Vacuum smelting process and device for nanocrystalline master alloy

Abstract

This invention discloses a vacuum smelting process and apparatus for nanocrystalline master alloys, belonging to the field of metallurgical technology. The process includes: calculating the maximum allowable temperature rise rate limited by vacuum degree based on the differential balance of transient gas release kinetics and actual pumping capacity; calculating the safe temperature rise rate limited by thermal stress by combining crucible deformation characteristics and safety boundaries, and determining the actual safe temperature rise rate by taking the minimum value; obtaining the initial power distribution based on this target and the electromagnetic skin effect; entering the liquid alloying stage, using negative feedback to regulate the power distribution based on the physicochemical properties and thermodynamic characteristics of the added elements to maintain the refining temperature; holding at a preset temperature, and calculating the precise deoxidation refining time based on the target oxygen content, mass transfer characteristics, and multi-component thermodynamic equilibrium partial pressure characteristics, ending the refining process upon completion. This invention achieves efficient, safe, and high-purity control of master alloy smelting through multi-parameter dynamic interaction and feedforward compensation.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and in particular relates to a vacuum smelting process and apparatus for nanocrystalline master alloys. Background Technology

[0002] Nanocrystalline alloys, due to their excellent soft magnetic properties, high permeability, and low iron loss, have extremely broad application prospects in fields such as power electronics, high-frequency transformers, and new energy vehicle motors. The purity (especially the extremely low residual oxygen content) and compositional uniformity of the nanocrystalline master alloy directly determine the microstructure and macroscopic magnetic properties of the thin strip after subsequent strip spinning and chilling. Currently, the industrial industry tends to use vacuum induction melting (VIM) technology to prepare nanocrystalline master alloys.

[0003] However, traditional vacuum smelting processes are highly dependent on the experience of operators and suffer from the following technical bottlenecks: During solid heating, the heating rate is often controlled based on experience. If the heating is too fast, the violent venting of the furnace charge can easily cause a sudden drop in vacuum and glow discharge arcing. At the same time, the huge temperature difference between the inner and outer walls of the crucible will generate extremely high thermal shock stress, leading to crucible cracking and steel leakage. During the liquid alloying stage, the addition of highly exothermic elements such as silicon (Si) and boron (B) is accompanied by a violent exothermic reaction. Traditional processes, lacking precise calculation of feedforward enthalpy, are prone to causing the molten pool temperature to boil out of control instantly, which not only exacerbates the volatilization and burning loss of elements but also poses a safety hazard to the furnace. The holding time during the refining and deoxidation period is usually based on fixed empirical values. If the refining time is too short, deoxidation will be insufficient and the residual oxygen content will exceed the standard; if the refining time is too long, not only will it waste electrical energy, but it will also aggravate the corrosion of the crucible refractory material by the high-temperature molten steel, causing the re-dissolution of elements such as oxygen and aluminum in the refractory material, resulting in secondary pollution of the master alloy.

[0004] Therefore, there is an urgent need for a vacuum smelting process and apparatus for nanocrystalline master alloys that can couple multiple physical fields and thermodynamic parameters to achieve dynamic and precise control throughout the entire process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a vacuum smelting process and apparatus for nanocrystalline master alloys, thus solving the aforementioned problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a vacuum smelting process for nanocrystalline master alloys, comprising: S10. Based on the differential balance between transient venting dynamics and the actual pumping capacity of the system, calculate the maximum allowable temperature rise rate that limits the vacuum level. S20. Combining the thermodynamic deformation characteristics, geometric constraints and stress safety boundary of the crucible, calculate the crucible thermal stress limit safe temperature rise rate and take the minimum value of the crucible and the vacuum limit maximum allowable temperature rise rate as the actual safe temperature rise rate. S30. Using the actual safe temperature rise rate as the input target, and combining the characteristics of the electromagnetic skin effect, the overall thermal efficiency of the equipment, the electromagnetic coupling efficiency, and the geometric characteristics of the material particles, the initial power distribution is obtained. S40. Entering the liquid alloying stage, the initial power distribution is controlled by negative feedback, taking into account the physicochemical properties of the added elements, the actual yield of the engineering process, and the thermodynamic characteristics of the alloying reaction, so as to maintain the temperature within the preset refining temperature range. S50. Maintain the temperature within the preset refining temperature range and keep the vacuum under the preset refining pressure. Combine the target and initial oxygen content mass fraction, physical and kinetic mass transfer characteristics and multi-component thermodynamic equilibrium partial pressure characteristics to calculate the precise deoxidation refining time. The refining ends when the time is up, and the nanocrystalline master alloy is obtained.

[0007] Based on the above technical solutions, the present invention also provides the following optional technical solutions: Further technical solutions: The parameters in each control step are limited as follows: In S10, the transient venting kinetics are characterized by the physical forward factor and desorption activation energy of gas desorption from the material surface; the actual pumping capacity of the system is characterized by the actual effective pumping speed of the vacuum system and the maximum allowable vacuum deterioration rate threshold. In S20, the thermodynamic deformation characteristics of the crucible include thermal diffusivity, Poisson's ratio, Young's modulus, and coefficient of linear expansion; the geometric constraints and stress safety boundaries include the outer diameter, inner diameter, engineering geometric safety factor, and maximum allowable tensile thermal stress of the crucible. In S30, the electromagnetic skin effect characteristics include the operating frequency of the medium-frequency induction power supply, the vacuum permeability, the relative permeability of the material, and the physical conductivity; the overall thermal efficiency of the equipment is the overall thermal efficiency of the induction furnace; the electromagnetic coupling efficiency is the actual electromagnetic coupling coefficient of the induction coil; and the geometric characteristics of the material particles are the average equivalent diameter of the solid particles charged into the furnace. In S40, the physicochemical properties of the added elements include the mass fraction and molar mass of the added elements; the thermodynamic characteristics of the alloying reaction include the absolute value of the molar exothermic enthalpy and the reaction time window. In S50, the physical and kinetic mass transfer characteristics include the effective surface area of ​​the molten pool, the macroscopic density of the alloy liquid, the basic liquid film mass transfer coefficient, and the electromagnetic stirring intensity correction coefficient; the multi-component thermodynamic equilibrium partial pressure characteristics include the molar mass of carbon and oxygen, the initial carbon content mass fraction, the Wagner activity coefficient of carbon and oxygen in the multi-component alloy liquid, the preset refining pressure, and the carbon-oxygen reaction equilibrium constant.

[0008] Further technical solution: In S10, the calculation logic for the maximum allowable temperature rise rate limited by vacuum degree is as follows: The maximum allowable temperature rise rate of the vacuum level limit is positively correlated with the combined product of the maximum allowable vacuum level deterioration rate threshold and the actual effective pumping speed of the vacuum system. It is also subject to the inverse modulation of the exponential thermal desorption attenuation factor, which is jointly mapped by the physical pre-exponential factor of gas desorption from the material surface, the desorption activation energy, the ideal gas constant, and the absolute temperature of the material in the furnace.

[0009] Further technical solution: In step S20, the calculation logic for determining the actual safe temperature rise rate during the solid heating period includes: Based on the maximum allowable tensile thermal stress, thermal diffusivity and engineering geometric safety factor of the crucible material, a thermal shock resistance benchmark for the material is established. Based on the Poisson's ratio, Young's modulus, coefficient of linear expansion of the crucible material, and the outer and inner diameters of the crucible, a thermodynamic stress conversion factor is constructed. The safe temperature rise rate of the crucible under thermal stress is the limit output after the thermal shock tolerance benchmark of the material is inversely mapped by the thermodynamic stress conversion factor; The actual safe temperature rise rate is determined by minimizing the limit boundary value between the crucible thermal stress-limited safe temperature rise rate and the vacuum degree-limited maximum allowable temperature rise rate output by S10.

[0010] Further technical solution: In S30, the initial power distribution calculation logic is configured as follows: The combined product of the total mass of material charged into the furnace, the average isobaric specific heat capacity of the furnace charge in solid state, and the actual safe temperature rise rate is used as the benchmark sensible heat demand power. Based on the operating frequency of the medium-frequency induction power supply, vacuum permeability, relative permeability of the material, physical conductivity, and average equivalent diameter of the solid particles charged into the furnace, an electromagnetic skin penetration attenuation factor is constructed. The initial power distribution is the result of amplification and compensation of the baseline sensible heat demand power after considering the system energy transmission barrier established by the comprehensive thermal efficiency of the induction furnace, the actual electromagnetic coupling coefficient of the induction coil, and the electromagnetic skin penetration attenuation factor.

[0011] Further technical solution: In S40, the corrected power distribution is calculated using feedforward enthalpy compensation logic. Extract the total number of added elements, and for each added element, based on its mass fraction, engineering yield, molar mass and absolute value of molar mixed exothermic enthalpy, combined with the total mass of the material charged into the furnace, integrate and sum to obtain the total equivalent of alloying exothermic heat. The total exothermic equivalent of the alloying is converted into an equivalent heat compensation power by time-domain amortization based on the reaction time window and the comprehensive thermal efficiency of the induction furnace. The corrected power distribution is the result of subtracting the equivalent heat compensation power from the initial power distribution output by S30.

[0012] Further technical solution: In S50, the precise deoxidation and refining time is calculated based on the steady-state carbon-oxygen dynamic loss driving force logic solution: The precise deoxygenation refining time is directly proportional to the total mass of the material and the macroscopic deoxygenation flux, which is jointly determined by the difference between the initial oxygen content mass fraction and the set target residual oxygen content mass fraction. The precise deoxygenation refining time is inversely constrained by the comprehensive deoxygenation mass transfer rate; the comprehensive deoxygenation mass transfer rate includes the physical fluid dynamics mass transfer factor and the effective deoxygenation mass transfer driving force. The physical fluid dynamics mass transfer factor is determined by the combined factors of the effective surface area of ​​the molten pool, the macroscopic density of the alloy liquid, the basic liquid film mass transfer coefficient, and the electromagnetic stirring intensity correction coefficient. The effective deoxidation mass transfer driving force is the difference between the average actual oxygen mass fraction of the alloy liquid during the refining process and the equilibrium oxygen mass fraction under the preset refining conditions. The equilibrium oxygen mass fraction is calculated based on the preset refining pressure, carbon-oxygen reaction equilibrium constant, Wagner activity coefficients of carbon and oxygen elements in the multi-component alloy liquid, and average effective carbon mass fraction, according to the thermodynamic equilibrium relationship of the carbon-oxygen reaction.

[0013] A further technical solution: The logic configuration for calculating the overall thermal efficiency of the induction furnace is as follows: The overall thermal efficiency is the percentage of effective power in the total active power output of the induction power supply during the calibration test, after deducting the system water cooling power and the power lost by spatial thermal radiation. The system's water-cooled heat dissipation power is derived from the volumetric flow rate, density, specific heat capacity at constant pressure, and temperature difference between the inlet and outlet water of the induction coil cooling water. The spatial heat radiation loss power is derived from the Stefan-Boltzmann constant, the system's comprehensive thermal radiation emissivity, effective surface area, and the fourth power difference between the absolute temperature of the material inside the furnace and the absolute temperature of the surrounding environment under calibration conditions.

