A machined joint and vacuum double-wall tubing and methods of making the same

Abstract

The present application relates to a kind of machining joint and vacuum double-layer pipeline and its preparation method, belong to double-layer pipeline manufacturing technical field, solve the existing conveying pipeline manufacturing cost high, product weight is easy to exceed standard, temperature control effect is not good Problem.Machining joint includes cylindrical body and the protrusion around the part outer periphery of the cylindrical body;Cylindrical body inside is provided with the cavity passing through two end faces;Along the extension direction of cylindrical body central axis, protrusion length is less than the length of cylindrical body, and the both ends of protrusion do not overlap with the both ends of cylindrical body;The both ends of cylindrical body are used to with the inner tube end face of vacuum double-layer pipeline butt joint, the both ends of protrusion are used to with the outer tube end face of vacuum double-layer pipeline butt joint.The vacuum double-layer pipeline method simple, production efficiency high is prepared by using the machining joint of the present application and inner tube, outer tube with corrugated structure is combined.

Description

Technical Field

[0001] The present invention relates to the technical field of double-layer pipeline manufacturing, in particular to a machined joint and a vacuum double-layer pipeline and a preparation method thereof. Background Art

[0002] At present, in the field of precision manufacturing, due to the special requirements of products, there are strict requirements for the temperature control of pipeline transportation systems (the temperature change of the liquid in the pipe does not exceed 20°C within 30 minutes). In the traditional sense, the double-layer pipe has an inner layer as a conveying pipe and an outer layer as a protective sleeve. The annular gap between the inner and outer pipes is filled with thermal insulation material. Its manufacturing cost is high, the product quality is easy to exceed the standard, and the production efficiency is low. In addition, in order to achieve the thermal insulation effect, the thermal insulation cotton is usually wrapped very thickly, which takes up a large space. Summary of the Invention

[0003] In view of the above analysis, the embodiments of the present invention aim to provide a machined joint and a vacuum double-layer pipeline and a preparation method thereof, so as to solve at least one of the problems of existing conveying pipelines, such as high manufacturing cost, low production efficiency, easy excess product weight, and large space occupation.

[0004] In one aspect, the present invention provides a machined joint for a vacuum double-layer pipeline, the machined joint comprising a cylindrical body and a protrusion surrounding a portion of the outer circumference of the cylindrical body; a cavity is provided inside the cylindrical body and passes through both end faces;

[0005] Along the extension direction of the central axis of the cylindrical body, the length of the protrusion is less than the length of the cylindrical body, and the two ends of the protrusion do not overlap with the two ends of the cylindrical body;

[0006] The end surfaces of both ends of the cylindrical body are used to connect with the inner tube end surface of the vacuum double-layer pipeline, and the end surfaces of both ends of the protrusion are used to connect with the outer tube end surface of the vacuum double-layer pipeline.

[0007] Preferably, the first end of the protrusion is close to the first end of the cylindrical body, and the distance between the first end of the protrusion and the first end of the cylindrical body is 3-5 mm;

[0008] The second end of the protrusion is close to the second end of the cylindrical body, and the distance between the second end of the protrusion and the second end of the cylindrical body is 3-5 mm.

[0009] Preferably, the cavity is cylindrical, and the cross-sectional diameter of the cavity is equal to the inner diameter of the inner tube of the vacuum double-layer pipeline.

[0010] Preferably, the wall thickness of the cylindrical body is equal to the thickness of the gap between the inner tube and the outer tube plus the wall thickness of the inner tube.

[0011] Preferably, the thickness of the protrusion is equal to the thickness of the outer tube.

[0012] In a second aspect, the present invention further provides a method for preparing a vacuum double-layer pipeline, using the above-mentioned machined joint, the preparation method comprising:

[0013] (a) preparing an outer tube and an inner tube, wherein the outer tube is provided with a corrugated structure near both ends;

[0014] (b) sleeve-connecting the outer tube to the inner tube;

[0015] (c) bending the sleeved outer tube and the inner tube;

[0016] (d) pressing one end of the outer tube to compress the corrugated structure, welding one end face of the inner tube to one end face of the cylindrical body of the machined joint, and releasing the corrugated structure after welding;

[0017] (e) repeating step (d) to weld the other end face of the inner tube to one end face of the cylindrical body of another machined joint, and releasing the corrugated structure after welding;

[0018] (f) Vacuum weld the end faces of both ends of the outer tube to the end faces of one end of the protrusions of the two machined joints.

