A superalloy low-segregation ingot and its preparation method

Abstract

The present invention discloses a superalloy ingot with low segregation and a preparation method thereof, belonging to the technical field of difficult-to-deform superalloys, and solving the problems of large segregation degree and poor uniformity of existing superalloy ingots. The preparation method of the present invention includes the following steps: melting to obtain alloy liquid; pouring the alloy liquid into an ingot mold, applying pulsed electromagnetic treatment to the alloy liquid after the pouring starts, continuing to apply pulsed electromagnetic after the pouring process is completed, closing the pulsed electromagnetic after 60-100 s to obtain an ingot; performing homogenization treatment on the ingot to obtain a superalloy ingot with low segregation. The ingot prepared by the method of the present invention has small segregation, fine grain size and good tissue uniformity.

Description

Technical Field

[0001] The present invention relates to the technical field of superalloys, and particularly to a superalloy ingot with low segregation and a preparation method thereof. Background Art

[0002] Superalloy turbine disks are core components for manufacturing engines and gas turbines, and their metallurgical quality plays a decisive role in the reliability, service life, and performance of engines and gas turbines. As the primary step in the smelting of wrought superalloys, if there is severe segregation of alloying elements such as Ti and Mo in vacuum induction ingots, it deteriorates the metallurgical quality and hot working plasticity of the ingots, becoming the main obstacle restricting the preparation of high-alloy superalloy turbine disks.

[0003] Superalloys have high contents of alloying elements such as Ti and Mo. During the induction melting process, it is difficult to evenly distribute solute elements through existing technologies, resulting in severe segregation of the ingots, which brings difficulties to the subsequent smelting and hot working of the ingots. Moreover, there is a large columnar crystal structure in the induction ingots, further deteriorating the hot working plasticity of the ingots. Therefore, how to reduce the segregation of superalloys and improve the uniformity of superalloy ingots has become an urgent problem to be solved. Summary of the Invention

[0004] In view of the above situation, the present invention aims to provide a superalloy ingot with low segregation and a preparation method thereof, which is used to solve at least one of the following technical problems: the existing superalloy ingots have a large degree of segregation and poor uniformity.

[0005] The object of the present invention is mainly achieved through the following technical solutions:

[0006] The present invention provides a preparation method for a superalloy ingot with low segregation, including the following steps:

[0007] Step 1, melting to obtain an alloy liquid;

[0008] Step 2, pouring the alloy liquid into an ingot mold. After the pouring starts, apply pulsed electromagnetic treatment to the alloy liquid. After the pouring process is completed, continue to apply pulsed electromagnetic for 60 - 100 s, and then turn off the pulsed electromagnetic to obtain an ingot;

[0009] Step 3, performing homogenization treatment on the ingot to obtain a superalloy ingot with low segregation.

[0010] Further, in Step 2, before pouring, preheat the ingot mold through a heating furnace, and the preheating temperature is 400 - 600 °C.

[0011] Further, in Step 2, the waveform of the pulsed electromagnetic is a rectangular wave.

[0012] Further, in step 2, the current I of the pulsed electromagnetic field and the ingot diameter d satisfy the following relationship: I = kd, where the value range of k is 0.6 - 1, the unit of I is A, and the unit of d is mm.

[0013] Further, in step 2, when the ingot diameter d is 100 - 120 mm, the current I of the pulsed electromagnetic field is 60 - 80 A; when the ingot diameter d is 150 - 170 mm, the current I of the pulsed electromagnetic field is 100 - 150 A; when the ingot diameter d is 200 - 220 mm, the current I of the pulsed electromagnetic field is 160 - 200 A.

[0014] Further, in step 2, the duty cycle of the current of the pulsed electromagnetic field is 20% - 40%.

[0015] Further, in step 3, the homogenization treatment includes the following steps:

[0016] S301: Keep the ingot at a temperature of 650 - 750 °C for heat preservation;

[0017] S302: Raise the temperature to 1000 - 1020 °C and keep it for heat preservation;

[0018] S303: Raise the temperature to 1150 - 1170 °C and keep it for heat preservation;

[0019] S304: Raise the temperature to 1200 - 1220 °C and keep it for heat preservation;

[0020] S305: Lower the temperature to 950 - 1050 °C and keep it for heat preservation; After taking out of the furnace, air-cool to room temperature.

