Multi-parameter real-time monitoring and purification regulation and control method in titanium alloy remelting process

Abstract

The invention discloses a multi-parameter real-time monitoring and purification regulation and control method in a titanium alloy remelting process, and belongs to the field of metal impurity removal and smelting. The problems that in the prior art, parameter monitoring lags behind (off-line detection), regulation and control are single (only power is regulated), and the rejection rate of cast ingots is high due to slow response are solved. The method comprises the steps that the titanium alloy excess materials are smelted through a plasma arc cold bed smelting furnace, in the smelting process, smelting parameters are collected, a coupling model is established based on MATLAB / Simulink, linkage analysis is conducted on data, and then closed-loop regulation and control are conducted. According to the method, the real-time performance of the technological process is remarkably improved, and the problem of response lag existing in a traditional off-line detection mode is effectively solved by shortening the parameter acquisition interval and regulating and controlling the response time. And in the aspects of purity and qualified rate, the impurities are efficiently removed. The automation degree of the system is improved, manual intervention is reduced, the labor cost is reduced, and the rejection rate is greatly reduced to be within 2% from 15%. In addition, the system has good material adaptability, and diversified smelting scene requirements are met.

Description

Technical Field

[0001] This invention belongs to the field of metal impurity removal and smelting, specifically, it relates to a method for real-time monitoring and purification control of multiple parameters during the remelting process of titanium alloys. Background Technology

[0002] In the hydrogen-containing plasma arc cold hearth remelting process of titanium alloys, real-time monitoring of parameters such as melt temperature, plasma arc morphology, furnace gas composition, and vacuum level is fundamental to ensuring ingot quality. However, current traditional monitoring methods suffer from significant lag, mostly relying on offline detection of ingot composition (such as measuring oxygen content after melting) to judge the purification effect, failing to capture process fluctuations in real time. This lag makes it difficult to detect problems such as sudden drops in melt temperature and abnormal gas composition during production, leading to incomplete impurity removal. According to industry statistics, the scrap rate of titanium alloy remelting under traditional processes exceeds 15%. Meanwhile, titanium alloy smelting costs are high; related calculations show that its cost is five times that of stainless steel. The high scrap rate further exacerbates the economic burden on enterprises, contradicting the cost control requirements for industrial-grade titanium alloy ingots (single ingot weight ≥15kg).

[0003] The current control methods are too simplistic to address the complex physicochemical changes during titanium alloy remelting. Current technologies primarily rely on manual adjustment of plasma gun power, neglecting key parameters such as gas composition and pressure. For example, when the water vapor concentration in the furnace increases, the hydrogen ratio cannot be increased promptly, leading to a decrease in oxygen impurity removal efficiency. However, experiments with non-consumable arc melting in a hydrogen-argon mixed atmosphere show that a hydrogen ratio of 5%-30% significantly reduces the oxygen content of Ti-6A-l4V alloy, further highlighting the importance of multi-parameter synergistic control. Furthermore, manual control response times exceed 5 minutes, while melt flow and reaction rates are rapid (e.g., impurity volatilization rates vary with temperature by up to 0.1 ppm / s). This mismatch in response speed easily leads to localized compositional inhomogeneities, making it difficult to ensure the overall quality stability of the ingot and failing to meet the high precision and consistency requirements of the aerospace industry for titanium alloy materials.

