High-alloy martensitic heat-resistant steel rotor after-forging annealing method and formulating method thereof

Abstract

The invention provides a high-alloy martensitic heat-resistant steel rotor post-forging annealing method and a formulating method thereof, and relates to the technical field of heat treatment.The formulating method of the high-alloy martensitic heat-resistant steel rotor post-forging annealing method comprises the steps that JMatPro software is used for simulation calculation, the austenitizing temperature range and the isothermal transformation temperature range are determined within one hour, and the temperature range of the austenitizing temperature and the isothermal transformation temperature range are determined within one hour; groping through a large number of physical experiments is avoided, and the test time is greatly shortened; through a physical experiment, an experiment scheme of the influence of the austenitizing temperature and the isothermal transformation temperature on the pearlite and ferrite transformation amount is formulated in a temperature range determined by JMatPro software, the optimal austenitizing temperature, the optimal isothermal transformation temperature and the optimal time parameter of a post-forging annealing process are obtained, and the optimal austenitizing temperature and the optimal isothermal transformation temperature are obtained by utilizing a mode of combining JMatPro and abaqus software simulation with the physical experiment. Temperature parameters and time parameters of the post-forging annealing process are rapidly and efficiently determined, the making process period is short, and the rotor manufacturing period is effectively shortened.

Description

Technical Field

[0001] The present invention relates to the field of heat treatment technology, and in particular to a post-forging annealing method for a high-alloy martensitic heat-resistant steel rotor and a formulation method thereof. Background Art

[0002] At present, the technical indicators of high-alloy martensitic heat-resistant steel rotor products require that the flaw detection sensitivity should be less than This puts forward requirements for the rotor grain size and uniformity. Too coarse grains and poor uniformity will affect the sensitivity of flaw detection. The steel used for ultra-supercritical rotors is mostly 9-12Cr high-alloy martensitic heat-resistant steel, which has a great tendency of tissue inheritance. After the rotor is forged, it is inevitable that there will be uneven grains from the surface to the core. Conventional post-forging annealing processes to eliminate organizational inheritance often use small sample heat treatment physical experimental methods. After austenitizing, they are slowly cooled to the ferrite + pearlite transformation temperature range, and the purpose of isothermal phase transformation is achieved through long-term isothermal treatment. The key heat treatment parameters include the austenitizing temperature range, the isothermal transformation temperature range and the isothermal transformation holding time. The optimal austenitizing temperature and isothermal transformation temperature range can be explored through a large number of physical experiments. However, due to the strong austenite stability of high-alloy martensitic heat-resistant steel, the isothermal time is usually more than one hundred hours, resulting in a long physical experiment cycle and high energy consumption. In addition, due to the size effect of large forgings, the temperature field at different positions of large-section rotor forgings during heat treatment needs to be cast into solid pieces, and the temperature of the core of the test piece is measured by embedding a coupler to obtain the average temperature data. The test piece is scrapped, and rotor forgings with changed sizes and cross-sections need to be specially cast into test pieces, which has high material costs and long experimental cycles. Summary of the invention

[0003] The problem solved by the present invention is how to solve the problem of long cycle and high material cost in formulating the annealing parameters of a high alloy martensitic heat-resistant steel rotor after forging.

[0004] In order to solve the above problems, the present invention provides a post-forging annealing method for a high-alloy martensitic heat-resistant steel rotor and a formulation method thereof.

[0005] In a first aspect, the present invention provides a method for formulating a post-forging annealing method for a high-alloy martensitic heat-resistant steel rotor, comprising the following steps:

[0006] S1: Call the JMatPro Fe-General Steel general steel module and its database, input the composition of high-alloy martensitic heat-resistant steel, calculate the austenite phase transformation temperature parameter Ac3, set the grain size level according to the forging completed grain size, set the maximum range of austenitization temperature, and simulate and calculate to obtain the isothermal transformation curve;

[0007] S2. Compare the effects of different austenitizing temperatures on the isothermal transformation of pearlite, select one or more groups of temperatures corresponding to the shortest pearlite incubation period as the optimal austenitizing temperature range, and select the isothermal transformation temperature range according to the transformation temperature of pearlite;

[0008] S3. Conduct physical experiments to verify and formulate an experimental plan for the effects of austenitizing temperature and isothermal transformation temperature on the transformation amount of pearlite and ferrite. Compare the time required for the transformation amount of pearlite and ferrite to reach ≥ 90% at different austenitizing temperature and isothermal transformation temperature, and obtain the optimal isothermal transformation temperature with the shortest isothermal transformation time.

