A design method for casting pouring system of large wall panel components

Abstract

This invention belongs to the field of aluminum alloy casting technology and relates to a design method for a gating system for casting large wall panel components. Firstly, the filling process of the molten metal is driven not only by the pressure in the low-pressure casting machine but also by gravity, enhancing the filling capacity of the molten metal in thin-walled structures and facilitating the complete forming of these structures. Secondly, it prevents the large horizontal sprue from forming a complete whole during casting, significantly reducing the unevenness of residual stress and minimizing deformation. Finally, it simplifies the structure of the gating system, simplifying molding and assembly, eliminating the need for mold flipping, reducing workload, and ensuring core stability.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy casting technology and relates to a gating system design method for casting large wall panel components. Technical Background

[0002] Large panel castings include aircraft landing gear guards, aircraft fuselage boarding doors, cargo doors, and various flat frame structures. Currently, the main manufacturing method for aerospace panel components involves assembling machined aluminum alloy parts with sheet metal parts using riveting and screw connections. This process is complex, has a long production cycle, and is costly. For components with large profiles, this method produces components with poor rigidity. Typical structural forms of panel components include... Figure 1 As shown, in recent years, with the development of aluminum alloy casting technology, wall panels can be manufactured using a technical route of first casting a blank as a whole and then machining it. When castings are used, their structural characteristics are as follows:

[0003] 1) The outer surface (aerodynamic surface) is a smooth curved surface, such as... Figure 1 As shown in b2; the blank thickness is 12-15mm, and the processed thickness is generally 2.5mm. The inner surface is distributed with cross-reinforcing ribs with a height of 50-60mm and a thickness of 1.5-2.5mm, such as... Figure 1 As shown in Figure 1 of section a.

[0004] 2) Along the length of the wall, there are two protruding lugs on one side, which are used to open and close the wall panel after the hinge is installed. On the other side, there are 2 to 3 thick bosses for installing the locking mechanism.

[0005] 3) The length varies from 1000mm to 2300mm, and the width varies from 600mm to 800mm.

[0006] As it is a combination of machining and sheet metal work, the casting requires high metallurgical quality and physical properties, and is produced using a precision resin sand casting process.

[0007] To ensure complete casting and achieve excellent metallurgical quality and mechanical properties, conventional casting processes employ a side-standing pouring posture, such as... Figure 2 As shown, the slit gating system is distributed on the outer surface and reinforcing ribs of the casting, with the vertical cylinder of the gating system situated on the cross passage of the bottom-pouring gating system. However, while this gating system ensures complete outer surface forming and achieves good metallurgical quality, the inner reinforcing ribs are difficult to form completely, requiring welding repair of any under-pouring areas to restore the shape. Furthermore, this gating system design also has the following problems:

[0008] First, the sand mold assembly process is labor-intensive. During assembly, the main sand mold is placed horizontally, and the core that forms the reinforcing ribs on the reverse side of the casting is placed horizontally in the main sand mold. After being fixed, the whole thing is rotated 90° and placed on the bottom mold of the horizontal runner. The core is prone to loosening during the rotation process, resulting in uneven wall thickness.

[0009] Secondly, after cutting and cleaning, the castings will have large deformations (5-10mm). These deformations need to be corrected during the heat treatment stage to meet the design requirements. The correction work is extensive and labor-intensive. Even after correction, some castings still cannot meet the design requirements and are scrapped. Summary of the Invention

[0010] To address the problems existing in the conventional gating system design for wall panel castings, this invention proposes a novel gating system design method. The aim is to produce hatch castings with complete shape, qualified metallurgical quality and mechanical properties by using this gating system in conjunction with resin sand casting, and to greatly reduce casting deformation.

[0011] The technical solution of this invention:

[0012] A method for designing a casting gating system for large wall panel components includes the following steps:

[0013] 1) The casting is poured horizontally with the aerodynamic surface facing upwards and the reinforcing rib facing downwards;

[0014] 2) A slit gating system is set on the outer side of the aerodynamic surface. The gating system is distributed along the length of the casting with a spacing of 250-300 mm.

[0015] 3) Since the cross-sectional shape of the casting along the width direction is an upward convex arc, the slit gating system is also designed to follow the arc shape. However, at the top of the upward convex arc, the slit gating system is separated with a separation interval of 30-40mm. The gating system beyond the two sides of the casting only retains the vertical cylinder structure, which bends downward 40-60mm beyond the edge of the casting, perpendicular to the horizontal plane. The end of the downward bend of the vertical cylinder extends 80-100mm beyond the lowest point of the casting.