[0021] Further, in step 3, the heat preservation time T1 in S301, the heat preservation time T2 in S302, the heat preservation time T3 in S303, and the heat preservation time T4 in S304 satisfy the following relationship: T1 < T2, T3 < T4.

[0022] Further, in step 3, the heating rate V1 in S302, the heating rate V2 in S303, and the heating rate V3 in S304 satisfy the following relationship: V1 > V2 > V3.

[0023] The present invention also provides a superalloy ingot with low segregation, which is prepared by the above preparation method.

[0024] Compared with the prior art, the present invention can at least achieve one of the following beneficial effects:

[0025] a) In the method for preparing a superalloy ingot with low segregation of the present invention, after pouring starts, pulsed electromagnetic treatment is applied to the molten alloy. Under the action of the electromagnetic field, the solute fluidity at the front of the solidification interface increases, solute elements can be fully mixed, the segregation degree of the ingot is significantly reduced, and at the same time, the segregation behavior of carbides is inhibited, improving the alloy composition uniformity. Moreover, during pulsed magnetic field treatment, convective motion occurs inside the alloy melt, and the crystal nuclei on the mold wall fall off and become free, increasing the number of crystal nuclei in the alloy, promoting the formation of a large number of equiaxed crystals in the ingot, significantly refining the ingot structure, suppressing columnar crystals, and also reducing the segregation of alloy elements in the ingot. The number of crystal nuclei formed in the superalloy melt increases, the grain size of the ingot decreases, and the mechanical properties and hot plasticity are improved. Finally, through high-temperature homogenization treatment, the segregation of alloy elements in the ingot is basically eliminated, obtaining a superalloy ingot with low segregation, significantly improving the hot working plasticity of the ingot.

[0026] b) The ingot prepared by the method of the present invention can be directly used for cogging forging without going through the electroslag remelting process and the vacuum consumable process, significantly reducing the preparation cost of the ingot.

[0027] c) The superalloy ingot with low segregation of the present invention has small segregation, no carbide segregation phenomenon, fine grain size, good tissue uniformity, and excellent toughness and plasticity. For example, the element segregation coefficients at the center of the ingot are as follows: Ti: 1.09 - 1.15, Mo: 1.00 - 1.03, Cr: 0.98 - 1.00, Co: 0.96 - 1.00; the element segregation coefficients at the edge of the ingot are as follows: Ti: 1.04 - 1.10, Mo: 1.02 - 1.11, Cr: 0.98 - 1.00, Co: 0.98 - 1.00; the grain size of the ingot is about 120 - 160 μm, and the grains are fine. The hardness fluctuation from the center to the edge of the ingot is small. For example, the hardness difference from the center to the edge of the ingot is below 3 HRC.

[0028] d) The room-temperature tensile strength of the superalloy ingot with low segregation of the present invention is above 680 MPa (for example, 681 - 700 MPa), the yield strength is above 440 MPa (for example, 442 - 460 MPa), the elongation after fracture is above 20% (for example, 20.5% - 23.5%), and the reduction of area is above 40% (for example, 42% - 49%); the properties of the ingot at 650 °C are as follows: the tensile strength is above 590 MPa (for example, 597 - 620 MPa), the yield strength is above 350 MPa (for example, 350 - 370 MPa), the elongation after fracture is above 26% (for example, 26.5% - 29%), and the reduction of area is above 32% (for example, 32% - 35%).

[0029] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention may be realized and attained by the content particularly pointed out in the written description and the drawings. Description of the Drawings

[0030] The drawings are only for the purpose of illustrating specific embodiments, and are not considered as a limitation to the present invention. Throughout the drawings, the same reference signs denote the same components.

[0031] Figure 1 It is the macrostructure diagram of the ingot in Example 1;

[0032] Figure 2 It is the macrostructure diagram of the ingot in Comparative Example 1;

[0033] Figure 3 It is the carbide morphology diagram of the ingot in Example 1;

[0034] Figure 4 It is the carbide morphology diagram of the ingot in Comparative Example 1. Detailed Embodiments

[0035] The following will specifically describe the preferred embodiments of the present invention in conjunction with the drawings, wherein the drawings form a part of the present invention and are used together with the embodiments of the present invention to explain the principle of the present invention.

