Low-segregation nickel-based superalloy, preparation method thereof and segregation defect control method

Abstract

The invention belongs to the field of high-temperature alloy manufacturing, and particularly discloses a low-segregation nickel-based high-temperature alloy, a preparation method of the low-segregation nickel-based high-temperature alloy and a segregation defect control method. The segregation defect control method comprises the steps that the melting speed of the nickel-based superalloy in the steady-state melting stage of vacuum consumable smelting is determined on the basis of the content of segregation-prone elements in the nickel-based superalloy; based on the determined melting speed of the steady-state melting stage, the filling ratio adopted for vacuum consumable smelting of the nickel-based superalloy is determined; and carrying out vacuum consumable smelting on the nickel-based superalloy according to the determined filling ratio and the determined melting speed in the steady-state smelting stage. According to the segregation defect control method, black spots, white spots and surface quality of the cast ingot in the nickel-based superalloy vacuum consumable smelting process can be effectively controlled.

Description

Technical Field

[0001] The present invention belongs to the field of high-temperature alloy manufacturing, and specifically relates to a method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloys, a method for preparing low-segregation nickel-based high-temperature alloys, and the low-segregation nickel-based high-temperature alloys prepared thereby. Background Art

[0002] High-temperature alloy refers to an alloy with iron, nickel and cobalt as the matrix that can be used under complex working stresses and long-term service above 600°C. This alloy has good comprehensive mechanical properties under high temperature conditions and is widely used in aerospace, petroleum, chemical and other fields.

[0003] Currently, some high-quality superalloys utilize vacuum consumable smelting as a secondary melting process. Numerous studies have demonstrated the significant impact of vacuum consumable smelting on the quality of superalloy products. Currently, white spots and black spots in consumable ingots are the primary issues encountered in vacuum consumable smelting of superalloys. Research has shown that black spots are a type of channel-type macrosegregation defect that significantly reduces the toughness, yield strength, and endurance properties of the material, leading to material scrap and severely limiting the development of superalloy varieties and properties. Furthermore, the formation of white spots can lead to differences in strengthening elements and precipitates between the white spots and the matrix. Compared to the matrix, the white spots contain fewer strengthening elements and grain boundary precipitates. Generally, the formation of white spots can severely impact the endurance creep and other properties of superalloy products. In production, if white spots are detected in superalloy products, severe cases will result in the product being scrapped. Therefore, mitigating or eliminating the occurrence of black spots and white spots during vacuum consumable smelting plays a vital role in the manufacturing and development of superalloys.

[0004] Previous studies have found that during vacuum consumable smelting, the formation of black spots is primarily determined by alloy composition and smelting parameters. For alloys containing high levels of segregating elements such as W, Mo, Al, and Ti, smelting parameters must be controlled to achieve a shallow, flat melt pool to avoid black spots. Regarding white spots, research has found that unmelted material from the crown of the ingot typically forms a defect. The crown is a layer of high-inclusion metal, formed at the top feeding end of a high-temperature alloy vacuum arc remelted ingot near the inner wall of the mold. These white spots are primarily influenced by factors such as the fill ratio and melting rate. Under certain ingot shapes, increasing the fill ratio significantly increases the electromagnetic force directed toward the ingot crown, increasing the likelihood of the crown tipping over, breaking off, and falling into the melt pool, which in turn increases the risk of white spots. However, under certain ingot shapes, increasing the melting rate makes it easier for fallen material from the crown to dissolve in the deeper melt pool, mitigating the formation of white spots. Furthermore, the filling ratio also affects the molten pool's edge-to-edge condition. Generally, increasing the filling ratio facilitates heat transfer from the molten pool to the side mold, resulting in better molten pool edge-to-edge condition, good ingot surface quality, less peeling, and a high yield rate. Currently, relevant technologies and inventions have conducted some research on improving the segregation problems of black spots and white spots in vacuum consumable ingots. However, the research work and the results achieved still have certain deficiencies. For example, the inherent optimization relationship between key parameters such as high-temperature alloy composition, melting rate, and filling ratio has not been clarified, resulting in an inability to effectively solve the problems of black spots, white spots, and poor surface quality in vacuum consumable smelting of high-temperature alloys.

[0005] In view of this, the existing high-temperature alloy preparation method needs to be improved. Summary of the Invention

[0006] The main purpose of the present invention is to address the deficiencies in the above-mentioned prior art and provide a method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloys and a method for preparing low-segregation nickel-based high-temperature alloys, aiming to avoid black spots while reducing white spot segregation defects during vacuum consumable smelting, and to prepare low-segregation nickel-based high-temperature alloy ingots.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: According to a first aspect of the present invention, a method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloys is provided, comprising the following steps: Determining the melting rate of the nickel-based superalloy in a steady-state melting stage of vacuum consumable smelting based on the content of segregation-prone elements in the nickel-based superalloy; Determining a filling ratio for vacuum consumable smelting of the nickel-based high-temperature alloy based on the determined melting rate in the steady-state melting stage; The nickel-based high-temperature alloy is subjected to vacuum consumable smelting according to the determined filling ratio and the determined melting rate in the steady-state smelting stage.

