Thin-walled tube with self-centering function and processing method thereof

Abstract

The application provides a thin-wall pipe backward extrusion die with self-centering function and a processing method thereof, and the die comprises an extrusion rod, an extrusion rod end, a guide cylinder and an extrusion cylinder; the top of the extrusion rod is used for connecting an external pressure device, the bottom of the extrusion rod is provided with the extrusion rod end, the extrusion rod end is used for extruding a blank inside the extrusion cylinder, and the bottom of the extrusion rod end is provided with a guide structure matched with the top of the blank; the bottom of the guide cylinder is sleeved outside the backward extrusion die, the top of the guide cylinder is sleeved outside the extrusion rod, and the guide cylinder, the backward extrusion die and the extrusion rod are coaxially arranged. The application processes the outer surface of the blank before backward extrusion, so that the extrusion rod end is tightly matched with the blank, thereby realizing high centering degree of the extrusion rod through the blank itself and the die without designing a corresponding die, a special high-precision and complex backward extrusion die is not needed, the die design and manufacturing period is shortened, and the economic benefit is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reverse extrusion forming of thin-walled pipes, in particular to a thin-walled pipe reverse extrusion die with self-centering function and a processing method thereof. BACKGROUND

[0002] Reverse extrusion forming technology is widely used in the production of non-ferrous metal products such as aluminum and magnesium due to its small extrusion force, high dimensional accuracy of extruded products, and more uniform organization and performance, especially for high-strength aluminum alloy. The production of thin-walled pipes of such materials usually adopts hot extrusion forming process, and needs to be matched with an extruder. According to the design of the extruder, a corresponding die is designed, which has a complex structure and a long processing cycle, and cannot meet the needs of product pre-research and small-batch production. In addition, during the reverse extrusion forming of thin-walled pipes, eccentricity is easily caused, leading to scrap of the workpiece. The die structure is required to be high, and the high-cost die manufacturing cost further increases the research and development cost. Therefore, for small-batch production or pre-research, it is of great significance to provide a low-cost, simple-structured, high-precision reverse extrusion forming device with low requirements for equipment, which can shorten the development cycle of new products and small-batch production. SUMMARY

[0003] In view of the defects in the prior art, the purpose of the present application is to provide a thin-walled pipe reverse extrusion die with self-centering function and a processing method thereof.

[0004] The thin-walled pipe reverse extrusion die with self-centering function provided by the present application comprises an extrusion rod, an extrusion rod end, a guide cylinder and an extrusion cylinder.

[0005] The top of the extrusion rod is used to connect an external pressure device, the bottom of the extrusion rod is provided with an extrusion rod end, the extrusion rod end is used to extrude a blank inside the extrusion cylinder, and the bottom of the extrusion rod end is provided with a guide structure matched with the top of the blank.

[0006] The bottom of the guide cylinder is sleeved outside the reverse extrusion die, the top of the guide cylinder is sleeved outside the extrusion rod, and the guide cylinder, the reverse extrusion die and the extrusion rod are coaxially arranged.

[0007] Preferably, the corresponding side surface of the working zone of the extrusion rod end is an extrusion working surface, and the height of the top surface of the blank is greater than or equal to the height of the extrusion working surface of the extrusion rod end.

[0008] The top of the blank is provided with a guide surface matched with the lower bottom surface and the side surface of the guide structure.

[0009] When the die is in an assembled state, the extrusion working surface and the side surface of the blank are in clearance fit.

[0010] Preferably, the bottom end surface of the extrusion rod end is processed with an annular groove coaxial with the extrusion rod end.

[0011] Preferably, the extrusion cylinder comprises a base, an extrusion cylinder outer shell and an extrusion cylinder liner, and the extrusion cylinder outer shell is fixedly mounted on the base;

[0012] The extrusion cylinder liner is coaxially and detachably installed in the extrusion cylinder outer shell, the lower end surface of the guide cylinder overlaps the upper end surface of the extrusion cylinder outer shell, and the height of the upper end surface of the reverse extrusion cylinder outer shell is greater than the height of the billet.

