Preparation method of Ni-Fe-based high-temperature alloy bar billet grain boundary primary carbide for optimizing ultra-supercritical thermal power generating unit pipeline

Abstract

The invention discloses a preparation method of a Ni-Fe-based high-temperature alloy bar billet grain boundary primary carbide for optimizing an ultra-supercritical thermal power generating unit pipeline. The Ni-Fe-based high-temperature alloy bar billet grain boundary primary carbide comprises the following materials: 0.045-0.055% of C, 18.0-20.0% of Cr, 0.4-0.6% of Mo and 0.2-0.4% of W; the high-temperature alloy comprises the following components in percentage by weight: 0.002 to 0.005 percent of B, 1.5 to 2.5 percent of Co, 25.0 to 27.0 percent of Fe, 1.9 to 2.1 percent of Al, 2.0 to 2.2 percent of Ti and the balance of Ni. The preparation method comprises the following steps: S1, obtaining a uniform and compact high-temperature alloy cast ingot through vacuum induction and vacuum consumable melting; s2, cogging is conducted, specifically, the high-temperature alloy cast ingot obtained in S1 is put into a natural gas heating furnace to be heated, the temperature is slowly increased to 1230 DEG C, the heat preservation time is longer than or equal to 100 h after the cast ingot reaches the temperature, then furnace cooling is conducted to 1050-1100 DEG C, heat preservation is conducted, cogging forging is conducted, the initial forging temperature is larger than or equal to 950 DEG C, and the final forging temperature is larger than or equal to 850 DEG C; according to the method, the Ni-Fe-based high-temperature alloy bar billet is prepared in a double-vacuum smelting and fast forging forming mode, and the Ni-Fe-based high-temperature alloy bar billet with uniform grain boundary primary carbide distribution is finally obtained by controlling the deformation process of the forming stage.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal processing, in particular to a method for preparing primary carbides at grain boundaries of Ni-Fe based high temperature alloy rod blanks for optimizing pipelines of ultra-supercritical thermal power units. Background Art

[0002] Ultra-supercritical thermal power unit technology is an important development measure proposed by my country to address coal energy and carbon emissions issues, and it is also the only way to achieve the "dual carbon" goal in the future. Ultra-supercritical thermal power units rely on the steam temperature to increase from 600°C to 650°C, and the power generation efficiency and comprehensive utilization rate of coal are significantly improved. However, due to the harsh service environment, some of the original unit pipes, rotors and other materials are no longer applicable. Therefore, the technology of ultra-supercritical thermal power units depends to a large extent on the development of material technology. Considering the demand for higher performance and economy of materials, a class of Ni-Fe-based high-temperature alloys has been developed in the industry.

[0003] Ni-Fe-based high-temperature alloys have become important components of key components of ultra-supercritical thermal power units such as high-temperature superheaters / reheaters, main steam and reheat steam pipelines, and turbine rotors due to their excellent high-temperature creep resistance, oxidation corrosion resistance, coal ash erosion resistance, and low cost. In order to optimize the microstructure and properties of the alloy, a small amount of grain boundary strengthening elements such as carbon are added to form carbides that pin the grain boundaries by combining with metal elements, thereby inhibiting grain growth behavior. Carbides are divided into primary and secondary carbides due to their precipitation temperature. Primary carbides have a higher precipitation temperature and larger size. They are generally precipitated during the smelting process. The precipitation of such carbides will seriously affect the welding performance of high-temperature alloys. When a large number of primary carbides gather at the grain boundaries, liquid cracks will easily form around the carbides, resulting in larger defects and a significant decrease in fatigue endurance performance. Therefore, it is urgent to solve the precipitation problem of primary carbides at grain boundaries. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing primary carbides at grain boundaries of Ni-Fe based high temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power units, so as to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing primary carbides at grain boundaries of Ni-Fe-based high-temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power units, comprising the following materials: comprising the following materials: C: 0.045-0.055, Cr: 18.0-20.0, Mo: 0.4-0.6, W: 0.2-0.4; B: 0.002-0.005, Co: 1.5-2.5, Fe: 25.0-27.0, Al: 1.9-2.1, Ti: 2.0-2.2, and the rest is Ni, comprising the following steps:

[0006] S1. Vacuum induction + vacuum consumable melting to obtain uniform and dense high-temperature alloy ingots;

