Progressive zone forging method

Abstract

A progressive partitioning forging method is disclosed, comprising: a first forging step, wherein the first forging step uses a first die to press and form a central region of one surface of a preform disposed on a concave base, thereby forming a first protrusion on a central region of another surface of the preform; and a second forging step, wherein the second forging step uses a second die to press and form a peripheral region of one surface of the pressed preform, thereby forming one surface of the preform into a flat surface.

Description

Cross-reference to related applications

[0001] This application claims priority to Korean Patent Application No. 10-2025-0038817, filed on March 26, 2025, the entire contents of which are incorporated herein by reference for all purposes. Technical Field

[0002] This disclosure relates to a progressive partition forging method, and more specifically, to a progressive partition forging method capable of calculating the pressable cross-sectional area based on the limited press load capacity and the rheological stress of the material to obtain the specifications of multiple dies, and progressively performing pressing forming from the central portion of the preform toward the peripheral portion using multiple dies, thereby producing a shaped product of a superalloy material through multiple forging stages. Background Technology

[0003] A gas turbine is a rotary thermal engine that uses high-temperature, high-pressure combustion gases to operate a turbine, and typically includes a compressor, a combustor, and a turbine. The turbine includes components such as discs and blades.

[0004] Conventionally, turbine disks are formed entirely through a single-die forging method, which requires high forging loads. Therefore, manufacturing turbine disks using high-capacity presses involves high costs and long production times. Furthermore, turbine disks formed through rotary forging methods cannot meet the required quality levels.

[0005] Here, the turbine disk is made of a superalloy material. Because superalloys exhibit flow stress at high temperatures that is several times higher than that of ordinary carbon steel, forming the product by die forging requires a press with extremely high load capacity, which is far beyond the load capacity of presses used for carbon steel, thus causing technical difficulties.

[0006] In particular, turbine disks used in large gas turbines are made of nickel-based superalloys and are large in size as forged products, thus requiring forging presses with a capacity of 50,000 tons or more. When superalloys are forged at high strain rates using hammer forging methods, it is difficult to obtain high-quality products due to cracking, deformation heat, etc. during forging, and therefore it is necessary to use a press to forge the superalloys.

[0007] Therefore, a die and forging method is needed that reduces costs and manufacturing time compared to conventional processes, and enables the manufacture of medium to large forgings from superalloy materials using presses with relatively low load capacities. Furthermore, the specifications for applying multiple dies with pressable cross-sectional areas need to be determined by considering the limited load capacity of the press and the stable rheological stresses of the superalloy material during hot forging. Summary of the Invention

[0008] The purpose of this disclosure is to provide a step-by-step partition forging method that can calculate the pressable cross-sectional area based on the limited press load capacity and the rheological stress of the material to obtain the specifications of multiple dies, and can use multiple dies to perform pressing forming step by step from the central portion of the preform towards the peripheral portion, thereby manufacturing a formed product from a superalloy material through multiple forging stages.

[0009] The technical problems to be solved by this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

[0010] One embodiment is a progressive partition forging method, which includes: a first forging step, wherein the first forging step uses a first die to press and form a central region of one surface of a preform disposed on a concave base, thereby forming a first protrusion on a central region of another surface of the preform; and a second forging step, wherein the second forging step uses a second die to press and form a peripheral region of one surface of the pressed preform, thereby forming one surface of the preform into a flat surface.

[0011] According to the embodiment, the stepwise partitioning forging method further includes a third forging step, which uses a third die to press one surface of the preform to form a second protrusion in the central region of one surface of the preform.

[0012] According to the embodiment, the stepwise partitioning forging method further includes: a fourth forging step, which uses a second die to press and form a peripheral region of one surface of the preform while maintaining the second protrusion, thereby forming a third protrusion in a peripheral region of another surface of the preform; and a fifth forging step, which uses a fourth die to press and form an edge region of one surface of the preform, thereby forming a fourth protrusion that surrounds the second protrusion and has a lower height than the second protrusion.