[0036] The present invention provides a method for preparing a high-temperature alloy low-segregation ingot, comprising the following steps:

[0037] Step 1, melting to obtain an alloy liquid;

[0038] Step 2, pouring the alloy liquid, applying pulsed electromagnetic treatment to the alloy liquid after the pouring starts, continuing to apply pulsed electromagnetic after the pouring process is completed, and turning off the pulsed electromagnetic after a certain time to obtain an ingot;

[0039] Step 3, performing homogenization treatment on the ingot to obtain a high-temperature alloy low-segregation ingot.

[0040] Specifically, in the above step 1, induction furnace is used for melting. Considering that when the melting temperature is lower than 1500 °C, it is difficult for the raw materials of high-temperature alloy to be completely melted and the composition is uneven; when the melting temperature is higher than 1600 °C, the supercooling degree of the alloy decreases, the as-cast structure of the ingot is prone to coarsening, and at the same time, the higher melting temperature is likely to cause the induction coil to be damaged by burning, resulting in a weakening of the magnetic field force. Therefore, the melting temperature is controlled at 1500 - 1600 °C, and the melting power is 20 - 60 KW.

[0041] Specifically, in the above step 1, in the early stage of smelting, low-power smelting is first adopted, and then the power is gradually increased to completely melt the raw materials. After all the raw materials are melted, keep warm for 5-10 minutes for pouring.

[0042] Specifically, in the above step 2, the ingot mold for pouring is placed in the hearth of a circular heating furnace, and the hearth of the circular heating furnace is placed in a stainless steel pipe; the stainless steel pipe is used to support the heating furnace and the ingot mold; a large amount of refractory materials are filled between the heating furnace and the stainless steel pipe; an induction coil is arranged around the stainless steel pipe, and the current and waveform in the induction coil are controlled by a power supply device to perform magnetic field treatment on the superalloy melt after pouring.

[0043] Specifically, in the above step 2, an electric control cabinet can be used to apply pulsed electromagnetic fields to the superalloy melt.

[0044] Specifically, in the above step 2, the stainless steel pipe is made of 316 austenitic stainless steel. The wall thickness of the stainless steel pipe is 20-25 mm.

[0045] Specifically, in the above step 2, before pouring, the ingot mold is preheated by the heating furnace. Considering that when the preheating temperature is less than 400 °C, the temperature difference between the inside and outside of the ingot increases, and thermal cracks are likely to appear on the surface of the ingot. By increasing the preheating temperature of the ingot mold, the thermal stress and strain during the solidification of the ingot can be effectively reduced, and at the same time, the ability of the liquid metal to compensate for shrinkage in the later stage of the ingot can be improved, so as to control the generation of thermal cracks during the solidification process; when the preheating temperature of the ingot mold exceeds 600 °C, the heating time of the ingot mold is too long, and the stress at the chamfer of the inner wall of the ingot mold does not decrease significantly; considering comprehensively, the preheating temperature is controlled at 400-600 °C.

[0046] Specifically, in the above step 2, the waveform of the pulsed electromagnetic field is a rectangular wave. Using a rectangular wave can accurately control the time of the pulsed electromagnetic field acting on the alloy melt.

[0047] Specifically, in the above step 2, the current I of the pulsed electromagnetic field and the diameter d of the ingot conform to the following relationship: I = kd, where the value range of k is 0.6-1, the unit of I is A, and the unit of d is mm.

[0048] Preferably, when the diameter d of the ingot is 100-120 mm, the current I of the pulsed electromagnetic field is 60-80 A;

[0049] when the diameter d of the ingot is 150-170 mm, the current I of the pulsed electromagnetic field is 100-150 A;

[0050] when the diameter d of the ingot is 200-220 mm, the current I of the pulsed electromagnetic field is 160-200 A;

[0051] when the diameter d of the ingot is 250-270 mm, the current I of the pulsed electromagnetic field is 210-230 A;

[0052] The diameter d of the ingot is 300 - 320 mm, and the current I of the pulsed electromagnetic field is 250 - 300 A.

[0053] Specifically, in the above step 2, the duty cycle of the current of the pulsed electromagnetic field is 20% - 40%, such as 23%, 25%, 30%, 35%; the frequency is 25 - 36 HZ, such as 27 HZ, 30 HZ, 32 HZ.