[0009] S4. Use abaqus software to The above large-section rotor forgings simulate the isothermal process of austenitizing furnace cooling to the isothermal transformation temperature, and obtain the heat treatment temperature curve of the surface and core of the large-section rotor forgings, obtain the time required for the surface and core of the rotor forgings to reach the uniform temperature, and select the optimal time parameters for the post-forging annealing process;

[0010] S5. Develop a post-forging annealing method for high-alloy martensitic heat-resistant steel rotors. After forging, the temperature is raised to homogenize the grain size, then the temperature is lowered to complete the martensitic transformation, and then the temperature is raised to the optimal isothermal transformation temperature and kept warm for pre-tempering to precipitate carbides. Then the temperature is heated to the optimal austenitizing temperature and kept warm for austenitization, and then the temperature is lowered to the optimal isothermal transformation temperature and kept warm for isothermal transformation. After completion, the temperature is lowered to room temperature.

[0011] Optionally, the composition of the high alloy martensitic heat-resistant steel rotor includes C: 0.01%-0.14%, Si: 0.05%-0.50%, Mn: 0.05%-0.70%, Cr: 8.5%-13%, W: 2.0%-3.5%, Mo: 0.1%-0.7%, Nb: 0.03%-0.07%, V: 0.1%-0.3%, Co: 2.8%-5%, Cu: 0.5%-1.5%, Ni: 0.1%-0.5%, B: 0.01%-0.015%, N: 0.01%-0.08%, Ta: 0.2%-0.5%, Zr: 0.1%-0.5% and Ce+Y: 0.01%-0.3%.

[0012] Optionally, in step S1, the maximum range of austenitizing temperature is set to Ac3+(10-350)°C.

[0013] Optionally, in step S2, the temperatures corresponding to the Ac3+10°C group to the Ac3+50°C group with the shortest pearlite incubation period are selected as the range of optimal austenitizing temperatures, and the range of optimal austenitizing temperatures is Ac3+(10-50)°C.

[0014] Optionally, in step S2, the transformation temperature of pearlite is 677-686°C, and the isothermal transformation temperature range is selected to be 680±30°C.

[0015] Optionally, in step S3, the optimal austenitizing temperature with the shortest isothermal transformation time is Ac3+10°C, and the shortest isothermal transformation time is 50h.

[0016] Optionally, in step S4, the optimal time parameters of the post-forging annealing process include pre-tempering time and annealing time, and the equalization time of the forging surface and core is set as the pre-tempering time, and the pre-tempering time is 20-25h; the time required for isothermal transformation and the value of the pre-tempering time are set as the annealing time, and the annealing time is 70-75h.

[0017] Optionally, step S5 specifically includes: formulating a post-forging annealing method for a high-alloy martensitic heat-resistant steel rotor, heating the temperature to 1050-1100°C after forging and keeping it for more than 10 hours to homogenize the grain size, then cooling the temperature to 150-250°C and keeping it for more than 10 hours to complete the martensitic transformation, then heating the temperature to 680±30°C and keeping it for 20-25 hours for pre-tempering to precipitate carbides, then heating to Ac3+(10-50)°C and keeping it for 10-15 hours for austenitization, then cooling the temperature to 680±30°C and keeping it for 70-75 hours for isothermal transformation, and then cooling to room temperature after completion.

[0018] In a second aspect, the present invention provides a method for annealing a high-alloy martensitic heat-resistant steel rotor after forging, which is formulated using the method for formulating the method for annealing a high-alloy martensitic heat-resistant steel rotor after forging as described in any of the above items.