[0013] According to an embodiment, the first mold has a cylindrical shape, and the concave base includes a first concave portion and a second concave portion, wherein the first concave portion is formed at the central portion of the concave base to be recessed into at least the bottom region of the first mold in the pressing direction, and the second concave portion is formed around the first concave portion to be recessed to a shallower depth than the first concave portion.

[0014] According to the embodiment, in the first forging step, the first protrusion can be formed to protrude a volume corresponding to the space of the first concave portion.

[0015] According to the embodiment, the outer diameter of the second mold is larger than the outer diameter of the first mold, the central part of the second mold is hollow and penetrates the second mold, and the inner diameter of the second mold is equal to or smaller than the diameter of the first concave part and is concentrically aligned with the first concave part.

[0016] According to the embodiment, the outer diameter of the third mold is smaller than that of the second mold, the central part of the third mold is hollow and penetrates the third mold, and the inner diameter of the third mold is formed to be the same as that of the second mold.

[0017] According to the implementation method, in the fourth forging step, the pressing and forming area may include the pressing and forming area in the third forging step, and the pressing and forming area may be larger than the pressing and forming area in the third forging step.

[0018] According to the embodiment, in the fourth forging step, the third protrusion is formed to protrude a volume corresponding to the space of the second concave portion, and the diameter of the third protrusion may be larger than the diameter of the fourth protrusion.

[0019] According to the implementation method, the outer diameter of the fourth mold is larger than the outer diameters of the first mold, the second mold and the third mold. The central part of the fourth mold is hollow and penetrates the fourth mold. The inner diameter of the fourth mold can be larger than the outer diameters of the first mold and the third mold and smaller than the outer diameter of the second mold.

[0020] According to the implementation method, the stepwise partition forging method further includes an upsetting step, which involves compressing a billet placed on a flat base using a press to form the billet into a preform before the first forging step.

[0021] According to the implementation method, the first mold, the second mold, the third mold and the fourth mold are pressed by a press, and the load capacity of the press can be set to 160 MN to 180 MN.

[0022] According to the embodiment, in the upsetting step, the billet is heated to 1000°C to 1100°C before being compressed by a press. After the upsetting step and before the first forging step, the preform is reheated to 1000°C to 1100°C. The preform can also be reheated to 1000°C to 1100°C after the second forging step and before the third forging step.

[0023] According to the embodiment, the formed product manufactured by the first to fifth forging steps is a turbine disk of a gas turbine made of a superalloy material, and the turbine disk can be formed to have a diameter of 1600 mm to 1800 mm.

[0024] According to the embodiment, the first protrusion and the second protrusion are symmetrical with respect to the center line of the molded product, and the third protrusion and the fourth protrusion can also be symmetrical with respect to the center line of the molded product.

[0025] According to this disclosure, the specifications of multiple dies can be derived by calculating the pressable cross-sectional area based on the press load capacity limited to the range of 160 MN to 180 MN and the rheological stress of the superalloy material. The cross-sectional area of ​​the multiple dies in contact with the preform can be set to be less than a predetermined area. Therefore, even using a press with limited load capacity, it is possible to manufacture formed products with a target shape made of superalloy material.

[0026] By using multiple dies and employing free forging and hot forging methods, and by progressively pressing the preform from the central portion toward the periphery in sections of the region, uniform forming and stable rheological stress of the superalloy material can be ensured.

[0027] Even when forming products using a press with relatively low load capacity through multiple forging steps, the formed products can still meet the required quality characteristics. The required quality characteristics refer to the effective strain, rheological stress, and deformation of the formed product that meet predetermined standards.

[0028] Each forging step can be completed in less than a minute, thereby reducing production costs and manufacturing time, and enabling the production of high-quality medium to large turbine disks made of superalloys using presses with low load capacity.