[0013] Preferably, the guide cylinder is directly connected to the outer surface of the extrusion cylinder liner, and there is a transition fit between the two. The length of the connecting portion between the guide cylinder and the extrusion cylinder liner is greater than 1 / 5 of the height of the guide cylinder.

[0014] Preferably, an extrusion rod support pad is fixedly mounted on the top of the extrusion rod.

[0015] Preferably, the end of the extrusion rod is detachably mounted on the bottom of the extrusion rod via a thread.

[0016] Preferably, air guide holes are processed on the side wall of the guide cylinder.

[0017] According to the present invention, a method for processing a thin-walled tube reverse extrusion die with a self-centering function is provided, which uses the thin-walled tube reverse extrusion die with a self-centering function, and includes the following steps:

[0018] Step 1: Process the blank according to the shape of the cavity between the end of the extrusion rod and the lining of the extrusion cylinder, so that the upper end surface of the blank can fit the end of the extrusion rod;

[0019] Step 2: Assemble the mold, place the billet, extrusion rod and extrusion rod end into the extrusion cylinder, then install the guide cylinder, and finally install the extrusion rod support pad;

[0020] Step 3: Heat treatment: Place the assembled mold and blank into a heating furnace and heat them according to the preset system;

[0021] Step 4: After heat treatment, the mold is transferred to the press to start reverse extrusion. The extrusion rod is driven down a specified distance according to the preset parameters to complete the production of the reverse extruded cylindrical part.

[0022] Step 5: After the mold cools down, the extruded rod, cylindrical part and the end of the extruded rod are taken out together and machined to remove the bottom margin of the cylindrical part, separate and remove the end of the extruded rod to obtain the target pipe.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention has a simple structure and is easy to operate. The outer surface of the blank is machined before reverse extrusion, so that the end of the extrusion rod is closely matched with the blank. The outer wall of the extrusion rod end, the inner wall of the extrusion cylinder lining, and the inner and outer walls of the blank are kept coaxial. Therefore, without designing a corresponding mold, a high degree of centering of the extrusion rod is achieved between the blank itself and the mold. There is no need to design a special high-precision and complex reverse extrusion mold, which shortens the mold design and manufacturing cycle and has high economic benefits.

[0025] 2. The present invention assembles and positions the blank and the reverse extrusion die before reverse extrusion, and then places the blank in a furnace for heating together, thereby utilizing the residual heat of the die to achieve approximately isothermal reverse extrusion forming.

[0026] 3. The present invention can replace different extrusion rod ends and extrusion barrel liners according to pipe specifications, which is simple and convenient.

[0027] 4. The present invention has a wide range of applications. The reverse extrusion die has no special requirements for the equipment, as long as the tonnage is met. This set of dies can be used directly on an ordinary press without the need for additional heating of the die. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0029] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0030] Figure 2 It is a partial enlarged schematic diagram of the fitting position between the end of the extruded rod and the blank in the present invention;

[0031] Figure 3 is a cross-sectional view of the blank in the present invention;

[0032] Figure 4 Schematic diagram of the structure of the tapered extruded rod head in the present invention;

[0033] Figure 5 for Figure 4 Cross-sectional view of the mid-tapered extruded club head at angle AA;

[0034] Figure 6 for Figure 5 A partial enlarged view of the middle tapered extruded rod head I;

[0035] Figure 7 Schematic diagram of the bottom view of the tapered extruded rod head in the present invention.

[0036] The figure shows:

[0037] DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0039] The present invention discloses a thin-walled pipe reverse extrusion die with a self-centering function and a processing method thereof. Compared with the prior art scheme of adopting a hot extrusion forming process and designing a corresponding die according to an extruder, the present application machines the outer surface of the blank before reverse extrusion, so that the end of the extrusion rod is tightly matched with the blank, and the outer wall of the extrusion rod end, the inner wall of the extrusion barrel lining and the inner and outer walls of the blank are kept coaxial, and a guide barrel is coaxially sleeved on the outside of the extrusion barrel, so that a high degree of centering of the extrusion rod is achieved between the blank itself and the die without designing a corresponding die. The invention can be applied to the exploration of the early reverse extrusion process and small-batch production.