[0019] Optionally, the following steps are included:

[0020] Take the forged high alloy martensitic heat-resistant steel rotor, heat it to 1050-1150℃ and keep it for more than 10h to homogenize the grain size, then cool it to 150-250℃ and keep it for more than 10h to complete the martensitic transformation, then heat it to 680±30℃ and keep it for 20-25h for pre-tempering to precipitate carbides, then heat it to Ac3+(10-50)℃ and keep it for 10-15h for austenitization, then cool it to 680±30℃ and keep it for 70-75h for isothermal transformation, and then cool it to room temperature after completion;

[0021] Among them, the composition of the high alloy martensitic heat-resistant steel rotor includes C: 0.01%-0.14%, Si: 0.05%-0.50%, Mn: 0.05%-0.70%, Cr: 8.5%-13%, W: 2.0%-3.5%, Mo: 0.1%-0.7%, Nb: 0.03%-0.07%, V: 0.1%-0.3%, Co: 2.8%-5%, Cu: 0.5%-1.5%, Ni: 0.1%-0.5%, B: 0.01%-0.015%, N: 0.01%-0.08%, Ta: 0.2%-0.5%, Zr: 0.1%-0.5% and Ce+Y: 0.01%-0.3%.

[0022] The beneficial effects of the post-forging annealing method of a high-alloy martensitic heat-resistant steel rotor of the present invention and the formulation method thereof are as follows: using JMatPro software to simulate and calculate, the range of austenitizing temperature and the range of isothermal transformation temperature are determined, avoiding groping through a large number of physical experiments, and the time for selecting the isothermal transformation temperature range can be completed within 1 hour, which greatly shortens the test time; through physical experiments, an experimental scheme for the influence of austenitizing temperature and isothermal transformation temperature on the transformation amount of pearlite and ferrite is formulated within the temperature range determined by JMatPro software, and the optimal austenitizing temperature, the optimal isothermal transformation temperature and the optimal time parameters of the post-forging annealing process are obtained, and the JMatPro software simulation and physical experiments are used to simulate the austenitizing temperature and the isothermal transformation temperature. The combined approach can quickly and efficiently determine the temperature and time parameters of the post-forging annealing process, shorten the process cycle, effectively shorten the rotor manufacturing cycle, and do not require the test pieces of each size to be scrapped by embedding a coupler in the core of the test piece for temperature measurement, thereby reducing material costs. The temperature and time parameters of the post-forging annealing process are determined by combining JMatPro and abaqus software simulation with physical experiments, which can effectively eliminate the inheritance of high-alloy martensitic heat-resistant steel structure. After annealing, the rotor structure is ferrite + pearlite without martensite, achieving the effect of isothermal structure transformation. After normalizing, the grain (size) is refined to 50μm, breaking the inheritance of martensitic structure, and the sensitivity of the flaw detection is <φ1.6. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flow chart of a method for formulating a method for annealing a high alloy martensitic heat-resistant steel rotor after forging according to an embodiment of the present invention;

[0024] Figure 2 The isothermal transformation curve diagram calculated by Jmatpro software simulation in the embodiment of the present invention;

[0025] Figure 3 The isothermal transformation curve diagram of the embodiment of the present invention is simulated and calculated by Jmatpro software in the austenitizing temperature range of Ac3+(10-350)°C;

[0026] Figure 4 A schematic diagram of a physical experiment scheme for determining the effect of austenitizing temperature on the transformation amount of pearlite and ferrite according to an embodiment of the present invention;

[0027] Figure 5 The embodiment of the present invention is a line graph of the transformation amount of pearlite and ferrite after isothermal treatment for 50 and 100 hours at different austenitizing temperatures;

[0028] Figure 6 This is an optical microscope image of an embodiment of the present invention when the transformation amount of pearlite and ferrite reaches 100%;

[0029] Figure 7 The heat treatment temperature curve of the simulated large-section rotor forging according to the embodiment of the present invention;

[0030] Figure 8 Schematic diagram of a post-forging annealing method for a high-alloy martensitic heat-resistant steel rotor according to an embodiment of the present invention;

[0031] Fig. 9 This is an optical microscope image of a φ900mm 16-ton trial product after annealing according to an embodiment of the present invention;

[0032] Fig.10 This is an optical microscope image of a φ900mm 16-ton trial product of an embodiment of the present invention after annealing and normalizing;

[0033] Fig.11 This is an optical microscope image of a φ900mm 16-ton trial product of an embodiment of the present invention before the post-forging annealing process is performed. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be interpreted as being limited to the embodiments described herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0035] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention;

[0036] The term "including" and its variations used herein are open inclusions, i.e., "including but not limited to"; the term "based on" means "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description.