[0008] According to some embodiments of the present invention, the easily segregated element includes at least one of W, Mo, Al, and Ti.

[0009] According to some embodiments of the present invention, determining the melting rate of the nickel-based superalloy in a steady-state melting stage of vacuum consumable smelting based on the content of segregation-prone elements in the nickel-based superalloy includes: When the content of the easily segregated element is within the specified range, the melting rate in the steady-state melting stage is set to 3.0-3.4 kg / min; When the content of the segregation-prone element is lower than the specified range, the melting rate in the steady-state melting stage is set to 3.5-4.2 kg / min. The specified ranges are: W: 1.5-4.5%, Mo: 3.5-4.5%, Al: 1.0-2.5%, and Ti: 2.0-3.0%.

[0010] According to some embodiments of the present invention, determining the filling ratio used in the vacuum consumable smelting of the nickel-based high-temperature alloy based on the determined melting rate in the steady-state melting stage includes: When the melting rate in the steady-state melting stage is 3.0-3.4 kg / min, the filling ratio is set to 0.65-0.72; When the melting rate in the steady-state melting stage is 3.5-4.2 kg / min, the filling ratio is set to 0.73-0.80.

[0011] According to some embodiments of the present invention, determining the filling ratio used in the vacuum consumable smelting of the nickel-based high-temperature alloy based on the determined melting rate in the steady-state melting stage includes: When the melting rate in the steady-state melting stage is 3.0-3.4 kg / min, the filling ratio is determined based on the melting rate according to the following formula: y=0.175x+0.13, where y is the filling ratio and x is the melting rate; When the melting rate in the steady-state melting stage is 3.5-4.2 kg / min, the filling ratio is determined based on the melting rate according to the following formula: y=0.1x+0.38, where y is the filling ratio and x is the melting rate.

[0012] According to some embodiments of the present invention, vacuum consumable smelting of the nickel-based high-temperature alloy according to the determined filling ratio and the determined melting rate in the steady-state smelting stage includes: determining a diameter of the nickel-based high-temperature alloy consumable electrode based on the determined filling ratio; A consumable electrode of a required diameter is prepared and vacuum consumable smelting is performed using the consumable electrode to obtain a nickel-based high-temperature alloy consumable ingot.

[0013] According to some embodiments of the present invention, a consumable electrode of a desired diameter is prepared by controlling the size of the vacuum induction ingot and the amount of ingot stripping.

[0014] According to a second aspect of the present invention, a method for preparing a low-segregation nickel-based high-temperature alloy is provided, comprising the following steps: Preparation of nickel-based high-temperature alloy consumable electrodes; The nickel-based high-temperature alloy consumable electrode is used to perform vacuum consumable smelting to obtain a nickel-based high-temperature alloy consumable ingot. The melting rate in the steady-state melting stage of the vacuum consumable smelting is determined based on the content of easily segregated elements in the nickel-based high-temperature alloy, and the filling ratio adopted in the vacuum consumable smelting is determined based on the melting rate in the steady-state melting stage.

[0015] According to some embodiments of the present invention, in the arc starting stage of the vacuum consumable smelting, the current is controlled to 4.0~8.0kA, the voltage is controlled to 22.0~24.0V, and the inert gas pressure is controlled to 0Pa; in the steady-state melting stage of the vacuum consumable smelting, the melting rate is controlled to 3.0~4.2kg / min, the droplet is controlled to 3~10 1 / s, and the inert gas pressure gradually increases from 0Pa to 400~800Pa; in the hot capping stage of the vacuum consumable smelting, the melting rate is controlled to 1.5~4.0kg / min, and the droplet is controlled to 10~18 1 / s.

[0016] According to a third aspect of the present invention, there is provided a low-segregation nickel-based high-temperature alloy, which is prepared by the method described in the second aspect of the present invention.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects: The present invention provides a method for controlling segregation defects during vacuum consumable smelting of nickel-based superalloys. First, the melting rate is determined based on the alloy composition and segregation characteristics to prevent black spot defects caused by segregating elements during the smelting process. Furthermore, the filling ratio is determined based on the melting rate to reduce the formation of white spots during the smelting process, while also improving the surface quality of the ingots, reducing the amount of surface flaking, and increasing the yield rate. By optimizing the inherent relationship between key parameters such as the nickel-based superalloy composition, melting rate, and filling ratio, the present invention effectively controls black spots, white spots, and surface quality of the ingots during vacuum consumable smelting of nickel-based superalloys.