[0007] S2, open the blank, put the high temperature alloy ingot obtained in S1 into a natural gas heating furnace for heating, slowly raise the temperature to 1230°C, keep the ingot warm for ≥100h, then cool the furnace to 1050°C-1100°C for insulation, and perform open forging, the starting forging temperature is ≥950°C, and the final forging temperature is ≥850°C;

[0008] S3, forming, subjecting the ingot obtained in S2 to 2-5 fire forming forging, the forging heating temperature is 1000℃-1050℃, and the deformation amount of each forging is 35%-50%;

[0009] S4. The forged rod obtained in step S3 is subjected to peeling and flaw detection to obtain a Ni-Fe-based high-temperature alloy rod blank that can be directly used for pipelines of supercritical thermal power units.

[0010] Preferably, the high-temperature alloy bar billet has a specification of Φ150mm-Φ500mm.

[0011] Preferably, the billet forging described in S2 adopts continuous re-forging, and the deformation amount of each fire is 20%-40%.

[0012] Preferably, the forming stage described in S3 is divided into 2-5 fires, the first 2-4 fires are radial upsetting and drawing, the deformation amount of each fire is 25%-45%, and the heating temperature is 1020℃-1050℃, and the last 1-2 fires are drawing forming, the deformation amount of each fire is 20%-30%, and the heating temperature ranges from 1000℃-1040℃.

[0013] Preferably, the final two-fire forging reduction rate is ≥50 mm / s, and the last 1-2 fire forging adopts a round-to-round deformation method.

[0014] Preferably, the cooling method of the forged rod blank obtained in S4 is air cooling, so as to obtain a Ni-Fe-based high-temperature alloy rod blank which can be directly used for pipelines of supercritical thermal power units.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention prepares a Ni-Fe-based high-temperature alloy rod blank by means of double vacuum smelting + rapid forging, and finally obtains a Ni-Fe-based high-temperature alloy rod blank with uniform distribution of primary carbides at the grain boundaries by controlling the deformation process in the forming stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the carbide of Φ250mm rod blank.

[0017] Among them: (a) is the edge 100×; (b) is R / 2100×; (c) is the center 100×. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The object of the present invention is to provide a method for preparing primary carbides at grain boundaries of Ni-Fe based high temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power units, so as to solve the problems raised in the above background technology.

[0020] like Figure 1 To achieve the above objectives, the present invention provides the following technical solution: a method for preparing primary carbides at grain boundaries of Ni-Fe based high temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power units, so as to solve the problems raised in the above background technology.

[0021] To achieve the above object, the present invention provides the following technical solution: a method for preparing primary carbides at grain boundaries of Ni-Fe-based high-temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power units, comprising the following materials: comprising the following materials: C: 0.045-0.055, Cr: 18.0-20.0, Mo: 0.4-0.6, W: 0.2-0.4; B: 0.002-0.005, Co: 1.5-2.5, Fe: 25.0-27.0, Al: 1.9-2.1, Ti: 2.0-2.2, and the rest is Ni, comprising the following steps:

[0022] S1. Vacuum induction + vacuum consumable melting to obtain uniform and dense high-temperature alloy ingots;

[0023] S2, open the blank, put the high temperature alloy ingot obtained in S1 into a natural gas heating furnace for heating, slowly raise the temperature to 1230°C, keep the ingot warm for ≥100h, then cool the furnace to 1050°C-1100°C for insulation, and perform open forging, the starting forging temperature is ≥950°C, and the final forging temperature is ≥850°C;

[0024] S3, forming, subjecting the ingot obtained in S2 to 2-5 fire forming forging, the forging heating temperature is 1000℃-1050℃, and the deformation amount of each forging is 35%-50%;

[0025] S4. The forged rod obtained in step S3 is subjected to peeling and flaw detection to obtain a Ni-Fe-based high-temperature alloy rod blank that can be directly used for pipelines of supercritical thermal power units.

[0026] Wherein, the specification of the high temperature alloy bar blank is Φ150mm-Φ500mm.

[0027] The blank forging described in S2 adopts continuous re-forging, and the deformation amount of each firing is 20%-40%.

[0028] Among them, the forming stage described in S3 is divided into 2-5 fires, the first 2-4 fires are radial upsetting and drawing, the deformation amount of each fire is 25%-45%, and the heating temperature is 1020℃-1050℃, and the last 1-2 fires are drawing forming, the deformation amount of each fire is 20%-30%, and the heating temperature range is 1000℃-1040℃.