[0029] The effects of this disclosure are not limited to those described above, and those skilled in the art can derive other effects not described herein from the following description of the embodiments of this disclosure. Attached Figure Description

[0030] Figure 1 It is a three-dimensional view of a gas turbine for power generation and an enlarged cross-sectional view of the interior of a gas turbine for power generation.

[0031] Figure 2 This is a schematic diagram illustrating the entire process of a step-by-step forging method according to one embodiment of the present disclosure.

[0032] Figure 3 This is a diagram illustrating the process of an upsetting step according to one embodiment.

[0033] Figure 4 This is a diagram illustrating the result of an upsetting process according to one embodiment.

[0034] Figure 5 It is a diagram illustrating the process of the first forging step according to one embodiment.

[0035] Figure 6 It is a diagram illustrating the result of the first forging step according to one embodiment.

[0036] Figure 7 This is a diagram illustrating the process of the second forging step according to one embodiment.

[0037] Figure 8 This is a diagram illustrating the result of the second forging step according to one embodiment.

[0038] Figure 9 This is a diagram illustrating the process of the third forging step according to one embodiment.

[0039] Figure 10 This is a diagram illustrating the result of the third forging step according to one embodiment.

[0040] Figure 11 This is a diagram illustrating the process of the fourth forging step according to one embodiment.

[0041] Figure 12 This is a diagram illustrating the result of the fourth forging step according to one embodiment.

[0042] Figure 13 This is a diagram illustrating the process of the fifth forging step according to one embodiment.

[0043] Figure 14 This is a diagram illustrating the result of the fifth forging step according to one embodiment.

[0044] Figure 15 This is a perspective view of a concave base according to one embodiment.

[0045] Figure 16 It is along Figure 15 A cross-sectional view of the concave base intercepted by line X-X'.

[0046] Figure 17 This is a diagram illustrating a molded product according to one embodiment.

[0047] Figure 18 The diagram illustrates the machining process. Figure 17 A diagram of a turbine disk obtained from a molded product.

[0048] Figure 19 The figure illustrates a graph of rheological stress based on temperature and strain rate analysis, which is used to calculate the cross-sectional area of ​​multiple dies used in a stepwise partitioning forging method according to one embodiment.

[0049] The accompanying drawings illustrate preferred embodiments of the present disclosure and are intended to further enhance understanding of the technical concept of the disclosure in conjunction with the detailed description thereof. Therefore, the present disclosure should not be construed as limited to the contents shown in these drawings. Detailed Implementation

[0050] In the following description, a preferred embodiment of the step-by-step forging method according to the present disclosure will be described with reference to the accompanying drawings.

[0051] Furthermore, the terms described below are defined in consideration of the functionality of one or more exemplary embodiments, and these terms may have different meanings depending on the intent or convention of the user or operator. Moreover, the exemplary embodiments described below are not intended to limit the scope of this disclosure, but merely exemplify the construction elements defined in the claims.

[0052] To clearly illustrate the invention, components unrelated to the description have been omitted, and similar components are indicated by similar reference numerals throughout the specification. Throughout the specification, when a part "comprises" or "includes" a component, unless otherwise stated, this indicates that other components are not excluded and may also be included.

[0053] In this specification, regarding elements referred to as "units" or "modules," two or more elements may be combined into one element, or, depending on the subdivision of functions, one element may be divided into two or more elements. Furthermore, each element described below, in addition to its own primary function, may additionally perform some or all of the functions performed by another element, and some of the primary functions of each element may be entirely performed by another component.

[0054] First refer to Figures 1 to 4 The following describes a step-by-step forging method 1 according to one embodiment of the present disclosure.

[0055] According to one embodiment of the present disclosure, the step-by-step forging method 1 generally includes an upsetting step U, a first process R1, and a second process R2. The first process R1 includes a first forging step S1, a second forging step S2, and a third forging step S3. The second process R2 includes a fourth forging step S4 and a fifth forging step S5. Through the step-by-step forging method 1, the preform 10 can be manufactured into a formed product 20. However, the present disclosure is not limited thereto. In some embodiments, the step-by-step forging method 1 may include only the first process R1, and in this case, the first process R1 may include only the first forging step S1 and the second forging step S2.

