Method for reducing die forging forming tonnage of oversize GH4169 alloy turbine disc

Abstract

The invention belongs to the field of metal material processing and forming, and discloses a method for reducing the die forging forming tonnage of a super-huge GH4169 alloy turbine disc, which comprises the following steps of: dividing a forge piece into a hub area, a radial plate area and a rim area along the radial direction; the wheel hub is placed according to the shape; the radial plate is designed in a non-shape-following manner, so that height differences H1 and H2 are respectively formed between the radial plate and the upper and lower surfaces of the hub; a flow control slope composed of a first inclined face (theta1) and a second inclined face (theta2) is constructed at the transition position of the radial plate and the rim. A die cavity is constructed according to the shape of the forge piece, a pressure reduction slope composed of an inclined face (theta3) and the opening height H3 is arranged on the outer side of the die, and the conditions that H3 is equal to 235-1.2 theta3, and theta3 is equal to 40-75 degrees are met. According to the method, metal is guided to be sequentially filled through the flow control slope, a traditional bridge part is replaced by the pressure reduction slope, the die forging tonnage is remarkably reduced, the GH4169 extra-large turbine disc forge piece with the diameter larger than or equal to 2 m can be formed on a 800 MN press at a time, and the quality of the forge piece is good.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing and forming technology, specifically relating to a method for reducing the tonnage of die forging extra-large GH4169 alloy turbine discs, which is particularly suitable for die forging of ultra-large GH4169 alloy turbine disc forgings with a diameter of more than 2 meters. Background Technology

[0002] As a core piece of equipment in the energy sector, heavy-duty gas turbines rely on their turbine discs, which are critical hot-end components subjected to high temperatures (600-800℃), high pressures, and high-speed centrifugal forces, directly determining the turbine's efficiency and reliability. GH4169 alloy, with its excellent high-temperature strength, oxidation resistance, and fatigue resistance below 650℃, has become the preferred material for turbine disc forgings.

[0003] As the power rating of gas turbines increases, the size of turbine discs continues to grow. Currently, the GH4169 alloy turbine discs used in 300MW heavy-duty gas turbines have a diameter of over 2 meters after precision machining, classifying them as ultra-large turbine disc forgings. The preparation of such extra-large turbine disc forgings is a first in China, and there is a lack of mature production experience to draw upon.

[0004] An 800MN die forging press provides the necessary power equipment for the preparation of ultra-large turbine disc forgings of GH4169 alloy. However, simply having a large-tonnage press is insufficient to guarantee forming quality; specific forging and die design schemes are still unclear. If conventional forging design methods are adopted, such as uniformly increasing the forging profile to perfectly match the finished product shape, setting a draft angle of 3–10°, and incorporating a traditional bridge-structured material storage groove (e.g., ...) at the die edge... Figure 2-3 As shown in the figure, this will lead to excessive metal flow resistance, resulting in severe extrusion in the bridge area during the later stages of forming. The forging tonnage will far exceed the limit of the 800MN equipment, making it impossible to complete production.

[0005] Therefore, there is an urgent need to develop a forging design and die forging method that can successfully form GH4169 alloy extra-large turbine disc forgings within the existing 800MN press capacity. Summary of the Invention

[0006] The purpose of this invention is to provide a method for reducing the tonnage of forging extra-large GH4169 alloy turbine discs. By optimizing the geometry of the forging and the design of the mold cavity, the forging load is significantly reduced, enabling extra-large GH4169 alloy turbine discs with a diameter of more than 2 meters to be forged in one go on an 800MN press.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for reducing the tonnage of forging extra-large GH4169 alloy turbine disks, comprising the following steps: Step 1: Based on the finished structure of the turbine disc, the forging is divided radially from the inside to the outside into the hub area for forming the disc hub, the spoke area connecting the hub and the rim, and the rim area located at the outermost edge. Step 2: Perform conformal design on the hub area to determine the forging profile of the hub part; Step 3: Perform a non-conformal design on the spoke area so that the upper and lower surfaces of the spoke area and the upper and lower surfaces of the hub area determined in Step 2 form a first height difference H1 and a second height difference H2, respectively. Step 4: At the transition between the spoke area and the rim area, construct a metal flow control slope; the flow control slope includes a first slope and a second slope, the starting point of the first slope is located at point A, after the machining allowance is increased in the radial and height directions of the corresponding part of the finished product, and the first slope forms a first angle θ1 with the vertical direction; the starting point of the second slope is located at point B, after the machining allowance is increased in the height direction of the corresponding part of the finished product and the maximum outer diameter, and the second slope forms a second angle θ2 with the horizontal direction; Step 5: Based on the forging shape designed in Steps 2 to 4, construct the final forging die cavity, and set a decompression ramp in the area corresponding to the forging rim on the outer edge of the die to replace the traditional bridge structure; the decompression ramp is composed of an inclined plane with a third angle θ3 to the vertical direction and a die opening height H3, and H3 and θ3 satisfy a negative correlation.