[0054] It should be noted that in the above step 2, it is necessary to precisely control the start time and end time of the pulsed electromagnetic field, as well as the specific process parameters of the pulsed electromagnetic field. Through the above precise control, the segregation of elements in the superalloy ingot can be reduced, and the grain size is small. The control of the above process steps and parameters can ensure that thermodynamic conditions for improving the segregation of alloying elements can be formed inside the alloy melt. When the current output is too small, the Lorentz force of the electromagnetic field is small, the stirring effect on the superalloy solute solution is weak, the driving force for the movement of the melt in the micro-region at the solidification front is small, and it is difficult for alloying elements to diffuse sufficiently; when the current is too large, the superalloy melt is stirred violently, and greater segregation of alloying elements and shrinkage cavities are likely to occur; when the frequency is less than 25 HZ, the vibration of the solid-solution interface of the superalloy melt cannot be effectively promoted, the solute concentration at the interface is low, and the solute flow is weak. When the frequency is higher than 35 Hz, the solute concentration at the interface is high, the solute flow is enhanced, and the solute flow is prone to disorder, resulting in greater segregation. Therefore, when the frequency is controlled between 25 HZ and 35 HZ, the solute can be evenly distributed and has good fluidity. When the duty cycle is less than 20%, the edge region of the ingot is easily affected by the pulsed magnetic field, but the central region is hardly affected, resulting in poor cross-sectional tissue uniformity and uneven solute element distribution; when the duty cycle is greater than 40%, the intermittency of the pulse is lost, the heat transfer capacity of the melt is reduced, and the continuous high temperature makes it difficult for the melt to nucleate, and the effect of the pulsed magnetic field on reducing segregation and refining grains is gradually weakened.

[0055] Specifically, in the above step 2, after the pouring process is completed, the pulsed electromagnetic field continues to act, and the pulsed electromagnetic field is turned off after 60 - 100 s. This is because when the electromagnetic action time is less than 60 s, the ingot is not completely solidified, and the electromagnetic field still plays a role; when the electromagnetic action time is higher than 100 s, the ingot is completely solidified, and the effect of the electromagnetic field on the solidification structure is significantly weakened.

[0056] Specifically, in the above step 3, the homogenization treatment includes the following steps:

[0057] S301: Keep the ingot at 650 - 750 °C for heat preservation;

[0058] S302: Raise the temperature to 1000 - 1020 °C and keep it for heat preservation;

[0059] S303: Raise the temperature to 1150 - 1170 °C and keep it for heat preservation;

[0060] S304. Heat up to 1200 - 1220 °C and hold the temperature.

[0061] S305. Cool down to 950 - 1050 °C and hold the temperature. After taking out of the furnace, air cool to room temperature.

[0062] Specifically, the holding times T1 of S301, T2 of S302, T3 of S303, and T4 of S304 satisfy the following relationship: T1 < T2, T3 < T4.

[0063] Specifically, the heating rates V1 in S302, V2 in S303, and V3 in S304 satisfy the following relationship: V1 > V2 > V3.

[0064] Specifically, the holding time of S301 is 3 - 5 h, such as 3.5 h, 4 h, 4.5 h; the holding time of S302 is 15 - 25 h, such as 17 h, 20 h, 23 h; the holding time of S303 is 15 - 25 h, such as 17 h, 20 h, 23 h; the holding time of S304 is 60 - 80 h, such as 63 h, 65 h, 67 h, 70 h, 73 h, 75 h, 77 h.

[0065] Specifically, the heating rate V1 in S302 is 40 - 50 °C / h, such as 43 °C / h, 45 °C / h, 47 °C / h; the heating rate V2 in S303 is 20 - 30 °C / h, such as 23 °C / h, 25 °C / h, 27 °C / h; the heating rate V3 in S304 is 5 - 10 °C / h, such as 7 °C / h, 8 °C / h, 9 °C / h.

[0066] Specifically, the cooling rate V4 in S305 is 45 - 50 °C / h, such as 47 °C / h, 48 °C / h, 49 °C / h.

[0067] Specifically, the holding time of S305 is 0.5 - 1 h, such as 0.6 h, 0.7 h, 0.8 h, 0.9 h.