[0037] In view of the problems existing in the above-mentioned related technologies, this embodiment provides a method for annealing a high-alloy martensitic heat-resistant steel rotor after forging and a formulation method thereof.

[0038] like Figure 1 As shown, a method for formulating a method for annealing a high alloy martensitic heat-resistant steel rotor after forging provided by an embodiment of the present invention comprises the following steps:

[0039] S1: Call the JMatPro Fe-General Steel general steel module and its database, input the composition of high-alloy martensitic heat-resistant steel, calculate the austenite phase transformation temperature parameter Ac3, set the grain size level according to the forging completed grain size, set the maximum range of austenitization temperature, and simulate and calculate to obtain the isothermal transformation curve;

[0040] S2. Compare the effects of different austenitizing temperatures on the isothermal transformation of pearlite, select one or more groups of temperatures corresponding to the shortest pearlite incubation period as the optimal austenitizing temperature range, and select the isothermal transformation temperature range according to the transformation temperature of pearlite;

[0041] S3. Conduct physical experiments to verify and develop an experimental plan for the effects of austenitizing temperature and isothermal transformation temperature on the transformation amount of pearlite and ferrite. Compare the time required for the transformation amount of pearlite and ferrite to reach ≥ 90% at different austenitizing temperatures and isothermal transformation temperatures, and obtain the optimal austenitizing temperature with the shortest isothermal transformation time.

[0042] S4. Use abaqus software to The above large-section rotor forgings simulate the isothermal process of austenitizing furnace cooling to the isothermal transformation temperature, and obtain the heat treatment temperature curve of the surface and core of the large-section rotor forgings, obtain the time required for the surface and core of the rotor forgings to reach the uniform temperature, and select the optimal time parameters for the post-forging annealing process;

[0043] S5. Develop a post-forging annealing method for high-alloy martensitic heat-resistant steel rotors. After forging, the temperature is raised to homogenize the grain size, then the temperature is lowered to complete the martensitic transformation, and then the temperature is raised to the optimal isothermal transformation temperature and kept warm for pre-tempering to precipitate carbides. Then the temperature is heated to the optimal austenitizing temperature and kept warm for austenitization, and then the temperature is lowered to the optimal isothermal transformation temperature and kept warm for isothermal transformation. After completion, the temperature is lowered to room temperature.

[0044] In this embodiment, JMatPro software is used for simulation and calculation to determine the range of austenitizing temperature and the range of isothermal transformation temperature, so as to avoid groping through a large number of physical experiments. The time for selecting the isothermal transformation temperature range can be completed within 1 hour, which greatly shortens the test time. Through physical experiments, an experimental plan for the influence of austenitizing temperature and isothermal transformation temperature on the transformation amount of pearlite and ferrite is formulated within the temperature range determined by JMatPro software, and the optimal austenitizing temperature, the optimal isothermal transformation temperature and the optimal time parameters of the annealing process after forging are obtained. The combination of JMatPro software simulation and physical experiments is used to quickly and efficiently obtain the optimal austenitizing temperature, the optimal isothermal transformation temperature and the optimal time parameters of the annealing process after forging. The temperature and time parameters of the post-forging annealing process are clarified, and the process cycle is short, which effectively shortens the rotor manufacturing cycle. There is no need to bury a coupler in the core of each size of the test piece to measure the temperature, which causes the test piece to be scrapped, thereby reducing material costs. The temperature and time parameters of the post-forging annealing process are clarified by combining JMatPro software simulation with physical experiments, which can effectively eliminate the inheritance of high-alloy martensitic heat-resistant steel structure. After annealing, the rotor structure is ferrite + pearlite, without martensite, achieving the effect of isothermal structure transformation. After normalizing, the grain (size) is refined to 50μm, breaking the inheritance of martensitic structure, and the sensitivity of the flaw detection is <φ1.6.

[0045] Specifically, Ac3 refers to the final temperature at which all proeutectoid ferrite is transformed into austenite during the heating process of steel. Specifically, Ac3 is the final temperature at which all proeutectoid ferrite is transformed into austenite during the heating process of steel, indicating that the ferrite component in the iron-carbon alloy has been completely transformed into austenite.

