A method for preparing a high-temperature alloy ingot without metallurgical defects by double vacuum consumable arc melting and application thereof

Abstract

The present application belongs to the technical field of high-end high-temperature alloy smelting, and relates to a method for preparing a high-temperature alloy ingot without metallurgical defects by double vacuum consumable arc smelting and application. The method comprises the following steps: firstly, a consumable electrode with required components is prepared by using a vacuum induction smelting furnace; secondly, the consumable electrode is subjected to first-stage vacuum consumable arc smelting at a first smelting rate and second-stage vacuum consumable arc smelting at a second smelting rate; at the end of the second-stage vacuum consumable arc smelting, a hot sealing top is performed by using a step-by-step decreasing current mode, and finally a high-temperature alloy ingot without metallurgical defects is obtained. The preparation method can eliminate conventional metallurgical defects such as porosity, inclusions and segregation from the root, effectively avoids problems such as excessive inclusions, element segregation and harmful phase precipitation existing in the traditional process, significantly improves the uniformity of the ingot structure and the metallurgical purity, and realizes comprehensive improvement of the comprehensive service performance of the high-temperature alloy ingot.

Description

Technical Field

[0001] This invention belongs to the field of high-end high-temperature alloy smelting technology, and relates to a method and application for preparing high-temperature alloy ingots without metallurgical defects by dual vacuum self-consuming arc smelting. Background Technology

[0002] As core load-bearing rotating components of aero engines, turbine disks and shafts directly determine the engine's reliability, lifespan, and safety limits through their material properties, particularly high-cycle fatigue and creep resistance. GH4169 alloy, with its superior comprehensive mechanical properties over a wide temperature range and excellent fatigue and corrosion resistance, has become the preferred material for manufacturing such components.

[0003] Currently, vacuum induction melting (VIM) + vacuum arc remelting (VAR) or vacuum induction melting (VIM) + electroslag remelting (ESR) + vacuum arc remelting (VAR) are traditional melting processes, but both have inherent drawbacks. On the one hand, in the VIM + VAR process, the single-pass vacuum arc remelting has limited effect on removing micron-sized Al2O3 inclusions. On the other hand, in order to balance production and melting stability, the selected melting rate easily causes the melt pool depth to deviate from the reasonable range—a shallow melt pool easily produces white spot defects, corresponding to a region of element depletion in the γ' phase; a deep melt pool will produce black spots, forming a niobium enrichment segregation zone, which is very easy to induce fatigue crack initiation. On the other hand, in the process of vacuum induction melting (VIM) + electroslag remelting (ESR) + vacuum arc remelting (VAR), when electroslag remelting is carried out with slag systems such as S2059, it is easy to introduce non-metallic inclusions containing calcium and fluorine, and there is also the problem of loss of active elements such as aluminum and titanium. In addition, the composition difference between the head and tail of large-sized ingots is more significant, which seriously affects the intrinsic properties of the material and the accuracy of composition control.

[0004] Therefore, there is an urgent need to develop a method for preparing high-temperature alloy ingots without metallurgical defects by dual vacuum self-consuming arc melting to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and propose a method and application for preparing high-temperature alloy ingots without metallurgical defects by dual vacuum self-consuming arc melting. This invention provides a three-stage melting process with full vacuum and no slag contamination: vacuum induction melting (VIM) + first-stage vacuum self-consuming arc melting (VAR1) + second-stage vacuum self-consuming arc melting (VAR2). Among them, the first-stage vacuum self-consuming arc melting (VAR1) focuses on the deep purification of the ingot, and the second-stage vacuum self-consuming arc melting (VAR2) focuses on the microstructure optimization of the ingot. Through the coordinated control of the parameters of the two vacuum self-consuming arc melting processes, the resulting ingot has high purity, excellent microstructure uniformity, stable composition and no metallurgical defects.

[0006] To achieve the above objectives, the present invention discloses the following technical solution: In a first aspect, the present invention employs a method for preparing high-temperature alloy ingots free of metallurgical defects through dual vacuum consumable arc melting, comprising the following steps: Step 1: Under vacuum conditions, Ni, Fe, Cr, Co, Mo and nickel-niobium master alloy are completely melted and then refined; after refining, the temperature is raised to the target temperature and Al and Ti are added. After the two are completely melted, the target temperature is maintained constant, and then nickel-boron master alloy and nickel-phosphorus master alloy are added; after alloying is completed, samples are taken for inspection. After the inspection is qualified, the consumable electrode is obtained by casting. Step 2: The consumable electrode is subjected to first-stage vacuum consumable arc melting at a first melting rate, and then to second-stage vacuum consumable arc melting at a second melting rate; at the end of the second-stage vacuum consumable arc melting, the current is gradually reduced to perform heat sealing, and finally a high-temperature alloy ingot without metallurgical defects is obtained.

[0007] Specifically, in step 1, the consumable electrode is prepared in a vacuum induction melting furnace.

[0008] Specifically, in step 1, the vacuum level in the vacuum induction melting furnace is preferably ≤0.3 Pa throughout the entire process of preparing the consumable electrode.

