Welding-free integrated straightening forming method for two ends of corrugated pipe

Abstract

According to the non-welding integrated straightening forming method for the two ends of the corrugated pipe, a middle corrugated section of the corrugated pipe is fixed through a profiling clamp, a curved surface clamping part of the middle corrugated section is matched with a waveform, and stable clamping is ensured through an anti-skid structure; secondly, the two ends of the corrugated pipe are stretched step by step through a power driving mechanism, a straight section integrated with a middle corrugated section is formed, and a smooth and convergent gradual transition area is naturally formed at the connecting position; and finally, the straight section is subjected to aftertreatment such as radial bulging, shaping, 45-degree inner chamfering and polishing, so that the flatness of the end face of the straight section is smaller than or equal to 0.1 mm, and the 90-degree bending frequency of the corrugated pipe is larger than or equal to 150 times. Through a welding-free integrated forming process, welding defects are avoided, stress concentration is eliminated, the liquid leakage risk is reduced, the original performance of materials is reserved, meanwhile, the machining efficiency and precision are improved, and the liquid cooling pipe connector is suitable for the pipeline connection requirement of high-end liquid cooling equipment.

Description

Technical Field

[0001] The present application relates to the technical field of metal bellows processing, and in particular to a method for straightening and forming a bellows without welding at both ends. Background Art

[0002] In the field of liquid cooling and heat dissipation technology, stainless steel bellows are widely used for coolant pipe connections due to their flexibility and corrosion resistance. In existing technologies, straight sections are usually formed at both ends of the bellows to achieve a sealed connection with the joints. However, traditional processes generally use laser welding or vacuum brazing to weld the prefabricated straight sections to the ends of the bellows. This welding process has the following significant drawbacks:

[0003] 1. Risk of leakage due to welding defects: Microscopic defects such as pores and cracks are easily generated during the welding process. Under the pressure fluctuations of the liquid cooling system, the defects may expand to form leakage points. Especially under dynamic working conditions such as 90-degree bending, the fatigue strength of the welded joints is insufficient, resulting in a significant increase in the probability of leakage.

[0004] 2. Deterioration of material properties: High welding temperature will change the metallographic structure of stainless steel, resulting in decreased corrosion resistance of the welding area. It is prone to rust during long-term use, affecting pipeline reliability.

[0005] 3. Appearance and processing efficiency issues: Additional surface treatment is required after welding to cover the weld marks, which not only increases the process cost, but also makes it difficult to ensure the flatness of the end face, affecting the subsequent assembly accuracy.

[0006] Therefore, how to provide a welding-free, high-precision method for forming both ends of a bellows to achieve one-piece forming of the straight section and the corrugated section while ensuring the mechanical properties and appearance quality of the transition zone has become a technical problem that needs to be urgently solved in this field. Summary of the Invention

[0007] The present application aims to solve one of the technical problems in the related art at least to a certain extent.

[0008] To this end, one of the purposes of this application is to provide a method for straightening and forming the two ends of a bellows without welding, realizing the integrated forming of the straight section and the corrugated section through a non-welding process, solving the problems of leakage, insufficient strength and poor appearance caused by the existing welding process, and improving the reliability and processing efficiency of the bellows in the liquid cooling system.

[0009] To achieve the above-mentioned purpose, the first embodiment of the present application proposes a method for straightening and forming a corrugated pipe without welding at both ends, comprising the following steps:

[0010] S1. Place the bellows on the machine and clamp the middle corrugated section of the bellows with a profiling fixture. The profiling fixture consists of four split semicircular clamping blocks that, when closed, form a curved clamping portion that matches the waveform of the bellows. The inside of the clamping portion has an anti-slip structure. The machine tool indirectly fixes the bellows by clamping the profiling fixture.

[0011] S2. Use a power drive mechanism to stretch the ends of the bellows in steps:

[0012] S2a. The two semicircular clamping blocks at one end of the bellows are connected to the power drive mechanism, and the two semicircular clamping blocks at the other end remain stationary, applying axial tension to the connecting end to form a continuous straight section at the end;

[0013] S2b replace the bellows fixed position, repeat step S2a to stretch the other end;

[0014] S3. The straight sections at both ends are subjected to radial expansion, synchronous shaping of the inner and outer contours, inner chamfering and surface polishing in sequence to form an integrated structure without welding seams.

[0015] The embodiment of the present application provides a method for straightening and forming the two ends of a bellows without welding, which realizes the integrated forming of the straight section and the corrugated section through a non-welding process, solves the problems of leakage, insufficient strength and poor appearance caused by the existing welding process, and improves the reliability and processing efficiency of the bellows in the liquid cooling system.

