Forging method for forging of shaft head of low-pressure welded rotor of steam turbine

Abstract

The present invention relates to the technical field of steam turbine rotor manufacturing, and specifically to a forging method for a forging of a low-pressure welded rotor shaft head of a steam turbine. S1: Forging the initial blank; S2: Upsetting and drawing out; S3: Machining the cylindrical section and the conical section; S4: Upsetting the cylindrical section; S5: Forming a boss on the upper surface of the cylindrical section; S6: Pressing out the groove around the boss; S7: Forming the small flange, the rod part and the lifting chuck. The invention conducts upsetting and drawing out on the initial blank for multiple times, and the drawing ratio each time is not less than 2.5, which can effectively forge and combine the internal hole defects of the initial forging to meet the flaw detection requirements. Each part of the product is qualified after ultrasonic flaw detection. The invention forges by first forming the large flange at high temperature and then cooling down to form the rod part and the small flange, which solves the problem of the formation of the large flange and the compaction of the internal defects. Cooling down to form the rod part and the small flange can effectively prevent the excessive growth of the grains of the large flange when forging the rod part and the small flange, and can effectively control the coarse grains inside the forging.

Description

Technical Field

[0001] The present invention relates to the technical field of steam turbine rotor manufacturing, and particularly to a forging method for a forging of a low-pressure welded rotor shaft head of a steam turbine. Background Art

[0002] As one of the core components of a steam turbine, the low-pressure rotor of a nuclear power steam turbine is composed of multiple-stage discs welded to the shaft heads at both ends. Each forging has characteristics such as large size, strict quality requirements, and high requirements for performance uniformity, making the manufacturing extremely difficult. Especially as the size of the forging increases, it becomes difficult to compact the internal defects of the ingot, which poses a great challenge to the extremely strict ultrasonic flaw detection requirements. This requires coordinated control of the forging of internal defects and the deformation process.

[0003] The structure of the forging of the low-pressure welded rotor shaft head is as Figure 1 shown, and it mainly consists of a small flange 1, a rod part 2, a large flange 3, a boss 4, a groove 5, and a lifting chuck 6. The lifting chuck 6 is connected to the small flange 1 and is mainly used for lifting the workpiece during heating in a pit furnace for performance heat treatment.

[0004] With the development of steam turbine technology, the designed size of the forging of the low-pressure welded rotor shaft head is getting larger and larger. Especially in the field of nuclear power, the diameter D of the large flange of the low-pressure rotor shaft head forging exceeds 3 meters, the length L1 exceeds 1 meter, the diameter of the remaining rod part is 1 - 1.5 meters, and the total length L of the rotor shaft head forging exceeds 5 meters.

[0005] For the manufacturing of the large flange of the rotor shaft head forging, the drawing-out method is generally used for forming. However, since the diameter of the large flange exceeds 3 meters, it is necessary to first manufacture a steel billet with a diameter larger than that of the large flange. However, the aspect ratio of the height and width of the steel billet is too large, and due to the short dividing length of the small-diameter rod part, during the process of drawing out the rod part, the deformation of the core and the outer circle is uneven, resulting in a concave defect on the end face of the rod part. At the same time, the excessive drawing ratio of the rod part requires multiple heating at high temperatures for a long time, which is extremely likely to cause grain growth of the large flange. Therefore, the present invention proposes a forming process method that can effectively solve the forging and compaction of internal defects in large steel ingots and achieve the shape and property control of each part of the forging. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a forging method for a forging of a welded rotor shaft head of a steam turbine, which is used for manufacturing a large-sized forging of a low-pressure welded rotor shaft head.

[0007] The technical solution adopted by the present invention to solve its technical problems is a forging method for a forging of a welded rotor shaft head of a steam turbine, which includes the following steps:

[0008] S1: Forge the initial blank from the ingot. The initial blank includes a tong handle section and an ingot body section, and the tong handle section and the ingot body section are coaxial. The ingot body section is obtained by cutting a certain proportion of the nozzle section from the ingot body.