[0009] Specifically, the complete melting temperature of Ni, Fe, Cr, Co, Mo, and nickel-niobium master alloys is 1400℃~1450℃.

[0010] Specifically, the refining temperature is 1525~1535℃, and the refining time is preferably 30~60min.

[0011] More specifically, in this invention, the refining temperature is the optimal range determined for the target alloy system and process route of this invention. Within this temperature range, better degassing effect and other process advantages can be achieved.

[0012] Specifically, the target temperature at which Al and Ti are completely melted is 1540~1550℃.

[0013] Specifically, the nickel raw material (Ni) includes, but is not limited to, metallic nickel and nickel beads; the iron raw material (Fe) includes, but is not limited to, metallic iron blocks; the chromium raw material (Cr) includes, but is not limited to, metallic chromium blocks; the cobalt raw material (Co) includes, but is not limited to, cobalt plates; and the molybdenum raw material (Mo) includes, but is not limited to, molybdenum bars and molybdenum plates.

[0014] Specifically, in step 1, the sampling operation involves the following steps: First, maintaining the refining temperature and allowing the alloy liquid after alloying to stand still; then, sampling the alloy liquid and using a fluorescence spectrometer to detect the composition, confirming that the content of each element is within the target range.

[0015] More specifically, the preferred resting time is 5 minutes.

[0016] Specifically, in step 1, the specific steps of the casting operation are as follows: reduce the power to maintain the temperature of the alloy liquid at the process set temperature, and then pour it into the preheated steel ingot mold.

[0017] More specifically, the process setting temperature is preferably 1450~1470℃; after preheating, the temperature of the steel ingot mold is preferably 590~610℃.

[0018] Specifically, the niobium (Nb) content deviation at the head and tail of the consumable electrode obtained in step 1 is ≤0.05%.

[0019] Furthermore, in step 2, the vacuum degree of the first-stage vacuum self-consuming arc melting is ≤0.08 Pa, and the first melting rate is 2.7~5.3 kg / min.

[0020] Specifically, with the help of infrared thermal imaging monitoring, the first melting rate can stably maintain the depth of the molten pool at about 1 / 2 of the ingot diameter, which is conducive to efficient heat transfer and removal of inclusions.

[0021] Specifically, during the first-stage vacuum self-consuming arc melting process, when the first melting rate is 2.7~5.3 kg / min, the corresponding first steady-state melting current is 8.5~14 kA, the first melting voltage is 22~27V, and the cooling water pressure is preferably 0.45 MPa.

[0022] Furthermore, during the first-stage vacuum self-consuming arc melting process, when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ406mm, the first melting rate is 2.7~2.9 kg / min; when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ508mm, the first melting rate is 3.9~4.1 kg / min; and when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ660mm, the first melting rate is 5.1~5.3 kg / min.

[0023] Specifically, during the first-stage vacuum self-consuming arc melting process, when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ406mm, the corresponding first steady-state melting current is 8.5~9.0kA and the first melting voltage is 22~24V; when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ508mm, the corresponding first steady-state melting current is 10.4~10.6kA and the first melting voltage is 24~26V; when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ660mm, the corresponding first steady-state melting current is 13.5~14.0kA and the first melting voltage is 26~27V.

[0024] Furthermore, in step 2, the vacuum degree of the secondary vacuum self-consuming arc melting is ≤0.03 Pa, and the second melting rate is 2.1~3.9 kg / min.

[0025] Specifically, with the help of infrared thermal imaging monitoring, the second smelting rate can control the depth of the molten pool to 1 / 3 of the ingot diameter, and the molten pool is generally shallow and flat.

[0026] Specifically, during the secondary vacuum self-consuming arc melting process, when the second melting rate is 2.1~3.9 kg / min, the corresponding second steady-state melting current is 6.8~10.8 kA, the second melting voltage is 20~27 V, and the cooling water pressure is preferably 0.45 MPa.

[0027] Furthermore, in the secondary vacuum self-consuming arc melting process, when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ406mm, the second melting rate is 2.1~2.3kg / min; when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ508mm, the second melting rate is 2.9~3.1kg / min; and when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ660mm, the second melting rate is 3.7~3.9kg / min.

[0028] Specifically, during the secondary vacuum self-consuming arc melting process, when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ406mm, the corresponding second steady-state melting current is 6.8~7.2 kA and the second melting voltage is 20~22V; when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ508mm, the corresponding second steady-state melting current is 8.1~8.3kA and the second melting voltage is 20~22V; when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ660mm, the corresponding second steady-state melting current is 10.5~10.8kA and the second melting voltage is 26~27V.

[0029] Furthermore, in step 2, during the hot capping stage, the final hot capping current is 40% to 50% of the second steady-state melting current.

[0030] Specifically, the hot capping process can slow down the cooling rate of the ingot head, ensuring that liquid metal is continuously supplied to the shrinkage area during solidification, thereby completing dynamic feeding, avoiding the formation of shrinkage cavities and porosity inside, and making the ingot head structure uniform and dense.

[0031] More specifically, the preferred heat sealing time is 2 hours.

