A method for preparing a Ni-Fe-based high-temperature alloy ingot for an ultra-supercritical thermal power unit

Abstract

The application discloses a preparation method of Ni-Fe based high-temperature alloy ingot for ultra-supercritical thermal power generating unit, and belongs to the field of nonferrous metallurgy. The mass percentage of the Ni-Fe based high-temperature alloy ingot is as follows: C: 0.03-0.04, Al: 1.30-1.50, Ti: 2.00-2.20, Si: <=0.10, Cr: 15.5-16.5, Mo: 0.7-0.9, W: 0.1-0.3, B: 0.002-0.005, Fe: 41.0-43.0, Nb: <=0.05, Ta: <=0.05, and the rest is Ni. The application prepares an induction electrode through a vacuum induction + vacuum casting smelting mode, reduces the burning loss of Al and Ti elements in the vacuum induction smelting process, and improves the yield of Al and Ti elements. The alloying process of Al and Ti elements is completed in the subsequent vacuum consumable smelting process, so that the accurate control of the components is facilitated. Finally, the Ni-Fe based high-temperature alloy ingot for ultra-supercritical thermal power generating unit with accurate components and high density is obtained.

Description

Technical Field

[0001] This invention relates to the field of alloy ingot preparation technology, specifically to a method for preparing Ni-Fe-based high-temperature alloy ingots for ultra-supercritical thermal power units. Background Technology

[0002] Coal, as my country's primary energy source, plays a crucial role in the country's energy supply and determines the dominant position of coal-fired power generation in my country's power structure. Although coal-fired power generation brings carbon emissions and environmental pressure, given my country's national conditions and energy structure, it will remain the main source of electricity supply for a considerable period. Therefore, given the inability to change emissions, gradually improving energy efficiency is a crucial measure to solve current energy problems. Ultra-supercritical thermal power currently possesses the most mature technology, with 600℃ commercial coal-fired power generation already achieving large-scale commercial application. To address environmental and carbon emission pressures, it is necessary to further improve coal-fired power generation efficiency and clean coal combustion technology, which places higher demands on the materials used in ultra-supercritical thermal power units. Currently, the main material used in ultra-supercritical thermal power units is heat-resistant steel. However, with the gradually increasing parameters of 650℃ ultra-supercritical thermal power units, heat-resistant steel can no longer fully meet the operating temperature requirements, inevitably leading to a shift in material selection towards high-temperature alloys.

[0003] The Ni-Fe based superalloy described in this invention is suitable for 650℃ ultra-supercritical thermal power units. Using Al and Ti as strengthening elements ensures the alloy exhibits excellent comprehensive performance at 650℃, meeting the requirements for service materials in 650℃ ultra-supercritical thermal power units. However, high Al and Ti content affects alloy smelting. Al and Ti elements are prone to burn-off and reaction with the crucible material, making precise control difficult. Therefore, it is urgent to solve these problems. Attached Figure Description

[0004] Figure 1 The diagram shows an induction casting ingot: 1: Induction casting ingot; 2: Al and Ti alloy; 3: Base pad with the same composition. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing Ni-Fe-based high-temperature alloy ingots for ultra-supercritical thermal power units, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing Ni-Fe-based superalloy ingots for ultra-supercritical thermal power units, comprising the following materials: C: 0.03-0.04%, Si: ≤0.10%, Cr: 15.5-16.5%, Mo: 0.7-0.9%, W: 0.1-0.3%, B: 0.002-0.005%, Fe: 41.0-43.0%, Nb: ≤0.05%, Ta: ≤0.05%, with the remainder being Ni, and including the following steps:

[0008] S1. The consumable electrode is prepared by vacuum induction + vacuum casting. After the surface is polished and the oxide scale is removed, it is welded to the auxiliary electrode and fixed to the smelting position of the vacuum consumable furnace. Arc melting is started. All elements except Al and Ti are added to the vacuum induction furnace in sequence. The vacuum is drawn and the power is slowly increased. After the metal is melted, the refining stage begins, and electromagnetic stirring is carried out at the same time.

[0009] S2. After refining is completed, vacuum casting is carried out after all elements except Al and Ti meet the target composition. The ingot mold contains Al and Ti alloys that are connected to the base pad of the same composition.

[0010] S3. In the later stage of the heat-sealing process, the melting rate is gradually reduced during the heat-sealing process to finally obtain the Ni-Fe based high-temperature alloy ingot.

[0011] Preferably, in the casting process of step S1, the ingot mold contains a spacer of the same composition that is connected to the Al and Ti alloys.

[0012] Preferably, in step S1, the melting rate is controlled at 3.3 to 4.0 kg / min after arc initiation to ensure that the vacuum degree is ≤0.5 Pa during the steady-state self-consumable melting process.

[0013] Preferably, in step S1, the refining stage requires adjusting the power to keep the temperature within the range of 1450–1480°C and refining for 60 minutes.

[0014] Preferably, the Al and Ti alloy in step S1 is obtained by self-consumable melting after briquetting, and the mass fraction ratio of Al to Ti is (0.6~0.75) / 1.