[0056] exist Figure 1The top view shows a perspective view of a gas turbine for power generation, and the bottom view shows an enlarged internal cross-sectional view taken along line A-A' of the top view. Figure 1 In the lower view, from left to right, the compressor, burner, and turbine are arranged sequentially. The turbine section consists of a first stage, a second stage, a third stage, and a fourth stage, from left to right. The formed product 20, manufactured by step-by-step partition forging method 1, can be machined and used as the turbine disk T for stages 1 to 4.

[0057] Reference Figures 2 to 17 The stepwise partitioning forging method 1 according to one embodiment of the present disclosure will be described in detail below.

[0058] In the first process R1, the preform 10 mounted on the concave base 500 is pressed and formed by the first mold 100, the second mold 200, and the third mold 300, such that a first protrusion 11 and a second protrusion 12 can be formed in the central portion of the preform 10. Furthermore, after the first process R1, in the second process R2, the preform 10 is pressed and formed by the second mold 200 and the fourth mold 400, such that a third protrusion 13 and a fourth protrusion 14 can be formed in the peripheral portion of the preform 10.

[0059] Figure 3 The diagram illustrates the process of upsetting step U. In Figure 3 In the diagram, (a) shows the blank B before compression, and (b) shows the blank B formed into a preform 10. The upsetting step U is a step prior to the first forging step S1, in which the blank B mounted on the flat base F is compressed by a flat die P attached to the lower part of the press to form the preform 10.

[0060] Figure 4 The diagram illustrates the result of the upsetting step U. In Figure 4 In the diagram, (a) shows a perspective view of the structural analysis results of the preform 10, and (b) shows a cross-sectional view of the structural analysis results of the preform 10. Figure 4 As shown in (b), stress concentration occurs within the preform 10, resulting in internal non-uniformity, which can lead to cracking. Therefore, internal uniformity and stable rheological stress can be ensured by performing multiple forging steps S1, S2, S3, S4, and S5.

[0061] Figure 5 The diagram illustrates the process of the first forging step S1. Figure 5 In the diagram, (a) is a side view of the preform 10 pressed by the first mold 100, and (b) is a perspective view of the preform 10. Figure 5As shown, the first mold 100 can be formed into a cylindrical shape, and the preform 10 is mounted on the concave base 500 and pressed by the first mold 100. During the pressing process, the central axes of the preform 10, the first mold 100, and the concave base 500 are aligned.

[0062] Figure 6 The diagram illustrates the result of the first forging step S1. Figure 6 In the diagram, (a) is a perspective view of the preform 10 after it has been pressed and formed by the first die 100, and (b) is a cross-sectional view. In the first forging step S1, the central portion of one side of the preform 10, which is mounted on the concave base 500, is pressed and formed by the first die 100. During pressing and forming, a first protrusion 11 can be formed in the central portion of the opposite side of the preform 10. Here, one side of the preform 10 refers to the upper side, and the opposite side refers to the lower side.

[0063] Specifically, such as Figure 6 , Figure 15 and Figure 16 As shown, the concave base 500 may include a first concave portion 501 and a second concave portion 502. The first concave portion 501 may be formed in the central portion of the concave base 500 such that it is recessed into at least the bottom region of the first mold 100 in the pressing direction. The second concave portion 502 may be formed around the first concave portion 501 such that a high step portion d1 exists. That is, the second concave portion 502 is recessed to a shallower depth than the first concave portion 501. Furthermore, the second concave portion 502 is lower than the top surface of the concave base 500 and may have a low step portion d2. Therefore, in the first forging step S1, the first protrusion 11 may be formed to protrude from the volume of the first concave portion 501.

