A vacuum consumable melting method

Abstract

The application provides a vacuum consumable melting method and relates to the technical field of melting. In the feeding stage, an infrared thermal imager installed on the observation window of a vacuum consumable arc furnace is used to acquire a temperature field distribution matrix of the molten pool surface in real time. A circular region is demarcated in the temperature field matrix, and the circular region is divided into a central region and an edge region. The cooling slope Ke of the central region and the cooling slope Kc of the edge region are extracted respectively. The solidification state is judged in real time according to the central / edge cooling slope ratio R=Ke / Kc. When R exceeds the preset threshold range, the arc stabilizing magnetic field is adjusted to realize forced directional solidification, the shrinkage holes are concentrated and compressed to the top end of the ingot, and the shrinkage hole depth is effectively compressed. In addition, the feeding is automatically determined to end at the liquidus temperature, the invalid long-time small-current operation is avoided, the feeding time is shortened, and the grain coarsening caused by excessive feeding is avoided. Therefore, the application can effectively inhibit the internal shrinkage hole defects of the ingot, reduce the amount of riser cutting, and improve the quality of the head of the alloy ingot.

Description

Technical Field

[0001] This invention relates to the field of smelting technology, and in particular to a vacuum consumable melting method. Background Technology

[0002] Vacuum arc remelting (VAR) is an important production process for active metals such as titanium, nickel, and zirconium, as well as their alloys. During the final feeding stage of melting, the molten pool solidification needs to be controlled by gradually reducing the melting current, so that the shrinkage pores are concentrated in a very small area at the top of the ingot, thereby reducing cutting losses. Existing technologies mainly employ a stepped current reduction method based on preset time points. This method has fixed parameters and cannot respond to random factors such as irregular electrode end shapes and cooling water temperature fluctuations, leading to significant differences in shrinkage cavity depth between different furnace runs. If the feeding time is too short, shrinkage pores are severe; if the feeding time is too long, grains are coarse and energy consumption increases, both of which impair the final quality of the ingot and material utilization.

[0003] To address the aforementioned issues, a control method is needed that can sense the solidification state of the molten pool in real time and dynamically adjust the feeding parameters accordingly, so as to achieve precise intervention in the shrinkage cavity formation process and accurate judgment of the feeding endpoint. Summary of the Invention

[0004] The summary section of this invention provides a brief overview of the concepts, which will be described in detail in the detailed description section that follows. This summary section is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.

[0005] Some embodiments of the present invention provide a vacuum self-consumable melting method to solve the technical problems mentioned in the background section above.

[0006] The vacuum arc remelting method provided by this invention performs the following steps during the feeding stage of vacuum arc remelting: Step S1: Obtain a temperature field matrix using an infrared thermal imager. The temperature field matrix is ​​a temperature field matrix facing the crystallizer. Delineate a circular region in the temperature field matrix, which coincides with the circular region of the molten pool. Divide the circular region into a central region and an edge region, and extract the cooling slope Ke of the central region and the cooling slope Kc of the edge region, respectively. In step S2, the solidification state is determined in real time based on the ratio of the cooling slope of the center to the edge, R=Ke / Kc. When R exceeds the preset threshold range, the arc stabilizing magnetic field is adjusted to force the molten pool to solidify in a directional manner. In step S3, when the temperature of the entire circular region is lower than the liquidus temperature of the molten alloy and the hot spot disappears, the feeding is completed and the power is automatically cut off.

[0007] Optionally, in step S2, the preset threshold range is 1.2≤R≤1.5; when R<1.2, the arc is made to converge toward the central region by adjusting the arc stabilizing current; when R>1.5, the arc is made to diffuse toward the edge region by adjusting the arc stabilizing current.

[0008] Optionally, in step S2, by adjusting the current ratio of the upper and lower sets of arc-stabilizing coils, the intersection point of the vertical component Bz and the radial component Br of the magnetic induction intensity is changed, so that the electric arc converges towards the central region or spreads towards the edge region.