[0068] It should be noted that during the homogenization treatment process of step 3 above, first hold the temperature at 650 - 750 °C to prevent large temperature differences inside and outside the ingot caused by too fast heating and too high temperature, which may lead to ingot cracking; then quickly heat up to 1000 - 1020 °C and hold the temperature, so that the low melting point phases σ and carbides M of the superalloy 23C6 is fully dissolved in the matrix; then it is heated to 1150 - 1170 °C at a relatively fast heating rate and held for heat treatment, and the low melting point phase η and boride are further dissolved; finally, it is heated to 1200 - 1220 °C at a slower heating rate to accelerate the diffusion of alloying elements, reduce microsegregation. Eventually, by adopting the above multi-stage homogenization process, the compositional segregation and microstructural segregation of the ingot are significantly reduced, an ingot with uniform composition and microstructure is obtained, and at the same time, the plasticity of the ingot is improved.

[0069] Specifically, during the homogenization treatment in step 3 above, it is first cooled to 950 - 1050 °C and held for heat treatment before cooling. At this time, the superalloy is in the γ + γ′ two-phase region, obtaining a two-phase structure, improving the grain boundary state, further enhancing the hot plasticity of the superalloy, further preventing the alloy from cracking during cogging, and realizing the cogging forging of the difficult-to-deform superalloy.

[0070] Compared with the prior art, in the method for preparing a superalloy low-segregation ingot of the present invention, after the alloy liquid is subjected to pulsed electromagnetic treatment at the beginning of pouring, under the action of the electromagnetic field, the solute fluidity at the front of the solidification interface increases, solute elements can be fully mixed, the segregation degree of the ingot is significantly reduced, and at the same time, the segregation behavior of carbides is inhibited, and the alloy composition uniformity is improved; and during the pulsed magnetic field treatment, convective motion occurs inside the alloy melt, the crystal nuclei on the mold wall fall off and become free, increasing the number of crystal nuclei in the alloy, promoting the formation of a large number of equiaxed crystals in the ingot, significantly refining the ingot microstructure, suppressing columnar crystals, and also reducing the segregation of alloying elements in the ingot; the number of crystal nuclei nucleated in the superalloy melt increases, the grain size of the ingot decreases, and the mechanical properties and hot plasticity are improved. Finally, through high-temperature homogenization treatment, the segregation of alloying elements in the ingot is basically eliminated, a superalloy ingot with low segregation is obtained, and the hot working plasticity of the ingot is significantly improved.

[0071] The ingot prepared after the above homogenization treatment can be directly used for cogging forging without going through the electroslag remelting process and the vacuum consumable process, significantly reducing the preparation cost of the ingot.

[0072] The present invention also provides a superalloy low-segregation ingot prepared by the above preparation method.

[0073] Specifically, the components of the above superalloy are in mass percentages, including C: 0.02% - 0.10%, Cr: 18.0% - 21.0%, Co: 13.0% - 14.0%, Mo: 3.50% - 5.00%, Al: 1.2% - 1.6%, Ti: 2.80% - 3.3%, and the balance is nickel.

[0074] The segregation of the superalloy low-segregation ingot of the present invention is small, there is no segregation of carbides, the grain size is fine, the tissue uniformity is good, and the toughness and plasticity are excellent. For example, the element segregation coefficients at the center of the ingot are as follows: Ti: 1.09 - 1.15, Mo: 1.00 - 1.03, Cr: 0.98 - 1.00, Co: 0.96 - 1.00; the element segregation coefficients at the edge of the ingot are as follows: Ti: 1.04 - 1.10, Mo: 1.02 - 1.11, Cr: 0.98 - 1.00, Co: 0.98 - 1.00; the grain size of the ingot is about 120 - 160 μm, and the grains are fine. The hardness fluctuation from the center to the edge of the ingot is small. For example, the hardness difference from the center to the edge of the ingot is below 3 HRC.

