Forging method of integrated magnet yoke ring

Abstract

The invention discloses a forging method of an integrated magnet yoke ring, which belongs to the technical field of hydroelectric power generation and comprises the following steps: preparing a hollow steel ingot, and expanding the aperture of an inner ring hole in the hollow steel ingot by using a hole expanding device to obtain an annular steel billet; the forming die is placed in spinning equipment, the annular steel blank is placed in a forging cavity, the lower end face of the annular steel blank abuts against the protruding face between the magnetic conductive block forming dies, the circumferential face of the annular steel blank abuts against the inner surface of the protruding forming die, the annular steel blank is spun through the spinning equipment, and in the spinning process, the annular steel blank is subjected to extrusion forming. The circumferential surface of the annular steel blank is extruded by the bulge forming die and extends outwards to form a plurality of bulges; the part, corresponding to the magnetic conductive block forming die, of the lower end surface of the annular steel blank is pressed and extends downwards to form a plurality of magnetic conductive blocks; and demolding and finishing to obtain a finished magnet yoke ring. The technical problems of long manufacturing period and high manufacturing cost of the high-rotating-speed and high-capacity pumping and storage magnet yoke are solved, and the high-rotating-speed and high-capacity pumping and storage magnet yoke has the advantages of being low in machining amount and high in safety and reliability.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydroelectric power generation, and particularly relates to a forging method of an integrated yoke ring. Background Art

[0002] At present, for a generator-motor with a rated power of 300 MW or above and a rated speed of 428.6 rpm or above, its yoke structure is constructed by stacking yoke rings layer by layer. As shown in Figure 5 、 Figure 8 , the yoke ring includes a ring steel 1. For the ventilation requirements of the unit and the requirements of steel strength, a plurality of protruding magnetic conduction blocks 2 are evenly distributed circumferentially on the upper end surface of the ring steel 1. The adjacent magnetic conduction blocks 2 are spaced by ventilation grooves 3. The magnetic conduction block 2 is integrally in a trapezoidal structure. A groove 20 for limiting the stacking of the yoke ring is provided in the trapezoidal structure, and an extended boss 21 is provided at the end of the trapezoidal structure. At the same time, a plurality of protruding parts 5 with a trapezoidal axial cross-section are also evenly distributed on the outer circumferential surface of the ring steel 1. The protruding parts 5 are located below the extended boss 21, and the outer end surfaces of the protruding parts 5 and the extended boss 21 are in the same plane. The extended boss 21 and the protruding parts 5 together form a forming area of the T-tail groove 4.

[0003] Focusing on the connection structure between the two key components of the ring steel and the magnetic conduction block, in the prior art practice, the following three representative types are mainly formed: The first connection structure, as shown in Figure 12 、 Figure 13 , wherein the ring steel 1 is processed from a high-strength forging by free forging, and the magnetic conduction block 2 is processed from a high-strength annular thick steel plate, and then the two are connected by welding.

[0004] The second connection structure, as shown in Figure 12 、 Figure 14 , both the ring steel 1 and the magnetic conduction block 2 are processed from high-strength annular thick steel plates, and then the two are connected by welding.

[0005] The third connection structure, as shown in Figures 15 - 18 , the ring steel 1 is free forged, and by increasing the axial forging height of the ring steel, the magnetic conduction block 2 and the ring steel 1 are forged into one body, and the magnetic conduction block 2 is formed by subsequent processing on the ring steel 1.

[0006] However, the above three technical solutions of the connection structure still have the following deficiencies in practical applications: 1) If the ring steel and the magnetic conduction block are connected by welding, in order to ensure the welding reliability of the magnetic conduction block, the carbon equivalent of the ring steel needs to be controlled below 0.65, resulting in great difficulty in controlling the material composition. Correspondingly, the manufacturing process becomes strict, leading to an increase in the material manufacturing cost.

[0007] 2) If the annular steel and the magnetic conduction blocks are connected by welding, the magnetic conduction blocks are severely deformed after welding. A large amount of machining allowance needs to be reserved before welding, and the post-welding finish machining takes a long time and results in high material loss.

[0008] 3) If the annular steel and the magnetic conduction blocks are connected by welding, the large number of magnetic conduction blocks around the circumference leads to a large amount of welding, and the manufacturing cycle of the annular steel is significantly prolonged.

[0009] 4) The outer edge of the finished product of the forged annular steel is circular, while the actual requirement of the yoke ring is a polygonal outer edge, which needs to be achieved through cutting processing, resulting in material waste.

[0010] 5) If the annular steel and the magnetic conduction blocks are forged into an integral body by free forging, it is necessary to completely rely on machining to form the magnetic conduction blocks, and the processing amount is huge and the cost is high.

[0011] 6) If a high-strength annular thick steel plate is used as the yoke ring, due to the high flatness of the steel plate itself, the deformation after welding is more serious. To ensure good contact between the rings after stacking, a large amount of processing needs to be carried out on the annular thick steel plate, which takes a long time and has a high manufacturing cost.