[0009] Optionally, in step S2, the magnetic field scanning waveform of the arc stabilizing coil is adjusted from a triangular wave to a square wave.

[0010] Optionally, after step S1, the cooling slope Ke of the central region is compared with the target cooling slope K pre-stored in the process database. target Compare the results; based on Ke and K target The deviation is dynamically adjusted by adjusting the current reduction ΔI to make the cooling slope Ke in the central region approach the target cooling slope K. target .

[0011] Optionally, when |Ke|>|K target |Decrease ΔI when |Ke|<|K target |Increases ΔI.

[0012] Optionally, the formula for calculating the current drop is: when |Ke|>|K target |When, ΔI=ΔI base ×(1-α); when |Ke|<|K target |When, ΔI=ΔI base ×(1+α); where α is an adjustment coefficient positively correlated with the deviation amplitude, and the range of α is 0.35-0.4, ΔI base It is the reduction in reference current, ΔI base The range is 500-1000A.

[0013] Optionally, in step S3, the condition for determining the disappearance of the hot spot is: the temperature of all pixels in the circular area is lower than the liquidus temperature of the molten alloy, and no local hot spots with a temperature higher than the background temperature by more than 20°C appear in 5 consecutive frames of images.

[0014] Optionally, in step S1, the center of the central region coincides with the center of the circular region, and the radius is 1 / 4R to 1 / 3R; the edge region is the remaining annular region after the central region is subtracted from the circular region, where R is the radius of the circular region.

[0015] Optionally, in step S1, the sampling frequency of the infrared thermal imager is 15Hz to 30Hz, and the interference generated by the copper reflection from the inner wall of the crystallizer is filtered out by a dynamic mask algorithm.

[0016] The above embodiments of the present invention have the following beneficial effects: During the feeding stage, an infrared thermal imager installed in the observation window of the vacuum consumable arc furnace acquires the surface temperature field distribution matrix of the molten pool in real time. A circular region is defined in the temperature field matrix, and a central region and an edge region are divided within the circular region. The cooling slope Ke of the central region and the cooling slope Kc of the edge region are extracted respectively. The solidification state is judged in real time according to the ratio of the central / edge cooling slope R=Ke / Kc. When R exceeds the preset threshold range, the arc-stabilizing magnetic field adjustment is triggered to achieve forced directional solidification, concentrating and compressing the shrinkage cavity to the top of the ingot, effectively compressing the shrinkage cavity depth. In addition, the end of feeding is automatically determined by the liquidus temperature, avoiding ineffective long-term low-current operation, shortening the feeding time, and avoiding grain coarsening caused by excessive feeding. Therefore, this application can effectively suppress shrinkage cavity defects inside the ingot, reduce the amount of riser removal, and improve the quality of the alloy ingot head. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the shrinkage process control in an embodiment of this application. Figure 2 This is a schematic diagram of the central area and edge area in an embodiment of this application.

[0019] 1. Central region; 2. Peripheral region; 3. Crystallizer; Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Figure 1 This is a flowchart illustrating the shrinkage process control in an embodiment of this application. Figure 2 This is a schematic diagram of the central and edge regions of an embodiment of this application. The present disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] The vacuum arc remelting method provided in this application performs the following steps during the feeding stage of vacuum arc remelting: In step S1, a temperature field matrix is ​​acquired using an infrared thermal imager. The temperature field matrix is ​​the temperature field matrix facing the crystallizer. A circular region is delineated in the temperature field matrix, which coincides with the circular region of the molten pool. Within the circular region, a central region and an edge region are divided, and the cooling slope Ke of the central region and the cooling slope Kc of the edge region are extracted respectively. In step S2, the solidification state is determined in real time based on the ratio of the cooling slope of the center to the edge, R=Ke / Kc. When R exceeds the preset threshold range, the arc stabilizing magnetic field is adjusted to force the molten pool to solidify in a directional manner. In step S3, when the temperature of the entire circular area is lower than the liquidus temperature of the molten alloy and the hot spot disappears, the feeding is completed and the power is automatically cut off.

