Method for forging large-section 1Cr17Ni2 stainless steel rotor forge piece

Abstract

The invention discloses a forging method of a large-section 1Cr17Ni2 stainless steel rotor forging. The forging method comprises the following steps: heating a steel ingot; forging, wherein the heated steel ingot is sequentially subjected to first upsetting, first rough drawing, second upsetting, second rough drawing, number printing and fine drawing forming on a pressing machine; and heat treatment after forging is conducted, specifically, first-time air cooling, normalizing, second-time air cooling, first-time supercooling, first-time tempering, third-time air cooling, second-time supercooling, second-time tempering, fourth-time air cooling and furnace cooling are sequentially conducted after the forge piece is formed. Initial forging and final forging temperatures are fully considered, generation of high-temperature ferrite is effectively controlled, cracks generated in low-temperature forging are avoided, meanwhile, a proper forging tool is used for improving the stress state of the forge piece, generation of the cracks in the forging process and control over the supercooling temperature and the supercooling time after forging are further avoided, the core structure of the forge piece is fully transformed, and the forging quality is improved. The stainless steel forge piece obtained through the control method is free of cracks and high in flaw detection qualification rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of forging forming technology, in particular to a large-section 1Cr17Ni2 stainless steel rotor forging forging method. BACKGROUND

[0002] 1Cr17Ni2 (Cr17Ni2) martensitic stainless steel is developed on the basis of Cr17 ferritic stainless steel, the content of carbon is increased and about 2% of nickel element is added, which has high strength and good corrosion resistance in oxidizing acid, organic salt solution. It is mainly applied to shaft, piston rod, pump and other parts which require strength and toughness and corrosion resistance. There is a standard specification (GJB5040) for the manufacture of 1Cr17Ni2 stainless steel forgings, but not all forgings can be manufactured according to the specification, which limits the application of the material to some extent. In GBT1220 standard, the tensile strength index of 1Cr17Ni2 steel is determined to be higher (Rm﹥1080Mpa, A﹥10%, AKU2﹥39J), and the recommended tempering temperature is 275-350℃. In actual production process, due to the forging characteristics of 1Cr17Ni2 martensitic stainless steel, the forging is prone to cracking, the flaw detection qualified rate is low, and when the diameter of large step of rotor forging is more than 900mm and the diameter difference between adjacent steps is more than 600mm, the forging difficulty is particularly great. SUMMARY

[0003] The present application provides a large-section 1Cr17Ni2 stainless steel rotor forging forging method, which is not only size qualified, good adaptability, no cracking of the forging, high flaw detection qualified rate, but also has higher toughness and impact value than the standard requirement.

[0004] To achieve the above purpose, the present application provides a large-section 1Cr17Ni2 stainless steel rotor forging forging method, the diameter of the large step of the rotor forging is 900-1100mm; the forging method comprises the following steps: S1) heating of the ingot; S2) forging: the heated ingot is sequentially subjected to first upsetting, first rough drawing, second upsetting, second rough drawing, marking and fine drawing on the press; S3) post-forging heat treatment: the forged piece is sequentially subjected to first air cooling, normalizing, second air cooling, first supercooling, first tempering, third air cooling, second supercooling, second tempering, fourth air cooling and furnace cooling.

[0005] Further, in the step S1), the ingot is heated in a natural gas heating furnace.

[0006] Further, in the step S1), the ingot is heated to 600-650℃, kept for 3-6h, then heated to 800-850℃ at a heating rate of 50-80℃ / h, kept for 3-6h, and finally heated to 1150-1200℃ at a heating rate of 80-100℃ / h, kept for 7-8h.

[0007] Further, in the step S2), the ratio of height to diameter after the first upsetting is 0.80-0.92, the ratio of length to diameter after the first rough drawing is 1.80-2.20, the ratio of height to diameter after the second upsetting is 0.67-0.80, and the ratio of length to diameter after the second rough drawing is 1.20-1.50.

[0008] Further, the first rough drawing and the second rough drawing both use an upper flat anvil and a lower V-shaped anvil, after the step number printing, an upper narrow anvil and a lower narrow anvil are used to draw the two ends, and finally an upper flat anvil and a lower V-shaped anvil are used to precisely draw and form each part of the forged piece.

[0009] Further, the anvil width of the upper flat anvil and the lower V-shaped anvil is 600-800mm, and the anvil width of the upper narrow anvil and the lower narrow anvil is ≤250mm.