[0075] Specifically, the room-temperature tensile strength of the above-mentioned superalloy low-segregation ingot is above 680 MPa (for example, 681 - 700 MPa), the yield strength is above 440 MPa (for example, 442 - 460 MPa), the elongation after fracture is above 20% (for example, 20.5% - 23.5%), and the reduction of area is above 40% (for example, 42% - 49%); the properties of the ingot at 650 °C are as follows: the tensile strength is above 590 MPa (for example, 597 - 620 MPa), the yield strength is above 350 MPa (for example, 350 - 370 MPa), the elongation after fracture is above 26% (for example, 26.5% - 29%), and the reduction of area is above 32% (for example, 32% - 35%).

[0076] The following uses specific examples and comparative examples to demonstrate the advantages of precise control of the process parameters of the present invention.

[0077] Example 1

[0078] This example provides a method for preparing a superalloy low-segregation ingot. The components of the superalloy in this example are shown in Table 1 below, and the method includes the following steps:

[0079] Place the nickel-based superalloy raw materials in a 20 kg induction furnace for melting. The melting temperature is 1550 °C, and the smelting power is 20 - 60 KW (at the beginning of smelting, low power smelting is first used, and then the power is gradually increased to completely melt the raw materials). After complete melting, low power smelting is used again. After holding for 6 minutes, pouring is carried out;

[0080] Before pouring, preheat the ingot mold to 600 °C through a heating furnace; after pouring starts, quickly turn on the electric control cabinet to apply pulsed electromagnetic force to the superalloy melt. Among them, the output current of the electric control cabinet is 70 A, the duty cycle is 30%, the frequency is 30 HZ, and the electromagnetic waveform is a rectangular wave; after the pouring process is completed, continue to apply pulsed electromagnetic force, and turn off the pulsed electromagnetic force after 70 s to obtain an ingot; the ingot size is

[0081] Subsequently, the ingot was subjected to high-temperature and long-time homogenization treatment: the ingot was held at 700 °C for 4 h; then it was heated to 1020 °C at a rate of 48 °C / h and held for 25 h; then it was heated to 1160 °C at a rate of 25 °C / h and held for 25 h; then it was heated to 1200 °C at a rate of 10 °C / h and held for 70 h; finally, it was cooled to 1000 °C at a rate of 48 °C / h, held for 1 h, and air-cooled to room temperature after being taken out of the furnace.

[0082] Example 2

[0083] This example provides a method for preparing a low-segregation ingot of superalloy. The components of the superalloy in this example are shown in Table 1 below, and the method includes the following steps:

[0084] Put the nickel-based superalloy raw materials into a 20 kg induction furnace for melting. The melting temperature is 1580 °C, and the smelting power is 20 - 60 KW (low power is used for smelting at the beginning, and then the power is gradually increased to completely melt the raw materials). After complete melting, hold for 10 min and then pour.

[0085] Before pouring, preheat the ingot mold to 600 °C through a heating furnace; after pouring starts, quickly turn on the electric control cabinet to apply pulsed electromagnetic field to the superalloy melt. Among them, the output current of the electric control cabinet is 74 A, the duty cycle is 32%, the frequency is 28 HZ, and the electromagnetic waveform is a rectangular wave; continue to apply pulsed electromagnetic field after the pouring process is completed, turn off the pulsed electromagnetic field after 80 s, and obtain the ingot; the size of the ingot is

[0086] Subsequently, the ingot was subjected to high-temperature and long-time homogenization treatment: the ingot was held at 700 °C for 4 h; then it was heated to 1020 °C at a rate of 47 °C / h and held for 20 h; then it was heated to 1170 °C at a rate of 25 °C / h and held for 20 h; then it was heated to 1220 °C at a rate of 8 °C / h and held for 70 h; finally, it was cooled to 1000 °C at a rate of 46 °C / h, held for 0.5 h, and air-cooled to room temperature after being taken out of the furnace.

[0087] Example 3

[0088] This example provides a method for preparing a low-segregation ingot of superalloy. The components of the superalloy in this example are shown in Table 1 below, and the method includes the following steps:

[0089] (1) Put the nickel-based superalloy raw materials into a 20 kg induction furnace for melting. The melting temperature is 1560 °C, and the smelting power is 20 - 60 KW (low power is used for smelting at the beginning, and then the power is gradually increased to completely melt the raw materials). After complete melting, hold for 10 min and then pour.

