Heat treatment method for large-scale 04Cr13Ni5Mo steel forging of runner

Abstract

This invention provides a heat treatment method for a large 04Cr13Ni5Mo steel forging, relating to the field of steel heat treatment technology. The method includes sequentially performing post-forging heat treatment and quenching and tempering heat treatment on the forging blank. The post-forging heat treatment includes sequentially performing a first normalizing treatment, a second normalizing treatment, a third normalizing treatment, and a first tempering treatment. The normalizing temperature for the first normalizing treatment is 1030-1050℃, the normalizing temperature for the second normalizing treatment is 1010-1020℃, the normalizing temperature for the third normalizing treatment is 970-990℃, and the tempering temperature for the first tempering treatment is 610-630℃. The large forging obtained using the heat treatment method provided by this invention has finer grain size, better strength, and better toughness.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for steel, and more specifically, to a heat treatment method for a large 04Cr13Ni5Mo steel wheel forging. Background Technology

[0002] 04Cr13Ni5Mo steel is a high-performance stainless steel suitable for manufacturing impulse turbine runners. With continuous technological innovation, existing small impulse turbine runners can no longer meet the requirements, necessitating the development of large impulse turbine runners, which in turn requires the development of large 04Cr13Ni5Mo steel runner forgings. These large impulse turbine runners have diameters exceeding 4 meters and must withstand the impact of extremely high water heads and erosion from sediment during operation, while driving the generator rotor at high speeds. This necessitates that the 04Cr13Ni5Mo steel large runner forgings possess excellent mechanical properties (strength, toughness, etc.). However, due to the large size and weight of these forgings, and the numerous heat treatment processes involved in forging, internal structural defects can occur, affecting their mechanical properties. Therefore, improving the mechanical properties of 04Cr13Ni5Mo steel large runner forgings has become an urgent problem to be solved. Summary of the Invention

[0003] The problem this invention addresses is: how to improve the mechanical properties of large 04Cr13Ni5Mo steel wheel forgings.

[0004] To address the aforementioned problems, this invention provides a heat treatment method for a large 04Cr13Ni5Mo steel forging, comprising sequentially performing post-forging heat treatment and quenching and tempering heat treatment on the forging blank; wherein, the post-forging heat treatment includes sequentially performing a first normalizing treatment, a second normalizing treatment, a third normalizing treatment, and a first tempering treatment; the quenching and tempering heat treatment includes sequentially performing a quenching treatment, a second tempering treatment, and a third tempering treatment; the normalizing temperature of the first normalizing treatment is 1030-1050℃, the normalizing temperature of the second normalizing treatment is 1010-1020℃, the normalizing temperature of the third normalizing treatment is 970-990℃, and the tempering temperature of the first tempering treatment is 610-630℃.

[0005] Optionally, the first normalizing treatment includes:

[0006] The forging blank is held at 640-660℃ for 14-16 hours, then heated to 1030-1050℃ and held for 35-37 hours, and finally air-cooled to 130-160℃ to obtain the first intermediate forging.

[0007] Optionally, the second normalizing treatment includes:

[0008] The first intermediate forging is held at 130-160℃ for 19-21 hours, then heated to 540-560℃ and held for 14-16 hours, then heated to 1010-1020℃ and held for 35-37 hours, and finally air-cooled to 130-160℃ to obtain the second intermediate forging.

[0009] Optionally, the third normalizing treatment includes:

[0010] The second intermediate forging is held at 130-160℃ for 19-21 hours, then heated to 540-560℃ and held for 9-11 hours, then heated to 970-990℃ and held for 35-37 hours, and finally air-cooled to 130-160℃ to obtain the third intermediate forging.

[0011] Optionally, the first tempering process includes:

[0012] The third intermediate forging is held at 130-160℃ for 19-21 hours, then heated to 610-630℃ and held for 44-46 hours. It is then cooled to 190-200℃ at a rate of 9-11℃ / h and air-cooled to room temperature to obtain the fourth intermediate forging.