[0032] In a second aspect, the present invention discloses a high-temperature alloy ingot free of metallurgical defects. The ingot is prepared by the double vacuum consumable arc melting method described in the first aspect above. Its oxygen content is ≤3.5ppm, nitrogen content is ≤4.0ppm, and the niobium element segregation ratio between dendrites and dendrite trunks is ≤1.20. The range of Al and Ti elements at the head and tail of the high-temperature alloy ingot free of metallurgical defects is ≤0.03%.

[0033] Thirdly, the present invention discloses the method for preparing metallurgically defect-free high-temperature alloy ingots by double vacuum self-consuming arc melting as described in the first aspect, and the application of the metallurgically defect-free high-temperature alloy ingots as described in the second aspect in the core load-bearing rotating components of aero-engines and gas turbines.

[0034] Specifically, the core load-bearing rotating components include key components such as turbine disks, turbine shafts, compressor disks, and casings of aero engines and gas turbines.

[0035] Compared with the prior art, the present invention has the following beneficial effects: First, this invention proposes a method for preparing high-temperature alloy ingots without metallurgical defects by dual vacuum self-consuming arc melting. Its core lies in the effective synergy between vacuum induction melting (VIM), first-stage vacuum self-consuming arc melting (VAR1), and second-stage vacuum self-consuming arc melting (VAR2).

[0036] First, the melting rate of the first-stage vacuum arc melting is 2.7~5.3 kg / min, and the melting rate of the second-stage vacuum arc melting is 2.1~3.9 kg / min, with the latter melting rate being much lower than the former. This specific low melting rate setting helps to form a shallow and flat molten pool and establish a steep temperature gradient, thereby ensuring that during the second-stage vacuum arc melting process, on the one hand, the micro-segregation of alloying elements can be significantly suppressed (Nb segregation ratio ≤1.20), and on the other hand, the residence time of liquid metal can be extended, the floating distance of inclusions can be reduced, and the violent agitation of the molten pool can be suppressed, allowing fine inclusions to float steadily under the action of buoyancy, thus achieving effective removal.

[0037] Secondly, the primary stage of vacuum arc remelting (VAR1) aims at coarse purification, initially removing most of the gas and large inclusions from the melt. The secondary stage of vacuum arc remelting (VAR2) acts as a fine scavenger, further removing residual fine inclusions and residual gas. Simultaneously, the entire process is carried out in a full vacuum environment, preventing the introduction of external impurities such as oxides and dust from the atmosphere into the melt. Through this two-stage vacuum arc remelting purification, the oxygen content of the finished ingot is no higher than 3.5 ppm, the nitrogen content is no higher than 4.0 ppm, and the inclusion level is excellent, with both gas content and inclusion control indicators reaching industry-leading levels.

[0038] Finally, compared with the traditional two-stage process (VIM+VAR), this invention significantly improves the stability of the molten pool and the uniformity of composition in the final remelting process by adding a first-stage vacuum consumable arc melting process. Combined with the process design, it can avoid the occurrence of white spot metallurgical defects.

[0039] Secondly, the high-temperature alloy ingots produced using the above-mentioned process are free of metallurgical defects, exhibiting no solidification defects such as white or black spots, and possessing fine grain size and excellent uniformity of axial columnar crystal structure. Compared to the traditional triple process (VIM+ESR+VAR), this invention effectively avoids the loss of active elements caused by slag and significantly controls the compositional deviation of Al and Ti elements at the beginning and end of the ingot. The resulting ingots demonstrate excellent fatigue performance and creep life, with stable mechanical properties, meeting the requirements for long-term safe service and high reliability design of components. Attached Figure Description

[0040] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0042] Figure 1 This is a flowchart of the preparation method of the present invention; Figure 2 This is a low-magnification microstructure of the high-temperature alloy ingot DB-1, which is Comparative Example 1 of this invention. Figure 3 This is a microstructure of the uncorroded state of the "white spot" defect in the high-temperature alloy ingot DB-1 of Comparative Example 1 of this invention; Figure 4 This is a microstructure of the corrosion state at the "white spot" defect region D in the high-temperature alloy ingot DB-1 of Comparative Example 1 of this invention; Figure 5 This is a low-magnification microstructure of the high-temperature alloy ingot DB-2, which is Comparative Example 2 of this invention. Figure 6 This is a corrosion-state microstructure of the "black spot" defect in region A of the high-temperature alloy ingot DB-2, which is Comparative Example 2 of this invention. Figure 7 This is a microstructure diagram of the segregation channel in region B of the high-temperature alloy ingot DB-2, which is Comparative Example 2 of this invention. Figure 8 This is a high-magnification microstructure of region C in the high-temperature alloy ingot DB-2, which is Comparative Example 2 of this invention. Detailed Implementation