[0018] The method for preparing a low-segregation nickel-based superalloy provided by the present invention prevents the formation of black speckle defects caused by segregating elements during the smelting process by determining the melting rate during the steady-state smelting phase of vacuum consumable smelting based on the content of segregating elements in the nickel-based superalloy. Furthermore, the filling ratio used in vacuum consumable smelting is determined based on the melting rate during the steady-state smelting phase, thereby reducing the formation of white spots during the smelting process. While effectively addressing white spots and black spots, the method can also improve the surface quality of the ingot, reduce the amount of ingot peeling, and produce ingots of high quality and high yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of the method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloys provided by the present invention.

[0020] Figure 2 The present invention provides a flow chart of the method for preparing a low-segregation nickel-based high-temperature alloy.

[0021] Figure 3 Figure 2 is the molten pool depth diagram at different melting rates.

[0022] Figure 4 These are low-magnification scanning electron microscope photos of nickel-based high-temperature alloy consumable ingots prepared in some embodiments and comparative examples.

[0023] Figure 5 The following are photos of consumable ingots of nickel-based high-temperature alloys prepared in some embodiments and comparative examples. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] As required, specific embodiments of the present invention are disclosed in this specification; however, it should be understood that the disclosed embodiments are merely illustrative of the invention, which may be implemented in various alternative forms. In the following description, various operating parameters and components are described in connection with various contemplated embodiments. These specific parameters and components are provided herein as examples only and are not intended to be limiting.

[0026] As mentioned in the background technology section, existing studies have found that in the vacuum consumable smelting process, black spots mainly depend on the alloy composition, smelting parameters, etc. For alloys with high contents of easily segregated elements such as W, Mo, Al, and Ti, it is necessary to control the smelting parameters to obtain a shallow and flat molten pool to avoid the formation of black spots. Studies have also found that typical white spot defects will be produced by the unmelted falling of the ingot crown. This type of white spot defect is mainly affected by factors such as the filling ratio and the melting rate. Under a certain ingot shape, generally with the increase of the filling ratio, the electromagnetic force directed to the inside of the molten pool on the ingot crown increases significantly, increasing the incidence of the ingot crown falling over and breaking and falling into the molten pool, which will increase the formation of white spots. However, under a certain ingot shape, with the increase of the melting rate, the falling objects of the ingot crown are more likely to dissolve in a deeper molten pool, which can reduce the formation of white spots. Not only that, the filling ratio also affects the molten pool to the edge. Generally, increasing the filling ratio is conducive to heat transfer from the molten pool to the side crystallizer, and the molten pool to the edge is better, resulting in good ingot surface quality, less peeling, and high yield. In view of this, the present invention establishes different melting rate ranges based on the nickel-based alloy composition and segregation tendency. Based on the influence of melting rate and filling ratio on white spots and surface quality of the ingot, a smelting process based on different alloy grades is determined, combining composition, melting rate, and filling ratio. This effectively controls black spots, white spots, and surface quality of the ingot during the consumable smelting process. In actual production, given a given ingot shape, different grades of high-temperature alloys have different compositions and segregation tendencies, resulting in different melting rate ranges. Therefore, it is necessary to establish an appropriate filling ratio range to mitigate the occurrence of white spots and black spots while achieving high-quality surface quality in high-temperature alloy ingots.

[0027] According to a first aspect of the present invention, a method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloys is provided. Figure 1 As shown, the segregation defect control method includes the following steps: S1: determining the melting rate of the nickel-based superalloy during the steady-state melting stage of vacuum consumable smelting based on the content of segregating elements in the nickel-based superalloy; S2: determining the filling ratio used in the vacuum consumable smelting of the nickel-based superalloy based on the determined melting rate during the steady-state melting stage; S3: performing vacuum consumable smelting on the nickel-based superalloy according to the determined filling ratio and the determined melting rate during the steady-state melting stage. The segregation defect control method provided by the present invention first determines the smelting melting rate based on the alloy composition and segregation characteristics to avoid the formation of black spot defects caused by segregating elements during the smelting process; based on this, the filling ratio is determined based on the melting rate to reduce the generation of white spots during the smelting process, while improving the surface quality of the ingot, reducing the amount of surface flaking of the ingot, and improving the yield rate. The segregation defect control method provided by the present invention can effectively control black spots, white spots, and surface quality of the ingot during the vacuum consumable smelting process of the nickel-based superalloy by optimizing the internal relationship between key parameters such as the nickel-based superalloy composition, melting rate, and filling ratio.

