An ultra-high-temperature high-strength steam turbine rotor forging and a preparation process thereof

Abstract

The present application relates to the technical field of steam turbine rotor manufacturing, and particularly relates to a super-high-temperature high-strength steam turbine rotor forge piece and a preparation process. The steam turbine rotor forge piece has a component content of 0.08-0.15% C, ≤1.0% Si, 0.6-1.0% Mn, 9.0-12.0% Cr, 4-6% Ni, 2.0-4.0% Mo, 0.15-0.25% Nb, 1.5-2.5% Co, 2-5% W, 0.05-0.25% Ti, 1.3-2.5% V, ≤0.25% Cu, ≤0.004% P, ≤0.0008% S, ≤0.020% Al, ≤0.8PPm 〔H〕, ≤10PPm 〔O〕, ≤150PPm 〔N〕, and the rest is Fe and inevitable impurities. The present application improves the performance of the steam turbine rotor forge piece, and thus is more suitable for the use requirement of high-temperature and high-pressure resistance.

Description

Technical Field

[0001] This invention relates to the field of steam turbine rotor manufacturing technology, specifically to an ultra-high temperature, high-strength steam turbine rotor forging and its preparation process. Background Technology

[0002] With increasingly severe energy and environmental pressures, the country is placing higher demands on the thermal power generation industry, pursuing higher parameters, secondary reheat, and cleaner, more efficient operation. Currently, the highest operating temperature of the ultra-supercritical rotors used in steam turbines is 630℃. Future development will focus on achieving higher steam temperatures and pressure parameters in stages to improve the thermal efficiency of high-temperature steam. However, these higher design operating temperatures pose unprecedented challenges to materials, and no reliable materials are currently available. Therefore, developing new high-temperature resistant rotor materials is urgently needed to address this domestic gap. Summary of the Invention

[0003] To address the aforementioned problems, this invention proposes an ultra-high temperature, high-strength steam turbine rotor forging and its manufacturing process, aiming to improve the performance of the steam turbine rotor forging and thus better meet its high-temperature and high-pressure application requirements. The specific technical solution is as follows: A high-temperature, high-strength steam turbine rotor forging, wherein the forging composition by mass ratio is 0.08-0.15% C, ≤1.0% Si, 0.6-1.0% Mn, 9.0-12.0% Cr, 4-6% Ni, 2.0-4.0% Mo, 0.15-0.25% Nb, 1.5-2.5% Co, 2-5% W, 0.05-0.25% Ti, 1.3-2.5% V, ≤0.25% Cu, ≤0.004% P, ≤0.0008% S, ≤0.020% Al, ≤0.8 ppm H, ≤10 ppm O, ≤150 ppm N, with the remainder being Fe and unavoidable impurities.

[0004] The aforementioned ultra-high temperature, high-strength turbine rotor forging material is primarily strengthened by adding W, Mo, and Co to the material composition. W and Mo are solid solution strengthening elements, and their combined effect is even better, resulting in extremely high hot strength and red hardness, as well as increased tempering stability. Co and V further strengthen the material, and Co can inhibit the formation and precipitation of δ-ferrite. The addition of trace amounts of Nb, Ti, and V can refine the grain size. This results in a microstructure consisting of uniform lath tempered martensite and fine, dispersed alloy precipitates, thereby improving the performance of the ultra-high temperature, high-strength turbine rotor forging and making it more suitable for its high-temperature and high-pressure applications.

[0005] A manufacturing process for an ultra-high temperature, high-strength steam turbine rotor forging includes the following steps: (1) Electric arc furnace for rough steelmaking: After the steel is batched, it is roughed in an electric arc furnace; (2) Ladle refining: A ladle refining furnace is used to refin the molten steel after roughing in the electric arc furnace into the ladle refining furnace. (3) Vacuum degassing treatment: The ladle is hoisted into a vacuum furnace to perform vacuum degassing treatment on the molten steel; (4) Casting of consumable electrode: After the molten steel is degassed under vacuum, it is poured into the consumable electrode mold at the consumable electrode casting station by a ladle. After cooling and demolding, the consumable electrode is obtained. The consumable electrode mold is a water-cooled electrode mold under Ar gas protection to improve the cooling rate and reduce the agglomeration and growth of carbides and inclusions. Note that riser feeding control should be carried out during casting to avoid riser shrinkage. (5) Annealing of consumable electrode; The consumable electrode is annealed; The electrode surface is cleaned after annealing. (6) Preparation of turbine rotor steel ingot by electroslag remelting: Using an electroslag remelting furnace and a specially designed turbine rotor steel ingot crystallizer, the consumable electrode is inserted into the turbine rotor steel ingot crystallizer of the Ar gas-protected electroslag remelting furnace for secondary refining. After cooling in the turbine rotor steel ingot crystallizer, the turbine rotor steel ingot is obtained after demolding. (7) Annealing of turbine rotor steel ingots: The turbine rotor steel ingots are annealed; the surface of the turbine rotor steel ingots is cleaned after annealing. (8) Forging: The turbine rotor steel ingot is heated and then forged; (9) Post-forging heat treatment: The forged turbine rotor steel ingot is subjected to normalizing + spheroidizing + tempering treatment; (10) Rough machining: The turbine rotor steel ingot after forging and heat treatment is rough machined; (11) Final heat treatment: The turbine rotor steel ingot after rough machining is subjected to solution treatment and two tempering treatments to obtain ultra-high temperature and high strength turbine rotor forgings.