[0004] From an industrialization perspective, existing monitoring and control technologies severely restrict the large-scale application of titanium alloy remelting processes. With the increasing demand for titanium alloys in aerospace, marine engineering, and other fields, higher requirements are being placed on the output and quality of industrial-grade titanium alloy ingots. However, traditional manual control methods are not only inefficient but also susceptible to human error, making stable batch production difficult. Related data shows that intelligent control can achieve a response time as low as 0.8 seconds, while manual control has an average response time of approximately 45 seconds. This comparison reflects the inherent disadvantage of manual control in response speed. During the titanium alloy remelting process, the lag and limitations of manual control lead to significant fluctuations in ingot quality, making it difficult to consistently meet the requirements of industrial-grade titanium alloy ingots, severely hindering the industrial upgrading of titanium alloy remelting processes. Therefore, developing a method for real-time acquisition of multiple parameters, linked analysis, and closed-loop control is crucial for solving the quality fluctuations in titanium alloy remelting, reducing scrap rates, and promoting industrialization. Summary of the Invention To address the problems of high ingot scrap rates caused by lagging parameter monitoring (offline detection), single control (only power adjustment), and slow response in existing technologies, this invention provides a multi-parameter real-time monitoring and purification control method that achieves oxygen ≤700ppm and nitrogen ≤100ppm in titanium alloys through closed-loop control.

[0005] To address the aforementioned technical problems, the present invention adopts the following technical solution: The purpose of this invention is to provide a method for real-time monitoring and purification control of multiple parameters during the remelting process of titanium alloys, comprising the following steps: The titanium alloy scrap was smelted in a plasma arc cold hearth furnace. During the smelting process, smelting parameters were collected, a coupled model was established based on MATLAB / Simulink, the data was analyzed in a linkage manner, and then closed-loop control was performed.

[0006] Regeneration involves filtering the hydrogen-argon mixture to remove molten splash powder, then condensing water vapor and cooling it to below 50°C. Subsequently, it is vacuum activated by molecular sieves to remove carbides, pressurized, and stored in a high-pressure storage tank for recycling.

[0007] Based on the above method, this invention provides precise control over TC4 conventional impurities, TA15 high-nitrogen impurities, and high-oxygen titanium alloy residues, respectively. The specific technical solutions are as follows: First aspect: Real-time monitoring and purification control methods for multiple parameters during the remelting of conventional impurities in TC4 titanium alloy. This direction is applicable to conventional TC4 blocky scrap (5-10mm). The specific steps are as follows: During the multi-parameter acquisition phase, two infrared thermometers (FLIR A655sc, resolution ±5℃, sampling frequency 1Hz) are placed above the cooling bed to monitor the center T1 and edge T2 of the molten pool (controlling T1-T2≤50℃); a residual gas analyzer (Pfeiffer QMG 220) detects the concentrations of H2O and N2 (sampling interval 10s); pressure sensors monitor the vacuum chamber P1 (0.0067-100Pa) and the circulation system P2 (0.05-0.1MPa); and a PLC collects the plasma gun power (50-200kW) and hydrogen / argon flow rate (0-100L / min) in real time.

[0008] In the data linkage analysis phase, a coupled model was established based on MATLAB / Simulink: when T1 < 1600℃ (TC4 melting point + 200℃), the overheating was deemed insufficient; when H2O > 500ppm, the oxygen impurities were deemed active; when N2 > 80ppm, the nitrogen was deemed excessive; when P2 < 0.05MPa, the circulating pressure was deemed insufficient.

[0009] During the closed-loop control phase, the PLC automatically executes the following: when T1 < 1600℃, the plasma gun power is increased (step size 5kW, response < 1s); when H2O > 500ppm, the hydrogen ratio is increased (step size 5vol%, response < 0.5s, Vol% refers to the partial pressure of gas volume in the furnace); when P2 < 0.05MPa, the compressor is triggered to increase pressure; in the later stage of melting, the crystallizer pulling speed is reduced from 1.0mm / s to 0.8mm / s (step size 0.1mm / s) to ensure uniform solidification.

[0010] The second aspect: Real-time monitoring and purification control methods for multiple parameters during the remelting of high-nitrogen impurities in TA15 titanium alloy. This approach addresses the issue of high nitrogen content in TA15 residue, and the specific steps are as follows: During the multi-parameter acquisition phase, the focus is on strengthening nitrogen concentration monitoring (sampling interval 5s), and adding one pressure sensor to monitor the dynamic pressure of the vacuum chamber (P1N2 > fluctuation ≤ ±0.5Pa); temperature monitoring focuses on the edge of the molten pool (T2 ≥ 1580℃, to avoid nitrogen residue).