[0012] The above problems indicate that the existing technologies represented by the above three connection structures generally have core defects such as serious material waste, long manufacturing cycle, and high manufacturing cost. Therefore, it is urgent to explore an innovative forging method for the yoke ring structure to solve the above problems. Summary of the Invention

[0013] The purpose of the present invention is to solve the above problems existing in the prior art, and provides a forging method for an integral yoke ring. The method is realized based on a die and die forging technology. The annular steel blank is subjected to die forging and spinning technology, so that the magnetic conduction blocks and the convex parts are integrally formed on the annular steel blank, and then the finished yoke ring is obtained through demoulding and finishing processing, effectively solving the technical problems of high manufacturing cost and long manufacturing cycle of the high-speed large-capacity pumped storage yoke.

[0014] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A forging method for an integral yoke ring, which is realized based on a die and die forging technology. The die includes an inner ring body, an outer ring body and a bottom die. The bottom die is fixed between the lower ends of the inner ring body and the outer ring body. The inner ring body, the outer ring body and the bottom die cooperate to form a forging cavity. The bottom die is evenly provided with a plurality of downwardly concave magnetic conduction block forming dies, and a convex surface is formed between adjacent magnetic conduction block forming dies; the inner surface of the outer ring body is evenly provided with a plurality of convex forming dies, and each convex forming die is respectively located between the magnetic conduction block forming dies; the forging method includes the following steps: a. Prepare a hollow steel ingot, and use a hole expanding device to expand the aperture of the inner ring hole on the hollow steel ingot to obtain an annular steel blank; b. Place the matrix die in the spinning equipment, put the annular steel blank into the forging cavity, make the lower end face of the annular steel blank abut against the convex surface between the magnetic conduction block forming dies, make the circumferential surface of the annular steel blank abut against the inner surface of the convex forming die, and make the upper end face of the annular steel blank expose between the upper end face of the inner ring body and the upper end face of the outer ring body. Use the spinning equipment to spin the annular steel blank. During the spinning process, the circumferential surface of the annular steel blank is extruded by the convex forming die and extends outward until a plurality of protruding parts are formed on the circumferential surface of the annular steel blank. The part of the lower end face of the annular steel blank corresponding to the magnetic conduction block forming die is pressed and extends downward until a plurality of magnetic conduction blocks are formed on the lower end face of the annular steel blank. c. Demold and finish the annular steel blank with protruding parts and magnetic conduction blocks to obtain the finished magnetic yoke ring.

[0015] Preferably, in the step a, the preparation method of the hollow steel ingot includes the following steps: a1. Prepare a cylindrical blank Perform pressing the tongs, chamfering, removing the nozzle, removing the riser, primary upsetting, drawing out to a square, rounding, and blanking on the steel ingot in sequence to obtain a cylindrical blank; a2. Prepare a hollow steel ingot Perform secondary upsetting, spinning from the outer circumference to the center, rolling, and punching along the axis on the cylindrical blank in sequence to obtain a hollow steel ingot.

[0016] Preferably, the upsetting ratio of the primary upsetting is 2.0 - 2.5, and the upsetting ratio of the secondary upsetting is 2.5 - 3.0.

[0017] Preferably, in the step a, when using a hole expanding equipment to expand the aperture of the inner ring hole on the hollow steel ingot, control the height of the obtained annular steel blank to be 1.1 - 1.2 times the height of the finished magnetic yoke ring.

[0018] Preferably, the spinning in the step b and the step a2 adopts the narrow anvil spinning technology, and the anvil width of the narrow anvil is less than 900 mm.

[0019] Preferably, in the step a1, when drawing out the steel ingot to a square, the wide anvil large reduction method is adopted, and the anvil width of the wide anvil is greater than 1100 mm.

[0020] Preferably, in the step a1, the raw materials selected for the steel ingot include nickel pig iron and return materials, and the proportion of nickel pig iron is ≥ 30 wt%.

[0021] Preferably, in the step a, before preparing the cylindrical blank from the steel ingot, heat the steel ingot to 1100 - 1150 °C and keep it warm for 10 - 11 h.

[0022] The advantages of adopting the present invention are as follows: 1. In the present invention, first, by applying the die forging and spin forging techniques to the ring-shaped steel blank, the magnetic conduction blocks and the protruding parts are integrally formed on the ring-shaped steel blank, and then, after demolding and finishing, the finished magnetic yoke ring is obtained. This fully ensures the fullness, density of the angular parts of the magnetic yoke ring and the performance requirements of the entire magnetic yoke, completely eliminates the welding process, and avoids problems such as strict control of the carbon equivalent of the material due to welding (≤0.65), large welding deformation requiring reserved machining allowance, time-consuming post-welding finishing machining, and welding quality risks. It directly reduces the difficulty of material composition control and manufacturing cost, and significantly shortens the processing cycle.

