Aircraft engine shield and manufacturing method thereof

Abstract

The invention belongs to the technical field of aircraft manufacturing, and discloses an aircraft engine shield and a manufacturing method thereof. Components made of thermoplastic composite materials are connected together through butt joints to form semicircular cover bodies, and the aircraft engine shield is formed after the two semicircular cover bodies are connected. The butt joint comprises a first component and a second component, the butt joint areas of the first component and the second component are each provided with a stepped structure, each stepped structure comprises a horizontal connecting area and two vertical connecting areas, the two vertical connecting areas are located on the two sides of the horizontal connecting area, and the horizontal connecting areas can be matched with a welding tool head of ultrasonic welding equipment. By adopting the scheme for preparing the aircraft engine shield, the manufacturing cost of the aircraft engine shield can be greatly reduced, the manufacturing difficulty of the aircraft engine shield can be remarkably reduced, the advantage of high manufacturing efficiency is achieved, and the mechanical property of the prepared aircraft engine shield meets the design and use requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft manufacturing, and particularly relates to an aircraft engine shroud and a manufacturing method thereof. Background Art

[0002] An aircraft engine is the core power system of the whole aircraft, and its performance directly determines the thrust efficiency, fuel economy and safety of the aircraft. With the increasing demands of the aviation industry for lightweight, high thrust-to-weight ratio and low emissions, engine design is gradually developing towards large bypass ratio and high rotational speed, and such designs put forward higher requirements for the strength, fatigue resistance and aerodynamic shape accuracy of the external structure of the engine. As an external protection structure of the engine, the engine shroud not only needs to withstand extreme working conditions such as foreign object impact and high-temperature gas erosion during flight, but also needs to maintain the integrity of the engine aerodynamic shape to reduce noise and resistance. Among them, the aircraft engine fan shroud, as a key shroud component at the front end of the engine, needs to directly bear the centrifugal force, aerodynamic load and external environmental impact generated by the high-speed rotation of the fan blades, and its structural reliability directly affects the engine operation safety and maintenance cost.

[0003] At present, the aircraft engine fan shroud generally adopts an integrated molding method of fiber-reinforced thermosetting composite material paving-curing, that is, a semi-circular shroud body is manufactured at one time by using the process of paving + compression molding, and then two semi-circular shroud bodies are connected to form an aircraft engine shroud. However, the thermosetting composite material cannot be remelted after curing, resulting in difficult waste recycling, which does not meet the environmental protection requirements of the sustainable development of the aviation industry. Carbon fiber reinforced thermoplastic composite material (CFRTP, hereinafter referred to as thermoplastic composite material / material) is gradually replacing thermosetting composite material due to its high specific strength, high specific stiffness, good impact toughness and recyclability, and has become one of the ideal materials for aircraft engine fan shrouds.

[0004] During the manufacturing process of the aircraft engine fan shroud, at present, it is necessary to rely on large autoclaves and large precision molds, which have high mold costs, equipment costs and energy consumption (the cost of a single set of molds is usually not less than 30,000 yuan, and the corresponding curing equipment is usually as high as several hundred thousand yuan), and large-sized components (the semi-circular shroud body of the aircraft engine shroud) are prone to problems such as uneven heating and incomplete exhaust during the curing process, resulting in defects such as holes, insufficient interlayer strength and resin enrichment areas, affecting the performance consistency of the finished product. Moreover, it is not convenient to carry out operations such as fiber laying and curing, and 3-4 people are required to cooperate. Summary of the Invention

[0005] At least to solve the technical problems mentioned in the background art, the purpose of the present invention is to provide an aircraft engine shroud and a manufacturing method thereof.

[0006] The present invention adopts the following technical solutions.

[0007] An aircraft engine shroud, which uses a butt joint to connect components made of thermoplastic composite materials together to form a semi-circular shroud, and the aircraft engine shroud is formed by connecting two semi-circular shrouds; wherein, the butt joint includes component one and component two, and stepped structures are arranged in the butt joint areas of component one and component two. The stepped structure includes a horizontal connection area and two vertical connection areas. The two vertical connection areas are located on both sides of the horizontal connection area, and the horizontal connection area can be adapted to the welding tool head of ultrasonic welding equipment.