[0028] The "filling ratio used in vacuum consumable metallurgy" mentioned in this article refers to the ratio of the consumable electrode area to the mold area used in vacuum consumable metallurgy. The filling ratio has a significant impact on the solidification quality of the ingot.

[0029] In some embodiments, the easily segregated element in the nickel-based superalloy includes at least one of W, Mo, Al, and Ti. Specifically, the nickel-based superalloy may contain only one of W, Mo, Al, and Ti, or only two or three of them, or all of them.

[0030] In some embodiments, in step S1, based on the content of easily segregated elements in the nickel-based high-temperature alloy, the melting rate of the nickel-based high-temperature alloy in the steady-state melting stage of vacuum consumable smelting is determined, including: when the content of easily segregated elements is in a specified range, the melting rate in the steady-state melting stage is set to 3.0~3.4kg / min; when the content of easily segregated elements is lower than the specified range, the melting rate in the steady-state melting stage is set to 3.5~4.2kg / min, wherein the specified range is: W: 1.5~4.5%, Mo: 3.5~4.5%, Al: 1.0~2.5%, Ti: 2.0~3.0%. In the present invention, based on the segregation characteristics of nickel-based high-temperature alloy components, for alloys with a high content of elements prone to segregation, a low melting rate range (3.0-3.4 kg / min) is formulated to effectively avoid the typical defects of black spots during the smelting process; for alloys with a low content of elements prone to segregation, a high melting rate range (3.5-4.2 kg / min) is formulated to shorten the smelting cycle and reduce production costs in order to improve production efficiency.

[0031] In some embodiments, in step S2, based on the determined melting rate in the steady-state melting stage, a filling ratio for vacuum consumable smelting of a nickel-based high-temperature alloy is determined, including: when the melting rate in the steady-state melting stage is 3.0-3.4 kg / min, the filling ratio is set to 0.65-0.72; when the melting rate in the steady-state melting stage is 3.5-4.2 kg / min, the filling ratio is set to 0.73-0.80. In the present invention, for the low melting rate operating range (3.0-3.4 kg / min), a small filling ratio range (0.65-0.72) is adopted to prevent the ingot crown from being subjected to a large electromagnetic force directed into the molten pool during the smelting process, causing the ingot crown to fall and break, and fall into a shallow molten pool (low melting rate, shallow and flat molten pool), where it is difficult to be completely ablated, resulting in white spot defects. When the filling ratio exceeds the above range, if the filling ratio is too large, the ingot will be subjected to greater inward electromagnetic forces, which will easily cause it to fall over and break, and increase the probability of white spot formation. If the filling ratio is too small, the melt pool edge condition and the ingot surface quality will be poor, the amount of peeling will be large, and the yield rate will be low. For the high melting rate range (3.5-4.2kg / min), a large filling ratio range (0.73-0.80) is adopted. On the one hand, although the ingot crown is subjected to greater electromagnetic forces directed into the melt pool, which may cause it to fall over and break, it will be completely dissolved when it falls into the deep melt pool (high melting rate, deep V-shaped melt pool), which can avoid the formation of white spots. On the other hand, the large filling ratio facilitates heat transfer from the melt pool to the side mold and helium, improving the melt pool edge condition and the ingot surface quality, which helps reduce the amount of peeling and improve the yield rate. If the fill ratio exceeds the above range, a larger fill ratio will affect arc safety. If the fill ratio is too small, the molten pool will transfer less heat to the side mold and helium, resulting in poor molten pool edge coverage, making it difficult to improve the surface quality of the ingot and reduce the amount of surface flaking. Furthermore, a smaller fill ratio will result in a deeper molten pool, which is more likely to cause black spot defects.

[0032] In some embodiments, in step S3, based on the determined melting rate in the steady-state melting stage, the filling ratio adopted in the vacuum consumable smelting of the nickel-based high-temperature alloy is determined, including: when the melting rate in the steady-state melting stage is 3.0~3.4kg / min, the filling ratio is determined based on the melting rate according to the following formula: y=0.175x+0.13, wherein y is the filling ratio and x is the melting rate; when the melting rate in the steady-state melting stage is 3.5~4.2kg / min, the filling ratio is determined based on the melting rate according to the following formula: y=0.1x+0.38, wherein y is the filling ratio and x is the melting rate.

[0033] In some embodiments, in step S3, vacuum consumable smelting is performed on the nickel-based high-temperature alloy according to the determined filling ratio and the determined melting rate in the steady-state smelting stage, including: determining the diameter of the nickel-based high-temperature alloy consumable electrode based on the determined filling ratio; preparing a consumable electrode of the required diameter and using the consumable electrode to perform vacuum consumable smelting to obtain a nickel-based high-temperature alloy consumable ingot.