[0043] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0044] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0045] Example 1 This embodiment provides a method for preparing high-temperature alloy ingots without metallurgical defects by dual-vacuum consumable arc melting, including the following steps: Step 1: Place nickel blocks, iron blocks, chromium blocks, cobalt plates, molybdenum plates, and nickel-niobium master alloys into a vacuum induction melting furnace, evacuate to ≤0.3 Pa, and refine them after complete melting at 1410±10℃. The refining temperature is 1530±5℃ and the refining time is 30 min. After refining, the temperature is raised to 1540℃, aluminum briquettes and titanium blocks are added, and after they are completely melted, the temperature is maintained at 1540℃. Then, nickel-boron master alloy and nickel-phosphorus master alloy are added. After alloying is completed, the temperature is maintained at 1540℃, and the alloy liquid is cooled for 5 minutes. Samples are then taken for fluorescence spectroscopy analysis to confirm that the content of each element in the alloy liquid is within the target range. After passing the test, the power is reduced to maintain the temperature of the alloy liquid at 1450℃, and then it is poured into a steel ingot mold to obtain a Φ350mm consumable electrode. The surface quality of the consumable electrode is good, and the niobium (Nb) content deviation at the head and tail is ≤0.05%.

[0046] Specifically, the crucible inside the vacuum induction melting furnace is made of aluminum-magnesium spinel.

[0047] Specifically, before casting, the steel ingot mold is preheated to 590°C.

[0048] Step 2: First, the prepared Φ350mm consumable electrode is placed into a vacuum consumable arc furnace, and a Φ406mm water-cooled copper crystallizer is used. First-stage vacuum consumable arc melting is carried out under a vacuum condition of ≤0.06Pa. The first steady-state melting current is 10.4~10.6kA, the first melting voltage is 24~26V, and the cooling water pressure is 0.45MPa. During stable melting, the first melting rate is precisely stabilized at 4.0±0.1kg / min using a melting rate-droplet closed-loop control system. Infrared thermal imaging monitoring shows that the depth of the molten pool is approximately half the diameter of the ingot.

[0049] Subsequently, the ingot obtained from the first-stage vacuum arc remelting was loaded into a vacuum arc remelting furnace, equipped with a Φ508mm water-cooled copper crystallizer, and a second-stage vacuum arc remelting was carried out under a vacuum condition of ≤0.02Pa. The second steady-state melting current was 8.1~8.3kA, the second melting voltage was 20~22V, and the cooling water pressure was 0.45MPa. During the stable melting period, the second melting rate was precisely stabilized at 3.0±0.1kg / min using a melting rate-droplet closed-loop control system. Infrared thermal imaging monitoring showed that the molten pool was generally shallow and flat.

[0050] At the end of the secondary vacuum self-consuming arc melting process, the current is gradually reduced to 50% (approximately 4kA) of the second steady-state melting current, and the hot capping is continued for 2 hours under this condition. After the melting process is completed, the ingot is cooled and demolded to finally obtain a Φ508mm high-temperature alloy ingot without metallurgical defects.

[0051] Example 2 This embodiment provides a method for preparing high-temperature alloy ingots without metallurgical defects by dual-vacuum consumable arc melting, including the following steps: Step 1: Place nickel blocks, iron blocks, chromium blocks, cobalt plates, molybdenum plates, and nickel-niobium master alloys into a vacuum induction melting furnace, evacuate to ≤0.3 Pa, and refine them after complete melting at 1425±10℃. The refining temperature is 1530±5℃ and the refining time is 40 min. After refining, the temperature is raised to 1545℃, aluminum briquettes and titanium blocks are added, and after they are completely melted, the temperature is maintained at 1545℃, and then nickel-boron master alloy and nickel-phosphorus master alloy are added. After alloying is completed, the temperature is maintained at 1545℃, and the alloy liquid is cooled for 5 minutes. Samples are then taken for fluorescence spectroscopy analysis to confirm that the content of each element in the alloy liquid is within the target range. After passing the test, the power is reduced to maintain the temperature of the alloy liquid at 1460℃, and then it is poured into a steel ingot mold to obtain a Φ260mm consumable electrode. The surface quality of the consumable electrode is good, and the niobium (Nb) content deviation at the head and tail is ≤0.05%.

[0052] Specifically, the crucible inside the vacuum induction melting furnace is made of aluminum-magnesium spinel.

[0053] Specifically, before casting, the steel ingot mold is preheated to 600°C.

[0054] Step 2: First, the prepared Φ260mm consumable electrode is placed into a vacuum consumable arc furnace, and a Φ320mm water-cooled copper crystallizer is used. First-stage vacuum consumable arc melting is carried out under a vacuum condition of ≤0.08Pa. The first steady-state melting current is 8.5~9.0kA, the first melting voltage is 22~24V, and the cooling water pressure is 0.45MPa. During stable melting, the first melting rate is precisely stabilized at 2.8±0.1kg / min using a melting rate-droplet closed-loop control system. Infrared thermal imaging monitoring shows that the depth of the molten pool is approximately half the diameter of the ingot.

