Preparation method for improving carbide morphology of Ni-Fe-based high-temperature alloy bar billet for ultra-supercritical thermal power generating unit pipeline

Abstract

The invention discloses a preparation method for improving the carbide morphology of a Ni-Fe-based high-temperature alloy bar billet for an ultra-supercritical thermal power generating unit pipeline. The Ni-Fe-based high-temperature alloy bar billet 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 Fe. The preparation method comprises the following steps: S1, obtaining a uniform and compact high-temperature alloy cast ingot through vacuum induction and vacuum self consumption; s2, cogging is conducted, specifically, the high-temperature alloy cast ingot obtained in S1 is put into a heating furnace to be heated, the temperature is slowly increased to 1170 DEG C, the heat preservation time is longer than or equal to 150 h after the cast ingot reaches the temperature, then furnace cooling is conducted to 1100-1150 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 dispersively distributed carbides is finally obtained by controlling a diffusion channel of the carbides during heat treatment after cogging.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal processing, in particular to a method for preparing carbide morphology of a Ni-Fe-based high-temperature alloy rod blank for use in pipelines of ultra-supercritical thermal power units. Background Art

[0002] In order to achieve the "dual carbon goals", my country is accelerating the construction of a new power system with new energy as the main body. The relevant national documents clearly point out that "a number of coal-based power generation technologies with higher efficiency, greater flexibility and lower emissions should be developed to consolidate the leading position of coal-fired power technology". Ultra-supercritical coal-fired power generation is the key direction of power innovation technology, but after the steam parameters are improved, the service conditions of high-temperature hot parts are more stringent, and Ni-Fe-based alloy materials with better performance than traditional heat-resistant steel are required. Ultra-supercritical thermal power unit technology is an important development measure proposed by my country to address coal energy and carbon emissions issues.

[0003] The excellent performance of Ni-Fe-based high-temperature alloys is derived from the pinning effect of precipitated phases such as carbides, so more carbon is added during the composition design. However, due to the high carbon content, it is easy to combine with metal elements to form different types of carbides, which are unevenly distributed within the grain and at the grain boundaries. The uneven distribution will cause the "cracking" behavior of the rod billet during the subsequent welding process, causing the component to fail, which will seriously restrict the rapid development of ultra-supercritical power generation technology. Therefore, it is urgent to solve the optimization problem of carbides in Ni-Fe-based high-temperature alloy rod billets. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a Ni-Fe based high temperature alloy rod for improving the carbide morphology of an ultra-supercritical thermal power unit pipeline, so as to solve the problems raised in the above background technology.

[0005] To achieve the above objectives, the present invention provides the following technical solutions: The purpose of the present invention is to provide a method for preparing carbide morphology of Ni-Fe based high temperature alloy rod blank for pipeline of ultra-supercritical thermal power unit to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a preparation method for improving the carbide morphology of a Ni-Fe-based high-temperature alloy rod blank for an ultra-supercritical thermal power unit pipeline, 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 Fe, comprising the following steps:

[0007] S1. Vacuum induction + vacuum self-consumption to obtain uniform and dense high-temperature alloy ingots;

[0008] S2, open the blank, put the high temperature alloy ingot obtained in S1 into a heating furnace for heating, slowly raise the temperature to 1170°C, keep the ingot warm for ≥150h, then cool the furnace to 1100°C-1150°C for insulation, and perform open forging, the starting forging temperature is ≥950°C, and the final forging temperature is ≥850°C;

[0009] S3, forming, subjecting the ingot obtained in S2 to 2-5 fire forming forging, the forging heating temperature is 1000℃-1230℃, and the deformation amount of each forging is 30%-45%;

[0010] S4, air cooling the forged rod obtained in step S3 to obtain a Ni-Fe-based high-temperature alloy rod blank that can be directly used for ultra-supercritical thermal power unit parts.

[0011] Preferably, the specification of the high-temperature alloy bar billet is Φ200mm-Φ500mm.

[0012] Preferably, the billet forging described in S2 adopts continuous re-forging, and the deformation amount of each fire is 15%-35%.