[0011] During the data linkage analysis phase, the coupling model threshold is adjusted as follows: when N2 > 90ppm, the vacuum level is increased (P1 is reduced by 10%); when T2 < 1580℃, the plasma gun edge power is increased (+10kW).

[0012] During the closed-loop control phase, at 90 ppm, the PLC controls the vacuum system to reduce P1 (from 0.01 Pa to 0.009 Pa, response < 2 s); simultaneously, the hydrogen ratio is increased (from 20 vol% to 25 vol%) to promote the reaction of nitrogen and hydrogen to generate NH3; in the later stage of smelting, the holding time is extended by 10 min to ensure that nitrogen is fully removed.

[0013] Third aspect: Real-time monitoring and purification control methods for multiple parameters during the remelting of high-oxygen titanium alloy scrap. This approach is applicable to high-oxygen waste titanium materials, and the specific steps are as follows: During the multi-parameter acquisition phase, the accuracy of hydrogen flow monitoring was improved to ±0.1L / min, and the residual gas analyzer focused on capturing H2O concentration (resolution 1ppm); temperature control T1=1650-1700℃ (high temperature promotes oxygen-hydrogen reaction).

[0014] During the data linkage analysis phase, the coupling model was set as follows: when H2O > 800ppm, the hydrogen ratio + 5vol% (upper limit 50vol%); when T1 < 1650℃, the power + 15kW.

[0015] The present invention has the following beneficial effects: This invention significantly improves the real-time performance of the process by shortening the parameter acquisition interval and control response time, effectively solving the response lag problem of traditional offline detection methods. Regarding purity and yield, it achieves efficient impurity removal, controlling the oxygen content of the ingot below 620 ppm and the nitrogen content to no more than 95 ppm. Simultaneously, the system's automation level is improved, reducing manual intervention, lowering labor costs, and significantly reducing the scrap rate from 15% to less than 2%. Furthermore, the system has good material adaptability, compatible with various titanium alloys such as TC4 and TA15, as well as high-impurity scrap, meeting the needs of diverse smelting scenarios. Detailed Implementation

[0016] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0017] Raw materials: TC4 titanium alloy scrap (Liaoning Ansteel, initial oxygen 1200ppm, nitrogen 180ppm, carbon 350ppm); TA15 titanium alloy scrap (initial oxygen 1100ppm, nitrogen 160ppm); high-impurity titanium alloy scrap (initial oxygen 1500ppm, nitrogen 200ppm), all crushed to 5-10mm; Monitoring equipment: Infrared thermometer (FLIR A655sc), residual gas analyzer (Pfeiffer QMG 220), pressure sensor (ABB 266HSH), PLC (Siemens S7-1500); Testing equipment: Oxygen, nitrogen and hydrogen analyzer (LECO ONH836), electronic universal testing machine (MTS C64.104), metallurgical microscope (ZEISS Axio Observer).

[0018] Example 1: Regulation of Common Impurities in TC4 (1) Raw material preparation: 20kg TC4 residue (oxygen 1200ppm, nitrogen 180ppm); (2) Monitoring deployment: Infrared thermometers measure T1 and T2, residual gas analyzers measure H2O / N2, and pressure sensors measure P1=0.01Pa and P2=0.08MPa; (3) Regulation process: 0-10min: T1=1620℃, H2O=300ppm, N2=60ppm, parameters are normal; 15min: T1 drops to 1580℃, PLC increases power to 130kW, 10s later T1=1630℃; 25 min: H2O = 600 ppm, PLC increases H2 ratio to 15 vol%, H2O = 450 ppm after 5 s; (4) Results: The oxygen content of the ingot was 260 ppm and the nitrogen content was 82 ppm. The pass rate was 100% and the tensile strength was 950 MPa.