[0055] Subsequently, the ingot obtained by the first-stage vacuum arc melting was loaded into a vacuum arc furnace and equipped with a Φ406mm water-cooled copper crystallizer. The second-stage vacuum arc melting was carried out under a vacuum condition of ≤0.03Pa. The second steady-state melting current was 6.8~7.2kA, the second melting voltage was 20~22V, and the cooling water pressure was 0.45MPa. During the stable melting period, the second melting rate was precisely stabilized at 2.2±0.1kg / min using a melting rate-droplet closed-loop control system. Infrared thermal imaging monitoring showed that the molten pool was generally shallow and flat.

[0056] At the end of the secondary vacuum self-consuming arc melting process, the current is gradually reduced to 45% (approximately 3kA) of the second steady-state melting current, and the hot capping is continued for 2 hours under this condition. After the melting process is completed, the ingot is cooled and demolded to finally obtain a Φ406mm high-temperature alloy ingot without metallurgical defects.

[0057] Example 3 This embodiment provides a method for preparing high-temperature alloy ingots without metallurgical defects by dual-vacuum consumable arc melting, including the following steps: Step 1: Place nickel blocks, iron blocks, chromium blocks, cobalt plates, molybdenum plates, and nickel-niobium master alloy into a vacuum induction melting furnace, evacuate to ≤0.3 Pa, and refine after complete melting at 1440±10℃. The refining temperature is 1530±5℃ and the refining time is 60 min. After refining, the temperature is raised to 1550℃, aluminum briquettes and titanium blocks are added, and after they are completely melted, the temperature is maintained at 1550℃, and then nickel-boron master alloy and nickel-phosphorus master alloy are added. After alloying is completed, the temperature is maintained at 1550℃, and the alloy liquid is cooled for 5 minutes. Samples are then taken for fluorescence spectroscopy analysis to confirm that the content of each element in the alloy liquid is within the target range. After the test is qualified, the power is reduced to maintain the temperature of the alloy liquid at 1470℃, and then it is poured into a steel ingot mold to obtain a Φ500mm consumable electrode. The surface quality of the consumable electrode is good, and the niobium (Nb) content deviation at the head and tail is ≤0.05%.

[0058] Specifically, the crucible inside the vacuum induction melting furnace is made of aluminum-magnesium spinel.

[0059] Specifically, before casting, the steel ingot mold is preheated to 600°C.

[0060] Step 2: First, the prepared Φ500mm consumable electrode is placed into a vacuum consumable arc furnace, and a Φ600mm water-cooled copper crystallizer is used. First-stage vacuum consumable arc melting is carried out under a vacuum condition of ≤0.06Pa. The first steady-state melting current is 13.5~14.0kA, the first melting voltage is 26~27V, and the cooling water pressure is 0.45MPa. During stable melting, the first melting rate is precisely stabilized at 5.2±0.1kg / min using a melting rate-droplet closed-loop control system. Infrared thermal imaging monitoring shows that the depth of the molten pool is approximately half the diameter of the ingot.

[0061] Subsequently, the ingot obtained by the first-stage vacuum arc melting was loaded into a vacuum arc furnace and equipped with a Φ660mm water-cooled copper crystallizer. The second-stage vacuum arc melting was carried out under a vacuum condition of ≤0.02Pa. The second steady-state melting current was 10.5~10.8kA, the second melting voltage was 26~27V, and the cooling water pressure was 0.45MPa. During the stable melting period, the second melting rate was precisely stabilized at 3.8±0.1kg / min using a melting rate-droplet closed-loop control system. Infrared thermal imaging monitoring showed that the molten pool was generally shallow and flat.

[0062] At the end of the secondary vacuum self-consuming arc melting process, the current is gradually reduced to 40% (approximately 4.5kA) of the second steady-state melting current, and the hot capping is continued for 2 hours under this condition. After the melting process is completed, the ingot is cooled and demolded to finally obtain a Φ660mm high-temperature alloy ingot without metallurgical defects.

[0063] Comparative Example 1 This comparative example provides a method for preparing high-temperature alloy ingots, which employs a dual process of conventional vacuum induction melting (VIM) and vacuum arc remelting (VAR), including the following steps: Step 1: Place nickel blocks, iron blocks, chromium blocks, cobalt plates, molybdenum plates, and nickel-niobium master alloys into a vacuum induction melting furnace, evacuate to ≤0.3 Pa, and refine them after complete melting at 1410±10℃. The refining temperature is 1530±5℃ and the refining time is 30 min. After refining, the temperature is raised to 1540℃, aluminum briquettes and titanium blocks are added, and after they are completely melted, the temperature is maintained at 1540℃. Then, nickel-boron master alloy and nickel-phosphorus master alloy are added. After alloying is completed, the temperature is maintained at 1540℃, and the alloy liquid is cooled for 5 minutes. Samples are then taken for fluorescence spectroscopy analysis to confirm that the content of each element in the alloy liquid is within the target range. After passing the test, the power is reduced to maintain the temperature of the alloy liquid at 1450℃, and then it is poured into a steel ingot mold to obtain a Φ406mm consumable electrode. The surface quality of the consumable electrode is good, and the deviation of the niobium (Nb) content at the head and tail is ≤0.05%.

[0064] Specifically, the crucible inside the vacuum induction melting furnace is made of aluminum-magnesium spinel.