[0025] During the feeding stage, an infrared thermal imager installed in the observation window of the vacuum arc furnace acquires the temperature field distribution matrix of the molten pool surface in real time. A circular region is delineated within the temperature field matrix, and within this region, a central region and an edge region are divided. The cooling slope Ke of the central region and the cooling slope Kc of the edge region are extracted respectively. The solidification state is determined in real time based on the ratio of the central / edge cooling slope R = Ke / Kc. When R exceeds a preset threshold range, an arc-stabilizing magnetic field adjustment is triggered to achieve forced directional solidification, concentrating and compressing shrinkage cavities to the top of the ingot, effectively reducing the depth of shrinkage cavities. Furthermore, the liquidus temperature automatically determines the end of feeding, avoiding ineffective long-term low-current operation, shortening the feeding time, and preventing grain coarsening caused by excessive feeding. Therefore, this application can effectively suppress shrinkage defects inside the ingot, reduce riser removal, and improve the quality of the alloy ingot head.

[0026] It should be noted that the infrared thermal imager continuously acquires the surface temperature field matrix of the molten pool at a set sampling frequency. The temperature values ​​of all pixels in the central area are spatially averaged to obtain the average temperature of the central area, and the temperature values ​​of all pixels in the edge area are spatially averaged to obtain the average temperature of the edge area. Then, the sliding differential of the changes of the two over time can be performed to obtain the cooling slope Ke of the central area and the cooling slope Kc of the edge area in real time.

[0027] In some embodiments, in step S2, the preset threshold range is 1.2≤R≤1.5; when R<1.2, the arc is made to converge toward the center area by adjusting the arc stabilizing current; when R>1.5, the arc is made to spread toward the edge area by adjusting the arc stabilizing current.

[0028] In some embodiments, in step S2, by adjusting the current ratio of the upper and lower sets of arc-stabilizing coils, the intersection point of the vertical component Bz and the radial component Br of the magnetic induction intensity is changed, causing the arc to converge towards the center or spread towards the edge. The combined magnetic field of the two sets of coils forms a specific distribution in space, and the relative intensity of Bz (vertical component) and Br (radial component) determines the convergence and divergence of the magnetic field lines. By changing the current ratio of the upper and lower coils, the equivalent focal point of the magnetic field can be moved, thereby affecting the deflection trend of the arc and the distribution of the dwell area on the surface of the molten pool, causing the arc to converge towards the center or spread towards the edge.

[0029] In some embodiments, in step S2, the magnetic field scanning waveform of the arc-stabilizing coil is adjusted from a triangular wave to a square wave. It should be noted that in the magnetic field scanning waveform curve, the horizontal axis represents time, and the vertical axis represents the current magnitude of the arc-stabilizing coil. This curve determines the change of the coil current over time. A triangular wave is used during the normal melting stage to ensure that the arc dwell time at each position is equal, and the heat input received by all parts of the molten pool surface is evenly distributed over time. A square wave is used during the feeding stage to concentrate the arc more in the central or edge area of ​​the molten pool, enhancing central heating and preventing premature cooling of the center.

[0030] In some embodiments, after step S1, the cooling slope Ke of the central region is compared with the target cooling slope K pre-stored in the process database. target Compare the results; based on Ke and K target The deviation is dynamically adjusted by adjusting the current reduction ΔI to make the cooling slope Ke in the central region approach the target cooling slope K. target .