[0040] According to the thin-walled pipe reverse extrusion die with self-centering function provided by the present invention, Figure 1 As shown, it includes an extrusion rod 7, an extrusion rod end 3, a guide cylinder 1 and an extrusion cylinder; the top of the extrusion rod 7 is used to connect to an external pressure device, and the bottom of the extrusion rod 7 is installed with an extrusion rod end 3, and the extrusion rod end 3 is used to extrude the blank 5 inside the extrusion cylinder, and the bottom of the extrusion rod end 3 is provided with a guide structure that matches the top of the blank 5; the bottom of the guide cylinder 1 is sleeved on the outside of the reverse extrusion die, and the top of the guide cylinder 1 is sleeved on the outside of the extrusion rod 7, and the guide cylinder 1, the reverse extrusion die and the extrusion rod 7 are coaxially arranged.

[0041] The bottom surface of the extrusion rod end 3 is the extrusion working surface, and a clearance fit is adopted between the extrusion working surface and the top surface of the blank 5; the height of the top surface of the blank 5 is greater than or equal to the height of the extrusion working surface of the extrusion rod end 3. The top of the blank 5 is provided with a guide surface that matches the lower bottom surface and side surface of the frustum structure. The bottom end surface of the extrusion rod end 3 is processed with an annular groove coaxial with the extrusion rod end 3. The extrusion cylinder includes a base 2, an extrusion cylinder jacket 4 and an extrusion cylinder liner 8, and the extrusion cylinder jacket 4 is fixedly mounted on the base 2; the extrusion cylinder liner 8 is coaxially and detachably mounted in the extrusion cylinder jacket 4, and the top of the extrusion cylinder liner 8 is provided in the guide cylinder 1, and the lower end surface of the guide cylinder 1 overlaps the upper end surface of the extrusion cylinder jacket 4, and the height of the upper end surface of the counter-extrusion cylinder jacket 4 is greater than the height of the blank 5.

[0042] Example 1

[0043] This embodiment provides a thin-walled pipe reverse extrusion die with a self-centering function. The reverse extrusion die includes: an extrusion rod 7, an extrusion rod end 3, a guide cylinder 1, a guide sleeve 6, an extrusion cylinder liner 8, an extrusion cylinder outer sleeve 4, a base 2, and an extrusion rod support pad 9. The extrusion rod 7 and the extrusion rod end 3 together form a punch; the extrusion cylinder liner 8, the extrusion cylinder outer sleeve 4, and the base 2 together form a die; and the guide cylinder 1 and the guide sleeve 6 together form a guide assembly, which ensures the concentricity of the extrusion rod 7, the extrusion cylinder, and the pipe during extrusion.

[0044] The working band of the extrusion rod end 3 and the blank 5 are matched with a clearance fit. The height of the blank 5 filling the cavity between the extrusion rod end 3 and the extrusion barrel liner 8 should exceed or be flush with the working band of the extrusion rod end 3. An annular groove is processed on the bottom end face of the extrusion rod end 3 to inhibit the flow of material on the contact surface to ensure that the material flows evenly to the pipe. The height of the extrusion barrel jacket 4 should be greater than the height of the blank 5. An extrusion rod support pad 9 is added to the top of the extrusion rod 7 to ensure that the mold is evenly stressed during the reverse extrusion process. The base 2 and the extrusion rod support pad 9 can also be changed according to the model of the extruder and fixed to the extruder.

[0045] The guide tube 1 is machined with air guide holes to facilitate subsequent demolding. The guide tube 1 is directly connected to the outer layer of the extrusion tube liner 8 using a transition fit. The length of the connection should be greater than 1 / 5 of the guide tube's height. The extrusion rod 7 and the extrusion rod end 3 are connected by threads. After the back-extrusion is completed, the extrusion rod 7 is removed to facilitate subsequent demolding. The extrusion tube liner 8 and the extrusion rod end 3 can be replaced with different sizes to produce pipes of different specifications.