[0013] Optionally, the quenching process includes:

[0014] The fourth intermediate forging is heated to 980-1020℃ and held for 16-22 hours, then cooled to 130-160℃ by blowing air to obtain the fifth intermediate forging.

[0015] Optionally, the second tempering process includes:

[0016] The fifth intermediate forging is heated to 560-600℃ and held for 22-36 hours, then air-cooled to 130-160℃ to obtain the sixth intermediate forging.

[0017] Optionally, the third tempering process includes:

[0018] The sixth intermediate forging is heated to 580-610℃ and held for 28-44 hours. After cooling, a large rotary forging is obtained.

[0019] Optionally, the diameter of the forging blank is 4m or more.

[0020] Optionally, the composition of the forging blank, by weight percentage, includes: C: 0.01-0.04%, Si: 0-0.6%, Mn: 0.50-1.00%, Cr: 12.0-13.0%, Mo: 0.40-0.80%, Ni: 4.5-6.0%, V: 0-0.07%, Cu: 0-0.50%, W: 0-0.10%, S: 0-0.008%, P: 0-0.020%, with the balance being Fe and unavoidable impurities; wherein the sum of the mass fractions of V, Cu, and W is 0-0.50%.

[0021] Compared with existing technologies, the heat treatment method for large wheel forgings provided by this invention, by controlling the normalizing temperature of the first normalizing treatment to 1030-1050℃, enables the forging to fully austenitize and ensures the complete dissolution of some carbides, allowing some micro-segregated elements to undergo short-range diffusion, thus achieving uniform microstructure and improving the strength and toughness of the large wheel forgings. By controlling the normalizing temperature of the second normalizing treatment to 1010-1020℃, which is slightly lower than the first normalizing temperature, further refinement of the grain size of the forging can be ensured, and some carbides can be dissolved. The incorporation of austenite further enhances the strength and toughness of large rotary forgings. By controlling the normalizing temperature of the third normalizing treatment to 970-990℃, the normalizing temperature of the third normalizing treatment is further reduced, allowing some fine carbides to disperse within the austenite, acting as grain boundaries and further refining the grain size of the forging, which is beneficial for further improving the strength and toughness of the large rotary forgings. By controlling the tempering temperature of the first tempering treatment to 610-630℃, the microstructure in the forging undergoes a reverse austenite transformation, which effectively improves the toughness of the forging and also helps to reduce the hardness of the forging, facilitating subsequent rough machining. In summary, the large rotary forgings obtained by the heat treatment method of this invention have finer grain size, better strength, and better toughness. Attached Figure Description

[0022] Figure 1 Image showing the metallographic structure of the large wheel forging obtained in Example 1;

[0023] Figure 2 The image shows the metallographic structure of the large wheel forging obtained in Example 2;

[0024] Figure 3 Images showing the metallographic structure of the large wheel forging obtained in Example 3;

[0025] Figure 4 Image showing the metallographic structure of the large wheel forging prepared in Comparative Example 1;

[0026] Figure 5 The image shows the metallographic structure of the large wheel forging prepared in Comparative Example 2. Detailed Implementation

[0027] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0029] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the description below. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0030] It should be noted that the 04Cr13Ni5Mo steel large turbine forging in this invention refers to a 04Cr13Ni5Mo steel turbine forging with a diameter exceeding 4m.

[0031] This invention provides a heat treatment method for a large 04Cr13Ni5Mo steel forging, comprising sequentially performing post-forging heat treatment and quenching and tempering heat treatment on the forging blank; wherein, the post-forging heat treatment includes sequentially performing a first normalizing treatment, a second normalizing treatment, a third normalizing treatment, and a first tempering treatment; the quenching and tempering heat treatment includes sequentially performing a quenching treatment, a second tempering treatment, and a third tempering treatment; the normalizing temperature of the first normalizing treatment is 1030-1050℃, the normalizing temperature of the second normalizing treatment is 1010-1020℃, the normalizing temperature of the third normalizing treatment is 970-990℃, and the tempering temperature of the first tempering treatment is 610-630℃.