[0010] Further, in the step S2), the upper flat anvil, the lower V-shaped anvil, the upper narrow anvil and the lower narrow anvil required for each forging are preheated to 350-450℃ before forging, and the preheating time is not less than 2 hours; when each forging is stopped, the surface temperature of the forged piece is measured by using a temperature measuring gun and should not be lower than 860℃.

[0011] Further, in step S3), the first air cooling of the forging refers to the forced-air cooling of the large step of the forging after forming, with the forced-air cooling reaching a surface temperature of 300-350℃ before loading into the furnace; after loading into the furnace, it is heated to 350-400℃ and held for 1-2 hours per 100mm; after the holding period, the temperature is increased to 620-680℃ at a rate of 50-60℃ / hour and held for 1-2 hours per 100mm; after the holding period, the temperature is increased to 980-100℃ at a rate of 50-60℃ / hour. Normalizing is performed at 020℃, with a holding time of 1-1.5 hours per 100mm. After normalizing, a second air cooling is performed, with forced air blowing on the large steps of the forging for a total duration of 18-24 hours. Within 0.5 hours after stopping forced air blowing, the surface temperature of the large steps is measured with a temperature gun. If the temperature is between 80-130℃, the furnace is set for the first supercooling. The first supercooling involves heating the forging to 100-140℃ and holding it for 2-3 hours per 100mm. After the first supercooling and holding, the first tempering is performed. The forgings are heated to 690-750℃ at a rate of 50-60℃ / h and then tempered and held for 2-3 hours per 100mm. After the first tempering and holding, a third air cooling is performed, and the large steps of the forgings are blasted with air for a total duration of 18-24 hours. Within 0.5 hours after the air is stopped, the surface temperature of the large steps is measured with a temperature gun. If the temperature is 50-100℃, the furnace is set for a second supercooling. The second supercooling involves heating the forgings to 50-100℃ and holding for 1-1.5 hours per 100mm. After the second undercooling, a second tempering is performed, heating the forging to 660-720℃ at a rate of 50-60℃ / h and holding it for 2-3 hours per 100mm. After the second tempering and holding, a fourth air cooling is performed, blowing air onto the large steps of the forging for a total duration of 6-10 hours. Within 0.5 hours after stopping the blowing, the surface temperature of the large steps is measured with a temperature gun. When the temperature reaches 400-450℃, the furnace is set for furnace cooling at a rate of 10-15℃ / h and a furnace cooling temperature of 50-100℃ before the forging is removed from the furnace.

[0012] Furthermore, after the second air cooling process, the small steps at both ends of the forging are wrapped with insulating cotton after 8-12 hours of forced air cooling.

[0013] Furthermore, after the third air cooling process, the small steps at both ends of the forging are wrapped with insulating cotton after 8-12 hours of forced air cooling.

[0014] Compared with existing technologies, the beneficial effects of this invention are as follows: In terms of production process, this invention fully considers the initial and final forging temperatures, effectively controlling the formation of high-temperature ferrite while avoiding cracks caused by low-temperature forging. Simultaneously, it uses suitable forging fixtures to improve the stress state of the forgings, further preventing crack formation during forging. Furthermore, the control of post-forging undercooling temperature and time ensures sufficient transformation of the core structure of the forgings. The stainless steel forgings obtained by combining these control methods are crack-free and have a high flaw detection pass rate. The main properties of the forgings of this invention are: Rm≥800MPa, Rp0.2≥620 MPa, A≥15%, Z≥45%, AKU2≥63J, HB≤285, and grain size≥4.5 grade. All tests passed. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the forging process using a flat anvil on the top and a V-shaped anvil on the bottom, as used in this invention. Figure 2 This is a schematic diagram of the narrow anvil elongation method used in this invention; Figure 3 This is a schematic diagram of the rotor forging structure of the present invention; Figure 4 This is a photograph of the grain size results for Example 1. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0017] like Figure 3 The diameter of the large step 8 in the 1Cr17Ni2 stainless steel rotor forging shown is 900-1100 mm. The forging method of the rotor forging includes the following steps: S1) Steel ingot heating: The steel ingot is heated in a natural gas heating furnace; First, heat the steel ingot to 600-650℃ and hold for 3-6 hours. Then, heat it to 800-850℃ at a heating rate of 50-80℃ / h and hold for 3-6 hours. Finally, heat it to 1150-1200℃ at a heating rate of 80-100℃ / h and hold for 7-8 hours.