[0034] In some embodiments, a consumable electrode of a desired diameter is prepared by controlling the size of the vacuum induction ingot and the amount of ingot peeling.

[0035] According to a second aspect of the present invention, a method for preparing a low-segregation nickel-based high-temperature alloy is provided, such as Figure 2 As shown, the preparation method includes the following steps: S10: preparing a nickel-based superalloy consumable electrode; S20: using the nickel-based superalloy consumable electrode to perform vacuum consumable smelting to obtain a nickel-based superalloy consumable ingot. The melting rate in the steady-state smelting stage of the vacuum consumable smelting is determined based on the content of easily segregated elements in the nickel-based superalloy, and the filling ratio used in the vacuum consumable smelting is determined based on the melting rate in the steady-state smelting stage. The preparation method of the low-segregation nickel-based superalloy provided by the present invention can avoid the formation of black spot defects caused by easily segregated elements during the smelting process by determining the melting rate in the steady-state smelting stage of the vacuum consumable smelting based on the content of easily segregated elements in the nickel-based superalloy; and can reduce the generation of white spots during the smelting process by determining the filling ratio used in the vacuum consumable smelting based on the melting rate in the steady-state smelting stage. The preparation method of the present invention can effectively solve the problems of white spots and black spots while improving the surface quality of the ingot, reducing the amount of ingot peeling, and producing ingots with high quality and high yield.

[0036] The production of consumable electrodes mainly involves several steps: vacuum induction ingot preparation, annealing, sawing, peeling, baking, and welding. Among these steps, the most important is to control the size of the vacuum induction ingot and the amount of peeling to control the diameter, i.e., area, of the consumable electrode, and thus the smelting filling ratio.

[0037] Vacuum consumable smelting includes the arc starting stage, steady-state melting stage and hot capping stage. Among them, the arc starting stage and hot capping stage are unstable smelting stages, and the corresponding ingot bottom and head must be cut off. The steady-state melting stage plays an important role in the ingot quality. Therefore, the smelting melting rate focused on in this technology is the melting rate in the steady-state melting stage.

[0038] In some embodiments, during the arc starting stage of vacuum consumable smelting, the current is controlled to be 4.0~8.0kA, the voltage is controlled to be 22.0~24.0V, and the inert gas pressure is controlled to be 0Pa; during the steady-state melting stage of vacuum consumable smelting, the melting rate is controlled to be 3.0~4.2kg / min, the droplet is controlled to be 3~10 1 / s, and the inert gas pressure gradually increases from 0Pa to 400~800Pa; during the hot capping stage of vacuum consumable smelting, the melting rate is controlled to be 1.5~4.0kg / min, and the droplet is controlled to be 10~18 1 / s.

[0039] In some embodiments, in step S20, using a nickel-based high-temperature alloy consumable electrode to perform vacuum consumable smelting to obtain a nickel-based high-temperature alloy consumable ingot includes: placing the consumable electrode in a consumable furnace, closing the furnace door, and starting to evacuate. When the vacuum degree and the leakage rate meet the requirements, that is, the vacuum degree is <0.10Pa and the leakage rate is <0.10Pa / min, power can be supplied to start melting and enter the arc starting stage; the arc starting stage adopts current + voltage control, the current is 4.0~8.0kA, the voltage is 22.0~24.0V, and the inert gas pressure during the arc starting period is 0Pa; the steady-state melting stage adopts droplet + melting rate control, the melting rate is 3.0~4.2kg / min, and the droplet is 3~10 1 / s. The inert gas pressure during the steady-state melting stage gradually increases from 0 Pa to the inert gas pressure used in the steady-state stage, with a pressure range of 400 Pa to 800 Pa. The hot capping stage adopts droplet + melt rate control, with a melt rate of 1.5 to 4.0 kg / min and a drop rate of 10 to 18 1 / s. The melt rate and inert gas pressure during the hot capping stage gradually decrease from the steady-state stage values ​​and then remain stable. The inert gas mentioned in the present invention can be helium.

[0040] The present invention formulates a control order for black spots, white spots and surface quality of ingots based on the influence of key parameters such as alloy composition, melting rate and filling ratio on white spots, black spots and surface quality of consumable ingots. First, a smelting melting rate range is formulated based on the alloy composition and segregation characteristics to avoid the formation of black spot defects in the alloy that is prone to segregation during the smelting process. On this basis, different filling ratio ranges are formulated based on the influence of the molten pool depth and filling ratio under different smelting melting rate ranges on white spots and surface quality of ingots to reduce the generation of white spots during the smelting process, while improving the surface quality of ingots, reducing the amount of ingot surface peeling and improving the yield rate. By optimizing the intrinsic relationship between key parameters such as nickel-based high-temperature alloy composition, melting rate, filling ratio, etc., the black spots, white spots and surface quality problems of nickel-based high-temperature alloy vacuum consumable ingots can be effectively controlled, and high-quality high-temperature alloy products can be produced.

