Differential lubrication method for surface of aviation internal high-pressure forming three-way pipe

Abstract

The invention relates to surface differential lubrication, in particular to a surface differential lubrication method for an aviation internal high-pressure forming three-way pipe. The top of the three-way branch pipe can be effectively prevented from being broken, and meanwhile wrinkles in a non-deformation area are effectively prevented. Comprising the following steps: S1, selecting a metal tube blank with certain outer diameter and wall thickness according to the specification of a finished product; s2, the surface quality and the internal quality of the pipe blank are checked; s3, the pipe blank is cut to the length of 250 mm; s4, a material supplementing area, a deformation area and a non-deformation area are marked on the pipe blank through a marking pen; s5, the non-deformation area is subjected to polishing treatment through raw abrasive paper; s6, a molybdenum disulfide lubricant is sprayed to the deformation area to reduce friction force; s7, the material supplementing area is not treated; s8, the pipe blank is placed in the dies, and the upper die and the lower die are closed to start the forming process; s9, advancing to a water injection position through a left pushing head and a right pushing head; s10, continuously advancing to a sealing position; s11, liquid is injected into the pipe through the push head; s12, applying counter-acting force to the formed three-way branch pipe by using a reverse thrust head; and S13, forming is completed.

Description

Technical Field

[0001] The invention relates to surface differential lubrication, in particular to a surface differential lubrication method for an aviation high pressure forming tee pipe. Background Art

[0002] Tee fittings play an extremely important role in complex pipeline connections, especially in aerospace and other fields. Traditionally, the manufacture of such pipe fittings is often carried out by half-pipe welding, but this method has the problems of low forming accuracy and poor surface quality.

[0003] In recent years, with the development of technology, high pressure forming technology has emerged, providing a new solution to the above problems. This technology uses liquid as a medium to transmit force, combined with specially designed molds, and uses a simple process loading path to achieve the overall forming of parts with complex cavities or shapes. According to specific technical requirements, this technology can support single or multiple forming operations, so it is favored by the modern processing industry. Compared with traditional welding methods, high pressure forming technology can realize the integrated forming of tube blanks, which not only significantly improves production efficiency, but also makes the final product lighter and smoother. In summary, high pressure forming technology represents an advanced trend in the current field of pipe manufacturing.

[0004] During the forming process of the tee parts, due to the liquid pressure inside the pipe, a large contact force is generated between the pipe blank and the mold cavity, thereby generating a large friction force. The influence of friction on the forming of the tee parts is very important. At present, for the pipe blank before internal high pressure forming, one is to form it directly without treatment, and the other is to spray soap liquid, molybdenum disulfide, lubricating oil, etc. for overall lubrication to reduce friction. Both methods have certain disadvantages:

[0005] The first method is to form directly without processing. There will be a large friction between the die and the tube blank, which makes it difficult for the material to flow in the feeding area C due to the large friction. The material cannot flow to the deformation area A, causing the material to accumulate in the feeding area C and produce wrinkles. Because the material in the feeding area C cannot flow to the deformation area A, the deformation area A cannot reach the required height of the tee branch pipe, and the wall thickness of the top of the tee branch pipe will be severely thinned until it reaches the yield limit and breaks.

[0006] The second method is to spray soap solution, molybdenum disulfide, lubricating oil, etc. for overall lubrication. This method can reduce the friction between the tube blank and the mold, which is beneficial to the flow of material in the feeding area C and thus improve the forming height of the three-way branch pipe. Figure 1 As shown, wrinkles will be generated in the non-deformation area B due to material flow accumulation, affecting the surface quality. Summary of the invention

[0007] The present invention aims at the defects of the prior art and provides a differential lubrication method for the surface of an aviation high pressure forming tee pipe.

