WO2021036226A1

WO2021036226A1 - Large-size high-niobium and high-temperature 706 alloy ingot and smelting process thereof

Info

Publication number: WO2021036226A1
Application number: PCT/CN2020/078719
Authority: WO
Inventors: 黄烁; 赵光普; 张北江; 段然; 秦鹤勇; 李连鹏; 丑英玉; 齐超
Original assignee: 北京钢研高纳科技股份有限公司; 抚顺特殊钢股份有限公司
Priority date: 2019-08-28
Filing date: 2020-03-11
Publication date: 2021-03-04
Also published as: CN111876651A; CN111876651B

Abstract

Provided are a large-size high-niobium and high-temperature 706 alloy ingot and a smelting process thereof, wherein the smelting process includes: vacuum induction smelting to obtain multiple vacuum induction ingots with the same composition, then the same number of electroslag electrodes are prepared, using (CaF 2-CaO-Al 2O 3-TiO 2) quaternary slag to exchange electroslag remelting, using the obtained electroslag ingot to obtain consumable electrode, then using the consumable electrode as the starting material to perform two vacuum consumable remelting. This process can be used to prepare large-size ingots of high-niobium and high-temperature 706 alloy with an ingot weight of more than 15 tons and a diameter of more than 800 mm, minimizing the formation of black spots and white spots metallurgical defects, and reducing the burning rate of Al and Ti elements.

Description

Large-size high-niobium high-temperature 706 alloy ingot and smelting process

Technical field

The invention relates to the technical field of large-size high-niobium alloys, and more specifically, it relates to a large-size high-niobium high-temperature 706 alloy ingot and its smelting process.

Background technique

706 superalloy is a special alloy. By adding elements (chromium, tungsten, molybdenum, etc.) different in size from the base metal atoms (such as nickel) in the raw material, it causes the distortion of the base metal lattice, which can be reduced by adding Alloy matrix stacking fault energy elements (such as cobalt) and adding elements that can slow down the diffusion rate of matrix elements (tungsten, molybdenum, etc.) to strengthen the matrix. Through the aging treatment, the second phase (γ', γ", carbide, etc.) can be precipitated from the supersaturated solid solution in the steel ingot to strengthen the alloy. The structure of the γ'phase is the same as that of the matrix, which is a face-centered cubic structure, and the lattice constant is The matrix is similar and coherent with the crystal, so the γ'phase can be uniformly precipitated in the matrix in the form of fine particles, which hinders the movement of dislocations and produces a significant strengthening effect. The γ'phase is an A3B type intermetallic compound, and A represents nickel, Cobalt, B represents aluminum, titanium, niobium, tantalum, vanadium, and tungsten, while chromium, molybdenum, and iron can be either A or B. The typical γ'phase in nickel-based alloys is Ni3(Al, Ti), γ" The phase is a body-centered tetragonal structure, and its composition is Ni3Nb. Because the mismatch between the γ" phase and the matrix is large, it can cause a large degree of coherent distortion, so that the alloy can obtain a high yield strength, but when it exceeds 700 ℃, it is strengthened. The effect is significantly reduced, and special treatment processes are required. Moreover, for the 706 alloy containing Al and Ti elements, the burning of Al and Ti elements is prone to occur during the electroslag remelting process, which is also an urgent problem to be solved in the preparation process.

In addition, for the high-temperature nickel-based 706 alloy with a Nb content of more than 3%, the triple smelting process of "vacuum induction melting + electroslag remelting + vacuum consumable remelting" is generally used for high-temperature large ingots of more than 10 tons produced in Europe and the United States. For example, the patent US20020170386A1 provides a triple smelting process for large ingots with an alloy diameter of 762 mm or more. During the use of this triple smelting equipment, the diameter of the ingot type and the electrode needs to be matched. The patent provides several examples of the matching of the ingot type and the electrode. However, for superalloy consumable ingots weighing more than 15 tons, taking into account the loss between the triple smelting process (electrode car light and flat head and tail), the weight of vacuum induction ingots exceeds 20 tons, which is suitable for vacuum induction furnaces and electroslag remelting furnaces. The equipment capacity is more demanding. At present, the main technical bottleneck for domestic production of large ingots of high-temperature alloys of more than 15 tons is that there is no vacuum induction melting equipment with a nominal capacity of more than 20 tons, and it is impossible to prepare a single vacuum induction electrode ingot of more than 20 tons. In order to solve this problem and adapt to the domestic equipment situation, only two 10-ton induction ingots can be poured in a vacuum induction furnace, and then remelted using double-arm exchange electrodes, and two small-tonnage short electrodes are used to prepare large-tonnage high-temperature alloys. Electroslag ingots are then used for subsequent vacuum consumable remelting through forged electrodes. However, the double-arm exchange electrode remelting method is used to prepare large-size electroslag ingots, and a series of quality defects such as injection, flow steel, composition fluctuation and inclusions are easily formed during the electrode exchange process, even through the subsequent high-temperature diffusion annealing. And electrode forging can not completely eliminate the above-mentioned quality defects. In the subsequent vacuum consumable remelting process, when smelted to the electrode joint, the above-mentioned quality defects will cause the consumable remelting process smelting parameters to fluctuate, and the 706 alloy with a high degree of alloying affects the consumable remelting smelting process parameters Very sensitive, parameter fluctuations are prone to smelting defects such as black spots and white spots, which will affect the metallurgical quality of consumable ingots.

Summary of the invention

In view of the shortcomings of the prior art, the first object of the present invention is to provide a large-size high-niobium high-temperature 706 alloy ingot, the weight of the obtained ingot can reach at least 15 tons, and there is no metallurgical defects such as black spots and white spots. , Ti element has no obvious burning loss. The bar forged from the ingot has been inspected by non-destructive flaw detection, and it is found that there is no abnormal signal at the electroslag remelting joint.

The second object of the present invention is to provide a smelting process for the above-mentioned large-size high-niobium high-temperature 706 alloy ingots, which realizes the smelting of large-size high-niobium high-temperature alloy ingots with an ingot weight of 15 tons or more and a diameter of 800 mm or more. The smelting process is Al, Ti element has no obvious burning loss, can effectively prevent the problem of hot cracking, minimize the formation of black and white metallurgical defects, reduce the degree of element segregation, and improve the thermoplasticity of the steel ingot.

In order to achieve the above objective, the present invention provides the following technical solution: a large-size high-niobium high-temperature 706 alloy ingot, characterized in that the high-niobium high-temperature alloy large-size ingot has a diameter of 800mm or more, and is calculated by mass percentage. The chemical composition of the large-size high-niobium high-temperature 706 alloy ingot is:

C≤0.02wt%, Cr 15.5～16.5wt%, Ni 40.0～43.0wt%, Nb 2.8～3.2wt%, Ti 1.5～1.8wt%, Al 0.1～0.3wt%, Si≤0.10wt%, Mn≤0.20 wt%, P≤0.015wt%, S≤0.0013wt%, Co≤0.30wt%, Mo≤0.20wt%, B≤0.006wt%, Cu≤0.30wt%, Ca≤0.005wt%, N≤0.006wt% , O≤0.005wt%, Fe balance.