[0018] S2) Forging: The heated steel ingot 3 is subjected to the following processes in sequence on a press: first upsetting, first rough drawing, second upsetting, second rough drawing, marking, and fine drawing. Combination Figure 1 , Figure 2As shown, the height-to-diameter ratio of the steel ingot after the first upsetting is 0.80-0.92, the length-to-diameter ratio after the first rough drawing is 1.80-2.20, the height-to-diameter ratio after the second upsetting is 0.67-0.80, and the length-to-diameter ratio after the second rough drawing is 1.20-1.50. Both the first and second rough drawing use an upper flat anvil 1 and a lower V-shaped anvil 2. After the step number 6 is printed, upper narrow anvil 4 and lower narrow anvil 5 are used to draw both ends, ensuring that the ends bulge out with protrusions 7. Finally, upper flat anvil 1 and lower V-shaped anvil 2 are used to finish-draw all parts of the forging into shape.

[0019] The width of both the upper flat anvil and the lower V-shaped anvil is 600-800mm, while the width of both the upper narrow anvil and the lower narrow anvil is ≤250mm. Forging with an upper flat anvil and a lower V-shaped anvil can more effectively transfer pressure to the interior of the forging, resulting in greater triaxial compressive stress on the core of the forging. This helps to compact defects such as porosity and air bubbles inside the forging, improves the density of the forging material, and enhances the internal quality of the forging.

[0020] For each forging operation, the upper flat anvil, lower V-shaped anvil, upper narrow anvil, and lower narrow anvil required for forging should be preheated to 350-450℃ for at least 2 hours. Each time forging stops, the surface temperature of the forging should be measured with a temperature gun and should not be lower than 860℃. Preheating the anvil effectively improves forging efficiency and avoids excessive temperature differences between the forging body and the anvil contact surface, preventing uneven forging temperature and affecting deformation. Controlling the final forging temperature to be no lower than 860℃ ensures that the forging remains within its forgeable temperature range with good plasticity, preventing cracks during forging and thus affecting subsequent flaw detection.

[0021] S3) Post-forging heat treatment: After the forging is formed, it is subjected to the following processes in sequence: first air cooling, normalizing, second air cooling, first supercooling, first tempering, third air cooling, second supercooling, second tempering, fourth air cooling, and furnace cooling. The first air cooling of the forging refers to using a fan to cool the large steps of the forging after forming, until the surface temperature of the large steps reaches 300-350℃, at which point it is loaded into the furnace. After loading, it is heated to 350-400℃ and held for 1-2 hours per 100mm. After holding, the temperature is increased at a rate of 50-60℃ / hour to 620-680℃ and held for 1-2 hours per 100mm. After holding, the temperature is increased at a rate of 50-60℃ / hour to 980-1020℃ for normalizing and holding for 1-1.5 hours. 100mm is executed; after the normalizing and holding period, a second air cooling is performed. The large step 8 of the forging is blasted with a blower for 8-12 hours. Then, insulation cotton is used to wrap the small steps 9 at both ends of the forging. The total blasting time is 18-24 hours. Within 0.5 hours after stopping the blower, the surface temperature of the large step is measured with a temperature gun. If the temperature is 80-130℃, the furnace is set for the first supercooling. The first supercooling involves heating the forging to 100-140℃ and holding it for 2-3 hours per 100mm. After the first supercooling and holding period, the first tempering is performed, with the forging set at 50... Heat the forging at -60℃ / h to 690-750℃ for tempering and holding, with a holding time of 2-3 hours per 100mm. After the first tempering and holding, perform a third air cooling, using a blower to blast the large steps of the forging for 8-12 hours. Then, wrap the small steps at both ends of the forging with insulating cotton, for a total blowing time of 18-24 hours. Within 0.5 hours after stopping the blowing, measure the surface temperature of the large steps with a temperature gun. If the temperature is 50-100℃, start the furnace for the second supercooling. The second supercooling involves heating the forging to 50-100℃ and holding it for 1-1.5 hours. / 100mm execution; after the second undercooling, perform the second tempering, heat the forging to 660-720℃ at a rate of 50-60℃ / h and hold for 2-3h / 100mm; after the second tempering and holding, perform the fourth air cooling, use a blower to blow air onto the large step of the forging, the total blowing time is 6-10h; within 0.5h after stopping the blowing, use a temperature gun to measure the surface temperature of the large step, and when the temperature is 400-450℃, put it into the furnace for furnace cooling, the furnace cooling rate is 10-15℃ / h, and the furnace cooling temperature is 50-100℃ when it is taken out of the furnace.