[0006] Preferably, in the forging process of step (8), the initial forging temperature is 1120-1200℃ and the final forging temperature is 900-950℃.

[0007] Preferably, in the final heat treatment of (11), the solution treatment involves placing the turbine rotor steel ingot in a heating furnace, heating it to 1050-1100°C at room temperature, holding it at that temperature, and then cooling it with water mist; the first tempering involves placing the turbine rotor steel ingot in a heating furnace, heating it to 720-820°C at room temperature, holding it at that temperature, and then air cooling it; the second tempering involves placing the turbine rotor steel ingot in a heating furnace, heating it to 710-810°C at room temperature, holding it at that temperature, and then air cooling it.

[0008] After normal tempering, the forgings are obtained as uniform lath tempered martensite with fine dispersed alloy precipitates. The dispersed alloy precipitates are second-phase reinforcing particles that play a role in dispersion strengthening. At high temperatures, they pin dislocations and hinder dislocation movement, thereby significantly improving the high-temperature strength and toughness of the turbine rotor forgings.

[0009] In this invention, the turbine rotor steel ingot crystallizer includes a water-cooled chassis and an annular crystallizer disposed on the water-cooled chassis. The water-cooled chassis has a water-cooled chamber inside, and the annular crystallizer has an annular water-cooled cavity. The water-cooled chamber and the annular water-cooled cavity are respectively provided with a water inlet and a water outlet. A water inlet pipe is connected to the water inlet, and a water outlet pipe is connected to the water outlet.

[0010] As a further improvement of the present invention, the turbine rotor steel ingot crystallizer is provided with a dynamic peak-shaving device for internal water temperature. The dynamic peak-shaving device for internal water temperature includes an annular water receiving groove connected to the lower part of the outer wall of the annular crystallizer, a drain outlet provided on the annular water receiving groove, a drain pipe connected to the drain outlet, and a plurality of bimetallic strip high-temperature steam traps provided on the outer circular surface of the annular crystallizer and arranged at intervals, which are connected to the annular water cooling cavity of the annular crystallizer. When the temperature of a local node area in the annular water cooling cavity of the annular crystallizer exceeds a preset threshold, the bimetallic strip high-temperature steam trap located at the local node area automatically opens, overflowing the overheated water in the local node area into the annular water receiving groove and discharged through the drain pipe, thereby achieving uniform temperature setting in each area of ​​the annular water cooling cavity of the annular crystallizer.

[0011] The opening degree of the bimetallic strip high-temperature steam trap is automatically adjusted according to the water temperature it comes into contact with. In case of overheating, the higher the water temperature, the larger the opening degree of the bimetallic strip high-temperature steam trap, and the greater the overflow of overheated water.

[0012] Preferably, a variable frequency chilled water pump is connected to the inlet of the annular water-cooled cavity of the annular crystallizer via the inlet pipe, and a pressure sensor is installed inside the annular water-cooled cavity of the annular crystallizer; the variable frequency chilled water pump and the pressure sensor are respectively connected to a controller, and the controller dynamically adjusts the speed of the variable frequency chilled water pump in real time according to the internal water pressure of the annular water-cooled cavity detected by the pressure sensor, thereby maintaining a constant internal water pressure of the annular water-cooled cavity.

[0013] When the temperature in a localized node area within the annular water-cooling chamber of the annular crystallizer becomes excessively high, hot water overflows from the bimetallic strip high-temperature steam trap, causing a drop in water pressure within the annular water-cooling chamber. At this point, the variable frequency chilled water pump increases its speed and flow rate to compensate for the pressure loss caused by the overflow of hot water from the bimetallic strip high-temperature steam trap, thus maintaining the dynamic balance of water pressure within the annular water-cooling chamber. When the temperature in the localized node area within the annular water-cooling chamber returns to normal, the bimetallic strip high-temperature steam trap at that location automatically closes, causing the water pressure within the annular water-cooling chamber to rise. At this point, the variable frequency chilled water pump reduces its speed and flow rate to restore the water pressure within the annular water-cooling chamber to normal, thus maintaining the dynamic balance of water pressure within the annular water-cooling chamber.