[0046] The processing method of the thin-walled pipe reverse extrusion die with self-centering function provided by the present invention is suitable for reverse extrusion forming of thin-walled pipes. First, the outer shape of the extrusion rod end 3 and the blank 5 is used to guide the concentricity of the extrusion rod 7 and the blank 5 during the assembly process. Then, with the further restraint of the guide cylinder 1 and the guide sleeve 6, the extrusion rod 7 moves along the center line of the reverse extrusion die to achieve centering during the reverse extrusion process, ensuring that the wall thickness of the produced thin-walled pipe is uniform. Figure 1 As shown, the method specifically includes:

[0047] Step S1: Machine the outer surface of the blank 5, and then process the blank 5 according to the shape of the cavity between the extrusion rod end 3 and the extrusion barrel liner 8, so that the extrusion rod end 3 can fit tightly with the blank 5, and the height must be greater than or equal to the working band height of the extrusion rod end 3, and the working band and the blank 5 are clearance-fitted.

[0048] Step S2: Place the blank 5 and the extrusion rod 7 as a whole into the extrusion cylinder, then install the guide cylinder 1, and finally install the extrusion rod support pad 9 through the bolts 10.

[0049] Step S3: placing the assembled mold and the blank 5 together into a heating furnace and heating them according to a predetermined system.

[0050] Step S4: transferring the heat-treated mold to a press to start reverse extrusion, and pressing down a specified distance according to pre-set parameters to complete the production of the reverse extruded cylindrical part;

[0051] Step S5: After the mold is cooled, the extruded rod end 3 is taken out together with the cylindrical part, and the bottom excess is removed by machining to take out the extruded rod end to obtain the target pipe.

[0052] Among them, the extrusion rod support pad 9 and the base 2 can be changed according to the requirements of the press, and can also be fixed on the press. The materials of the guide sleeve 6, the guide cylinder 1 and the extrusion rod 7 can preferably be the same material, which can effectively avoid the mold jamming caused by heating. The guide cylinder 1 and the extrusion cylinder liner 8 adopt a transition fit, and the length of the connecting part should be greater than 1 / 5 of the height of the guide cylinder 1 to ensure that the guide cylinder can withstand the eccentric load during the extrusion process, thereby effectively suppressing the occurrence of eccentricity. The blank used for back extrusion can be non-ferrous metals such as aluminum alloy and magnesium alloy.

[0053] Next, the above-mentioned processing method will be described in more detail.

[0054] Example 2:

[0055] After the positive extrusion blank is opened, the spray-formed high-strength aluminum alloy material is turned into a cylindrical blank with a diameter of 155mm and a height of 175mm. The blank is then processed according to the space cavity between the end of the extrusion rod and the inner lining of the extrusion cylinder, such as Figure 2 As shown, the working zone of the extrusion rod end and the blank are matched with a clearance of H6 / h5, and the mold material is H13 hot die steel. First, evenly apply a layer of graphite lubricant to the blank and the extrusion rod end to prevent sticking to the mold. After the reverse extrusion cylinder outer shell and the inner lining are assembled with interference fit, the blank and the extrusion rod are placed, the punch is assembled, and the extrusion rod support pad is installed. Then, the mold and the blank are placed in a heating furnace as a whole and heated to 450°C and kept warm for 6 hours as required. After heating is completed, it is transferred to the press and hot reverse extrusion is performed at an extrusion speed of 60mm / min. After the extrusion is completed and the mold is cooled, the extrusion rod end is taken out together with the cylindrical part, and the bottom excess is removed by machining to obtain the target thin-walled pipe. In this embodiment, the sample is an aluminum alloy material, and the raw material for the reverse extrusion thin-walled pipe can be other non-ferrous metal materials.

[0056] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0057] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the specific embodiments described above, and various changes or modifications can be made by those skilled in the art within the scope of the claims, which do not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other in the case of no conflict.