[0014] Further technical solution: The nanocrystalline master alloy mainly contains Fe, Si, B, Nb and Cu elements, and the added elements in S40 include Si and B.

[0015] A further technical solution: the preset initial vacuum threshold and the preset refining pressure both range from 0.1 to 0.5. The preset refining temperature range is 1500-1540°C. .

[0016] A vacuum smelting apparatus for nanocrystalline master alloys, employing the aforementioned vacuum smelting process for nanocrystalline master alloys, includes a vacuum induction furnace, a copper roller with a cooling system (which can be cooled by circulating water) installed inside the vacuum induction furnace, and a crucible installed inside the induction furnace.

[0017] This invention provides a vacuum smelting process and apparatus for nanocrystalline master alloys, which has the following advantages compared with the prior art: 1. This invention combines transient gas release dynamics with the differential balance of the system's pumping capacity, as well as the thermodynamic deformation and geometric constraints of the crucible, to dynamically optimize the actual safe temperature rise rate. This mechanism can automatically match the pumping bottleneck of the vacuum pump with the thermal shock limit of the crucible material, thus eliminating the arcing phenomenon and the risk of crucible thermal cracking during solid heating from the root. 2. In the liquid alloying stage, this invention introduces feedforward enthalpy compensation logic. By combining the physicochemical and thermodynamic characteristics of the added elements (such as Si and B), engineering yield, and molar mixing exothermic enthalpy, the initial power distribution is controlled in real time with negative feedback. This effectively counteracts the drastic temperature rise during the combination of highly exothermic elements, avoids boiling and splashing of the molten pool, and greatly improves the absorption rate and composition stability of highly active elements. 3. By coupling physical mass transfer parameters with multi-component activity coefficients (Wagner activity coefficients), vacuum degree and other thermodynamic equilibrium partial pressure characteristics, the system can accurately calculate the deoxidation refining time required to achieve the target oxygen content. This ensures extremely low residual oxygen content and avoids crucible erosion and secondary pollution caused by over-refining. 4. This invention transforms abstract and complex metallurgical physicochemical reactions (such as electromagnetic skin effect, carbon-oxygen reaction, and activity interaction) into physical correlation operator mappings that can be solved in real time by the control system, realizing a fully closed-loop control from cold heating to the end of refining, which significantly improves the batch stability and production efficiency of nanocrystalline master alloys. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process of the present invention.

[0019] Figure 2 This is a logic block diagram of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0022] Please see Figure 1 The present invention provides a vacuum smelting process for nanocrystalline master alloys, comprising: S10. Based on the differential balance between transient venting dynamics and the actual pumping capacity of the system, calculate the maximum allowable temperature rise rate that limits the vacuum level. S20. Combining the thermodynamic deformation characteristics, geometric constraints and stress safety boundary of the crucible, calculate the crucible thermal stress limit safe temperature rise rate and take the minimum value of the crucible and the vacuum limit maximum allowable temperature rise rate as the actual safe temperature rise rate. S30. Using the actual safe temperature rise rate as the input target, and combining the characteristics of the electromagnetic skin effect, the overall thermal efficiency of the equipment, the electromagnetic coupling efficiency, and the geometric characteristics of the material particles, the initial power distribution is obtained. S40. Entering the liquid alloying stage, the initial power distribution is controlled by negative feedback, taking into account the physicochemical properties of the added elements, the actual yield of the engineering process, and the thermodynamic characteristics of the alloying reaction, so as to maintain the temperature within the preset refining temperature range. S50. Maintain the temperature within the preset refining temperature range and keep the vacuum under the preset refining pressure. Combine the target and initial oxygen content mass fraction, physical and kinetic mass transfer characteristics and multi-component thermodynamic equilibrium partial pressure characteristics to calculate the precise deoxidation refining time. The refining is completed when the time is up to obtain the nanocrystalline master alloy. In this invention, the criteria for entering the liquid alloying stage are as follows: when the control system detects a sudden change in the infrared radiation characteristics of the material surface inside the furnace (from diffuse reflection on a solid rough surface to specular reflection on a liquid surface), and the temperature feedback value measured by the bottom thermocouple reaches the liquidus temperature of the base metal (e.g., 1480°C - 1500°C) and remains there for a set time (e.g., 2 minutes) with a fluctuation rate of less than 1%, the system determines that the base metal is fully melted. At this time, the control system outputs a feeding command to add the necessary elements.

[0023] The parameter constraints for each control step are as follows: In S10, the transient venting kinetics are characterized by the physical forward factor and desorption activation energy of gas desorption from the material surface; the actual pumping capacity of the system is characterized by the actual effective pumping speed of the vacuum system and the maximum allowable vacuum deterioration rate threshold. In S20, the thermodynamic deformation characteristics of the crucible include thermal diffusivity, Poisson's ratio, Young's modulus, and coefficient of linear expansion; the geometric constraints and stress safety boundaries include the outer diameter, inner diameter, engineering geometric safety factor, and maximum allowable tensile thermal stress of the crucible. In S30, the electromagnetic skin effect characteristics include the operating frequency of the medium-frequency induction power supply, the vacuum permeability, the relative permeability of the material, and the physical conductivity; the overall thermal efficiency of the equipment is the overall thermal efficiency of the induction furnace; the electromagnetic coupling efficiency is the actual electromagnetic coupling coefficient of the induction coil; and the geometric characteristics of the material particles are the average equivalent diameter of the solid particles charged into the furnace. In S40, the physicochemical properties of the added elements include the mass fraction and molar mass of the added elements; the thermodynamic characteristics of the alloying reaction include the absolute value of the molar exothermic enthalpy and the reaction time window. In S50, the physical and kinetic mass transfer characteristics include the effective surface area of ​​the molten pool, the macroscopic density of the alloy liquid, the basic liquid film mass transfer coefficient, and the electromagnetic stirring intensity correction coefficient; the multi-component thermodynamic equilibrium partial pressure characteristics include the molar mass of carbon and oxygen, the initial carbon content mass fraction, the Wagner activity coefficient of carbon and oxygen in the multi-component alloy liquid, the preset refining pressure, and the carbon-oxygen reaction equilibrium constant.

[0024] The following example will provide a more detailed explanation of the above technical solution: Suppose that in a factory at location A, user A is responsible for operating a vacuum induction furnace for producing nanocrystalline master alloys. The factory previously faced some challenges in the smelting process: during the solid heating stage, due to improper control of the heating rate, the vacuum level inside the furnace often dropped sharply, and even glow discharge arcing occurred. At the same time, the crucible also occasionally cracked. During the liquid alloying stage, when alloying elements such as silicon and boron were added, the temperature of the molten pool would spike instantly, resulting in element volatilization loss and posing a safety hazard to the furnace. During the refining and deoxidation stage, because the holding time was a fixed empirical value, the oxygen content of the final alloy fluctuated greatly. Sometimes the deoxidation was insufficient, and sometimes the refining time was too long, resulting in wasted energy.

[0025] To address these issues, the plant introduced the aforementioned vacuum smelting process for nanocrystalline master alloys. During the initial solid heating phase, the system first executes step S10. Instead of relying on user A's experience, it dynamically calculates the maximum permissible rate of temperature rise at the current temperature based on the transient gas desorption kinetics of the material inside the furnace (e.g., through pre-measured data on the gas desorption rate of the material at different temperatures) and the actual pumping capacity of the vacuum system (e.g., the real-time effective pumping speed of the vacuum pump and the plant-set maximum vacuum deterioration threshold). This ensures that the vacuum level does not deteriorate drastically.

[0026] Simultaneously, the system executes step S20 in parallel, combining the thermodynamic deformation characteristics of the crucible (e.g., the thermal diffusivity and coefficient of linear expansion of the crucible material) with its geometric constraints and stress safety boundaries (e.g., the inner and outer diameters of the crucible and the maximum allowable tensile thermal stress of the material) to accurately calculate the safe temperature rise rate that the crucible can withstand under the current conditions, thus avoiding cracking caused by thermal stress. Subsequently, the system automatically compares these two calculated temperature rise rates and takes the minimum of the two as the actual safe temperature rise rate for the current stage. For example, if the vacuum-limited temperature rise rate is 5 K / s, while the crucible's thermal stress-limited temperature rise rate is 3 K / s, the system will automatically select 3 K / s as the actual temperature rise rate.

[0027] Next, the system enters step S30, using the actual safe temperature rise rate as the target, and combining the characteristics of the electromagnetic skin effect (e.g., the operating frequency of the induction power supply, the conductivity of the material, etc.), the overall thermal efficiency of the equipment, the electromagnetic coupling efficiency, and the particle geometry of the material being charged, to accurately calculate the initial power distribution required. User A only needs to start the program, and the system can automatically adjust the power to ensure that the material in the furnace heats up at the safest and most efficient rate.

[0028] When the control system detects a sudden change in the infrared radiation characteristics of the material surface inside the furnace (from diffuse reflection on a solid, rough surface to specular reflection on a liquid surface), and the temperature feedback value from the bottom thermocouple reaches the liquidus temperature of the base metal and remains below 1% for a set time, the system determines that the base metal is fully melted and outputs a feeding command. User A adds silicon and boron as instructed, at which point the process enters the S40 liquid alloying stage. The system combines the physicochemical properties of these added elements (e.g., their mass fraction, molar mass) and the thermodynamic characteristics of the alloying reaction (e.g., the absolute value of the molar exothermic enthalpy of silicon and boron reacting with iron) to regulate the power distribution through a negative feedback mechanism. For example, since the addition of silicon and boron is accompanied by a violent exothermic reaction, the system pre-calculates this exothermic heat and correspondingly reduces the power distribution, thereby precisely maintaining the molten pool temperature within the preset refining temperature range of 1500-1540 °C, avoiding the previous temperature runaway boiling phenomenon.

[0029] After holding at a preset refining temperature range and maintaining a vacuum at a preset refining pressure (e.g., 0.1-0.5 Pa), the process proceeds to step S50. The system combines the target and initial oxygen content mass fraction, the physical and kinetic mass transfer characteristics of the molten pool (e.g., effective surface area of ​​the molten pool, macroscopic density of the alloy melt, electromagnetic stirring intensity correction coefficient), and multi-component thermodynamic equilibrium partial pressure characteristics (e.g., carbon-oxygen reaction equilibrium constant, Wagner activity coefficient of carbon and oxygen in the alloy melt) to accurately calculate the precise deoxidation refining time required to achieve the target residual oxygen content. For example, if the initial oxygen content is high, the system will calculate a longer refining time; if the target oxygen content is low, it will be extended accordingly. Once the calculated time expires, the system automatically terminates the refining process, obtaining a highly pure and uniformly composed nanocrystalline master alloy.