[0014] During electroslag remelting, a high-temperature region typically forms inside the crystallizer near the slag and molten pool. As the slag level inside the turbine rotor ingot crystallizer gradually rises, this high-temperature region also shifts upwards. This invention addresses this by arranging a large number of bimetallic strip high-temperature steam traps in an intermittent array on the annular crystallizer. This ensures that the intermittently arranged bimetallic strip high-temperature steam traps always function at the dynamically changing highest temperature, achieving a dynamic temperature peak reduction effect inside the crystallizer. This improves the uniformity of the cooling water temperature inside the crystallizer, thereby enhancing the quality of the turbine rotor ingot.

[0015] In this invention, a dummy electrode disk is provided on the electroslag remelting furnace above the turbine rotor ingot crystallizer, and the consumable electrode is connected to the lower end of the dummy electrode disk.

[0016] The dummy electrode disk is mounted on a lifting mechanism located above the turbine rotor ingot crystallizer in the electroslag remelting furnace to meet the lifting requirements of the consumable electrode during electroslag remelting.

[0017] As a further improvement of the present invention, an electroslag remelting Ar gas protection device is provided on the upper part of the turbine rotor steel ingot crystallizer. The electroslag remelting Ar gas protection device includes a protective cover provided on the upper end of the turbine rotor steel ingot crystallizer, a through hole provided at the upper center of the protective cover for passing through a consumable electrode, and an annular protective gas supply chamber provided on the protective cover in a circumferential direction. The annular protective gas supply chamber is connected to an Ar gas supply source through a pipeline. A number of gas supply pipes extending to the upper part of the turbine rotor steel ingot crystallizer are provided on the annular protective gas supply chamber in a circumferential direction. The front end of the gas supply pipe is vertically connected to a blowing pipe that communicates with the gas supply pipe.

[0018] Preferably, the air blowing pipe is a slag powder pipe formed by pressing electroslag remelting slag powder material through a special pipe forming mold.

[0019] Preferably, the special mold for forming the tube body includes an upper mold and a lower mold that fit together, a guide post disposed between the upper mold and the lower mold, a feeding port disposed at the upper end of the upper mold, a feeding cap disposed on the feeding port of the upper mold, and a conical mandrel with a demolding slope disposed between the upper mold and the lower mold. The upper mold and the lower mold fit together to form a mold cavity, and the conical mandrel passes through the mold cavity formed by the upper mold and the lower mold.

[0020] Preferably, a connecting screw is also provided between the upper mold and the lower mold.

[0021] Preferably, the tapered mandrel is provided with positioning cylinders at both ends, and positioning semicircular holes are provided at both ends of the cavities of the upper and lower molds respectively. After the upper and lower molds are aligned, the semicircular holes on the upper and lower molds are aligned to form a complete circular hole, and the positioning cylinders are positioned on the complete circular hole.

[0022] Preferably, the upper mold and the lower mold are provided with demolding holes at their left and right ends, and the demolding holes are arranged in the vertical direction and extend to the positioning cylinder.

[0023] During demolding, an ejector pin can be placed in the demolding hole. The ejector pin applies force to the positioning cylinder to push out the conical mandrel along with the air blowing pipe on it. Then, the draft angle of the conical mandrel is used to separate the air blowing pipe from the conical mandrel.

[0024] In use, a special mold for tube forming is installed on a powder metallurgy forming press. The pre-mixed and evenly blended electroslag remelting slag powder is added to the mold cavity and pressed. Under high pressure, the slag powder bonds together, and after demolding, a slag powder tube is formed. The pressed slag powder tube is used directly as a blowing pipe without sintering and is connected to a gas delivery pipe via a special connector.

[0025] During electroslag remelting, multiple circumferentially distributed air blowing pipes simultaneously blow Ar gas into the turbine rotor steel ingot crystallizer from top to bottom. The Ar gas forms a protective atmosphere above the slag liquid inside the crystallizer. As the electroslag remelting progresses, the slag liquid inside the crystallizer gradually rises. The lower part of the slag powder pipe, near the slag liquid, gradually melts under high temperature. This not only provides Ar gas protection but also replenishes the slag liquid inside the crystallizer, helping to maintain the stability of the liquid slag quality and thus improving the quality of the turbine rotor steel ingot after electroslag remelting.

[0026] The beneficial effects of this invention are: First, the present invention discloses an ultra-high temperature, high-strength steam turbine rotor forging and its manufacturing process. This is achieved by adding W, Mo, and Co to the material composition for alloy strengthening. W and Mo are solid solution strengthening elements, and their combined effect is even better, resulting in extremely high hot strength and red hardness, as well as increased tempering stability. Co and V further strengthen the material, and Co can inhibit the formation and precipitation of δ-ferrite. The addition of trace amounts of Nb, Ti, and V can refine the grain size. This results in a microstructure consisting of uniform lath tempered martensite plus fine, dispersed alloy precipitates, thereby improving the performance of the ultra-high temperature, high-strength steam turbine rotor forging.