[0064] Figure 7 The diagram illustrates the process of the second forging step S2. Figure 7 In the image, (a) is a side view of the preform 10 pressed by the second mold 200, and (b) is a perspective view of the preform 10. Figure 8 The diagram illustrates the result of the second forging step S2. Figure 8 In the figure, (a) is a perspective view of the preform 10 after it has been pressed and formed by the second mold 200, and (b) is a cross-sectional view.

[0065] like Figures 6 to 8 As shown, in the second forging step S2, the peripheral region of the central portion of one side of the preform 10, which was pressed and formed in the first forging step S1, can be pressed and formed using the second die 200. Therefore, one side of the preform 10 can be formed into a flat shape.

[0066] Furthermore, the outer diameter of the second mold 200 is larger than that of the first mold 100, and the central portion of the second mold 200 can be hollow and penetrate through the second mold 200. That is, the second mold 200 can be formed into a ring shape. The inner diameter of the second mold 200 can be equal to or smaller than the diameter of the first concave portion 501 and is concentrically aligned with the first concave portion 501. The area pressed by the second mold 200 partially overlaps with the area pressed by the first mold 100 to prevent burr formation.

[0067] Figure 9 The diagram illustrates the process of the third forging step, S3. Figure 9 In the figure, (a) is a side view of the preform 10 pressed by the third mold 300, and (b) is a perspective view of the preform 10. Figure 10 The diagram illustrates the result of the third forging step S3. Figure 10 In the figure, (a) is a perspective view of the preform 10 after it has been pressed and formed by the third mold 300, and (b) is a cross-sectional view.

[0068] like Figures 8 to 10 As shown, in the third forging step S3, one side of the preform 10 can be pressed and formed using the third die 300. Therefore, a second protrusion 12 can be formed in the central region of one side of the preform 10. Here, the outer diameter of the third die 300 can be smaller than the outer diameter of the second die 200, and the central portion of the third die 300 can be hollow and penetrate through the third die 300. That is, the third die 300 can be formed into an annular shape. The inner diameter of the third die 300 can be equal to the inner diameter of the second die 200, which will be described in conjunction with the fourth forging step S4.

[0069] Figure 11 The diagram illustrates the process of the fourth forging step, S4. Figure 11 In the image, (a) is a side view of the preform 10 pressed by the second mold 200, and (b) is a perspective view of the preform 10. Figure 12 The diagram illustrates the result of the fourth forging step (S4). Figure 12 In the figure, (a) is a perspective view of the preform 10 after it has been pressed and formed by the second mold 200, and (b) is a cross-sectional view.

[0070] like Figures 10 to 12 As shown, in the fourth forging step S4, the peripheral region of one side of the preform 10 can be pressed and formed by the second die 200 while holding the second protrusion 12. The region pressed and formed in the fourth forging step S4 can include the region pressed and formed in the third forging step S3, and can be larger.

[0071] Furthermore, the inner diameter of the third die 300 can be formed to be equal to the inner diameter of the second die 200. In the fourth forging step S4, in order to prevent the central hollow portion of the second die 200 from affecting the second protrusion 12, the inner diameter of the second die 200 can be equal to or greater than the inner diameter of the third die 300.

[0072] After the fourth forging step S4, a third protrusion 13 can be formed on the peripheral region of the opposite side of the preform 10. (Refer to...) Figures 15 to 17 The third protrusion 13 can protrude by an amount that the second concave portion 502. Furthermore, the diameter of the third protrusion 13 can be larger than the diameter of the fourth protrusion 14.

[0073] Figure 13 The diagram illustrates the process of the fifth forging step, S5. Figure 13 In the image, (a) is a side view of the preform 10 pressed by the fourth mold 400, and (b) is a perspective view of the preform 10. Figure 14 The diagram illustrates the result of the fifth forging step, S5. Figure 14 In the figure, (a) is a perspective view of the preform 10 after it has been pressed and formed by the fourth mold 400, and (b) is a cross-sectional view.