The smelting process of large-size high-niobium high-temperature 706 alloy ingot provided by the present invention includes the following steps:

Vacuum induction smelting: According to the designed alloy composition requirements, the pure metal raw materials and/or return materials are weighed according to the required elements of the alloy per unit weight as raw materials, and vacuum induction smelting is performed to control the Ni content in the smelting mother liquor to 40.0-43.0wt%. Nb content is 2.80～3.3wt%, Ti content is 0.5～2.0wt%, Al content is 0.2～0.5wt%, and multiple vacuum induction ingots with the same composition are poured;

Exchange electroslag remelting: the same number of electroslag electrodes are prepared by using the vacuum induction ingots made; all the prepared electroslag electrodes are used, and the exchange electroslag remelting is performed under argon protection. The slag system used is ( CaF ₂ -CaO-Al ₂ O ₃ -TiO ₂ ) quaternary slag, (CaF ₂ -CaO-Al ₂ O ₃ -TiO ₂ ) quaternary slag contains _{60～75wt% of CaF 2} and 10～25wt% of CaO. Al ₂ O ₃ accounts for 8 to 13 wt%, and TiO ₂ accounts for 1 to 10 wt%; after the exchange electroslag remelting is completed, it is cooled and demolded to obtain an electroslag ingot:

Primary vacuum consumable remelting: the demolded electroslag ingot is subjected to primary annealing, secondary annealing, forging and drawing to a predetermined size to obtain a primary consumable electrode, wherein the secondary annealing temperature is higher than the primary annealing temperature; then use A consumable electrode is remelted once in vacuum;

Secondary vacuum consumable remelting: the primary consumable remelted ingots obtained by the primary vacuum consumable remelting, car light, flat head and tail, to obtain a secondary consumable electrode; then use the secondary consumable electrode for secondary vacuum Consumable remelting to prepare ingots of target diameter

In the above technical scheme of the present invention, in order to overcome the burning loss of Al and Ti, the Al content in the smelting mother liquor is controlled to be between 0.2 and 0.5 wt%, and the additional Al can be used as a deoxidizer to a certain extent, and remelting process using _{_{(CaF 2 -CaO-Al 2 O}} 3 -TiO 2) and four yuan slag _{_{(CaF 2 -CaO-Al 2 O}} 3 -TiO 2) four yuan CaF ₂ slag accounts for 60 ~ 75wt %, CaO accounts for 10-25wt%, Al ₂ O ₃ accounts for 8-13wt%, TiO ₂ accounts for 1-10wt%. According to the amount of additional Al added, the composition of each part of the slag system, especially the content of _{TiO 2} _{, The content of TiO 2} in the slag system is controlled to 1-10wt%, which can solve the burning problem of Ti element at the head and tail of the electroslag ingot, and also ensure the uniformity of the Ti composition in the electroslag ingot, and minimize the easily oxidized elements In order to overcome the problem of insufficient capacity of vacuum induction melting equipment, a conventional tonnage (such as 12 tons) vacuum induction furnace is used to prepare multiple induction ingots with the same composition (this also reduces the requirement for the weight of a single induction ingot), In this way, a plurality of electroslag electrodes are prepared, and then electrode exchange remelting is used to prepare large-tonnage electroslag ingots, and then two vacuum consumable remeltings are carried out. Among them, one vacuum consumable remelting can improve the electrode exchange joint. Metallurgical quality, and then through secondary vacuum consumable remelting, can completely solve the metallurgical quality problem, so as to prepare high-quality, non-metallurgical defects of at least 15 tons of high-temperature alloy large-size consumable ingot. Considering the loss, the total weight of multiple vacuum induction ingots should be 125% to 160% of the target weight of the ingot.

In a preferred embodiment, in the vacuum induction melting step, the melting temperature is 1300-1550°C. After the raw materials are melted, refining is carried out under electromagnetic stirring for 15-120 minutes, and the refining temperature is 1350-1550°C; then cooling for 1-10 hours After that, the mold is demolded to obtain a vacuum induction ingot; the vacuum induction smelting process is repeated many times, and there are many vacuum induction ingots with the same composition.

In fact, when the diameter of the vacuum induction ingot exceeds 800mm and the single weight exceeds 10 tons, large-size induction ingots of high-niobium superalloys will produce great thermal stress during the solidification process after casting, especially those containing Al, Ti aging precipitation alloys, after being cooled to the enhanced aging precipitation temperature range, will precipitate strengthening phases and cause greater structural stress, and in severe cases, the steel ingot will burst directly. However, if the demolding time is too short, the steel ingot is not completely solidified, and premature demolding is easy to crack.

For this reason, in a preferred embodiment, the method of preparing the electroslag electrode is to directly stress-relieve annealing each vacuum induction ingot. During annealing, the temperature is pre-heated to 600-800°C, and then at a rate of 5-45°C/h The temperature is raised to 800-1000℃ and kept for 4～32h, and then cooled to 600～800℃ for 4～32h at a rate of 1～35℃/h, then air-cooled, and then polished and flat-headed to obtain the electroslag electrode. Generally, the diameter of the resulting electroslag electrode should be matched with the diameter of the matching mold of the vacuum consumable electric arc furnace used in the vacuum consumable remelting step, that is, the diameter of the matching mold and the electrode should maintain an appropriate ratio, that is, filling The ratio is about 0.8 to 0.9.

This application adopts the above solution to directly stress-relieve and anneal the vacuum induction ingot. There are many advantages. First, it can prevent the temperature from falling into the aging precipitation zone due to air cooling after the ingot is demolded in time to form excessive structural stress; second, it can be used Reasonable heating rate increases the temperature of the steel ingot, aiming at the problem of low thermal conductivity of the superalloy, avoiding large thermal stress inside and outside the steel ingot; third, keeping the temperature at 800～1000℃ for a certain period of time can make the temperature of the steel ingot fully uniform and release the internal stress of solidification ; Fourth, the slow cooling of 1～35℃/h and the heat preservation of 600～800℃ for a certain time can effectively prevent the steel ingot from forming greater thermal stress and structural stress again.

In a preferred embodiment, when performing exchange electroslag remelting, the slag system used is (CaF ₂ -CaO-Al ₂ O ₃ -TiO ₂ ) quaternary slag, (CaF ₂ -CaO-Al ₂ O _3- TiO ₂ ) In the quaternary slag, CaF ₂ accounts for 60 to 75 wt%, CaO accounts for 10 to 25 wt%, Al ₂ O ₃ accounts for 8 to 13 wt%, and TiO ₂ accounts for 1 to 5 wt%. In a more preferred embodiment, electroslag The steady-state melting rate of remelting is controlled at 5-15kg/min, and before each electrode exchange, when the remaining weight of the current electrode is 500kg-1000kg, the steady-state melting rate will increase with a slope of 0.5-2kg/min. When the melting rate reaches 12-25kg/min, keep stable until the electroslag electrode is exchanged, and the electrode exchange process keeps the smelting parameters before the exchange, and the exchange time does not exceed 2min; after each electrode exchange is completed, when the next electrode melts 100kg After ~500kg, reduce the melting rate to a steady-state melting rate of 5~15kg/min with a slope of 0.5~2kg/min, continue remelting, and start heat sealing when the last electrode has 200~600kg remaining; exchange electroslag remelting ends After that, it is cooled for 2-10 hours, demoulded, and an electroslag ingot is obtained.