[0027] Secondly, the present invention provides an ultra-high temperature high strength steam turbine rotor forging and its preparation process. The final heat treatment after fracture involves solution treatment and two tempering treatments, resulting in uniform lath tempered martensite with fine dispersed alloy precipitates. The dispersed alloy precipitates are second-phase reinforcing particles that play a role in dispersion strengthening. At high temperatures, they pin dislocations and hinder dislocation movement, thereby significantly improving the high temperature strength and toughness of the steam turbine rotor forging.

[0028] Third, the present invention provides an ultra-high temperature, high-strength steam turbine rotor forging and its manufacturing process. The steam turbine rotor ingot is manufactured using electroslag remelting technology, which effectively removes internal inclusions, forming an ultra-clean steam turbine rotor ingot. This process also refines the internal primary carbide structure, eliminates the network structure, and improves the strength of the molten steel after cooling. This further enhances the working performance of the cold-rolled work rolls.

[0029] Fourth, the present invention provides an ultra-high temperature, high-strength steam turbine rotor forging and its manufacturing process. The steam turbine rotor ingot crystallizer is equipped with a dynamic peak-shaving device for the internal water temperature of the annular crystallizer. Bimetallic strip-type high-temperature drain valves are arranged in a spaced array on the outer cylindrical surface of the annular crystallizer. This allows for targeted dynamic temperature adjustment of dynamically changing high-temperature areas on the steam turbine rotor ingot crystallizer, thereby maintaining dynamic temperature control during electroslag remelting. This further improves the manufacturing quality of the steam turbine rotor ingot.

[0030] Fifth, the present invention relates to an ultra-high temperature and high strength steam turbine rotor forging and its manufacturing process. The electroslag remelting Ar gas protection device uses a specially manufactured slag powder tube as an Ar gas blowing pipe. While forming an Ar gas protective atmosphere, the continuously melting slag at the lower end of the slag powder tube can be replenished to the slag liquid layer inside the crystallizer in a timely manner. This is beneficial to maintaining the stability of the liquid slag quality inside the crystallizer and enhancing the continuous absorption capacity of the slag liquid inside the crystallizer for impurities, thereby further improving the quality of the steam turbine rotor steel ingot after electroslag remelting. Attached Figure Description

[0031] Figure 1This is a schematic flowchart of the manufacturing process of an ultra-high temperature high strength steam turbine rotor forging according to the present invention; Figure 2 This is a schematic diagram of the structure of the turbine rotor steel ingot crystallizer used in the preparation process of an ultra-high temperature high strength turbine rotor forging according to the present invention. Figure 3 This is a schematic diagram of the structure of a special mold for forming tubes used in the preparation process of an ultra-high temperature, high strength steam turbine rotor forging according to the present invention.

[0032] In the diagram: 1. Consumable electrode, 2. Steam turbine rotor steel ingot crystallizer, 3. Water-cooled chassis, 4. Annular crystallizer, 5. Water-cooled chamber, 6. Annular water-cooled cavity, 7. Water inlet pipe, 8. Water outlet pipe, 9. Annular water receiving trough, 10. Drain pipe, 11. Bimetallic strip high-temperature steam trap, 12. Pressure sensor, 13. Dummy electrode plate, 14. Electroslag remelting Ar gas protection device, 15. Protective cover, 16. Annular protective gas supply chamber, 17. Gas supply pipe, 18. Gas blowing pipe, 19. Special mold for tube forming, 20. Upper mold, 21. Lower mold, 22. Guide column, 23. Feed port, 24. Feeding cap, 25. Conical mandrel, 26. Positioning cylinder, 27. Demolding hole. Detailed Implementation

[0033] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1: like Figures 1 to 3 The illustration shows an embodiment of an ultra-high temperature, high-strength steam turbine rotor forging according to the present invention. The forging comprises, by mass ratio, 0.08-0.15% C, ≤1.0% Si, 0.6-1.0% Mn, 9.0-12.0% Cr, 4-6% Ni, 2.0-4.0% Mo, 0.15-0.25% Nb, 1.5-2.5% Co, 2-5% W, 0.05-0.25% Ti, 1.3-2.5% V, ≤0.25% Cu, ≤0.004% P, ≤0.0008% S, ≤0.020% Al, ≤0.8 ppm [H], ≤10 ppm [O], ≤150 ppm [N], with the remainder being Fe and unavoidable impurities.