[0008] Secondly, the present invention provides a GH4169 alloy turbine disc forging, wherein the forging is designed and manufactured using the above-mentioned method for reducing the tonnage of die forging extra-large GH4169 alloy turbine discs.

[0009] The forging comprises, from the inside to the outside, the following components radially: The hub region has a conformally shaped forged profile. The spoke area is connected to the outer periphery of the hub area, and the upper and lower surfaces of the spoke area and the upper and lower surfaces of the hub area have a first height difference H1 and a second height difference H2, respectively. A rim region, which is connected to the outer periphery of the spoke region; The transition between the spoke area and the rim area has a flow control slope feature consisting of a first inclined plane and a second inclined plane. The first inclined plane forms a first angle θ1 with the vertical direction, and the second inclined plane forms a second angle θ2 with the horizontal direction. The geometric position of the first inclined plane and the second inclined plane is defined by the intersection point after adding machining allowance to the finished product size.

[0010] Preferably, the diameter of the GH4169 alloy turbine disc forging after precision machining is greater than or equal to 2 meters.

[0011] Compared with the prior art, the present invention has the following beneficial effects: (1) By using a three-stage non-uniform feed rate, a flow-controlled slope to guide the sequential filling of metal, and a pressure-reducing ramp to replace the high-resistance bridge section, the peak load of the die forging process is significantly reduced. Finite element simulation verification shows that the die forging tonnage of the GH4169 alloy extra-large turbine disc forging designed using the method of this invention is 805MN (approximately 80,529 tons), significantly lower than the forming tonnage of conventional design methods (simulated value > 850MN), successfully controlling the forming load within the 800MN equipment limit. This enables the one-time die forging of GH4169 alloy extra-large turbine disc forgings with a diameter of 2 meters or more on existing 800MN presses, filling a technological gap in the domestic manufacturing field of turbine disc forgings of this size.

[0012] (2) The formed forging has uniform metal flow and no defects such as folding or incomplete filling. After non-destructive testing and mechanical property testing, it meets the technical standard requirements of GH4169 alloy turbine disks. It is not only applicable to GH4169 alloy, but can also provide a reference for the die forging of ultra-large disk forgings of other difficult-to-deform alloys. Attached Figure Description

[0013] Figure 1 This is a rough-machined delivery diagram of the GH4169 alloy extra-large turbine disk in an embodiment of the present invention.

[0014] Figure 2 A schematic diagram of a forging structure based on conventional forging design methods (comparative example).

[0015] Figure 3 A schematic diagram of a mold structure for a conventional forging design method (comparative example).

[0016] Figure 4 This is a schematic diagram of the forging structure according to an embodiment of the present invention.

[0017] Figure 5 This is a schematic diagram of the mold structure according to an embodiment of the present invention.

[0018] Figure 6 This is a schematic diagram of the area division in step 1 of the present invention. The diagram shows the division and boundary positions of the hub area, the spoke area, and the rim area.

[0019] Figure 7 This is a schematic diagram of the hub area design in step 2 of the present invention.

[0020] Figure 8 This is a schematic diagram of the spoke area design in step 3 of the present invention, showing the positions of H1 and H2.

[0021] Figure 9 This is a schematic diagram of the construction of the metal flow control slope in step 4 of the present invention. The diagram shows the positions of the starting point A, the starting point B, the first included angle θ1, and the second included angle θ2.

