 3 This is a flowchart of the three-control-loop coupled and coordinated control logic of the present invention. The diagram shows in detail the control logic of the three control loops and their coupling relationships. Three coupling points are marked in the diagram: coupling point A is the branching and synchronization point of the temperature deviation signal, coupling point B is the constraint transmission point of power distribution, and coupling point C is the hard constraint point of the total power upper limit.

[0108] The three-control loop coupled and coordinated control system of this invention produces a significant "1+1+1>3" synergistic effect. Using light wave heating alone, the temperature control accuracy is only about ±10℃; using graphene alone requires 3-4 hours to heat up; and using power grid balancing alone is decoupled from the smelting process. The synergy of these three elements achieves the optimal overall system effect of rapid heating (approximately 45 minutes), precise temperature control (±3℃), and a superior power grid (imbalance <5%). Light wave heating is responsible for "speed," graphene for "accuracy," and power grid balancing for "stability." Through unified scheduling and coupled coordination by the PLC controller 11, these three elements maximize their effectiveness in their respective areas of strength.

[0109] In one embodiment, an automatic liquid supply system is further included, the automatic liquid supply system comprising:

[0110] The automatic feeding mechanism 7 is located on the upper side of the furnace body;

[0111] The molten pool 5 is located at the bottom of the furnace chamber 2;

[0112] A metering pump 8 is connected to the molten pool 5;

[0113] And a delivery pipe 9 connecting the metering pump 8 to an external die-casting machine, the outer wall of which is wrapped with a graphene heating film 4 for heat preservation.

[0114] In this embodiment, the molten pool 5 is located at the bottom of the furnace 2 to contain the molten metal. The automatic feeding mechanism 7 is used to automatically weigh and feed the metal ingots. The quantitative liquid supply pump 8 is connected to the bottom of the molten pool 5 and pumps the molten metal quantitatively to the conveying pipe 9. The outer wall of the conveying pipe 9 is wrapped with a graphene heating film 4 for heat preservation.

[0115] This invention also provides an intelligent temperature control method for a non-ferrous metal light wave melting furnace, the method comprising the following steps:

[0116] The temperature at multiple locations within furnace 2 and the three-phase current of the power grid are collected in real time.

[0117] Based on the deviation between the collected temperature and the target temperature, the heating power of each zone of the light wave emitting device 1 and the graphene heating film 4 is adjusted through the temperature control loop.

[0118] The three-phase imbalance is calculated based on the collected three-phase current. When the three-phase imbalance exceeds a preset threshold, the power of each section of the graphene heating film 4 is redistributed among the three-phase power grid through the power grid balancing circuit.

[0119] Based on the current smelting stage, the power distribution ratio between the light wave emitting device 1 and the graphene heating film 4 is dynamically adjusted through a collaborative heating circuit.

[0120] Specific Implementation Case 1 of Zinc Alloy Smelting: The light wave emitting device 1 employs a six-group infrared light wave generator array arranged on the top of the furnace body, each group with a rated power of 15kW, for a total power of 90kW. The light wave generators use silicon carbide rods (SiC) or halogen lamps as emission sources, with an emission spectrum covering the 2μm-10μm band. Optical filters limit the main emission band to the 3μm-5μm range. The power of each group of light wave generators is independently adjusted via solid-state relays (SSRs), with an adjustment resolution of 0.5kW and a response time of <100ms.

[0121] The furnace chamber 2 adopts a cylindrical structure with an inner diameter of 800mm and a height of 1000mm. It is made of heat-resistant stainless steel (such as 310S) with a wall thickness of 8mm. A high-temperature resistant ceramic fiber lining 3 is tightly installed on the inner wall of the furnace chamber 2. This lining uses polycrystalline mullite fiber modules with a density of 128kg / m³, a temperature resistance rating of 1200℃, and a lining thickness of 150mm. The inner surface of the ceramic fiber lining 3 is coated with an infrared reflective coating 12. The coating material is a zirconium oxide (ZrO2) based high-temperature infrared reflective coating with a reflectivity >92% in the 3μm-5μm wavelength range.

[0122] The graphene heating film 4 has a total area of ​​approximately 3.02 m² across its five zones. The graphene heating film 4 is a single-layer or multi-layer graphene film prepared using chemical vapor deposition (CVD), with a sheet resistivity controlled within the range of 50 Ω / sq-200 Ω / sq and a surface power density designed to be 1.5 kW / m²-2.0 kW / m². Each zone has a rated power of 5 kW, for a total power of 25 kW.