[0031] It should be noted that the process database contains pre-stored optimal cooling curves and target cooling slope K, categorized by alloy grade and crystallizer diameter. target The optimal cooling curve was obtained by fitting thermodynamic numerical simulation with historical furnace measured data, corresponding to an ideal directional solidification state where the molten pool solidification interface is shallow and dish-shaped, with the center temperature consistently 50°C to 80°C higher than the edge temperature. Specifically, using ProCAST or Magma numerical simulation software, with the actual thermophysical parameters of the alloy as input, the movement speed of the solidification front under different current reduction gradients was simulated to obtain the initial value of the theoretically optimal cooling slope; combined with the current curve of the minimum feeding period of the riser detected by ultrasonic testing in actual production, an empirical benchmark value was extracted; infrared thermal imaging was used to record the entire process during 3 to 5 furnace calibration tests, and the curve was iteratively corrected based on the measured shrinkage cavity depth.

[0032] In some embodiments, when |Ke|>|K target | When ΔI is reduced, the actual cooling rate is faster than the target. The molten pool's center temperature drops too rapidly, indicating that the current input is insufficient to maintain the ideal cooling pace, and the molten pool is cooling too quickly. Without intervention, the central region will prematurely form a crust, and the solidification front will advance too quickly from the center outwards, preventing the replenishment of liquid metal to the bottom contraction zone, thus deepening the shrinkage cavity. Reducing ΔI means decreasing the current reduction or even pausing the current reduction to maintain the current level, replenishing more heat to the molten pool, and bringing the cooling rate back to the target value.

[0033] When |Ke|<|K target Increasing ΔI at this point indicates that the actual cooling rate is slower than the target. Insufficient temperature drop at the center of the molten pool indicates excess heat, causing the pool to remain liquid for an extended period. Without intervention, prolonged feeding time and prolonged high temperatures in the liquid metal can lead to coarse grains, increased energy consumption, and potentially deteriorated solidification interface morphology due to an excessively deep pool. Increasing ΔI accelerates current decay, reduces heat input, and pushes the cooling rate back to the target value.

[0034] In some embodiments, the formula for calculating the current drop is: when |Ke|>|K target |When, ΔI=ΔI base×(1-α). If the temperature drops too quickly, the current needs to be reduced less or even stopped, so (1-α) is used to narrow the reduction. The larger α is, the more severe the deviation; the smaller (1-α) is, the smaller the current reduction. In extreme cases, when α approaches 1, ΔI approaches zero. When |Ke| < |K target |When, ΔI=ΔI base ×(1+α). The cooling is too slow, requiring a larger current reduction to accelerate cooling; therefore, (1+α) is used to amplify the cooling amplitude. The larger α is, the more severe the deviation; the larger (1+α) is, the larger the current reduction, resulting in a more rapid current drop and faster cooling of the molten pool. Here, α is an adjustment coefficient positively correlated with the deviation amplitude. The range of α is 0.35-0.4. ΔI base It is the reference current reduction, that is, the amount of current that should be reduced in each control cycle under ideal conditions without any deviation, ΔI. base The range is 500-1000A.

[0035] In some embodiments, the criterion for hot spot disappearance in step S3 is: the temperature of all pixels within the circular area is lower than the liquidus temperature of the molten alloy, and no local hot spots with temperatures more than 20°C higher than the background temperature appear in five consecutive frames. The liquidus temperature is the temperature at which the alloy begins to solidify. The fact that the temperature of all pixels in the entire area is lower than this value indicates that no area on the surface of the molten pool is completely liquid. The background temperature refers to the overall average temperature within the circular area. By accurately determining the end time of feeding, the riser length is shortened while avoiding excessive feeding that leads to grain coarsening.

[0036] In some embodiments, in step S1, the center of the central region coincides with the center of the circular region, with a radius of 1 / 4R to 1 / 3R; the edge region is the remaining annular region after subtracting the central region from the circular region, where R is the radius of the circular region. Since the center of the central region coincides with the center of the circular region, the geometric center of the central region is aligned with the molten pool axis, ensuring that the extracted cooling slope Ke of the central region accurately reflects the thermal state at the molten pool axis. This avoids control misjudgments caused by Ke sampling positions deviating from the true thermal center due to eccentric partitioning. The edge region, the remaining annular region after subtracting the central region from the circular region, ensures that the central and edge regions seamlessly cover the entire molten pool cross-section, with neither overlap nor omission. This ensures that Ke and Kc represent the true cooling behavior of two complementary regions of the molten pool cross-section, thereby guaranteeing that the ratio R accurately quantifies the solidification rate difference between the center and the edge, providing a reliable criterion for controlling the feeding process.