[0023] Secondly, by applying the die forging and spin forging to the ring-shaped steel blank, the magnetic conduction blocks and the protruding parts are integrally formed on the ring-shaped steel blank, replacing the traditional process of machining the trapezoidal protruding parts on the outer edge by cutting. This significantly reduces the cutting amount, avoids the welding quality risk, and further improves the reliability and safety of the magnetic yoke operation. Moreover, compared with the traditional step-by-step processing technology of magnetic conduction blocks and rings, the process of welding magnetic conduction blocks and the process of machining magnetic conduction blocks are omitted, and there is no need for secondary processing of magnetic conduction blocks after free forging or cutting of thick steel plates, which significantly reduces the material loss and processing amount.

[0024] Thirdly, by applying the die forging and spin forging to the ring-shaped steel blank, the magnetic conduction blocks are integrally formed on the ring-shaped steel. Based on this structural feature, the protruding part and the extended boss are used as the axial sampling area, thus replacing the traditional sampling method that requires additional forging of redundant materials with an inner ring width of not less than 100 mm. This optimizes the sampling area structure and significantly reduces the material redundancy. At the same time, the axial sampling area formed by the protruding part and the extended boss is exactly in the stress concentration areas such as the T-tail groove or dovetail groove of the magnetic yoke. Since axial sampling has higher requirements for the mechanical properties of the material, using this area as the sampling point for detection can more accurately reflect the actual performance of the key parts of the magnetic yoke, thus significantly improving the reliability and accuracy of the mechanical property test results.

[0025] Through mechanical property test verification, the test results of the samples cut at 90 mm from the end face of the magnetic yoke ring and at the axial center of the magnetic yoke ring are as follows: yield strength ≥ 690 MPa, tensile strength ≥ 770 MPa, elongation ≥ 16%; the 0°C impact energy test result of the sample cut at 90 mm from the end face of the magnetic yoke ring is ≥ 68 J; the 0°C impact energy test result of the sample cut at the axial center of the magnetic yoke ring is ≥ 47 J, fully meeting the mechanical property standards of high-speed generator-motors.

[0026] In summary, the forging method of the present invention, while ensuring the reliability and safety of the magnetic yoke operation, significantly reduces the material loss and processing cost, shortens the manufacturing cycle, and effectively solves the technical problems of high manufacturing cost and long cycle of high-speed large-capacity pumped storage magnetic yokes.

[0027] 2. In the present invention, a hollow steel ingot is prepared through the forging processes of primary upsetting and secondary upsetting, effectively crushing and refining the as-cast structure and forging and closing internal defects, meeting the requirements of the tissue uniformity and integrity for the subsequent formed yoke ring, ensuring the goal of the integrated forming forging process of the extra-large ring steel forging by combining die forging and spin forging, and ensuring that the finished yoke ring can meet the stringent standards for key parameters such as mechanical properties and impact energy during the operation of the large-capacity and high-speed pumped storage unit.

[0028] 3. In the present invention, the primary upsetting adopts an upsetting ratio of 2.0 - 2.5, which can effectively crush the as-cast structure, forge and close the porosity defects, promote the transformation of the steel ingot from casting to forging, and obtain a dense and uniform cylindrical blank; subsequently, the cylindrical blank is forged again, and the secondary upsetting ratio is set to 2.5 - 3.0, taking into account both crushing the as-cast structure and preventing defects caused by excessive deformation, improving the performance stability of the final finished yoke ring.

[0029] 4. In the present invention, the height of the annular steel blank is designed to be 1.1 - 1.2 times the height of the finished yoke ring. This design of the height margin reserves sufficient processing space for subsequent die-forging by spinning, ensuring that the annular steel blank can fully fill the die-forging cavity during the spinning process, thereby ensuring good filling and density at the angular parts of the finished yoke ring.

[0030] 5. In the present invention, through the spinning method with a narrow anvil and the anvil width of the narrow anvil being less than 900 mm: during the spinning forging of the cylindrical blank from the outside to the inside in step a2, it can make the material generate more precise plastic flow during the process of forming a hollow steel ingot under the action of radial pressure; in step b, the metal radial flow of the annular steel blank can be precisely controlled, enabling the magnetic conduction block and the protruding part to closely fit the die-forging cavity, achieving high-precision integrated forming, and ensuring the dimensional accuracy and density of each part of the finished yoke structure.

[0031] 6. In the present invention, when drawing out the steel ingot to a square shape, by adopting the wide anvil large reduction method, that is, the WHF main deformation method, and the anvil width of the wide anvil being greater than 1100 mm, this method and parameter range can not only effectively crush the as-cast structure, forge and close the internal porosity defects of the steel ingot, promote the transformation of the steel ingot from the as-cast structure to the forged structure, but also fully forge and close the internal defects of the steel ingot, thereby obtaining a more dense and uniform cylindrical blank.

[0032] 7. In the present invention, by controlling the selection of the steel ingot raw materials to include nickel pig iron and return materials, and limiting the proportion of nickel pig iron within the range of ≥30 wt%, the strength, toughness and high-temperature resistance of the steel are significantly improved, ensuring the anti-fatigue performance of the yoke ring under extreme mechanical loads, thereby meeting the long-term stable operation requirements of the pumped storage unit.