[0123] Temperature sensor 6 uses a type K thermocouple (NiCr-NiSi) with a total of 9 points: 1 point at the bottom center of the molten pool 5, 1 point at the bottom edge, 1 point at the lower part of the side wall, 2 points at the middle of the side wall, 2 points at the upper middle of the side wall, and 2 points 50mm below the surface of the molten pool 5. The thermocouple signals are transmitted to the PLC controller 11 via a temperature transmitter (4-20mA output). The temperature sampling period is 100ms, and the measurement accuracy is ±1℃.

[0124] The automatic feeding mechanism 7 includes a storage hopper, an automatic weighing unit, and a tipping feeding mechanism. The storage hopper has a capacity of 100kg / time, an automatic weighing accuracy of ±0.5kg, and a feeding cycle that can be set (usually replenished every 15-20 minutes).

[0125] The metering pump 8 is an electromagnetic pump, which utilizes the interaction between an alternating magnetic field and the induced current in the molten metal to generate electromagnetic force to drive the flow of the molten metal. It has no moving mechanical parts, is high-temperature resistant, and maintenance-free. The rated flow rate of the pump is continuously adjustable from 0-50 kg / min, with a supply accuracy of ±1 kg / min. The conveying pipeline 9 is made of high-temperature resistant stainless steel (50 mm inner diameter), extending from the molten pool 5 to each die-casting machine (three die-casting machines in this embodiment), with a maximum conveying distance of 10 m. The outer wall of the pipeline is entirely wrapped with a graphene heating film 4 insulation strip to maintain the temperature of the zinc alloy liquid inside the pipe above 400°C, with a temperature loss of <5°C during the conveying process.

[0126] The three-phase current transformer 10 is a split-core CT with a transformation ratio of 1000:5 and an accuracy of 0.5 class. It is installed on the low-voltage side bus of the workshop transformer to collect three-phase current in real time. The three-phase unbalance calculation cycle is 1 second, and power redistribution is triggered when β > 5%. The five graphene zones are connected to different phase lines of the three-phase power grid: the first zone 21 is connected to phase A, the second zone 22 is connected to phase B, the third zone 23 is connected to phase C, the fourth zone 24 is connected to phase A, and the fifth zone 25 is connected to phase B.

[0127] The PLC controller 11 adopts the Siemens S7-1200 series (CPU 1214C DC / DC / DC), configured with 16 analog inputs and 16 analog outputs. The human-machine interface uses a 10-inch touchscreen (MCGS TPC series), providing functions such as temperature setting, real-time curve display, energy consumption statistics, and fault alarms. The main functional modules of the control system include: temperature acquisition and display, optical power control, graphene zone control, power grid balancing, liquid supply control, data logging, and alarm protection.

[0128] To further illustrate the superiority of the three-loop coupled coordinated control of the present invention, consider the following extreme contradictory condition: During the isothermal stage, the temperature Tfusion of the molten pool 5 has stabilized at 450°C, and the target value Tset is 450°C. At this time, the current Ia of phase A of the power grid suddenly increases, causing the three-phase imbalance β to surge from 3% to 12%. Any existing independent control system would be in trouble as a result: if only grid balancing is performed, the power of the heating unit connected to phase A will be reduced, which will inevitably disrupt the precise isothermal state; if only isothermal control is maintained, the power grid will be severely unbalanced.

[0129] Under the mechanism of the control system of this invention, coupling points B and C immediately cooperate (see reference). Figure 3The power grid balancing circuit calculates that the load on phase A needs to be reduced by approximately 5kW, and this requirement is transmitted as a "constraint" to the zoned constant temperature control circuit. Under the condition of satisfying the total heat load balance, the constant temperature control circuit immediately reduces the power of the first zone 21 and the fourth zone 24 connected to phase A by 2.5kW each, while simultaneously increasing the power of the second zone 22, the third zone 23, and the fifth zone 25 connected to phases B and C by a total of 5kW. This adjustment is completed within 100ms. The result is that the temperature fluctuation of the molten pool 5 is controlled within ±1℃ (maintaining a constant total heat input through uniform compensation in each zone), and the three-phase imbalance decreases from 12% to 4.5% within one control cycle, recovering to below the set threshold. This specific operating condition fully demonstrates the unexpected technical effect of the cooperative control of this invention compared to the "1+1+1>3" effect of an independent control system.