[0013] Preferably, the forming stage described in S3 is divided into 2-5 fires, the heating temperature of the second fire is 1200-1230°C, the first 2-4 fires are radial upsetting and drawing, the deformation is 30%-45%, the heating temperature of the 3rd-4th fires is 1020°C-1060°C, the last 1-2 fires are drawing forming, the deformation of each fire is 15%-25%, and the heating temperature range is 1000°C-1040°C.

[0014] Preferably, the final two-fire forging reduction rate is ≥80 mm / s, and the last 1-2 fire forging adopts a round-to-round deformation method.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention prepares Ni-Fe-based high-temperature alloy rod blanks by double vacuum smelting + rapid forging, and finally obtains Ni-Fe-based high-temperature alloy rod blanks with dispersed carbides by controlling the diffusion channel of carbides during heat treatment after blanking.

[0016] Compared with the prior art, the beneficial effects of the present invention are: preparing Ni-Fe-based high-temperature alloy rod blanks by double vacuum smelting + rapid forging, and finally obtaining Ni-Fe-based high-temperature alloy rod blanks with dispersed carbides by controlling the diffusion channel of carbides during heat treatment after blanking. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1These are the carbide height magnifications of the Φ204mm rod blank, where: (a) is 100× for the edge; (b) is R / 2100×; and (c) is 100× for the core. 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] See also Figure 1 The present invention provides a technical solution: Example 1

[0020] A method for preparing carbide morphology of Ni-Fe-based high-temperature alloy rod blank for pipelines of ultra-supercritical thermal power units, comprising the following materials:

[0021] 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

[0022] , the rest is Fe, comprising the following steps:

[0023] S1. Vacuum induction + vacuum self-consumption to obtain uniform and dense high-temperature alloy ingots;

[0024] S2, open the blank, put the high temperature alloy ingot obtained in S1 into a heating furnace for heating, slowly raise the temperature to 1170°C, keep the ingot warm for 150h, then cool the furnace to 1100°C for insulation, and perform open forging, the starting forging temperature is ≥950°C, and the final forging temperature is ≥850°C;

[0025] S3, forming, subjecting the ingot obtained in S2 to 2-5 fire forming forging, the forging heating temperature is 1000℃-1060℃, and the deformation amount of each forging is 30%-45%;

[0026] S4, the forged rod obtained in step S3 is air-cooled to obtain a Ni-Fe-based high-temperature alloy rod blank that can be directly used for ultra-supercritical thermal power unit parts.

[0027] Among them, the specification of high-temperature alloy rod billet is Φ204mm.

[0028] Among them, the billet forging in S2 adopts continuous re-forging, and the deformation amount of each fire is 25%.

[0029] Among them, the forming stage in S3 is divided into 2-5 fires. The first 2-4 fires are radial upsetting and drawing with a deformation of 40%. The heating temperature of the 2nd-4th fires is 1040℃. The last 1-2 fires are drawing forming, with a deformation of 20% in each fire and a heating temperature of 1020℃.

[0030] Among them, the final two-fire forging reduction rate is 120mm / s, and the last 1-2 fire forging adopts a round-to-round deformation method.

[0031] The obtained Ni-Fe-based high-temperature alloy rod blank for the pipeline of the ultra-supercritical thermal power unit has a carbide grade of 6-7 as a whole according to GB / T14999.6.

[0032] Example 2

[0033] A method for preparing carbide morphology of Ni-Fe-based high-temperature alloy rod blank for pipelines of ultra-supercritical thermal power units, comprising the following materials:

[0034] 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 Fe, comprising the following steps:

[0035] S1. Vacuum induction + vacuum self-consumption to obtain uniform and dense high-temperature alloy ingots;

[0036] S2, open the blank, put the high temperature alloy ingot obtained in S1 into a heating furnace for heating, slowly raise the temperature to 1170°C, keep the ingot warm for 150h, then cool the furnace to 1100°C for insulation, and perform open forging, the starting forging temperature is ≥950°C, and the final forging temperature is ≥850°C;

[0037] S3, forming, subjecting the ingot obtained in S2 to 2-5 fire forming forging, the forging heating temperature is 1000℃-1230℃, and the deformation amount of each forging is 30%-45%;

[0038] S4, the forged rod obtained in step S3 is air-cooled to obtain a Ni-Fe-based high-temperature alloy rod blank that can be directly used for ultra-supercritical thermal power unit parts.