[0041] According to a third aspect of the present invention, there is provided a low-segregation nickel-based high-temperature alloy, which is prepared by the method described in the second aspect of the present invention.

[0042] The present invention will be further described below with reference to specific examples, but the present invention is not limited thereto in any way. To avoid redundancy, the methods used are conventional methods unless otherwise specified.

[0043] Example 1: 1) The nickel-based superalloy used has a chemical composition of C ≤ 0.08, Cr: 17-20%, W: 4-5%, Mo: 4-5%, Al: 1-1.5%, Ti: 2.2-2.8%, with the remainder being Ni and some unavoidable impurities. The consumable electrode rods are produced through a process consisting of vacuum induction smelting, pouring, annealing, sawing, peeling, baking, and welding. The induction ingots obtained during the induction ingot pouring process have a diameter of 440 mm, and the electrode rods are 424 mm in diameter after peeling. A smelting fill ratio of 0.7 is used.

[0044] 2) Place the electrode rod from step 1) as a consumable electrode into a Φ508mm ingot-shaped consumable furnace. Close the furnace door and begin evacuating. Once the vacuum and leak rate meet the requirements (i.e., vacuum <0.1Pa and leak rate <0.1Pa / min), power can be supplied to begin smelting. The arc starting phase of the consumable smelting process lasts from 0 to 20 minutes. Current + voltage control is used during this phase. During this phase, the current gradually increases from 4.5kA to 7.5kA before stabilizing, and the voltage gradually increases from 22V to 24V before stabilizing. The helium pressure during this phase is 0Pa.

[0045] 3) The time from 21 to 720 minutes is the steady-state melting stage of consumable smelting. In the steady-state melting stage, the droplet + melting rate control is adopted. The number of droplets is 7.0 1 / s and the melting rate is 3.4 kg / min. Helium is filled when the smelting time reaches 100 minutes. When the smelting time reaches 150 minutes, the helium pressure increases to 500 Pa and then stabilizes.

[0046] 4) The hot capping stage of the consumable smelting process lasts from 721 to 800 minutes. This stage utilizes droplet and melt rate control, with a droplet count of 11 to 16 1 / s and a melt rate of 1.5 to 3.4 kg / min. The early stage of the hot capping process lasts from 721 to 750 minutes, during which the melt rate is gradually reduced from 3.4 kg / min to 1.8 kg / min, and the helium pressure is reduced from 500 Pa to 350 Pa. The late stage of the hot capping process lasts from 751 to 800 minutes, a low-melting-rate, heat-insulating smelting phase (50 minutes). During this phase, the melt rate is gradually reduced from 1.8 kg / min to 1.5 kg / min, and the helium pressure is maintained at 350 Pa.

[0047] 5) After the hot capping is completed, the ingot is cooled in the crystallizer for 120 minutes and then removed from the mold. After air cooling, a consumable ingot is obtained.

[0048] Example 2: The only difference from Example 1 is that by controlling the size of the vacuum induction ingot and the amount of ingot stripping, an electrode rod with a diameter of 410 mm was produced, using a filling ratio of 0.65. In this case, the metal pool depth is smaller, the inward electromagnetic force on the ingot crown is smaller, and no black or white spots appear.

[0049] Example 3: The only difference from Example 1 is that by controlling the size of the vacuum induction ingot and the amount of ingot peeling, an electrode rod with a diameter of 430 mm was prepared, and a filling ratio of 0.72 was used. In this case, no white or black spots appeared in the molten pool, and the surface quality of the ingot was good.

[0050] Example 4: The only difference from Example 1 is that the melting rate during the steady-state melting stage of the consumable smelting process is 3.0 kg / min. In this case, no white spots or black spots appear in the molten pool.

[0051] Example 5: The only differences from Example 1 are: (1) the chemical composition of the nickel-based high-temperature alloy used is: C ≤ 0.08, Cr: 17-21%, Ni: 50-55%, Co ≤ 1%, Mo: 2.8-3.3%, Al: 0.2-0.8%, Ti: 0.65-1.15%, Nb: 4.75-5.5%, with the remainder being Fe and unavoidable impurities. (2) the melting rate during the steady-state melting stage of the consumable smelting process is 3.9 kg / min; (3) the electrode rod used has a diameter of 440 mm and a filling ratio of 0.75. In this case, the ingot does not show any black or white spots, and the surface quality is good.