[0065] Specifically, before casting, the steel ingot mold is preheated to 590°C.

[0066] Step 2: The prepared Φ406mm consumable electrode is placed into a vacuum consumable arc furnace and equipped with a Φ508mm water-cooled copper crystallizer. Vacuum consumable arc melting is carried out under a vacuum condition of ≤0.06Pa. The steady-state melting current is 8.1~8.3kA, the melting voltage is 20~22V, and the cooling water pressure is 0.45MPa. During the stable melting period, the melting rate is precisely stabilized at 3.0±0.1kg / min using a melting rate-droplet closed-loop control system. Infrared thermal imaging monitoring shows that the depth of the molten pool is approximately 1 / 3 of the ingot diameter, and the overall shape is shallow and flat.

[0067] At the end of the vacuum self-consuming arc melting process, the current is gradually reduced to 50% of the steady-state melting current (approximately 4kA), and the hot capping is continued for 2 hours under this condition. After the melting process is completed, the ingot is cooled and demolded to obtain a high-temperature alloy ingot DB-1 with a specification of Φ508mm.

[0068] Comparative Example 2 This comparative example provides a method for preparing high-temperature alloy ingots. This method employs a three-stage process of conventional vacuum induction melting (VIM), electroslag remelting (ESR), and vacuum arc remelting (VAR), including the following steps: Step 1: Place nickel blocks, iron blocks, chromium blocks, cobalt plates, molybdenum plates, and nickel-niobium master alloys into a vacuum induction melting furnace, evacuate to ≤0.3 Pa, and refine them after complete melting at 1410±10℃. The refining temperature is 1530±5℃ and the refining time is 30 min. After refining, the temperature is raised to 1540℃, aluminum briquettes and titanium blocks are added, and after they are completely melted, the temperature is maintained at 1540℃. Then, nickel-boron master alloy and nickel-phosphorus master alloy are added. After alloying is completed, the temperature is maintained at 1540℃, and the alloy liquid is cooled for 5 minutes. Samples are then taken for fluorescence spectroscopy analysis to ensure that the content of each element in the alloy liquid is within the target range. After the test is qualified, the power is reduced to maintain the temperature of the alloy liquid at 1450℃, and then it is poured into a steel ingot mold to obtain a Φ350mm consumable electrode. The surface quality of the consumable electrode is good, and the niobium (Nb) composition deviation at the head and tail is ≤0.05%.

[0069] Specifically, the crucible inside the vacuum induction melting furnace is made of aluminum-magnesium spinel.

[0070] Specifically, before casting, the steel ingot mold is preheated to 590°C.

[0071] Step 2: Place the prepared Φ350mm consumable electrode in a protective atmosphere electroslag remelting furnace and use a Φ450mm water-cooled copper crystallizer for electroslag remelting. During the electroslag remelting process, the S2059 slag system is used, and the smelting rate during the slag formation period is controlled at 210~285kg / h, and the slag wave amplitude is controlled at 0.1~0.6mohm. After entering the stable smelting period, the smelting rate is 250±5 kg / h, and the slag wave amplitude is 0.32±1mohm. After the smelting is completed, cool for 50 minutes to obtain the electroslag ingot.

[0072] Specifically, the S2059 slag system is composed of 50% CaF2, 22% CaO, 22% Al2O3 and 6% MgO by mass fraction.

[0073] Step 3: The electroslag ingot is loaded into a vacuum consumable arc furnace and equipped with a Φ508mm water-cooled copper crystallizer. Vacuum consumable arc melting is carried out under a vacuum condition of ≤0.02Pa. During the melting process, the steady-state melting current is 10.5~10.8kA, the melting voltage is 26~27V, and the cooling water pressure is 0.45MPa. During the stable melting period, the second melting rate is precisely stabilized at 3.8±0.1kg / min using a melting rate-droplet closed-loop control system. Infrared thermal imaging monitoring shows that the depth of the molten pool is approximately 1 / 3 of the ingot diameter, and the molten pool is generally shallow and flat.

[0074] Subsequently, at the end of the vacuum self-consuming arc melting process, the hot capping current was reduced to 48% (approximately 5kA) of the steady-state melting current by gradually decreasing the current, and the hot capping was continued for 2 hours under this condition. After the melting process was completed, the ingot was cooled and demolded to finally obtain a high-temperature alloy ingot DB-2 with a diameter of 508mm.

[0075] Furthermore, to verify the effect of the preparation process of this application on improving the metallurgical quality and service performance of the ingots, the metallurgically defect-free high-temperature alloy ingots 1, 2, and 3 prepared in the examples, as well as the high-temperature alloy ingots DB-1 and DB-2 prepared in the comparative examples, were uniformly tested for metallurgical purity, compositional uniformity, and high-temperature mechanical properties. The metallurgical purity indicators included oxygen content and nitrogen content; the compositional uniformity indicators included niobium segregation ratio and the average range of Al / Ti content at the ingot head and tail; and the high-temperature mechanical properties indicators included fatigue strength and high-temperature creep life. The test results for each ingot are shown in Table 1.