[0022] Due to the dimensional deviation between the small steps at both ends of the rotor and the large step in the middle, the temperature and microstructure transformation rate are inconsistent during heat treatment. Simultaneously, the large step section is too large, resulting in inconsistent microstructure transformation rates between the outer layer and the core. Furthermore, the 1Cr17Ni2 (Cr17Ni2) material is prone to martensitic transformation under air cooling conditions. Excessive superposition of temperature stress and microstructure transformation stress at each stage of heat treatment can lead to cracking. To ensure that the temperature and microstructure transformation rate of the inner and outer layers of the small and large steps are more consistent and to reduce internal stress, blowers are used to enhance the cooling rate of the large step during the post-forging air cooling stage, the normalizing air cooling stage, the first tempering air cooling stage, and the second tempering air cooling stage. During the normalizing air cooling stage and the first tempering air cooling stage, insulation cotton is used to slow down the cooling rate of the small step. This improves the temperature gradient in each part and reduces temperature stress.

[0023] To reduce the temperature difference between the workpiece and the furnace during the tempering stage, the workpiece loading temperature must be strictly controlled. The workpiece surface temperature should be measured before loading, and the surface temperature should be slightly lower than the supercooling holding temperature by 30-50℃. To avoid excessive retained austenite in the large-step core, which could lead to continued martensitic transformation during subsequent tempering and air cooling, causing core expansion and cracking, a two-stage supercooling followed by two-stage tempering process is employed after normalizing. Both supercooling temperatures are below the Ms point. The first supercooling completes most of the austenite-to-martensite transformation, and the second supercooling temperature, lower than the first, further reduces austenite residue, promoting further transformation of the austenite core to martensite, preventing core cracking, and eliminating internal transformation stress.

[0024] Example 1 S1) Heat the steel ingot to 650℃, hold for 3 hours, then heat to 800℃ at a heating rate of 50℃ / h and hold for 3 hours. Finally, heat to 1150℃ at a heating rate of 80℃ / h and hold for 7.5 hours.

[0025] (S2) The ratio of height to diameter of the steel ingot after the first upsetting is 0.85, the ratio of length to diameter after the first rough drawing is 1.90, the ratio of height to diameter after the second upsetting is 0.72, and the ratio of length to diameter after the second rough drawing is 1.20. Both drawing operations use an upper flat anvil 1 and a lower V-shaped anvil 2. After the step number is marked 6, upper narrow anvil 4 and lower narrow anvil 5 are used to draw the ends, ensuring that the ends bulge out at both ends 7. Finally, upper flat anvil 1 and lower V-shaped anvil 2 are used again to finish-draw all parts of the forging. Furthermore, the upper flat anvil, lower V-shaped anvil, upper narrow anvil, and lower narrow anvil required for forging are preheated to 350-450℃ for at least 2 hours before each forging operation. Each time forging is stopped, the surface temperature of the forging is measured with a temperature gun and must not be lower than 860℃.

[0026] S3) After the forging is formed, it is first air-cooled until the surface temperature of the large step reaches 300℃, then loaded into the furnace. After loading, it is heated to 350℃ and held for 18 hours, then heated to 680℃ at a rate of 60℃ / h and held for 18 hours; then heated to 980℃ at a rate of 50℃ / h for normalizing and held for 14 hours; after the normalizing holding, it is air-cooled a second time, and the large step of the forging is blasted with a blower for 10 hours. After blasting, the small steps at both ends of the forging are wrapped with insulation cotton, and the total blasting time is 22 hours; within 0.5 hours after the blasting stops, the temperature is measured at 80℃ before loading into the furnace for the first supercooling; the first supercooling is held at 100℃ for 27 hours; after the first supercooling, the first tempering is performed, heated to 690℃ at a rate of 50℃ / h and held for 27 hours; the first... After tempering, a third air cooling is performed, using a blower to blast the large steps of the forging for 10 hours. Then, insulation cotton is used to wrap the small steps at both ends of the forging. The total blasting time is 22 hours. Within 0.5 hours after the blasting stops, the temperature is measured at 60°C and the forging is then placed in the furnace for a second supercooling. The second supercooling involves heating the forging to 80°C and holding it for 14 hours. After the second supercooling, a second tempering is performed, heating the forging to 660°C at a rate of 50°C / h and holding it for 27 hours. After the second tempering and holding, a fourth air cooling is performed, using a blower to blast the large steps of the forging for a total blasting time of 10 hours. Within 0.5 hours after the blasting stops, the temperature is measured at 450°C and the forging is then placed in the furnace for furnace cooling at a rate of 15°C / h and a furnace cooling temperature of 100°C before unloading.