[0033] 8. In the present invention, before the primary forging process of the ingot, by heating the ingot to 1100 - 1150 °C and holding for 10 - 11 h, the temperature inside and outside the ingot is ensured to be uniform, so that the deformation ability of each part of the ingot is consistent in the subsequent primary forging process, avoiding defects such as uneven deformation and cracking caused by local temperature differences, and laying a foundation for obtaining a ring-shaped steel forging with uniform structure and stable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of putting the ring-shaped steel blank into the die for drop forging in the present invention; Figure 2 It is a top view of the die for drop forging in the present invention; Figure 3 It is a top view of an arc section of the ring-shaped steel forging forged by the present invention; Figure 4 It is an A - A cross-sectional view of an arc section of the ring-shaped steel forging forged by the present invention; Figure 5 It is a schematic diagram of the overall structure of the ring-shaped steel forging forged by the present invention; Figure 6 It is a top view of an arc section of the magnetic yoke ring finely processed by the present invention; Figure 7 It is an A - A cross-sectional view of an arc section of the finished magnetic yoke ring finely processed by the present invention; Figure 8 It is a schematic diagram of the overall structure of the finished magnetic yoke ring finely processed by the present invention; Figure 9 It is a schematic diagram of the sampling position of the ring-shaped steel forging in the present invention; Figure 10 It is a schematic diagram of the structure where the sampling position is at the T - shaped tail groove in the present invention; Figure 11 It is the performance test result of the ring-shaped steel forging forged in the embodiment; Figure 12 It is a top view of an arc section of the welding structure of the magnetic yoke ring in the prior art; Figure 13 It is an A - A cross-sectional view of an arc section of the welding structure of the magnetic yoke ring in the prior art (free-forged ring-shaped steel); Figure 14 It is an A - A cross-sectional view of an arc section of the welding structure of the magnetic yoke ring in the prior art (thick steel plate ring-shaped steel); Figure 15 It is a top view of the ring-shaped steel forging in the prior art (including the forging height of the magnetic conduction block); Figure 16 It is an A - A cross-sectional view of the ring-shaped steel forging in the prior art (including the forging height of the magnetic conduction block); Figure 17It is the top view of the magnetic yoke ring formed by machining magnetic conduction blocks on the annular steel forging in the prior art; Figure 18 It is the A-A sectional view of the magnetic yoke ring formed by machining magnetic conduction blocks on the annular steel forging in the prior art.

[0035] The reference numerals in the figure are: 1, annular steel; 2, magnetic conduction block; 20, groove; 21, extension boss; 3, ventilation groove; 4, T-shaped groove; 5, protruding part; 6, protruding surface; 7, magnetic conduction block forming die; 8, annular steel blank; 9, split die; 90, inner ring body; 91, outer ring body; 92, bottom die; 10, rotating table; 11, protruding forming die; 12, inner ring hole. Specific embodiments

[0036] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0037] The forging method of the integral magnetic yoke ring provided by the present invention is realized based on the split die 9 and split die forging technology, and combines spin forging to cooperate to realize the forging of the integral magnetic yoke ring. Please refer to Figure 1 and Figure 2 , which respectively show the structural diagram after the annular steel blank 8 is placed in the split die 9 and the structural diagram of the split die 9. Among them, the split die 9 includes an inner ring body 90, an outer ring body 91 and a bottom die 92. The bottom die 92 is fixed between the lower ends of the inner ring body 90 and the outer ring body 91. The inner ring body 90, the outer ring body 91 and the bottom die 92 cooperate to form a forging cavity. A plurality of downwardly concave magnetic conduction block forming dies 7 are uniformly arranged on the bottom die 92, and a protruding surface 6 is formed between adjacent magnetic conduction block forming dies 7. A plurality of protruding forming dies 11 are uniformly arranged on the inner surface of the outer ring body 91, and each protruding forming die 11 is respectively located between the magnetic conduction block forming dies 7.

[0038] Based on the above split die structure, the specific forging method for forging the integral magnetic yoke ring in this embodiment includes the following steps: a. Prepare a hollow steel ingot, and use a hole expanding device to expand the aperture of the inner ring hole 12 on the hollow steel ingot to obtain an annular steel blank 8.

[0039] Specifically, use a hole expanding device to expand the aperture of the inner ring hole 12 to be greater than and close to the outer diameter of the inner ring body 90 of the split die 9, control the height of the hollow steel ingot to be greater than the height of the finished magnetic yoke ring, control the outer diameter of the hollow steel ingot to be close to the outer diameter of the finished magnetic yoke ring, and control the height of the annular steel blank 8 to be lower than the height of the inner ring body 90.

[0040] Preferably, when using a hole expanding device to expand the inner ring hole diameter of the hollow ingot, the height of the obtained annular billet 8 is controlled to be 1.1-1.2 times the height of the finished yoke ring. This design of the height margin reserves sufficient processing space for subsequent spinning forging in the mold, ensuring that the annular billet 8 can fully fill the forging cavity of the tire mold during the spinning process, thereby ensuring good filling and density at the outer circumferential corner part of the finished yoke ring.