[0076] Table 1 Comparison of comprehensive properties of various high-temperature alloy ingots Examples 1-3 prepared high-temperature alloy ingots with metallurgical defects free of defects, with specifications of Φ508mm, Φ406mm, and Φ660mm respectively. The above three specifications are the mainstream application sizes of ingots used for core load-bearing rotating components of current aero engines.

[0077] As shown in Table 1, in terms of metallurgical purity, the oxygen content of the ingots of Φ406mm, Φ508mm, and Φ660mm prepared by the process of this invention is stably controlled at 3.0~3.5ppm and the nitrogen content is stably controlled at 3.8~4.0ppm, which is at an extremely low level in the industry, and the gas content of ingots of different specifications fluctuates very little. In contrast, the oxygen and nitrogen contents of the ingots prepared by the VIM+VAR dual process reach 6.5ppm and 7.1ppm respectively, which is more than twice that of Example 1. Even the oxygen and nitrogen contents of the ingots prepared by the high-end VIM+ESR+VAR triple process in the industry can only be reduced to 4.9ppm and 5.3ppm respectively, which are still significantly higher than those of the ingots prepared by the process of this invention.

[0078] Regarding compositional uniformity, the Nb segregation ratio of the ingot produced by the process of this invention is only 1.13~1.15, which is 21%~22% lower than that of the VIM+VAR dual process (Nb segregation ratio 1.45) and 12%~13% lower than that of the VIM+ESR+VAR triple process (Nb segregation ratio 1.30). At the same time, the average range of Al / Ti elements at the beginning and end of the ingot is only 0.02%~0.03%, which is far lower than the range level of the high-end VIM+ESR+VAR triple process, reducing it by 75%, and completely solving the problem of compositional fluctuations at the beginning and end of large-size ingots.

[0079] Regarding core service performance, the fatigue strength of the ingots prepared by this invention is consistently between 558 and 570 MPa, representing a 17% to 19% improvement over the 480 MPa of the VIM+VAR dual-process ingots and a 6% to 9% improvement over the 525 MPa of the VIM+ESR+VAR triple-process ingots. Furthermore, the performance fluctuation of the ingots in the examples is only ±12 to ±16 MPa, with data dispersion far lower than the two comparative examples, demonstrating excellent performance consistency. Simultaneously, the creep rupture life of the ingots in Examples 1 to 3 is consistently above 200 hours, more than twice the average of the VIM+VAR dual-process and nearly 70% higher than the average of the VIM+ESR+VAR triple-process, fully meeting the long-life and high-reliability service requirements of high-end high-temperature alloys.

[0080] In addition, such as Figure 2 As shown, the microstructure of the high-temperature alloy ingot DB-1 of Comparative Example 1 is low magnified. Typical "white spot" defects can be observed in the cross section of the ingot (shown in the area marked by the red circle in the figure).

[0081] To further reveal the nature of this defect, metallographic characterization was performed on defect region D. Its uncorroded microstructure morphology is shown below. Figure 3 As shown, in the uncorroded state, it can be clearly observed that the white spot area is not a uniform component segregation band, but is composed of dark aggregates distributed in a continuous, chain-like manner. These aggregates are distributed in an irregular band-like pattern within the matrix.

[0082] After etching the sample, the microstructure morphology of defect region D is as follows: Figure 4 As shown, the matrix grain boundary structure is clearly exposed, and defect aggregates are found to be mainly distributed along the grain boundaries, forming continuous chain-like channels that severely disrupt the overall continuity of the matrix structure. EDS compositional analysis of this defect area yielded results shown in Table 2. The aggregates are composite oxide inclusions containing Mg, Al, and Nb, with an oxygen content as high as 32.98 wt.%, typical of deoxidation products or slag-like foreign inclusions. The presence of such "dirty white spots" defects significantly damages the integrity of the matrix structure, easily inducing stress concentration and crack initiation, and significantly reducing the fatigue strength and creep life of the ingot. It is one of the key metallurgical defects restricting the improvement of the overall performance of high-temperature alloy ingots produced by the conventional VIM+VAR dual-process.

[0083] Table 2. EDS energy dispersive spectroscopy analysis results of "dirty white spots" inclusions in Comparative Example 1 element Quality score (%) Atomic fraction (%) C 6.04 11.68 O 32.98 47.85 Mg 11.45 10.93 Al 25.44 21.89 Ca 0.37 0.22 Ti 3.79 1.84 Cr 0.95 0.43 Fe 0.82 0.34 Ni 2.05 0.81 Nb 16.11 4.01 total 100 100 Furthermore, such as Figure 5The figure shows the low-magnification microstructure of the high-temperature alloy ingot DB-2, Comparative Example 2. The figure clearly shows obvious "black spot" defect areas (circled in red). These defects, after low-magnification etching, appear as dark areas with significantly different color and structure from the matrix, and are typical dendritic segregation defects in high-temperature alloys.

[0084] Will Figure 5 Enlarging region A in the image yields... Figure 6 .like Figure 6 As shown, the defect area is not an isolated spot, but a continuous "segregation channel" (marked by yellow dashed lines) distributed along the dendrites; these channels are residual liquid phase regions enriched with solute elements during solidification, and are also the main locations for subsequent segregation phase precipitation.