[0027] A large-section 1Cr17Ni2 stainless steel rotor forging with no cracks and passing flaw detection was obtained. For example... Figure 4 The method of this invention, as shown, results in a final product with a grain size level that exceeds the acceptance level requirements.

[0028] Example 2 S1) Heat the steel ingot to 600℃, hold for 6 hours, then heat to 820℃ at a heating rate of 60℃ / h and hold for 4 hours. Finally, heat to 1150℃ at a heating rate of 90℃ / h and hold for 8 hours.

[0029] (S2) The ratio of height to diameter of the steel ingot after the first upsetting is 0.88, the ratio of length to diameter after the first rough drawing is 1.95, the ratio of height to diameter after the second upsetting is 0.75, and the ratio of length to diameter after the second rough drawing is 1.35. Both drawing operations use an upper flat anvil 1 and a lower V-shaped anvil 2. After the step number is marked 6, upper narrow anvil 4 and lower narrow anvil 5 are used to draw the ends, ensuring that the ends bulge out at both ends 7. Finally, upper flat anvil 1 and lower V-shaped anvil 2 are used again to finish-draw all parts of the forging. Furthermore, the upper flat anvil, lower V-shaped anvil, upper narrow anvil, and lower narrow anvil required for forging are preheated to 350-450℃ for at least 2 hours before each forging operation. Each time forging stops, the surface temperature of the forging is measured with a temperature gun and must not be lower than 860℃.

[0030] S3) After the forging is formed, it is first air-cooled until the surface temperature of the large step reaches 320℃, then loaded into the furnace. After loading, it is heated to 370℃ and held for 18 hours, then heated to 680℃ at a rate of 50℃ / h and held for 10 hours; then heated to 1000℃ at a rate of 55℃ / h for normalizing and held for 12 hours; after the normalizing and holding period, it is air-cooled a second time, and the large step of the forging is blasted with a blower for 10 hours. After blasting, the small steps at both ends of the forging are wrapped with insulation cotton, and the total blasting time is 22 hours; within 0.5 hours after the blasting stops, the temperature is measured at 80℃ before loading into the furnace for the first supercooling; the first supercooling is held at 120℃ for 27 hours, and after the first supercooling, the first tempering is performed, heated to 720℃ at a rate of 55℃ / h and held for 25 hours; the first After the first tempering, a third air cooling is performed, using a blower to blast the large steps of the forging for 10 hours. Then, insulation cotton is used to wrap the small steps at both ends of the forging. The total blasting time is 22 hours. Within 0.5 hours after the blasting stops, the temperature is measured at 80°C, and the forging is then placed in the furnace for a second supercooling. The second supercooling involves heating the forging to 50°C and holding it for 14 hours. After the second supercooling, a second tempering is performed, heating the forging to 700°C at a rate of 55°C / h and holding it for 27 hours. After the second tempering and holding, a fourth air cooling is performed, using a blower to blast the large steps of the forging for a total blasting time of 10 hours. Within 0.5 hours after the blasting stops, the temperature is measured at 400°C, and the forging is then placed in the furnace for furnace cooling at a rate of 12°C / h and a furnace cooling temperature of 80°C before unloading.

[0031] A large-section 1Cr17Ni2 stainless steel rotor forging with no cracks and passing flaw detection was obtained.

[0032] Example 3 S1) Heat the steel ingot to 630℃, hold for 6 hours, then heat to 850℃ at a heating rate of 80℃ / h and hold for 5 hours. Finally, heat to 1200℃ at a heating rate of 100℃ / h and hold for 7 hours.