[0041] b. Place the tire mold 9 in the spinning device and place it on the rotating table 10. Then, place the annular billet 8 into the forging cavity, making the lower end face of the annular billet 8 abut against the convex surface 6 between the adjacent magnetic conduction block forming molds 7, the circumferential surface of the annular billet 8 abut against the inner surface of the convex forming mold 11, and the upper end face of the annular billet 8 is exposed between the upper end face of the inner ring body 90 and the upper end face of the outer ring body 91 as the spinning operation surface. Use the spinning device to spin the annular billet 8. During the spinning process: the circumferential surface of the annular billet 8 is extruded by the convex forming mold 11 and extends outward. Here, "outward" is radially outward defined based on the center of the annular billet 8. At this time, due to the resistance between the adjacent convex forming molds 11 in the forging cavity, several protruding parts 5 will be formed on the circumferential surface of the annular billet 8; at the same time, the part of the lower end face of the annular billet 8 corresponding to the magnetic conduction block forming mold 7 is pressed and extends downward. Due to the resistance of the bottom mold 92 in the forging cavity, several magnetic conduction blocks 2 will be formed on the lower end face of the annular billet 8.

[0042] In this step during the spinning process, it is preferred to use the narrow anvil spinning technology, and the anvil width of the narrow anvil is less than 900 mm. In this way, the radial flow of the metal can be accurately controlled, enabling the magnetic conduction blocks 2 and the protruding parts 5 to closely fit the forging cavity of the tire mold 9, achieving high-precision integral forming and ensuring the dimensional accuracy and density of each part of the yoke structure.

[0043] c. Demold the annular billet 8 with the protruding parts 5 and the magnetic conduction blocks 2 formed to obtain a yoke ring forging with the annular steel 1, the protruding parts 5, and the magnetic conduction blocks 2 integrally formed as shown in Figures 3 - 5 ; finally, through finishing processing, obtain the finished yoke ring as shown in Figures 6 - 8 .

[0044] In the present invention, "a. Prepare a hollow steel ingot, and use a hole expanding device to expand the aperture of the inner ring hole on the hollow steel ingot to obtain an annular billet; b. Place the die in a spinning device, put the annular billet into the forging cavity, make the lower end face of the annular billet abut against the convex surface between the magnetic conductive block forming dies, the circumferential surface of the annular billet abut against the convex forming die, and the upper end face of the annular billet expose between the upper end face of the inner ring body and the upper end face of the outer ring body. Use the spinning device to spin the annular billet. During the spinning process, the circumferential surface of the annular billet is extruded and extended outwards by the convex forming die until a number of protruding parts are formed on the circumferential surface of the annular billet; and the part of the lower end face of the annular billet corresponding to the magnetic conductive block forming die is pressed and extended downwards until a number of magnetic conductive blocks are formed on the lower end face of the annular billet; c. Demold and finish process the annular billet with the protruding parts and magnetic conductive blocks formed thereon to obtain a finished magnetic yoke ring", as a complete technical solution, compared with the prior art, this method realizes the integral forming of the annular steel, the protruding parts and the magnetic conductive blocks through die forging and spinning forging technologies, omits the processes of separately processing the annular steel and the magnetic conductive blocks, welding the magnetic conductive blocks and subsequent processing of the magnetic conductive blocks in the traditional process, and at the same time reduces the large amount of machining allowance reserved due to welding deformation, not only saves materials, significantly shortens the processing cycle, but also greatly reduces the manufacturing cost. In addition, it avoids the potential risks caused by poor welding quality and further improves the reliability and safety of the operation of the magnetic yoke structure.

[0045] Further, in step a, the method for preparing the hollow steel ingot includes the following steps: a1. Prepare a cylindrical blank Perform pressing the tong head treatment, chamfering treatment, removing the nozzle treatment, removing the riser treatment, primary upsetting treatment, drawing out to a square treatment, rounding treatment, and blanking treatment on the steel ingot in sequence to obtain a cylindrical blank.

[0046] During the process of removing the riser treatment, it is necessary to ensure sufficient riser removal amount to ensure the elimination of defects such as porosity and shrinkage cavity caused by riser residue, and avoid safety accidents such as fracture of the magnetic yoke ring due to internal hidden dangers during the operation of the subsequent large-capacity high-speed pumped storage unit.

[0047] The ingot used in this step needs to be prepared through the following steelmaking process: successively carrying out raw material preparation, electric arc furnace melting, secondary refining, vacuum degassing, argon protection casting, ingot cooling, ingot demoulding, and hot rotary forging, etc. Specifically, in the raw material preparation stage, the selected raw materials include nickel pig iron and return materials, and the proportion of nickel pig iron is ≥30wt% (mass percentage) to ensure the strength, toughness, and high-temperature resistance of the steel. Subsequently, the selected raw materials are placed into the electric arc furnace for melting, and the melting temperature range is preferably between 1300°C and 1400°C to obtain molten steel that meets the requirements. Then, the obtained molten steel is subjected to impurity removal through the secondary refining process, and then the molten steel with impurities removed is poured into a vacuum device for vacuum degassing treatment. After the degassing operation is completed, the molten steel is poured into an ingot mold and then demoulded to obtain an ingot. The entire casting process is protected by argon to prevent the molten steel from oxidizing.