[0037] In some embodiments, in step S1, the sampling frequency of the infrared thermal imager is 15Hz to 30Hz, and the interference generated by the reflection of copper on the inner wall of the crystallizer is filtered out by a dynamic mask algorithm.

[0038] Example 1: TA1 pure titanium ingot (Φ720mm) This embodiment uses TA1 pure titanium as the smelting object, the crystallizer inner diameter is 720mm, and a three-stage VAR smelting process is adopted. The specific implementation process of the present invention is illustrated by taking the feeding stage of the third smelting as an example.

[0039] Step S1: Install a dual-color infrared thermal imager at the observation window of the VAR furnace, with a sampling frequency set to 20Hz. The infrared thermal imager faces the top surface of the crystallizer to acquire the temperature field matrix of the molten pool surface. Based on the crystallizer's inner diameter of 720mm, the system automatically delineates a circular region within the temperature field matrix. This circular region coincides with the circular region of the molten pool viewed from above, and its radius R corresponds to the crystallizer's inner radius of 360mm. Within this circular region, a central region and an edge region are defined: the center of the central region coincides with the center of the circular region, and its radius is set to R / 3, or 120mm, corresponding to the typical scale of the liquid zone in the center of the molten pool during the TA1 alloy feeding period; the edge region is the remaining annular area after subtracting the central region from the circular region, with a width of approximately 240mm. The system continuously acquires the temperature field matrix at a frame rate of 20Hz. A dynamic mask algorithm resets the pixel weights corresponding to the copper inner wall of the crystallizer to zero, filtering out interference from strong infrared reflections from the copper wall on temperature calculations, and only performing statistical calculations on the pixels in the molten pool region.

[0040] Spatially average the temperature values ​​of all pixels in the central and edge regions, and then perform sliding differential on their respective average temperature time series to obtain the real-time cooling slope Ke of the central region and the real-time cooling slope Kc of the edge region.

[0041] Step S2: The system calculates the ratio R = Ke / Kc in real time. The preset threshold range is set to 1.2 ≤ R ≤ 1.5. When R is between 1.2 and 1.5, the molten pool is determined to be in an ideal directional solidification state, and the system maintains the current arc-stabilizing magnetic field parameters unchanged. When R < 1.2, it indicates that the cooling rate in the central region is similar to or even faster than that in the edge region, the directional solidification trend weakens, and the system triggers arc-stabilizing magnetic field adjustment, increasing the proportion of arc dwell time in the central region, strengthening the heat input in the central region, and restoring the temperature gradient from the center outward. When R > 1.5, it indicates that the cooling rate in the edge region is too fast, and the system triggers reverse adjustment. By increasing the current ratio of the lower and upper arc-stabilizing coils, the intersection point of the vertical component Bz and the radial component Br of the magnetic induction intensity is moved downward, expanding the coverage area of ​​the arc in the edge region, supplementing heat to the edge region, and maintaining the unobstructed channel for the downward feeding of the central liquid metal.

[0042] Step S3: The system continuously monitors the temperature field matrix. When the temperature of all pixels within the circular area is below the alloy liquidus temperature, and no local hot spots with a temperature more than 20°C higher than the background temperature appear in 5 consecutive frames (i.e., 0.25 seconds), the system determines that the feeding is complete, and the PLC automatically cuts off the melting power supply to enter the ingot cooling stage.

[0043] Compared with the traditional fixed-program shrinkage method, this embodiment reduces the average hole depth from 85mm to less than 40mm, and reduces the cutting head loss by about 2.8%.