[0019] Preferably, step (c) includes: first filling a low-melting-point alloy between the sleeved outer tube and the inner tube and cooling the mixture, then bending the outer tube and the inner tube, and after the bending is completed, removing the low-melting-point alloy.

[0020] Preferably, the welding in step (d) and step (e) is performed by argon arc welding.

[0021] Preferably, the vacuum welding in step (f) is vacuum electron beam welding.

[0022] In a third aspect, the present invention provides a vacuum double-layer pipeline prepared by the above preparation method.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. The machined joint of the present invention is combined with the inner tube and the outer tube with a corrugated structure, and conventional welding and vacuum welding are respectively used to prepare a double-layer tube. Before conventional welding, it is only necessary to compress the corrugated structure of the outer tube to weld the inner tube and the joint, and then loosen the corrugated structure to vacuum weld the outer tube and the joint. The method is simple and speeds up the production efficiency of the double-layer tube.

[0025] 2. The inner tube and outer tube of the vacuum double-layer tube prepared by the method of the present invention are in a vacuum state. Through vacuum insulation, the temperature control of the conveying medium in the inner tube of the double-layer tube can be effectively guaranteed, and the double-layer tube occupies a small space.

[0026] 3. No insulating material needs to be filled between the inner tube and the outer tube of the vacuum double-layer tube of the present invention, which reduces the manufacturing cost. The double-layer tube is lighter and more suitable for use in the field of precision manufacturing.

[0027] 4. The present invention first fills the space between the sleeved outer and inner tubes with a low-melting-point alloy and cools it, then bends the outer and inner tubes. After bending, the low-melting-point alloy is removed. The low-melting-point alloy filling between the inner and outer tubes ensures uniform deformation at all locations during the bending process, thereby improving the consistency of the inner diameter at all locations of the vacuum double-layer pipeline.

[0028] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0030] Figure 1 Schematic diagram of the three-dimensional structure of the machined joint of the present invention;

[0031] Figure 2 is a cross-sectional view of a section of a machined joint of the present invention;

[0032] Figure 3 This is a flow chart of the preparation method of the vacuum double-layer pipeline of the present invention;

[0033] Figure 4 This is a schematic diagram of the outer tube structure of the present invention;

[0034] Figure 5 Schematic diagram of the structure after the low melting point alloy is filled between the outer tube and the inner tube;

[0035] Figure 6 This is a schematic diagram of the structure after the outer tube and inner tube are bent and the low-melting-point alloy is removed;

[0036] Figure 7 Schematic diagram of the structure of the outer tube after the corrugated structure is compressed;

[0037] Figure 8Schematic diagram of the structure after the corrugated structure of the outer tube is released.

[0038] Reference numerals:

[0039] 1-cylindrical body; 101-cavity; 102-first end of the cylindrical body; 103-second end of the cylindrical body; 2-protrusion; 201-first end of the protrusion; 202-second end of the protrusion; 3-inner tube; 4-outer tube; 401-corrugated structure; 5-low melting point alloy. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0041] In one aspect, the present invention provides a machined joint for a vacuum double-layer pipeline, such as Figure 1 and Figure 2 As shown, the machined joint includes a cylindrical body 1 and a protrusion 2 surrounding a portion of the outer circumference of the cylindrical body 1; a cavity 101 is provided inside the cylindrical body 1 and passes through both end faces;

[0042] Along the extension direction of the central axis of the cylindrical body 1, the length of the protrusion 2 is smaller than the length of the cylindrical body 1, and the two ends of the protrusion 2 do not overlap with the two ends of the cylindrical body 1;

[0043] The end faces of the cylindrical body 1 are used to connect with the end faces of the inner tube 3 of the vacuum double-layer pipeline, and the end faces of the protrusion 2 are used to connect with the end faces of the outer tube 4 of the vacuum double-layer pipeline.