[0008] In the present invention, the vertical and horizontal in the vertical connection area and the horizontal connection area are defined based on the flat placement of the workpiece to be connected. When the direction of the workpiece to be connected changes, the vertical and horizontal also change adaptively; the angular range of the vertical connection area is defined as the included angle between this connection area and the horizontal plane, and the included angle is 60-90°; after the butt joint is connected, the fronts of component one and component two are basically in the same plane, and the backs of component one and component two after docking are also basically in the same plane. The so-called front and back refer to the areas on the component surface that are no more than 10 mm away from the vertical connection area.

[0009] To further improve the connection strength of the aircraft engine shroud, a number of convex points arranged in an array are provided only in the horizontal connection area of one of the components (component one or component two); preferably, the size of the convex points does not exceed 0.5 mm, and the density of the convex points is evenly arranged 50-100 per square centimeter. Further, a protruding part is provided along the top edge of the slope of component one or component two, and the width of the protruding part is not greater than 2 mm. The protruding part is used as the material to fill the space where the heating element is located during the connection process. Adopting such a scheme can further improve the connection strength and quality of the aircraft engine shroud.

[0010] A manufacturing method of the aforementioned aircraft engine shroud, the steps include: Step 1, along the axial direction of the semi-circular shroud, the semi-circular shroud is designed and divided into at least two components, and each component is formed by a molding process. Step 2, connect the adjacent components in butt joint until the manufacture of the semi-circular shroud is completed. Step 3, connect the two semi-circular shrouds together to form an aircraft engine shroud.

[0011] Further, the step of connecting the adjacent components in butt joint includes: Step 21, butt joint component one and component two, and place a heating element between the vertical connection areas of component one and component two. The heating element is externally connected to a heating control system, and the thickness of the heating element does not exceed 0.6 mm to obtain the workpiece to be butt jointed. Step 22: Place the workpiece to be butt-jointed flat and fix it on the translational working platform. Then, use a lateral pressing tool to laterally press the workpiece to be butt-jointed, and use a limiting tool to vertically limit the workpiece to be butt-jointed. Step 23: Move the welding tool head of the ultrasonic welding equipment to the connection starting point, and set the process parameters (including welding parameters) and connection method (path). Step 24: Start the connection. During the connection process, control the translational working platform and the heating element to move at a constant speed according to the set speed, and control the welding tool head to perform intermittent spot welding (point connection) according to the set frequency. The heating element is always located in front of the connection point to preheat the vertical connection area. Step 25: After the connection is completed, remove the heating element, the welding tool head, and the limiting tool, and cool the workpiece. If necessary, the surface of the connection area also needs to be polished and reinforced by continuous fiber paving.

[0012] To further improve the connection strength of the aircraft engine shroud, during the connection process, always control the lateral pressing tool to keep the lateral pressing force of the workpiece to be butt-jointed constant.

[0013] As a preferred solution, the heating element is a metal sheet or several metal wires arranged at intervals.

[0014] To be able to implement the connection more smoothly, the way to move the heating element at a constant speed is to longitudinally or obliquely upward withdraw the heating element. Withdrawing the heating element means that the heating element and the workpiece move away from each other until the heating element completely leaves the workpiece.

[0015] As a preferred solution, when the thickness of the butt-joint area is greater than the set thickness value A (A = 7 mm), a strip-shaped groove is provided in the vertical connection area, and the heating element is several metal wires arranged at intervals, and the metal wires are fitted in the strip-shaped groove.

[0016] As a preferred solution, when the thickness of the butt-joint area is greater than the set thickness value B (B = 5 mm), the front and back of the workpiece to be butt-jointed are respectively connected according to steps 22 to 25.

[0017] To further improve the connection efficiency, the angle between the slope of the vertical connection area and the horizontal plane is preferably 70 - 85 degrees, and the effective working width of the welding tool head is not less than the width of the horizontal connection area.

[0018] As a preferred solution, when the thickness of the butt-joint area is greater than the set thickness value C (such as C = 12 mm), the stepped structure has two horizontal connection areas with different heights and three vertical connection areas.