[0044] Example 2: TA4 titanium alloy ingot (Φ860mm) This embodiment uses TA4 low-alloy titanium alloy as the melting object, the inner diameter of the crystallizer is 860mm, and a three-stage VAR melting process is adopted. The specific implementation process of the present invention is illustrated by taking the feeding stage of the third melting as an example.

[0045] Step S1: The sampling frequency of the infrared thermal imager is set to 15Hz. The system delineates a circular region coinciding with the molten pool in the temperature field matrix, with the radius R of the circular region corresponding to the inner radius of the crystallizer, which is 430mm. The radius of the central region is set to R / 3, i.e., 143mm; the edge region is the remaining annular region after subtracting the central region from the circular region, with a width of approximately 287mm. After filtering out copper wall reflection interference using a dynamic mask algorithm, the system continuously extracts the cooling slope Ke of the central region and the cooling slope Kc of the edge region.

[0046] Step S2: For 860mm TA4 alloy ingots, considering the enhanced heat dissipation effect at the edges due to their larger diameter, the preset threshold range is set to 1.2≤R≤1.5. When R<1.2, the system triggers the arc-stabilizing magnetic field to converge towards the center; when R>1.5, the current ratio of the upper and lower arc-stabilizing coils is adjusted to shift the position of the intersection point of Bz and Br towards the edge of the molten pool, thereby expanding the range of the arc's effect in the edge region.

[0047] Step S3: When the temperature of all pixels within the circular area is below the liquidus temperature of TA4 alloy (1655℃), and no local hot spots with a temperature more than 20℃ higher than the background temperature appear in 5 consecutive frames, the system automatically cuts off the power.

[0048] After applying this embodiment, the geometry of the molten pool during the feeding period is closer to the ideal shallow dish shape, with the central liquid solidifying last. The poor feeding defects commonly found in TA4 ingots due to radial segregation of Fe elements are significantly improved.

[0049] Example 3: TC4 titanium alloy ingot (Φ1020mm) This embodiment uses TC4 (Ti-6Al-4V) titanium alloy as the melting object, and the inner diameter of the crystallizer is 1020mm, which is the largest diameter and the most complex specification in terms of process control among the three embodiments of this invention. A three-stage VAR melting process is adopted, and the feeding stage of the third melting is used as an example for illustration.

[0050] Step S1: Considering the large molten pool area of ​​the Φ1020mm ingot and the more significant instantaneous fluctuations in heat flow caused by the movement of the arc foot, the sampling frequency of the infrared thermal imager was increased to 30Hz to ensure accurate capture of sudden heat flow events caused by the movement of the arc foot. The system delineates a circular region in the temperature field matrix, with radius R corresponding to the inner radius of the crystallizer (510mm). The radius of the central region is set to R / 3, i.e., 170mm; the width of the edge region is approximately 340mm. After the dynamic mask algorithm completes the copper wall reflection filtering, the system extracts Ke and Kc in real time at a frame rate of 30Hz.

[0051] Step S2: For a 1020mm TC4 alloy ingot, considering the wide solidification range of TC4 alloy and the strong heat dissipation at the edges of large-diameter ingots, the preset threshold range is set to 1.2≤R≤1.5. When R<1.2, the system triggers the arc-stabilizing coil's magnetic field to converge towards the center, significantly enhancing the heat input in the central region. When R>1.5, the position of the intersection point of Bz and Br is changed by adjusting the current ratio of the upper and lower arc-stabilizing coils, increasing the heat input coverage of the arc in the edge region.

[0052] Step S3: When the temperature of all pixels within the circular area is below the liquidus temperature of TC4 alloy (1660℃), and no local hot spots with a temperature more than 20℃ higher than the background temperature appear in five consecutive frames (i.e., continuous sampling for 0.17 seconds at 30Hz), the system determines that the shrinkage compensation is complete and automatically cuts off the power. TC4 alloy has a wide solidification range, and the mushy region within the solid-liquid two-phase zone has poor thermal conductivity. The five-frame confirmation mechanism effectively prevents misjudgments caused by a brief rise in surface temperature due to convection within the molten pool.