[0046] The isothermal transformation curve, namely the TTT curve (T-time, T-temperature, T-transformation), can comprehensively reflect the relationship between the isothermal temperature, holding time and the percentage of transformation products (transformation start and transformation end) of supercooled austenite at different supercooling degrees, and is also called the "C curve".

[0047] Optionally, the composition of the high alloy martensitic heat-resistant steel rotor includes C: 0.01%-0.14%, Si: 0.05%-0.50%, Mn: 0.05%-0.70%, Cr: 8.5%-13%, W: 2.0%-3.5%, Mo: 0.1%-0.7%, Nb: 0.03%-0.07%, V: 0.1%-0.3%, Co: 2.8%-5%, Cu: 0.5%-1.5%, Ni: 0.1%-0.5%, B: 0.01%-0.015%, N: 0.01%-0.08%, Ta: 0.2%-0.5%, Zr: 0.1%-0.5% and Ce+Y: 0.01%-0.3%.

[0048] Optionally, in step S1, the maximum range of austenitizing temperature is set to Ac3+(10-350)°C.

[0049] In this optional embodiment, the Jmatpro software calculates the Ac3 temperature point and sets the maximum austenitizing temperature range to Ac3+(10-350)°C. Impurities will appear when the temperature exceeds Ac3+350°C.

[0050] Optionally, in step S2, the temperatures corresponding to the Ac3+10°C group to the Ac3+50°C group with the shortest pearlite incubation period are selected as the range of optimal austenitizing temperatures, and the range of optimal austenitizing temperatures is Ac3+(10-50)°C.

[0051] In this optional embodiment, if Figure 2 As shown, the green curve is the pearlite inoculation curve, the blue curve is the bainite inoculation curve, and the two black straight lines at the bottom are the martensite inoculation lines. The transformation temperature of pearlite is 677-686℃. In the austenitizing temperature range of Ac3+(10-350)℃, multiple temperatures of Ac3+10℃, Ac3+50℃, Ac3+100℃, Ac3+200℃ and Ac3+350℃ are selected for simulation, and the transformation time of pearlite is measured respectively, as shown in FIG. Figure 3 As shown, the pearlite incubation curve is above 500℃, and the bainite incubation curve is below 500℃. The shortest pearlite incubation period is in the Ac3+10℃ group, and the incubation period of the nose tip of the pearlite transformation C curve (i.e. the shortest time) is less than 10 hours. With the increase of austenitizing temperature, the incubation period of the nose tip of the pearlite transformation C curve is prolonged. The incubation period of the nose tip of the pearlite transformation C curve in the Ac3+50℃ group is 10-15 hours, among which the Ac3+350℃ group requires the longest time. There is little difference between the Ac3+100℃ group and the Ac3+350℃ group, all of which require more than 20 hours. The simulation results of Jmatpro software narrow the austenitizing temperature range to Ac3+(10-50)℃.

[0052] Optionally, in step S2, the transformation temperature of pearlite is 677-686°C, and the isothermal transformation temperature range is selected to be 680±30°C.

[0053] In this optional embodiment, if Figure 2 As shown, the transformation temperature of pearlite is 677-686°C, and the transformation temperature of bainite is between 350-500°C. The isothermal transformation temperature range is selected based on the premise of pearlite transformation and avoiding bainite transformation. The isothermal transformation temperature range is artificially selected to be 680±30°C.

[0054] Optionally, in step S3, the optimal austenitizing temperature with the shortest isothermal transformation time is Ac3+10°C, and the shortest isothermal transformation time is 50h.