By adopting the above technical solutions, for ingots with diameters greater than 1000mm, the steady-state melting rate of electroslag remelting is controlled to be 5-15kg/min. The subsequent adjustment of the melting rate before and after the electrode exchange can reasonably increase the molten pool when the electrode is exchanged. The depth can solve the decrease of molten pool fluidity caused by the suspension of smelting during the electrode exchange process, reduce the disturbance of the molten pool caused by the instantaneous embedding of the electrode in the slag pool, and reduce the metallurgical quality problems such as inclusions and injection.

In a preferred embodiment, the demolded electroslag ingot is subjected to primary annealing, secondary annealing, forging and drawing to a predetermined size to obtain a consumable electrode. The specific implementation method is as follows:

For electroslag ingots, an annealing is started within 0.5-2h after demolding. Specifically, it is preheated to 300-550℃, held for 12-32h to achieve uniform temperature, and then heated at a rate of 1-25℃/h to 600～ Hold at 750°C for 4～32h, then heat up to 800～1000°C at a rate of 5～35℃/h and keep it at 800～1000℃ for 4～32h, then cool to 550～750℃ at a rate of 1～35℃/h and keep it at 4～32h, then Air cooling

Perform secondary annealing on the electroslag ingot after the primary annealing. Specifically, keep it at 550～750℃ for 4～24h, then at a rate of 5～35℃/h to 800～1000℃, and then at 1～25℃. Heat up to 1050～1150℃ for 4～32h at a rate of ℃/h, then heat up to 1150～1250℃ for 24～72h at a rate of 1～25℃/h, and then cool to 800 at a rate of 1～35℃/h Keep warm at ～950℃ for 4～32h, then air cooling;

For the electroslag ingot after secondary annealing, it is heated to 1100～1180℃ before forging, and the heating time before forging is 4～12h. The free forging adopts a fast forging machine of more than 3000 tons to draw the length in one direction, and each pass is pressed down on one side. The amount is controlled at 5～30mm, and the final forging temperature is 850～1000℃;

For the steel ingot after free forging and drawing, the head and tail are flattened, and a consumable electrode is obtained. Generally, the diameter of the primary consumable electrode should be matched with the diameter of the matching mold of the vacuum consumable arc furnace used in the primary vacuum consumable remelting.

The reason for adopting the above technical solution is that the obtained high-niobium superalloy ingots with a diameter of 1000mm or more in the electroslag ingots have great thermal stress during the solidification process and are very easy to burst; due to the reasonable requirements for consumable electrodes and corresponding crystallizers Filling ratio, the large-sized electroslag ingot cannot be directly used for one-time consumable remelting, and free forging is needed to reduce the diameter, for example, it can be 800-900mm; but because the diameter of the electroslag ingot is too large, solidification segregation Very serious, there are severe dendrite element segregation and low melting point phase between dendrites, and the thermoplasticity is extremely poor.

In order to solve the problem of thermal stress of high-niobium superalloy electroslag ingots with a diameter of more than 1000mm, the application, after the electroslag remelting is completed, is cooled by water in the water-cooled crystallizer in the adopted electroslag remelting furnace for 2-10 hours. To ensure that the steel ingot is fully solidified and cooled to below the aging precipitation temperature, an annealing is started within 0.5-2h after demolding. In the first annealing, preheat to 300～550℃ to avoid excessive thermal stress caused by excessive temperature, then keep the temperature at 300～550℃ for 12～32h to achieve uniform temperature, and then heat up to 600 at a rate of 1～25℃/h Keep it at ～750℃ for 4～32h, then heat it up to 800～1000℃ at a rate of 5～35℃/h and keep it for 4～32h, and then cool it at a rate of 1～35℃/h to 550～750℃ and keep it for 4～32h, Then air-cooled. Through the one-time annealing, the thermal stress formed by the temperature gradient during the solidification of the electroslag ingot can be released, and at the same time, the over-aging treatment is used to coarsen the strengthening phase to avoid the formation of structural stress, thereby inhibiting the direct explosion of the large-size superalloy electroslag ingot after demolding.

In order to improve the thermal plasticity of high-niobium superalloy electroslag ingots with a diameter of 800mm or more, the electroslag ingots should be subjected to secondary annealing after annealing, that is, high-temperature diffusion annealing. In order to avoid excessive thermal stress, the heating rate must be strictly controlled. Therefore, the electroslag ingot is kept at a temperature below 550-750°C for 4-24 hours, and then the temperature is raised to 800-1000°C at a rate of 5-35°C/h. Then at a rate of 1～25℃/h to 1050～1150℃ for 4～32h, then at a rate of 1～25℃/h to 1150～1250℃ for 24～72h, then 1～35℃/h It is cooled to 800～950℃ and kept for 4～32h at a high speed, and then air-cooled. Through multi-stage slow heating, it can avoid the formation of excessive thermal stress in the steel ingot to cause explosion. In addition, through high temperature and long-term diffusion annealing, the low melting point phase in the alloy can be re-dissolved, the dendrite element segregation can be weakened, and the thermoplasticity of the steel ingot can be improved. , To provide high-plasticity steel ingots for subsequent forging preparation of consumable electrodes.

In a preferred embodiment, during a vacuum consumable remelting, the steady-state melting rate is controlled to be 3.5-7.5kg/min; after 800-2000kg smelting is started, helium cooling is started; after the remaining 1500-5000kg, the current is reduced to adjust the melting rate to 3.0～7.0kg/min; after the remaining 200～1000kg, heat sealing is started to prepare a consumable remelted ingot.

In the above-mentioned vacuum consumable remelting process, the volume of the ingot will shrink during solidification, and there will be a gap with the mold wall. Under vacuum conditions, the cooling water of the steel ingot and the outer wall of the mold cannot directly contact the cooling water to achieve heat dissipation. Helium conducts heat; in the early stage of smelting, the steel ingot can dissipate heat through the bottom and the mold. When the smelting reaches a certain stage, the heat dissipation at the bottom is limited. For this reason, it is necessary to pass in a proper amount of helium after a certain stage of smelting. Melting stability, too little helium gas will not have the cooling effect; because the steel ingot is too large, the more the ingot solidifies, the greater the heat capacity and the more difficult the heat transfer. Therefore, at the end of smelting, it is necessary to appropriately reduce the melting rate and stabilize the depth of the molten pool. In turn, the probability of formation of metallurgical defects is reduced; the timing of heat sealing is judged according to the remaining weight of a consumable electrode, which can save the amount of steel ingot removal and increase the yield rate.

In a preferred embodiment, before the secondary vacuum consumable remelting, the primary consumable remelting ingot is first polished and flattened to obtain a diameter that matches the diameter of the crystallizer used in the secondary vacuum consumable remelting The secondary consumable electrode; when performing secondary vacuum consumable remelting, the steady-state melting rate is controlled to be 4.0～8.5kg/min; after smelting 1000～3000kg, it is cooled by helium gas; the current is reduced after the remaining 2000～5500kg Adjust the melting rate to 3.0～7.5kg/min; start heat sealing after the remaining 250～1500kg;

In a preferred embodiment, after the secondary consumable remelting is completed, vacuum cooling is performed for 1 to 8 hours, and then stress relief annealing is started within 2 hours; during annealing, it is preheated to 300 to 750°C and kept for 4 to 32 hours to achieve uniform temperature. Then the temperature is raised to 800-1000°C at a rate of 5-50°C/h, kept for 4 to 32 hours, and then cooled to 550-750°C at a rate of 1 to 35°C/h for 4 to 32 hours, and then air-cooled.