[0009] S2: Upset and draw out. Heat the initial blank to the first temperature, and take it out of the furnace after the core of the initial blank reaches the temperature. Put the tong handle section into the upsetting die, place a flat upsetting plate on the upper part of the ingot body section, and upset the ingot body section by pressing the flat upsetting plate with a press. After upsetting, take the initial blank out of the upsetting die, and draw out the ingot body section to form the second blank.

[0010] S3: Heat the second blank to the first temperature, take it out of the furnace after the core of the second blank reaches the temperature, forge the ingot body section of the second blank into a cylindrical section and a conical section, cut off the tong handle section, and flatten the end of the conical section to form the third blank.

[0011] S4: Heat the third blank to the first temperature, take it out of the furnace after the core of the third blank reaches the temperature, and put the conical section into the upsetting die. A conical hole adapted to the conical section is provided in the upsetting die. A forging plate is arranged above the cylindrical section, and the cylindrical section is upset by pressing the forging plate with a press. After completion, take the third blank out of the upsetting die, and then perform rotary forging on the cylindrical section to eliminate the side bulging of the cylindrical section to form the fourth blank.

[0012] S5: Heat the fourth blank to the second temperature, which is lower than the first temperature, take it out of the furnace after the core of the fourth blank reaches the temperature, and put the conical section into the upsetting die. After placing the flat upsetting plate on the cylindrical section and upsetting and flattening it, then install the ring cutter. The ring cutter is coaxial with the cylindrical section. The press presses down the ring cutter to perform radial feeding on the cylindrical section. Finally, use a flat anvil to perform rotary rolling on the periphery of the boss to form a boss on the upper surface of the cylindrical section to form the fifth blank.

[0013] S6: Heat the fifth blank to the third temperature, which is lower than the second temperature, take it out of the furnace after the core of the fifth blank reaches the temperature, roll the cylindrical section to the diameter size D of the large flange of the forging. After rolling, place the conical section into the upsetting die, and use a flat anvil to perform rotary rolling on the periphery of the boss to the length L1 of the large flange. After rolling, put the pressing ring on the boss, and the press presses down the pressing ring to press out the groove around the boss to form the sixth blank.

[0014] S7: Heat the sixth blank to the second temperature, take it out of the furnace after the core of the conical section of the sixth blank reaches the temperature, and use an upper flat and lower V-shaped anvil to draw out the conical section to finally form the small flange, the rod part and the lifting chuck.

[0015] Furthermore, in step S1, the tong handle section is forged from the ingot riser, and the cutting ratio of the nozzle of the ingot body section is not less than 7% of the weight of the ingot. In step S2, the upsetting ratio of the ingot body section is 1.8 - 2.2.

[0016] Further, in step S2, the WHF method is adopted for stretching the ingot body section. When using the WHF method for stretching, the initial anvil width ratio is required to be 0.6 - 0.8, and it is stretched according to the pressing program for 10 - 12 passes, with a stretching ratio of 2.5 - 3.

[0017] Further, in step S3, the taper of the conical section is 3 - 5°.

[0018] Further, in step S3, the length of the cylindrical section is H0, the length of the conical section is H1, and the minimum diameter of the conical section is d1, where H0 = (2.5 - 3.5)L1, d1 = (1.2 - 1.5)D1, L1 is the length of the large flange, and D1 is the diameter of the small flange.

[0019] Further, in step S4, the forging plate is a conical plate. The conical part of the conical plate faces the cylindrical section and is coaxial with the cylindrical section. The press presses down the conical plate to upset the cylindrical section; after upsetting the cylindrical section, a flat anvil is used to perform rotary rolling on the upper surface of the cylindrical section.

[0020] Further, in step S4, after forging with the conical plate, the linear distance from the lowest point of the upper surface of the cylindrical section to the lower surface of the cylindrical section is H2. After performing rotary rolling on the upper surface of the cylindrical section with a flat anvil, the linear distance from the upper surface of the cylindrical section to the lower surface of the cylindrical section is H3. Among them, H0 / H2 = (1.7 - 2.2), H2 = H3 + (100 mm - 200 mm), and L1 / H3 = (0.7 - 0.9), where L1 is the length of the large flange.