[0048] Before preparing the cylindrical blank from the ingot, the ingot needs to be heated to 1100 - 1150°C and held at this temperature for 10 - 11h to ensure uniform temperature inside and outside the ingot.

[0049] Meanwhile, when initially upsetting the ingot, the upsetting ratio is set to 2.0 - 2.5; when elongating the ingot to a square shape, the wide anvil large reduction method, that is, the WHF main deformation method, is adopted, and the anvil width of the wide anvil is greater than 1100mm. This parameter range can not only effectively break the as-cast structure, forge the internal looseness defects of the ingot, and promote the transformation of the ingot from the as-cast structure to the forged structure, but also fully forge the internal defects of the ingot, thereby obtaining a cylindrical blank with a denser and more uniform structure.

[0050] a2. Preparation of a hollow ingot The cylindrical blank is successively subjected to re-upsetting treatment, spinning treatment from the outer circumference to the center, rounding treatment, and axial punching treatment using a hollow drill to obtain a hollow ingot with an inner ring hole 12. Among them, the upsetting ratio of the re-upsetting is set to 2.5 - 3.0. This parameter range can not only further effectively break the as-cast structure but also avoid defects caused by excessive deformation; during the spinning treatment from the outer circumference to the center, the narrow anvil spinning technology is preferably adopted, and the anvil width of the narrow anvil is less than 900mm to make the cylindrical blank generate more accurate plastic flow; During the forging process of the hollow ingot in steps a1 and a2, through the forging processes of initial upsetting and re-upsetting, the as-cast structure can be effectively broken and refined, internal defects can be forged, the tissue uniformity can be improved, and at the same time, the shape and size of the blank can be reasonably adjusted to ensure the forging quality of the yoke ring.

[0051] The working principle of the present invention is as follows: The split die 9 is fixed on the rotating table 10 in the spinning equipment, and then the annular steel blank 8 is nested and installed in the forging cavity of the split die 9 through its inner ring hole 12 and the inner ring body 90 of the split die 9. Then, pressure is applied by the spinning equipment, and this pressure is transmitted to theFigure 1 The upper end surface of the annular steel blank 8 in the shown direction promotes the metal to flow mainly towards the outer circumferential direction and downward by spinning the height of the annular steel blank 8. Due to the resistance of the forging cavity of the die 9 to the metal flow, the flow direction of the metal is changed. On the premise of ensuring that the height of the annular steel blank 8 is reduced and the size of the inner ring hole 12 remains unchanged, only the outer diameter size of the annular steel blank 8 is increased to ensure that the metal fully fills the forging cavity of the die 9, fully ensuring the fullness and density of the outer circumferential corner part of the finished yoke ring. Finally, the integrated forming process goal of combining die forging and spinning forging of extra-large rings is successfully achieved. At the same time, it also ensures that the yoke can meet the strict standards for key parameters such as mechanical properties and impact energy during the operation of large-capacity and high-speed pumped storage units.

[0052] Taking the contour dimensions of the finished yoke ring obtained by forging as φ6800×φ6200×φ1100mm as an example, the forging method of this integrated yoke ring of the present invention will be further described below in conjunction with specific embodiments.

[0053] Example 1 In this embodiment, it is completed by the following processes: The first step, raw material preparation: Select nickel pig iron and return materials as raw materials, where the proportion of nickel pig iron = 30wt%. The second step, ingot preparation: Put the selected raw materials into an electric arc furnace for melting to obtain molten steel. Among them, the melting temperature is 1300°C. Then, the obtained molten steel is refined outside the furnace to remove impurities, and then the molten steel after removing impurities is poured into a vacuum device for vacuum degassing treatment. After completing the degassing operation, the molten steel is poured into a ingot mold and demolded to obtain an ingot. The whole casting process is protected by argon to prevent the molten steel from oxidizing.

[0054] The third step, ingot heating and heat preservation: Heat the ingot to 1100°C and keep it at this temperature for 10 hours to ensure that the temperature inside and outside the ingot is uniform.

[0055] The fourth step, ingot riser and sprue removal treatment: The ingot is successively subjected to pressing the tongs handle treatment, chamfering treatment, sprue removal treatment, and riser removal treatment. During the riser removal treatment, it is necessary to ensure sufficient riser cutting amount to ensure the elimination of defects such as porosity and shrinkage caused by riser residue.

[0056] The fifth step, primary upsetting plastic treatment of the ingot: The ingot after removing the sprue and riser is successively subjected to primary upsetting treatment, drawing to a square treatment, rounding treatment, and blanking treatment to obtain a cylindrical blank. Among them, the primary upsetting ratio is 2.0; when drawing to a square treatment, the wide anvil large reduction method, that is, the WHF main deformation method, is used, and the anvil width of the wide anvil is greater than 1100mm.