[0019] Example 2: Regulation of high nitrogen impurities in TA15 (1) Raw material preparation: 20kg TA15 residue (nitrogen 160ppm); (2) Monitoring deployment: N2 sampling interval 5s, P1 monitoring accuracy ±0.5Pa; (3) Regulation process: 12 min: N2 = 90 ppm, PLC reduces P1 to 0.009 Pa, after 20 s N2 = 75 ppm; 30min: T1=1780℃, PLC power reduced to 140kW, T1 stabilized at 1720℃; (4) Results: The oxygen content of the ingot was 310 ppm and the nitrogen content was 88 ppm. The pass rate was 100% and the yield strength was 880 MPa.

[0020] Example 3: Control of high-oxygen titanium alloy scrap (1) Raw material preparation: 20kg high oxygen residue (oxygen 1500ppm); (2) Monitoring deployment: H2 flow accuracy ±0.1L / min, H2O resolution 1ppm; (3) Regulation process: 5 min: H2O=800ppm, PLC increases H2 ratio to 35vol%, H2O=600ppm; 20min: T1=1630℃, PLC power increased to 195kW, T1=1660℃; (4) Results: Oxygen 620ppm and nitrogen 95ppm in the ingot.

[0021] Comparative Example 1: Traditional manual control (without real-time monitoring) (1) Raw material preparation 20kg of TC4 residue (oxygen 1200ppm, nitrogen 180ppm), 5-10mm lumps, dried at 80℃ for 2h (consistent with Example 1).

[0022] (2) Controlling the process Using the same type of hydrogen-containing plasma arc cooling hearth furnace, without real-time monitoring equipment: Initial parameters: H2:Ar=10:90, power 120kW, furnace pressure 0.08MPa; Control: Stop the machine every 30 minutes to take samples for testing. If oxygen > 700 ppm, manually increase power (+10 kW / time). If nitrogen > 100 ppm, manually decrease furnace pressure (-0.01 MPa / time). There is no dynamic adjustment of gas / pressure; the pulling speed is adjusted to 0.8mm / s based on experience later.

[0023] (3) Result detection Impurities: Oxygen 950ppm, Nitrogen 150ppm (exceeding industrial standards); Efficiency: Total melting time: 90 min (60 min in Example 1); Pass rate: 65% (3 shrinkage cavities, 0.2% TiC inclusions); Mechanical properties: tensile strength 820 MPa, elongation 12.1% (13.7% lower than Example 1).

[0024] Comparative Example 2: Single-parameter control (temperature adjustment only) (1) Raw material preparation 20kg TA15 residue (oxygen 1100ppm, nitrogen 160ppm), 3-8mm particles (consistent with Example 2).

[0025] (2) Controlling the process Only equipped with an infrared thermometer; temperature adjustment is required. Monitoring: Control only the center of the molten pool T1 (1600-1700℃). If T1 < 1600℃, increase the power (+10kW, response > 30s). Fixed parameters: H2:Ar=20:80 (volume ratio), furnace pressure 0.06MPa, pull-out 1.2mm / s, which remain unchanged throughout the process.

[0026] (3) Result detection Impurities: Oxygen 820ppm, Nitrogen 120ppm (exceeding the standard); Quality: Axial oxygen difference 180ppm (edge ​​910ppm / center 730ppm); Pass rate: 70%, tensile strength 850MPa (3.4% lower than Example 2).

[0027] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A method for real-time monitoring and purification control of multiple parameters during the remelting process of titanium alloys, characterized in that, Includes the following steps: The titanium alloy scrap was smelted in a plasma arc cold hearth furnace. During the smelting process, smelting parameters were collected, a coupled model was established based on MATLAB / Simulink, the data was analyzed in a linkage manner, and then closed-loop control was performed.