[0015] Preferably, in step S1, the mass ratio of the built-in Al and Ti alloy to the mass of the cast molten steel is (3.3~3.7) / 100.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] 1. It avoids contact between Al and Ti in the vacuum induction melting process and refractory materials such as crucibles, thus reducing the burn-off of Al and Ti elements;

[0018] 2. The alloying process of Al and Ti elements is carried out simultaneously during the vacuum self-consumable melting process, which makes it easier to control the composition precisely. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1

[0021] A method for preparing Ni-Fe-based superalloy ingots for ultra-supercritical thermal power units, comprising the following materials: C: 0.03, Si: ≤0.10, Cr: 15.5, Mo: 0.7, W: 0.1; B: 0.002, Fe: 41.0, Nb: ≤0.05, Ta: ≤0.05, with the remainder being Ni, and including the following steps:

[0022] S1. The consumable electrode is prepared by vacuum induction + vacuum casting. After the surface is polished and the oxide scale is removed, it is welded to the auxiliary electrode and fixed to the smelting position of the vacuum consumable furnace. Arc melting is started. All elements except Al and Ti are added to the vacuum induction furnace in sequence. The vacuum is drawn and the power is slowly increased. After the metal is melted, the refining stage begins, and electromagnetic stirring is carried out at the same time.

[0023] S2. After refining is completed, vacuum casting is carried out after all elements except Al and Ti meet the target composition. The ingot mold contains Al and Ti alloys that are connected to the base pad of the same composition.

[0024] S3. In the later stage of the heat-sealing process, the melting rate is gradually reduced during the heat-sealing process to finally obtain the Ni-Fe based high-temperature alloy ingot.

[0025] Furthermore, in the casting process of step S1, the ingot mold contains a spacer of the same composition that is connected to the Al and Ti alloys.

[0026] Furthermore, in step S1, the melting rate is controlled at 3.3 / min after arc initiation to ensure that the vacuum degree is ≤0.5pa during the steady-state self-consumable melting process.

[0027] Furthermore, in the refining stage of step S1, the power needs to be adjusted to keep the temperature within the range of 1450℃, and the refining time is 60 minutes.

[0028] Furthermore, the Al and Ti alloy in step S1 is obtained by self-consumable melting after briquetting, and the mass fraction ratio of Al to Ti is (0.67) / 1.

[0029] Furthermore, in step S1, the mass ratio of the built-in Al and Ti alloy to the mass of the cast molten steel is (3.5) / 100.

[0030] The composition of the Ni-Fe based superalloy ingot prepared according to the present invention is shown in Table 1. It meets the target composition requirements, the composition of the ingot is consistent from beginning to end, and the Al and Ti elements are highly consistent with the target addition values, with no obvious burn-off.

[0031] Table 1. Composition of the first and last parts of Ni-Fe based superalloy ingots

[0032]

[0033] Conclusion: This invention prepares Ni-Fe based superalloy ingots through vacuum induction and vacuum casting, avoiding contact between Al and Ti during the vacuum induction melting process and refractory materials such as crucibles, thus reducing the burn-off of Al and Ti elements; the alloying process of Al and Ti elements is carried out simultaneously during the vacuum consumable melting process, which makes it easier to control the composition precisely.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a Ni-Fe-based high-temperature alloy ingot for ultra-supercritical thermal power generating units, comprising the following materials: C: 0.03-0.04, Si: ≤0.10, Cr: 15.5-16.5, Mo: 0.7-0.9, W: 0.1-0.3; B: 0.002-0.005, Fe: 41.0-43.0, Nb: ≤0.05, Ta: ≤0.05, and the balance being Ni, characterized in that, It comprises the following steps: S1, a consumable electrode is prepared by a vacuum induction + vacuum casting method, after surface polishing, the oxide skin is removed, and then the consumable electrode is welded with an auxiliary electrode and fixed to a vacuum consumable furnace smelting position, arc striking is performed for smelting, other elements except Al and Ti are sequentially added to the vacuum induction furnace, vacuum is extracted and the power is slowly increased to, after the metal is melted, the refining stage is started, and electromagnetic stirring is performed at the same time; S2, after the refining is completed and the other elements except Al and Ti meet the target composition, vacuum casting is performed, an Al and Ti alloy connected with a bottom pad of the same composition is pre-embedded in the ingot mold; S3, a hot sealing top is performed in the later stage of vacuum consumable, the melting rate is gradually and slowly reduced during the hot sealing top process, and finally a Ni-Fe-based high-temperature alloy ingot is obtained; The Al and Ti alloy in the step S1 is obtained by uniformly mixing and briquetting and then consumably smelting, and the mass fraction ratio of Al to Ti is (0.60~0.75) / 1; The mass ratio of the embedded Al and Ti alloy to the cast steel liquid in the step S1 is (3.3~3.7) / 100.

2. The Ni-Fe-based high-temperature alloy ingot preparation method for ultra-supercritical thermal power generating units according to claim 1, characterized in that: The casting process in the step S1 is that the ingot mold is embedded with a same-component pad connected with the Al and Ti alloy.

3. The Ni-Fe-based high-temperature alloy ingot preparation method for ultra-supercritical thermal power generating units according to claim 1, characterized in that: In the step S1, the melting rate after arc striking is controlled to be 3.3~4.0 kg / min, so as to ensure that the vacuum degree is less than or equal to 0.5 pa during the stable consumable smelting process.

4. The Ni-Fe-based high-temperature alloy ingot preparation method for ultra-supercritical thermal power generating units according to claim 1, characterized in that: In the step S1, the power needs to be adjusted to make the temperature in the range of 1450~1480℃ during the refining stage, and the refining is performed for 60 min.

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