[0055] In this optional embodiment, if Figure 3 As shown in the figure, the shortest pearlite incubation period is in the Ac3+10 group, and the incubation period (i.e. the shortest time) of the nose of the pearlite transformation C curve is less than 10 hours, so the optimal austenitizing temperature is selected as Ac3+10℃. Figure 4 As shown in the figure, combined with the jmatpro simulation results, a physical experiment plan was developed to study the effect of austenitizing temperature on the transformation of pearlite and ferrite. Samples with the same initial organization and grain size (size greater than 20*20*20mm) were heated to Ac3+10℃, Ac3+50℃, Ac3+100℃ and Ac3+150℃ for 5-10h in the furnace, respectively, and kept warm for 5-15h. They were then cooled to 700℃ in the furnace and kept warm for 50 or 100h and then air-cooled. To eliminate the influence of the surface decarburization layer, the sample was cut in the middle, and the organization of the middle surface was observed to obtain the transformation of pearlite and ferrite under different processes. The results are summarized and analyzed, as shown in the figure. Figure 5 As shown, when heated to Ac3+10℃, the transformation amount of pearlite and ferrite reaches 100% in 50 hours; when heated to Ac3+50℃, the transformation amount of pearlite and ferrite reaches 95% in 50 hours, and the transformation amount of pearlite and ferrite reaches 100% in 100 hours. It can be seen that when the austenitizing temperature is Ac3+10℃, the shortest time required for isothermal transformation is 50h. Figure 6 As shown, the microstructure when the transformation amount of pearlite and ferrite reaches 100%.

[0056] Optionally, in step S4, the optimal time parameters of the post-forging annealing process include pre-tempering time and annealing time, and the equalization time of the forging surface and core is set as the pre-tempering time, and the pre-tempering time is 20-25h; the time required for isothermal transformation and the value of the pre-tempering time are set as the annealing time, and the annealing time is 70-75h.

[0057] In this optional embodiment, for a φ900mm large-section rotor forging, the isothermal process of austenitizing furnace cooling to 700°C is simulated, and the simulation software is abaqus, and the temperature curves of the surface and core of the φ900mm large-section rotor forging are obtained, as shown in Table 1 and Figure 7 As shown, Figure 7 The "lower couple" in the middle is the surface temperature obtained by the physical experiment of the actual sample, and the surface and core are software simulation curves. It can be seen that the curves obtained by software simulation and physical experiment are not much different, and the error of software simulation is small. It can be seen that the time required for the surface and core to be evenly heated is 20h, so the annealing and holding time for isothermal transformation of large forgings is at least 70h (50h+20h).

[0058] The simulation method is used to predict the temperature equalization time of the surface and core of large-section forgings, thus avoiding the damage to the product caused by core drilling. While saving cost and time, a reasonable and effective process is formulated.

[0059] Table 1 Average temperature of large-section rotor forgings at 700°C.

[0060] 700℃ holding time / h Surface temperature / ℃ Core temperature / ℃ Temperature difference between surface and core / ℃ 0 766 850 84 8.7 710 728 18 14 706 711 5 20 705 706 1

[0061] Alternatively, if Figure 8 As shown, step S5 specifically includes: formulating a post-forging annealing method for a high-alloy martensitic heat-resistant steel rotor, heating the temperature to 1050-1150°C after forging and keeping it for more than 10 hours to homogenize the grain size, then cooling it to 150-250°C and keeping it for more than 10 hours to complete the martensitic transformation, then heating it to 680±30°C and keeping it for 20-25 hours for pre-tempering to precipitate carbides, then heating it to Ac3+(10-50)°C and keeping it for 10-15 hours for austenitization, then cooling it to 680±30°C and keeping it for 70-75 hours for isothermal transformation, and then cooling it to room temperature after completion.

[0062] In this optional embodiment, after the φ900mm 16-ton trial product is annealed according to this process, the microstructure is as follows: Fig. 9 As shown, the structure is ferrite + pearlite, without martensite, achieving the effect of isothermal structure transformation. After normalizing, the grain (size) is refined. The microstructure is as follows Fig.10 As shown, the grain size reaches about 50μm, the precision rating is 5.5, breaking the martensitic structure inheritance, and the flaw detection sensitivity is <φ1.6. Fig.11 This is a φ900mm 16-ton trial product before the post-forging annealing process was performed. The initial grain size was 350-500μm, which is 00 grade, and the flaw detection sensitivity is φ3-4.

[0063] A method for annealing a high-alloy martensitic heat-resistant steel rotor after forging provided in an embodiment of the present invention is formulated using the method for formulating a method for annealing a high-alloy martensitic heat-resistant steel rotor after forging as described in any one of the above items.