In a vacuum consumable remelting process, since the primary consumable electrode is forged by using multiple vacuum induction ingots to exchange electroslag ingots prepared by electroslag remelting, there are fluctuations in metallurgical quality at the electrode exchange joints. Even through high temperature diffusion and forging, it cannot be completely eliminated. Since the consumable remelting process is very sensitive to the quality of the electrode, it is prone to abnormal problems such as melting rate fluctuations and electrode blockage when remelting to the electrode exchange joint. It is easy to form metallurgical defects such as black and white spots, and cannot pass the subsequent high temperature. Diffusion annealing, forging or heat treatment processes are eliminated, which will directly cause the prepared bars or forgings to be scrapped in severe cases. For this reason, this application will turn the primary consumable remelting ingots, flat head and tail to prepare secondary consumable electrodes, and then perform secondary consumable remelting. Since the diameter of the steel ingot after the secondary consumable remelting exceeds 800mm, there will be great thermal stress, so after the secondary consumable remelting is completed, vacuum cooling is required, and then the stress relief annealing is started within 2h to avoid the steel ingot. After demolding, it bursts. During annealing, it should be preheated to 300～750℃ and kept for 4～32h to achieve uniform temperature, then at a rate of 5～50℃/h to 800～1000℃ and kept for 4～32h, and then at 1～35℃ Cooling to 550～750℃ for 4～32h at a rate of /h, and then air cooling. The subsequent use of this method can release the thermal stress formed by the temperature gradient during the solidification of the consumable remelted ingot. At the same time, the over-aging treatment is used to make The strengthening phase is coarsened to avoid the formation of structural stress, thereby inhibiting the direct explosion of large-size superalloy electroslag ingots after demolding.

The invention has the following advantages:

1. The method for preparing large-size, high-niobium, high-temperature 706 alloy provided by the present invention, by reasonably controlling the amount of Al added in the molten steel, and adopting a specific quaternary slag system in the exchange electroslag remelting process, can make the process There is no Al and Ti elements and no obvious burning loss.

2. The present invention can break through the tonnage limit of induction furnace and atmosphere protection electroslag furnace, adopting conventional tonnage (such as 12 tons) vacuum induction furnace to prepare 2 electrodes, and then using electroslag furnace to exchange electrodes to smelt 2 induction ingots into 1 Electroslag ingots, which are then used to manufacture vacuum consumable ingots of at least 15 tons;

3. The electroslag furnace with limited tonnage of the electrode arm can be used to prepare 20-ton high-temperature alloy electroslag ingots by the method of exchange electroslag remelting;

4. Electroslag ingots prepared by exchange electroslag remelting are subjected to high temperature diffusion annealing to obtain a certain degree of thermoplasticity, and then free forging is used to open the billet to prepare a consumable electrode with a suitable diameter, which can significantly improve the melting stability of a consumable remelting process. Sex

5. The secondary consumable electrode prepared by the primary consumable remelting steel ingot is used for the secondary consumable remelting. If necessary, further consumable remelting is performed multiple times, which can effectively solve the electroslag exchange during the electroslag remelting process. Metallurgical defects such as inclusions at the ingot exchange electrode joints are used to prepare high-niobium superalloy consumable ingots with a diameter of 800mm or more and an ingot weight of more than 15 tons without metallurgical defects.

detailed description

Hereinafter, the present invention will be further described in detail with reference to the embodiments.

Example 1:

This embodiment is used to illustrate the method of preparing 706 alloy (a consumable ingot with a diameter of 1050 mm).

Target 706 alloy composition (by mass percentage):

C 0.018%, Cr 15.8%, Ni 41.5%, Nb3.01%, Ti1.72%, Al 0.25%, Si0.02%, Mn0.01%, P0.006%, S0.0006%, Co0.02% , Mo0.01%, B0.004%, Cu0.02%, Ca0.004%, N0.005%, O0.002%, Fe balance.

The specific preparation method is as follows:

Vacuum induction smelting: According to the designed alloy composition requirements, 50% of the return material is weighed according to the required elements of the alloy per unit weight, and the rest is made of new metal raw materials. Using a 12-ton vacuum induction furnace, the upper limit of the melting temperature is 1550℃. After melting, the composition of the molten steel is detected. By adding new metal, the content of Ni in the molten steel is controlled to be about 42.0wt%, the content of Nb is about 3.02wt%, and the content of Ti is about 1.80 wt%, Al content is about 0.30wt%; according to the amount of added metal material, refining is performed under electromagnetic stirring for 15-30 minutes, the refining temperature is 1350°C, and the tapping temperature is 1400°C. After pouring the steel, the furnace is cooled for 4 hours and then demolded to obtain two 12-ton vacuum electrode ingots with a diameter of 820 mm, which are then directly annealed. The annealing furnace is preheated to 600°C, and then heated at a rate of 5°C/h to 800°C for 24 hours, and then cooled at a rate of 1°C/h to 600°C for 10 hours, and then air-cooled.

The annealed vacuum induction ingot car/polishing, flat head and tail are used to prepare the electroslag electrode.

Electroslag remelting: The diameter of the crystallizer is 1100mm, and the slag system is (CaF ₂ -CaO-Al ₂ O ₃ -TiO ₂ ) quaternary slag. The specific composition is: CaF ₂ 60%, CaO 10%, Al ₂ O ₃ 13% , TiO ₂ 10%. The steady-state melting rate is 15kg/min, and Ar gas protection at a pressure of 0.2bar is introduced during the melting process to prevent the molten steel from contacting oxygen and nitrogen in the air during the melting process. Before the electrode exchange, when the remaining weight is 800kg, adjust the input power and voltage to increase the melting rate. On the basis of the steady-state melting rate, increase the melting rate with a slope of 1.05kg/min. When it reaches 25kg/min, it will remain stable until the electroslag electrode is exchanged. . The electrode exchange process maintains the smelting parameters before the exchange, and the exchange time cannot exceed 2 min. After the electrode exchange is completed, after the second electrode melts 100kg, the melting rate is increased by adjusting the input power and voltage, and the melting rate is reduced to 10kg/min at a slope of 0.50kg/min. After the second electrode remains 200kg, the heat sealing starts.

After the electroslag remelting is completed, the water-cooled crystallizer in the furnace is cooled by water for 4 hours, and within 0.5 hours after demolding, it is transferred to the annealing furnace for stress relief annealing. The annealing furnace should be pre-heated to 300°C, kept at 300°C for 12h, then at a rate of 5°C/h to 600°C for 4h, then at a rate of 10°C/h to 800°C for 5h, and then at 5°C/h Cool down to 600°C for 12 hours at a rate of h, then cool in air.