[0008] To achieve the above object, the present invention adopts the following technical scheme, a method for differential lubrication of the surface of an aviation high pressure forming tee pipe, comprising the steps of:

[0009] S1. Select a metal tube blank with a certain outer diameter and wall thickness according to the finished product specifications;

[0010] S2. Check the surface and internal quality of the tube to ensure there are no defects;

[0011] S3, using a cutting machine to cut the tube blank into a length of 250 mm, and ensure that the end faces at both ends are perpendicular to the axis, and remove the burrs at both ends to ensure sealing;

[0012] S4, using a marker pen to mark the feeding area (90 mm inward from both ends), the deformation area (one third of the middle 70 mm along the axial direction) and the non-deformation area (the remaining part) on the tube blank;

[0013] S5, grinding the non-deformed area with coarse sandpaper to increase the friction of the area, and cleaning the aluminum chips generated by grinding with an air gun;

[0014] S6. Spraying molybdenum disulfide lubricant on the deformation area to reduce friction. Before spraying, other areas can be protected with adhesive tape to avoid contamination;

[0015] S7, the feeding area is not processed;

[0016] S8, placing the processed tube blank into the mold, closing the upper and lower molds to start the forming process;

[0017] S9: During the forming process, the left pusher and the right pusher first advance to the water injection position to discharge the air in the tube;

[0018] S10, then the left and right push heads continue to move forward to the sealing position and contact the tube blank to form a seal;

[0019] S11, inject liquid into the tube through the push head, set the initial feeding pressure to 6MPa, and the feeding volume each time to 2mm. The internal pressure and feeding volume curve are as follows Fig. 9 When the liquid pressure in the tube reaches 6MPa, the left and right push heads move forward to force the material in the feeding area to flow to the deformation area. At the same time, the deformation area deforms to form a three-way branch pipe. The total feeding volume is 26mm and the maximum internal pressure is 40MPa. Among them, the non-deformation area is not easy to produce wrinkles due to the large friction.

[0020] S12, using the reverse thrust head to apply a reaction force to the formed three-way branch pipe to prevent the top wall from becoming thinner and cracking;

[0021] S13. After forming is completed, open the mold, take out the three-way pipe fitting, and check its forming quality.

[0022] Furthermore, in S2, the defects include any one or more of scratches, cracks, sharp pits, and flat pits.

[0023] Furthermore, the lubricant is molybdenum disulfide, which can effectively reduce the friction coefficient of the deformation zone.

[0024] Furthermore, during the forming process, the shape and size of the three-way pipe can be accurately controlled by controlling the movement of the left and right push heads and the liquid pressure.

[0025] Further, the mold is an internal high pressure forming mold, which includes an upper mold and a lower mold, both of which have the same structure, and both of which are provided with a through groove channel 1 and a groove channel 2 perpendicular thereto on their surfaces, and the groove channel 1 is connected to the groove channel 2; when the upper and lower molds are molded together, the two groove channels 1 form a first accommodating cavity for accommodating the straight tube to be processed, and the two groove channels 2 form a second accommodating cavity for accommodating the reverse thrust head; the straight tube to be processed is placed in the two groove channels 1 after the molds are molded together, and its tube body passes through the groove channel 2 and fits the shape of the first accommodating cavity;

[0026] The internal high pressure forming die also includes a left pusher head and a right pusher head, each pusher head includes a columnar portion and a round pancake-shaped end portion, wherein the columnar portion of at least one pusher head is provided with a liquid outlet, and the end portion is provided with a liquid inlet, and the liquid outlet and the liquid inlet are connected through a channel; when in use, the columnar portion of the left pusher head extends from one end of the first accommodating cavity and abuts against one end of the straight tube, and the columnar portion of the right pusher head extends from the other end into the first accommodating cavity and abuts against the other end of the straight tube;

[0027] The internal high-pressure forming mold also includes a reverse thrust head, which includes a cylindrical portion and a round pancake-shaped end portion. When in use, it is located in the second accommodating cavity, and its end portion fits with both sides of the second accommodating cavity; sealing rubber rings are provided on the top of the left push head and the right push head, which fit tightly with the tube walls at both ends of the straight tube to form a sealed space.

[0028] Compared with the prior art, the present invention has beneficial effects.