[0130] Specific Implementation Case 2 of Zinc Alloy Smelting:

[0131] Compared to the 500kg furnace model in the specific implementation case, this embodiment has been scaled up and its parameters adjusted in the following aspects:

[0132] Furnace chamber 2 dimensions: inner diameter Φ1000mm, height 1300mm, wall thickness 10mm. The volume of furnace chamber 2 is increased to approximately 1.02m³, with an effective molten liquid capacity of 1000kg.

[0133] Light wave emitting device 1: It adopts an array of 8 infrared light wave generators, with a single group power of 18kW and a total power of 144kW. It is arranged in a 2×4 rectangular array on the top of the furnace body.

[0134] The graphene heating film has a 48-zone layout: the number of zones in the graphene heating film 4 is increased from 5 to 8. The bottom area is divided into 2 zones, and the side wall area is divided into 6 zones (3 layers along the height, each layer containing 2 semi-circular arc zones). Each of the 8 zones is independently powered and temperature-controlled, with a single zone power of 6kW and a total power of 48kW.

[0135] Temperature sensor arrangement: The number of temperature detection points increased from 9 to 15. The weighted fusion algorithm adjusted the weight coefficients accordingly.

[0136] The 1000kg large molten pool 5 has the capacity to supply liquid to more die-casting machines. This embodiment is configured with a dual-pump parallel configuration (one in use and one on standby), with a single pump flow rate of 0-50kg / min and a total liquid supply capacity of 0-80kg / min. The delivery pipeline 9 adopts a branch-flow design, which can supply liquid to 5-8 die-casting machines simultaneously.

[0137] Specific Implementation Case of Aluminum Alloy Smelting 3:

[0138] Aluminum (Al) and zinc (Zn) exhibit significantly different absorption characteristics in the infrared band. From a solid-state physics perspective, the plasma frequency of free electrons in a metal determines its optical behavior in the infrared band. Aluminum has a significantly higher free electron density than zinc, resulting in a higher plasma frequency and a corresponding shift of the infrared absorption edge towards shorter wavelengths. Experimentally measured emissivity curves of the normal spectrum of pure aluminum show that aluminum has a high emissivity in the 2μm-4μm band (ελ ≈ 0.75-0.85), while in the region with wavelengths greater than 5μm, the emissivity rapidly decreases to below 0.3. Therefore, for aluminum alloy smelting, the preferred wavelength range should be adjusted to 2μm-4μm.

[0139] The melting point of aluminum alloy (pure aluminum 660℃) is higher than that of zinc alloy (approximately 420℃), therefore the operating temperature should be adjusted accordingly to 660℃-720℃. The temperature resistance rating of the ceramic fiber lining 3 needs to be increased to above 1400℃, using zirconium-containing polycrystalline mullite fiber or alumina fiber. The infrared reflective coating 12 needs to be replaced with an alumina (Al2O3)-based high-temperature coating. The temperature sensor 6 should be replaced with an N-type thermocouple or an R-type thermocouple.

[0140] The power parameters need to be increased accordingly: the total power of the light wave emitting device 1 should be increased to 120kW-180kW; the total power of the graphene heating film 4 should be increased to 35kW-50kW. The liquid supply pump should be made of a special material resistant to aluminum liquid corrosion (such as a silicon nitride ceramic pump body), and the inner diameter of the delivery pipe 9 should be increased to Φ60mm to compensate for the flow resistance caused by the high viscosity of the aluminum liquid.

[0141] This invention employs infrared light waves for non-contact volume heating of non-ferrous metals, fundamentally overcoming the physical limitations of the skin effect in electromagnetic induction heating. The light wave heating process does not generate electromagnetic stirring, thus fundamentally suppressing metal oxidation and burn-off. A composite control strategy using a 4-zone graphene heating film arrangement, multi-point temperature detection, PID control, and fuzzy control algorithms achieves furnace temperature control accuracy within ±3℃, a 5-7 times improvement over the ±15℃-±20℃ temperature control accuracy of traditional induction furnaces. It innovatively couples constant temperature control with three-phase power grid balance control, reducing three-phase imbalance from >15% in traditional induction furnaces to <5%, and improving the power factor to over 0.95, eliminating the need for additional reactive power compensation devices and harmonic mitigation equipment.