[0035] The aforementioned ultra-high temperature, high-strength turbine rotor forging material is primarily strengthened by adding W, Mo, and Co to the material composition. W and Mo are solid solution strengthening elements, and their combined effect is even better, resulting in extremely high hot strength and red hardness, as well as increased tempering stability. Co and V further strengthen the material, and Co can inhibit the formation and precipitation of δ-ferrite. The addition of trace amounts of Nb, Ti, and V can refine the grain size. This results in a microstructure consisting of uniform lath tempered martensite and fine, dispersed alloy precipitates, thereby improving the performance of the ultra-high temperature, high-strength turbine rotor forging and making it more suitable for its high-temperature and high-pressure applications.

[0036] Example 2: A manufacturing process for an ultra-high temperature, high-strength steam turbine rotor forging according to Example 1 includes the following steps: (1) Electric arc furnace for rough steelmaking: After the steel is batched, it is roughed in an electric arc furnace; (2) Ladle refining: A ladle refining furnace is used to refin the molten steel after roughing in the electric arc furnace into the ladle refining furnace. (3) Vacuum degassing treatment: The ladle is hoisted into a vacuum furnace to perform vacuum degassing treatment on the molten steel; (4) Casting of consumable electrode: After the molten steel is degassed under vacuum, it is poured into the consumable electrode mold at the consumable electrode casting station by a ladle. After cooling and demolding, consumable electrode 1 is obtained. The consumable electrode mold is a water-cooled electrode mold under Ar gas protection to improve the cooling rate and reduce the agglomeration and growth of carbides and inclusions. Note that riser feeding control should be carried out during casting to avoid riser shrinkage. (5) Annealing of consumable electrode; The consumable electrode is annealed; The electrode surface is cleaned after annealing. (6) Preparation of turbine rotor steel ingot by electroslag remelting: Using an electroslag remelting furnace and a specially designed turbine rotor steel ingot crystallizer 2, the consumable electrode 1 is inserted into the turbine rotor steel ingot crystallizer 2 of the Ar gas-protected electroslag remelting furnace for secondary refining, and cooled in the turbine rotor steel ingot crystallizer 2. After demolding, the turbine rotor steel ingot is obtained. (7) Annealing of turbine rotor steel ingots: The turbine rotor steel ingots are annealed; the surface of the turbine rotor steel ingots is cleaned after annealing. (8) Forging: The turbine rotor steel ingot is heated and then forged; (9) Post-forging heat treatment: The forged turbine rotor steel ingot is subjected to normalizing + spheroidizing + tempering treatment; (10) Rough machining: The turbine rotor steel ingot after forging and heat treatment is rough machined; (11) Final heat treatment: The turbine rotor steel ingot after rough machining is subjected to solution treatment and two tempering treatments to obtain ultra-high temperature and high strength turbine rotor forgings.

[0037] Preferably, in the forging process of step (8), the initial forging temperature is 1120-1200℃ and the final forging temperature is 900-950℃.

[0038] Preferably, in the final heat treatment of (11), the solution treatment involves placing the turbine rotor steel ingot in a heating furnace, heating it to 1050-1100°C at room temperature, holding it at that temperature, and then cooling it with water mist; the first tempering involves placing the turbine rotor steel ingot in a heating furnace, heating it to 720-820°C at room temperature, holding it at that temperature, and then air cooling it; the second tempering involves placing the turbine rotor steel ingot in a heating furnace, heating it to 710-810°C at room temperature, holding it at that temperature, and then air cooling it.

[0039] After normal tempering, the forgings are obtained as uniform lath tempered martensite with fine dispersed alloy precipitates. The dispersed alloy precipitates are second-phase reinforcing particles that play a role in dispersion strengthening. At high temperatures, they pin dislocations and hinder dislocation movement, thereby significantly improving the high-temperature strength and toughness of the turbine rotor forgings.

[0040] In this embodiment, the turbine rotor steel ingot crystallizer 2 includes a water-cooled chassis 3 and an annular crystallizer 4 disposed on the water-cooled chassis 3. The water-cooled chassis 3 has a water-cooled chamber 5 inside, and the annular crystallizer 4 is provided with an annular water-cooled cavity 6. The water-cooled chamber 5 and the annular water-cooled cavity 6 are respectively provided with a water inlet and a water outlet. The water inlet is connected to a water inlet pipe 7, and the water outlet is connected to a water outlet pipe 8.

[0041] As a further improvement of this embodiment, the turbine rotor steel ingot crystallizer 2 is equipped with a dynamic peak-shaving device for internal water temperature. The dynamic peak-shaving device for internal water temperature includes an annular water receiving groove 9 connected to the lower part of the outer wall of the annular crystallizer 4, a drain outlet provided on the annular water receiving groove 9, a drain pipe 10 connected to the drain outlet, and a plurality of bimetallic strip high-temperature steam traps 11 provided on the outer circular surface of the annular crystallizer 4 and arranged at intervals, which are connected to the annular water cooling cavity 6 of the annular crystallizer 4. When the temperature of a local node area in the annular water cooling cavity 6 of the annular crystallizer 4 exceeds a preset threshold, the bimetallic strip high-temperature steam trap 11 located at the local node area automatically opens, overflowing the overheated water located at the local node area into the annular water receiving groove 9 and discharged through the drain pipe 10, thereby achieving uniform temperature setting in each area of ​​the annular water cooling cavity 6 of the annular crystallizer 4.