[0030] In traditional smelting processes, the heating rate during the solid heating period is often set empirically, which can easily lead to a sudden drop in vacuum, glow discharge arcing, and crucible cracking due to excessive thermal stress. In contrast, this process, through steps S10 and S20, achieves dynamic calculation of the temperature rise rate limited by both vacuum and crucible thermal stress, and takes the minimum of these two values ​​as the actual safe temperature rise rate. This precise calculation based on multi-physics coupling effectively avoids the safety hazards and equipment damage risks associated with traditional empirical settings, ensuring the stability and safety of the heating process.

[0031] In the liquid alloying stage, traditional processes, when adding highly exothermic elements such as silicon and boron, are prone to sudden uncontrolled boiling of the molten pool temperature due to a lack of precise calculation of the feedforward enthalpy. This exacerbates element volatilization and burn-off, posing safety hazards to the furnace. This process, through steps S30 and S40, obtains the initial power distribution based on the actual safe temperature rise rate. During the liquid alloying stage, it combines the physicochemical properties of the added elements with the thermodynamic characteristics of the alloying reaction for negative feedback control. This forward-looking enthalpy calculation and dynamic power adjustment mechanism allows the molten pool temperature to be precisely maintained within the preset refining temperature range, significantly reducing element burn-off, improving the uniformity of the alloy composition, and eliminating the safety risks caused by temperature runaway.

[0032] Furthermore, during the refining and deoxidation period, traditional processes typically employ fixed, empirically-based holding times. This can lead to insufficient deoxidation, excessive residual oxygen content, or excessively long refining times, increased energy consumption, and secondary contamination. This process, through the S50 step, combines the target and initial oxygen content mass fractions, physical kinetic mass transfer characteristics, and multi-component thermodynamic equilibrium partial pressure characteristics to calculate a precise deoxidation and refining time. This dynamic time calculation based on real-time parameters and thermodynamic equilibrium ensures the sufficiency and efficiency of the deoxidation process, avoiding the problems of insufficient or over-refining caused by traditional fixed-time methods. This improves the purity of the master alloy, reduces production costs, and minimizes the risk of erosion and secondary contamination of the crucible refractory material.

[0033] In summary, the aforementioned vacuum smelting process for nanocrystalline master alloys overcomes the significant technical bottlenecks in the heating, alloying, and refining stages of traditional empirical smelting processes by introducing coupled calculations of multi-physics fields and thermodynamic parameters and dynamic and precise control throughout the entire process. This process achieves intelligent, safe, and efficient smelting, providing a solid technical guarantee for the preparation of high-purity and high-uniformity nanocrystalline master alloys.

[0034] Preferably, in step S10, the calculation logic for limiting the maximum allowable temperature rise rate under vacuum is as follows: The maximum allowable temperature rise rate of the vacuum level limit is positively correlated with the combined product of the maximum allowable vacuum level deterioration rate threshold and the actual effective pumping speed of the vacuum system. It is also subject to the inverse modulation of the exponential thermal desorption attenuation factor, which is jointly mapped by the physical forward factor of gas desorption from the material surface, the desorption activation energy, the ideal gas constant, and the absolute temperature of the material in the furnace. Specifically, in S10, the formula for calculating the maximum allowable temperature rise rate limited by the vacuum degree is as follows: ; in, Indicates the maximum permissible rate of temperature rise under vacuum conditions (unit: ), This represents the maximum permissible rate of vacuum degradation threshold (in units of...). ), The actual effective pumping speed of the vacuum system (unit: ), Represents the ideal gas constant (unit: ). ), This indicates the absolute temperature of the material currently inside the furnace (unit: ). ), The physical exponent factor (in units) represents the physical pre-exponential factor for gas desorption from the material surface. ), The desorption activation energy of gas on the material surface (unit: ) ), This represents the exponential thermal desorption attenuation factor.

[0035] The calculation formula It represents the maximum rate of temperature rise that the material inside the furnace can withstand under the current vacuum environment and material conditions, and its calculation results directly guide the subsequent setting of heating power. This is the preset upper limit for the vacuum deterioration rate. Its setting can be determined based on the vacuum pump's performance parameters, the process's stringent vacuum requirements, or historical production data. For example, it can be set to 0.01. Or 0.05 To prevent a sharp drop in vacuum level during heating, the preset upper limit of vacuum level deterioration rate is set. The method for obtaining the threshold value is as follows: The critical glow discharge threshold test method is used for experimental calibration. Specifically, under the condition of an empty vacuum induction furnace with a normal smelting intermediate frequency voltage applied, inert gas is introduced into the vacuum furnace chamber at an increasing rate through a fine-tuning gas filling valve, artificially creating a dynamically deteriorating vacuum environment. Simultaneously, an optical sensor and a current fluctuation monitoring system are used to capture the critical pressure rise rate at the moment the glow discharge (arc striking) is triggered inside the furnace. This critical rate is multiplied by a preset engineering safety redundancy coefficient, and the result is used as the upper limit of the preset vacuum degree (i.e., preset refining pressure) deterioration rate called at the bottom layer of the control system. . This refers to the effective pumping capacity of a vacuum system under actual operating conditions. This value can be obtained by comprehensively evaluating factors such as the nameplate parameters of the vacuum pump, performance curves, and pipeline resistance, or by receiving real-time feedback from an online monitoring system. is the ideal gas constant, a known physical constant. It is the real-time absolute temperature of the material inside the furnace, which is usually accurately measured by devices such as infrared thermometers or thermocouples. and It is a key parameter characterizing the gas desorption properties of material surfaces, among which As a physical pre-exponential factor, it reflects the frequency of desorption reactions, while The desorption activation energy represents the minimum energy required for the desorption reaction. These two parameters are usually obtained experimentally or by consulting relevant material databases. Together, they determine the outgassing rate of the material at different temperatures and the physical pre-exponential factor of gas desorption from the material surface. With desorption activation energy The method for obtaining the data is as follows: calibration is performed using the dual-heating-rate quasi-equilibrium venting method. The specific steps are as follows: extract materials from the same batch and place them in a vacuum chamber, recording the system pressure during the heating process. ) and absolute temperature ( The relationship between the two is such that the gas release kinetics follow the model: Under dynamic equilibrium conditions, the pressure and the venting rate satisfy ( The pressure response equation is obtained as follows: Transform it into a linear form for regression: By least squares fitting the slope and intercept Desorption activation energy is obtained Physical pre-exponential factor Exponential thermal desorption attenuation factor This comprehensively reflects the dynamic changes in gas desorption during the heating process of materials.

[0036] The scheme in this application establishes a differential equilibrium relationship between the transient gas release kinetics of materials and the actual pumping capacity of the vacuum system through the above calculation formula. Specifically, the numerator of the formula... This reflects the gas load capacity that the vacuum system can effectively handle under the maximum permissible vacuum degradation rate threshold. The denominator is... This quantifies the gas desorption rate of the material due to heating at the current temperature. By dynamically matching the gas handling capacity of the vacuum system with the actual gas release rate of the material, the formula can calculate in real time the maximum temperature rise rate that the material can withstand without exceeding the preset vacuum deterioration threshold. This dynamic balance allows the smelting process to adaptively adjust the heating strategy according to changes in the material's state and the vacuum system's performance, thereby maximizing heating efficiency while ensuring vacuum stability.

[0037] The following is a concrete example to illustrate this. Suppose we are smelting a nanocrystalline master alloy in a vacuum induction furnace, and the maximum permissible rate of vacuum degradation threshold of the vacuum system is... Set to 0.02 The actual effective pumping speed of the vacuum system 12 ideal gas constant It is 8.314 The current absolute temperature of the material inside the furnace. 1200 Based on previous tests of this nanocrystalline master alloy material, the physical exponent factor of gas desorption on its surface was... 150 Desorption activation energy 180 By substituting these parameters into the above calculation formula, the maximum allowable temperature rise rate under vacuum conditions at the current moment can be calculated in real time. For example, the calculation result might be 0.5. This means that under current conditions, the material can safely heat up by 0.5 Kelvin per second without causing the vacuum level to deteriorate beyond the preset threshold. This calculation result will serve as an important basis for subsequent adjustments to the heating power.

[0038] The above technical solution allows for precise quantification and dynamic determination of the maximum permissible temperature rise rate under the current vacuum system capacity and material venting characteristics. This avoids the vacuum level deteriorating beyond the threshold due to excessively rapid temperature rise, thus affecting smelting quality, and also avoids reduced production efficiency due to excessively slow temperature rise. Therefore, while ensuring the high purity requirements of vacuum smelting, the efficiency and controllability of the heating process are optimized.

[0039] Preferably, in step S20, the calculation logic for determining the actual safe temperature rise rate during the solid heating period includes: Based on the maximum allowable tensile thermal stress, thermal diffusivity and engineering geometric safety factor of the crucible material, a thermal shock resistance benchmark for the material is established. Based on the Poisson's ratio, Young's modulus, coefficient of linear expansion of the crucible material, and the outer and inner diameters of the crucible, a thermodynamic stress conversion factor is constructed. The safe temperature rise rate of the crucible under thermal stress is the limit output after the thermal shock tolerance benchmark of the material is inversely mapped by the thermodynamic stress conversion factor; The actual safe temperature rise rate is determined by minimizing the limit boundary between the crucible thermal stress-limited safe temperature rise rate and the vacuum degree-limited maximum allowable temperature rise rate output by S10. Specifically, in step S20, the formula for calculating the actual safe temperature rise rate during the solid heating period is as follows: ; ; in, Indicates the crucible's thermal stress-limited safe temperature rise rate (unit: ), Indicates the geometric safety factor of the crucible. Indicates the maximum allowable tensile thermal stress of the crucible material (unit: ), Indicates the thermal diffusivity of the crucible material (unit: ). ), The Poisson's ratio represents the material of the crucible. Young's modulus of the crucible material (unit: ), The coefficient of linear expansion of the crucible material (unit: 1000 m²) ), Indicates the outer diameter of the crucible (unit: ), Indicates the inner diameter of the crucible (unit: ). ), Indicates the actual safe temperature rise rate (unit: ), Indicates the maximum permissible rate of temperature rise under vacuum conditions (unit: ), Indicates the thermal shock resistance standard of the material. Represents the thermodynamic stress conversion factor. This indicates the search for the limit boundary.