[0090] (2) Before pouring, preheat the ingot mold to 590 °C through a heating furnace; after the pouring starts, quickly open the electric control cabinet to apply pulsed electromagnetic field to the superalloy melt. Among them, the output current of the electric control cabinet is 120 A, the duty cycle is 35%, the frequency is 36 HZ, and the electromagnetic waveform is a rectangular wave; after the pouring process is completed, continue to apply the pulsed electromagnetic field, and turn off the pulsed electromagnetic field after 90 s to obtain an ingot; the size of the ingot is

[0091] (3) Subsequently, perform high-temperature long-time homogenization treatment on the ingot: keep the ingot at 750 °C for 5 h; then heat it up to 1020 °C at a rate of 40 °C / h and keep it for 25 h; then heat it up to 1170 °C at a rate of 20 °C / h and keep it for 25 h; then heat it up to 1220 °C at a rate of 10 °C / h and keep it for 80 h; finally, cool it to 1050 °C at a rate of 45 °C / h, keep it for 1 h, and air-cool it to room temperature after taking it out of the furnace.

[0092] During the research process, the inventor conducted a large number of studies and now takes some solutions with poor performance as comparative examples.

[0093] Comparative Example 1

[0094] This comparative example provides a method for preparing a superalloy ingot with low segregation. The components of the superalloy in this comparative example are the same as those in Example 1, and the overall steps of the preparation method are the same as those in Example 1. The differences are as follows:

[0095] (2) During pouring, the current is 50 A, the duty cycle is 10%, and the frequency is 20 HZ; after the pouring process is completed, continue to apply the pulsed electromagnetic field, and turn off the pulsed electromagnetic field after 30 s.

[0096] Comparative Example 2

[0097] This comparative example provides a method for preparing a superalloy ingot with low segregation. The components of the superalloy in this comparative example are the same as those in Example 1, and the overall steps of the preparation method are the same as those in Example 1. The differences are as follows:

[0098] (2) During pouring, the current is 50 A;

[0099] (3) During this process, heat the ingot to 1010 °C at a rate of 45 °C / h and keep it for 30 h; then heat it to 1190 °C at a rate of 10 °C / h and keep it for 80 h; finally, cool it to 1000 °C at a rate of 46 °C / h and keep it for 0.5 h, and air-cool it to room temperature after taking it out of the furnace.

[0100] The chemical composition of the example is shown in Table 1 below.

[0101] Wire cut samples were taken from the ingots obtained in Example 1 and Comparative Example 1. The macrostructure of the ingot in Example 1 is as Figure 1 shown, and the macrostructure of the ingot in Comparative Example 1 is as Figure 2As shown, it is found that after comparison, the riser of the ingot of Example 1 after magnetic field treatment is significantly smaller than that of Comparative Example 1.

[0102] The grain sizes of the ingots of the examples and the comparative examples are shown in Table 2 below. It can be seen that the grain size of the ingot of the example of the present invention is finer than that of the comparative example. For example, the grain size of the ingot of the example is 120 - 160 μm.

[0103] The carbides in the ingot of Example 1 are as Figure 3 shown, and the carbides in the ingot of Comparative Example 1 are as Figure 4 shown. It can be seen that there is no segregation phenomenon of carbides in Example 1.

[0104] The segregation coefficients of Ti, Mo, Cr, and Co in the ingots of the examples and the comparative examples are shown in Table 3; it can be seen that the segregation degree of the ingots of the present invention is small and the compositional uniformity is good.

[0105] The hardness fluctuation from the center to the edge of the ingot of the example is small, and the mechanical properties are significantly improved. For example, the hardness difference from the center to the edge of the ingot is below 3 HRC. The hardness difference from the center to the edge of the ingot of Comparative Example 1 reaches 8 HRC, and the hardness difference from the center to the edge of the ingot of Comparative Example 2 reaches 7 HRC. It can be seen that the compositional properties of the ingots of the present invention are more uniform and stable.

[0106] The properties of the examples and the comparative examples are shown in Table 4 below. It can be seen that the ingots of the present invention have good hot plasticity.