[0029] The present invention makes different friction coefficients of different regions of the tee tube blank different by performing different surface treatments (spraying molybdenum disulfide lubricant and sandpaper polishing) on ​​different regions of the tee tube blank during internal high pressure forming, thereby solving the problem of wrinkles and ruptures being easily generated during the forming process of the tee tube, and at the same time, it is beneficial to reduce the wall thickness reduction amount and increase the forming height of the tee branch tube. It can effectively prevent the top of the tee branch tube from rupture, and at the same time effectively prevent the generation of wrinkles in the non-deformation zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. The protection scope of the present invention is not limited to the following description.

[0031] Figure 1 It is a schematic diagram of a pleated three-way pipe in the prior art.

[0032] Figure 2 This is the modeling diagram of the integral lubrication tee.

[0033] Figure 3 This is a diagram of a differential lubrication tee model.

[0034] Figure 4 It is a schematic diagram of the overall lubrication results.

[0035] Figure 5 It is a schematic diagram of differential lubrication simulation.

[0036] Figure 6 It is a schematic diagram of the tube before forming.

[0037] Figure 7-8 This is a structural diagram of the internal high pressure forming die.

[0038] Fig. 9 It is a curve diagram of internal pressure and feed amount.

[0039] In the figure, 1 is the deformation zone, 2 is the non-deformation zone, 3 is the feeding zone, 4 is the non-deformation zone after forming, 5 is the three-way branch pipe after forming, 6 is the left push head, 7 is the right push head, 8 is the reverse push head, 9 is the lower mold, 10 is the mold cavity, 11 is the overall lubrication billet, 11 is the deformation zone of the differential lubrication billet, 12 is the non-deformation zone of the differential lubrication billet, and 13 is the feeding zone of the differential lubrication billet. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and beneficial effects of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0041] For the convenience of explaining the problem, the initial tube is divided into three areas: feeding area, deformation area, and non-deformation area. Figure 6 shown.

[0042] like Figure 7-8 As shown, the specific embodiments include:

[0043] Step 1: Select the tube blank of corresponding material, diameter and wall thickness according to the finished product specifications. This scheme takes the tee tube with outer diameter of φ55mm and wall thickness of 1.5mm as an example.

[0044] Step 2: Check the surface and internal quality of the tube blank. There should be no defects such as scratches, cracks, sharp pits, flat pits, etc.

[0045] Step 3: Use a cutting machine to cut the tube into 250mm long straight tubes and remove the burrs at both ends of the tube. When cutting, ensure that the end faces of the tube are perpendicular to the axis, otherwise it will affect the sealing of the tube.

[0046] Step 4: Use a marker pen to divide the tube into different areas: 90mm inward from both ends of the tube is the feeding area 3, and the remaining 70mm in the middle of the tube is divided into three equal parts along the axial direction, divided into deformation area 1 and non-deformation area 2.

[0047] Step 5: Use coarse sandpaper to grind the non-deformed area 2 to increase the friction of the non-deformed area 2. After grinding, use an air gun to blow away the aluminum chips.

[0048] Step 6: Spray molybdenum disulfide lubricant on deformation zone 1 to reduce the friction of deformation zone 1. To prevent molybdenum disulfide from being sprayed on other areas, wrap other areas with tape before spraying.

[0049] Step 7: No treatment is done in feeding zone 3.

[0050] Step 8: Place the processed tube blank into the mold 9, start the equipment, close the upper and lower molds, and start forming.

[0051] Step 9: During forming, the left push head 6 and the right push head 7 first move forward to the water injection position, and inject water to discharge the air in the tube.

[0052] Step 10: The left push head 6 and the right push head 7 continue to move forward to the sealing position and achieve sealing after contacting the tube blank.

[0053] Step 11: Liquid is injected into the tube blank through the pusher head, and the left and right pushers are adjusted according to the set internal pressure-displacement curve (such as Fig. 9 The tube blank is pushed forward by the feeding area 3 at both ends of the tube blank to feed the material to the middle deformation area 1, and the deformation area 1 begins to deform to form a three-way branch pipe 5. The non-deformation area 4 has been polished, and the friction is large, and the material is difficult to flow, so no wrinkles will be generated. The reverse push head 8 applies a reaction force to the three-way branch pipe 5, which can effectively prevent the top wall thickness of the three-way branch pipe 5 from being thinned and prevent the top of the branch pipe 5 from being broken.