[0016] 4) The bent vertical tube is connected to the side horizontal runners on both sides. The side horizontal runners are disconnected in the middle. If they interfere with the vertical tube, they are disconnected at a position close to the middle. The two side horizontal runners are then connected together by a main horizontal runner. The gate for low-pressure casting is located below the main horizontal runner.

[0017] The slotted gating system is located on the outer surface and is situated directly above or near the reinforcing ribs.

[0018] Each slotted gating system has 3 to 4 vent holes with a diameter of Φ3 to 5 mm at the top of the gating system.

[0019] Both the side runner and the main runner have square cross-sectional shapes.

[0020] The slotted gating system consists of a vertical cylinder and a slot, with the slot width δ being 1.5 to 2 times the thickness w of the aerodynamic surface of the casting, and the vertical cylinder diameter D being 3 to 4 times the slot width δ.

[0021] Both ends of the side horizontal runners should extend 100-150mm beyond the center of the vertical cylinder. The side length l of the side horizontal runner cross section is 1.1-1.3 times the diameter of the vertical cylinder. The side length 2 of the main horizontal runner is 1.5-1.8 times the diameter of the vertical cylinder, and its length is the distance between the outer sides of the two upper horizontal runners. The gate diameter d is the side length l of the main horizontal runner. 主 0.6 to 0.8 times the size, with a height of 80 to 100 mm.

[0022] The inner surface of the main horizontal gating channel is coated with thermal insulation material or a 3mm thick aluminum silicate fiber felt is pasted on the surface and then baked and dried.

[0023] The casting method of the gating system.

[0024] 1) For wall plate castings, there are 2 or 3 pouring gates. During pouring, the pouring gates need to be directly aligned with the riser pipe on the low-pressure pouring machine.

[0025] 2) The mold must be preheated. The mold temperature should not be lower than 60℃ during pouring and should not exceed 150℃. The temperature should be determined according to the size and wall thickness of the casting. The larger the casting and the smaller the wall thickness, the higher the mold temperature should be, and vice versa.

[0026] 3) During low-pressure casting, thermocouples are installed on the main runner to measure the temperature changes of the molten metal. Figure 10 As shown, when the temperature of the molten metal drops to 20-25°C above the solidification line of the alloy, the pressure holding is stopped, and the molten metal that has not solidified in the main horizontal runner flows back into the crucible, ensuring that the main horizontal runner is interrupted in the middle.

[0027] The advantages of this invention are as follows: First, the filling process of the molten metal is driven not only by the pressure in the low-pressure casting machine but also by gravity, which enhances the filling capacity of the molten metal in the thin-walled structure and makes it easier to achieve the complete forming of the thin-walled structure. Second, the large horizontal sprue cannot form a complete whole during casting, which greatly reduces the unevenness of residual stress during the casting process and reduces the amount of deformation during the casting process. Finally, the structure of the gating system is simplified, making the molding and assembly simpler, eliminating the need for mold flipping, reducing workload, and ensuring the stability of the core position. Attached Figure Description

[0028] Figure 1 This is a typical structural form for wall panel castings. Here, 'a' represents the side with reinforcing ribs, and 'b' represents the outer surface.

[0029] Figure 2 This is a standard gating system design for wall panel castings. In this design, 'a' represents the slit gating distribution on the side with reinforcing ribs, and 'b' represents the slit gating distribution on the outer surface.

[0030] Figure 3 This invention presents the distribution pattern of the gating system for wall panel castings.

[0031] Figure 4 This is a schematic diagram showing the connection between the slotted gating system and the horizontal gating system of the present invention.

[0032] Figure 5 This is a schematic diagram of the bending of the slotted gating system of the present invention.

[0033] Figure 6 These are the structural dimensions of the slotted gating system of the present invention.

[0034] Figure 7 This is a structural diagram of the front landing gear skid plate casting. In the diagram, 'a' represents the overall dimensions, 'b' represents the casting reinforcing ribs, and 'c' is a schematic diagram of the longitudinal section wall thickness of the casting.

[0035] Figure 8 This diagram shows the structural form of the casting system for the front landing gear skid plate. Figure a shows the distribution of the slotted gating system, and figure b shows the connection diagram of the transverse gating system.

[0036] Figure 9 The structural dimensions are for the slotted gating system of the front landing gear guard plate.

[0037] Figure 10 A schematic diagram showing the location of the thermocouples for temperature measurement in the main horizontal runner.