[0032] The heat treatment method for large wheel forgings provided in this invention, by controlling the normalizing temperature of the first normalizing treatment to 1030-1050℃, can fully austenitize the microstructure of the forging and ensure the complete dissolution of some carbides, allowing some micro-segregated elements to undergo short-range diffusion, thus achieving uniform microstructure composition and improving the strength and toughness of the large wheel forging. By controlling the normalizing temperature of the second normalizing treatment to 1010-1020℃, which is slightly lower than the normalizing temperature of the first normalizing treatment, it can ensure further refinement of the grain size of the forging and allow some carbides to incorporate into the austenite. The first tempering treatment, conducted at 610-630℃, induces a reverse austenite transformation in the forging structure, effectively improving its toughness and reducing its hardness, thus facilitating subsequent rough machining. In summary, the large wheel forging obtained using the heat treatment method provided in this invention exhibits finer grain size, better strength, and better toughness. By controlling the normalizing temperature of the third normalizing treatment to 970-990℃, the normalizing temperature is further reduced, allowing some fine carbides to disperse within the austenite, acting as grain boundaries and further refining the grain size of the forging, which is beneficial for further improving the strength and toughness of the large wheel forging.

[0033] It should be noted that the forging blank in the embodiments of the present invention is forged from 04Cr13Ni5Mo steel ingot, and the initial forging temperature during the forging process is 1180℃ and the final forging temperature is 850℃.

[0034] In some embodiments of the present invention, the first normalizing treatment includes:

[0035] The forging blank is held at 640-660℃ for 14-16 hours, heated to 1030-1050℃ at a rate of 40-60℃ / h, held for 35-37 hours, and then air-cooled to 130-160℃ to obtain the first intermediate forging.

[0036] In this embodiment, the forging blank is kept at 640-660℃ for 14-16 hours to avoid cracking due to excessively low temperature during operation; the temperature is increased to 1030-1050℃ at a rate of 40-60℃ / h to ensure recrystallization of the forging.

[0037] In some embodiments of the present invention, the second normalizing treatment includes:

[0038] The first intermediate forging is held at 130-160℃ for 19-21 hours, heated to 540-560℃ at a rate of 20-40℃ / h, held for 14-16 hours, then heated to 1010-1020℃ at a rate of 40-60℃ / h, held for 35-37 hours, and air-cooled to 130-160℃ to obtain the second intermediate forging.

[0039] In this embodiment, holding the first intermediate forging at 130-160℃ for 19-21 hours ensures sufficient transformation of the core structure, reduces the content of retained austenite, and is beneficial to further improve the strength of the forging. Heating to 540-560℃ at a relatively slow rate (20-40℃ / h) and holding for 14-16 hours can effectively prevent excessive thermal stress in the forging. Heating to 1010-1020℃ at a relatively fast rate (40-60℃ / h) can effectively increase the nucleation rate of the material and increase the number of nuclei per unit volume, thereby facilitating further grain refinement.

[0040] In some embodiments of the present invention, the third normalizing treatment includes:

[0041] The second intermediate forging is held at 130-160℃ for 19-21 hours, then heated to 540-560℃ at a rate of 20-40℃ / h, held for 9-11 hours, then heated to 970-990℃ at a rate of 40-60℃ / h, held for 35-37 hours, and then air-cooled to 130-160℃ to obtain the third intermediate forging.

[0042] In this embodiment, holding the second intermediate forging at 130-160℃ for 19-21 hours ensures sufficient transformation of the core structure, reduces the content of retained austenite, and is beneficial to further improve the strength of the forging. Heating to 540-560℃ at a relatively slow rate (20-40℃ / h) and holding for 9-11 hours can effectively prevent excessive thermal stress in the forging. Heating to 970-990℃ at a relatively fast rate (40-60℃ / h) can effectively increase the nucleation rate of the material and increase the number of nuclei per unit volume, thereby facilitating further grain refinement.

[0043] In some embodiments of the present invention, the first tempering process includes:

[0044] The third intermediate forging is held at 130-160℃ for 19-21 hours, heated to 610-630℃ at a rate of 30-40℃ / h, held for 44-46 hours, cooled to 190-200℃ at a rate of 9-11℃ / h, and air-cooled to room temperature to obtain the fourth intermediate forging.