[0042] The opening degree of the bimetallic strip high-temperature steam trap 11 is automatically adjusted according to the water temperature it comes into contact with. In case of overheating, the higher the water temperature, the larger the opening degree of the bimetallic strip high-temperature steam trap 11, and the greater the overflow of overheated water.

[0043] Preferably, a variable frequency chilled water pump (not shown in the figure) is connected to the inlet of the annular water-cooled cavity 6 of the annular crystallizer 4 via the inlet pipe. A pressure sensor 12 is installed inside the annular water-cooled cavity 6 of the annular crystallizer 4. The variable frequency chilled water pump and the pressure sensor 12 are respectively connected to a controller. The controller dynamically adjusts the speed of the variable frequency chilled water pump in real time according to the internal water pressure of the annular water-cooled cavity 6 detected by the pressure sensor 12, thereby maintaining a constant internal water pressure in the annular water-cooled cavity.

[0044] Preferably, the internal water pressure of the annular water-cooled cavity 6 is set to 1.1 to 1.5 atmospheres.

[0045] When the temperature in a localized node area within the annular water-cooling chamber 6 of the annular crystallizer 4 becomes excessively high, hot water overflows from the bimetallic strip high-temperature steam trap 11, causing a drop in water pressure within the annular water-cooling chamber 6. At this point, the variable frequency chilled water pump increases its speed and flow rate to compensate for the pressure loss caused by the overflow of hot water from the bimetallic strip high-temperature steam trap 11, thus maintaining the dynamic balance of water pressure within the annular water-cooling chamber. When the temperature in the localized node area within the annular water-cooling chamber 6 of the annular crystallizer 4 returns to normal, the bimetallic strip high-temperature steam trap at that location automatically closes, causing the water pressure within the annular water-cooling chamber 6 to rise. At this point, the variable frequency chilled water pump reduces its speed and flow rate to restore the water pressure within the annular water-cooling chamber 6 to normal, thus maintaining the dynamic balance of water pressure within the annular water-cooling chamber 6.

[0046] During electroslag remelting, a high-temperature region typically forms inside the crystallizer near the slag and molten pool. As the slag level inside the turbine rotor ingot crystallizer 2 gradually rises, this high-temperature region also moves upwards. In this embodiment, a large number of bimetallic strip high-temperature steam traps 11 are arranged in a spaced array on the annular crystallizer 4. This ensures that the spaced array of bimetallic strip high-temperature steam traps 11 always functions at the highest temperature, which is constantly changing in position. This achieves a dynamic temperature peak reduction effect inside the crystallizer, thereby improving the uniformity of the cooling water temperature inside the crystallizer and ultimately improving the quality of the turbine rotor ingot.

[0047] In this embodiment, a dummy electrode disk 13 is provided on the electroslag remelting furnace above the turbine rotor ingot crystallizer 2, and the consumable electrode 1 is connected to the lower end of the dummy electrode disk 13.

[0048] The dummy electrode disk 13 is mounted on the lifting mechanism (not shown in the figure) located above the turbine rotor ingot crystallizer 2 in the electroslag remelting furnace to meet the lifting requirements of the consumable electrode 1 during electroslag remelting.

[0049] As a further improvement of this embodiment, an electroslag remelting Ar gas protection device 14 is provided on the upper part of the turbine rotor steel ingot crystallizer 2. The electroslag remelting Ar gas protection device 14 includes a protective cover 15 provided on the upper end of the turbine rotor steel ingot crystallizer 2, a through hole provided at the upper center of the protective cover 14 for passing through the consumable electrode 1, and an annular protective gas supply chamber 16 provided on the protective cover 14 in a circumferential direction. The annular protective gas supply chamber 16 is connected to an Ar gas supply source through a pipeline. A number of gas supply pipes 17 are provided on the annular protective gas supply chamber 16 in a circumferential direction extending to the upper part of the turbine rotor steel ingot crystallizer 2. The front end of the gas supply pipe 17 is vertically connected to a blowing pipe 18 that communicates with the gas supply pipe 17.

[0050] Preferably, the air blowing pipe 18 is a slag powder pipe formed by pressing electroslag remelting slag powder material through a special pipe forming mold 19.

