Design method of large complex three-dimensional multi-mold surface forging

Abstract

The application provides a design method of a large complex three-dimensional multi-parting surface forged piece, which comprises the following steps: 1, forging piece design; S1, parting surface design: parting surface 1 and parting surface 2 are divided according to the shape of the forging piece; S2, forging piece allowance design: the single-side allowance of the forging piece is designed to be 5-30 mm; S3, draft angle design: the same small draft angle design or variable draft angle design is adopted on the vertical edge of the forging piece; S4, transition fillet design: the concave fillet radius on the forging piece is 0.5-3 of the height of the vertical edge; forming process; K1, blank making: the metal on both sides of the parting surface 1 of the forging piece is pressed through a head forming tool A; K2, pre-forging: the metal on both sides of the parting surface 1 is pressed by a press through a pre-forging die; K3, finish forging: the metal on both sides of the parting surface 2 is pressed by a press through a finish forging die. By increasing the number of parting surfaces, the thick section size of the forging piece is reduced, the backward extrusion forming is changed into upsetting forming, and the feasibility of the forging process is improved.

Description

Technical Field

[0001] This invention relates to the field of die forging technology, and in particular to a design method for large, complex, three-dimensional multi-part forgings. Background Technology

[0002] With the increasingly severe security situation surrounding the country, aviation equipment is undergoing rapid upgrades, leading to a stronger demand for aircraft with higher speeds, lighter weights, longer ranges, higher reliability, and longer lifespans. To meet these iterative upgrades, comprehensive optimization of the aircraft's internal structure and component shapes is essential. Advances in fundamental theories, numerical simulations, and emerging technologies have broadened the design perspectives of aircraft structural designers, moving beyond conventional structures. Through continuous innovation and transformation, new and complex structures have been designed, solving problems such as the reliance on 3D printing for manufacturing and the insufficient fatigue life of 3D-printed parts. These new structures are better suited for optimizing aircraft force transmission and structure. Large integral structural components possess continuous force transmission, improving structural strength, stiffness, and fatigue life, while avoiding deformation caused by post-weld processing and shortening the manufacturing cycle. By eliminating numerous rivets, screws, and other fasteners, large integral structural components significantly reduce weight, decrease the number of aircraft parts and tooling requirements, simplify interchangeability, and greatly reduce assembly difficulty.

[0003] After proposing a novel design scheme for large integral parts, the issue of engineering implementation still needs to be considered. Currently, the moving crossbeam of large die forging presses with a capacity of 40,000 tons or more in China can only move vertically up and down, providing downward forming pressure to drive the metal to flow from the center to the periphery. There is currently no large multi-directional die forging press that can simultaneously provide forming forces in both the horizontal and vertical directions. This results in limitations on the geometric design of large aerospace parts, meaning that there are significant differences between the length, width, and thickness dimensions of the parts. Usually, there is only one maximum projection surface, and the parting surface is unique. If the forging has features such as high bulges, branches, and ribs that are perpendicular to the parting surface, the metal flow can be guided by using transition fillets, conformal parting, and process materials. It can also be formed by reverse extrusion without affecting the uniqueness of the parting surface. Generally speaking, if the width-to-height ratio of the ribs is greater than 3.5, the forming difficulty of the forging increases. If the width-to-height ratio is greater than 5, it cannot be formed by reverse extrusion.

[0004] The integration inevitably leads to a larger outer dimension of the forgings. Not only does the forming tonnage far exceed 40,000 tons, but the dimensional differences of some forgings in the three dimensions gradually decrease, and the maximum projected cross section does not exist. In the traditional design approach, if the fillet size and process coating are increased indiscriminately, not only will materials be wasted, but the performance of the thick cross section will also be difficult to guarantee. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a design method for large, complex, three-dimensional multi-parting forgings. By increasing the number of parting surfaces, the thickness and cross-sectional dimensions of the forging are reduced, and the reverse extrusion forming is transformed into upsetting forming, the feasibility of the forging process is improved.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A design method for large, complex, three-dimensional multi-part forgings includes the following steps:

[0008] I. Forging Design

[0009] S1. Parting surface design: Parting surface 1 and parting surface 2 are divided according to the shape of the forging. Parting surface 1 and parting surface 2 intersect and are perpendicular to each other.

[0010] S2. Forging allowance design: Based on the size of the forging parts, the single-sided allowance of the forging is designed to be 5-30mm.

[0011] S3. Draft Angle Design: The vertical edges of the forging adopt the same small draft angle design or the variable draft angle design. The same small draft angle design extends from the root along the stepped arrangement, and the angle design is 1 to 10°. The variable draft angle design gradually increases from the top of the rib to the root, and the angle design is 1 to 10°.