[0040] Crucible thermal stress limits safe temperature rise rate ( The engineering geometric safety factor (EMF) refers to the maximum permissible rate of temperature rise while ensuring the structural integrity and safety of the crucible. Its calculation comprehensively considers the thermodynamic properties, geometric dimensions, and engineering safety margins of the crucible material, aiming to avoid destructive stresses caused by uneven thermal expansion or excessive temperature gradients. Determining this rate is crucial to ensuring the safe operation of the smelting process. The engineering geometric safety factor (GMD) is used to provide additional safety margins in engineering design and can be determined based on empirical data, industry standards, or specific application risk assessments. For example, it can range from 0.5 to 0.9, or be adjusted according to the brittleness and service life requirements of the crucible material. The method for obtaining the data is as follows: physical calibration is performed using the thermal shock damage comparison test method. The specific operation is as follows: first, obtain the theoretical critical cracking temperature difference value of the material and design dimensions under a defect-free ideal state. Subsequently, spare crucibles from the same batch were subjected to destructive thermal shock quenching tests, which involved rapidly heating them to different temperature steps and then quickly subjecting them to forced water cooling or air cooling quenching. The actual critical temperature difference at which microcracks appeared on the surface of the crucible was recorded. The engineering geometric safety factor is given by the formula. This coefficient, calculated as a reduction parameter less than 1, is used in the algorithm to compensate for the stress concentration effect caused by micro-defects in the actual crucible processing. The maximum allowable tensile thermal stress of the crucible material ( The thermal diffusivity (TDP) of the crucible material refers to the maximum tensile stress that the material can withstand at high temperatures. Exceeding this stress may lead to material failure. This parameter is usually obtained through material mechanics experiments or material performance data provided by the supplier, such as through tensile or creep tests. The Poisson's ratio (Pr) characterizes the rate of heat transfer within the crucible material. A higher thermal diffusivity means that heat can be distributed more evenly within the material more quickly, thereby reducing local temperature gradients and thermal stress. This parameter can be determined experimentally using methods such as the transient hot wire method or the laser scintillation method. The Young's modulus (YM) is the ratio of the absolute values ​​of transverse strain to axial strain when a material is subjected to uniaxial force. It reflects the trend of transverse dimensional changes in a material when it expands or contracts due to heat. This parameter can be determined by static tensile testing or ultrasonic testing. The Young's modulus of the crucible material (YM) The Young's modulus is a physical quantity that measures the ease with which a material undergoes elastic deformation. It represents the material's ability to resist deformation within its elastic range. A higher Young's modulus means that the material deforms less under the same stress, but it may also lead to greater thermal stress accumulation. This parameter can be determined through tensile or bending tests. The coefficient of linear expansion (CDO) of the crucible material... The outer diameter ( ) represents the relative change in length of a material as temperature changes. It directly affects the thermal expansion of the crucible during heating and is a crucial parameter for calculating thermal stress. This parameter can be measured using a thermal dilatometer. ) and inner diameter ( The geometric dimensions of the crucible, collectively determining the crucible wall thickness, significantly influence heat transfer and thermal stress distribution. Wall thickness is a key geometric factor in calculating thermal stress, and these parameters can be obtained through direct measurement or design drawings. Actual safe temperature rise rate (… ( ) is the maximum allowable temperature rise rate during the solid heating stage, taking into account both vacuum level limitations and crucible thermal stress limitations. It is determined by taking the maximum allowable temperature rise rate limited by vacuum level ( ) and crucible thermal stress limiting safe temperature rise rate ( The minimum value of is used to determine the limit boundary, ensuring that under no circumstances will the smelting process cause the vacuum system to run out of control or the crucible to be damaged due to excessively rapid temperature rise. This is a decision-making mechanism used to select the most stringent constraints among multiple interdependent factors. In this scheme, it ensures that during the vacuum smelting process, the actual rate of temperature rise will neither cause the vacuum level to deteriorate beyond the allowable range nor subject the crucible to excessive thermal stress, thereby achieving process robustness and safety.

[0041] In the solid heating phase of the vacuum smelting process for nanocrystalline master alloys, this application considers not only the limitation of vacuum degree on the temperature rise rate but also the limitation of crucible thermal stress to ensure the stability of the smelting process and the safety of the equipment. Specifically, in S20, based on the thermodynamic deformation characteristics of the crucible (such as thermal diffusivity, Poisson's ratio, Young's modulus, and coefficient of linear expansion), geometric constraints (such as the outer and inner diameters of the crucible), and stress safety boundaries (such as the engineering geometric safety factor and the maximum allowable tensile thermal stress), the crucible thermal stress-limited safe temperature rise rate is calculated using a specific calculation formula. This rate reflects the maximum rate of temperature rise that the crucible can withstand without thermal stress failure. Subsequently, this safe temperature rise rate limited by thermal stress is compared with the maximum permissible temperature rise rate limited by vacuum level calculated in S10 above. The two values ​​are compared, and the smaller value is taken as the final actual safe rate of temperature rise. This strategy of minimizing the value, i.e., optimizing the limit boundary, ensures that the temperature rise rate is always within the strictest limits allowed by the vacuum system and crucible structure safety throughout the entire solid heating process. In this way, this scheme effectively avoids the problem of excessive crucible thermal stress that may be caused by considering only the vacuum limit, thereby ensuring the continuity of the smelting process, the long-term reliability of the equipment, and the stability of product quality.

[0042] As a specific implementation method, in the solid heating stage of the vacuum smelting process for nanocrystalline master alloys, a high-purity graphite crucible can be used for smelting. This graphite crucible material possesses specific thermal diffusivity, Poisson's ratio, Young's modulus, and coefficient of linear expansion, parameters which can be obtained by consulting material handbooks or conducting experimental tests. For example, an engineering geometric safety factor can be set to ensure sufficient safety margin in actual operation. Simultaneously, based on the characteristics of graphite material, its maximum allowable tensile thermal stress can be determined. The outer and inner diameters of the crucible are obtained from design drawings or actual measurements. During the smelting process, the control system acquires the temperature of the material inside the furnace in real time and, combined with the actual pumping capacity of the vacuum system and the maximum allowable vacuum deterioration rate threshold, calculates the maximum allowable temperature rise rate limited by the vacuum level. Simultaneously, using the aforementioned crucible material and geometric parameters, a preset calculation model is used to calculate the safe temperature rise rate limited by the crucible's thermal stress in real time. Finally, the control system compares these two calculated temperature rise rates and selects the smaller one as the actual safe temperature rise rate at the current moment. For example, if the allowable temperature rise rate limited by the vacuum level is 5... The allowable temperature rise rate due to crucible thermal stress limitation is 3. The system will then set the actual temperature rise rate to 3. In this way, the power output of the induction heating power supply will be adjusted according to this actual safe temperature rise rate to ensure that during the heating process, neither the vacuum level will deteriorate due to excessive gas release nor the crucible will be damaged due to excessive thermal stress.

[0043] The above technical solution allows for comprehensive consideration of the physical limitations of the vacuum environment and crucible material during the solid heating stage of vacuum smelting of nanocrystalline master alloys. By introducing the calculation of the safe temperature rise rate limited by crucible thermal stress and comparing it with the maximum allowable temperature rise rate limited by vacuum, the minimum value is taken to determine the actual safe temperature rise rate. This makes the temperature rise control during the smelting process more precise and safe, effectively avoiding the risk of crucible thermal stress concentration, deformation, or even cracking due to excessively rapid temperature rise, significantly extending the service life of the crucible, and reducing equipment maintenance costs. Simultaneously, this dual-limitation temperature rise control strategy ensures the stability of the vacuum degree and the reliability of the process throughout the heating process, laying a solid foundation for the subsequent liquid alloying and refining stages, thereby improving the production efficiency and product quality of nanocrystalline master alloys.

[0044] Preferably, in step S30, the initial power distribution calculation logic is configured as follows: The combined product of the total mass of material charged into the furnace, the average isobaric specific heat capacity of the furnace charge in solid state, and the actual safe temperature rise rate is used as the benchmark sensible heat demand power. Based on the operating frequency of the medium-frequency induction power supply, vacuum permeability, relative permeability of the material, physical conductivity, and average equivalent diameter of the solid particles charged into the furnace, an electromagnetic skin penetration attenuation factor is constructed. The initial power distribution is the result of amplification and compensation of the baseline sensible heat demand power after considering the system energy transmission barrier jointly established by the comprehensive thermal efficiency of the induction furnace, the actual electromagnetic coupling coefficient of the induction coil, and the electromagnetic skin penetration attenuation factor. Specifically, in step S30, the formula for calculating the initial power distribution is: ; in, Indicates the initial power distribution (unit: ), This indicates the total mass of materials loaded into the furnace (in units of...). ), This represents the average isobaric specific heat capacity of the furnace charge in the solid state (unit: ). ), Indicates the actual safe temperature rise rate (unit: ), This indicates the overall thermal efficiency of the induction furnace. This represents the actual electromagnetic coupling coefficient of the induction coil. Indicates the average equivalent diameter of the solid particles charged into the furnace (unit: ), Indicates the operating frequency of the intermediate frequency induction power supply (unit: ), Vacuum permeability (unit: ), Indicates the relative magnetic permeability of the material. The physical conductivity of a material (in units of 1000 kJ / m²) ), Pi is a constant. This indicates the reference sensible heat demand power. Indicates the electromagnetic skin penetration attenuation factor. This indicates a barrier to energy transmission in the system.

[0045] Initial power distribution This refers to the electrical power that the induction power supply needs to provide to the induction coil during the solid-state heating stage of vacuum induction smelting. Its function is to provide heat to the material inside the furnace, causing its temperature to rise at a preset rate. (Total mass of material) This refers to the total mass of all materials to be melted in the induction furnace. This parameter is used to calculate the total energy required to heat the materials. The average isobaric specific heat capacity of the furnace charge in the solid state. This represents the amount of heat required to raise the temperature of a unit mass of material by one unit temperature in its solid state. This value can be obtained by consulting material handbooks, conducting experimental measurements, or performing thermodynamic calculations. Actual safe temperature rise rate. This is determined based on the limitations of the vacuum system and crucible; it represents the maximum allowable heating rate of the material during the solid-state heating stage, and this rate is the target that the control system needs to achieve during the heating process. The overall thermal efficiency of the induction furnace... This refers to the efficiency with which an induction furnace converts input electrical energy into effective thermal energy of the material. It comprehensively considers the heat losses of components such as the induction coil, furnace lining, and cooling system. This efficiency can be obtained through equipment thermal balance calibration, for example, by measuring cooling water temperature rise and radiation losses, or estimated using empirical data or data provided by the equipment manufacturer. The actual electromagnetic coupling coefficient of the induction coil... This coefficient represents the efficiency of electromagnetic energy coupling between the induction coil and the material inside the furnace. It is affected by various factors such as coil structure, material shape and position, and operating frequency. Its value can be set through electromagnetic field simulation calculations, experimental measurements, or based on experience. The actual electromagnetic coupling coefficient of the induction coil... The method for obtaining the data is as follows: The calorimeter thermal balance calibration method (short-circuit loop method) is used for testing. Specifically, a standard water-cooled copper short-circuit loop with known physical conductivity and relative magnetic permeability is placed in the working area of ​​the induction furnace crucible to simulate the material load; the induction power supply is then connected to apply a known total active power. Heating is performed while simultaneously measuring the copper loss power of the induction coil's cooling water. Simultaneously monitor the inlet and outlet temperature difference and volumetric flow rate of the short-circuit ring cooling water, and calculate the actual heat power absorbed by the load based on the calorimetric equation. Ultimately, through relational expressions The actual electromagnetic coupling coefficient was obtained. The average equivalent diameter of the solid particles charged into the furnace was also determined. This refers to the average size of the solid particles charged into the furnace. This parameter is crucial for assessing the impact of the electromagnetic skin effect on particulate materials and can be determined through material sieving analysis, image processing statistics, or empirical values. The operating frequency of the medium-frequency induction power supply... This refers to the frequency of the alternating current output by the induction power supply. This frequency is a key parameter affecting the depth of the electromagnetic skin effect and is usually determined by the model and settings of the induction power supply. Vacuum permeability. It is a physical constant representing the magnetic permeability in a vacuum. (Relative magnetic permeability of a material) This represents the magnetic permeability of a material relative to a vacuum. For ferromagnetic materials, its value is much greater than 1, while for non-magnetic materials it is close to 1. This value can be obtained by consulting material property databases or through experimental measurement. The physical electrical conductivity of the material. The electromagnetic skin penetration attenuation factor is a physical quantity representing the conductivity of a material. This value can be obtained by consulting a material handbook or through experimental measurement. The electromagnetic skin penetration attenuation factor is a correction coefficient used to quantify the impact of the electromagnetic skin effect during heating. When the induced current forms a skin effect on the conductor surface, heat is mainly concentrated in the surface layer, leading to a decrease in internal heating efficiency. This factor considers factors such as material particle size, operating frequency, magnetic permeability, and electrical conductivity, correcting for the effectiveness of energy transfer. The system energy transfer barrier integrates the overall thermal efficiency of the induction furnace, the actual electromagnetic coupling coefficient of the induction coil, and the electromagnetic skin penetration attenuation factor, collectively characterizing the losses and efficiency limitations in the entire energy transfer chain from the power source outputting electrical energy to the material actually absorbing heat energy.