[0044] It should be noted that the “end” refers to the end portion, and the “end face” refers to the plane of the end.

[0045] In one embodiment, in order to prevent the welds between the inner tube 3 and the joint and the welds between the outer tube 4 and the joint from interfering with each other when the joint is welded to the inner tube 3 and the outer tube 4, the first end 201 of the protrusion 2 is close to the first end 102 of the cylindrical body 1, and the distance between the first end 201 of the protrusion 2 and the first end 102 of the cylindrical body 1 is 3-5 mm;

[0046] The second end 202 of the protrusion 2 is close to the second end 103 of the cylindrical body 1 , and the distance between the second end 202 of the protrusion 2 and the second end 103 of the cylindrical body 1 is 3-5 mm.

[0047] In the present invention, the cavity 101 of the machined joint is for communicating the pipelines at both ends of the joint.

[0048] In one embodiment, the cavity 101 is cylindrical, and the cross-sectional diameter of the cavity 101 is equal to the inner diameter of the inner tube 3 of the double-layer vacuum pipeline. The cross-sectional diameter of the cavity 101 is equal to the inner diameter of the inner tube 3, thereby preventing obstruction of the conveying medium in the inner tube 3 due to the difference in inner diameter, thereby ensuring smooth flow of the conveying medium.

[0049] In one embodiment, the wall thickness of the cylindrical body 1 is equal to the thickness of the gap between the inner tube 3 and the outer tube 4 plus the wall thickness of the inner tube 3 .

[0050] In one embodiment, the thickness of the protrusion 2 is equal to the wall thickness of the outer tube 4 .

[0051] It can be understood that the sum of the wall thickness of the cylindrical body 1 and the thickness of the protrusion 2 is equal to the sum of the gap thickness between the inner tube 3 and the outer tube 4, the wall thickness of the inner tube 3 and the wall thickness of the outer tube 4, thereby ensuring that the outer surface and inner surface of the double-layer tube formed after the inner tube and the outer tube are respectively welded to the joint are flat.

[0052] In order to improve the welding quality between the joint and the double-layer pipe, the joint and the double-layer pipe are made of the same material.

[0053] In a second aspect, the present invention also provides a method for preparing a vacuum double-layer pipeline, using the above-mentioned machined joint, such as Figure 3 As shown, the preparation method comprises:

[0054] (a) Prepare an outer tube 4 and an inner tube 3. The outer tube 4 is provided with a corrugated structure 401 near both ends. Figure 4 As shown;

[0055] (b) sleeve-connecting the outer tube 4 to the inner tube 3;

[0056] (c) bending the sleeved outer tube 4 and inner tube 3;

[0057] (d) Press one end of the outer tube 4 to compress the corrugated structure 401, and weld one end face of the inner tube 3 to one end face of the cylindrical body 1 of the machined joint, as shown in FIG. Figure 7 As shown, the corrugated structure 401 is released after welding is completed;

[0058] (e) Repeat step (d) to weld the other end face of the inner tube 3 to one end face of the cylindrical body 1 of another machined joint, and release the corrugated structure 401 after welding is completed;

[0059] (f) Vacuum weld the two end faces of the outer tube 4 to the end faces of the protrusions 2 of the two machined joints, respectively. Figure 8 shown.

[0060] It should be noted that the vacuum welding refers to welding in a vacuum environment, that is, before welding, the environment in which the product is located is evacuated, and then welding is performed in a vacuum, so that the enclosed space between the inner tube and the outer tube after welding is vacuum, thereby obtaining a vacuum double-layer tube.

[0061] Compared with the prior art, the machined joint of the present invention is combined with an inner tube and an outer tube with a corrugated structure, and ordinary welding and vacuum welding are respectively used to prepare a double-layer tube. Before ordinary welding, it is only necessary to compress the corrugated structure of the outer tube to weld the inner tube and the joint, and then loosen the corrugated structure to vacuum weld the outer tube and the joint. The method is simple and speeds up the production efficiency of the double-layer tube. The inner tube and the outer tube of the vacuum double-layer tube prepared by the method of the present invention are in a vacuum state. Through vacuum insulation, the temperature control of the conveying medium in the inner tube of the double-layer tube can be effectively guaranteed, and the double-layer tube occupies a small space. The inner tube and the outer tube of the vacuum double-layer tube of the present invention do not need to be filled with insulating material, which reduces the manufacturing cost, and the double-layer tube is lighter and more suitable for use in precision manufacturing fields such as aerospace.