[0022] Figure 10 This is a schematic diagram of the pressure relief ramp mold structure in step 5 of the present invention. The diagram shows the position of the third included angle θ3 and the mold opening height H3.

[0023] Figure 11 The image shows a photograph / simulation result of the final formed GH4169 alloy extra-large turbine disc forging in this embodiment of the invention. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0025] To clearly illustrate the technical solution of this invention, the terms used herein are defined as follows: The "hub region," "spoke region," and "rim region" described in this invention are classifications based on the radial geometric characteristics and functions of the turbine disc forging. For example... Figure 6 As shown, along the radial direction of the forging from the inside out (i.e. from...) Figure 6 (From left to right), in order: Hub area: This refers to the thicker, central part of the forging. This area is ultimately machined to form the hub structure of the turbine disc, primarily used for mounting the spindle and bearing assembly stress. Figure 6 In the embodiment shown, the hub area corresponds to a section with a relatively large thickness near the central axis of the forging.

[0026] Spoke area: This refers to the thin, plate-like transition section connecting the hub and the rim. This area is relatively thin, extends radially in a disc shape, and primarily serves a connecting and force-transmitting function. Figure 6 In the embodiment shown, the spoke region corresponds to the radial extension section where the thickness of the forging is drastically reduced but remains relatively thin.

[0027] Flange region: This refers to the outermost edge of the forging, where the thickness increases again. This region is ultimately machined to form the rim structure of the turbine disc, used to mount the blades. Figure 6 In the embodiment shown, the rim region corresponds to the outermost edge of the forging, where the thickness increases again.

[0028] The boundary between the hub area and the spoke area is located at the transition point where the thickness of the forging decreases sharply (e.g., Figure 6 (The location indicated by the middle arrow); the boundary between the spoke area and the rim area is located at the turning point where the thickness of the forging increases sharply (e.g., ...). Figure 6 (The location indicated by the other arrow in the middle).

[0029] For GH4169 alloy extra-large turbine disc forgings, those skilled in the art, in conjunction with... Figures 6 to 8 The cross-sectional shape of the forging shown clearly identifies the boundary positions of the three regions without requiring excessive labor.

[0030] Radial: refers to the direction perpendicular to the central axis of the forging.

[0031] Axial direction: refers to the direction parallel to the central axis of the forging, that is, the height direction of the forging.

[0032] Inner / Outer: With the center axis of the forging as a reference, inner refers to the direction closer to the center axis, and outer refers to the direction farther away from the center axis.

[0033] Height: Unless otherwise specified, it refers to the axial dimension of the forging or die.

[0034] Conformal allowance: This refers to the fact that the outline shape of the forging is basically consistent with the outline shape of the finished product, and the machining allowance is increased uniformly only on the basis of the finished product size.

[0035] Extra-large turbine discs refer to GH4169 alloy turbine disc forgings with a diameter ≥ 2 meters after precision machining. Prior to this invention, there was no successful experience in manufacturing GH4169 alloy turbine disc forgings of this size in China, which falls into the category of ultra-large forgings.

[0036] Example 1:

[0037] This embodiment provides a die forging method for extra-large turbine disk forgings made of GH4169 alloy, and the specific steps are as follows: Step 1: Based on the finished structure of a 300MW heavy-duty gas turbine disk of a certain model, the rough machining delivery drawing is as follows: Figure 1 As shown, the diameter after rough machining is 2140mm. The forging to be designed is divided radially from the inside to the outside into a hub area, a spoke area, and a rim area, as follows: Figure 6 As shown. The dividing point is determined according to the thickness inflection point.

[0038] Step 2: Perform conformal allowance design on the wheel hub area, with an allowance of 9mm on each side. Design a connecting skin at the inner diameter of the wheel hub, with a connecting skin thickness of 200mm. The outline of the forged wheel hub area is as follows. Figure 7 As shown.

[0039] Step 3: Perform a non-conformal design on the spoke area to create a first height difference H1 = 65mm between the upper surface of the spoke and the upper surface of the hub, and a second height difference H2 = 54mm between the lower surface of the spoke and the lower surface of the hub, satisfying H1 > H2. Figure 8 As shown.

[0040] Step 4: Construct a flow control slope at the transition between the spoke area and the rim area.