[0021] Further, the value range of the first temperature is 1230 - 1270 °C, the value range of the second temperature is 1160 - 1230 °C, and the value range of the third temperature is 1120 - 1160 °C. Among them, the heating temperature in step S2 takes the upper-middle limit of the first temperature.

[0022] Further, after step S2, step S2 is repeated to upset and stretch the initial blank, and it is repeated at least 2 times.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. The invention upsets and stretches the initial blank multiple times, and the stretching ratio each time is not less than 2.5, which can effectively forge and combine the internal hole defects of the initial blank to meet the flaw detection requirements, and all parts of the product are qualified after ultrasonic flaw detection.

[0025] 2. The invention adopts a special mold and rotary rolling of the upper flat anvil on the large flange, and uses reasonable deformation parameters to reduce the forging forming load under the stress condition of further compacting internal defects, making the dimensions and internal deformation degree of the forging more uniform.

[0026] 3. The invention forges by first forming the large flange at high temperature and then forming the rod part and the small flange after cooling, which solves the difficulties in forming the large flange and the compaction of internal defects. Forming the rod part and the small flange after cooling can effectively prevent the excessive growth of the grains of the large flange when forging the rod part and the small flange, and can effectively control the coarse grains inside the forging. Description of the Drawings

[0027] Figure 1 is a schematic structural diagram of a rotor shaft head forging;

[0028] Figure 2 is a schematic diagram of the initial blank;

[0029] Figure 3 is a schematic diagram of upsetting and drawing out the initial blank to form a second blank;

[0030] Figure 4 is a schematic diagram of forming a third blank from the second blank;

[0031] Figures 5A - 5B is a schematic diagram of upsetting the third blank;

[0032] Figure 6 is a schematic diagram of rotary upsetting and spreading the upset third blank in a die;

[0033] Figure 7 is for Figure 6 to form a fourth blank by rolling;

[0034] Figures 8A - 8C are respectively schematic diagrams of upsetting, using an upper ring cutter, and rotary upsetting and spreading the fourth blank to form a fifth blank;

[0035] Figures 9A - 9B is a schematic diagram of forming a sixth blank from the fifth blank.

[0036] Reference numerals: 1 - small flange; 2 - rod part; 3 - large flange; 4 - boss; 5 - groove; 6 - lifting chuck; 9 - nozzle section; 10 - tong handle section; 11 - ingot body section; 12 - upsetting leak pan; 13 - flat upsetting plate; 14 - cylindrical section; 15 - conical section; 16 - upsetting die; 17 - press forging plate; 18 - flat anvil; 19 - ring cutter; 20 - pressing ring. Detailed Description of the Invention

[0037] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0038] As Figures 2 - 9BAs shown in the figure, a forging method for a forged part of a steam turbine welded rotor shaft head according to the present invention includes the following steps:

[0039] S1: Forging an initial blank from an ingot. The initial blank includes a tong portion 10 and an ingot body portion 11, and the tong portion 10 and the ingot body portion 11 are coaxial. The ingot body portion 11 is obtained by cutting a certain proportion of the nozzle section 9 from the ingot body of the steel ingot.

[0040] S2: Upsetting and drawing out. Heat the initial blank to a first temperature, and take it out of the furnace after the core of the initial blank reaches the temperature. Place the tong portion 10 into the upsetting leak plate 12, and place a flat upsetting plate 13 on the upper part of the ingot body portion 11. Press the flat upsetting plate 13 by a press to upset the ingot body portion 11. After upsetting is completed, take the initial blank out of the upsetting leak plate 12, and draw out the ingot body portion 11 to form a second blank.

[0041] S3: Heat the second blank to the first temperature, and take it out of the furnace after the core of the second blank reaches the temperature. Forge the ingot body portion 11 of the second blank into a cylindrical section 14 and a conical section 15, cut off the tong portion 10, and flatten the end of the conical section 15 to form a third blank.