[0054] Step 12: Open the mold, take out the tee pipe, and check the forming quality.

[0055] The mold is an internal high pressure forming mold, which includes an upper mold and a lower mold, both of which have the same structure, and both of which are provided with a through groove channel 1 and a groove channel 2 perpendicular thereto on their surfaces, and the groove channel 1 is connected to the groove channel 2; when the upper and lower molds are molded together, the two groove channels 1 form a first accommodating cavity for accommodating the straight tube to be processed, and the two groove channels 2 form a second accommodating cavity for accommodating the reverse thrust head; the straight tube to be processed is placed in the two groove channels 1 after the molds are molded together, and the tube body passes through the groove channel 2 and fits the shape of the first accommodating cavity;

[0056] The internal high pressure forming die also includes a left pusher head and a right pusher head, each pusher head includes a columnar portion and a round pancake-shaped end portion, wherein the columnar portion of at least one pusher head is provided with a liquid outlet, and the end portion is provided with a liquid inlet, and the liquid outlet and the liquid inlet are connected through a channel; when in use, the columnar portion of the left pusher head extends from one end of the first accommodating cavity and abuts against one end of the straight tube, and the columnar portion of the right pusher head extends from the other end into the first accommodating cavity and abuts against the other end of the straight tube;

[0057] The internal high-pressure forming mold also includes a reverse thrust head, which includes a cylindrical portion and a round pancake-shaped end portion. When in use, it is located in the second accommodating cavity, and its end portion fits with both sides of the second accommodating cavity; sealing rubber rings are provided on the top of the left push head and the right push head, which fit tightly with the tube walls at both ends of the straight tube to form a sealed space.

[0058] The present invention utilizes the method of surface differential lubrication to improve the forming quality of the tee pipe. Specifically, molybdenum disulfide lubricant is sprayed on the deformation zone to increase the height of the tee branch pipe and reduce the wall thickness reduction. Sandpaper polishing is performed on the non-deformation zone to effectively prevent the problem of wrinkles in the non-deformation zone.

[0059] Example 1: A method of differential surface lubrication is used to generate different friction forces in different areas of the tube blank. The height of the tee branch is increased, which effectively prevents the top of the tee branch from breaking, and effectively prevents the formation of wrinkles in the non-deformed area. This is achieved by dividing the tube blank before internal high-pressure forming into different areas and performing different surface treatments on different areas. The surface is roughened by sandpaper polishing to increase friction, and the friction coefficient after polishing is about 0.2; the surface is lubricated by spraying molybdenum disulfide lubricant to reduce friction, and the friction coefficient after spraying molybdenum disulfide is about 0.05; the friction coefficient without any treatment is about 0.12. In order to verify the feasibility of the present technical solution, ABAQUS software was used for simulation before trial production, and the overall lubrication tee and differential lubrication tee were simulated respectively. Since the tee pipe has a symmetrical structure, in order to save calculation time, a 1 / 4 model is used for modeling. The model is as follows Figure 2 , 3As shown. The tube blank is set as a deformable sheet structure, the diameter is set to 55mm, the wall thickness is set to 1.5mm, and the mold, right push head, and reverse push head adopt discrete rigid body structure. The linear loading method is adopted, the internal pressure peak is 40MPa, and the right punch feed amount is 20mm. First, liquid is injected into the tube blank in the sealing stage, and then the push head starts to feed, and the internal pressure is loaded according to the loading path. The reverse push head pressure is constant at 3MPa.

[0060] The friction coefficients of each area of ​​the integrally lubricated tee and differentially lubricated tee are shown in Table 1.

[0061] Table 1 Simulation schemes of integral lubrication tee and differential lubrication tee

[0062]

[0063] The overall lubrication simulation results are shown in Figure 4 , the minimum wall thickness of the top of the tee branch is about 1.042mm, and the minimum wall thickness of the straight section of the tee branch is about 1.270mm. Figure 4 The tube blank (marked by the middle red circle) is concave inward, indicating that wrinkles have occurred here.