[0045] In this embodiment, the third intermediate forging is held at 130-160℃ for 19-21 hours to ensure sufficient transformation of the core structure of the forging, reduce the content of residual austenite, and further improve the strength of the forging. The forging is heated to 610-630℃ at a relatively slow rate (30-40℃ / h) and held for 44-46 hours to effectively prevent excessive thermal stress in the forging.

[0046] In some embodiments of the present invention, the quenching process includes:

[0047] The fourth intermediate forging is heated to 980-1020℃ and held for 16-22 hours, then cooled to 130-160℃ by blowing air to obtain the fifth intermediate forging.

[0048] In some embodiments of the present invention, the second tempering process includes:

[0049] The fifth intermediate forging is heated to 560-600℃ and held for 22-36 hours, then air-cooled to 130-160℃ to obtain the sixth intermediate forging.

[0050] In some embodiments of the present invention, the third tempering process includes:

[0051] The sixth intermediate forging is heated to 580-610℃ and held for 28-44 hours. After cooling, a large rotary forging is obtained.

[0052] In some embodiments of the present invention, the diameter of the forging blank is 4m or more.

[0053] In some embodiments of the present invention, the composition of the forging blank, by weight percentage, includes: C: 0.01-0.04%, Si: 0-0.6%, Mn: 0.50-1.00%, Cr: 12.0-13.0%, Mo: 0.40-0.80%, Ni: 4.5-6.0%, V: 0-0.07%, Cu: 0-0.50%, W: 0-0.10%, S: 0-0.008%, P: 0-0.020%, with the balance being Fe and unavoidable impurities; wherein the sum of the mass fractions of V, Cu, and W is 0-0.50%.

[0054] The present invention will be further described below with reference to specific embodiments.

[0055] Example 1

[0056] A1. First normalizing treatment: The forging blank is held at 650℃ for 15 hours, heated to 1040℃ at a rate of 50℃ / h, held for 36 hours, and air-cooled to 145℃ to obtain the first intermediate forging; wherein, the diameter of the forging blank is 4900mm and the height is 1120mm; the composition of the forging blank by weight percentage includes: C: 0.02%, Si: 0.3%, Mn: 0.70%, Cr: 12.5%, Mo: 0.60%, Ni: 5.0%, V: 0.03%, Cu: 0.20%, W: 0.05%, S: 0.004%, P: 0.010%, with the balance being Fe and unavoidable impurities.

[0057] A2. Second normalizing treatment: The first intermediate forging is held at 145°C for 20 hours, heated to 550°C at a rate of 30°C / h, held for 15 hours, then heated to 1020°C at a rate of 50°C / h, held for 36 hours, and air-cooled to 145°C to obtain the second intermediate forging.

[0058] A3. Third normalizing treatment: The second intermediate forging is held at 145°C for 20 hours, heated to 550°C at a rate of 30°C / h, held for 10 hours, then heated to 980°C at a rate of 50°C / h, held for 36 hours, and air-cooled to 145°C to obtain the third intermediate forging.

[0059] A4. First tempering treatment: The third intermediate forging is held at 145°C for 20 hours, heated to 620°C at a rate of 35°C / h, held for 45 hours, cooled to 200°C at a rate of 10°C / h, and air-cooled to room temperature to obtain the fourth intermediate forging.

[0060] A5. Quenching treatment: The fourth intermediate forging is heated to 1000℃ and held for 19 hours, then cooled to 145℃ by blowing air to obtain the fifth intermediate forging.

[0061] A6. Second tempering treatment: The fifth intermediate forging is heated to 580°C, held for 29 hours, and then air-cooled to 145°C to obtain the sixth intermediate forging.

[0062] A7. Third tempering treatment: The sixth intermediate forging is heated to 600°C and held for 36 hours. After cooling, a large rotary forging is obtained.