[0033] (S2) The ratio of height to diameter of the steel ingot after the first upsetting is 0.92, the ratio of length to diameter after the first rough drawing is 2.15, the ratio of height to diameter after the second upsetting is 0.80, and the ratio of length to diameter after the second rough drawing is 1.50. Both drawing operations use an upper flat anvil 1 and a lower V-shaped anvil 2. After the step number is marked 6, upper narrow anvil 4 and lower narrow anvil 5 are used to draw the ends, ensuring that the ends bulge out at both ends 7. Finally, upper flat anvil 1 and lower V-shaped anvil 2 are used again to finish-draw all parts of the forging. Furthermore, the upper flat anvil, lower V-shaped anvil, upper narrow anvil, and lower narrow anvil required for forging are preheated to 350-450℃ for at least 2 hours before each forging operation. Each time forging is stopped, the surface temperature of the forging is measured with a temperature gun and must not be lower than 860℃.

[0034] S3) After the forging is formed, it is first air-cooled until the surface temperature of the large step reaches 350℃, then loaded into the furnace. After loading, it is heated to 400℃ and held for 10 hours, then heated to 650℃ at a rate of 55℃ / h and held for 18 hours; then heated to 1020℃ at a rate of 60℃ / h for normalizing and held for 10 hours; after the normalizing holding, it is air-cooled a second time, and the large step of the forging is blasted with a blower for 10 hours. After blasting, the small steps at both ends of the forging are wrapped with insulation cotton. The total blasting time is 22 hours; within 0.5 hours after the blasting stops, the temperature is measured at 130℃ before loading into the furnace for the first supercooling; the first supercooling is held at 140℃ for 18 hours, and after the first supercooling, the first tempering is performed, heated to 750℃ at a rate of 60℃ / h and held for 18 hours; the first... After the first tempering, a third air cooling is performed, using a blower to blast the large steps of the forging for 10 hours. Then, insulation cotton is used to wrap the small steps at both ends of the forging. The total blasting time is 22 hours. Within 0.5 hours after the blasting stops, the temperature is measured at 100℃ before the furnace is set for a second supercooling. The second supercooling involves heating the forging to 100℃ and holding it for 8 hours. After the second supercooling, a second tempering is performed, heating the forging to 720℃ at a rate of 60℃ / h and holding it for 18 hours. After the second tempering and holding, a fourth air cooling is performed, using a blower to blast the large steps of the forging for a total blasting time of 10 hours. Within 0.5 hours after the blasting stops, the temperature is measured at 400℃ before the furnace is set for furnace cooling at a rate of 10℃ / h and a furnace cooling temperature of 50℃ before the forging is removed from the furnace.

[0035] A large-section 1Cr17Ni2 stainless steel rotor forging with no cracks and passing flaw detection was obtained.

[0036] Table 1 Results of Mechanical Property Tests This invention fully considers the influence of forging temperature range, forging tooling on stainless steel forming, post-forging heat treatment temperature, supercooling time, and the transformation of the internal structure of the forging during the forging process. The resulting stainless steel forgings are crack-free and have a high failure rate in flaw detection. The main properties of the forgings produced by this invention are: Rm≥800MPa, Rp0.2≥620 MPa, A≥15%, Z≥45%, AKU2≥63J, HB≤285, and grain size≥4.5 grade; all tests are passed.

Claims

1. A forging method for a large-section 1Cr17Ni2 stainless steel rotor forging, wherein the diameter of the large step of the rotor forging is 900-1100 mm; characterized in that: The forging method includes the following steps: S1) Heating of steel ingots; S2) Forging: The heated steel ingot is subjected to the following processes in sequence on a press: first upsetting, first rough drawing, second upsetting, second rough drawing, marking, and fine drawing. S3) Post-forging heat treatment: After the forging is formed, it is subjected to the following processes in sequence: first air cooling, normalizing, second air cooling, first supercooling, first tempering, third air cooling, second supercooling, second tempering, fourth air cooling, and furnace cooling.

2. The forging method for large-section 1Cr17Ni2 stainless steel rotor forgings according to claim 1, characterized in that: In step S1), the steel ingot is heated in a natural gas heating furnace.

3. The forging method for large-section 1Cr17Ni2 stainless steel rotor forgings according to claim 1, characterized in that: In step S1), the steel ingot is first heated to 600-650℃ and held for 3-6 hours, then heated to 800-850℃ at a heating rate of 50-80℃ / h and held for 3-6 hours, and finally heated to 1150-1200℃ at a heating rate of 80-100℃ / h and held for 7-8 hours.