[0042] S4: Heat the third blank to the first temperature, and take it out of the furnace after the core of the third blank reaches the temperature. Place the conical section 15 into the upsetting die 16. A conical hole adapted to the conical section 15 is provided in the upsetting die 16. A forging plate 17 is arranged above the cylindrical section 14. Press the forging plate 17 by a press to upset the cylindrical section 14. After completion, take the third blank out of the upsetting die 16, and then perform rotary forging on the cylindrical section 14 to eliminate the side bulging of the cylindrical section 14 to form a fourth blank.

[0043] S5: Heat the fourth blank to a second temperature, and the second temperature is lower than the first temperature. Take it out of the furnace after the core of the fourth blank reaches the temperature. Place the conical section 15 into the upsetting die 16. Place the flat upsetting plate 13 on the cylindrical section 14 and then perform upsetting and leveling. Then, place the ring cutter 19, and the ring cutter 19 is coaxial with the cylindrical section 14. Press the ring cutter 19 by the press to perform radial feeding on the cylindrical section 14. Finally, use a flat anvil 18 to perform rotary rolling on the periphery of the boss 4 to form a boss 4 on the upper surface of the cylindrical section 14 to form a fifth blank.

[0044] S6: Heat the fifth blank to the second temperature, and take it out of the furnace after the core of the fifth blank reaches the temperature. Roll the cylindrical section 14 to the diameter size D of the large flange 3 of the forging. After rolling, place the conical section 15 into the upsetting die 16, and use a flat anvil 18 to perform rotary rolling on the periphery of the boss 4 to the length L1 of the large flange 3. After rolling is completed, place the pressing ring 20 on the boss 4, and press the pressing ring 20 by the press to press out the groove 5 around the boss 4 to form a sixth blank.

[0045] S7: Heat the sixth blank to the third temperature. After the core of the conical section 15 of the sixth blank reaches the required temperature, take it out of the furnace, and use an upper flat and lower V anvil to stretch the conical section 15, finally forming the small flange 1, the rod part 2, and the lifting chuck 6.

[0046] Further, in step S1, the clamp handle section is forged from the ingot riser, and the cutting ratio of the nozzle section 9 of the ingot body section is not less than 7% of the ingot weight; in step S2, the upsetting ratio of the ingot body section 11 is 1.8 - 2.2.

[0047] Further, in step S2, the WHF method is used to stretch the ingot body section 11. When using the WHF method for stretching, the initial anvil width ratio is required to be 0.6 - 0.8, and it is stretched according to the forging reduction program for 10 - 12 passes, and the stretching ratio is 2.5 - 3.

[0048] Further, in step S3, the taper of the conical section 15 is 3 - 5°.

[0049] Further, in step S3, the length of the cylindrical section 14 is H0, the length of the conical section 15 is H1, and the minimum diameter of the conical section 15 is d1, where H0 = (2.5 - 3.5)L1, d1 = (1.2 - 1.5)D1, L1 is the length of the large flange 3, and D1 is the diameter of the small flange 1.

[0050] Further, in step S4, the forging plate 17 is a conical plate. The conical part of the conical plate faces the cylindrical section 14 and is coaxial with the cylindrical section 14. The press presses down the conical plate to upset the cylindrical section 14; after upsetting the cylindrical section 14, use the flat anvil 18 to perform rotary spreading on the upper surface of the cylindrical section 14. By pressing the cylindrical section 14 with the conical plate, the conical tip part of the conical plate can better apply pressure to the cylindrical section 14, so that a conical groove is formed on the upper surface of the cylindrical section 14, and then use the flat anvil 18 to spread around the conical groove, which can reduce the working pressure of the press.

[0051] Further, in step S4, after forging with the conical plate, the straight-line distance from the lowest point on the upper surface of the cylindrical section 14 to the lower surface of the cylindrical section 14 is H2. After using the flat anvil 18 to perform rotary spreading on the upper surface of the cylindrical section 14, the straight-line distance from the upper surface of the cylindrical section 14 to the lower surface of the cylindrical section 14 is H3, where H0 / H2 = (1.7 - 2.2), H2 = H3 + (100 mm - 200 mm), and L1 / H3 = (0.7 - 0.9), and L1 is the length of the large flange 3.