[0046] The solution proposed in this application achieves refined management of the heating process by introducing a calculation formula for the initial power distribution. This solution is first based on the total mass of the material. Average isobaric specific heat capacity of furnace charge in solid state and the actual safe temperature rise rate determined by the preceding steps. The baseline sensible heat demand required for the material to reach the target heating rate under ideal conditions was calculated. However, practical induction heating systems suffer from energy loss and transmission efficiency issues. Therefore, this scheme further considers the overall thermal efficiency of the induction furnace. And the actual electromagnetic coupling coefficient of the induction coil This reflects the efficiency of electrical energy conversion into heat energy. More importantly, the scheme introduces an electromagnetic skin penetration attenuation factor, which comprehensively considers the average equivalent diameter of the solid particles charged into the furnace. The operating frequency of the intermediate frequency induction power supply Vacuum permeability Relative magnetic permeability of materials and the physical conductivity of the material These parameters precisely quantified the impact of the electromagnetic skin effect on the heating process of particulate materials. By dividing the baseline sensible heat demand by the system energy transfer barrier constituted by these efficiency and attenuation factors, the initial power distribution required by the induction power supply can be accurately calculated. This calculation method ensures that the material can be heated strictly according to the actual safe temperature rise rate during the solid-state heating stage, avoiding problems such as vacuum deterioration or excessive thermal stress in the crucible that may be caused by setting the power based on experience, thereby achieving precise control and optimization of the heating process.

[0047] As a specific implementation method, assuming that when smelting nanocrystalline master alloys in a vacuum induction furnace, the total mass of materials charged into the furnace is... 100 Average isobaric specific heat capacity of furnace charge in solid state For 500 The actual safe temperature rise rate calculated based on the preceding steps. It is 0.3 Overall thermal efficiency of induction furnace The actual electromagnetic coupling coefficient of the induction coil is calibrated to 0.75 by the equipment. The average equivalent diameter of the solid particles charged into the furnace is 0.85. It is 0.01 (i.e., 10) The operating frequency of the intermediate frequency induction power supply The relative magnetic permeability of the material is 2000 Hz. Physical conductivity is 100 (for iron-based alloys). for Vacuum permeability for .

[0048] First, calculate the baseline sensible heat demand power: .

[0049] Next, the electromagnetic skin penetration attenuation factor is calculated: .

[0050] Then, calculate the energy transfer barrier of the system: .

[0051] Finally, calculate the initial power distribution: .

[0052] Therefore, the initial power distribution of the inductive power supply can be set to approximately 34.48. This is to ensure that the material can be heated at 0.3 during the solid-state heating stage. The actual safe temperature rise rate is used for heating.

[0053] The above technical solution enables precise calculation of the initial power required for the solid-state heating stage in the vacuum smelting process of nanocrystalline master alloys. This effectively solves the technical challenge of accurately controlling the heating power according to a preset safe temperature rise rate in complex vacuum smelting environments. The solution fully considers key factors such as the thermophysical properties of the material, the energy transfer efficiency of the induction heating system, and the electromagnetic skin effect, avoiding potential risks such as vacuum degradation and excessive thermal stress in the crucible caused by inaccurate power settings. Therefore, it ensures the stability and safety of the smelting process, improves energy utilization efficiency, and lays a solid foundation for the smooth progress of subsequent liquid alloying and refining stages, ultimately contributing to the acquisition of high-quality nanocrystalline master alloy products.

[0054] Preferably, in step S40, the corrected power distribution is calculated using feedforward enthalpy compensation logic: Extract the total number of added elements, and for each added element, based on its mass fraction, engineering yield, molar mass and absolute value of molar mixed exothermic enthalpy, combined with the total mass of the material charged into the furnace, integrate and sum to obtain the total equivalent of alloying exothermic heat. The total exothermic equivalent of the alloying is converted into an equivalent heat compensation power by time-domain amortization based on the reaction time window and the comprehensive thermal efficiency of the induction furnace. The corrected power distribution power is the result of subtracting the equivalent heat compensation power from the initial power distribution power output by S30. Specifically, in S40, the formula for calculating the corrected power distribution is as follows: ; in, Indicates corrected power distribution (unit: ), Indicates the initial power distribution (unit: ), This indicates the total mass of materials loaded into the furnace (in units of...). ), This indicates the total number of types of elements added. This variable represents the ordinal number of the element being added. Indicates the first The quality fraction of the added element Indicates the first The actual yield of the added elements in the project. Indicates the first Absolute value of the molar enthalpy of the added elements (in units of 1000 m²) ), Indicates the first Molar mass of each added element (in units) ), Represents the reaction time window (unit: ), This indicates the overall thermal efficiency of the induction furnace. This represents the total equivalent heat exotherm of alloying. This represents the equivalent heating compensation power.

[0055] Among them, the power distribution is corrected. This refers to the adjustment value made to the actual output electrical power of the induction furnace during the liquid alloying stage to maintain a stable furnace temperature. It represents the net electrical energy input rate that the system needs to provide after considering the heat effect of the alloying reaction. Initial power distribution This is a baseline power calculated based on the actual safe temperature rise rate during the solid heating period, primarily used for heating materials from a solid to a liquid state. (Total mass of material) This is the total amount of all materials to be melted in the furnace, and it is the basic parameter for heat calculation. Mass fraction of added elements. This indicates the proportion of a specific added element in the total material, directly affecting its amount participating in the reaction. (Engineering yield) The calculations take into account the loss or incomplete utilization of elements added during actual production to ensure that the results are closer to reality. Absolute value of molar exothermic enthalpy of mixing. Molar mass quantifies the heat released or absorbed by each mole of added element when mixed with the base metal, and is a key parameter for evaluating the heat effect of alloying. Used to convert mass fraction to molar quantity for thermodynamic calculations. Reaction time window The time period during which the alloying reaction occurs and releases or absorbs heat is defined, allowing the heat change to be converted into equivalent power. The overall thermal efficiency of the induction furnace. This reflects the efficiency of the induction furnace in converting electrical energy into effective heat energy, and is used to accurately map the calculated heat changes to the adjustment of electrical power. The total equivalent heat of alloying is the total heat generated by all added elements during the alloying process, while the equivalent heat compensation power is the power value that needs to be compensated or offset by electrical power after the total heat is evenly distributed within the reaction time window.

[0056] The solution proposed in this application addresses the temperature fluctuation problem caused by the thermal effect of the alloying reaction by introducing dynamic correction of the power distribution during the liquid alloying stage. Specifically, in S30, the system calculates the initial power distribution based on the actual safe temperature rise rate during the solid heating period. This power is primarily used to heat the materials inside the furnace to a molten state. When the control system detects that the materials inside the furnace have entered the liquid alloying stage and outputs a feeding command to introduce additive elements (such as Si and B), these additive elements undergo an alloying reaction with the base metal. Since these reactions are usually accompanied by significant exothermic or endothermic effects, if not controlled, the furnace temperature will deviate from the preset refining temperature range. Therefore, this scheme accurately calculates the "equivalent heat compensation power," which comprehensively considers the total mass of the materials. Quality score of each added element Project completion rate absolute value of exothermic enthalpy of molar mixture molar mass Response time window and the overall thermal efficiency of the induction furnace An equivalent power value is obtained by averaging the total exothermic equivalent of all added elements over the reaction time window and considering the furnace's thermal efficiency. This "equivalent exothermic compensation power" is then calculated from the initial power distribution. Subtract from the middle to obtain the corrected power distribution. If the alloying reaction is exothermic, the compensation power is positive, and the corrected power distribution will be reduced accordingly to avoid overheating. If the alloying reaction is endothermic, the compensation power is negative (or the formula is adjusted to increase the power), and the corrected power distribution will be increased accordingly to prevent temperature drop. This negative feedback control mechanism ensures that the furnace temperature can be precisely maintained within the preset refining temperature range during the alloying process, thereby guaranteeing the stability of the alloying process and the quality of the final nanocrystalline master alloy.

[0057] As a specific implementation method, in the vacuum smelting process of nanocrystalline master alloys, after the base metal (mainly Fe) in the furnace has completely melted and reached the liquidus temperature, the control system will issue a command to add elements, such as Si and B. Assume that the total mass of the material in the furnace at this point... 100 Based on the preset alloy composition, the mass fraction of Si... The mass fraction of B is 0.05. The value is 0.01. The actual yield of Si and B in engineering applications can be obtained through historical data or experimental calibration. and (e.g., 0.98 and 0.95 respectively), and the absolute values ​​of their molar exothermic enthalpy of mixing with Fe. and (For example, Si is -20) B is -30 Meanwhile, the molar mass of Si is known. Approximately 0.028 The molar mass of B Approximately 0.011 kg / mol. Setting the alloying reaction time window. The overall thermal efficiency of the induction furnace is 120 seconds. The value is 0.75. Before adding any elements, the system had already calculated the initial power distribution based on S30. Once Si and B are added to the molten pool, the control system immediately uses the above parameters to calculate the alloying exothermic equivalent of Si and B respectively, and then sums them to obtain the total alloying exothermic equivalent. For example, the exothermic equivalent of Si is: ; The heat exothermic equivalent of B is: .

[0058] Add these equivalents together and then divide by the reaction time window. Overall thermal efficiency of induction furnace This yields the "equivalent heat compensation power". Let's assume the calculated "equivalent heat compensation power" is 50.4. The system will then distribute the initial power. Subtract 50.4 The corrected power distribution is obtained. The corrected power is then used to apply negative feedback control to the induction furnace, thereby ensuring that the furnace temperature can be stably maintained at 1500-1540°C during the Si and B alloying process. The preset refining temperature range.