[0041] First, determine the starting point A: using the corresponding part of the finished product as a reference, increase the radial direction by 9mm and the height direction by 9mm. The intersection of the two increases is the starting point A.

[0042] Determine starting point B: Using the corresponding part of the finished product as a reference, the intersection of the point where the height is increased by 9mm and the maximum outer diameter is the starting point B.

[0043] Using starting point A as the base point, construct a first inclined plane with an angle of θ1 = 65° to the vertical direction; using starting point B as the base point, construct a second inclined plane with an angle of θ2 = 10° to the horizontal direction. The first and second inclined planes are connected by a transition fillet with a radius of R = 50 mm to form a complete flow-control slope structure, as shown below. Figure 9 As shown.

[0044] Step 5: Based on the forging shape designed in Steps 2-4, construct the final forging die cavity. In the area corresponding to the forging rim on the outer edge of the die, a pressure-reducing ramp is installed to replace the traditional bridge structure. Based on H3=235-1.2θ3, taking θ3=60°, we calculate H3=235-1.2×60=163mm. That is, the slope of the pressure-reducing ramp is at a 60° angle to the vertical direction, and the die opening height is 163mm. Figure 10 As shown.

[0045] Step 6: After the GH4169 alloy bar has been blanked, it is subjected to multiple blanking processes and then forged in one pass on an 800MN die forging press.

[0046] Using the above method, extra-large turbine disk forgings of GH4169 alloy were successfully formed on an 800MN die forging press. Finite element simulation verified that the peak load during the forming process was 805MN (approximately 80,529 tons). Figure 11 As shown, it is below the device limit.

[0047] The final forgings were inspected for quality: the forgings had smooth surfaces and were free of defects such as folds and cracks.

[0048] To verify the applicability of H3=235-1.2θ3, simulations were performed with θ3=40°, 50°, and 75° while keeping other parameters constant. The results are shown in Table 1.

[0049] Table 1 Example <![CDATA[Value of θ3]]> <![CDATA[Calculated value of H3]]> Simulated forming tonnage Forming quality Example 2 40° 187mm 795MN Fully filled and without defects Example 3 50° 175mm 800MN Fully filled and without defects Example 4 75° 145mm 818MN Fully filled, with a slight burr at the edges. The results show that within the range of θ3 ∈ [40°, 75°], the forming tonnage fluctuates around 800MN and does not exceed the equipment limit, verifying the effectiveness of H3 = 235 - 1.2θ3 within this parameter range. Among them, the forming tonnage is the lowest and the forming quality is the best in the range of θ3 = 55°~65°.

[0050] Comparative Example 1: Conventional Design Method

[0051] Using conventional forging design methods as a comparative example: the forging contour is designed to follow the shape completely, the draft angle is 5°, the mold is set with a traditional bridge structure, the bridge height is 35mm, and the other conditions (bill specifications, heating temperature, mold temperature, lubrication conditions, equipment) are exactly the same as in Example 1.

[0052] Finite element simulation showed that the peak forming load using conventional design methods was 872MN, exceeding the 800MN equipment limit, making it impossible to complete the forming process in actual production. Furthermore, incomplete filling defects appeared at the rim, rendering the forging unusable.

[0053] Comparative Example 2: Design omitting the flow control slope

[0054] To verify the necessity of the flow control slope, while keeping other parameters the same as in Example 1, only the flow control slope design in step 4 (i.e., the transition between the spokes and the rim is a conventional circular arc transition) was omitted, and simulation verification was performed.

[0055] The results show that the peak forming load is 842MN, which is slightly lower than the conventional design, but still exceeds the 800MN equipment limit, and a slight folding defect appears at the lower corner of the rim. This indicates that the synergistic effect of the flow control slope and the pressure relief slope is the key to achieving tonnage reduction.

[0056] The GH4169 alloy turbine disc forging and its die forging method provided by this invention have been successfully applied to the trial production of 300MW-class turbine disc forgings at a heavy-duty gas turbine manufacturing enterprise in China. The forgings exhibit precise dimensions, excellent microstructure and properties, and fully meet design requirements. This method can be widely applied to the die forging of similar ultra-large disc forgings, showing promising prospects for industrial application.