[0012] S4. Transition fillet design: The radius of the concave fillet on the forging is 0.5-3 times the height of the vertical side, and the radius of the convex fillet is equal to the single-side allowance at that position.

[0013] II. Molding Process

[0014] K1. Billet making: First, the forging material is placed in the heating furnace for preheating. Then, the preheated forging is placed on a one-way high-speed forging machine for upsetting. The metal at the head is gathered. The metal on both sides of the parting surface 1 of the forging is pressed by the head forming tool A. Then, the forging is taken out and put back into the furnace for heat preservation for 30-120 minutes. Then, the metal on both sides of the parting surface 2 of the forging is pressed by the head forming tool B. After forging, it is placed on a special material rack for cooling to form a billet. The underpressure is controlled at 5-10mm.

[0015] K2, Pre-forging: Lubricant is evenly sprayed on the surface of the billet, the billet is placed in a heating furnace for preheating, the pre-forging die is connected to the press, and lubricant is sprayed in the cavity of the pre-forging die. Then the heated billet is placed in the cavity of the die, and the press presses the metal on both sides of the parting surface 1 through the pre-forging die.

[0016] K3. Final forging: Uniformly spray lubricant on the surface of the blank, then place it in a heating furnace for preheating. Connect the final forging die to the press, and spray lubricating medium in the cavity of the final forging die. Then place the preheated blank in the die cavity, and the press presses the metal on both sides of the parting surface 2 through the final forging die. After forming, it is cooled on a special cooling rack.

[0017] In step S1, the outer shape of the forging is a three-dimensional structure, the projection in the side direction is a "cross" - shaped structure, and the projection in the upper direction is a "day" - shaped structure. The forging is designed with parting surface 1 and parting surface 2 in two spatial dimensions respectively.

[0018] In step S2, the size of the forging part specification is ≥1200×1200×1000mm, and the projected area of the forging is greater than 1.2㎡.

[0019] In step S3, the same small draft angle is a gradient draft with at least two steps designed, and the height drop between the steps is evenly divided; the variable draft angle is at least two kinds of draft angles designed, and the hypotenuse connection points are equally divided according to the width.

[0020] The beneficial effects of the present invention are:

[0021] 1. It provides a new idea for forming forgings with a multi - parting surface structure by a unidirectional large - scale die forging press, which can avoid enterprises from investing in new equipment such as multi - directional large - scale die forging presses again, reduce production costs, improve equipment utilization efficiency, strongly support the production of new complex large - scale integral structure forgings, and contribute to improving the performance of aircraft.

[0022] 2. By increasing the number of parting surfaces, reducing the size of the thick and large cross - section of the forging, and changing the backward extrusion forming into upsetting forming, the feasibility of the forging process is improved. Brief Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the size of the forging;

[0024] Figure 2 It is a schematic diagram of the design of the parting surface;

[0025] Figure 3 It is a schematic diagram of the allowance of the forging;

[0026] Figure 4 It is a schematic diagram of the design of the draft angle;

[0027] Figure 5 It is a schematic diagram of the design of the fillet of the forging;

[0028] Figure 6 It is a schematic diagram of the metal forming on both sides of parting surface 1;

[0029] Figure 7This is a schematic diagram of the metal forming on both sides of the parting surface 2;

[0030] Figure 8 This is a schematic diagram of the cooling process. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] Example 1

[0033] A design method for large, complex, three-dimensional multi-part forgings includes the following steps:

[0034] I. Forging Design (e.g.) Figures 1 to 5 (As shown)

[0035] S1. Parting Surface Design: Based on the shape of the forging, parting surface 1 and parting surface 2 are divided. Parting surface 1 and parting surface 2 intersect and are perpendicular to each other. This type of forging has no maximum projection surface. The spatial dimensions of the forging are approximately 1200mm×1200mm×1000mm or more. The ratio of the projected area of ​​the vertical length to the width is close to 1. After finding two or more larger projection surfaces with the same area based on the shape characteristics of the part, the design principle to be followed is that one of the parting surfaces is perpendicular to the mold base to ensure that the forging material is minimized.

[0036] S2. Forging allowance design: Based on the size of the forging parts, the single-sided allowance of the forging is designed to be 5-30mm. The allowance of the web plate on the single parting surface can be selected according to the smaller value, and the difficult-to-fill part can be selected according to the larger value.