[0059] By precisely adjusting the power distribution during the liquid alloying stage, this application effectively counteracts the thermal effects generated by the alloying reaction of added elements, thereby maintaining the furnace temperature precisely within the preset refining temperature range. This significantly improves the temperature control accuracy and stability of the alloying process, avoiding temperature fluctuations caused by exothermic or endothermic reactions, thus ensuring the full dissolution and uniform distribution of added elements, effectively suppressing the formation of harmful phases, and ultimately obtaining a nanocrystalline master alloy with uniform composition and excellent performance. Compared to schemes that rely solely on initial power distribution, this scheme significantly improves the level of refined control of the smelting process by dynamically adjusting the power, ensuring consistent product quality.

[0060] Preferably, in S50, the precise deoxidation and refining time is calculated based on the steady-state carbon-oxygen dynamic loss driving force logic: The precise deoxygenation refining time is directly proportional to the total mass of the material and the macroscopic deoxygenation flux, which is jointly determined by the difference between the initial oxygen content mass fraction and the set target residual oxygen content mass fraction. The precise deoxygenation refining time is inversely constrained by the comprehensive deoxygenation mass transfer rate; the comprehensive deoxygenation mass transfer rate includes the physical fluid dynamics mass transfer factor and the effective deoxygenation mass transfer driving force. The physical fluid dynamics mass transfer factor is determined by the combined factors of the effective surface area of ​​the molten pool, the macroscopic density of the alloy liquid, the basic liquid film mass transfer coefficient, and the electromagnetic stirring intensity correction coefficient. The effective deoxidation mass transfer driving force is the difference between the average actual oxygen mass fraction of the alloy liquid during the refining process and the equilibrium oxygen mass fraction under the preset refining conditions. The equilibrium oxygen mass fraction is calculated based on the preset refining pressure (i.e., preset vacuum degree), carbon-oxygen reaction equilibrium constant, Wagner activity coefficients of carbon and oxygen elements in multi-component alloy liquid, and average effective carbon mass fraction, according to the thermodynamic equilibrium relationship of carbon-oxygen reaction. Specifically, in step S50, the average effective carbon mass fraction of the refining process is first determined based on the carbon consumption during the carbon-oxygen reaction process: ; Then, based on the thermodynamic equilibrium relationship of the carbon-oxygen reaction, determine the effective deoxygenation mass transfer driving force under the preset refining conditions: ; The precise deoxygenation and refining time is calculated according to the following formula: ; in, Indicates precise deoxygenation and refining time (unit: ), Indicates the total mass of materials (unit: ), This indicates the initial oxygen content by mass fraction. This indicates the set target residual oxygen content by mass fraction. Represents the effective surface area of ​​the molten pool (unit: ), The macroscopic density of the alloy liquid (unit: ), Indicates the basic liquid film mass transfer coefficient (unit: ). ), This represents the correction factor for the electromagnetic stirring intensity. This indicates the initial carbon content by mass fraction. This indicates the average effective carbon mass fraction during the refining process. Indicates standard pressure ( ), It represents the equilibrium oxygen mass fraction (the equilibrium oxygen mass fraction determined by the thermodynamic equilibrium relationship of the carbon-oxygen reaction under preset refining temperature, preset refining pressure and average effective carbon mass fraction). This indicates the preset refining pressure (the preset refining pressure used in carbon-oxygen thermodynamic balance calculations, in units of...). ), Represents the equilibrium constant for the carbon-oxygen reaction. The Wagner activity coefficient represents the carbon element in a multi-component alloy liquid. The Wagner activity coefficient represents the oxygen element in a multi-component alloy liquid. The molar mass of carbon (unit: ) ), The molar mass of oxygen (in units of 1000 mcg) ), This represents the macroscopic deoxygenation flux. Indicates the overall deoxygenation mass transfer rate. Represents the mass transfer factor in physical fluid dynamics. This indicates the driving force for effective deoxygenation and mass transfer.

[0061] The equilibrium oxygen mass fraction is determined by the thermodynamic equilibrium relationship of the carbon-oxygen reaction. The carbon-oxygen reaction is expressed as: ; The activities of carbon and oxygen in multi-component alloy melts are expressed as follows: ; ; When the equilibrium constant of the carbon-oxygen reaction is adopted as the dimensionless thermodynamic equilibrium constant When expressed, the balance relationship is: ; in, The equilibrium partial pressure of carbon monoxide at the alloy liquid-gas interface (unit: ); Under the vacuum deoxidation refining conditions of this application, a preset refining pressure is used. The equilibrium partial pressure of carbon monoxide is used to characterize the carbon-oxygen thermodynamic equilibrium calculation. The equilibrium oxygen mass fraction under the preset refining conditions is calculated from the above equilibrium relationship: ; Therefore, the result of the above formula is not a dimensionless partial pressure ratio in the general sense, but rather the equilibrium oxygen mass fraction obtained by back-calculating the carbon-oxygen reaction equilibrium relationship.

[0062] To facilitate direct use of pressure parameters in Pa by industrial control systems, standard pressure can be incorporated into the dimensionless thermodynamic equilibrium constant, defining a pressure-type apparent equilibrium constant: ; in, The unit is Pa; When the aforementioned pressure-type apparent equilibrium constant is used, the equilibrium oxygen mass fraction is equivalently expressed as: ; And because: ; therefore: ; The two expressions described above are equivalent expressions of the same carbon-oxygen reaction thermodynamic equilibrium relationship under different constant definitions, and the calculated equilibrium oxygen mass fraction is the same.

[0063] Precise deoxygenation refining time This refers to the precise time required to reduce the oxygen content in a molten alloy from its initial value to a target value during vacuum smelting. Its importance lies in ensuring the purity of the alloy, preventing increased brittleness or performance degradation due to excessive oxygen content, and avoiding increased energy consumption and reduced production efficiency caused by excessively long refining times. (Total mass of material) This refers to the total mass of the molten alloy to be refined in the furnace. This parameter can be accurately measured using a weighing sensor during furnace loading, or estimated using a furnace level sensor combined with the density of the molten alloy. Initial oxygen content (mass fraction) This refers to the mass fraction of oxygen in the molten alloy before refining begins. This value can be quickly analyzed by sampling before the furnace, or initially set based on experience data from previous smelting batches. The set target residual oxygen content mass fraction. This refers to the desired oxygen content in the molten alloy after refining; this value is typically set based on the stringent oxygen content requirements of the final product. Effective surface area of ​​the molten pool. This refers to the actual contact area between the molten alloy and the vacuum environment for gas exchange. This area is affected by factors such as the geometry of the crucible, the amount of molten alloy, and surface fluctuations caused by electromagnetic stirring. It can be monitored in real time by a vision system pre-installed in the furnace. (Mega density of the molten alloy) This refers to the overall density of the molten alloy at the refining temperature. This parameter can be obtained by consulting the physical property handbook of the relevant alloy or determined through experimental measurement. Basic liquid film mass transfer coefficient. This coefficient characterizes the rate at which oxygen atoms diffuse from the interior of the molten alloy to the surface and desorb. It is related to factors such as the viscosity, surface tension, and temperature of the molten alloy and can be determined through expert experience or experimental calibration. Electromagnetic stirring intensity correction coefficient. This coefficient is used to correct the influence of electromagnetic stirring on the mass transfer process. Electromagnetic stirring can accelerate convection inside the molten pool, thereby improving mass transfer efficiency. It can be obtained through experimental measurement and fitting of deoxidation rates under different stirring intensities, or empirically set based on the electromagnetic stirring power and frequency. (Preset refining pressure) This refers to the preset absolute pressure maintained by the vacuum system during the refining process. This pressure is monitored in real-time by a vacuum gauge and dynamically controlled by the vacuum system within a preset range. Under conditions where carbon monoxide generated from the carbon-oxygen reaction is the main gaseous product of the refining stage, and the influence of other gaseous components is negligible, the preset refining pressure is used to approximately characterize the equilibrium partial pressure of carbon monoxide at the alloy liquid-gas interface. (Carbon-oxygen reaction equilibrium constant) It describes the carbon-oxygen reaction ( The apparent equilibrium constant at a given temperature is the constant at which thermodynamic equilibrium is achieved. This constant is closely related to temperature and can be obtained by querying a thermodynamic database or by calculating from thermodynamic data. When the thermodynamic database provides a pressure-type apparent equilibrium constant, this pressure-type apparent equilibrium constant is denoted as... The Wagner activity coefficient of carbon in multi-component alloy melts is calculated by conversion with the dimensionless thermodynamic equilibrium constant. Wagner activity coefficient of oxygen in multi-component alloy liquid. This is used to correct the non-ideal behavior of carbon and oxygen in multi-component alloy liquids, reflecting the influence of other alloying elements on the activities of carbon and oxygen. The activities of carbon and oxygen are respectively determined according to... and Confirmed. Initial carbon content (mass fraction) This refers to the mass fraction of carbon in the molten alloy before refining begins. This value can be obtained through sampling and analysis before the furnace, or estimated based on empirical data from the batching and smelting process. (Molar mass of carbon) Molar mass of oxygen These are inherent physical constants of the element, which can be found in the periodic table or a chemistry handbook. Macroscopic deoxygenation flux. This represents the total amount of oxygen that needs to be removed from the molten alloy during the entire refining process. The comprehensive deoxidation mass transfer rate represents the actual rate at which oxygen is removed from the molten alloy during refining; it comprehensively considers the effects of physical mass transfer and thermodynamic equilibrium partial pressure. Physical fluid dynamics mass transfer factor. This reflects the promoting effect of the physical properties of the molten pool and the stirring intensity on oxygen mass transfer. The average actual oxygen mass fraction of the alloy melt during refining, and the effective deoxidation mass transfer driving force. This demonstrates the difference between the average actual oxygen mass fraction and the equilibrium oxygen mass fraction under the current vacuum level, temperature, and alloy composition conditions of the carbon-oxygen reaction. It should be noted that the average actual oxygen mass fraction... and balance oxygen mass fraction Both are dimensionless quantities, but they can be subtracted not only because they have the same dimensions, but also because they both represent the mass fraction of oxygen element expressed using the same mass fraction standard. Although formally calculated from pressure, equilibrium constant, activity coefficient, and carbon mass fraction, its physical meaning is not a general dimensionless pressure ratio, but rather the equilibrium oxygen mass fraction calculated from the carbon-oxygen reaction equilibrium relationship. Therefore, the subtraction in the formula is not a subtraction between the oxygen mass fraction and any partial pressure ratio, but a subtraction between the average actual oxygen mass fraction and the equilibrium oxygen mass fraction. These two are the same physical quantity, possessing the same dimensions, physical properties, and representational basis. Their difference characterizes the degree to which the carbon-oxygen reaction deviates from equilibrium. The basic liquid film mass transfer coefficient... With electromagnetic stirring intensity correction factor The method for obtaining the data is as follows: a static-dynamic deoxidation kinetics comparison calibration method is adopted. The specific operation is as follows: after the base metal is completely melted, the power is cut off to eliminate electromagnetic stirring, and natural static deoxidation is carried out using high vacuum. The residual oxygen content is sampled and recorded at regular intervals. Based on time variables Fitting an exponential decay response model without logarithmic approximation: Solve for the static deoxygenation rate constant And through the formula The basic liquid film mass transfer coefficient was obtained by conversion. Subsequently, normal power was applied to restore electromagnetic stirring, and macroscopic convection was generated in the molten pool under the action of Lorentz force. The dynamic deoxidation rate constant was obtained by repeated sampling and fitting. ; through ratio Obtain the electromagnetic stirring intensity correction coefficient under this working condition. .