[0074] Refer again Figures 5 to 17 In the fifth forging step S5, the edge region of one side of the preform 10 can be pressed and formed using the fourth die 400. The outer diameter of the fourth die 400 can be larger than the outer diameters of the first die 100, the second die 200, and the third die 300, and the central portion of the fourth die 400 can be hollow and penetrate through the fourth die 400. The inner diameter of the fourth die 400 can be larger than the outer diameters of the first die 100 and the third die 300 and smaller than the outer diameter of the second die 200. Through the fifth forging step S5, a fourth protrusion 14 can be formed, which surrounds the second protrusion 12 and has a lower height than the second protrusion 12 to provide a stepped portion d2.

[0075] exist Figure 17 The diagram shows a preform 20 produced by a step-by-step partition forging method 1. Referring to the structure of the preform 20, the first protrusion 11 and the second protrusion 12 can be formed symmetrically with respect to the center line C-C' of the preform 20. Similarly, the third protrusion 13 and the fourth protrusion 14 can also be symmetrical with respect to the center line C-C'. Preferably, this symmetry is considered to be proportional, since the dimensions can vary.

[0076] Figure 18 The diagram illustrates the machining process. Figure 17 The turbine disk T is obtained by preforming the part 20 shown in the figure. Figure 18In the process, the turbine disk T is formed by cutting and machining the outer surface of the preform 20, and Figure 17 Preform 20 and Figure 18 The dimensional differences between the turbine disks T are minimal. The preform 20 is formed from a superalloy material and constitutes the turbine disk T for a gas turbine, wherein the turbine disk T can have a diameter ranging from 1600 mm to 1800 mm.

[0077] Figure 19 The figure illustrates a graph of the rheological stress as a function of temperature and strain rate, which is used to calculate the cross-sectional areas of multiple dies 100, 200, 300, and 400 used in the stepwise partitioned forging method 1.

[0078] Reference Figures 2 to 19 According to the step-by-step forging method 1, the preform 10 can be pressed and formed by gradually increasing the area from the center of the preform 10 in the radial direction, so as to form multiple stepped parts d1, d2.

[0079] The flat die P, first die 100, second die 200, third die 300, and fourth die 400 used for pressing are pressed by a press, wherein the press may have a load capacity set in the range of 160 MN to 180 MN. Additionally, the edges of the first die 100, second die 200, third die 300, and fourth die 400 that contact the preform 10 may be chamfered or rounded to prevent stress concentration.

[0080] In the upsetting step U, the billet B can be heated to a temperature in the range of 1000°C to 1100°C before being compressed by a press. After the upsetting step U and before the first forging step S1, the preform 10 can be reheated to a temperature in the range of 1000°C to 1100°C. Similarly, after the second forging step S2 and before the third forging step S3, the preform 10 can be reheated to a temperature in the range of 1000°C to 1100°C.

[0081] The time required for each step of the progressive forging method 1 is approximately as follows: upsetting step U takes about 58 seconds; the first forging step S1 takes about 7.7 seconds; the second forging step S2 takes about 5.6 seconds; the third forging step S3 takes about 4.1 seconds; the fourth forging step S4 takes about 3.3 seconds; and the fifth forging step S5 takes about 4.4 seconds.

[0082] The cross-sectional areas of the first mold 100, the second mold 200, the third mold 300, and the fourth mold 400 can be calculated and determined based on at least one of the press load capacity, the material type of the preform 10, and the rheological stress depending on the heating temperature. Here, the cross-sectional area of ​​the first mold 100, the second mold 200, the third mold 300, and the fourth mold 400 refers to the area of ​​the horizontally cut surface in contact with the preform 10.

[0083] The cross-sectional areas of the first die 100, the second die 200, the third die 300, and the fourth die 400 can be set to values ​​obtained by dividing the maximum load capacity of the press by the strain rate and the rheological stress. Additionally, the inner diameter of any one of the first die 100, the second die 200, the third die 300, and the fourth die 400 can be set to be smaller than the maximum outer diameter of the preceding die, causing the forging areas to overlap.