Claims

1. A thin-walled pipe reverse extrusion die with self-centering function, characterized in that: It comprises an extrusion rod (7), an extrusion rod end (3), a guide cylinder (1) and an extrusion cylinder; The top of the extrusion rod (7) is used to connect to an external pressure device, and the bottom of the extrusion rod (7) is equipped with an extrusion rod end (3), and the extrusion rod end (3) is used to extrude the blank (5) inside the extrusion cylinder, and the bottom of the extrusion rod end (3) is provided with a guide structure that matches the top of the blank (5); The bottom of the guide cylinder (1) is sleeved on the outside of the reverse extrusion die, the top of the guide cylinder (1) is sleeved on the outside of the extrusion rod (7), and the guide cylinder (1), the reverse extrusion die and the extrusion rod (7) are coaxially arranged; The side surface corresponding to the working zone of the extrusion rod end (3) is an extrusion working surface, and the height of the top surface of the blank (5) is greater than or equal to the height of the extrusion working surface of the extrusion rod end (3); When the die is in an assembled state, a clearance fit is adopted between the extrusion working surface and the inner side surface of the blank (5); The top of the blank (5) is provided with a guide surface that matches the bottom surface and side surfaces of the guide structure; The bottom end surface of the extrusion rod end head (3) is machined with an annular groove coaxial with the extrusion rod end head (3).

2. The thin-walled pipe reverse extrusion die with self-centering function according to claim 1, characterized in that: The extrusion cylinder comprises a base (2), an extrusion cylinder outer shell (4) and an extrusion cylinder liner (8), wherein the extrusion cylinder outer shell (4) is fixedly mounted on the base (2); The extrusion cylinder liner (8) is coaxially and detachably installed in the extrusion cylinder outer shell (4), and the height of the upper end surface of the reverse extrusion cylinder outer shell (4) is greater than the height of the blank (5).

3. The thin-walled pipe reverse extrusion die with self-centering function according to claim 1, characterized in that: The guide cylinder (1) is directly connected to the outer surface of the extrusion cylinder liner (8), and the two are transitionally matched. The length of the connection portion between the guide cylinder (1) and the extrusion cylinder liner (8) is greater than 1 / 5 of the height of the guide cylinder (1).

4. The thin-walled pipe reverse extrusion die with self-centering function according to claim 1, characterized in that: An extrusion rod support pad (9) is fixedly mounted on the top of the extrusion rod (7).

5. The thin-walled pipe reverse extrusion die with self-centering function according to claim 1, characterized in that: The extrusion rod end (3) is detachably mounted on the bottom of the extrusion rod (7) via a thread.

6. The thin-walled pipe reverse extrusion die with self-centering function according to claim 1, characterized in that: An air guide hole is machined on the side wall of the guide cylinder (1).

7. A method for processing a thin-walled pipe reverse extrusion die with a self-centering function, characterized in that: The thin-walled pipe reverse extrusion die with a self-centering function according to any one of claims 1 to 6 is used, comprising the following steps: Step 1: Processing the blank (5), processing the blank (5) according to the shape of the cavity between the extrusion rod end (3) and the extrusion barrel liner (8), so that the upper end surface of the blank (5) can fit with the extrusion rod end (3); Step 2: Assemble the mold, place the blank (5), the extrusion rod (7) and the extrusion rod end (3) into the extrusion cylinder as a whole, then install the guide cylinder (1), and finally install the extrusion rod support pad (9); Step 3: Heat treatment, placing the assembled mold and the blank (5) together in a heating furnace and heating them according to a preset system; Step 4: After the heat treatment, the mold is transferred to the press to start reverse extrusion, and the extrusion rod (7) is driven to press down a specified distance according to the preset parameters to complete the production of the reverse extruded cylindrical part; Step 5: After the mold is cooled, the extruded rod (7), the cylindrical part and the extruded rod end (3) are taken out together, and machined to remove the excess at the bottom of the cylindrical part, and the extruded rod end (3) is separated and taken out to obtain the target pipe.

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