High temperature diffusion annealing of electroslag ingots: install the furnace at a temperature below 550°C for 4 hours, then heat up to 800°C at a rate of 10°C/h, then heat up to 1050°C at a rate of 5°C/h, hold for 4 hours, and then heat at 5°C/h The temperature was raised to 1150°C for 24 hours at a rate of h, and then cooled to 800°C for 32 hours at a rate of 5°C/h, and then air-cooled.

Electrode forging: The heating temperature before forging of the electroslag ingot with a diameter of 1100mm is 1100℃, and the heating time before forging is 4h. The free forging adopts a 3500 ton fast forging machine to draw length in one direction, and the unilateral reduction of each pass is controlled to 25mm, the final forging temperature is 850℃, and the final forging, turning, and flat head and tail are prepared to a diameter of 820mm. Extremely, used for a vacuum consumable remelting.

One-time vacuum consumable remelting: The diameter of the crystallizer is 920mm, the consumable remelting is controlled by the melting rate, and the steady-state melting rate is controlled to 3.5kg/min; the helium cooling is started after 800kg of smelting; after the remaining 1500kg, the current is reduced to adjust the melting The speed reaches 3.0kg/min; after the remaining 200kg, the heat sealing is started, and the heat sealing is controlled by the current. The primary consumable remelting ingot is machined and flat-headed to a diameter of 900mm, which is used for secondary vacuum consumable remelting.

Secondary vacuum self-consumption remelting: 1050mm is used for the crystallizer, the melting is controlled by the melting rate, and the steady-state melting rate is controlled to 4.0kg/min; the helium cooling is started after the smelting of 1000kg; after the remaining 2000kg, the current is reduced to adjust the melting rate to 3.0 kg/min; after the remaining 250kg, the heat sealing is started, and the heat sealing is controlled by the current. After the secondary vacuum consumable remelting is completed, it is vacuum cooled for 3 hours, and then the void is transferred to the annealing furnace for stress relief annealing within 2 hours to avoid the steel ingot from bursting after demolding. The annealing furnace should be preheated to 300°C for 4 hours to achieve uniform temperature, then heated at a rate of 5°C/h to 800°C for 5 hours, and then cooled at a rate of 5°C/h to 550°C for 5 hours, and then air-cooled.

Test result: The trial-produced 1050mm consumable ingot of 706 alloy weighs 15.5 tons, and there is no hot cracking, and no metallurgical defects such as black spots and white spots. The composition test on the head and tail of the steel ingot showed that the Al and Ti elements at the head and tail have no obvious burning loss. The Al element is 0.27% at the head and 0.24% at the tail. The Ti element is 1.68% at the head and 1.78% at the tail. After the secondary consumable remelted ingot with a diameter of 1050mm is homogenized at high temperature and diffused and annealed, after finishing, forging is arranged to prepare forged bars. After non-destructive inspection of the bar, it was found that there was no abnormal signal at the electroslag remelting joint, indicating that the secondary vacuum consumable remelting can effectively solve the metallurgical quality problem at the 706 alloy electroslag joint.

Example 2

Target 706 alloy composition (by mass percentage):

C 0.011%, Cr 16.2%, Ni 42.2%, Nb 2.88%, Ti1.60%, Al 0.18%, Si 0.02%, Mn 0.02%, P 0.008%, S 0.0004%, Co 0.01%, Mo 0.02%, B 0.003%, Cu 0.05%, Ca 0.001%, N 0.0045%, O 0.0025%, Fe balance.

The specific preparation method is as follows:

Vacuum induction smelting: According to the designed alloy composition requirements, 50% of the return material is weighed according to the required elements of the alloy per unit weight, and the rest is made of new metal raw materials. A 12-ton vacuum induction furnace is used. The upper limit of the melting temperature is 1550℃. After melting, the composition of the molten steel is detected. By adding new metal, the content of Ni in the molten steel is controlled to be about 42.5% by weight, the content of Nb is about 2.92% by weight, and the content of Ti is about 1.65. wt%, Al content is about 0.22wt%, refining under electromagnetic stirring for 40 minutes, the refining temperature is 1480°C, and the tapping temperature is 1500°C. The steel was poured in two times. After completion, the furnace was cooled for 4 hours and then demolded to obtain two 12-ton consumable ingots with a diameter of 820mm, which were then directly annealed. The annealing furnace is preheated to 650°C, and then heated to 900°C at a rate of 25°C/h for 24 hours, and then cooled to 700°C at a rate of 15°C/h for 10 hours, and then air-cooled.

The annealed vacuum induction ingots are turned and flattened to prepare electroslag electrodes.

Electroslag remelting: The diameter of the crystallizer is 1100mm, and the slag system is (CaF ₂ -CaO-Al ₂ O ₃ -TiO ₂ ) quaternary slag. The specific composition is: CaF ₂ 64%, CaO 15%, Al ₂ O ₃ 10 %, TiO ₂ 6%. The steady-state melting rate is 10kg/min, and Ar gas protection at 0.2bar pressure is introduced during the smelting process to prevent the molten steel from contacting oxygen and nitrogen in the air during the smelting process. Before electrode exchange, when the remaining weight is 500kg, adjust the input power and voltage to increase the melting rate, and increase the melting rate with a slope of 0.75kg/min on the basis of the steady-state melting rate. When it reaches 12kg/min, it remains stable until the electroslag electrode is exchanged. . The electrode exchange process maintains the smelting parameters before the exchange, and the exchange time cannot exceed 2 min. After the electrode exchange is completed, after the second electrode melts 300kg, the melting rate is increased by adjusting the input power and voltage, and the melting rate is reduced to 6kg/min at a slope of 1.5kg/min. After the second electrode is left with 500kg, the heat sealing starts.

After the electroslag remelting is completed, the water-cooled crystallizer in the furnace is cooled by water for 4 hours, and after demolding, it is transferred to the annealing furnace for stress relief annealing within 2 hours. The annealing furnace should be preheated to 350°C, kept at 350°C for 24h, then at a rate of 20°C/h to 650°C for 30h, then at a rate of 25°C/h to 900°C for 72h, and then at 30°C/h Cool down to 550°C for 32 hours at a rate of h, then cool in air.

High temperature diffusion annealing of electroslag ingots: install the furnace at a temperature below 550°C for 4 hours, then heat up to 1000°C at a rate of 15°C/h, then heat up to 1150°C at a rate of 25°C/h, hold for 12 hours, and then hold at 25°C/h The temperature was raised to 1250°C for 72 hours at a rate of h, and then cooled to 950°C at a rate of 35°C/h for 8 hours, and then air-cooled.

Electrode forging: The heating temperature before forging of the electroslag ingot with a diameter of 1100mm is 1180℃, and the heating time before forging is 12h. Free forging adopts 3500 ton fast forging machine to draw length in one direction, the single side reduction of each pass is controlled to 30mm, the final forging temperature is 1000℃, and the final forging, turning, and flat head and tail are prepared to a diameter of 820mm. Extremely, used for a vacuum consumable remelting.

