Efficient heat treatment method for large-sized runner forging

Abstract

The application provides a high-efficiency heat treatment method for large-scale rotating wheel forgings, and relates to the technical field of steel heat treatment.The heat treatment method provided by the application firstly performs twice normalizing treatment on the forgings, controls the heating rate, normalizing temperature and holding time in the normalizing treatment process, so that the large-scale rotating wheel forgings have fine grain size, high strength and high toughness.The tempering temperature of the first tempering treatment is controlled to be 600-640 DEG C, the structure in the forgings is reversely transformed from austenite, the toughness of the forgings can be effectively improved, the hardness of the forgings is reduced, and rough machining in the later stage is facilitated.The heat treatment time of the heat treatment method for large-scale rotating wheel forgings is short, and the large-scale rotating wheel forgings obtained by using the method have fine grain size, high strength and high toughness.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for steel, and more specifically, to a high-efficiency heat treatment method for large rotary forgings. 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. Large impulse turbine runners have diameters exceeding 4 meters and thicknesses exceeding 1 meter, resulting in large cross-sectional dimensions for the 04Cr13Ni5Mo steel large runner forgings. During production, to ensure fine grain size and optimal mechanical properties, heat treatment is required after forging. Due to the large cross-sectional dimensions of the 04Cr13Ni5Mo steel large runner forgings, the heat treatment time is long and energy consumption is high, affecting production efficiency. Therefore, while ensuring the fine grain size and good mechanical properties of large 04Cr13Ni5Mo steel forgings, how to further shorten the heat treatment time of the forgings has become an urgent problem to be solved. Summary of the Invention

[0003] The problem solved by this invention is: how to further shorten the heat treatment time of large 04Cr13Ni5Mo steel forgings while ensuring finer grain size and better mechanical properties.

[0004] To address the above problems, this invention provides an efficient heat treatment method for large turbine forgings, comprising:

[0005] Step S1, First normalizing treatment: The forging blank of 04Cr13Ni5Mo steel is held at 150-200℃ for 10-20h, heated to 520-580℃ at a rate of 15-25℃ / h, then heated to 1020-1040℃ at a rate of 50-60℃ / h, held for 6-8h, furnace cooled to 940-960℃, held for 15-18h, and air cooled to 150-200℃ to obtain the first intermediate forging;

[0006] Step S2, Second normalizing treatment: The first intermediate forging is held at 150-200℃ for 10-20h, heated to 520-580℃ at a rate of 15-25℃ / h, then heated to 1020-1040℃ at a rate of 50-60℃ / h, held for 6-8h, furnace cooled to 940-960℃, held for 15-18h, and air cooled to 150-200℃ to obtain the second intermediate forging;

[0007] Step S3: Perform a first tempering treatment on the second intermediate forging to obtain a third intermediate forging; wherein the tempering temperature of the first tempering treatment is 600-640℃.

[0008] Step S4: Quench the third intermediate forging to obtain the fourth intermediate forging;

[0009] Step S5: Perform a second tempering treatment on the fourth intermediate forging to obtain a large wheel forging.

[0010] Optionally, in step S3, the first tempering process includes:

[0011] The second intermediate forging is held at 150-200℃ for 10-20 hours, heated to 600-630℃ at a first heating rate, held for 25-40 hours, cooled to 190-200℃ at a first cooling rate, and then removed from the furnace for cooling to obtain the third intermediate forging.

[0012] Optionally, in step S3, the first heating rate is 30-40℃ / h.

[0013] Optionally, in step S3, the first cooling rate is not higher than 10℃ / h.

[0014] Optionally, in step S4, the quenching process includes:

[0015] The third intermediate forging is heated to 200-250℃ and held for 10-15 hours. Then, it is heated to 520-600℃ at a rate of 15-25℃ / h, and then heated to 930-980℃ at a rate of 40-60℃ / h. After holding for 15-18 hours, it is air-cooled to 130-200℃ to obtain the fourth intermediate forging.

[0016] Optionally, in step S5, the second tempering process includes:

[0017] The fourth intermediate forging is held at 130-200℃ for 10-20 hours, heated to 580-610℃ at a second heating rate, held for 25-40 hours, and cooled to 190-200℃ at a second cooling rate. It is then removed from the furnace and cooled to obtain the large rotary forging.

[0018] Optionally, in step S5, the second heating rate is 30-40℃ / h.

[0019] Optionally, in step S5, the second cooling rate is 5-15℃ / h.