[0084] The cross-sectional areas of the multiple dies 100, 200, 300, and 400 used in the stepwise partitioned forging method 1 can be calculated by analyzing the flow stress of the material as a function of temperature and strain rate. (Refer to...) Figure 19 The curve shows that when IN706 superalloy material is forged using a press with a load capacity of 170MN, the maximum permissible cross-sectional area can be calculated to be approximately 1.06 m². 2 .

[0085] Specifically, in Figure 19 The graph shows the rheological stress of IN706 material as a function of strain rate at a forging temperature of 1000°C. Figure 19 (a) indicates that the calculated rheological stress is 150 MPa at a forging temperature of 1000°C and a strain rate of 0.01 / sec. Figure 19 (b) indicates that the rheological stress was calculated to be 240 MPa at a forging temperature of 1000°C and a strain rate of 0.1 / sec.

[0086] Based on a press with a load capacity of 170 MN, the initial strain rate of IN706 was calculated to be 0.011 / sec. The strain rate was also calculated to be 0.011 / sec when the pressing speed was set to 17 mm / sec and the initial upsetting height was set to 1500 mm. (Refer to...) Figure 19 The curve corresponds to a flow stress of approximately 160 MPa at a strain rate of 0.011 / sec.

[0087] Therefore, according to the pressure equation, the calculation is established as: 170 MN / area = 160 MPa (160 N / mm²). Solving this equation, the cross-sectional area is calculated to be approximately 1.06 m². Therefore, the cross-sectional areas of the first mold 100, the second mold 200, the third mold 300, and the fourth mold 400 can each be set to be equal to or less than approximately 1.06 m². 2 In other words, the cross-sectional areas of multiple molds of 100, 200, 300, and 400 can be determined by taking into account the load capacity of the press and the rheological stress of the material.

[0088] Therefore, according to the stepwise partitioning forging method 1 of the present disclosure, the specifications of the plurality of dies 100, 200, 300, and 400 can be determined by calculating the compressible cross-sectional area based on the press load capacity limited to the range of 160 MN to 180 MN and the rheological stress of the superalloy material. The cross-sectional area of ​​the plurality of dies 100, 200, 300, and 400 in contact with the preform 10 can be set to be equal to or less than a predetermined area. Therefore, even if the press has a limited load capacity, forged products with a target shape made of superalloy material can be produced.

[0089] Furthermore, by combining multiple dies 100, 200, 300, and 400 with free forging and hot forging, and by pressing the preform 10 stepwise from the central portion toward the periphery in units of area, uniform forging and stable rheological stress of the superalloy material can be ensured.

[0090] Furthermore, even when forging is performed using a press with relatively low load capacity through multiple forging steps S1, S2, S3, S4, and S5, the forged product 20 can still meet the required quality characteristics. The required quality characteristics refer to the effective strain, rheological stress, and deformation of the forged product 20 that meet predetermined standards. Therefore, high-quality medium to large turbine disks made of superalloys can be manufactured using a press with relatively low load capacity.

[0091] In addition, the processing time for each forging step S1, S2, S3, S4, and S5 can be minimized to less than one minute, thereby reducing production costs and shortening the manufacturing cycle of the forged product 20.

[0092] This disclosure is not limited to the specific embodiments and descriptions described above, and those skilled in the art can make various modifications without departing from the spirit of this disclosure as claimed in the claims. Such changes are within the scope of protection of this disclosure. List of reference numerals 1: Step-by-step zone forging method U: Upsetting steps P: Flat mold F: Flat base B: Billet S1: First Forging Step S2: Second forging step S3: Third Forging Step S4: Fourth Forging Step S5: Fifth Forging Step 10: Preforms 11: First protrusion 12: Second protrusion 13: Third protrusion 14: Fourth protrusion 20: Molded products 100: First mold 200: Second mold 300: Third mold 400: Fourth mold 500: Concave base 501: First concave portion 502: Second concave portion d1: High step section d2: Low step section T: Turbine disk

Claims

1. A step-by-step zone forging method, comprising: In the first forging step, a first die is used to press and form the central region of one surface of a preform placed on a concave base, thereby forming a first protrusion in the central region of the other surface of the preform. as well as In the second forging step, a second die is used to press and shape the peripheral area of ​​one surface of the preform, so that the one surface of the preform is flat.