[0052] Further, the value range of the first temperature is 1230 - 1270 °C, the value range of the second temperature is 1160 - 1230 °C, and the value range of the third temperature is 1120 - 1160 °C. Among them, the heating temperature in step S2 takes the upper-middle limit of the first temperature, which is 1250 - 1270 °C.

[0053] Further, after step S2, step S2 is repeated to upset and draw out the initial blank, and it is repeated at least 2 times.

[0054] Example 1

[0055] In this example, an 180t double-vacuum ingot is used as the forging raw material, and the material is 25Cr2Ni2MoV. After forging and forming, the large flange 3 of the rotor shaft head forging has a diameter D = 3050mm, a length L1 = 950mm, the diameter of the small flange 1 is D1 = 1500mm, and the weight of the rotor shaft head forging is about 100 tons. The forging method is as follows:

[0056] (1) After the ingot is hot-delivered, it is heated to 1230°C according to a special heating process, held for 22 hours, and then the forging tong handle section 10 and the ingot body section 11 are forged, and the nozzle section 9 at the end of the ingot body section 11 is cut off. The cutting ratio of the nozzle section 9 is 7.3% to form the initial blank. The schematic diagram is as Figure 2 shown.

[0057] (2) After the blank is heated to 1250°C and held for 29 hours, the ingot body section 11 is upset on a 160MN press using the upper flat upsetting plate 13 and the lower upsetting leaky plate 12. The upsetting ratio is 2.1, and the WHF method is used for drawing out with a wide anvil with an initial anvil width ratio of 0.65, and it is drawn out for 12 passes, and the drawing ratio is about 2.7. The heating system for the second upsetting and drawing out is the same as that of the first time. After upsetting, it is drawn out to the 10th pass, and the drawing ratio is about 2.5. After the WHF method of drawing out, it is pressed into an octagon to form the second blank. The schematic diagram is as Figure 3 shown.

[0058] (3) After the second blank is heated to 1230°C and held for 18 hours, the ingot body section 11 is forged on a 160MN press using the upper flat and lower V-shaped anvils to form the cylindrical section 14 and the conical section 15, the tong handle section 10 is cut off, and the end of the conical section 15 is flattened to form the third blank. Among them, the length of the cylindrical section 14 is H0 = 2850mm, H1 = 2100mm, and the minimum diameter of the conical section 15 is d1 = 1700mm. The schematic diagram is as Figure 4 shown.

[0059] (4) After the third blank is heated to 1230°C and held for 23 hours, the conical section 15 is placed in the upsetting die 16, and the cylindrical section 14 is upset in the die on a 160MN press using the conical plate. After upsetting, the distance H2 from the lowest point on the upper surface of the cylindrical section 14 to the lower surface of the cylindrical section 14 is 1400mm. The schematic diagrams are as Figure 5A and Figure 5B shown. Subsequently, the upper surface of the cylindrical section 14 is rotated and rolled with the flat anvil 18 until the length H3 of the cylindrical section 14 is 1300mm. The schematic diagram is as Figure 6As shown. After the rolling is completed, the third blank is taken out of the leakage tray, and the upper flat and lower V-shaped anvil is used to roll the large flange 3 to eliminate the bulging, forming the fourth blank. The schematic diagram is as Figure 7 shown.

[0060] (5) After heating the fourth blank to 1190 °C and holding for 22 hours, the flat upsetting plate 13 is placed on the cylindrical section 14 and then upset and flattened. Then, the upper ring cutter 19 is used. The ring cutter 19 is coaxial with the cylindrical section 14. The press presses down the ring cutter 19 to radially distribute the material on the cylindrical section 14, forming a boss 4 on the upper surface of the cylindrical section 14. Finally, the flat anvil 18 is used to rotate and roll the periphery of the boss 4 to form the fifth blank; the schematic diagram is as Figures 8A - 8C shown.