[0020] Optionally, in step S1, the diameter of the forging blank is 4m or more, and the thickness is 1m or more.

[0021] Optionally, in step S1, 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: 12.0-13.5%, 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%.

[0022] Compared with existing technologies, the heat treatment method provided in this invention first performs two normalizing treatments on the forging. During the normalizing process, the forging is first held at 150-200℃ for 10-20 hours to induce martensitic transformation. Then, the forging is heated to 1020-1040℃. During this heating process, before the forging temperature reaches 520-580℃, the heating rate is slow (15-25℃ / h), allowing the martensite to slowly recover, effectively reducing the thermal and structural stresses of the forging and improving the strength of the large turbine forging. When the forging temperature reaches 520-580℃, the heating rate is faster (50- A tempering temperature of 60℃ / h effectively increases the nucleation driving force of the material, promoting grain nucleation and thus refining the grains, which is beneficial for further improving the strength and toughness of large wheel forgings. After heating the forging to 1020-1040℃, holding it at this temperature for a short time (6-8h) avoids grain coarsening caused by prolonged holding at high temperatures and significantly reduces the normalizing time. Then, the forging is furnace cooled to 940-960℃ and held at this temperature for a relatively long time (15-18h) to ensure full austenitization of the microstructure, thereby further improving the strength and toughness of large wheel forgings. By controlling the tempering temperature of the first tempering treatment to 600-640℃, the microstructure of the forging undergoes a reverse austenitic 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 heat treatment method for large rotary forgings provided by this invention has a shorter heat treatment time, and the large rotary forgings obtained by this method have finer grain size, higher strength, and higher toughness. Attached Figure Description

[0023] Figure 1 Image showing the metallographic structure of the large wheel forging obtained in Example 1;

[0024] Figure 2 The image shows the metallographic structure of the large wheel forging obtained in Example 2;

[0025] Figure 3The image shows the metallographic structure of the large wheel forging obtained in Example 3;

[0026] Figure 4 The image shows the metallographic structure of the large wheel forgings prepared in the comparative example. 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, in this invention, large-scale turbine forgings refer to 04Cr13Ni5Mo steel turbine forgings with a diameter exceeding 4m and a thickness exceeding 1m.

[0031] This invention provides an efficient heat treatment method for large rotary forgings, comprising:

[0032] Step S1, First normalizing treatment: The forging blank of 04Cr13Ni5Mo steel is held at 150-200℃ for 10-20h, heated to 520-580℃ at a rate of 15-25℃ / h, then heated to 1020-1040℃ at a rate of 50-60℃ / h, held for 6-8h, furnace cooled to 940-960℃, held for 15-18h, and air cooled to 150-200℃ to obtain the first intermediate forging;

[0033] Step S2, Second normalizing treatment: The first intermediate forging is held at 150-200℃ for 10-20h, heated to 520-580℃ at a rate of 15-25℃ / h, then heated to 1020-1040℃ at a rate of 50-60℃ / h, held for 6-8h, furnace cooled to 940-960℃, held for 15-18h, and air cooled to 150-200℃ to obtain the second intermediate forging;

[0034] Step S3: Perform a first tempering treatment on the second intermediate forging to obtain a third intermediate forging; wherein the tempering temperature of the first tempering treatment is 600-640℃.

[0035] Step S4: Quench the third intermediate forging to obtain the fourth intermediate forging;

[0036] Step S5: Perform a second tempering treatment on the fourth intermediate forging to obtain a large wheel forging.

[0037] The heat treatment method provided in this embodiment of the invention first performs two normalizing treatments on the forging. During the normalizing process, the forging is first held at 150-200℃ for 10-20 hours to induce martensitic transformation. Then, the forging is heated to 1020-1040℃. During this heating process, before the forging temperature reaches 520-580℃, the heating rate is slow (15-25℃ / h), allowing the martensite to slowly recover, effectively reducing the thermal and structural stresses of the forging and improving the strength of the large turbine forging. When the forging temperature reaches 520-580℃, the heating rate is faster (50-60℃ / h). The process of heating the forging to 1020-1040℃ for a short time (6-8h) effectively increases the nucleation driving force, promoting grain nucleation and refining the grains, thus improving the strength and toughness of large wheel forgings. After heating the forging to 1020-1040℃, holding it at this temperature for a short time (6-8h) avoids grain coarsening caused by prolonged holding at high temperatures and significantly reduces the normalizing time. Then, the forging is furnace-cooled to 940-960℃ and held at this temperature for a relatively long time (15-18h) to ensure full austenitization of the microstructure, further improving the strength and toughness of the large wheel forgings. Controlling the tempering temperature of the first tempering treatment to 600-640℃ induces a reverse austenitic transformation in the microstructure of the forging, effectively improving its toughness and reducing its hardness, facilitating subsequent rough machining. In summary, the heat treatment method for large rotary forgings provided in this embodiment of the invention has a short heat treatment time, and the large rotary forgings obtained by this method have finer grain size, higher strength, and higher toughness.