[0057] Step 6. Reducing and plastic processing and punching of the cylindrical blank: The cylindrical blank is successively subjected to re-reducing treatment, spinning treatment from the outer circumference to the center, rolling treatment, and axial punching treatment with a hollow drill to obtain a hollow ingot with an inner ring hole 12. Among them, the re-reducing ratio is 2.5.

[0058] Step 7. Hole expanding treatment of the hollow ingot: Use a hole expanding device to expand the aperture of the inner ring hole 12 on the hollow ingot to obtain an annular blank 8. After hole expanding, the inner diameter of the inner ring hole 12 is 6200 mm, approximately equal to the outer diameter φ6120 mm of the die; during the hole expanding process, the height of the blank is synchronously controlled, and a machining allowance is reserved according to 1.1 times the height 1100 mm of the finished yoke ring, that is, the height of the annular blank is processed to 1210 mm.

[0059] Step 8. Forging and forming of the annular blank: Place the die 9 in a spinning device, then put the annular blank 8 into the forging cavity. The upper end face of the annular blank 8 is exposed between the upper end face of the inner ring body 90 and the upper end face of the outer ring body 91 as the spinning operation surface. Then use the narrow anvil spinning technology to spin the height of the annular blank 8, and the anvil width of the narrow anvil is less than 900 mm. Synchronously, with the help of the die cavity constraint force, especially the cooperation of the convex surface 6, the magnetic conduction block forming die 7, and the convex forming die 11 in the forging cavity, drive the metal of the annular blank to be filled into each surface of the forging cavity in a directional manner. When the height of the blank 8 reaches the size of the finished yoke ring 1100 mm, that is, when the reserved allowance is removed, the annular blank 8 completely fills the forging cavity, and the magnetic conduction block 2 and the protruding part 5 are integrally formed on the annular blank 8.

[0060] Step 9. Machining treatment of the annular blank: Finish machining the annular blank 8 on which the magnetic conduction block 2 and the protruding part 5 are integrally formed to obtain the Figures 6 - 8 finished product as shown.

[0061] Example 2 The process of this example is the same as that of Example 1, the differences are as follows: In the raw material preparation of the first step, the proportion of nickel pig iron = 35 wt%; In the process of preparing the ingot in the second step, the melting temperature of the selected raw materials in the electric arc furnace is 1350 °C; In the process of heating and heat preservation treatment of the ingot in the third step, the ingot is heated to 1130 °C and heat-preserved at this temperature for 10.5 h to ensure uniform temperature inside and outside the ingot; In the process of primary upsetting and plastic processing of the ingot in the fifth step, the upsetting ratio of the ingot after cutting off the nozzle and riser is 2.2; In the process of re-upsetting and plastic processing of the cylindrical blank in the sixth step, the upsetting ratio of the cylindrical blank is 2.8; During the reaming process of the hollow ingot in the seventh step, the height of the blank is synchronously controlled, and the machining allowance is reserved at 1.15 times the height of the finished yoke ring, which is 1100 mm. That is, the height of the annular steel blank is processed to 1265 mm.

[0062] Example 3 This example has the same process as Example 1, except that: In the raw material preparation of the first step, the proportion of ferronickel is 40 wt%. During the ingot preparation process of the second step, the melting temperature of the selected raw materials in the electric arc furnace is 1400 °C. During the ingot heating and heat preservation process of the third step, the ingot is heated to 1150 °C and heat-preserved at this temperature for 11 h to ensure uniform temperature inside and outside the ingot. During the first upsetting plastic treatment of the ingot in the fifth step, the upsetting ratio of the ingot after removing the nozzle and riser is 2.5. During the second upsetting plastic treatment of the cylindrical blank in the sixth step, the upsetting ratio of the cylindrical blank is 3.0. During the reaming process of the hollow ingot in the seventh step, the height of the blank is synchronously controlled, and the machining allowance is reserved at 1.2 times the height of the finished yoke ring, which is 1100 mm. That is, the height of the annular steel blank is processed to 1320 mm.