[0053] After the application of this embodiment, compared with the traditional stepped flow reduction and feeding process of the same specification, the shrinkage depth of the ingot head is reduced from an average of 120mm to less than 55mm, the macroscopic segregation of Al at the ingot head is significantly improved, and the overall quality stability of the ingot is significantly improved.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A vacuum consumable melting method, characterized in that, The following steps are performed during the feeding stage of vacuum arc remelting: Step S1: Obtain a temperature field matrix using an infrared thermal imager. The temperature field matrix is ​​a temperature field matrix facing the crystallizer. Delineate a circular region in the temperature field matrix, which coincides with the circular region of the molten pool. Divide the circular region into a central region and an edge region, and extract the cooling slope Ke of the central region and the cooling slope Kc of the edge region, respectively. In step S2, the solidification state is determined in real time based on the ratio of the cooling slope of the center to the edge, R=Ke / Kc. When R exceeds the preset threshold range, the arc stabilizing magnetic field is adjusted to force the molten pool to solidify in a directional manner. In step S3, when the temperature of the entire circular region is lower than the liquidus temperature of the molten alloy and the hot spot disappears, the feeding is completed and the power is automatically cut off.

2. The vacuum consumable melting method according to claim 1, characterized in that, In step S2, the preset threshold range is 1.2≤R≤1.5; when R<1.2, the arc is made to converge toward the center area by adjusting the arc stabilizing current; when R>1.5, the arc is made to diffuse toward the edge area by adjusting the arc stabilizing current.

3. The vacuum consumable melting method according to claim 2, characterized in that, In step S2, by adjusting the current ratio of the upper and lower sets of arc-stabilizing coils, the intersection point of the vertical component Bz and the radial component Br of the magnetic induction intensity is changed, causing the electric arc to converge toward the central region or spread toward the edge region.

4. The vacuum consumable melting method according to claim 3, characterized in that, In step S2, the magnetic field scanning waveform of the arc stabilizing coil is adjusted from a triangular wave to a square wave.

5. The vacuum consumable melting method according to claim 1, characterized in that, After step S1, the cooling slope Ke of the central region is compared with the target cooling slope K pre-stored in the process database. target Compare the results; based on Ke and K target The deviation is dynamically adjusted by adjusting the current reduction ΔI to make the cooling slope Ke in the central region approach the target cooling slope K. target .

6. The vacuum consumable melting method according to claim 5, characterized in that, When |Ke|>|K target |When |Ke|<|K, decrease ΔI, when |Ke|<|K target |Increases ΔI.

7. The vacuum consumable melting method according to claim 6, characterized in that, The formula for calculating the current drop is: when |Ke|>|K target |When, ΔI=ΔI base ×(1-α); when |Ke|<|K target |When, ΔI=ΔI base ×(1+α); where α is an adjustment coefficient positively correlated with the deviation amplitude, and the range of α is 0.35-0.4, ΔI base It is the reduction in reference current, ΔI base The range is 500-1000A.

8. The vacuum consumable melting method according to any one of claims 1 to 7, characterized in that, In step S3, the condition for determining the disappearance of the hot spot is: the temperature of all pixels in the circular area is lower than the liquidus temperature of the molten alloy, and no local hot spots with a temperature higher than the background temperature by more than 20°C appear in 5 consecutive frames of images.

9. The vacuum arc remelting method according to any one of claims 1 to 7, characterized in that, In step S1, the center of the central region coincides with the center of the circular region, and the radius is 1 / 4R to 1 / 3R; the edge region is the remaining annular region of the circular region minus the central region, where R is the radius of the circular region.

10. The vacuum consumable melting method according to any one of claims 1 to 7, characterized in that, In step S1, the sampling frequency of the infrared thermal imager is 15Hz to 30Hz, and the interference generated by the copper reflection from the inner wall of the crystallizer is filtered out by a dynamic mask algorithm.

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