[0057] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for reducing the tonnage of forging extra-large GH4169 alloy turbine disks, characterized in that, Includes the following steps: Step 1: Based on the finished structure of the turbine disc, the forging is divided radially from the inside to the outside into the hub area for forming the disc hub, the spoke area connecting the hub and the rim, and the rim area located at the outermost edge. Step 2: Perform conformal scaling design on the hub area to determine the forging profile of the hub part; Step 3: Perform a non-conformal design on the spoke area so that the upper and lower surfaces of the spoke area and the upper and lower surfaces of the hub area determined in Step 2 form a first height difference H1 and a second height difference H2, respectively. Step 4: At the transition between the spoke area and the rim area, construct a metal flow control slope; the flow control slope includes a first slope and a second slope, the starting point of the first slope is located at point A, which is the intersection of the machining allowance along the radial and height directions of the corresponding part of the finished product, and the first slope forms a first angle θ1 with the vertical direction; the starting point of the second slope is located at point B, which is the intersection of the machining allowance along the height direction of the corresponding part of the finished product and the maximum outer diameter, and the second slope forms a second angle θ2 with the horizontal direction; Step 5: Based on the forging shape designed in Steps 2 to 4, construct the final forging die cavity, and set a decompression ramp in the area corresponding to the forging rim on the outer edge of the die to replace the traditional bridge structure; the decompression ramp is composed of an inclined plane with a third angle θ3 to the vertical direction and a die opening height H3, and H3 and θ3 satisfy a negative correlation.

2. The method for reducing the tonnage of forging extra-large GH4169 alloy turbine disks according to claim 1, characterized in that, In step 3, the value of the first height difference H1 ranges from 50mm to 80mm, and the value of the second height difference H2 ranges from 50mm to 58mm.

3. The die forging method for a GH4169 alloy turbine disc forging according to claim 1, characterized in that, In step 4, the first included angle θ1 ranges from 55° to 80°, and the second included angle θ2 ranges from 5° to 15°.

4. The method for reducing the tonnage of forging extra-large GH4169 alloy turbine disks according to claim 1, characterized in that, In step 4, the first inclined plane and the second inclined plane are connected by a transition fillet.

5. A method for reducing the tonnage of forging extra-large GH4169 alloy turbine discs according to claim 4, characterized in that, The radius of the transition fillet is 30mm to 80mm.

6. The method for reducing the tonnage of forging extra-large GH4169 alloy turbine disks according to claim 1, characterized in that, In step 5, the negative correlation between H3 and θ3 is satisfied: H3 = 235 - 1.2θ3, where the value of θ3 ranges from 40° to 75°.

7. A method for reducing the tonnage of forging extra-large GH4169 alloy turbine disks according to claim 6, characterized in that, The value of the third included angle θ3 is between 55° and 65°.

8. The method for reducing the tonnage of forging extra-large GH4169 alloy turbine disks according to claim 1, characterized in that, Its features are, The single-sided allowance for conformal allowance in step 2 is 8mm to 10mm.

9. A GH4169 alloy turbine disc forging, characterized in that, The forging is designed and manufactured using the method for reducing the tonnage of die forging extra-large GH4169 alloy turbine disks as described in any one of claims 1 to 8, and the forging comprises, from the inside to the outside, the following components in a radial direction: The hub region has a conformally shaped forged profile. The spoke area is connected to the outer periphery of the hub area, and the upper and lower surfaces of the spoke area and the upper and lower surfaces of the hub area have a first height difference H1 and a second height difference H2, respectively. A rim region, which is connected to the outer periphery of the spoke region; The transition between the spoke area and the rim area has a flow control slope feature consisting of a first inclined plane and a second inclined plane. The first inclined plane forms a first angle θ1 with the vertical direction, and the second inclined plane forms a second angle θ2 with the horizontal direction. The geometric position of the first inclined plane and the second inclined plane is defined by the intersection point after adding the machining allowance to the finished product size.

10. A GH4169 alloy turbine disc forging according to claim 9, characterized in that, The forging satisfies at least one of the following characteristics: The first height difference H1 is 50mm to 80mm, and the second height difference H2 is 50mm to 58mm; The first included angle θ1 is 55° to 80°, and the second included angle θ2 is 5° to 15°; The diameter of the forging after precision machining is greater than or equal to 2 meters.

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