[0061] (6) After heating the fifth blank to 1190 °C and holding for 14 hours, first, the upper flat and lower V-shaped anvil is used to roll the cylindrical section 14 to a diameter of 3050 mm. Then, the tapered section 15 of the fifth blank is placed in the upsetting die 16, and the upper pressure ring 20 presses the groove 5. The flat anvil 18 is used to rotate and roll the periphery of the boss 4 to the thickness L1 of the large flange 3. After the rolling is completed, the pressure ring 20 is sleeved on the boss 4, and the press presses down the pressure ring 20 to press out the groove 5 around the boss 4, forming the sixth blank. The schematic diagram is as Figures 9A - 9B shown.

[0062] (7) After heating the sixth blank to 1120 °C and holding for 18 hours, it is taken out of the furnace and the upper flat and lower V-shaped anvil is used to stretch the tapered section 15, and finally the small flange 1, the rod part 2 and the lifting lug 6 are formed.

[0063] Example 2

[0064] In this example, a 210t double-vacuum ingot is used as the forging raw material, and the material is 25Cr2Ni3MoV. After forging and forming, the diameter D of the large flange 3 of the rotor shaft head forging is 3100 mm, the length L1 is 1200 mm, the diameter of the small flange 1 is D1 = 1600 mm, and the weight of the rotor shaft head forging is 115 tons. The forging method is as follows:

[0065] (1) After the hot delivery of the ingot, it is heated to 1270 °C according to the special heating process and held for 25 hours, and then the forging tong handle section 10 and the ingot body section 11 are forged, and the nozzle section 9 at the end of the ingot body section 11 is cut off. The cutting ratio of the nozzle section 9 is 7.5%, forming the initial blank. The schematic diagram is as Figure 2 shown.

[0066] (2) The billet is heated to 1270 °C and held for 36 hours, then upsetting is carried out on the ingot body section 11 using the upper flat upsetting plate 13 and the lower upsetting die 12 on a 160 MN press. The upsetting ratio is 1.9. Drawing is carried out using the WHF method with an initial anvil width ratio of 0.63 for 12 passes, and the drawing ratio is 2.8. The heating regime for the second upsetting and drawing is the same as the first time. After upsetting, it is drawn to the 10th pass, and the drawing ratio is 2.6. After drawing using the WHF method, it is pressed into an octagon to form the second billet. The schematic diagram is as shown in Figure 3 shown.

[0067] (3) The second billet is heated to 1270 °C and held for 19 hours, then forged on the ingot body section 11 using the upper flat and lower V-shaped anvil on a 160 MN press to form the cylindrical section 14 and the conical section 15. The handle section 10 is cut off, and the end of the conical section 15 is flattened to form the third billet. Among them, the length of the cylindrical section 14 is H0 = 3000 mm, H1 = 1800 mm, and the minimum diameter of the conical section 15 is d1 = 1800 mm. The schematic diagram is as shown in Figure 4 shown.

[0068] (4) The third billet is heated to 1270 °C and held for 25 hours. Then, the conical section 15 is placed in the upsetting die 16, and the cylindrical section 14 is upset inside the die using the conical plate on a 160 MN press. After upsetting, the distance from the lowest point on the upper surface of the cylindrical section 14 to the lower surface of the cylindrical section 14 is H2 = 1500 mm. The schematic diagrams are as shown in Figure 5A and Figure 5B shown. Subsequently, the upper surface of the cylindrical section 14 is rotary rolled using the flat anvil 18 until the length of the cylindrical section 14 is H3 = 1400 mm. The schematic diagram is as shown in Figure 6 shown. After rolling is completed, the third billet is taken out of the die and the large flange 3 is rolled using the upper flat and lower V-shaped anvil to eliminate the bulge to form the fourth billet. The schematic diagram is as shown in Figure 7 shown.

[0069] (5) The fourth billet is heated to 1230 °C and held for 25 hours. Then, the flat upsetting plate 13 is placed on the cylindrical section 14 and upset and flattened. Then, the upper ring cutter 19 is used. The ring cutter 19 is coaxial with the cylindrical section 14. The press presses down the ring cutter 19 to carry out radial material distribution on the cylindrical section 14 to form a boss 4 on the upper surface of the cylindrical section 14. Finally, the area around the boss 4 is rotary rolled using the flat anvil 18 to form the fifth billet. The schematic diagram is as shown in Figures 8A - 8C shown.