[0019] Advantages: Using the solution of the present invention to prepare the aircraft engine shroud can not only reduce its manufacturing cost, but also significantly reduce its manufacturing difficulty. Only one person can complete the operation smoothly, and it also has the advantage of high manufacturing efficiency. The mechanical properties of the prepared aircraft engine shroud meet the design and use requirements; the present invention cleverly realizes the effective connection of the split components of the aircraft engine shroud, and can avoid the appearance of voids / holes in the connection area of the aircraft engine shroud; adopting the solution of the present invention can realize the continuous ultrasonic welding of the aircraft engine shroud, ensure the joint connection strength and uniformity, obtain good fatigue performance and better sealing performance, and reduce the joint deformation and residual stress in the connection area; adopting the solution of the present invention is also beneficial to ensuring the continuity of the fibers and the good quality of the joints; in addition, in the present invention, through the mutual cooperation of the two regional connection structures (ultrasonic horizontal connection area and hot melt vertical connection area), it is convenient for engineering application, and the connection structure has excellent mechanical properties. Description of the Drawings

[0020] Figure 1 Partial schematic diagram of the connection joint of the aircraft engine shroud in Example 1; Figure 2 Stereoscopic schematic diagram of the connection process of the connection joint of the aircraft engine shroud in Example 1; Figure 3 Lateral schematic diagram of the connection process of the connection joint of the aircraft engine shroud in Example 1; Figure 4 Stereoscopic schematic diagram of the connection process of the connection joint of the aircraft engine shroud in Example 2; Figure 5 Lateral schematic diagram of the connection process of the connection joint of the aircraft engine shroud in Example 2; Figure 6 Schematic diagram of the heating element in Example 2; Figure 7 Top-down schematic diagram of the connection process of the connection joint of the aircraft engine shroud in Example 3; Figure 8 Stereoscopic schematic diagram of the connection process of the connection joint of the aircraft engine shroud in Example 3; Figure 9 Partial schematic diagram of the connection joint of the aircraft engine shroud in Example 4; Figure 10 Schematic diagram of the manufacturing process of the aircraft engine shroud in Example 1. Detailed Description of the Invention

[0021] The technical solutions in the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Embodiment 1

[0022] Combined with Figures 1 to 3 As shown, an aircraft engine shroud uses docking joints to connect components made of thermoplastic composite materials together to form a semi-circular cover, and the aircraft engine shroud is formed by connecting two semi-circular covers; wherein, each docking joint includes component one 1 and component two 2, and stepped structures are provided in the docking areas of component one 1 and component two 2. The stepped structure includes a horizontal connection area 3 and two vertical connection areas 4. The two vertical connection areas 4 are located on both sides of the horizontal connection area 3, and the horizontal connection area 3 can adapt to the welding tool head 5 of ultrasonic welding equipment. In this embodiment, the widths of component one 1 and component two 2 are both 200 mm, the lengths are both 300 mm, the wall thicknesses of component one 1 and component two 2 are both 6 mm, the thickness (height) of the vertical connection area 4 is 3 mm, the width of the horizontal connection area 3 is 20 mm, the angle between the slope surface of the vertical connection area 4 and the horizontal plane is 90 degrees. A number of convex points 12 are arranged in an array in the horizontal connection area 3 of component two 2 (the size of the convex points does not exceed 0.5 mm, and the density of the convex points is evenly arranged 60 - 65 per square centimeter. The convex points 12 can be formed on the surface of the plate by laser etching or molding). After component one 1 and component two 2 are docked, the tips of the convex points 12 just abut against the surface of the horizontal connection area 3 of component one 1. In this embodiment, a protruding part 13 is provided at the top edge of the slope surface of component one 1 or component two 2. The width of the protruding part 13 is not greater than 2 mm, and the protruding part 13 serves as the material for filling the space where the heating element 9 is located during the connection process (the volume of the protruding part 13 is equal to the volume of all the heating elements 9 at a single vertical connection area 4).