[0062] Specifically, in step (a), the inner diameter of the outer tube 4 is larger than the outer diameter of the inner tube 3. The inner tube 3 can be a straight tube commonly used in the art. The outer tube 4 is a straight tube with a corrugated structure 401 provided near both ends of the tube. The structure of the outer tube 4 is as follows: Figure 4 shown.

[0063] Exemplarily, the corrugated structure 401 of the outer tube 4 can be formed by internal high pressure forming, including: inputting liquid into the tube blank, pressurizing, and using the liquid pressure in the tube blank to expand and then compress the tube until it reflects the required shape, thereby forming the outer tube 4 containing the corrugated structure 401.

[0064] It should be noted that the bending in step (c) refers to bending the outer tube 4 and the inner tube 3 simultaneously.

[0065] For example, after the outer tube 4 is put on the inner tube 3, it is bent into shape using a CNC tube bending machine according to the actual structure of the product.

[0066] In one embodiment, step (c) comprises: first filling the space between the sleeved outer tube 4 and the inner tube 3 with a low melting point alloy 5 and cooling the space to room temperature, such as Figure 5 Then bend the outer tube 4 and the inner tube 3. After the bending is completed, remove the low melting point alloy 5. Figure 6 shown.

[0067] It should be noted that the low-melting-point alloy is in a flowable molten state when filling. After filling, the molten alloy becomes solid by cooling, and then bending is performed. At this time, since the space between the inner tube 3 and the outer tube 4 is filled with solid and no air exists, the inner tube 3 and the outer tube 4 can be deformed evenly during bending.

[0068] In addition, in order to completely fill the space between the inner tube 3 and the outer tube 4 with the low melting point alloy, during implementation, one end of the inner tube 3 and the outer tube 4 can be closed first, and the low melting point alloy can be filled between the inner tube 3 and the outer tube 4 from the other end. After filling, the low melting point alloy can be directly cooled and solidified.

[0069] The present invention first fills a low-melting-point alloy between the sleeved outer and inner tubes, cools the mixture, and then bends the outer and inner tubes. After the bending is complete, the low-melting-point alloy is removed. The low-melting-point alloy filled between the inner and outer tubes ensures uniform deformation at all locations during the bending process, thereby improving the consistency of the inner diameter at all locations in the vacuum double-layer pipeline.

[0070] Illustratively, the low melting point alloy refers to an alloy having a melting point less than 300°C, preferably an alloy having a melting point of 200-300°C.

[0071] For example, the inner tube 3 and the outer tube 4 may be made of stainless steel or aluminum alloy.

[0072] For example, the low melting point alloy is preferably an alloy that is not likely to chemically react with the inner tube 3 and the outer tube 4, such as a lead-tin alloy.

[0073] For example, in order to keep the gap between the outer tube 4 and the inner tube 3 uniform when filling the low-melting-point alloy 5, in step (b), after the outer tube 4 and the inner tube 3 are sleeved, 2-4 rubber blocks are placed around the circumference in the gap between the two ends of the outer tube 4 and the inner tube 3, so that the central axes of the outer tube 4 and the inner tube 3 coincide.

[0074] In one embodiment, removing the low-melting-point alloy 5 includes heating the bent double-layer tube to a temperature higher than the melting point of the low-melting-point alloy 5 so that the low-melting-point alloy 5 melts and flows out of the double-layer tube.

[0075] In order to ensure that the compressed end of the outer tube 4 does not affect the welding of the inner tube and the joint in steps (d) and (e), the corrugated structure 401 of the outer tube 4 must be compressed to completely expose the connection between the inner tube and one end face of the cylindrical body 1 of the joint.

[0076] Exemplarily, the compression amount of the corrugated structure 401 is 10-15 mm.