[0037] S3. Draft Angle Design: The vertical edges of the forging shall adopt either a uniform small draft angle design or a variable draft angle design. The uniform small draft angle design extends towards the root along the stepped arrangement, with an angle of 1 to 10°. The variable draft angle design gradually increases from the top of the rib to the root, with an angle of 1 to 10°. Both the uniform small draft angle design and the variable draft angle design shall ensure a smooth transition to reduce metal flow resistance. The gradient draft angle shall have at least two steps with an evenly distributed height difference. The variable draft angle design shall have at least two types of draft angles, with the inclined edge connection points evenly divided according to the width.

[0038] S4. Transition fillet design: The radius of the concave fillet on the forging is 0.5-3 times the height of the vertical side, and the radius of the convex fillet is equal to the single-side allowance at that position.

[0039] II. Molding process (e.g.) Figures 6 to 8 (As shown)

[0040] K1. Billet Preparation: The billet preparation process is completed on a one-way high-speed forging mill. First, the forging material is placed in a heating furnace for preheating (the preheating temperature varies depending on the metal material; for titanium alloy forgings, the preheating temperature is 800–985℃). Then, the preheated forging is placed on the one-way high-speed forging mill for upsetting, accumulating the head metal. The metal on both sides of the parting surface 1 of the forging is pressed by the head forming fixture A. Then, the forging is removed and returned to the furnace for holding for 30–120 minutes. Finally, the metal on both sides of the parting surface 2 of the forging is pressed by the head forming fixture B. After forging, the metal is placed on a special rack for cooling to form a billet. The underpressure is controlled at 5-10mm. The specific number of forging passes should be reasonably allocated according to the actual material's deformation requirements. Steel forgings require fewer passes, while titanium alloy forgings can be processed in multiple passes. The tooling cavity needs to be sprayed with a lubricating medium. The billet-making process is characterized by using a unidirectional high-speed forging machine and billet-making tooling to press the two parting surfaces of a forging, initially distributing the metal, and using a special rack for cooling to avoid deformation during the cooling process.

[0041] K2. Pre-forging: The pre-forging process is carried out on a unidirectional large-scale die forging press. A lubricant (glass powder lubricant) is evenly sprayed onto the surface of the billet. The billet is placed in a heating furnace for preheating (preheating temperature 800-985℃). The pre-forging die is connected to the press, and a lubricating medium (graphite lubricant) is sprayed into the die cavity. The heated billet is then placed in the die cavity, and the press presses the metal on both sides of the parting surface 1 through the pre-forging die. Care must be taken to control under-pressure to prevent the forging from extruding burrs. The forging must then be immediately returned to the furnace. If burrs are extruded, it must be placed on a special cooling rack to cool before removing the burrs and reheating. The characteristic of the process described in step two is that it utilizes a unidirectional large-scale die forging press and die pressing to simplify a multi-parting surface forging into a single-parting surface for pressing within one heat cycle.

[0042] K3. Final Forging: The final forging process is carried out on a unidirectional large die forging press. The surface of the billet is evenly sprayed with lubricant and then placed in a heating furnace for preheating (preheating temperature is 800-985℃). The final forging die is connected to the press, and lubricating medium is sprayed into the cavity of the final forging die. Then, the heated billet is placed in the die cavity, and the press presses the metal on both sides of the parting surface 2 through the final forging die. After forming, it is cooled on a special cooling rack.

[0043] If commercially available forging designs and forming processes are not adopted, firstly, this type of cross-shaped forging requires the investment of a large multi-directional die forging press, increasing equipment costs; secondly, if no new equipment is invested, a large amount of material can only be applied to reduce the height-to-diameter ratio, which will lead to material waste, and the performance of the thick section is lower than that of the thin section, as shown in Table 1.

[0044] Ti-55531 1192MPa 1213MPa TA15 987MPa 1024MPa

[0045] Table 1

[0046] In step S1, the outer shape of the forging is a three-dimensional structure. The projection in the side direction is a "cross" structure, and the projection in the upward direction is a "day" structure. The forging is designed with parting surfaces 1 and 2 in two spatial dimensions respectively.

[0047] In step S2, the size of the forging part specification is ≥1200×1200×1000mm, and the projected area of the forging is greater than 1.2㎡.

[0048] In step S3, the same small draft angle is a gradient draft with at least two steps designed, and the height difference between the steps is evenly divided; the variable draft angle is at least two slopes designed, and the hypotenuse connection points are equally divided according to the width.

[0049] The advantage of designing two steps is to reduce the flash and save raw materials; for such a cross-shaped three-dimensional forging, if a single draft angle is designed according to the conventional method, a large amount of flash will accumulate at the root; thus resulting in waste of raw materials, an increase in the cross-section, and affecting the final performance of the forging.