4. The forging method for large-section 1Cr17Ni2 stainless steel rotor forgings according to claim 1, characterized in that: In step S2), the ratio of the height to the diameter of the steel ingot after the first upsetting is 0.80-0.92, the ratio of the length to the diameter after the first rough drawing is 1.80-2.20, the ratio of the height to the diameter after the second upsetting is 0.67-0.80, and the ratio of the length to the diameter after the second rough drawing is 1.20-1.

50.

5. The forging method for large-section 1Cr17Ni2 stainless steel rotor forgings according to claim 4, characterized in that: The first and second rough drawing processes both use an upper flat anvil and a lower V-shaped anvil. After the step number is printed, the upper narrow anvil and lower narrow anvil are used to draw the two ends. Finally, the upper flat anvil and lower V-shaped anvil are used to finish drawing each part of the forging.

6. The forging method for large-section 1Cr17Ni2 stainless steel rotor forgings according to claim 5, characterized in that: The width of the upper flat anvil and the lower V-shaped anvil is 600-800mm, and the width of the upper narrow anvil and the lower narrow anvil is ≤250mm.

7. The forging method for large-section 1Cr17Ni2 stainless steel rotor forgings according to claim 1, characterized in that: In step S2), the upper flat anvil, lower V-shaped anvil, upper narrow anvil, and lower narrow anvil required for forging are preheated to 350-450°C for each forging operation, and the preheating time is not less than 2 hours. Each time forging is stopped, the surface temperature of the forging is measured with a temperature gun and is not lower than 860°C.

8. The forging method for large-section 1Cr17Ni2 stainless steel rotor forgings according to claim 1, characterized in that: In step S3), the first air cooling of the forging refers to the forced air cooling of the large step of the forging after forming. The forging is cooled until the surface temperature of the large step reaches 300-350℃ before being loaded into the furnace. After loading, it is heated to 350-400℃ and held for 1-2 hours per 100mm. After holding, the temperature is increased to 620-680℃ at a rate of 50-60℃ / hour and held for 1-2 hours per 100mm. After holding, the temperature is increased to 980-1020℃ at a rate of 50-60℃ / hour. Normalizing and holding are performed for 1-1.5 hours per 100mm. After normalizing and holding, a second air cooling is performed, with forced air blowing on the large steps of the forging for a total duration of 18-24 hours. Within 0.5 hours after stopping forced air blowing, the surface temperature of the large steps is measured with a temperature gun. When the temperature reaches 80-130℃, the furnace is refrigerated for the first supercooling. The first supercooling involves heating the forging to 100-140℃ and holding it for 2-3 hours per 100mm. After the first supercooling and holding, the forging is tempered for the first time. Heat the forging at 50-60℃ / h to 690-750℃ for tempering and holding, with a holding time of 2-3 hours per 100mm. After the first tempering and holding, perform a third air cooling, blowing air onto the large steps of the forging for a total duration of 18-24 hours. Within 0.5 hours after stopping the blowing, measure the surface temperature of the large steps with a temperature gun. If the temperature is 50-100℃, start the furnace for a second supercooling. The second supercooling involves heating the forging to 50-100℃ and holding it for 1-1.5 hours per 100mm. After the second undercooling, a second tempering is performed, where the forging is heated to 660-720℃ at a rate of 50-60℃ / h and held for 2-3 hours per 100mm. After the second tempering and holding, a fourth air cooling is performed, where the large step of the forging is blasted with air for a total duration of 6-10 hours. Within 0.5 hours after the air is stopped, the surface temperature of the large step is measured with a temperature gun. When the temperature reaches 400-450℃, the furnace is set for furnace cooling at a rate of 10-15℃ / h and a furnace cooling temperature of 50-100℃ before the forging is removed from the furnace.

9. The forging method for large-section 1Cr17Ni2 stainless steel rotor forgings according to claim 8, characterized in that: After the second air cooling process, which involves blowing air for 8-12 hours, the small steps at both ends of the forging are wrapped with insulating cotton.

10. The forging method for large-section 1Cr17Ni2 stainless steel rotor forgings according to claim 8, characterized in that: During the third air cooling process, after 8-12 hours of blowing air, the small steps at both ends of the forging are wrapped with insulating cotton.

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