[0077] In the present invention, the welding in steps (d) and (e) is only for welding the inner tube 3 to one end face of the cylindrical body 1 of the joint. Therefore, the welding in steps (d) and (e) is performed by argon arc welding, and the internal weld is welded manually. At this time, the corrugated structure 401 is in a compressed state.

[0078] In the present invention, the vacuum welding in step (f) is not only performed to weld the outer tube 4 to one end face of the protrusion 2 of the joint, but also to maintain a vacuum between the inner tube 3 and the outer tube 4 of the double-layer tube formed after welding. Therefore, step (f) utilizes vacuum welding to vacuum weld the outer weld seam. At this point, the corrugated structure 401 is in a released and expanded state. Vacuum welding refers to welding performed in a vacuum.

[0079] Exemplarily, the vacuum welding in step (f) is performed by vacuum electron beam welding.

[0080] In order not to affect the welding effect, the parts to be welded are polished before argon arc welding and vacuum electron beam welding to remove the oxide layer and other impurity layers on the parts to be welded.

[0081] It should be noted that a plurality of bent double-layer tubes can be prepared according to steps (a) to (c), and then the plurality of double-layer tubes can be connected together by welding joints according to steps (d) to (f) to form a vacuum double-layer pipeline.

[0082] Specifically, a plurality of double-layer tubes are prepared according to steps (a) to (c), and the two ends of the first double-layer tube are connected to the first ends of the first joint and the second joint respectively according to steps (d) to (f), including: pressing one end of the outer tube 4 to compress the corrugated structure 401, welding one end face of the inner tube 3 to the end face of the first end head 102 of the cylindrical body 1 of the first joint, releasing the corrugated structure 401 after welding, repeating the above steps, welding the other end face of the inner tube 3 to the end face of the first end head 102 of the cylindrical body 1 of the second joint, and releasing the corrugated structure 401 after welding; The end faces of the outer tube 4 are respectively vacuum welded to the end faces of the first end heads 201 of the two machined joints, completing the welding of the two ends of the first double-layer tube to the joint; one end of the second double-layer tube is connected to the second end of the first joint according to the above steps, including: pressing one end of the outer tube 4 to compress the corrugated structure 401, welding the end face of the inner tube 3 to the end face of the second end head 103 of the cylindrical body 1 of the joint, releasing the corrugated structure 401 after welding, and vacuum welding the end face of the outer tube 4 to the end face of the second end head 202 of the protrusion 2, completing the welding of one end of the second double-layer tube to the second end of the first joint. More double-layer tubes are connected in the same way, and the welded joints at both ends of the final double-layer pipeline are ensured to form a vacuum double-layer pipeline of a certain length. No further details will be given here.

[0083] It should be noted that in step (c), the outer tube 4 and the inner tube 3 after being connected can be bent multiple times to form multiple bent portions. However, whether the bending is performed once or multiple times, it is only necessary to provide the corrugated structure 401 near the two ends of the outer tube 4.

[0084] In order to make the inner tube 3 contact with one end surface of the cylindrical body 1 and the outer tube 4 contact with one end surface of the protrusion 2 during welding, the length of the outer tube 4 is greater than that of the inner tube 3 .

[0085] Furthermore, the length by which the two ends of the outer tube 4 extend beyond the two ends of the inner tube 3 is equal to the distance between the end of the protrusion 2 and the end of the cylindrical body 1 adjacent thereto.

[0086] In one embodiment, the preparation method further comprises: leak testing the vacuum double-layer pipeline obtained in step (f) to check whether the welding parts are qualified.

[0087] Specifically, the leak detection includes: weighing the vacuum double-layer pipe after welding (accurate to the last four digits) and recording the weight; immediately after weighing, immersing the vacuum double-layer pipe in aviation kerosene for oil immersion leak detection, taking it out and weighing it after 24 hours, and comparing it with the weight before oil immersion. If the weight increases, it proves that the electron beam weld has leaked, the double-layer pipe is unqualified, and re-welding is required; if the weight does not change before and after, the vacuum double-layer pipe is qualified.