[0051] Preferably, the tube forming mold 19 includes an upper mold 20 and a lower mold 21 that fit together, a guide post 22 disposed between the upper mold 20 and the lower mold 21, a feeding port 23 disposed at the upper end of the upper mold 20, a feeding cap 24 disposed on the feeding port 23 of the upper mold, and a conical mandrel 25 with a demolding slope disposed between the upper mold 20 and the lower mold 21. The upper mold 20 and the lower mold 21 fit together to form a mold cavity, and the conical mandrel 25 passes through the mold cavity formed by the upper mold 20 and the lower mold 21.

[0052] Preferably, a connecting screw is also provided between the upper mold 20 and the lower mold 21.

[0053] Preferably, the tapered mandrel 25 is provided with positioning cylinders 26 at both ends, and positioning semi-circular holes are provided at both ends of the cavities of the upper mold 20 and the lower mold 21. After the upper mold 20 and the lower mold 21 are aligned, the semi-circular holes on the upper mold 20 and the lower mold 21 are aligned to form a complete circular hole, and the positioning cylinders 26 are positioned on the complete circular hole.

[0054] Preferably, the upper mold 210 and the lower mold 21 are provided with demolding holes 27 at their left and right ends, and the demolding holes 27 are arranged in the vertical direction and extend to the positioning cylinder 26.

[0055] During demolding, an ejector pin can be placed in the demolding hole 27. The ejector pin applies force to the positioning cylinder 26 to eject the conical mandrel 25 together with the air blowing pipe 18 above it. Then, the draft angle of the conical mandrel 25 is used to separate the air blowing pipe 18 from the conical mandrel 25.

[0056] In use, the special mold 19 for tube forming is installed on the powder metallurgy forming press. The electroslag remelting slag powder material, which has been batched and mixed evenly, is added to the mold cavity of the special mold 19 for pressing. The slag powder is bonded together under high pressure, and after demolding, a slag powder tube is formed. The pressed slag powder tube is used directly as a blowing pipe 18 without sintering, and is connected to the gas delivery pipe 18 through a special connector.

[0057] During electroslag remelting, multiple circumferentially distributed air blowing pipes 18 simultaneously blow Ar gas into the turbine rotor steel ingot crystallizer 2 from top to bottom, creating a protective atmosphere above the slag liquid inside the crystallizer 2. As electroslag remelting progresses, the slag liquid inside the crystallizer 2 gradually rises, and the lower part of the slag powder pipe near the slag liquid gradually melts under high temperature. This not only provides Ar gas protection but also replenishes the slag liquid inside the crystallizer, helping to maintain the stability of the liquid slag quality and thus improving the quality of the turbine rotor steel ingot after electroslag remelting.

[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A manufacturing process for ultra-high temperature, high-strength steam turbine rotor forgings, characterized in that, The ultra-high temperature high-strength steam turbine rotor forging, according to its mass ratio, comprises 0.08-0.15% C, ≤1.0% Si, 0.6-1.0% Mn, 9.0-12.0% Cr, 4-6% Ni, 2.0-4.0% Mo, 0.15-0.25% Nb, 1.5-2.5% Co, 2-5% W, 0.05-0.25% Ti, 1.3-2.5% V, ≤0.25% Cu, ≤0.004% P, ≤0.0008% S, ≤0.020% Al, ≤0.8 ppm H, ≤10 ppm O, ≤150 ppm N, with the remainder being Fe and unavoidable impurities. The preparation process of the ultra-high temperature high-strength steam turbine rotor forging includes the following steps: (1) Electric arc furnace for rough steelmaking: After the steel is batched, it is roughed in an electric arc furnace; (2) Ladle refining: A ladle refining furnace is used to refin the molten steel after roughing in the electric arc furnace into the ladle refining furnace. (3) Vacuum degassing treatment: The ladle is hoisted into a vacuum furnace to perform vacuum degassing treatment on the molten steel; (4) Casting of consumable electrode: After the molten steel is degassed under vacuum, it is poured into the consumable electrode mold at the consumable electrode casting station by a ladle. After cooling and demolding, the consumable electrode is obtained. The consumable electrode mold is a water-cooled electrode mold under Ar gas protection to improve the cooling rate and reduce the agglomeration and growth of carbides and inclusions. Note that riser feeding control should be carried out during casting to avoid riser shrinkage. (5) Annealing of consumable electrode; The consumable electrode is annealed; The electrode surface is cleaned after annealing. (6) Preparation of turbine rotor steel ingot by electroslag remelting: Using an electroslag remelting furnace and a specially designed turbine rotor steel ingot crystallizer, the consumable electrode is inserted into the turbine rotor steel ingot crystallizer of the Ar gas-protected electroslag remelting furnace for secondary refining. After cooling in the turbine rotor steel ingot crystallizer, the turbine rotor steel ingot is obtained after demolding. (7) Annealing of turbine rotor steel ingots: The turbine rotor steel ingots are annealed; the surface of the turbine rotor steel ingots is cleaned after annealing. (8) Forging: The turbine rotor steel ingot is heated and then forged; (9) Post-forging heat treatment: The forged turbine rotor steel ingot is subjected to normalizing + spheroidizing + tempering treatment; (10) Rough machining: The turbine rotor steel ingot after forging and heat treatment is rough machined; (11) Final heat treatment: The turbine rotor steel ingot after rough machining is subjected to solution treatment and two tempering treatments to obtain ultra-high temperature and high strength turbine rotor forgings. The turbine rotor steel ingot crystallizer includes a water-cooled chassis and an annular crystallizer mounted on the water-cooled chassis. The water-cooled chassis contains a water-cooled chamber, and the annular crystallizer has an annular water-cooled cavity. The water-cooled chamber and the annular water-cooled cavity are respectively provided with an inlet and an outlet. An inlet pipe is connected to the inlet, and an outlet pipe is connected to the outlet. The turbine rotor steel ingot crystallizer is equipped with an internal dynamic water temperature reduction device, which includes an annular water receiving groove connected to the lower part of the outer wall of the annular crystallizer and a drain outlet mounted on the annular water receiving groove. A drain pipe connected to the drain outlet and a number of bimetallic strip high-temperature steam traps arranged at intervals on the outer surface of the annular crystallizer and connected to the annular water-cooling cavity of the annular crystallizer are provided. When the temperature of a local node area in the annular water-cooling cavity of the annular crystallizer exceeds a preset threshold, the bimetallic strip high-temperature steam trap located at the local node area automatically opens, allowing the overheated water located at the local node area to overflow into the annular water receiving tank and be discharged through the drain pipe, thereby achieving uniform temperature setting in each area of ​​the annular water-cooling cavity of the annular crystallizer.