[0023] A manufacturing method of the aircraft engine shroud in this embodiment, combined with Figure 10 As shown, the steps include: Step 1, along the axial direction of the semi-circular cover, the semi-circular cover is designed and divided into twelve components, and each component is formed by a molding process respectively; The molding process is a prior art. First, the CFRTP prepreg is laminated and laid on the surface of the mold, then a high-temperature release agent is sprayed on the surface of the mold, and then the mold is heated to above the melting point of the material and kept under pressure for a period of time to achieve the molding of the component; in other embodiments, the number of divisions of the semi-circular cover design is determined by those skilled in the art according to the specifications of the aircraft engine shroud; Step 2: Docking and connecting adjacent components until the manufacture of the semi-circular cover is completed, that is, connecting twelve components to form a semi-circular cover (a total of eleven connections need to be implemented); Step 3: Connect the two semi-circular covers together (usually by connecting the closed semi-circular covers to the engine pylon with metal hinges and configuring elastic latches) to form an aircraft engine shroud; In this method, the step of docking and connecting adjacent components includes: Step 21: Docking component one 1 and component two 2, and placing a heating element 9 between the vertical connection areas 4 of component one 1 and component two 2. The heating element 9 is externally connected to a heating control system, and the heating element 9 is also connected to a retractable clamping system (the retractable clamping system uses a lead screw mechanism driven by a servo motor) to obtain a workpiece to be docked; among them, the heating element 9 is composed of multiple independent copper sheets with a thickness of 0.5 mm, a length of 20 mm, and a height of 10 mm; The way of heating the heating element 9 in the present invention is a prior art. One optional way is to energize the heating element 9 and generate heat using its resistance, and another optional way is to select an electric heating sheet that meets the thickness requirements; Step 22: Place the obtained workpiece to be docked flat and fix it on a translational working platform 8. The translational working platform 8 is driven by a servo motor and is installed on a slide rail 10. Then, use a transverse pressing tool 11 to horizontally press the workpiece to be docked, so that the vertical connection areas 4 of component one 1 and component two 2 are closely attached, and then use a limiting tool to vertically limit the workpiece to be docked; It should be noted that the translational working platform 8 selected in the present invention (including but not limited to plate workbenches, arc workbenches, tubular workbenches) should be adjusted adaptively according to the shape and curvature of the components, as long as it can ensure the stable placement and pressing of the workpiece; Step 23: Move the welding tool head 5 of the ultrasonic welding equipment to the starting point of connection, and set the process parameters (the amplitude of the welding tool head 5 is 40 µm, the welding pressure is 0.15 MPa, and the welding speed (the moving speed of the translational working platform 8) is 15 mm / s); In this embodiment, the ratio of the amplitude transformer of the sonic welding equipment is 1:1.3, the maximum output amplitude is 100 µm, the nominal power capacity is 3600 W, the welding tool head 5 of the ultrasonic welding equipment is cylindrical, the diameter of the welding tool head 5 is 25 mm, and the spot welding frequency of the welding tool head 5 is determined by those skilled in the art according to the welding speed and the newly added area of each spot welding (for a cylindrical welding tool head, the newly added area of each spot welding is usually 1 / 2 of the single effective connection area of the welding tool head 5); Step 24, start connection. During the connection process, control the translational working platform 8 and the heating element 9 to move at a constant speed according to the set speed, control the welding tool head to perform intermittent spot welding according to the set frequency, and keep the heating element 9 always in front of the connection point to preheat the vertical connection area 4. The distance between the heating area of the heating element 9 and the welding tool head 5 is 20 mm. During the connection process, always control the transverse pressing tool 11 to keep the transverse pressing force on the workpieces to be butted constant. Among them, the method of moving the heating element 9 at a constant speed is to longitudinally withdraw the heating element 9. In this embodiment, ten heating elements 9 need to be arranged simultaneously in the vertical connection area 4 before welding. During the connection process, every time the welding tool head 5 moves forward a standard distance (20 mm), control the extraction clamping system to withdraw one heating element 9 upward (for example, as shown in Figure 2 : when the welding tool head 5 moves to the set position three, withdraw the heating element three 91; when the welding tool head 5 moves to the set position four, withdraw the heating element four 92; when the welding tool head 5 moves to the set position five, withdraw the heating element five 93; when the welding tool head 5 moves to the set position six, withdraw the heating element six 94). The functions of this operation method include: smoothly achieving stable connection of the vertical connection area 4, preventing the formation of concave / hole areas in the vertical connection area 4 during the connection process, and at the same time avoiding the heating element 9 getting stuck in the connection area. Step 25, after the connection is completed, remove the heating element 9, the welding tool head 5 and the limiting tool, and cool the workpiece (the cooling and solidification temperature reduction gradient is 10 °C / min, and the air humidity is controlled at 25%). Embodiment 2