[0038] In the figure, 1 is the casting reinforcing rib, 2 is the casting outer surface, 3 is the vertical cylinder, 4 is the low-pressure pouring gate, 5 is the horizontal runner, 6 is the temperature measuring thermocouple, 7 is the side horizontal runner, 8 is the main horizontal runner, 9 is the gap, and 10 is the lug. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0040] The distribution of the gating system is as follows: Figure 3 As shown, the details are as follows:

[0041] The casting is poured horizontally, with the aerodynamic surface facing upwards and the reinforcing rib facing downwards.

[0042] A slit gating system is installed on the outer side of the aerodynamic surface. The gating system is distributed along the length of the casting with a spacing of 250-300 mm. The specific location should be directly above or near the reinforcing rib.

[0043] like Figure 3As shown, the bent vertical tube 3 is connected to the side horizontal runners 7 on both sides. The side horizontal runners are disconnected in the middle. If they interfere with the vertical tube, they are disconnected at a position close to the middle. The cross-sectional shape of the side horizontal runners is square.

[0044] like Figure 4 As shown, the two side horizontal runners 7 are connected together by a main horizontal runner 8, and the cross-sectional shape of the main horizontal runner is also square; the low-pressure pouring port 4 is below the main horizontal runner.

[0045] like Figure 5 As shown, since the cross-sectional shape of the casting along the width direction is an upward-convex arc, the slit gating system is also designed to follow the arc shape. However, at the top of the upward-convex arc, the slit gating system is separated with a spacing of 30-40mm. The gating system extending beyond the sides of the casting retains only the vertical cylinder structure, which bends downward 40-60mm beyond the edge of the casting, perpendicular to the horizontal plane. The end of the downward-bent vertical cylinder 3 extends about 80-100mm beyond the lowest point of the casting. The diameter d of the low-pressure gating port 4 is the side length l of the main horizontal runner. 主 0.6 to 0.8 times the size, with a height of 80 to 100 mm.

[0046] like Figure 6 As shown, the slit gating system consists of a vertical cylinder 3 and a slit 9. The slit width δ is 1.5 to 2 times the thickness w of the aerodynamic surface of the casting, and the vertical cylinder diameter D is 3 to 4 times the slit width δ. The side runners 7 extend 100 to 150 mm beyond the center of the vertical cylinder at both ends, and the side length l of the side runner cross-section is... 侧 It is 1.1 to 1.3 times the diameter of the vertical tube; the main horizontal runner has a side length of l. 主 It is 1.5 to 1.8 times the diameter of the vertical tube, and its length is the distance between the outer sides of the two upper side horizontal runners.

[0047] During low-pressure casting, thermocouples are installed on the main runner to measure the temperature changes of the molten metal in the runner. Figure 5 As shown in Figure 6, when the temperature of the molten metal drops to 20-25°C above the solidification line of the alloy, the pressure holding is stopped, and the molten metal that has not solidified in the main horizontal runner flows back into the crucible, ensuring that the main horizontal runner is interrupted in the middle.

[0048] Example

[0049] The external structure of the casting of the nose landing gear skid plate of a certain type of aircraft is as follows: Figure 7 As shown. The casting is 2100mm long, 600mm wide, 12mm thick with a pneumatic profile, and has an inner reinforcing rib height of 50mm and a thickness of 2.5mm. There are 3 lugs on the inner side for mounting the hinges for opening and closing the guard plate. The maximum height of the lugs is 280mm.

[0050] According to the present invention, the gating system structure and distribution of the front landing gear skid plate casting are as follows: Figure 8 As shown.

[0051] The specific dimensions of the front landing gear skid plate casting system are as follows:

[0052] 1) Distribution of pneumatic surface slotted gating

[0053] like Figure 8 As shown in Figure a, the casting is 2100mm long. The inner reinforcing ribs consist of 6 grids along the length, each grid being 300mm long. The slotted gating system is distributed on the transverse reinforcing ribs, totaling 7 locations with a spacing of 300mm, which are also located directly above the 3 lugs.

[0054] 2) Distribution of side horizontal runners and main horizontal runners

[0055] like Figure 8 As shown in diagram a, the side runner 7 is divided into two sections to reduce the large residual stress generated after solidification and cooling of the large runner. The shorter runner connects to three vertical cylinders 3, and the longer runner connects to four vertical cylinders 3; as shown in diagram a. Figure 8 As shown in b, the side horizontal runners are connected to the main horizontal runner 8. There are a total of 2 main horizontal runners, and a low-pressure pouring port 4 is set in the middle of the main horizontal runner.