[0038] 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℃.

[0039] In some embodiments of the present invention, step S3, the first tempering process includes:

[0040] The second intermediate forging is held at 150-200℃ for 10-20h, heated to 600-630℃ at a first heating rate, held for 25-40h, and cooled to 190-200℃ at a first cooling rate. It is then removed from the furnace and cooled to obtain the third intermediate forging. The first heating rate is 30-40℃ / h, and the first cooling rate is not higher than 10℃ / h.

[0041] In this embodiment, the second intermediate forging is held at 150-200℃ for 10-20h 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. Since the grain size of the forging is finer after the secondary normalizing treatment, heating to 600-630℃ at a relatively fast rate (30-40℃ / h) will not bring the risk of cracking. Finally, the forging is cooled slowly to reduce the internal stress of the forging.

[0042] In some embodiments of the present invention, step S4, the quenching process includes:

[0043] The third intermediate forging is heated to 200-250℃ and held for 10-15 hours. Then, it is heated to 520-600℃ at a rate of 15-25℃ / h, and then heated to 930-980℃ at a rate of 40-60℃ / h. After holding for 15-18 hours, it is air-cooled to 130-200℃ to obtain the fourth intermediate forging.

[0044] In this embodiment, the forging is held at 200-250℃ for 10-20 hours to ensure uniform temperature inside and outside the forging. Then, the forging is heated to 930-980℃. During this heating process, when the temperature of the forging has not reached 520-600℃, the heating rate is slow (15-25℃ / h), allowing martensite to recover slowly, which can effectively reduce the thermal stress and structural stress of the forging and is beneficial to further improve the strength of the large wheel forging. When the temperature of the forging reaches 520-600℃, the heating rate is faster (40-60℃ / h), which can effectively increase the material nucleation driving force, promote grain nucleation, and thus effectively refine the grains, which is beneficial to further improve the strength and toughness of the large wheel forging. At 930-980℃, it is held for 15-18 hours to heat the core of the forging to above 900℃, ensuring full austenitization.

[0045] In some embodiments of the present invention, step S5, the second tempering process includes:

[0046] The fourth intermediate forging is held at 130-200℃ for 10-20h, heated to 580-610℃ at a second heating rate, held for 25-40h, and cooled to 190-200℃ at a second cooling rate. It is then removed from the furnace and cooled to obtain the large rotary forging. The second heating rate is 30-40℃ / h, and the second cooling rate is 5-15℃ / h.

[0047] In this embodiment, the fourth intermediate forging is held at 130-200℃ for 10-20 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; holding at 580-610℃ (slightly higher than the Ac1 temperature of the forging) causes a small amount of reverse austenite transformation in the forging, which is beneficial to further improve the toughness of the forging.

[0048] In some embodiments of the present invention, in step S1, the diameter of the forging blank is 4m or more and the thickness is 1m or more.

[0049] In some embodiments of the present invention, in step S1, 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: 12.0-13.5%, 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%.

[0050] The present invention will be further described below with reference to specific embodiments.

[0051] Example 1

[0052] A1. First normalizing treatment: The forging blank made of 04Cr13Ni5Mo steel is held at 175℃ for 15 hours, heated to 550℃ at a rate of 20℃ / h, then heated to 1030℃ at a rate of 55℃ / h, held for 7 hours, furnace cooled to 950℃, held for 16.5 hours, and air cooled to 175℃ to obtain the first intermediate forging; the diameter of the forging blank is 4800mm and the height is 1000mm; by weight percentage, the composition of the forging blank 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.

[0053] A2. Second normalizing treatment: The first intermediate forging is held at 175°C for 15 hours, heated to 550°C at a rate of 20°C / hour, then heated to 1030°C at a rate of 55°C / hour, held for 7 hours, furnace cooled to 950°C, held for 16.5 hours, and air cooled to 175°C to obtain the second intermediate forging.