One-time vacuum consumable remelting: The diameter of the crystallizer is 920mm, and the consumable remelting is controlled by the melting rate. The steady-state melting rate is controlled to 7.5kg/min; the helium cooling is started after 1800kg of smelting; after the remaining 5000kg, the current is reduced and the melting is adjusted. The speed reaches 7.0kg/min; after the remaining 1500kg, the heat sealing is started, and the heat sealing is controlled by the current. The primary consumable remelting ingot is machined and flat-headed to a diameter of 900mm, which is used for secondary vacuum consumable remelting.

Secondary vacuum self-consumption remelting: 1050mm is selected for the crystallizer, the melting is controlled by the melting rate, and the steady-state melting rate is controlled at 8.5kg/min; after 3000kg of smelting starts, helium cooling is started; after the remaining 5500kg, the current is reduced to adjust the melting rate to 7.5 kg/min; after the remaining 1500kg, the heat sealing is started, and the heat sealing is controlled by the current. After the secondary vacuum consumable remelting is completed, it is vacuum cooled for 8 hours, and then the void is transferred to the annealing furnace for stress relief annealing within 2 hours to prevent the steel ingot from bursting after demoulding. The annealing furnace should be preheated to 750°C for 32 hours to achieve uniform temperature, and then heated at a rate of 35°C/h to 1000°C for 32 hours, and then cooled at a rate of 25°C/h to 750°C for 32 hours, and then air-cooled to achieve the target Ingot casting.

Test result: The trial-produced 1050mm consumable ingot of 706 alloy weighs 15.5 tons, and there is no hot cracking, and no metallurgical defects such as black spots and white spots. The composition test on the head and tail of the steel ingots shows that there is no obvious burning loss of Al and Ti elements at the head and tail. Al element is 0.24% for the head and 0.19% for the tail, Ti element is 1.68% for the head and 1.50 for the tail. %. After the three-time consumable remelted ingot with a diameter of 1050mm is homogenized at high temperature and diffused and annealed, it is arranged for forging after polishing to prepare forged bars. After non-destructive testing of the bar, it was found that there was no abnormal signal at the electroslag remelting joint, indicating that the three-time vacuum consumable remelting can effectively solve the metallurgical quality problem at the 706 alloy electroslag joint.

Example 3

Target 706 alloy composition (by mass percentage):

C 0.015%, Cr 16.6%, Ni 40.0%, Nb 3.18%, Ti 1.51%, Al 0.10%, Si 0.01%, Mn 0.15%, P 0.007%, S 0.0005%, Co 0.03%, Mo 0.03%, B 0.005%, Cu0 0.04%, Ca 0.002%, N 0.004%, O 0.003%, Fe balance.

The specific preparation method is as follows:

Vacuum induction smelting: According to the designed alloy composition requirements, 60% of the return material is weighed according to the required elements of the alloy per unit weight, and the rest is made of new metal raw materials. A 12-ton vacuum induction furnace is used. The upper limit of the melting temperature is 1350℃. After melting, the composition of the molten steel is detected. By adding new metal, the content of Ni in the molten steel is controlled to be about 40.5wt%, the content of Nb is about 3.2wt%, and the content of Ti is about 1.57 wt%, Al content is about 0.15wt%, refining under electromagnetic stirring for 100 minutes, the refining temperature is 1400°C, and the tapping temperature is 1450°C. The steel was poured in two times. After completion, the furnace was cooled for 4 hours and then demolded to obtain two 12-ton consumable ingots with a diameter of 820mm, which were then directly annealed. The annealing furnace is pre-heated to 750°C, and then heated to 1000°C at a rate of 40°C/h for 24 hours, then cooled to 800°C at a rate of 30°C/h for 30 hours, and then air-cooled.

Electroslag remelting: The diameter of the crystallizer is 1100mm, and the slag system is (CaF2-CaO-Al2O3-TiO2) quaternary slag. The specific composition is: CaF264%, CaO 15%, Al2O3 8%, TiO2 1%. The steady-state melting rate is 5kg/min, and Ar gas protection at 0.2bar pressure is introduced during the smelting process to prevent the molten steel from contacting oxygen and nitrogen in the air during the smelting process.

Before the electrode exchange, when the remaining weight is 600kg, adjust the input power and voltage to increase the melting rate. On the basis of the steady-state melting rate, increase the melting rate with a slope of 2kg/min. When it reaches 20kg/min, it will remain stable until the electroslag electrode is exchanged. The electrode exchange process maintains the smelting parameters before the exchange, and the exchange time cannot exceed 2 min. After the electrode exchange is completed, after the second electrode melts 500kg, the melting rate is increased by adjusting the input power and voltage, and the melting rate is reduced to 15kg/min at a slope of 2kg/min. When the second electrode remains 500kg, the heat sealing starts.

After the electroslag remelting is completed, the water-cooled crystallizer in the furnace is cooled by water for 4 hours, and the mold is transferred to the annealing furnace for stress relief annealing within 1 hour. The annealing furnace should be preheated to 550°C, kept at 400°C for 24h, then at a rate of 15°C/h to 750°C for 24h, then at a rate of 18°C/h to 1000°C for 36h, and then at 15°C/h It is cooled to 750°C for 12 hours at a rate of h, and then air-cooled.

High temperature diffusion annealing of electroslag ingots: install the furnace at a temperature below 550°C for 4 hours, then heat up to 950°C at a rate of 10°C/h, then heat up to 1100°C at a rate of 15°C/h, hold for 12 hours, and then at 20°C/h The temperature was raised to 1200°C for 48 hours at a rate of h, and then cooled to 850°C at a rate of 15°C/h for 24 hours, and then air-cooled.

Electrode forging: The heating temperature before forging of the electroslag ingot with a diameter of 1100mm is 1150℃, and the heating time before forging is 8h. The free forging adopts a 3500 tons fast forging machine to draw length in one direction, and the unilateral reduction of each pass is controlled to 5mm, and the final forging temperature is 900℃. The final forging, turning, and flat head and tail are prepared to a diameter of 820mm. Extremely, used for a vacuum consumable remelting.

One-time vacuum consumable remelting: The diameter of the crystallizer is 920mm, the consumable remelting is controlled by the melting rate, and the steady-state melting rate is controlled to 5.0kg/min; the helium cooling is started after 1500kg is melted; the current is reduced after the remaining 2000kg to adjust the melting The speed reaches 6.0kg/min; after the remaining 250kg, the heat sealing is started, and the heat sealing is controlled by the current. The primary consumable remelting ingot is machined and flat-headed to a diameter of 900mm, which is used for secondary vacuum consumable remelting.

Secondary vacuum self-consumption remelting: The mold is 1050mm, the melting is controlled by the melting rate, and the steady-state melting rate is controlled to 6.5kg/min; the helium cooling is started after 1500kg is melted; the current is reduced after the remaining 3000kg to adjust the melting rate to 6.0 kg/min; after the remaining 1000kg, the heat sealing is started, and the heat sealing is controlled by the current. After the secondary vacuum consumable remelting is completed, vacuum cooling is performed for 5 hours, and then the void is transferred to the annealing furnace for stress relief annealing within 2 hours to prevent the ingot from bursting after demolding. The annealing furnace should be preheated to 450°C for 24 hours to achieve uniform temperature, then heated at a rate of 25°C/h to 900°C for 24 hours, and then cooled at a rate of 35°C/h to 600°C for 12 hours, and then air-cooled to achieve the target Ingot casting.