[0088] In a third aspect, the present invention also provides a vacuum double-layer pipe prepared by the above-mentioned preparation method. The vacuum double-layer pipe has a vacuum state between the inner and outer pipes, and the vacuum insulation can effectively ensure the temperature control of the medium transported in the inner pipe of the double-layer pipe.

[0089] The machined joint and vacuum double-layer pipeline of the present invention and their preparation methods are further described below through specific examples.

[0090] Example 1

[0091] A machined joint for a double-layer vacuum pipeline comprises a cylindrical body 1 and a protrusion 2 surrounding a portion of the outer circumference of the cylindrical body 1. A cavity 101 is provided within the cylindrical body 1, extending through both end faces. Along the central axis of the cylindrical body 1, the protrusion 2 is 4 mm long, while the cylindrical body 1 is 10 mm long, and the ends of the protrusion 2 do not overlap with the ends of the cylindrical body 1. The distance between the first end 201 of the protrusion 2 and the first end 102 of the cylindrical body 1 is 3 mm; the distance between the second end 202 of the protrusion 2 and the second end 103 of the cylindrical body 1 is 3 mm. The cavity 101 is cylindrical, with a cross-sectional diameter of 28 mm. The wall thickness of the cylindrical body 1 is 3 mm, while the thickness of the protrusion 2 is 1 mm.

[0092] Example 2

[0093] (a) An outer tube 4 and an inner tube 3 made of steel were prepared. Corrugated structures 401 were formed near both ends of the outer tube 4 by hydroforming (with a compression of 13 mm). The inner tube 3 had an outer diameter (outer diameter) of 30 mm and a wall thickness of 1 mm; the outer tube 4 had an outer diameter (outer diameter) of 36 mm and a wall thickness of 1 mm.

[0094] (b) socketing the outer tube 4 onto the inner tube 3; after the outer tube 4 and the inner tube 3 are socketed, three rubber blocks are placed circumferentially in the gap between the ends of the outer tube 4 and the inner tube 3 so that the central axes of the outer tube 4 and the inner tube 3 coincide with each other;

[0095] (c) First, a low-melting-point alloy 5 (lead-tin alloy, melting point 270°C) is filled between the sleeved outer tube 4 and inner tube 3 and cooled; then, the outer tube 4 and inner tube 3 are simultaneously bent. After the bending is completed, the bent double-layer tube is heated to a temperature higher than the melting point of the low-melting-point alloy 5, causing the low-melting-point alloy 5 to melt and flow out of the double-layer tube;

[0096] (d) pressing one end of the outer tube 4 backward to compress the corrugated structure 401, manually argon arc welding the inner weld of one end face of the inner tube 3 to one end face of the cylindrical body 1 of the machined joint, and releasing the corrugated structure 401 after welding; polishing the welded portion before argon arc welding; the argon arc welding conditions include: a tungsten rod diameter of 1.5 mm, a welding current of 50 A, an arc voltage of 13 V, a gas flow rate of 6 L / min, and a welding wire diameter of 1.5 mm;

[0097] (e) Repeat step (d) to weld the other end face of the inner tube 3 to one end face of the cylindrical body 1 of another machined joint, and release the corrugated structure 401 after welding is completed;

[0098] (f) vacuum electron beam welding the outer welds of the two end faces of the outer tube 4 to the end faces of the protrusions 2 of the two machined joints; polishing the welded areas before vacuum electron beam welding; the vacuum electron beam welding conditions include: an acceleration voltage of 50 kV, an electron beam current of 80 mA, and an electron beam focus diameter of 0.5 mm;

[0099] (g) After welding, weigh the vacuum double-layer pipe (accurate to the last four digits) and record the weight. Immediately after weighing, immerse the vacuum double-layer pipe in aviation kerosene for leak detection. Take it out and weigh it after 24 hours. Compare the weight with the weight before oil immersion. If there is no change in weight, the welding is qualified.

[0100] The vacuum double-layer pipeline obtained in this embodiment has a uniform shape at all locations and a mass per meter of 1.6 kg / m.