2. A method for real-time monitoring and purification control of multiple parameters during the remelting process of TC4 titanium alloy, characterized in that, Includes the following steps: The TC4 titanium alloy scrap was placed in a plasma arc cold hearth melting furnace and melted under a hydrogen-argon mixed gas. During the melting parameter acquisition stage, the center temperature T1 and the edge temperature T2 of the molten pool were monitored and controlled to be T1-T2≤50℃; the concentrations of H2O and N2 were detected; the vacuum chamber pressure P1 and the circulating pressure P2 were monitored; and the PLC collected the plasma gun power and the flow rate of the hydrogen-argon mixed gas in real time. In the data linkage analysis phase, a coupled model was established based on MATLAB / Simulink: when T1 < 1600℃, it was determined that the overheating was insufficient; when H2O > 500ppm, it was determined that oxygen impurities were active; when N2 > 80ppm, it was determined that nitrogen exceeded the standard. When P2 < 0.05 MPa, the circulating pressure is determined to be insufficient; During the closed-loop control phase, the PLC automatically executes the following: when T1 < 1600℃, the plasma gun power is increased; when H2O > 500ppm, the hydrogen ratio is increased; when P2 < 0.05MPa, the compressor is triggered to increase pressure; in the later stage of melting, the crystallizer pulling speed is controlled to decrease from 1.0mm / s to 0.8mm / s to ensure uniform solidification.

3. The method according to claim 2, characterized in that, The particle size of TC4 titanium alloy scrap is 5mm-10mm.

4. The method according to claim 2, characterized in that, Regeneration involves filtering the hydrogen-argon mixture to remove molten splash powder, then condensing water vapor and cooling it to below 50°C. Subsequently, it is vacuum activated by molecular sieves to remove carbides, pressurized, and stored in a high-pressure storage tank for recycling.

5. A method for real-time monitoring and purification control of multiple parameters during the remelting process of TA15 titanium alloy, characterized in that, Includes the following steps: The TA15 titanium alloy scrap was placed in a plasma arc cold hearth melting furnace and melted under a hydrogen-argon mixture. During the melting parameter acquisition stage, the nitrogen concentration, the dynamic pressure P1 of the vacuum chamber, and the edge temperature T2 of the focused molten pool were monitored. During the data linkage analysis phase, the coupling model threshold is adjusted as follows: when N2 > 90ppm, the vacuum level is increased; when T2 < 1580℃, the edge power of the plasma gun is increased. During the closed-loop control phase, when N2 > 90 ppm, the PLC controls the vacuum system to reduce P1; simultaneously, the hydrogen ratio is increased; in the later stage of smelting, the holding time is extended.

6. The method according to claim 5, characterized in that, The nitrogen concentration sampling interval is 5 seconds.

7. The method according to claim 5, characterized in that, T2≥1580℃。 8. A method for real-time monitoring and purification control of multiple parameters during the remelting process of high-oxygen alloys, characterized in that, Includes the following steps: High-oxygen waste titanium material was placed in a plasma arc cold hearth melting furnace and melted under a hydrogen-argon mixed gas. During the smelting parameter acquisition stage, the accuracy of hydrogen flow monitoring was improved to ±0.1L / min, and the residual gas analyzer focused on capturing H2O concentration and monitoring the center temperature T1 of the molten pool.

9. During the data linkage analysis phase, the coupling model is set as follows: when H2O > 800ppm, the hydrogen ratio increases by 5% with an upper limit of 50%; when T1 < 1650℃, the power is increased by 15kW.

10. In the closed-loop control stage, the initial hydrogen ratio is set to 30%, which is increased to 35% when H2O > 800ppm; when T1 < 1650℃, the plasma gun power is increased from 180kW to 195kW; the gas circulation system increases the molecular sieve regeneration frequency.

11. The method according to claim 8, characterized in that, T1 is controlled at 1650-1700℃.

12. The method according to claim 8, characterized in that, The gas circulation system increases the molecular sieve regeneration frequency to once every 20 minutes.