Test results: The trial-produced 1050mm consumable ingot of 706 alloy weighs 15.8 tons. There is no hot cracking and no metallurgical defects such as black spots and white spots. The composition test on the head and tail of the steel ingots shows that there is no obvious burning loss of Al and Ti elements at the head and tail. The Al element is 0.16% for the head and 0.12% for the tail. The Ti element is 1.60% for the head and 1.46 for the tail. %. After the three-time consumable remelted ingot with a diameter of 1050mm is homogenized at high temperature and diffused and annealed, it is arranged for forging after polishing to prepare forged bars. After non-destructive testing of the bar, it was found that there was no abnormal signal at the electroslag remelting joint, indicating that the three-time vacuum consumable remelting can effectively solve the metallurgical quality problem at the 706 alloy electroslag joint.

Comparative example

The comparative example is used to illustrate the preparation method of 706 alloy (a consumable ingot with a diameter of 920 mm) prepared by a triple preparation process.

The target 706 alloy composition is the same as the 706 alloy composition of Example 1 (by mass percentage):

C0.018%, Cr 15.8%, Ni 41.5%, Nb3.01%, Ti 1.72%, Al 0.25%, Si 0.02%, Mn 0.01%, P 0.006%, S 0.0006%, Co 0.02%, Mo 0.01%, B 0.004%, Cu 0.02%, Ca 0.004%, N 0.005%, O 0.002%, Fe balance.

The specific preparation method is as follows:

Vacuum induction smelting: According to the designed alloy composition requirements, 40% of the return material is weighed according to the required elements of the alloy per unit weight, and the rest is made of new metal raw materials. A 12-ton vacuum induction furnace is used to prepare two 12-ton consumable ingots with a diameter of 820mm. The upper melting temperature is 1550℃. After melting, the composition of the molten steel is detected. By adding new metal, the content of Ni in the molten steel is controlled to about 42.0wt%. The Nb content is about 3.10wt%, the Ti content is about 1.82wt%, and the Al content is about 0.35wt%. Electromagnetic stirring is used for 40 minutes; the refining temperature is 1480°C, and the tapping temperature is 1500°C. After pouring the steel, the furnace is cooled for 4 hours and then demoulded, and then directly subjected to annealing treatment. The annealing furnace is preheated to 650°C, and then heated to 900°C at a rate of 25°C/h for 24 hours, and then cooled to 600°C at a rate of 15°C/h for 10 hours, and then air-cooled.

The annealed vacuum induction ingots are turned, and the ends are flattened to prepare electroslag electrodes.

Electroslag remelting: The diameter of the crystallizer is 1100mm, and the slag system is (CaF ₂ -CaO-Al ₂ O ₃ -TiO ₂ ) quaternary slag. The specific composition is: CaF ₂ 70%, CaO 15% _{, Al 2} O _{3 15%} , TiO ₂ 6%. The steady-state melting rate is 10kg/min, and Ar gas protection at 0.2bar pressure is introduced during the smelting process to prevent the molten steel from contacting oxygen and nitrogen in the air during the smelting process. Before electrode exchange, when the remaining weight is 600kg, adjust the input power and voltage to increase the melting rate, and increase the melting rate with a slope of 0.55kg/min on the basis of the steady-state melting rate. When it reaches 15kg/min, it will remain stable until the electroslag electrode is exchanged. . The electrode exchange process maintains the smelting parameters before the exchange, and the exchange time cannot exceed 2 min. After the electrode exchange is completed, after the second electrode melts 200kg, the melting rate is increased by adjusting the input power and voltage, and the melting rate is reduced to 10kg/min at a slope of 0.75kg/min. When the second electrode remains 500kg, the heat sealing starts.

After the electroslag remelting is completed, it should be cooled by passing water in a water-cooled crystallizer in the furnace for 4 hours, and transferred to the annealing furnace for stress relief annealing within 0.5 hours after demolding. The annealing furnace should be preheated to 450°C, kept at 450°C for 24h, then at a rate of 15°C/h to 650°C for 4h, then at a rate of 25°C/h to 950°C for 12h, and then at 15°C/h Cool down to 600°C for 12 hours at a rate of h, then cool in air.

High temperature diffusion annealing of electroslag ingots: install the furnace at a temperature below 550°C for 4 hours, then heat up to 950°C at a rate of 10°C/h, then heat up to 1100°C at a rate of 15°C/h, hold for 12 hours, and then at 20°C/h The temperature was raised to 1190°C for 48 hours at a rate of h, and then cooled to 850°C for 24 hours at a rate of 15°C/h, and then air-cooled.

Electrode forging: The heating temperature before forging of the electroslag ingot with a diameter of 1100mm is 1150℃, and the heating time before forging is 10h. The free forging adopts a 3500 ton fast forging machine to draw the length in one direction. The unilateral reduction of each pass is controlled to 25mm, and the final forging temperature is 900℃. The consumable electrode with a diameter of 820mm is finally prepared by forging, turning, and flat head. .

Self-consumable remelting: The diameter of the crystallizer is 920mm, and the self-consumable remelting is controlled by the melting rate. The steady-state melting rate is controlled at 5.5kg/min; the helium cooling is started after the smelting of 1000kg; after the remaining 2000kg, the current is reduced to adjust the melting rate to 4.0kg/min; after the remaining 500kg, the heat sealing is started, and the heat sealing is controlled by the current. After the consumable remelting is completed, it is cooled in vacuum for 3 hours, and then the void is transferred to the annealing furnace for stress relief annealing within 2 hours to prevent the ingot from bursting after demoulding. The annealing furnace should be preheated to 450°C for 8 hours to achieve uniform temperature, and then heated at a rate of 10°C/h to 850°C for 24 hours, and then cooled at a rate of 15°C/h to 600°C for 12 hours, and then air-cooled.

Test results: 706 alloy 920mm consumable ingots trial-produced by the triple smelting process, weighing 15.2 tons, and no hot cracking; the composition test on the head and tail of the steel ingot, the test results show that the head and tail Al and Ti elements burned significantly, and Al The element is 0.29% in the head and 0.19% in the tail, and the Ti element is 1.62% in the head and 1.80% in the tail. After the secondary consumable ingot with a diameter of 920mm is homogenized, diffused and annealed at high temperature, it is polished and forged to prepare forged bars. The bars were inspected by non-destructive flaw detection, and abnormal signals were found at the electroslag remelting joints, and an obvious black spot defect was found at the joints after anatomy.

This specific embodiment is only an explanation of the present invention, and is not a limitation of the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contribution as needed, but as long as the rights of the present invention The scope of the requirements is protected by the patent law.