[0064] This application proposes a mathematical model that comprehensively considers physical mass transfer kinetics and multi-component thermodynamic equilibrium partial pressures to accurately calculate the deoxidation and refining time of S50 during the vacuum smelting of nanocrystalline master alloys. The core of this model lies in calculating the ratio between the macroscopic deoxidation flux and the overall deoxidation mass transfer rate to determine the required precise deoxidation and refining time. Specifically, macroscopic deoxygenation flux Quantified from the initial oxygen content Reduce to target residual oxygen content The total amount of oxygen required to be removed constitutes the overall task of deoxidation refining. The overall deoxidation mass transfer rate is a dynamic parameter coupled with multiple factors, determined by both the physical fluid dynamics mass transfer factor and the effective deoxidation mass transfer driving force. The physical fluid dynamics mass transfer factor takes into account the effective surface area of ​​the molten pool. Macroscopic density of molten alloy Basic liquid film mass transfer coefficient and electromagnetic stirring intensity correction coefficient The influence of physical factors on the transport rate of oxygen atoms from the bulk liquid phase to the gas phase interface is considered. The effective deoxygenation mass transfer driving force takes into account the preset refining pressure. carbon-oxygen reaction equilibrium constant Wagner activity coefficients of carbon and oxygen elements in multi-component alloy liquids and Initial carbon content mass fraction And the molar mass of carbon and oxygen elements and The influence of thermodynamic factors on the driving force of the carbon-oxygen reaction is investigated. By organically integrating these key parameters into a unified calculation formula, this method can accurately reflect the actual dynamics of the deoxidation process, thus overcoming the problem of inaccurate estimation of deoxidation time in traditional methods. This refined calculation method enables more precise control of the deoxidation process within a preset refining temperature range and pressure, ensuring that the oxygen content in the alloy melt can efficiently and stably reach the preset target, thereby improving the control precision and product quality of the entire vacuum smelting process.

[0065] The following is a specific example. In the vacuum smelting process of nanocrystalline master alloys, when the control system detects a sudden change in the infrared radiation characteristics of the material surface inside the furnace, and the temperature feedback value from the bottom thermocouple reaches the liquidus temperature of the base metal and remains below 1% for a set time, the system determines that the base metal is fully melted and outputs a feeding command to introduce added elements, entering the liquid alloying stage. Subsequently, within a preset refining temperature range (e.g., 1500-1540°C)... Internal heat preservation, and refining at a preset pressure (e.g., 0.1-0.5). Maintaining a vacuum. At this point, to accurately determine the deoxidation refining time, the initial oxygen content mass fraction is first obtained through pre-furnace sampling and analysis. and initial carbon content mass fraction Based on the target product requirements, set the target residual oxygen content mass fraction. Total mass of materials The effective surface area of ​​the molten pool is obtained from the weighing data during furnace loading. The effective surface area of ​​the molten pool can be calculated based on the crucible size and liquid level. The method of obtaining the surface area is as follows: Considering the centripetal compression of the melt under the Lorentz force of the alternating electromagnetic field during vacuum induction smelting, the liquid surface will form a dynamic three-dimensional curved surface with a central bulge and a downward-sloping edge. To avoid model distortion caused by static planar calculation, this application constructs a nonlinear surface area calculation model based on the curvature mapping mechanism. Let the inner diameter of the crucible be... The effective surface area of ​​the molten pool The calculation formula is: In the formula, To characterize the molten pool surface morphology correction coefficient for the electromagnetic bulge effect, during the equipment calibration phase, a laser profile scanner was used to measure the three-dimensional point cloud data of the peak height at the center and the valley height at the edge of the molten pool under a specific stirring power. This data was then fitted to a paraboloid of revolution, and the actual surface area was calculated, divided by the area of ​​a static physical circle. The dimensionless magnification factor was then obtained. Macroscopic density of molten alloy Basic liquid film mass transfer coefficient carbon-oxygen reaction equilibrium constant Molar mass of carbon and oxygen and These parameters can be found in relevant thermodynamic databases or empirical handbooks. Electromagnetic stirring intensity correction factor. The Wagner activity coefficients of carbon and oxygen in multi-component alloy liquids are determined based on the actual operating parameters of the electromagnetic stirring equipment and the pre-calibration results. and It can be estimated using thermodynamic software based on the alloy composition. Preset refining pressure. The vacuum gauge provides real-time feedback. By substituting all the above parameters into the formula for calculating the precise deoxidation and refining time, the required precise deoxidation and refining time under the current conditions can be calculated in real-time or periodically. For example, if the calculation yields If the time limit is 1200 seconds, the system will continue refining for 1200 seconds before ending the refining process.

[0066] Through the aforementioned technical solution, in the refining stage of the vacuum smelting process for nanocrystalline master alloys, precise prediction and control of deoxidation refining time can be achieved based on a comprehensive consideration of physical mass transfer kinetics and multi-component thermodynamic equilibrium partial pressures. This significantly improves the efficiency and stability of the deoxidation process, ensuring that the oxygen content in the alloy melt accurately reaches the preset target, thereby effectively avoiding over-refining or under-refining problems caused by improper refining time. Ultimately, this helps to obtain high-quality nanocrystalline master alloys with lower and more uniform oxygen content, thereby improving the overall performance and batch stability of the material.

[0067] Preferably, the logic for calculating the overall thermal efficiency of the induction furnace is configured as follows: The overall thermal efficiency is the percentage of effective power in the total active power output of the induction power supply during the calibration test, after deducting the system water cooling power and the power lost by spatial thermal radiation. The system's water-cooled heat dissipation power is derived from the volumetric flow rate, density, specific heat capacity at constant pressure, and temperature difference between the inlet and outlet water of the induction coil cooling water. The spatial heat radiation loss power is derived from the Stefan-Boltzmann constant, the system's comprehensive thermal radiation emissivity, effective surface area, and the fourth power difference between the absolute temperature of the material inside the furnace and the absolute temperature of the surrounding environment under calibration conditions. Specifically, the overall thermal efficiency of the induction furnace is obtained through equipment thermal balance calibration, and its calculation formula is as follows: ; in, This indicates the overall thermal efficiency of the induction furnace. This represents the total active power output of the induced power supply during the calibration test (unit: ), This indicates the specific heat capacity of cooling water at constant pressure (unit: ). ), The density of cooling water (unit: ) ), The volumetric flow rate of the cooling water for the induction coil (unit: ), This indicates the absolute temperature of the return water to the induction coil (unit: ). ), This indicates the absolute temperature of the inlet water for cooling the induction coil (unit: ). ), Indicates the overall thermal emissivity of the system. This represents the Stefan-Boltzmann constant (unit: ). ), Represents effective surface area (unit: ), This indicates the absolute temperature of the material inside the furnace under calibrated conditions (unit: ). ), The absolute temperature of the surrounding environment (unit: ) ), Indicates the system's water cooling power. This represents the power lost through thermal radiation in space.

[0068] The overall thermal efficiency of an induction furnace is a measure of its ability to convert input electrical energy into effective thermal energy for the materials inside the furnace. It reflects energy losses during transmission, including heat carried away by cooling water, furnace body heat dissipation, and radiative loss. Equipment thermal balance calibration is a method to determine the overall thermal efficiency of an induction furnace by measuring its energy input and various energy losses under stable operating conditions. This typically involves monitoring parameters such as the inlet and outlet temperatures and flow rates of the cooling water, as well as the furnace surface temperature and ambient temperature. This calibration process can be performed during equipment installation and commissioning, or during regular maintenance, to ensure the accuracy of the efficiency parameters. The calculation formula... This indicates the total active power output of the induction power supply during the calibration test. This is the energy input of the induction furnace and can be directly measured using the power supply's power meter. , , , , These parameters are used to calculate the system's water cooling power, and they can be monitored in real time by flow meters and temperature sensors or measured during calibration. , , , , These parameters are used to calculate the power loss due to thermal radiation in space, and they can be obtained through infrared thermometry, surface area estimation, and material property lookup tables.

[0069] The proposed solution accurately obtains the overall thermal efficiency of the induction furnace by introducing a thermal balance calibration method. During the smelting process, the energy input of the induction furnace mainly comes from the total active power output of the induction power supply. However, not all the input energy is effectively transferred to the material inside the furnace; some energy is lost through the cooling system, and another portion is radiated into the environment through the furnace surface. To accurately quantify these energy losses, this method measures the absolute temperatures of the inlet and outlet water of the induction coil cooling water. , and volumetric flow rate Combined with the constant pressure specific heat capacity of cooling water and density This allows for the precise calculation of the system's water-cooling power. Simultaneously, the absolute temperature of the materials inside the furnace is measured. The absolute temperature of the surrounding environment In conjunction with the system's overall thermal emissivity Stefan-Boltzmann constant and effective surface area The power loss due to thermal radiation in the space is calculated. Subtracting these two main power losses from the total input power yields the effective power actually received by the material inside the furnace, from which the overall thermal efficiency of the induction furnace can be calculated. This precise efficiency calculation method ensures that, in the above S30, the initial power distribution... The calculations can more accurately reflect actual heating needs, avoiding overestimation or underestimation of power due to inaccurate efficiency estimations. Similarly, in S40 above, the power distribution is corrected. The calculations are therefore more reliable, ensuring that the temperature can be precisely maintained within the preset refining temperature range during the liquid alloying stage. In this way, the solution overcomes the difficulty of accurately controlling thermal efficiency in traditional smelting processes, providing a solid foundation for precise control of the entire smelting process.

[0070] The following is a specific example to illustrate this. As a concrete implementation method, the overall thermal efficiency of an induction furnace can be calibrated for equipment thermal balance through the following steps: First, when the induction furnace is unloaded or loaded with specific calibration materials and reaches a stable operating state, the total active power output of the induction power supply is measured using a high-precision power meter. Meanwhile, high-precision temperature sensors and flow meters installed on the inlet and outlet pipes of the induction coil cooling water system monitor the absolute temperature of the cooling water inlet in real time. absolute temperature of return water and volumetric flow rate In addition, an infrared thermometer was used to measure the absolute surface temperature of the materials inside the furnace. And use an ambient temperature sensor to obtain the absolute temperature of the surrounding environment. Effective surface area of ​​the induction furnace The overall thermal emissivity of the system can be estimated based on the furnace body structure dimensions. The overall thermal emissivity of the system can be determined by consulting tables or through experiments based on the properties of the furnace lining material. The method for obtaining the data is as follows: experimental calibration is performed using the steady-state blackbody radiation inversion method. The specific operation is as follows: the crucible is heated to the set refining working temperature and kept in thermal equilibrium steady state, and the net electrical power input required to maintain the constant temperature of the system is recorded. The absolute temperature of the outer wall of the crucible was measured using a high-precision infrared thermometer. And simultaneously obtain the absolute temperature of the surrounding environment. The overall thermal emissivity of the system is calculated by inversely solving the Stefan-Boltzmann radiation law. The solution equation is: The specific heat capacity of cooling water at constant pressure and density The Stefan-Boltzmann constant can be obtained by looking up a table based on the physical properties of water at the corresponding temperature. These are known physical constants. By substituting all measured and determined parameters into the above calculation formula, the overall thermal efficiency of the induction furnace under the current operating conditions can be obtained. The calibration process can be repeated multiple times, with the average value taken to improve accuracy, or calibration can be performed under different operating conditions to establish an efficiency database for dynamic correction during actual smelting.