[0052] Example 6: The only difference from Example 5 is that by controlling the size of the vacuum induction ingot and the amount of ingot peeling, an electrode rod with a diameter of 433 mm was produced, and a filling ratio of 0.73 was used. In this case, the ingot had no white spots or black spots and had good surface quality.

[0053] Example 7: The only difference from Example 5 is that by controlling the size of the vacuum induction ingot and the amount of ingot peeling, an electrode rod with a diameter of Φ454 mm was produced, and a filling ratio of 0.8 was used. In this case, the ingot had no white spots or black spots and had good surface quality.

[0054] Example 8: The only difference from Example 5 is that the melting rate during the steady-state melting stage of the consumable smelting process is 3.5 kg / min. In this case, no white spots or black spots appear in the molten pool.

[0055] Example 9: The only difference from Example 5 is that the melting rate during the steady-state melting stage of the consumable smelting process is 4.2 kg / min. In this case, no white spots or black spots appear in the molten pool, and the surface quality of the ingot is good.

[0056] Comparative Example 1: The only difference from Example 1 is that by controlling the size of the vacuum induction ingot and the amount of ingot peeling, an electrode rod with a diameter of Φ406 mm was prepared, and a filling ratio of 0.64 was used. In this case, the surface quality of the ingot was poor.

[0057] Comparative Example 2: The only difference from Example 1 is that by controlling the size of the vacuum induction ingot and the amount of ingot peeling, an electrode rod with a diameter of 433 mm was prepared, and a filling ratio of 0.73 was used. In this case, the ingot crown was subjected to a strong inward electromagnetic force, causing it to fall over and break. The broken ingot crown fell into the shallow metal molten pool, making it difficult to completely melt, resulting in white spots.

[0058] Comparative Example 3: The only difference from Example 1 is that the melting rate in the steady-state melting stage is 2.9 kg / min, that is, a lower melting rate is used for smelting. In this case, the molten pool does not reach the edge during the smelting process, the surface quality of the ingot is poor, and the amount of ingot peeling is large.

[0059] Comparative Example 4: The only difference from Example 1 is that the melting rate in the steady-state melting stage is 3.5 kg / min, that is, a higher melting rate is used for smelting. In this case, the smelting pool depth and the mushy zone are large, the local solidification time of the alloy is long, and black spot defects appear in the ingot.

[0060] Comparative Example 5: The only difference from Example 5 is that by controlling the size of the vacuum induction ingot and the amount of ingot peeling, an electrode rod with a diameter of Φ400 mm was prepared, and the filling ratio used was 0.72. In this case, the surface quality of the ingot was poor.

[0061] Comparative Example 6: The only difference from Example 5 is that by controlling the size of the vacuum induction ingot and the amount of ingot peeling, an electrode rod with a diameter of Φ456 mm is prepared, and a filling ratio of 0.81 is used. In this case, the arc safety is poor.

[0062] Comparative Example 7: The only difference from Example 5 is that the melting rate in the steady-state smelting stage is 3.4 kg / min, that is, a smaller melting rate is used for smelting. In this case, the molten pool during the smelting process is shallow and flat, and the ingot crown falls into the molten pool and is difficult to be completely melted, forming white spots.

[0063] The present invention first uses Meltflow to analyze the effect of melting rate on molten pool depth and white spot dissolution. Figure 3 As shown in the results, it was found that increasing the melting rate and increasing the molten pool depth are beneficial to the dissolution of white spots. Then the influence of the filling ratio on the depth of the metal molten pool and the extent to which the molten pool extends to the edge was analyzed. As shown in Table 1, with the increase of the filling ratio, the thickness of the mushy area at the edge of the molten pool gradually decreased, and the molten pool to the edge and the surface quality were better. In addition, by consulting relevant literature, the influence of the filling ratio on the electromagnetic force on the ingot crown was clarified. It was found that with the increase of the filling ratio, the electromagnetic force on the ingot crown increased, and the risk of white spots increased. According to the influence of the melting rate and filling ratio on white spots and black spots, a reasonable range of alloy composition, smelting melting rate and filling ratio was formulated, which effectively reduced the black spots and white spots on the ingot and improved the surface quality of the ingot.

[0064] Table 1 Thickness of mushy zone at the edge of molten pool under different filling ratios

[0065] At the same time, the low-magnification and surface peeling conditions of some nickel-based high-temperature alloys prepared in the examples and comparative examples were obtained at the production site, such as Figure 4 As shown in the figure, the ingot of Example 1 has no black spots or white spots at low magnification, while the white spots appear in Comparative Example 2. Figure 5 As can be seen, Example 1 has good surface quality, with a surface peeling amount of 10 mm, while the surface quality of the ingot in Comparative Example 1 is poor, with a surface peeling amount of 15 mm. The above results show that the technical solution proposed by the present invention can effectively control white spots, black spots and surface quality of consumable smelting ingots, and produce high-quality high-temperature alloy products.