[0054] A3. First tempering treatment: The second intermediate forging is held at 175°C for 15 hours, heated to 615°C at a first heating rate, held for 32 hours, and cooled to 195°C at a first cooling rate. The third intermediate forging is then obtained by cooling. The first heating rate is 35°C / h, and the first cooling rate is 8°C / h.

[0055] A4. Quenching treatment: The third intermediate forging is heated to 225°C and held for 12.5 hours. Then, it is heated to 560°C at a rate of 20°C / hour, and then heated to 955°C at a rate of 50°C / hour. It is held for 16.5 hours and then air-cooled to 165°C to obtain the fourth intermediate forging.

[0056] A5. Second tempering treatment: The fourth intermediate forging is held at 165°C for 15 hours, heated to 595°C at a second heating rate, held for 32 hours, and cooled to 195°C at a second cooling rate to obtain the large rotary forging; wherein, the second heating rate is 35°C / h and the second cooling rate is 10°C / h.

[0057] Example 2

[0058] A1. First normalizing treatment: The forging blank made of 04Cr13Ni5Mo steel is held at 150℃ for 20h, heated to 520℃ at a rate of 15℃ / h, then heated to 1020℃ at a rate of 50℃ / h, held for 8h, furnace cooled to 940℃, held for 18h, and air cooled to 150℃ to obtain the first intermediate forging; the diameter of the forging blank is 4900mm and the height is 1120mm; by weight percentage, the composition of the forging blank 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.

[0059] A2. Second normalizing treatment: The first intermediate forging is held at 150°C for 20 hours, heated to 520°C at a rate of 15°C / h, then heated to 1020°C at a rate of 50°C / h, held for 8 hours, furnace cooled to 940°C, held for 18 hours, and air cooled to 150°C to obtain the second intermediate forging.

[0060] A3. First tempering treatment: The second intermediate forging is held at 150°C for 20 hours, heated to 600°C at a first heating rate, held for 40 hours, cooled to 190°C at a first cooling rate, and then removed from the furnace for cooling to obtain the third intermediate forging; wherein, the first heating rate is 30°C / h, and the first cooling rate is 8°C / h.

[0061] A4. Quenching treatment: The third intermediate forging is heated to 200°C and held for 15 hours. Then, the temperature is increased to 520°C at a rate of 15°C / hour, and then increased to 930°C at a rate of 40°C / hour. The temperature is held for 18 hours and then air-cooled to 130°C to obtain the fourth intermediate forging.

[0062] A5. Second tempering treatment: The fourth intermediate forging is held at 130°C for 20 hours, heated to 580°C at a second heating rate, held for 40 hours, and cooled to 190°C at a second cooling rate to obtain the large rotary forging; wherein, the second heating rate is 30°C / h and the second cooling rate is 5°C / h.

[0063] Example 3

[0064] A1. First normalizing treatment: The forging blank made of 04Cr13Ni5Mo steel is held at 200℃ for 10h, heated to 580℃ at a rate of 25℃ / h, then heated to 1040℃ at a rate of 60℃ / h, held for 6h, furnace cooled to 960℃, held for 15h, and air cooled to 200℃ to obtain the first intermediate forging; the diameter of the forging blank is 4000mm and the height is 1000mm; by weight percentage, the composition of the forging blank 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 200°C for 10 hours, heated to 580°C at a rate of 25°C / h, then heated to 1040°C at a rate of 60°C / h, held for 6 hours, furnace cooled to 960°C, held for 15 hours, and air cooled to 200°C to obtain the second intermediate forging.

[0066] A3. First tempering treatment: The second intermediate forging is held at 200°C for 10-20 hours, heated to 630°C at a first heating rate, held for 25 hours, cooled to 200°C at a first cooling rate, and then removed from the furnace for cooling to obtain the third intermediate forging; wherein, the first heating rate is 40°C / h, and the first cooling rate is 8°C / h.

[0067] A4. Quenching treatment: The third intermediate forging is heated to 250°C and held for 10 hours. Then, the temperature is increased to 600°C at a rate of 25°C / hour, and then increased to 980°C at a rate of 60°C / hour. The temperature is held for 15 hours and then air-cooled to 200°C to obtain the fourth intermediate forging.

[0068] A5. Second tempering treatment: The fourth intermediate forging is held at 200°C for 10 hours, heated to 610°C at a second heating rate, held for 25 hours, and cooled to 200°C at a second cooling rate. The large rotary forging is then obtained. The second heating rate is 40°C / h, and the second cooling rate is 15°C / h.