[0070] (6) After heating the fifth blank to 1230 °C and holding for 14 hours, first use an upper flat and lower V-shaped anvil to roll the cylindrical section 14 to a diameter of 3100 mm. Then, place the conical section 15 of the fifth blank into the upsetting die 16, and use the upper pressure ring 20 to press the groove 5. Use a flat anvil 18 to perform rotary spreading on the periphery of the boss 4 until the thickness of the large flange 3 reaches 1200. After spreading, put the pressure ring 20 on the boss 4, and the press presses down the pressure ring 20 to press out the groove 5 around the boss 4 to form the sixth blank. The schematic diagram is as shown in Figures 9A - 9B shown.

[0071] (7) After heating the sixth blank to 1160 °C and holding for 18 hours, take it out of the furnace and use an upper flat and lower V-shaped anvil to stretch the conical section 15, and finally form the small flange 1, the rod part 2 and the lifting lug 6.

[0072] For the forgings of Example 1 and Example 2, after the above forging process, special heat treatment, and rough machining, ultrasonic flaw detection is carried out according to the technical requirements of the forgings to inspect the internal quality. No excessive defects are found in each area after detection. After the forgings are quenched and tempered, UT and room temperature performance tests are carried out. Some of the results are shown in Table 1 below:

[0073] Table 1 Test product detection data

[0074]

[0075] It can be analyzed from Table 1 that the forgings prepared in Example 1 and Example 2 have good mechanical properties, the grain size reaches grade 6.5, and the ultrasonic flaw detection of each part of the forgings is qualified, which fully shows that the process preparation method and measures are effective.

[0076] The embodiments of this specific implementation manner are all preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A forging method for a forging of a low-pressure welded rotor shaft head of a steam turbine, characterized in that, The method includes the following steps: S1: Forging an initial blank from an ingot. The initial blank includes a tong handle section (10) and an ingot body section (11), and the tong handle section (10) and the ingot body section (11) are coaxial. The ingot body section is obtained by cutting a certain proportion of the nozzle section (9) from the ingot body of the steel ingot. S2: Upsetting and drawing out. Heat the initial blank to a first temperature, and take it out of the furnace after the core of the initial blank reaches the temperature. Place the tong handle section (10) into the upsetting leak pan (12), and place a flat upsetting plate (13) on the upper part of the ingot body section (11). Press the flat upsetting plate (13) by a press to upset the ingot body section (11). After upsetting is completed, take the initial blank out of the upsetting leak pan (12), and draw out the ingot body section (11) to form a second blank. S3: Heat the second blank to the first temperature, and take it out of the furnace after the core of the second blank reaches the temperature. Forge the ingot body section (11) of the second blank into a cylindrical section (14) and a conical section (15), cut off the tong handle section (10), and flatten the end of the conical section (15) to form a third blank. S4: Heat the third blank to the first temperature, and take it out of the furnace after the core of the third blank reaches the temperature. Place the conical section (15) into the upsetting die (16). A conical hole adapted to the conical section (15) is provided in the upsetting die (16). A forging plate (17) is arranged above the cylindrical section (14). Press the forging plate (17) by a press to upset the cylindrical section (14). After completion, take the third blank out of the upsetting die (16), and then perform rotary forging on the cylindrical section (14) to eliminate the side bulging of the cylindrical section (14) to form a fourth blank. S5: Heat the fourth blank to a second temperature, which is lower than the first temperature, and take it out of the furnace after the core of the fourth blank reaches the temperature. Place the conical section (15) into the upsetting die (16). Place the flat upsetting plate (13) on the cylindrical section (14) and then perform upsetting and flattening. Then, mount the ring cutter (19). The ring cutter (19) is coaxial with the cylindrical section (14). Press down the ring cutter (19) by a press to perform radial material distribution on the cylindrical section (14). Finally, use a flat anvil (18) to perform rotary spreading on the periphery of the boss (4) to form a boss (4) on the upper surface of the cylindrical section (14) to form a fifth blank. S6: Heat the fifth blank to the second temperature, and take it out of the furnace after the core of the fifth blank reaches the temperature. Roll the cylindrical section (14) until the diameter dimension D of the large flange (3) of the forging is reached. After rolling, place the conical section (15) into the upsetting die (16). Use a flat anvil (18) to perform rotary spreading on the periphery of the boss (4) until the length L1 of the large flange (3) is reached. After spreading, put a retaining ring (20) on the boss (4), and press down the retaining ring (20) by a press to press out the groove (5) around the boss (4) to form a sixth blank. S7: Heat the sixth blank to a third temperature, which is lower than the second temperature, and take it out of the furnace after the core of the conical section (15) of the sixth blank reaches the temperature. Use an upper flat and lower V-shaped anvil to draw out the conical section (15), and finally form the small flange (1), the rod part (2), and the lifting chuck (6).