[0066] Finally, it should be noted that the embodiments described above are only some of the embodiments of the present invention, not all of them. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloys, characterized in that: The following steps are involved: Determining the melting rate of the nickel-based high-temperature alloy in a steady-state melting stage of vacuum consumable smelting based on the content of segregation-prone elements in the nickel-based high-temperature alloy; Determining a filling ratio used in vacuum consumable smelting of the nickel-based high-temperature alloy based on the determined melting rate in the steady-state melting stage; According to the determined filling ratio and the determined melting rate in the steady-state melting stage, the nickel-based high-temperature alloy is subjected to vacuum consumable smelting.

2. The method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloy according to claim 1, characterized in that: The easily segregated element includes at least one of W, Mo, Al and Ti.

3. The method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloy according to claim 2, characterized in that: Based on the content of segregation-prone elements in the nickel-based high-temperature alloy, the melting rate of the nickel-based high-temperature alloy in the steady-state melting stage of vacuum consumable smelting is determined, including: When the content of the segregation-prone element is within the specified range, the melting rate in the steady-state melting stage is set to 3.0-3.4 kg / min; When the content of the segregation-prone element is lower than the specified range, the melting rate in the steady-state melting stage is set to 3.5-4.2 kg / min. Wherein, the specified range is: W: 1.5~4.5%, Mo: 3.5~4.5%, Al: 1.0~2.5%, Ti: 2.0~3.0%.

4. The method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloy according to claim 3, characterized in that: Based on the determined melting rate in the steady-state melting stage, the filling ratio used in the vacuum consumable smelting of the nickel-based high-temperature alloy is determined, including: When the melting rate in the steady-state melting stage is 3.0-3.4 kg / min, the filling ratio is set to 0.65-0.72; When the melting rate in the steady-state melting stage is 3.5-4.2 kg / min, the filling ratio is set to 0.73-0.

80.

5. The method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloy according to claim 3, characterized in that: Based on the determined melting rate in the steady-state melting stage, the filling ratio used in the vacuum consumable smelting of the nickel-based high-temperature alloy is determined, including: When the melting rate in the steady-state melting stage is 3.0-3.4 kg / min, the filling ratio is determined based on the melting rate according to the following formula: y=0.175x+0.13, wherein y is the filling ratio and x is the melting rate; When the melting rate in the steady-state melting stage is 3.5-4.2 kg / min, the filling ratio is determined based on the melting rate according to the following formula: y=0.1x+0.38, wherein y is the filling ratio and x is the melting rate.

6. The method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloy according to claim 1, characterized in that: According to the determined filling ratio and the determined melting rate in the steady-state melting stage, the nickel-based high-temperature alloy is subjected to vacuum consumable smelting, including: determining a diameter of a nickel-based high-temperature alloy consumable electrode based on the determined filling ratio; A consumable electrode of a required diameter is prepared and vacuum consumable smelting is performed using the consumable electrode to obtain a nickel-based high-temperature alloy consumable ingot.

7. The method for controlling segregation defects in vacuum consumable smelting of nickel-based high-temperature alloy according to claim 6, characterized in that: The consumable electrode with the required diameter can be prepared by controlling the size of the vacuum induction ingot and the amount of ingot peeling.

8. A method for preparing a low-segregation nickel-based high-temperature alloy, characterized in that: The following steps are involved: Preparation of nickel-based high-temperature alloy consumable electrodes; The nickel-based high-temperature alloy consumable electrode is used to perform vacuum consumable smelting to obtain a nickel-based high-temperature alloy consumable ingot. The melting rate in the steady-state melting stage of the vacuum consumable smelting is determined based on the content of the easily segregated elements in the nickel-based high-temperature alloy, and the filling ratio used in the vacuum consumable smelting is determined based on the melting rate in the steady-state melting stage.

9. The method for preparing a low-segregation nickel-based high-temperature alloy according to claim 8, characterized in that: In the arc starting stage of the vacuum consumable smelting, the current is controlled to be 4.0~8.0kA, the voltage is controlled to be 22.0~24.0V, and the inert gas pressure is controlled to be 0Pa; in the steady-state smelting stage of the vacuum consumable smelting, the melting rate is controlled to be 3.0~4.2kg / min, the molten droplet is controlled to be 3~101 / s, and the inert gas pressure gradually increases from 0Pa to 400~800Pa; in the hot capping stage of the vacuum consumable smelting, the melting rate is controlled to be 1.5~4.0kg / min, and the molten droplet is controlled to be 10~18 1 / s.

10. A low-segregation nickel-based high-temperature alloy, characterized in that: The method is prepared by any one of claims 8 to 9.

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