[0069] Comparative Example

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] Compared with Examples 1-3, the comparative example involves more heat treatment processes and takes longer for the forgings.

[0078] Experimental Example

[0079] The metallographic structure of the large turbine forgings obtained in Examples 1-3 and the comparative examples was characterized, and the results are shown in the figure. Figure 1-4 ,from Figure 1-4 It can be seen that the grain size grades of the large turbine forgings obtained in Examples 1-3 and the comparative example are 3.5, 3.8, 4.5, and 2.8, respectively. This indicates that the large turbine forgings obtained in Examples 1-3 have finer grain size compared to the comparative example. It should be noted that a higher grain size grade corresponds to finer grain size. Figure 1-4 The length represented by the scale is 100μm.

[0080] The mechanical properties and flaw detection limit sensitivity of the large forgings obtained in Examples 1-3 and the comparative examples were characterized. The results are shown in Table 1. As can be seen from Table 1, compared with the comparative examples, the large forgings in Examples 1-3 have higher yield strength, tensile strength, elongation after fracture, 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 the comparative examples, the large forgings in Examples 1-3 have higher flaw detection limit sensitivity.

[0081] Table 1

[0082]

[0083]

[0084] 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.

[0085] 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 highly efficient heat treatment method for large rotary forgings, characterized in that, include: Step S1, First normalizing treatment: The forging blank of 04Cr13Ni5Mo steel is held at 150-200℃ for 10-20h, heated to 520-580℃ at a rate of 15-25℃ / h, then heated to 1020-1040℃ at a rate of 50-60℃ / h, held for 6-8h, furnace cooled to 940-960℃, held for 15-18h, and air cooled to 150-200℃ to obtain the first intermediate forging; Step S2, Second normalizing treatment: The first intermediate forging is held at 150-200℃ for 10-20h, heated to 520-580℃ at a rate of 15-25℃ / h, then heated to 1020-1040℃ at a rate of 50-60℃ / h, held for 6-8h, furnace cooled to 940-960℃, held for 15-18h, and air cooled to 150-200℃ to obtain the second intermediate forging; Step S3: Perform a first tempering treatment on the second intermediate forging to obtain a third intermediate forging; wherein, the tempering temperature of the first tempering treatment is 600-640℃; Step S4: Quench the third intermediate forging to obtain the fourth intermediate forging; Step S5: Perform a second tempering treatment on the fourth intermediate forging to obtain a large wheel forging.

2. The efficient heat treatment method for large turbine forgings according to claim 1, characterized in that, In step S3, the first tempering process includes: The second intermediate forging is held at 150-200℃ for 10-20 hours, heated to 600-630℃ at a first heating rate, held for 25-40 hours, cooled to 190-200℃ at a first cooling rate, and then removed from the furnace for cooling to obtain the third intermediate forging.

3. The efficient heat treatment method for large turbine forgings according to claim 2, characterized in that, In step S3, the first heating rate is 30-40℃ / h.

4. The efficient heat treatment method for large turbine forgings according to claim 2, characterized in that, In step S3, the first cooling rate is no higher than 10℃ / h.

5. The efficient heat treatment method for large rotary forgings according to claim 1, characterized in that, In step S4, the quenching process includes: The third intermediate forging is heated to 200-250℃ and held for 10-15 hours. Then, it is heated to 520-600℃ at a rate of 15-25℃ / h, and then heated to 930-980℃ at a rate of 40-60℃ / h. After holding for 15-18 hours, it is air-cooled to 130-200℃ to obtain the fourth intermediate forging.

6. The efficient heat treatment method for large turbine forgings according to claim 1, characterized in that, In step S5, the second tempering process includes: The fourth intermediate forging is held at 130-200℃ for 10-20 hours, heated to 580-610℃ at a second heating rate, held for 25-40 hours, and cooled to 190-200℃ at a second cooling rate. It is then removed from the furnace and cooled to obtain the large rotary forging.

7. The efficient heat treatment method for large turbine forgings according to claim 6, characterized in that, In step S5, the second heating rate is 30-40℃ / h.

8. The efficient heat treatment method for large turbine forgings according to claim 6, characterized in that, In step S5, the second cooling rate is 5-15℃ / h.

9. The efficient heat treatment method for large turbine forgings according to claim 1, characterized in that, In step S1, the diameter of the forging blank is 4m or more, and the thickness is 1m or more.

10. The efficient heat treatment method for large turbine forgings according to claim 1, characterized in that, In step S1, 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: 12.0-13.5%, 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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