[0064] The simulation results of differential lubrication are shown in Figure 5 The minimum wall thickness at the top of the tee branch is about 1.084 mm, and the minimum wall thickness at the straight section of the tee branch is about 1.307 mm. No instability or wrinkling occurs in the non-deformation zone, indicating that the forming is good here.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. Therefore, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of the present invention.

Claims

1. A differential lubrication method for the surface of an aviation high pressure forming tee pipe, comprising the following steps: S1. Select a metal tube blank with a certain outer diameter and wall thickness according to the finished product specifications; S2. Check the surface and internal quality of the tube to ensure there are no defects; S3, using a cutting machine to cut the tube blank into a length of 250 mm, and ensure that the end faces at both ends are perpendicular to the axis, and remove the burrs at both ends to ensure sealing; S4, using a marking pen to mark the feeding area, deformation area and non-deformation area on the tube blank; S5, grinding the non-deformed area with coarse sandpaper to increase the friction of the area, and cleaning the aluminum chips generated by grinding with an air gun; S6. Spraying molybdenum disulfide lubricant on the deformation area to reduce friction. Before spraying, other areas can be protected with adhesive tape to avoid contamination; S7, the feeding area is not processed; S8, placing the processed tube blank into the mold, closing the upper and lower molds to start the forming process; S9: During the forming process, the left pusher and the right pusher first advance to the water injection position to discharge the air in the tube; S10, then the left and right push heads continue to move forward to the sealing position and contact the tube blank to form a seal; S11, injecting liquid into the tube through the pusher head to promote the material in the feeding area to flow to the deformation area, and at the same time the deformation area is deformed to form a three-way branch pipe; wherein the non-deformation area is not easy to generate wrinkles due to the large friction force; S12, using the reverse thrust head to apply a reaction force to the formed three-way branch pipe to prevent the top wall from becoming thinner and cracking; S13. After forming is completed, open the mold, take out the three-way pipe fitting, and check its forming quality.

2. The method according to claim 1, characterized in that: In S2, the defects include any one or more of scratches, cracks, sharp pits, and flat pits.

3. The method according to claim 1, characterized in that: The lubricant is molybdenum disulfide, which can effectively reduce the friction coefficient of the deformation zone.

4. The method according to claim 1, characterized in that: During the forming process, the shape and size of the three-way pipe can be precisely controlled by controlling the movement of the left and right push heads and the liquid pressure.

5. The method according to claim 1, characterized in that: The mold is an internal high pressure forming mold, which includes an upper mold and a lower mold, both of which have the same structure, and both of which are provided with a through groove channel 1 and a groove channel 2 perpendicular thereto on their surfaces, and the groove channel 1 is connected to the groove channel 2; when the upper and lower molds are molded together, the two groove channels 1 form a first accommodating cavity for accommodating the straight tube to be processed, and the two groove channels 2 form a second accommodating cavity for accommodating the reverse thrust head; the straight tube to be processed is placed in the two groove channels 1 after the molds are molded together, and the tube body passes through the groove channel 2 and fits the shape of the first accommodating cavity; The internal high pressure forming die also includes a left pusher head and a right pusher head, each pusher head includes a columnar portion and a round pancake-shaped end portion, wherein the columnar portion of at least one pusher head is provided with a liquid outlet, and the end portion is provided with a liquid inlet, and the liquid outlet and the liquid inlet are connected through a channel; when in use, the columnar portion of the left pusher head extends from one end of the first accommodating cavity and abuts against one end of the straight tube, and the columnar portion of the right pusher head extends from the other end into the first accommodating cavity and abuts against the other end of the straight tube; The internal high-pressure forming mold also includes a reverse thrust head, which includes a cylindrical portion and a round pancake-shaped end portion. When in use, it is located in the second accommodating cavity, and its end portion fits with both sides of the second accommodating cavity; sealing rubber rings are provided on the top of the left push head and the right push head, which fit tightly with the tube walls at both ends of the straight tube to form a sealed space.

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