[0101] The temperature control effect of the vacuum double-layer pipeline obtained in this embodiment was tested. The method included: filling the inner tube with 70°C test kerosene, building in a temperature sensor, sealing both ends with insulation material, placing it in an environment with a temperature of 200°C, and testing the test liquid temperature. The result was: after 30 minutes, the kerosene temperature did not change by more than 20°C, which met the temperature control requirements for insulation pipes in the precision manufacturing field.

[0102] Example 3

[0103] A double-layer vacuum pipeline was prepared according to the method of Example 2, except that no low-melting-point alloy was filled during bending.

[0104] The vacuum double-layer pipeline obtained in this embodiment has an uneven shape.

[0105] Comparative Example 1

[0106] A double-layer insulation pipe is prepared using an existing method, wherein the inner pipe is a conveying pipe, the outer pipe is a protective casing, and insulation material is placed in the annular gap between the inner pipe and the outer pipe.

[0107] The mass per meter of the double-layer thermal insulation pipeline obtained in this embodiment is 2 kg / m.

[0108] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a vacuum double-layer pipeline, characterized in that: A machined joint is used, the machined joint comprising a cylindrical body (1) and a protrusion (2) surrounding a portion of the outer circumference of the cylindrical body (1); a cavity (101) penetrating both end faces is provided inside the cylindrical body (1); Along the extension direction of the central axis of the cylindrical body (1), the length of the protrusion (2) is less than the length of the cylindrical body (1), and the two ends of the protrusion (2) do not overlap with the two ends of the cylindrical body (1); The end faces of both ends of the cylindrical body (1) are used to connect with the end faces of the inner tube (3) of the vacuum double-layer pipeline, and the end faces of both ends of the protrusion (2) are used to connect with the end faces of the outer tube (4) of the vacuum double-layer pipeline; The preparation method comprises: (a) preparing an outer tube (4) and an inner tube (3), wherein the outer tube (4) is provided with a corrugated structure (401) near both ends; (b) sleeve-connecting the outer tube (4) and the inner tube (3); (c) bending the sleeved outer tube (4) and the inner tube (3); (d) pressing one end of the outer tube (4) to compress the corrugated structure (401), welding one end face of the inner tube (3) to one end face of the cylindrical body (1) of the machined joint, and releasing the corrugated structure (401) after welding is completed; (e) repeating step (d) to weld the other end face of the inner tube (3) to one end face of the cylindrical body (1) of another machined joint, and releasing the corrugated structure (401) after welding is completed; (f) Vacuum welding the end faces of both ends of the outer tube (4) to the end faces of one end of the protrusions (2) of the two machined joints.

2. The preparation method according to claim 1, characterized in that The first end (201) of the protrusion (2) is close to the first end (102) of the cylindrical body (1), and the distance between the first end (201) of the protrusion (2) and the first end (102) of the cylindrical body (1) is 3-5 mm; The second end (202) of the protrusion (2) is close to the second end (103) of the cylindrical body (1), and the distance between the second end (202) of the protrusion (2) and the second end (103) of the cylindrical body (1) is 3-5 mm.

3. The preparation method according to claim 1, characterized in that The cavity (101) is cylindrical, and the cross-sectional diameter of the cavity (101) is equal to the inner diameter of the inner tube (3) of the vacuum double-layer pipeline.

4. The preparation method according to claim 3, characterized in that The wall thickness of the cylindrical body (1) is equal to the thickness of the gap between the inner tube (3) and the outer tube (4) plus the wall thickness of the inner tube (3).

5. The preparation method according to claim 3, characterized in that The thickness of the protrusion (2) is equal to the thickness of the outer tube (4).

6. The preparation method according to claim 1, characterized in that Step (c) comprises: firstly filling a low melting point alloy (5) between the sleeved outer tube (4) and the inner tube (3) and cooling the mixture; then bending the outer tube (4) and the inner tube (3); and after the bending is completed, removing the low melting point alloy (5).

7. The preparation method according to claim 1, characterized in that The welding in step (d) and step (e) adopts argon arc welding.

8. The preparation method according to claim 1, characterized in that The vacuum welding in step (f) adopts vacuum electron beam welding.

9. A vacuum double-layer pipeline prepared according to the preparation method according to any one of claims 1 to 8.

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