2. The step-by-step forging method according to claim 1 further includes: The third forging step involves pressing one surface of the preform using a third die to form a second protrusion in the central region of that surface.

3. The step-by-step forging method according to claim 2 further includes: The fourth forging step involves pressing the peripheral region of one surface of the preform using the second die while maintaining the second protrusion, thereby forming a third protrusion in the peripheral region of the other surface of the preform. The fifth forging step involves pressing an edge region of one surface of the preform using a fourth die to form a fourth protrusion that surrounds the second protrusion and has a lower height than the second protrusion.

4. The step-by-step forging method according to claim 1, in, The first mold has a cylindrical shape, and the concave base includes a first concave portion and a second concave portion, and The first concave portion is formed at the central portion of the concave base to be recessed into the bottom region of the first mold in the pressing direction, and the second concave portion is formed around the first concave portion to be recessed to a shallower depth than the first concave portion.

5. The step-by-step forging method according to claim 4, in, In the first forging step, the first protrusion is formed to protrude a volume corresponding to the space of the first concave portion.

6. The step-by-step forging method according to claim 4, in, The outer diameter of the second mold is larger than that of the first mold, and the central portion of the second mold is hollow and penetrates the second mold. The inner diameter of the second mold is equal to or smaller than the diameter of the first concave portion and is concentrically aligned with the first concave portion.

7. The step-by-step forging method according to claim 2, in, The outer diameter of the third mold is smaller than that of the second mold, and the central portion of the third mold is hollow and penetrates the third mold. The inner diameter of the third mold is formed to be the same as that of the second mold.

8. The step-by-step forging method according to claim 3, in, In the fourth forging step, the pressing and forming region includes the region pressing and forming in the third forging step, and the pressing and forming region is larger than the region pressing and forming in the third forging step.

9. The step-by-step forging method according to claim 3, in, In the fourth forging step, the third protrusion is formed to protrude a volume corresponding to the space of the second concave portion, and The diameter of the third protrusion is larger than the diameter of the fourth protrusion.

10. The step-by-step forging method according to claim 3, in, The outer diameter of the fourth mold is larger than that of the first mold, the second mold, and the third mold. The central portion of the fourth mold is hollow and penetrates through the mold. The inner diameter of the fourth mold is greater than the outer diameters of the first mold and the third mold, but smaller than the outer diameter of the second mold.

11. The step-by-step forging method according to claim 3, further comprising: Prior to the first forging step, an upsetting step is performed in which a blank placed on a flat base is compressed by a press to form the preform.

12. The step-by-step partitioning forging method according to claim 11, in, The first mold, the second mold, the third mold, and the fourth mold are pressed by the press, and the load capacity of the press is set to 160 MN to 180 MN.

13. The step-by-step forging method according to claim 11, in, In the upsetting step, the billet is heated to 1000°C to 1100°C before being compressed by the press. After the upsetting step and before the first forging step, the preform is reheated to 1000°C to 1100°C. After the second forging step and before the third forging step, the preform is reheated to 1000°C to 1100°C.

14. The step-by-step forging method according to claim 3, in, The formed product manufactured by the first to the fifth forging steps is a turbine disk of a gas turbine made of a superalloy material, and the turbine disk is formed to have a diameter of 1600 mm to 1800 mm.

15. The step-by-step forging method according to claim 3, in, The first protrusion and the second protrusion are symmetrical with respect to the center line of the molded product, and the third protrusion and the fourth protrusion are also symmetrical with respect to the center line of the molded product.

Images