[0071] Through the above technical solution, the overall thermal efficiency of the induction furnace can be accurately obtained. This allows for more accurate calculation of the initial power distribution during the vacuum smelting of nanocrystalline master alloys, as well as the adjustment of the power distribution during the liquid alloying stage, based on more precise thermal efficiency parameters. Therefore, it effectively avoids temperature control deviations caused by inaccurate thermal efficiency estimations, ensuring that the material inside the furnace is precisely heated according to the preset temperature rise rate and stably maintained within the preset refining temperature range during the liquid alloying stage. This not only improves the stability and controllability of the smelting process but also helps optimize energy utilization efficiency, ultimately resulting in nanocrystalline master alloy products with superior quality and more stable performance.

[0072] The nanocrystalline master alloy mainly contains Fe, Si, B, Nb and Cu elements, and the added elements in S40 include Si and B.

[0073] The preset initial vacuum threshold and the preset refining pressure both range from 0.1 to 0.5. The preset refining temperature range is 1500-1540°C. .

[0074] A vacuum smelting apparatus for nanocrystalline master alloys, employing the aforementioned vacuum smelting process for nanocrystalline master alloys, includes a vacuum induction furnace, a copper roller with a cooling system (which can be cooled by circulating water) installed inside the vacuum induction furnace, and a crucible installed inside the induction furnace.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A vacuum smelting process for nanocrystalline master alloys, characterized in that, include: S10. Based on the differential balance between transient venting dynamics and the actual pumping capacity of the system, calculate the maximum allowable temperature rise rate that limits the vacuum level. S20. Combining the thermodynamic deformation characteristics, geometric constraints and stress safety boundary of the crucible, calculate the crucible thermal stress limit safe temperature rise rate and take the minimum value of the crucible and the vacuum limit maximum allowable temperature rise rate as the actual safe temperature rise rate. S30. Using the actual safe temperature rise rate as the input target, and combining the characteristics of the electromagnetic skin effect, the overall thermal efficiency of the equipment, the electromagnetic coupling efficiency, and the geometric characteristics of the material particles, the initial power distribution is obtained. S40. Entering the liquid alloying stage, the initial power distribution is controlled by negative feedback, taking into account the physicochemical properties of the added elements, the actual yield of the engineering process, and the thermodynamic characteristics of the alloying reaction, so as to maintain the temperature within the preset refining temperature range. S50. Maintain the temperature within the preset refining temperature range and keep the vacuum under the preset refining pressure. Combine the target and initial oxygen content mass fraction, physical and kinetic mass transfer characteristics and multi-component thermodynamic equilibrium partial pressure characteristics to calculate the precise deoxidation refining time. The refining ends when the time is up, and the nanocrystalline master alloy is obtained.

2. The vacuum smelting process for nanocrystalline master alloys according to claim 1, characterized in that, The parameter constraints for each control step are as follows: In S10, the transient venting kinetics are characterized by the physical forward factor and desorption activation energy of gas desorption from the material surface; the actual pumping capacity of the system is characterized by the actual effective pumping speed of the vacuum system and the maximum allowable vacuum deterioration rate threshold. In S20, the thermodynamic deformation characteristics of the crucible include thermal diffusivity, Poisson's ratio, Young's modulus, and coefficient of linear expansion; the geometric constraints and stress safety boundaries include the outer diameter, inner diameter, engineering geometric safety factor, and maximum allowable tensile thermal stress of the crucible. In S30, the electromagnetic skin effect characteristics include the operating frequency of the medium-frequency induction power supply, the vacuum permeability, the relative permeability of the material, and the physical conductivity; the overall thermal efficiency of the equipment is the overall thermal efficiency of the induction furnace; the electromagnetic coupling efficiency is the actual electromagnetic coupling coefficient of the induction coil; and the geometric characteristics of the material particles are the average equivalent diameter of the solid particles charged into the furnace. In S40, the physicochemical properties of the added elements include the mass fraction and molar mass of the added elements; the thermodynamic characteristics of the alloying reaction include the absolute value of the molar exothermic enthalpy and the reaction time window. In S50, the physical and kinetic mass transfer characteristics include the effective surface area of ​​the molten pool, the macroscopic density of the alloy liquid, the basic liquid film mass transfer coefficient, and the electromagnetic stirring intensity correction coefficient; the multi-component thermodynamic equilibrium partial pressure characteristics include the molar mass of carbon and oxygen, the initial carbon content mass fraction, the Wagner activity coefficient of carbon and oxygen in the multi-component alloy liquid, the preset refining pressure, and the carbon-oxygen reaction equilibrium constant.

3. The vacuum smelting process for nanocrystalline master alloys according to claim 2, characterized in that, In S10, the calculation logic for the maximum allowable temperature rise rate limited by vacuum degree is as follows: The maximum allowable temperature rise rate of the vacuum limit is positively correlated with the combined product of the maximum allowable vacuum deterioration rate threshold and the actual effective pumping speed of the vacuum system. It is also subject to the inverse modulation of the exponential thermal desorption attenuation factor, which is jointly mapped by the physical forward factor of gas desorption from the material surface, the desorption activation energy, the ideal gas constant, and the absolute temperature of the material in the furnace.

4. The vacuum smelting process for nanocrystalline master alloys according to claim 3, characterized in that, In step S20, the calculation logic for determining the actual safe temperature rise rate during the solid heating period includes: Based on the maximum allowable tensile thermal stress, thermal diffusivity and engineering geometric safety factor of the crucible material, a thermal shock resistance benchmark for the material is established. Based on the Poisson's ratio, Young's modulus, coefficient of linear expansion of the crucible material, and the outer and inner diameters of the crucible, a thermodynamic stress conversion factor is constructed. The safe temperature rise rate of the crucible under thermal stress is the limit output after the thermal shock tolerance benchmark of the material is inversely mapped by the thermodynamic stress conversion factor; The actual safe temperature rise rate is determined by minimizing the limit boundary value between the crucible thermal stress-limited safe temperature rise rate and the vacuum degree-limited maximum allowable temperature rise rate output by S10.

5. The vacuum smelting process for nanocrystalline master alloys according to claim 4, characterized in that, In step S30, the initial power distribution calculation logic is configured as follows: The combined product of the total mass of material charged into the furnace, the average isobaric specific heat capacity of the furnace charge in solid state, and the actual safe temperature rise rate is used as the benchmark sensible heat demand power. Based on the operating frequency of the medium-frequency induction power supply, vacuum permeability, relative permeability of the material, physical conductivity, and average equivalent diameter of the solid particles charged into the furnace, an electromagnetic skin penetration attenuation factor is constructed. The initial power distribution is the result of amplification and compensation of the baseline sensible heat demand power after considering the system energy transmission barrier established by the comprehensive thermal efficiency of the induction furnace, the actual electromagnetic coupling coefficient of the induction coil, and the electromagnetic skin penetration attenuation factor.

6. The vacuum smelting process for nanocrystalline master alloys according to claim 5, characterized in that, In step S40, the corrected power distribution is calculated using feedforward enthalpy compensation logic: Extract the total number of types of added elements, and for each added element, based on its mass fraction, engineering yield, molar mass and absolute value of molar mixed exothermic enthalpy, combined with the total mass of the material charged into the furnace, integrate and sum to obtain the total equivalent of alloying exothermic heat. The total exothermic equivalent of the alloying is converted into an equivalent heat compensation power by time-domain amortization based on the reaction time window and the comprehensive thermal efficiency of the induction furnace. The corrected power distribution is the result of subtracting the equivalent heat compensation power from the initial power distribution output by S30.

7. The vacuum smelting process for nanocrystalline master alloys according to claim 2, characterized in that, In S50, the precise deoxidation and refining time is calculated based on the steady-state carbon-oxygen dynamic loss driving force logic solution: The precise deoxygenation refining time is directly proportional to the total mass of the material and the macroscopic deoxygenation flux, which is jointly determined by the difference between the initial oxygen content mass fraction and the set target residual oxygen content mass fraction. The precise deoxygenation refining time is inversely constrained by the comprehensive deoxygenation mass transfer rate; the comprehensive deoxygenation mass transfer rate includes the physical fluid dynamics mass transfer factor and the effective deoxygenation mass transfer driving force. The physical fluid dynamics mass transfer factor is determined by the combined factors of the effective surface area of ​​the molten pool, the macroscopic density of the alloy liquid, the basic liquid film mass transfer coefficient, and the electromagnetic stirring intensity correction coefficient. The effective deoxidation mass transfer driving force is the difference between the average actual oxygen mass fraction of the alloy liquid during the refining process and the equilibrium oxygen mass fraction under the preset refining conditions. The equilibrium oxygen mass fraction is calculated based on the preset refining pressure, carbon-oxygen reaction equilibrium constant, Wagner activity coefficients of carbon and oxygen elements in the multi-component alloy liquid, and average effective carbon mass fraction, according to the thermodynamic equilibrium relationship of the carbon-oxygen reaction.

8. The vacuum smelting process for nanocrystalline master alloys according to claim 6, characterized in that, The logic configuration for calculating the overall thermal efficiency of the induction furnace is as follows: The overall thermal efficiency is the percentage of effective power in the total active power output of the induction power supply during the calibration test, after deducting the system water cooling power and the power lost by spatial thermal radiation. The system's water-cooled heat dissipation power is derived from the volumetric flow rate, density, specific heat capacity at constant pressure, and temperature difference between the inlet and outlet water of the induction coil cooling water. The spatial heat radiation loss power is derived from the Stefan-Boltzmann constant, the system's comprehensive thermal radiation emissivity, effective surface area, and the fourth power difference between the absolute temperature of the material inside the furnace and the absolute temperature of the surrounding environment under calibration conditions.

9. The vacuum smelting process for nanocrystalline master alloys according to claim 1, characterized in that, The nanocrystalline master alloy contains Fe, Si, B, Nb, and Cu elements, and the added elements in S40 include Si and B. The preset initial vacuum threshold and the preset refining pressure both range from 0.1 to 0.

5. The preset refining temperature range is 1500-1540°C. .

10. A vacuum smelting apparatus for nanocrystalline master alloys, employing the vacuum smelting process for nanocrystalline master alloys as described in any one of claims 1-9, comprising a vacuum induction furnace, a copper roller with a cooling system installed inside the vacuum induction furnace, and a crucible installed inside the induction furnace.

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