[0064] Optionally, the following steps are included:

[0065] Take the forged high alloy martensitic heat-resistant steel rotor, heat it to 1050-1100°C and keep it for more than 10 hours to homogenize the grain size, then cool it to 150-250°C and keep it for more than 10 hours to complete the martensitic transformation, then heat it to 680±30°C and keep it for 20-25 hours for pre-tempering to precipitate carbides, then heat it to Ac3+(10-50)°C and keep it for 10-15 hours for austenitization, then cool it to 680±30°C and keep it for 70-75 hours for isothermal transformation, and then cool it to room temperature after completion;

[0066] Among them, the composition of the high alloy martensitic heat-resistant steel rotor includes C: 0.01%-0.14%, Si: 0.05%-0.50%, Mn: 0.05%-0.70%, Cr: 8.5%-13%, W: 2.0%-3.5%, Mo: 0.1%-0.7%, Nb: 0.03%-0.07%, V: 0.1%-0.3%, Co: 2.8%-5%, Cu: 0.5%-1.5%, Ni: 0.1%-0.5%, B: 0.01%-0.015%, N: 0.01%-0.08%, Ta: 0.2%-0.5%, Zr: 0.1%-0.5% and Ce+Y: 0.01%-0.3%.

[0067] In this embodiment, after the high-alloy martensitic heat-resistant steel rotor is annealed according to this annealing process, the structure is ferrite + pearlite without martensite, achieving the effect of isothermal structural transformation. After normalizing, the grain (size) is refined to about 50μm, and the target degree rating is 5.5, breaking the martensitic structural inheritance, and the sensitivity of the flaw detection is <φ1.6.

[0068] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for formulating a post-forging annealing method for a high-alloy martensitic heat-resistant steel rotor, characterized in that: The following steps are involved: S1: Call the JMatPro Fe-General Steel general steel module and its database, input the composition of high-alloy martensitic heat-resistant steel, calculate the austenite phase transformation temperature parameter Ac3, set the grain size level according to the forging completed grain size, set the maximum range of austenitization temperature, and simulate and calculate to obtain the isothermal transformation curve; S2. Compare the effects of different austenitizing temperatures on the isothermal transformation of pearlite, select one or more groups of temperatures corresponding to the shortest pearlite incubation period as the optimal austenitizing temperature range, and select the isothermal transformation temperature range according to the transformation temperature of pearlite; S3. Conduct physical experiments to verify and formulate an experimental plan for the effects of austenitizing temperature and isothermal transformation temperature on the transformation amount of pearlite and ferrite. Compare the time required for the transformation amount of pearlite and ferrite to reach ≥ 90% at different austenitizing temperature and isothermal transformation temperature, and obtain the optimal isothermal transformation temperature with the shortest isothermal transformation time. S4. Using abaqus software, the isothermal process of austenitizing and furnace cooling to the isothermal transformation temperature of a large-section rotor forging with a diameter of more than 900 mm is simulated to obtain the heat treatment temperature curve of the surface and the core of the large-section rotor forging, the time required for the surface and the core of the rotor forging to reach the uniform temperature, and the optimal time parameter of the post-forging annealing process is selected; S5. Develop a post-forging annealing method for high-alloy martensitic heat-resistant steel rotors. After forging, the temperature is raised to homogenize the grain size, then the temperature is lowered to complete the martensitic transformation, then the temperature is raised to the optimal isothermal transformation temperature and kept warm for pre-tempering to precipitate carbides, then the temperature is heated to the optimal austenitizing temperature and kept warm for austenitizing, then the temperature is lowered to the optimal isothermal transformation temperature and kept warm for isothermal transformation, and then the temperature is lowered to room temperature after completion.

2. The method for formulating the post-forging annealing method for a high alloy martensitic heat-resistant steel rotor according to claim 1, characterized in that: The composition of the high alloy martensitic heat-resistant steel rotor includes C: 0.01%-0.14%, Si: 0.05%-0.50%, Mn: 0.05%-0.70%, Cr: 8.5%-13%, W: 2.0%-3.5%, Mo: 0.1%-0.7%, Nb: 0.03%-0.07%, V: 0.1%-0.3%, Co: 2.8%-5%, Cu: 0.5%-1.5%, Ni: 0.1%-0.5%, B: 0.01%-0.015%, N: 0.01%-0.08%, Ta: 0.2%-0.5%, Zr: 0.1%-0.5% and Ce+Y: 0.01%-0.3%.