[0024] An aircraft engine shroud, referring to Embodiment 1, the main difference from Embodiment 1 is that, as shown in Figures 4 to 6 , the wall thicknesses of both the component one 1 and the component two 2 are 8 mm, the thickness (height) of the vertical connection area 4 is 4 mm, the width of the horizontal connection area 3 is 25 mm, and a welding tool head size adapted to this width is selected. The angle between the slope of the vertical connection area 4 and the horizontal plane (angle e is shown in the figure) is 85 degrees. The heating element 9 includes a number of metal wires 6 arranged at intervals (nickel-chromium alloy wires with a diameter of 0.2 mm). During the connection process, the method of moving the heating element 9 at a constant speed is to obliquely withdraw the heating element 9 upward. In this embodiment, a number of metal wires 6 need to be arranged simultaneously in the vertical connection area 4 before welding connection. The main function of the extraction clamping system is to clamp or tension the fixed ends of the metal wires 6. During the connection process, partial extraction of the metal wires 6 is achieved as the workpiece moves with the translational working platform 8. Embodiment 3

[0025] An aircraft engine shroud, referring to Embodiment 1, the main difference from Embodiment 1 is that, as shown inFigure 7 and Figure 8 As shown, the wall thicknesses of component 1 and component 2 are both 12 mm. The thickness (height) of the vertical connection area 4 is 6 mm, and the width of the horizontal connection area 3 is 40 mm. A welding tool size adapted to this width is selected. The slope of the vertical connection area 4 forms an angle of 80 degrees with the horizontal plane. Ten equally spaced strip grooves 7 with a width and depth of 0.3 mm are provided in the vertical connection area 4. The heating element 9 includes a number of metal wires 6 (nichrome alloy wires with a diameter of 0.3 mm) arranged at intervals, and each metal wire 6 is fitted in a strip groove 7. During the connection process, the way to move the heating element 9 at a constant speed is to longitudinally withdraw the heating element 9. During the process of the workpiece moving with the translational working platform 8, the synchronous withdrawal of all the metal wires 6 is achieved. Example 4

[0026] An aircraft engine shroud, referring to Example 1, the main difference from Example 1 is that in combination with Figure 9 As shown, the stepped structure has two horizontal connection areas 3 with different heights and three vertical connection areas 4. The wall thicknesses of component 1 and component 2 are both 15 mm. The thickness (height) of a single vertical connection area 4 is 5 mm, and the width of a single horizontal connection area 3 is 45 mm. A welding tool size adapted to this width is selected. The slope of the vertical connection area 4 forms an angle of 75 degrees with the horizontal plane. Eight equally spaced strip grooves 7 with a width and depth of 0.5 mm are provided in the vertical connection area 4. The heating element 9 includes a number of metal wires 6 (nichrome alloy wires with a diameter of 0.5 mm) arranged at intervals, and each metal wire 6 is fitted in a strip groove 7. During the connection process, the way to move the heating element 9 at a constant speed is to longitudinally withdraw the heating element 9. During the process of the workpiece moving with the translational working platform 8, the synchronous withdrawal of all the metal wires 6 is achieved.

[0027] The mechanical properties of the connection areas of the aircraft engine shrouds obtained in the examples were detected (substantially the tensile strength of the butt joint connection areas). The test results: the tensile strength of the butt joint connection area obtained in Example 1 was 50.5 Mpa, the tensile strength of the butt joint connection area obtained in Example 2 was 54.6 Mpa, the tensile strength of the butt joint connection area obtained in Example 3 was 53.2 Mpa, and the tensile strength of the butt joint connection area obtained in Example 4 was 58.5 Mpa. The mechanical properties of the workpieces obtained in each example all met the design and usage requirements.

[0028] The key technical points in the present invention include: arranging a detachable extremely thin small heating element 9 in the vertical connection area 4 of component 1 and component 2, and jointly forming a specific docking joint with the horizontal connection area 3, and then through the combined cooperation of ultrasonic welding and hot melt connection, effectively realizing the connection of the docking joint of the components of the aircraft engine shroud; during the connection process, the positions of component 1 and component 2 do not change, and the heating element 9 can be smoothly withdrawn. Through the action of the welding tool head 5, the ultrasonic welding of the horizontal connection area 3, the hot melt connection of the vertical connection area 4, the filling of the space where the heating element 9 is located, and the melting and elimination of the protruding part 13 (that is, the protruding part 13 melts and disappears, and this part of the material is pressed into the space where the heating element 9 is withdrawn) are synchronously realized. Especially when the included angle between the slope of the vertical connection area 4 and the horizontal plane is 75 - 85 degrees, the filling of the space where the heating element 9 is located and the melting and elimination effect of the protruding part 13 are relatively the best. The key is that it can effectively prevent the lateral, longitudinal, and vertical deformation of the workpiece, and the workpiece does not bend and deform when there is no limiting tool arranged in the longitudinal direction.