[0107] Table 1 Chemical composition, wt%

[0108] Number C Cr Co Mo Al Ti Example 1 0.035 19.29 13.28 4.46 1.59 3.12 Example 2 0.031 19.46 13.54 4.34 1.45 3.18 Example 3 0.034 19.12 13.25 4.31 1.42 3.07

[0109] Table 2 Grain sizes of the ingots

[0110] Number Grain size / μm Example 1 120～150 Example 2 130～160 Example 3 120～160 Comparative Example 1 190～220 Comparative Example 2 180～220

[0111] Table 3 Alloy element segregation coefficients

[0112]

[0113]

[0114] Table 4 Ingot performance test results

[0115]

[0116] The above is only the preferred specific implementation manners of the present invention, but the protection scope of the present invention is not limited thereto. Any change or replacement that can be easily thought of by those skilled in the technical field of the present invention within the technical scope disclosed by the present invention shall be covered by the protection scope of the present invention.

Claims

1. A method for preparing a superalloy ingot with low segregation, characterized in that the components of the superalloy, by mass percentage, include C: 0.02% - 0.10%, Cr: 18.0% - 21.0%, Co: 13.0% - 14.0%, Mo: 3.50% - 5.00%, Al: 1.2% - 1.6%, Ti: 2.80% - 3.3%, and the balance is nickel; the preparation method includes the following steps: Step 1, melt to obtain alloy liquid; Step 2, pour the alloy liquid into an ingot mold. After the pouring starts, apply pulsed electromagnetic treatment to the alloy liquid. After the pouring process is completed, continue to apply pulsed electromagnetic for 60 - 100 s, and then turn off the pulsed electromagnetic to obtain an ingot; Step 3, perform homogenization treatment on the ingot to obtain a superalloy ingot with low segregation; In the said Step 2, the waveform of the pulsed electromagnetic is a rectangular wave; the current I of the pulsed electromagnetic and the ingot diameter d satisfy the following relationship: I = kd, where the value range of k is 0.6 - 1, the unit of I is A, and the unit of d is mm; In the said Step 2, the duty cycle of the pulsed electromagnetic current is 30% - 40%, and the frequency is 28 - 36 HZ; In the said Step 3, the homogenization treatment includes the following steps: S301, keep the ingot at 650 - 750 °C for heat preservation; S302, raise the temperature to 1000 - 1020 °C and keep it for heat preservation; S303, raise the temperature to 1150 - 1170 °C and keep it for heat preservation; S304, raise the temperature to 1200 - 1220 °C and keep it for heat preservation; S305, lower the temperature to 950 - 1050 °C and keep it for heat preservation; after taking out of the furnace, air-cool to room temperature; The heating rate V1 in S302, the heating rate V2 in S303, and the heating rate V3 in S304 satisfy the following relationship: V1 > V2 > V3; V1 is 40 - 50 °C / h, and V3 is 5 - 10 °C / h; The segregation of the superalloy ingot with low segregation is small. The element segregation coefficients at the center of the ingot are as follows: Ti: 1.09 - 1.15, Mo: 1.00 - 1.03, Cr: 0.98 - 1.00, Co: 0.96 - 1.00; the element segregation coefficients at the edge of the ingot are as follows: Ti: 1.04 - 1.10, Mo: 1.02 - 1.11, Cr: 0.98 - 1.00, Co: 0.98 - 1.

00.

2. The preparation method according to claim 1, characterized in that, In the said Step 2, preheat the ingot mold through a heating furnace before pouring, and the preheating temperature is 400 - 600 °C.

3. The preparation method according to claim 1, characterized in that, In the said Step 2, when the ingot diameter d is 100 - 120 mm, the current I of the pulsed electromagnetic is 60 - 80 A; when the ingot diameter d is 150 - 170 mm, the current I of the pulsed electromagnetic is 100 - 150 A; when the ingot diameter d is 200 - 220 mm, the current I of the pulsed electromagnetic is 160 - 200 A.

4. The preparation method according to claim 1, characterized in that, In the said Step 2, the duty cycle of the pulsed electromagnetic current is 30% - 35%.

5. The preparation method according to claim 1, characterized in that In the said Step 3, the heat preservation time T1 in S301, the heat preservation time T2 in S302, the heat preservation time T3 in S303, and the heat preservation time T4 in S304 satisfy the following relationship: T1 < T2, T3 < T4.

6. A superalloy ingot with low segregation, characterized in that, The superalloy low-segregation ingot is prepared by using the preparation method described in any one of claims 1 to 5.

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