3. The method for formulating the post-forging annealing method for the high alloy martensitic heat-resistant steel rotor according to claim 2 is characterized in that: In the step S1, the maximum range of austenitizing temperature is set to Ac3+(10-350)°C.

4. The method for formulating the post-forging annealing method for the high alloy martensitic heat-resistant steel rotor according to claim 3 is characterized in that: In the step S2, the temperatures corresponding to the Ac3+10°C group to the Ac3+50°C group with the shortest pearlite incubation period are selected as the range of the optimal austenitizing temperature, and the range of the optimal austenitizing temperature is Ac3+(10-50)°C.

5. The method for formulating the post-forging annealing method for the high alloy martensitic heat-resistant steel rotor according to claim 3 is characterized in that: In the step S2, the transformation temperature of the pearlite is 677-686°C, and the isothermal transformation temperature range is selected to be 680±30°C.

6. The method for formulating the post-forging annealing method for the high alloy martensitic heat-resistant steel rotor according to claim 3, characterized in that: In the step S3, the optimal austenitizing temperature for the shortest isothermal transformation time is Ac3+10°C, and the shortest isothermal transformation time is 50h.

7. The method for formulating the post-forging annealing method for a high alloy martensitic heat-resistant steel rotor according to claim 6, characterized in that: In the step S4, the optimal time parameters of the post-forging annealing process include pre-tempering time and annealing time. The equalization time of the forging surface and the core is set as the pre-tempering time, and the pre-tempering time is 20-25h; the time required for isothermal transformation and the value of the pre-tempering time are set as the annealing time, and the annealing time is 70-75h.

8. The method for formulating the post-forging annealing method for a high alloy martensitic heat-resistant steel rotor according to claim 7, characterized in that: The step S5 specifically includes: formulating a post-forging annealing method for a high-alloy martensitic heat-resistant steel rotor, heating the rotor to 1050-1100°C after forging and keeping the temperature for more than 10 hours to homogenize the grain size, then cooling the rotor to 150-250°C and keeping the temperature for more than 10 hours to complete the martensitic transformation, then heating the rotor to 680±30°C and keeping the temperature for 20-25 hours for pre-tempering to precipitate carbides, then heating the rotor to Ac3+(10-50)°C and keeping the temperature for 10-15 hours for austenitization, then cooling the rotor to 680±30°C and keeping the temperature for 70-75 hours for isothermal transformation, and then cooling the rotor to room temperature after completion.

9. A method for annealing a high alloy martensitic heat-resistant steel rotor after forging, characterized in that: The invention is formulated by adopting the method for annealing a high alloy martensitic heat-resistant steel rotor after forging as described in any one of claims 1 to 8.

10. The post-forging annealing method for a high alloy martensitic heat-resistant steel rotor according to claim 9, characterized in that: The following steps are involved: Take the forged high alloy martensitic heat-resistant steel rotor, heat it to 1050-1150℃ and keep it for more than 10h to homogenize the grain size, then cool it to 150-250℃ and keep it for more than 10h to complete the martensitic transformation, then heat it to 680±30℃ and keep it for 20-25h for pre-tempering to precipitate carbides, then heat it to Ac3+(10-50)℃ and keep it for 10-15h for austenitization, then cool it to 680±30℃ and keep it for 70-75h for isothermal transformation, and then cool it to room temperature after completion; Among them, the composition of the high alloy martensitic heat-resistant steel rotor includes C: 0.01%-0.14%, Si: 0.05%-0.50%, Mn: 0.05%-0.70%, Cr: 8.5%-13%, W: 2.0%-3.5%, Mo: 0.1%-0.7%, Nb: 0.03%-0.07%, V: 0.1%-0.3%, Co: 2.8%-5%, Cu: 0.5%-1.5%, Ni: 0.1%-0.5%, B: 0.01%-0.015%, N: 0.01%-0.08%, Ta: 0.2%-0.5%, Zr: 0.1%-0.5% and Ce+Y: 0.01%-0.3%.

Images