[0142] The key technical indicators of each embodiment of the present invention are compared with those of existing electromagnetic induction melting technology in the following table:

[0143]

[0144] This invention not only has significant technical and economic benefits, but also important industrial and social value: it fills a domestic gap by combining light wave heating technology with graphene intelligent constant temperature technology for the first time and applying it to the field of non-ferrous metal smelting; the technology has good scalability and can be extended to the smelting and processing of various non-ferrous metals such as aluminum alloys, copper alloys, and magnesium alloys; it is highly compatible with the national "dual carbon" strategy, equipment upgrading policies, and intelligent manufacturing policies, and has the inherent advantages of obtaining policy support and priority market promotion.

[0145] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0146] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A non-ferrous metal light wave melting furnace, characterized in that, include: Furnace body; A light wave emitting device is installed on the top of the furnace body to emit infrared light waves into the furnace chamber; A graphene heating film is wrapped around the outer wall of the furnace body; Temperature detection unit, used to collect temperature data at multiple locations inside the furnace in real time; The current detection unit is used to detect the three-phase current of the power grid in real time. The controller is connected to the light-emitting device, the graphene heating film, the temperature detection unit, and the current detection unit, respectively. The controller is configured to perform three-loop coupled and coordinated control, wherein the three control loops include: The temperature control loop adjusts the heating power of the light wave emitting device and the graphene heating film based on the deviation between the temperature fed back by the temperature detection unit and the target temperature. The power grid balancing circuit calculates the three-phase imbalance based on the three-phase current fed back by the current detection unit, and redistributes the power when the three-phase imbalance exceeds a preset threshold. The collaborative heating circuit dynamically adjusts the power distribution ratio between the light wave emitting device and the graphene heating film according to the melting stage.

2. The non-ferrous metal light wave melting furnace according to claim 1, characterized in that, The inner wall of the furnace is lined with an infrared reflective coating.

3. The non-ferrous metal light wave melting furnace according to claim 1, characterized in that, When smelting zinc alloy, the infrared light emitted by the light emitting device has a wavelength range of 2μm-10μm.

4. The non-ferrous metal light wave melting furnace according to claim 3, characterized in that, When smelting zinc alloys, the wavelength range of the infrared light emitted by the light emitting device is preferably 3μm-5μm.

5. A non-ferrous metal light wave melting furnace according to claim 1, characterized in that, The graphene heating film is divided into multiple independently controllable zones.

6. A non-ferrous metal light wave melting furnace according to claim 1, characterized in that, The graphene heating film is divided into a bottom region and multiple sidewall regions distributed along the height of the sidewalls. Each region is independently powered and independently regulated.

7. A non-ferrous metal light wave melting furnace according to claim 5, characterized in that, The temperature control loop adopts a composite control strategy combining PID control and fuzzy control, and outputs power adjustment signals for the graphene heating film in each zone based on the weighted fusion value of multi-point temperature.

8. A non-ferrous metal light wave melting furnace according to claim 1, characterized in that, The synergistic heating circuit is configured as follows: During the heating phase, the light wave emitting device is controlled to heat at the dominant power, while the graphene heating film is heated at the auxiliary power. During the constant temperature phase, the light wave emitting device is controlled to reduce to a maintenance power or shut down, and precise temperature control is dominated by the graphene heating film.

9. A non-ferrous metal light wave melting furnace according to claim 1, characterized in that, It also includes an automatic liquid supply system, which comprises: An automatic feeding mechanism is installed on the upper side of the furnace body; The molten pool located at the bottom of the furnace; A metering pump connected to the molten pool; And a delivery pipe connecting the metering pump to an external die-casting machine, the outer wall of which is wrapped with a graphene heating film for heat preservation.

10. A smart temperature control method for a non-ferrous metal light wave smelting furnace, characterized in that, The method is implemented based on the non-ferrous metal light wave melting furnace according to any one of claims 1-9; the method includes the following steps: Real-time acquisition of temperature at multiple locations within the furnace and three-phase current from the power grid; Based on the deviation between the collected temperature and the target temperature, the heating power of each section of the light wave emitting device and the graphene heating film is adjusted through a temperature control loop. The three-phase imbalance is calculated based on the collected three-phase current. When the three-phase imbalance exceeds a preset threshold, the power of each section of the graphene heating film is redistributed among the three-phase power grid through the power grid balancing circuit. Based on the current smelting stage, the power distribution ratio between the light wave emitting device and the graphene heating film is dynamically adjusted through a synergistic heating circuit.

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