[0063] Example 2

[0064] A1. First normalizing treatment: The forging blank is held at 640℃ for 16 hours, heated to 1030℃ at a rate of 40℃ / h, held for 37 hours, and air-cooled to 130℃ to obtain the first intermediate forging; wherein, the diameter of the forging blank is 4600mm and the height is 1120mm; the composition of the forging blank by weight percentage includes: C: 0.02%, Si: 0.3%, Mn: 0.70%, Cr: 12.5%, Mo: 0.60%, Ni: 5.0%, V: 0.03%, Cu: 0.20%, W: 0.05%, S: 0.004%, P: 0.010%, with the balance being Fe and unavoidable impurities.

[0065] A2. Second normalizing treatment: The first intermediate forging is held at 130°C for 21 hours, heated to 540°C at a rate of 20°C / h, held for 16 hours, then heated to 1010°C at a rate of 40°C / h, held for 37 hours, and air-cooled to 130°C to obtain the second intermediate forging.

[0066] A3. Third normalizing treatment: The second intermediate forging is held at 130°C for 21 hours, heated to 540°C at a rate of 20°C / h, held for 11 hours, then heated to 970°C at a rate of 40°C / h, held for 37 hours, and air-cooled to 130°C to obtain the third intermediate forging.

[0067] A4. First tempering treatment: The third intermediate forging is held at 130°C for 21 hours, heated to 610°C at a rate of 30°C / h, held for 46 hours, cooled to 190°C at a rate of 9°C / h, and air-cooled to room temperature to obtain the fourth intermediate forging.

[0068] A5. Quenching treatment: The fourth intermediate forging is heated to 980°C and held for 22 hours, then cooled to 130°C by blowing air to obtain the fifth intermediate forging.

[0069] A6. Second tempering treatment: The fifth intermediate forging is heated to 560°C, held for 36 hours, and then air-cooled to 130°C to obtain the sixth intermediate forging.

[0070] A7. Third tempering treatment: The sixth intermediate forging is heated to 580°C and held for 44 hours. After cooling, a large rotary forging is obtained.

[0071] Example 3

[0072] A1. First normalizing treatment: The forging blank is held at 660℃ for 14 hours, heated to 1050℃ at a rate of 60℃ / h, held for 35 hours, and air-cooled to 160℃ to obtain the first intermediate forging; wherein, the diameter of the forging blank is 4200mm and the height is 1120mm; the composition of the forging blank by weight percentage includes: C: 0.02%, Si: 0.3%, Mn: 0.70%, Cr: 12.5%, Mo: 0.60%, Ni: 5.0%, V: 0.03%, Cu: 0.20%, W: 0.05%, S: 0.004%, P: 0.010%, with the balance being Fe and unavoidable impurities.

[0073] A2. Second normalizing treatment: The first intermediate forging is held at 160°C for 19 hours, heated to 560°C at a rate of 40°C / h, held for 14 hours, then heated to 1020°C at a rate of 60°C / h, held for 35 hours, and air-cooled to 160°C to obtain the second intermediate forging.

[0074] A3. Third normalizing treatment: The second intermediate forging is held at 160°C for 19 hours, heated to 560°C at a rate of 40°C / h, held for 9 hours, then heated to 990°C at a rate of 60°C / h, held for 35 hours, and air-cooled to 160°C to obtain the third intermediate forging.

[0075] A4. First tempering treatment: The third intermediate forging is held at 160°C for 19 hours, heated to 630°C at a rate of 40°C / h, held for 44 hours, cooled to 200°C at a rate of 11°C / h, and air-cooled to room temperature to obtain the fourth intermediate forging.

[0076] A5. Quenching treatment: The fourth intermediate forging is heated to 1020℃ and held for 16 hours, then cooled to 160℃ by blowing air to obtain the fifth intermediate forging.

[0077] A6. Second tempering treatment: The fifth intermediate forging is heated to 580°C, held for 22 hours, and then air-cooled to 160°C to obtain the sixth intermediate forging.

[0078] A7. Third tempering treatment: The sixth intermediate forging is heated to 610°C and held for 28 hours. After cooling, a large rotary forging is obtained.