[0039] Among them, the specification of high-temperature alloy rod billet is Φ204mm.

[0040] Among them, the billet forging in S2 adopts continuous re-forging, and the deformation amount of each fire is 25%.

[0041] Among them, the forming stage in S3 is divided into 2-5 fires, the heating temperature of the second fire is 1210℃, the first 2-4 fires are radial upsetting and drawing with a deformation of 35%, the heating temperature of the 3rd-4th fires is 1040℃, and the last 1-2 fires are drawing forming, with a deformation of 20% in each fire and a heating temperature of 1020℃-1040℃.

[0042] Among them, the final two-fire forging reduction rate is 120mm / s, and the last 1-2 fire forging adopts a round-to-round deformation method.

[0043] The obtained Ni-Fe-based high-temperature alloy rod blank for the pipeline of the ultra-supercritical thermal power unit has carbide grade 1-2 as a whole according to GB / T14999.6 rating.

[0044] 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 the pipeline of the ultra-supercritical thermal power unit, while in Example 1, only S3 does not specifically limit the second fire temperature.

[0045] Experimental results: The carbide distribution of the Ni-Fe-based high-temperature alloy bar blank finally obtained in Example 2 is more dispersed and meets the requirements, while the carbide distribution of the Ni-Fe-based high-temperature alloy bar blank finally obtained in Example 1 is aggregated and does not meet the requirements.

[0046] Conclusion: The present invention prepares Ni-Fe-based high-temperature alloy rod blanks by double vacuum smelting + rapid forging, and finally obtains Ni-Fe-based high-temperature alloy rod blanks with dispersed carbides by controlling the diffusion channel of carbides during heat treatment after blanking.

[0047] 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 a Ni-Fe-based high-temperature alloy rod for improving the carbide morphology of an ultra-supercritical thermal power unit pipeline, 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 Fe, characterized in that: The method comprises the following steps: S1. Vacuum induction + vacuum self-consumption to obtain uniform and dense high-temperature alloy ingots; S2. Forging: placing the high temperature alloy ingot obtained in S1 into a heating furnace for heating, slowly heating the temperature to 1170°C, keeping the temperature for ≥150h after the ingot reaches the temperature, then cooling the furnace to 1100°C-1150°C for forging, starting forging temperature ≥950°C, and final forging temperature ≥850°C; S3, forming: the ingot obtained in S2 is subjected to 2-5 fire forming forging, the forging heating temperature is 1000℃-1230℃, and the deformation amount of each forging is 30%-45%; S4. Air-cooling the forged rod obtained in S3 to obtain a Ni-Fe-based high-temperature alloy rod blank that can be directly used for ultra-supercritical thermal power unit parts.

2. The method for preparing carbide morphology of Ni-Fe-based high-temperature alloy rod blank for improving pipelines of ultra-supercritical thermal power units according to claim 1, characterized in that: The specifications of the high-temperature alloy bar blank are Φ200mm-Φ500mm.

3. The method for preparing carbide morphology of Ni-Fe based high temperature alloy rod for improving pipeline of ultra-supercritical thermal power unit 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 15%-35%.

4. The method for preparing carbide morphology of Ni-Fe based high temperature alloy rod for improving pipeline of ultra-supercritical thermal power unit according to claim 1, characterized in that: The forming stages described in S3 are divided into 2-5 fires, the heating temperature of the second fire is 1200-1230°C, the first 2-4 fires are radial upsetting and drawing, the deformation is 30%-45%, the heating temperature of the 3rd-4th fires is 1020°C-1060°C, the last 1-2 fires are drawing forming, the deformation of each fire is 15%-25%, and the heating temperature range is 1000°C-1040°C.

5. The method for preparing carbide morphology of Ni-Fe based high temperature alloy rod for improving pipeline of ultra-supercritical thermal power unit according to claim 1, characterized in that: The final two-fire forging reduction rate is ≥80mm / s, and the last 1-2 fire forging adopts a round-to-round deformation method.

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