Claims

A large-size high-niobium high-temperature 706 alloy ingot, characterized in that the large-size high-niobium high-temperature alloy ingot has a diameter of more than 800mm, and the chemical composition of the large-size high-niobium high-temperature 706 alloy ingot is calculated by mass percentage. The ingredients are:

C≤0.02wt%, Cr 15.5～16.5wt%, Ni 40.0～43.0wt%, Nb 2.8～3.2wt%, Ti 1.5～1.8wt%, Al 0.1～0.3wt%, Si≤0.10wt%, Mn≤0.20 wt%, P≤0.015wt%, S≤0.0013wt%, Co≤0.30wt%, Mo≤0.20wt%, B≤0.006wt%, Cu≤0.30wt%, Ca≤0.005wt%, N≤0.006wt% , O≤0.005wt%, Fe balance.
The smelting process of a large-size high-niobium high-temperature 706 alloy ingot according to claim 1, characterized in that it comprises the following steps:

Vacuum induction smelting: According to the designed alloy composition requirements, the pure metal raw materials and/or return materials are weighed according to the required elements of the alloy per unit weight as raw materials, and vacuum induction smelting is performed to control the Ni content in the smelting mother liquor to 40.0-43.0wt%. Nb content is 2.80～3.3wt%, Ti content is 0.5～2.0wt%, Al content is 0.2～0.5wt%, and multiple vacuum induction ingots with the same composition are poured;

Exchange electroslag remelting: the same number of electroslag electrodes are prepared by using the vacuum induction ingots made; all the prepared electroslag electrodes are used, and the exchange electroslag remelting is performed under argon protection. The slag system used is ( CaF 2 -CaO-Al 2 O 3 -TiO 2 ) quaternary slag, (CaF 2 -CaO-Al 2 O 3 -TiO 2 ) quaternary slag contains 60～75wt% of CaF 2 and 10～25wt% of CaO. Al 2 O 3 accounts for 8 to 13 wt%, and TiO 2 accounts for 1 to 10 wt%; after the exchange electroslag remelting is completed, it is cooled and demolded to obtain an electroslag ingot:

Primary vacuum consumable remelting: the demolded electroslag ingot is subjected to primary annealing, secondary annealing, forging and drawing to a predetermined size to obtain a primary consumable electrode, wherein the secondary annealing temperature is higher than the primary annealing temperature; then use A consumable electrode is remelted once in vacuum;

Secondary vacuum consumable remelting: the primary consumable remelted ingots obtained by the primary vacuum consumable remelting, car light, flat head and tail, to obtain a secondary consumable electrode; then use the secondary consumable electrode for secondary vacuum Consumable remelting to prepare ingots of target diameter.
The smelting process according to claim 2, characterized in that, in the vacuum induction melting step, the melting temperature is 1300-1550°C, after the raw materials are melted, refining is carried out under electromagnetic stirring for 15-120 minutes, and the refining temperature is 1350-1550°C. ; Then, after cooling for 1-10 hours, demoulding to obtain a vacuum induction ingot; repeat the vacuum induction melting process many times to have multiple vacuum induction ingots with the same composition.
The smelting process according to claim 2, characterized in that the method of preparing the electroslag electrode is directly stress-relieving annealing for each vacuum induction ingot. During annealing, the temperature is pre-heated to 600-800°C, and then the temperature is 5 to 45°C. Heat up to 800～1000℃ and keep it warm for 4～32h at a rate of 1～35℃/h, then cool to 600～800℃ and keep it for 4～32h at a rate of 1～35℃/h, then air cooling, and then car light, flat head and tail, that is Electroslag electrode.
The smelting process according to claim 2, characterized in that when performing exchange electroslag remelting, the slag system used is (CaF 2 -CaO-Al 2 O 3 -TiO 2 ) quaternary slag, (CaF 2- (CaO-Al 2 O 3 -TiO 2 ) In the quaternary slag, CaF 2 accounts for 60 to 75 wt %, CaO accounts for 10 to 25 wt %, Al 2 O 3 accounts for 8 to 13 wt %, and TiO 2 accounts for 1 to 5 wt %.
The smelting process according to claim 5, characterized in that the steady-state melting rate of electroslag remelting is controlled to be 5-15kg/min; and, before each electrode exchange, when the remaining weight of the current electrode is 500kg-1000kg, On the basis of the steady-state melting rate, increase the melting rate to 12-25kg/min with a slope of 0.5-2kg/min, keep it stable until the electroslag electrode is exchanged, and the electrode exchange process maintains the smelting parameters before the exchange, and the exchange time does not exceed 2min; After each electrode exchange is completed, when the next electrode melts 100kg～500kg, reduce the melting rate with a slope of 0.5～2kg/min to a steady state melting rate of 5～15kg/min, continue to remelt until the last one After the remaining 200-600kg of the electrode is left, heat-sealing starts; after the exchange of electroslag remelting, it is cooled for 2-10h, demolded, and an electroslag ingot is obtained.
The smelting process according to claim 2, characterized in that, in performing multiple vacuum consumable remelting steps, the demolded electroslag ingot is subjected to primary annealing, secondary annealing, and forging to a predetermined size to obtain a primary The concrete realization of the consumable electrode is as follows,

For electroslag ingots, an annealing is started within 0.5-2h after demolding. Specifically, it is preheated to 300-550℃, held for 12-32h to achieve uniform temperature, and then heated at a rate of 1-25℃/h to 600～ Hold at 750°C for 4～32h, then heat up to 800～1000°C at a rate of 5～35℃/h and keep it at 800～1000℃ for 4～32h, then cool to 550～750℃ at a rate of 1～35℃/h and keep it at 4～32h, then Air cooling

Perform secondary annealing on the electroslag ingot after primary annealing, specifically, heating up to 800-1000°C at a rate of 5 to 35°C/h, and then heating up to 1050 to 1150°C at a rate of 1 to 25°C/h 4～32h, then heat up at a rate of 1～25℃/h to 1150～1250℃ and keep for 24～72h, then cool at a rate of 1～35℃/h to 800～950℃ and keep it for 4～32h, then air cooling;

For the electroslag ingot after secondary annealing, it is heated to 1100～1180℃ before forging, and the heating time before forging is 4～12h. The free forging adopts a fast forging machine of more than 3000 tons to draw the length in one direction, and each pass is pressed down on one side. The amount is controlled at 5～30mm, and the final forging temperature is 850～1000℃;

For the steel ingot after free forging and drawing, the head and tail are flattened, and a consumable electrode is obtained.
The smelting process according to claim 2, characterized in that when performing a vacuum consumable remelting, the steady-state melting rate is controlled to be 3.5～7.5kg/min; the helium cooling is started after 800～2000kg smelting is started; the remaining 1500～ After 5000kg, the current is reduced to adjust the melting rate to 3.0～7.0kg/min; after the remaining 200～1000kg, the heat sealing is started to obtain a self-consumable remelting ingot.
The smelting process according to claim 2, characterized in that when performing secondary vacuum consumable remelting, the steady-state melting rate is controlled to be 4.0-8.5kg/min; after the smelting starts, 1000-3000kg is passed through helium for cooling; After 2000～5500kg, reduce the current to adjust the melting rate to 3.0～7.5kg/min; after the remaining 250～1500kg, start heat sealing.
The smelting process according to claim 2, characterized in that, after the secondary consumable remelting is completed, vacuum cooling is performed for 1 to 8 hours, and then stress relief annealing is started within 2 hours; during annealing, it is preheated to 300 to 750°C and kept warm. Achieve uniform temperature in 4～32h, then heat up to 800～1000℃ at a rate of 5～50℃/h, keep it for 4～32h, then cool to 550～750℃ at a rate of 1～35℃/h and keep it for 4～32h, Then, air cooling is used to obtain an ingot of the target diameter.