[0079] Comparative Example 1

[0080] B1. Annealing and isothermal treatment: The forging blank is held at 650℃ for 20h, heated to 1040℃ at a rate of 45℃ / h, held for 36h, furnace cooled to 560℃, held for 240h, furnace cooled to 200℃, and cooled to room temperature to obtain the first intermediate forging; wherein, the diameter of the forging blank is 4900mm and the height is 1120mm; the composition of the forging blank by weight percentage includes: C: 0.02%, Si: 0.3%, Mn: 0.70%, Cr: 12.5%, Mo: 0.60%, Ni: 5.0%, V: 0.03%, Cu: 0.20%, W: 0.05%, S: 0.004%, P: 0.010%, with the balance being Fe and unavoidable impurities.

[0081] B2. Quenching treatment: The first intermediate forging is heated to 1000℃ and held for 19 hours, and then cooled to 145℃ by blowing air to obtain the second intermediate forging.

[0082] B3. First tempering treatment: The second intermediate forging is heated to 580°C, held for 29 hours, and then air-cooled to 145°C to obtain the third intermediate forging.

[0083] B4. Secondary tempering treatment: The third intermediate forging is heated to 600°C and held for 36 hours. After cooling, a large rotary forging is obtained.

[0084] Comparative Example 2

[0085] B1. Annealing and Isothermal Treatment: The forging blank is held at 650℃ for 20 hours, then heated to 1040℃ at a rate of 45℃ / h, held for 36 hours, furnace cooled to 560℃, held for 240 hours, furnace cooled to 200℃, and cooled to room temperature to obtain the first intermediate forging; the first intermediate forging is heated to 650℃, held for 20 hours, then heated to 990℃ at a rate of 45℃ / h, held for 36 hours, furnace cooled to 560℃, held for 240 hours, furnace cooled to 200℃, and cooled to room temperature. A second intermediate forging is obtained; wherein the diameter of the forging blank is 4900 mm and the height is 1120 mm; the composition of the forging blank by weight percentage includes: C: 0.02%, Si: 0.3%, Mn: 0.70%, Cr: 12.5%, Mo: 0.60%, Ni: 5.0%, V: 0.03%, Cu: 0.20%, W: 0.05%, S: 0.004%, P: 0.010%, with the balance being Fe and unavoidable impurities.

[0086] B2. Quenching treatment: The second intermediate forging is heated to 1000℃ and held for 19 hours, and then cooled to 145℃ by blowing air to obtain the third intermediate forging.

[0087] B3. Tempering treatment: The third intermediate forging is heated to 580°C, held for 29 hours, and then air-cooled to 145°C to obtain the fourth intermediate forging.

[0088] B4. Secondary tempering treatment: The fourth intermediate forging is heated to 600°C and held for 36 hours. After cooling, a large rotary forging is obtained.

[0089] Example

[0090] The metallographic structure of the large turbine forgings obtained in Examples 1-3 and Comparative Examples 1-2 was characterized, and the results are shown in the figure. Figure 1-5 ,from Figure 1-5 It can be seen that the grain size grades of the large turbine forgings obtained in Examples 1-3 and Comparative Examples 1-2 are 2.8, 3.3, 4.3, 1.0, and 1.3, respectively. Furthermore, the large turbine forgings obtained in Comparative Examples 1-2 exhibit more severe mixed grains. Therefore, compared to Comparative Examples 1-2, the large turbine forgings obtained in Examples 1-3 have finer grain sizes. It should be noted that a higher grain size grade corresponds to finer grain size.

[0091] The mechanical properties and flaw detection limit sensitivity of the large wheel forgings prepared in Examples 1-3 and Comparative Examples 1-2 were characterized. The results are shown in Table 1. As can be seen from Table 1, compared with Comparative Examples 1-2, the large forgings in Examples 1-3 have higher yield strength, tensile strength, reduction of area and AKv, indicating that the large forgings in Examples 1-3 have higher strength and toughness. As can be seen from Table 1, compared with Comparative Examples 1-2, the large forgings in Examples 1-3 have higher flaw detection limit sensitivity.