[0029] Among them, the final two-fire forging reduction rate is ≥50mm / s, and the last 1-2 fire forging adopts a circle-circle deformation method.

[0030] The cooling method of the forged bar blank obtained in S4 is air cooling, and the Ni-Fe-based high-temperature alloy bar blank which can be directly used for the pipeline of supercritical thermal power unit is obtained. The bar blank is graded as primary carbide 1-2 according to GB / T14999.6 standard.

[0031] Example 1

[0032] A method for preparing primary carbides at grain boundaries of Ni-Fe-based high-temperature alloy rod blanks for optimizing pipelines of ultra-supercritical thermal power units, comprising the following materials: C: 0.05, Cr: 19.0, Mo: 0.5, W: 0.3; B: 0.0035, Co: 2.0, Fe: 26.0, Al: 2.0, Ti: 2.1, and the rest is Ni, comprising the following steps:

[0033] S1. Vacuum induction + vacuum consumable melting to obtain uniform and dense high-temperature alloy ingots;

[0034] S2, open the blank, put the high temperature alloy ingot obtained in S1 into a natural gas heating furnace for heating, slowly raise the temperature to 1230°C, keep the ingot warm for 100 hours, then cool the furnace to 1080°C for insulation, and perform open forging, the starting forging temperature is ≥950°C, and the final forging temperature is ≥850°C;

[0035] S3, forming, subjecting the ingot obtained in S2 to 2-5 fire forming forging, the forging heating temperature is 1000℃-1050℃, and the deformation amount of each forging is 45%;

[0036] S4. The forged rod obtained in step S3 is subjected to peeling and flaw detection to obtain a Ni-Fe-based high-temperature alloy rod blank that can be directly used for pipelines of supercritical thermal power units.

[0037] Wherein, the specification of the high-temperature alloy rod blank is Φ250mm.

[0038] The billet forging described in S2 adopts continuous re-forging, and the deformation amount of each fire is 30%.

[0039] Among them, the forming stage described in S3 is divided into 2-5 fires, the first 2-4 fires are radial upsetting and drawing, the heating temperature is 1030°C, and the last 1-2 fires are drawing forming, and the heating temperature range is 1010°C.

[0040] Among them, the final two-fire forging reduction rate is 60mm / s, and the last 1-2 fire forging adopts a circle-circle deformation method.

[0041] The cooling method of the forged bar blank obtained in S4 is air cooling, and the Ni-Fe-based high-temperature alloy bar blank that can be directly used for supercritical thermal power unit pipelines is obtained. The bar blank is graded as a carbide of grade 5-6 according to GB / T14999.6 standard.

[0042] Example 2

[0043] A method for preparing primary carbides at grain boundaries of Ni-Fe-based high-temperature alloy rod blanks for optimizing pipelines of ultra-supercritical thermal power units, comprising the following materials: C: 0.05, Cr: 19.0, Mo: 0.5, W: 0.3; B: 0.0035, Co: 2.0, Fe: 26.0, Al: 2.0, Ti: 2.1, and the rest is Ni, comprising the following steps:

[0044] S1. Vacuum induction + vacuum consumable melting to obtain uniform and dense high-temperature alloy ingots;

[0045] S2, open the blank, put the high temperature alloy ingot obtained in S1 into a natural gas heating furnace for heating, slowly raise the temperature to 1230°C, keep the ingot warm for 100 hours, then cool the furnace to 1080°C for insulation, and perform open forging, the starting forging temperature is ≥950°C, and the final forging temperature is ≥850°C;

[0046] S3, forming, subjecting the ingot obtained in S2 to 2-5 fire forming forging, the forging heating temperature is 1000℃-1050℃, and the deformation amount of each forging is 45%;

[0047] S4. The forged rod obtained in step S3 is subjected to peeling and flaw detection to obtain a Ni-Fe-based high-temperature alloy rod blank that can be directly used for pipelines of supercritical thermal power units.

[0048] Wherein, the specification of the high-temperature alloy rod blank is Φ250mm.

[0049] The billet forging described in S2 adopts continuous re-forging, and the deformation amount of each fire is 30%.

[0050] Among them, the forming stage described in S3 is divided into 2-5 fires, the first 2-4 fires are radial upsetting and drawing, the deformation amount of each fire is 35%, the heating temperature is 1030℃, and the last 1-2 fires are drawing forming, the deformation amount of each fire is 25%, and the heating temperature range is 1010℃.