[0085] Will Figure 6 The segregation channel B region was further magnified to obtain Figure 7 Then Figure 7 By magnifying region C, the characteristic structures within the channel (such as...) can be clearly observed. Figure 8 (As shown). The results indicate that γ+γ' eutectic phase and η phase are enriched and precipitated in the channel. This dendritic segregation and precipitation of harmful phases are one of the key metallurgical defects leading to the deterioration of ingot performance in the VIM+ESR+VAR triple process.

[0086] In summary, the dual-vacuum self-consuming arc remelting process proposed in this invention can stably prepare high-temperature alloy ingots free of metallurgical defects. It comprehensively outperforms the industry's conventional VIM+VAR dual-process and VIM+ESR+VAR triple-process in three core dimensions: metallurgical purity, compositional uniformity, and core service performance. The method for preparing metallurgically defect-free high-temperature alloy ingots using dual-vacuum self-consuming arc remelting proposed in this invention possesses excellent specification adaptability, consistently achieving superior comprehensive performance in ingots of Φ406mm (small), Φ508mm (medium), and Φ660mm (large), without exhibiting performance degradation issues due to increased ingot size. It has broad prospects for industrial application. The core logic behind its performance improvement lies in achieving deep degassing and significantly improving the uniformity of alloy element distribution through two vacuum self-consuming arc remelting processes. This fundamentally eliminates conventional metallurgical defects such as porosity, inclusions, and segregation, ultimately achieving a comprehensive leap in the overall performance of the ingot.

[0087] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0088] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing metallurgically defect-free high-temperature alloy ingots by dual-vacuum consumable arc melting, characterized in that, Includes the following steps: Step 1: Under vacuum conditions, Ni, Fe, Cr, Co, Mo and nickel-niobium master alloy are completely melted and then refined; after refining, the temperature is raised to the target temperature and Al and Ti are added. After the two are completely melted, the target temperature is maintained constant, and then nickel-boron master alloy and nickel-phosphorus master alloy are added; after alloying is completed, samples are taken for inspection. After the inspection is qualified, the consumable electrode is obtained by casting. Step 2: The consumable electrode is subjected to first-stage vacuum consumable arc melting at a first melting rate, and then to second-stage vacuum consumable arc melting at a second melting rate. At the end of the secondary vacuum self-consuming arc melting process, a gradually decreasing current method is used for hot sealing, ultimately producing a high-temperature alloy ingot without metallurgical defects.

2. The method for preparing metallurgically defect-free high-temperature alloy ingots by dual-vacuum consumable arc melting according to claim 1, characterized in that, In step 2, the vacuum degree of the first-stage vacuum self-consuming arc melting is ≤0.08 Pa, and the first melting rate is 2.7~5.3 kg / min.

3. The method for preparing metallurgically defect-free high-temperature alloy ingots by dual-vacuum consumable arc melting according to claim 2, characterized in that, During the first-stage vacuum self-consuming arc melting process, when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ406mm, the first melting rate is 2.7~2.9kg / min; when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ508mm, the first melting rate is 3.9~4.1kg / min; and when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ660mm, the first melting rate is 5.1~5.3 kg / min.

4. The method for preparing metallurgically defect-free high-temperature alloy ingots by dual-vacuum consumable arc melting according to claim 1, characterized in that, In step 2, the vacuum degree of the secondary vacuum self-consuming arc melting is ≤0.03 Pa, and the second melting rate is 2.1~3.9 kg / min.

5. The method for preparing metallurgically defect-free high-temperature alloy ingots by dual-vacuum consumable arc melting according to claim 4, characterized in that, During the secondary vacuum self-consuming arc melting process, when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ406mm, the second melting rate is 2.1~2.3kg / min; when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ508mm, the second melting rate is 2.9~3.1kg / min; and when the diameter of the high-temperature alloy ingot without metallurgical defects is Φ660mm, the second melting rate is 3.7~3.9kg / min.

6. The method for preparing metallurgically defect-free high-temperature alloy ingots by double vacuum consumable arc melting according to claim 1, characterized in that, In step 2, during the hot capping stage, the final hot capping current is 40% to 50% of the second steady-state melting current.

7. A high-temperature alloy ingot free of metallurgical defects, characterized in that, The ingot is prepared by the double vacuum self-consuming arc melting method according to any one of claims 1 to 6, and has an oxygen content ≤ 3.5 ppm, a nitrogen content ≤ 4.0 ppm, and a niobium element segregation ratio between dendrites and dendrite trunks ≤ 1.

20. The range of Al and Ti elements at the head and tail of the metallurgical defect-free high-temperature alloy ingot is ≤ 0.03%.

8. A method for preparing a high-temperature alloy ingot without metallurgical defects based on the dual vacuum consumable arc melting according to any one of claims 1 to 6, and the application of the high-temperature alloy ingot without metallurgical defects according to claim 7 in the core load-bearing rotating components of aero engines and gas turbines.

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