2. A manufacturing process for an ultra-high temperature, high-strength steam turbine rotor forging as described in claim 1, characterized in that, In the forging process of step (8), the initial forging temperature is 1120-1200℃ and the final forging temperature is 900-950℃.

3. A manufacturing process for an ultra-high temperature, high-strength steam turbine rotor forging as described in claim 1, characterized in that, In the final heat treatment described in (11), the solution treatment involves placing the turbine rotor steel ingot in a heating furnace, heating it to 1050-1100℃ at room temperature, holding it at that temperature, and then cooling it with water mist. The first tempering involves placing the turbine rotor steel ingot in a heating furnace, heating it to 720-820℃ at room temperature, holding it at that temperature, and then air cooling it. The second tempering involves placing the turbine rotor steel ingot in a heating furnace, heating it to 710-810℃ at room temperature, holding it at that temperature, and then air cooling it.

4. A manufacturing process for an ultra-high temperature, high-strength steam turbine rotor forging as described in claim 1, characterized in that, A variable frequency chilled water pump is connected to the inlet of the annular water-cooled cavity of the annular crystallizer via the inlet pipe. A pressure sensor is installed inside the annular water-cooled cavity of the annular crystallizer. The variable frequency chilled water pump and the pressure sensor are respectively connected to a controller. The controller dynamically adjusts the speed of the variable frequency chilled water pump in real time according to the internal water pressure of the annular water-cooled cavity detected by the pressure sensor, thereby maintaining a constant internal water pressure of the annular water-cooled cavity.

5. A manufacturing process for an ultra-high temperature, high-strength steam turbine rotor forging as described in claim 1, characterized in that, An electroslag remelting Ar gas protection device is provided on the upper part of the turbine rotor steel ingot crystallizer. The electroslag remelting Ar gas protection device includes a protective cover at the upper end of the turbine rotor steel ingot crystallizer, a through hole at the upper center of the protective cover for passing through a consumable electrode, and an annular protective gas supply chamber arranged circumferentially on the protective cover. The annular protective gas supply chamber is connected to an external Ar gas supply source through a pipeline. A number of gas supply pipes extending circumferentially to the upper part of the turbine rotor steel ingot crystallizer are arranged on the annular protective gas supply chamber. The front end of the gas supply pipe is vertically connected to a blowing pipe that communicates with the gas supply pipe.

6. A manufacturing process for an ultra-high temperature, high-strength steam turbine rotor forging as described in claim 5, characterized in that, The air blowing pipe is a slag powder pipe formed by pressing electroslag remelting slag powder material through a special mold for pipe forming.

7. A manufacturing process for an ultra-high temperature, high-strength steam turbine rotor forging as described in claim 6, characterized in that, The special mold for forming the tube body includes an upper mold and a lower mold that fit together, a guide post disposed between the upper mold and the lower mold, a feeding port disposed at the upper end of the upper mold, a feeding cap disposed on the feeding port of the upper mold, and a conical mandrel with a demolding slope disposed between the upper mold and the lower mold. The upper mold and the lower mold fit together to form a mold cavity, and the conical mandrel passes through the mold cavity formed by the upper mold and the lower mold.

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