[0050] Example 2

[0051] 1. Design the positions of the double parting surfaces according to the part shape in step one, then design the forging allowance, then design the forging draft angle, and finally design the forging fillet.

[0052] 2. Design the pre-forging and the blank billet in sequence according to the cross-sectional dimensions of the forging, and design the tooling A and the pre-forging die according to the structures on both sides of the parting surface 1, design the tooling B and the final forging die according to the structures on both sides of the parting surface 2, and design the diameter of the upsetting cylinder inner hole according to the bar size.

[0053] 3. After assembling the upsetting tooling, spray the mold release agent on the inner cavity surface of the tooling, then put the bar into it for upsetting. Immediately draw out the bar after upsetting, and then heat it in the furnace.

[0054] 4. Spray the graphite lubricant in the tooling A, then put the heated blank into the tooling A, press the metal on both sides of the parting surface 1, and then immediately heat it in the furnace.

[0055] 5. Spray the graphite lubricant in the tooling B, then put the heated blank into the tooling B, press the metal on both sides of the parting surface 2, and then cool it using a special material rack.

[0056] 6. Uniformly spray the lubricating medium on the surface of the blank obtained in step 5, then place it in the heating furnace for preheating, then connect the pre-forging die and the press, and spray the lubricating medium in the die cavity. Then place the heated blank in the die cavity to press the metal on both sides of the parting surface 1, and choose to heat it in the furnace or cool it according to the flash situation.

[0057] 7. Spray lubricating medium evenly on the surface of the billet obtained in step 6, then place it in a heating furnace for preheating, then connect the final forging die and the press, and spray lubricating medium in the die cavity. Then place the heated billet in the die cavity to press the metal on both sides of the parting surface 2. After forming, cool it on a special cooling rack.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A design method for large, complex, three-dimensional multi-parting forgings, characterized in that: It includes the following steps: I. Forging design S1. Parting surface design: Divide the parting surfaces 1 and 2 according to the shape of the forging. The parting surfaces 1 and 2 intersect and are perpendicular to each other; S2. Forging allowance design: According to the size of the forging part specifications, the unilateral allowance of the forging is designed to be 5 - 30 mm; S3. Draft angle design: Adopt the same small draft angle design or variable draft angle design for the vertical edges on the forging. The same small draft angle design extends towards the root along the stepped arrangement, and the draft angle is designed to be 1 - 10°; The variable draft angle design gradually increases from the rib top to the root, and the draft angle is designed to be 1 - 10°; S4. Transition fillet design: The concave fillet radius on the forging is 0.5 - 3 times the height of the vertical edge, and the convex fillet radius is equal to the unilateral allowance at that position; II. Forming process K1. Blank making: First, put the forging incoming material into the heating furnace for preheating, then put the preheated forging on the single - action upsetting press for upsetting to gather the metal at the head. Press the metal on both sides of the parting surface 1 of the forging through the head forming tooling A, then take out the forging and put it back into the furnace for heat preservation for 30 - 120 minutes, and then press the metal on both sides of the parting surface 2 of the forging through the head forming tooling B. After forging, place it on the special material rack for cooling to form a blank, and control the under - pressure to be 5 - 10 mm; K2. Pre - forging: Uniformly spray lubricant on the surface of the blank, put the blank into the heating furnace for preheating, connect the pre - forging die to the press, and spray lubricating medium in the cavity of the pre - forging die. Then put the heated blank into the die cavity, and the press presses the metal on both sides of the parting surface 1 through the pre - forging die; K3. Final forging: Uniformly spray lubricant on the surface of the blank, then place it in the heating furnace for preheating, connect the final forging die to the press, and spray lubricating medium in the cavity of the final forging die. Then put the heated blank into the die cavity, and the press presses the metal on both sides of the parting surface 2 through the final forging die. After forming, cool it on the special cooling material rack.

2. The design method for a large, complex, three-dimensional multi-part forging as described in claim 1, characterized in that: In step S1, the shape of the forging is a three - dimensional structure, the projection in the side direction is a "cross" - shaped structure, and the projection in the upper direction is a "day" - shaped structure. The parting surfaces 1 and 2 are designed in two spatial dimensions respectively for the forging.

3. The design method for a large, complex, three-dimensional multi-part forging as described in claim 1, characterized in that: In step S2, the size of the forging part specifications is ≥1200×1200×1000 mm.

4. The design method for a large, complex, three-dimensional multi-part forging as described in claim 1, characterized in that: In step S3, the same small draft angle is a gradient draft with at least two steps designed, and the height drop between the steps is evenly divided; The variable draft angle is designed with at least two draft angles, and the hypotenuse connection points are equally divided according to the width.

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