2. The forging method of a low-pressure welded rotor shaft head forging of a steam turbine according to claim 1, characterized in that: In step S1, the handle segment is forged from the ingot riser, and the cut-off ratio of the nozzle section of the ingot body is not less than 7% of the ingot weight; in step S2, the upsetting ratio of the ingot body (11) is 1.8 - 2.

2.

3. The forging method of a forged shaft head of a low-pressure welded rotor of a steam turbine according to claim 2, characterized in that: In step S2, the WHF method is adopted for drawing out the ingot body (11). When using the WHF method for drawing out, the initial anvil width ratio is required to be 0.6 - 0.8, and it is drawn out according to the pressing program for 10 - 12 passes, and the drawing out ratio is 2.5 - 3.

4. The forging method of a low-pressure welded rotor shaft head forging of a steam turbine as described in claim 1, characterized in that: In step S3, the taper of the conical section (15) is 3 - 5°.

5. The forging method of a low-pressure welded rotor shaft head forging of a steam turbine as claimed in claim 1, characterized in that: In step S3, the length of the cylindrical section (14) is H0, the length of the conical section (15) is H1, and the minimum diameter of the conical section (15) is d1, where H0 = (2.5 - 3.5)L1, d1 = (1.2 - 1.5)D1, L1 is the length of the large flange (3), and D1 is the diameter of the small flange (1).

6. The forging method of a low-pressure welded rotor shaft head forging of a steam turbine according to claim 5, characterized in that: In step S4, the forging plate (17) is a conical plate. The conical part of the conical plate faces the cylindrical section (14) and is coaxial with the cylindrical section (14). The press presses down the conical plate to upset the cylindrical section (14); after upsetting the cylindrical section (14), a flat anvil (18) is used to perform rotary rolling on the upper surface of the cylindrical section (14).

7. The forging method of a low-pressure welded rotor shaft head forging of a steam turbine according to claim 6, characterized in that: In step S4, after forging with the conical plate, the straight-line distance from the lowest point of the upper surface of the cylindrical section (14) to the lower surface of the cylindrical section (14) is H2. After performing rotary rolling on the upper surface of the cylindrical section (14) with the flat anvil (18), the straight-line distance from the upper surface of the cylindrical section (14) to the lower surface of the cylindrical section (14) is H3. Among them, H0 / H2 = (1.7 - 2.2), H2 = H3 + (100 mm - 200 mm), and L1 / H3 = (0.7 - 0.9), where L1 is the length of the large flange (3).

8. The forging method of a low-pressure welded rotor shaft head forging of a steam turbine according to claim 1, characterized in that: The value range of the first temperature is 1230 - 1270 °C, the value range of the second temperature is 1160 - 1230 °C, and the value range of the third temperature is 1120 - 1160 °C. Among them, the heating temperature in step S2 takes the upper-middle limit of the first temperature.

9. The forging method of a low-pressure welded rotor shaft head forging of a steam turbine according to claim 1, characterized in that: After step S2, step S2 is repeated to upset and draw out the initial blank, and it is repeated at least 2 times.

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