[0063] Based on the magnetic yoke rings with the magnetic conduction blocks 2 and the protruding parts 5 integrally formed on the annular steel 1 forged in the foregoing Examples 1-3, the cutting positions of the mechanical property specimens are arranged in the high-stress areas such as the T-shaped grooves or dovetail grooves on the outer edge thereof, that is, as Figure 9 、 Figure 10 shown, the corresponding area between the protruding part 5 and the extended boss 21 is used as the sampling area for the performance test of the finished magnetic yoke ring, and the axial sampling method is adopted. The specific sampling scheme is as follows: At the height positions 90 mm from the upper and lower end faces of the magnetic yoke ring respectively, a set of tensile specimens and three sets of impact specimens are intercepted; at the same time, tensile specimens are intercepted at the axial center section of the magnetic yoke ring (that is, at the 1 / 2 height position in the thickness direction). The test results show that for the mechanical property indexes such as the tensile strength, yield strength and impact energy of the specimens at each part, the magnetic yoke can meet the strict standards for the key parameters such as mechanical properties and impact energy required during the operation of large-capacity and high-speed pumped storage units, specifically as Figure 11 shown: The test results of the specimens intercepted at 90 mm from the end face of the magnetic yoke ring and at the axial center of the magnetic yoke ring are that the yield strength ≥ 690 MPa, the tensile strength ≥ 770 MPa, and the elongation ≥ 16%; the test result of the 0 °C impact energy of the specimens intercepted at 90 mm from the end face of the magnetic yoke ring is ≥ 68 J; the test result of the 0 °C impact energy of the specimens intercepted at the axial center of the magnetic yoke ring is ≥ 47 J.

[0064] The above are only specific embodiments of the present invention. Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features; all the features disclosed, or all the steps in any method or process, except for mutually exclusive features and / or steps, can be combined in any manner.

Claims

1. Forging method of an integrated magnetic yoke ring, characterized in that, This method is implemented based on a die forging die (9) and die forging technology. The die forging die (9) includes an inner ring body (90), an outer ring body (91), and a bottom die (92). The bottom die (92) is fixed between the lower ends of the inner ring body (90) and the outer ring body (91). The inner ring body (90), the outer ring body (91), and the bottom die (92) cooperate to form a forging cavity. A number of downwardly concave magnetic conduction block forming dies (7) are evenly arranged on the bottom die (92), and a convex surface (6) is formed between adjacent magnetic conduction block forming dies (7); a number of convex forming dies (11) are evenly arranged on the inner surface of the outer ring body (91), and each convex forming die (11) is respectively located between the magnetic conduction block forming dies (7). The forging method includes the following steps: a. Prepare a hollow ingot, and use a hole expanding device to expand the aperture of the inner ring hole on the hollow ingot to obtain an annular steel blank (8); b. Place the die forging die (9) in a spinning device, put the annular steel blank (8) into the forging cavity, make the lower end face of the annular steel blank (8) abut against the convex surface (6) between the magnetic conduction block forming dies (7), the circumferential surface of the annular steel blank (8) abut against the inner surface of the convex forming die (11), and the upper end face of the annular steel blank (8) is exposed between the upper end faces of the inner ring body (90) and the outer ring body (91). Use the spinning device to spin the annular steel blank (8). During the spinning process, the circumferential surface of the annular steel blank (8) is extruded and extended outward by the convex forming die (11) until a number of protrusions (5) are formed on the circumferential surface of the annular steel blank (8), and the part of the lower end face of the annular steel blank (8) corresponding to the magnetic conduction block forming die (7) is pressed and extended downward until a number of magnetic conduction blocks (2) are formed on the lower end face of the annular steel blank (8); c. Demold and finish machine the annular steel blank (8) formed with protrusions (5) and magnetic conduction blocks (2) to obtain a finished magnetic yoke ring.

2. The forging method of the integrated magnetic yoke ring according to claim 1, characterized in that: In the step a, the preparation method of the hollow ingot includes the following steps: a1. Prepare a cylindrical blank The ingot is successively subjected to pressing the tongs, chamfering, removing the sprue, removing the riser, primary upsetting, drawing out to a square shape, rounding, and blanking to obtain a cylindrical blank; a2. Prepare a hollow ingot The cylindrical blank is successively subjected to secondary upsetting, spinning from the outer circumference to the center, rolling round, and punching along the axis to obtain a hollow ingot.

3. The forging method of the integral magnetic yoke ring according to claim 2, characterized in that: The upsetting ratio of the primary upsetting is 2.0 - 2.5, and the upsetting ratio of the secondary upsetting is 2.5 - 3.

0.

4. The forging method of the integral magnetic yoke ring according to claim 1, characterized in that: In the step a, when using a hole expanding device to expand the aperture of the inner ring hole on the hollow ingot, control the height of the obtained annular steel blank (8) to be 1.1 - 1.2 times the height of the finished magnetic yoke ring.

5. The forging method of the integral magnetic yoke ring according to claim 3, characterized in that: The spinning in the steps b and a2 uses the narrow anvil spinning technology, and the anvil width of the narrow anvil is less than 900 mm.

6. The forging method of the integrated magnetic yoke ring according to claim 5, characterized in that: In the step a1, the method of drawing out the ingot to a square shape uses the wide anvil large reduction method, and the anvil width of the wide anvil is greater than 1100 mm.

7. The forging method of the integrated magnetic yoke ring according to claim 5, characterized in that: In the step a1, the raw materials selected for the ingot include nickel pig iron and return materials, and the proportion of nickel pig iron is ≥ 30 wt%.

8. The forging method of the integrated magnetic yoke ring according to any one of claims 1-7, characterized in that: In the step a, before preparing the cylindrical blank from the ingot, the ingot is heated to 1100 - 1150 °C and kept warm for 10 - 11 h.

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