[0051] Among them, the final two-fire forging reduction rate is 60mm / s, and the last 1-2 fire forging adopts a circle-circle deformation method.

[0052] The cooling method of the forged bar blank obtained in S4 is air cooling, and the Ni-Fe-based high-temperature alloy bar blank which can be directly used for the pipeline of supercritical thermal power unit is obtained. The bar blank is graded as primary carbide 1-2 according to GB / T14999.6 standard.

[0053] Comparative Example 1 and Example 2: In Example 2, the steps of the present invention are strictly followed to prepare the Ni-Fe-based high-temperature alloy rod blank for an ultra-supercritical thermal power unit, while in Example 1, only S3 directly performs 2-5 forming forging on the ingot, and the deformation amount of each fire is not strictly controlled.

[0054] Experimental results: The primary carbide distribution at the grain boundary of the Ni-Fe-based high-temperature alloy rod blank finally obtained in Example 2 is more uniform and meets the requirements, while the carbides of the Ni-Fe-based high-temperature alloy rod blank finally obtained in Example 1 are uneven and have a large number, which does not meet the requirements.

[0055] Conclusion: The present invention prepares Ni-Fe-based high-temperature alloy billet by double vacuum smelting + rapid forging, and finally obtains Ni-Fe-based high-temperature alloy billet with uniform distribution of primary carbides at grain boundaries and meeting the requirements by controlling the deformation process in the forming stage.

[0056] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing primary carbides at grain boundaries of Ni-Fe-based high-temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power units, comprising the following materials: C: 0.045-0.055, Cr: 18.0-20.0, Mo: 0.4-0.6, W: 0.2-0.4; B: 0.002-0.005, Co: 1.5-2.5, Fe: 25.0-27.0, Al: 1.9-2.1, Ti: 2.0-2.2, and the rest is Ni, comprising the following steps: S1. Vacuum induction + vacuum consumable melting to obtain uniform and dense high-temperature alloy ingots; S2, open the blank, put the high temperature alloy ingot obtained in S1 into a natural gas heating furnace for heating, slowly raise the temperature to 1230°C, keep the ingot warm for ≥100h, then cool the furnace to 1050°C-1100°C for insulation, and perform open forging, the starting forging temperature is ≥950°C, and the final forging temperature is ≥850°C; S3, forming, subjecting the ingot obtained in S2 to 2-5 fire forming forging, the forging heating temperature is 1000℃-1050℃, and the deformation amount of each forging is 35%-50%; S4. The forged rod obtained in step S3 is subjected to peeling and flaw detection to obtain a Ni-Fe-based high-temperature alloy rod blank that can be directly used for pipelines of supercritical thermal power units.

2. The method for preparing primary carbides at grain boundaries of Ni-Fe-based high-temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power plants according to claim 1, characterized in that: The specifications of the high-temperature alloy bar blank are Φ150mm-Φ500mm.

3. The method for preparing primary carbides at grain boundaries of Ni-Fe-based high-temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power plants according to claim 1, characterized in that: The billet forging described in S2 adopts continuous re-forging, and the deformation amount of each fire is 20%-40%.

4. The method for preparing primary carbides at grain boundaries of Ni-Fe-based high-temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power plants according to claim 1, characterized in that: The forming stage described in S3 is divided into 2-5 fires. The first 2-4 fires are radial upsetting and drawing, with a deformation of 25%-45% in each fire and a heating temperature of 1020℃-1050℃. The last 1-2 fires are drawing and forming, with a deformation of 20%-30% in each fire and a heating temperature range of 1000℃-1040℃.

5. The method for preparing primary carbides at grain boundaries of Ni-Fe-based high-temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power units according to claim 1, characterized in that: The final two-fire forging reduction rate is ≥50mm / s, and the last 1-2 fire forging adopts a round-to-round deformation method.

6. The method for preparing primary carbides at grain boundaries of Ni-Fe-based high-temperature alloy rods for optimizing pipelines of ultra-supercritical thermal power plants according to claim 1, characterized in that: The cooling method of the forged rod blank obtained in S4 is air cooling, and the resulting Ni-Fe-based high-temperature alloy rod blank can be directly used for pipelines of supercritical thermal power units.

Images