[0092] Table 1

[0093]

[0094] It should be noted that in Table 1, radial and axial represent the radial and axial properties of the forging, respectively. Rp0.2 represents the yield strength, Rm represents the tensile strength, AKv is used to characterize the impact toughness, representing the energy absorbed by the material under impact load, A represents the elongation after fracture, and Z represents the reduction of area.

[0095] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A heat treatment method for a large 04Cr13Ni5Mo steel forging, characterized in that, The process includes sequentially performing post-forging heat treatment and quenching and tempering heat treatment on the forging blank; wherein, the post-forging heat treatment includes sequentially performing a first normalizing treatment, a second normalizing treatment, a third normalizing treatment, and a first tempering treatment; the quenching and tempering heat treatment includes sequentially performing a quenching treatment, a second tempering treatment, and a third tempering treatment; the normalizing temperature of the first normalizing treatment is 1030-1050℃, the normalizing temperature of the second normalizing treatment is 1010-1020℃, the normalizing temperature of the third normalizing treatment is 970-990℃, and the tempering temperature of the first tempering treatment is 610-630℃.

2. The heat treatment method for the 04Cr13Ni5Mo steel large turbine forging according to claim 1, characterized in that, The first normalizing treatment includes: The forging blank is held at 640-660℃ for 14-16 hours, then heated to 1030-1050℃ and held for 35-37 hours, and finally air-cooled to 130-160℃ to obtain the first intermediate forging.

3. The heat treatment method for the 04Cr13Ni5Mo steel large turbine forging according to claim 2, characterized in that, The second normalizing process includes: The first intermediate forging is held at 130-160℃ for 19-21 hours, then heated to 540-560℃ and held for 14-16 hours, then heated to 1010-1020℃ and held for 35-37 hours, and finally air-cooled to 130-160℃ to obtain the second intermediate forging.

4. The heat treatment method for the 04Cr13Ni5Mo steel large turbine forging according to claim 3, characterized in that, The third normalizing process includes: The second intermediate forging is held at 130-160℃ for 19-21 hours, then heated to 540-560℃ and held for 9-11 hours, then heated to 970-990℃ and held for 35-37 hours, and finally air-cooled to 130-160℃ to obtain the third intermediate forging.

5. The heat treatment method for the 04Cr13Ni5Mo steel large turbine forging according to claim 4, characterized in that, The first tempering process includes: The third intermediate forging is held at 130-160℃ for 19-21 hours, then heated to 610-630℃ and held for 44-46 hours. It is then cooled to 190-200℃ at a rate of 9-11℃ / h and air-cooled to room temperature to obtain the fourth intermediate forging.

6. The heat treatment method for the 04Cr13Ni5Mo steel large turbine forging according to claim 5, characterized in that, The quenching process includes: The fourth intermediate forging is heated to 980-1020℃ and held for 16-22 hours, then cooled to 130-160℃ by blowing air to obtain the fifth intermediate forging.

7. The heat treatment method for the 04Cr13Ni5Mo steel large turbine forging according to claim 6, characterized in that, The second tempering process includes: The fifth intermediate forging is heated to 560-600℃ and held for 22-36 hours, then air-cooled to 130-160℃ to obtain the sixth intermediate forging.

8. The heat treatment method for the 04Cr13Ni5Mo steel large turbine forging according to claim 7, characterized in that, The third tempering process includes: The sixth intermediate forging is heated to 580-610℃ and held for 28-44 hours. After cooling, a large rotary forging is obtained.

9. The heat treatment method for the 04Cr13Ni5Mo steel large turbine forging according to claim 1, characterized in that, The diameter of the forging blank is 4m or more.

10. The heat treatment method for the 04Cr13Ni5Mo steel large turbine forging according to claim 1, characterized in that, The forging blank comprises, by weight percentage: C: 0.01-0.04%, Si: 0-0.6%, Mn: 0.50-1.00%, Cr: 12.0-13.0%, Mo: 0.40-0.80%, Ni: 4.5-6.0%, V: 0-0.07%, Cu: 0-0.50%, W: 0-0.10%, S: 0-0.008%, P: 0-0.020%, with the balance being Fe and unavoidable impurities; wherein the sum of the mass fractions of V, Cu, and W is 0-0.50%.

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