[0056] 3) Slot gating dimensions

[0057] like Figure 9 As shown, the sprue consists of a vertical cylinder 3 and a sprue 9. The aerodynamic surface thickness of the casting is 12mm, and the sprue width δ is 1.5 times the thickness of the curved surface at that location, which is 18mm. The diameter D of the vertical cylinder is 3 times the sprue width δ, which is 54mm. The distance from the vertical cylinder to the curved surface of the casting is set to 50mm. The vertical cylinder extends to both sides and then vertically downwards, with the downward distance being 100mm lower than the lowest point of the lug. Figure 8 As shown in a.

[0058] 4) Dimensions of side runners and main runners

[0059] like Figure 10 As shown, the cross-section of the side horizontal gating 7 is square, with a side length of l. 侧 It is 1.1 times the diameter of the vertical tube, i.e., 60mm. The two main horizontal runners have a square cross-section with a side length of l. 主 It is 1.5 times the diameter of the vertical tube, that is, 81mm.

[0060] 5) Low-pressure gate size

[0061] like Figure 10 As shown, the low-pressure pouring nozzle 4 is circular, with a diameter equal to the side length l of the main horizontal runner section. 主 It is 0.8 times the size, which is 65mm, and the height is 80mm.

[0062] Using the above-mentioned gating system, chills were placed in locally thick areas. The mold was a resin sand mold, and the low-pressure casting process parameters are shown in Table 1. During casting, a thermocouple was installed on the main runner. The alloy material was ZL114A, whose solidification temperature range is 550–610℃. When the temperature measured by the thermocouple reached 570℃, the pressure holding was stopped.

[0063] After cleaning, the castings were inspected by X-ray. The metallurgical quality of the castings reached the level of HB963 Class I parts. The thin-walled reinforcing ribs of the castings were fully formed. The maximum deformation of the castings in the as-cast state was 2mm, which fully met the technical requirements.

[0064] Table 1 Low-pressure casting process parameters for front landing gear skid plate castings

[0065]

Claims

1. A design method for a casting gating system for large wall panel components, characterized in that, Includes the following steps: 1) The casting is poured horizontally with the aerodynamic surface facing upwards and the reinforcing rib facing downwards; 2) Multiple slit-type gating systems are set on the outer side of the aerodynamic surface. The gating systems are distributed along the length of the casting with a spacing of 250-300mm. The slit-type gating system consists of a vertical cylinder and slits. The slit width δ is 1.5-2 times the thickness w of the aerodynamic surface of the casting, and the vertical cylinder diameter D is 3-4 times the slit width δ. 3) Since the cross-sectional shape of the casting along the width direction is an upward convex arc, the slit gating system is also designed to follow the shape of the arc. However, at the top of the upward convex arc, the slit gating system is separated with a spacing of 30-40mm. The gating system that extends beyond the sides of the casting only retains the vertical cylinder structure, which bends downward 40-60mm beyond the edge of the casting, perpendicular to the horizontal plane. The end of the downward-bent vertical cylinder extends 80-100mm beyond the lowest point of the casting. 4) The bent vertical tube is connected to the side horizontal runners on both sides. The side horizontal runners are disconnected in the middle. If they interfere with the vertical tube, they are disconnected at a position close to the middle. The two side horizontal runners are then connected together by a main horizontal runner. The gate for low-pressure casting is located below the main horizontal runner.

2. The design method for the casting and gating system of large wall panel components according to claim 1, characterized in that, The slotted gating system is located on the outer surface and directly above or near the reinforcing ribs.

3. The design method for the casting and gating system of large wall panel components according to claim 1, characterized in that, Three to four vent holes with a diameter of Φ3 to 5 mm are made at the break point at the top of each slotted gating system.

4. The design method for the casting and gating system of large wall panel components according to claim 1, characterized in that, Both the side runner and the main runner have square cross-sectional shapes.

5. The design method for the casting and gating system of large wall panel components according to claim 1, characterized in that, Both ends of the side horizontal gating should extend 100-150mm beyond the center of the vertical cylinder closest to the ends of the side horizontal gating. The side length of the side horizontal gating cross-section is l. 侧 It is 1.1 to 1.3 times the diameter of the vertical tube; the side length of the main horizontal runner is l. 主 It is 1.5 to 1.8 times the diameter of the vertical tube, and its length is the distance between the outer sides of the two upper horizontal runners; the gate diameter d is the side length of the main horizontal runner l. 主 0.6 to 0.8 times the size, with a height of 80 to 100 mm.

6. The design method for the casting and gating system of large wall panel components according to claim 1, characterized in that, Apply thermal insulation coating to the inner surface of the main horizontal runner or attach a 3mm thick aluminum silicate fiber felt to the surface and bake it dry.

Images