[0029] In the solution of Embodiment 1, only small molds, small autoclaves, and ultrasonic connection equipment are required for the main equipment. The cost reduction of the required molds and autoclaves can reach more than 50%, and the overall cost is also greatly reduced. The key is that the difficulty of manufacturing the engine shroud is very low, and only one technician can smoothly operate it, saving many cumbersome processes of integrally curing the semi-circular cover.

[0030] Using the solution of the present invention to prepare the aircraft engine shroud can not only greatly reduce its manufacturing cost, but also significantly reduce its manufacturing difficulty. Only one person can smoothly complete the operation, and it also has the advantage of high manufacturing efficiency. The mechanical properties of the prepared aircraft engine shroud meet the design and use requirements; the present invention cleverly realizes the effective connection of the split components of the aircraft engine shroud, and can avoid the appearance of cavities / holes in the connection area of the aircraft engine shroud; using the solution of the present invention can realize the continuous ultrasonic welding of the aircraft engine shroud, ensure the connection strength and uniformity of the joint, obtain good fatigue performance, better sealing performance, reduce the joint deformation and the residual stress in the connection area; using the solution of the present invention is also beneficial to ensuring the continuity of the fiber and having good joint quality; in addition, in the present invention, through the mutual cooperation of the two-region connection structure (ultrasonic horizontal connection area and hot melt vertical connection area), it is convenient for engineering application, and the connection structure has excellent mechanical properties.

Claims

1. An aircraft engine shroud, characterized in that: Adopt a butt joint to connect components made of thermoplastic composite materials together and form a semi-circular cover, and the aircraft engine shroud is formed by connecting two semi-circular covers; wherein, the butt joint includes component one (1) and component two (2), and stepped structures are arranged in the butt joint areas of component one (1) and component two (2), and the stepped structure includes a horizontal connection area (3) and two vertical connection areas (4), and the two vertical connection areas (4) are located on both sides of the horizontal connection area (3).

2. The aircraft engine shroud according to claim 1, wherein: A number of convex points (12) arranged in an array are only provided in the horizontal connection area (3) of one of the components. After component one (1) and component two (2) are butted, the convex points (12) are abutted against the surface of the horizontal connection area (3) of the other component.

3. A manufacturing method of the aircraft engine shroud according to claim 1 or 2, characterized in that the steps Including: Step 1, along the axial direction of the semi-circular cover, design and divide the semi-circular cover into at least two components, and form each component by a molding process respectively. Step 2, butt-connect adjacent components until the manufacturing of the semi-circular cover is completed. Step 3, connect two semi-circular covers together to form an aircraft engine shroud.

4. The manufacturing method according to claim 3, characterized in that, The step of butt-connecting adjacent components includes: Step 21, butt-connect component one (1) and component two (2), and place a heating element (9) between the vertical connection areas (4) of component one (1) and component two (2). The heating element (9) is externally connected to a heating control system, and the thickness of the heating element (9) is not greater than 0.6 mm to obtain a workpiece to be butted. Step 22, lay the obtained workpiece to be butted flat and fix it on a translational working platform (8), then use a transverse pressing tool (11) to transversely press the workpiece to be butted, and then use a limiting tool to vertically limit the workpiece to be butted. Step 23, move the welding tool head (5) of the ultrasonic welding equipment to the connection starting point and set the process parameters. Step 24, start the connection. During the connection process, control the translational working platform (8) and the heating element (9) to move at a set speed uniformly, and the heating element (9) is always in front of the connection point to realize preheating of the vertical connection area (4). Step 25, after the connection is completed, remove the heating element (9), the welding tool head (5) and the limiting tool, and cool the workpiece.

5. The manufacturing method according to claim 4, characterized in that: During the connection process, always control the transverse pressing tool (11) to keep the transverse pressing force of the workpiece to be butted constant.

6. The manufacturing method according to claim 4, characterized in that: The heating element (9) is a metal sheet or has a number of metal wires (6) arranged at intervals.

7. The manufacturing method according to claim 4, characterized in that: The method of moving the heating element (9) uniformly is to longitudinally or obliquely upward withdraw the heating element (9).

8. The manufacturing method according to claim 4, characterized in that: The included angle between the slope surface of the vertical connection area (4) and the horizontal plane is 70-85 degrees, and the effective working width of the welding tool head (5) is not less than the width of the butt joint area.

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