[0016] In addition, the method for straightening and forming a corrugated pipe without welding at both ends proposed in the present application may also have the following additional technical features:

[0017] In one embodiment of the present application, in step S2a: the power drive mechanism is a cylinder, and only a single corrugated segment is fixed during stretching at each end, the stretching force is 5-15 kN, and a gradual transition zone is formed at the connection between the straight segment and the corrugated segment.

[0018] In one embodiment of the present application, in step S3, the radial bulging process is performed by expanding the straight section radially by a bulging tool, and the bulging amount is controlled to be 5%-8% of the tube diameter.

[0019] In one embodiment of the present application, a non-welded corrugated pipe product: the middle corrugated section and the straight sections at both ends are an integrally formed structure, the cross-sectional profile of the gradual transition zone at the connection is a smooth convergent shape, the flatness of the straight section end face is ≤0.1mm and has a 45° inner chamfer, and the number of 90-degree bends is ≥150 times.

[0020] The advantages of this application compared with the existing technology are:

[0021] (1) Through the non-welding one-piece molding process, defects such as pores and cracks in the traditional welding process are avoided; the gradual transition zone at the connection between the straight section and the middle corrugated section is a smooth convergent shape, which effectively eliminates stress concentration, so that the bellows can still maintain structural integrity under 90-degree bending conditions (bending times ≥ 150 times), greatly reducing the risk of leakage in the liquid cooling system.

[0022] (2) The non-welding process retains the original metallographic structure of stainless steel, avoids the degradation of material properties caused by high-temperature welding, fundamentally solves the problem of easy rust in the welding area, and significantly improves the long-term reliability of the bellows.

[0023] (3) Eliminate welding and weld mark post-processing processes, reduce processing steps, and improve the overall pipe manufacturing yield; after post-processing, the flatness of the straight section is ≤0.1mm and has a 45° inner chamfer. The surface finish meets the assembly and appearance requirements of high-end liquid cooling equipment, while reducing process costs.

[0024] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0026] Figure 1 This is a product schematic diagram of a method for straightening and forming a corrugated pipe without welding at both ends according to an embodiment of the present application;

[0027] Figure 2 This is a product schematic diagram of a method for straightening and forming a corrugated pipe without welding at both ends according to another embodiment of the present application;

[0028] Figure 3 A schematic diagram of a profiling fixture for a method of straightening and forming a corrugated pipe without welding at both ends according to an embodiment of the present application;

[0029] Figure 4 The present invention is a schematic diagram of the steps of a method for straightening and forming a corrugated pipe without welding at both ends according to an embodiment of the present application.

[0030] As shown in the figure: 1. Contour clamp; 11. Curved clamping part; 12. Anti-slip structure; 2. Corrugated section; 3. Power drive mechanism; 4. Straight section; 21. Gradual transition zone; 31. Bulging tool. DETAILED DESCRIPTION

[0031] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application and are not to be construed as limiting the present application. On the contrary, the embodiments of the present application include all variations, modifications, and equivalents that fall within the spirit and scope of the appended claims.

[0032] The following describes a method for straightening and forming a corrugated pipe without welding at both ends in one piece according to an embodiment of the present application with reference to the accompanying drawings.

[0033] like Figures 1-4 As shown, the specific implementation of this application is described in detail below.

[0034] Bellows diameter: DN4 (4MM) - DN10 (10MM), wave pitch 1.2MM - 2.5MM, wall thickness 0.12MM - 0.2MM.

[0035] Example: Taking a 316L stainless steel corrugated pipe with a diameter of DN8 and a material thickness of 0.18mm as an example (wave pitch 2.0mm), the complete processing flow is as follows:

[0036] S1. Positioning of profiling fixture and fixing of bellows protection

[0037] Clamp Structure: The contouring fixture 1 consists of four split, semicircular clamping blocks (two upper and two lower). When closed, they form a curved clamping section 11 that precisely matches the corrugated pipe's waveform. A grid-like anti-slip structure 12 is incorporated into the clamping section. For a 2.0mm corrugation pitch, the grid protrusion height is 0.08mm, and the depth of the embedded gap in the wave trough is ≥0.07mm (suitable for small-pitch corrugations).

[0038] Protecting fixed processes:

[0039] Place the third corrugated section 2 in the middle of the bellows into the curved groove of the lower clamping block;

[0040] Close the upper clamping block and lock the four clamping blocks with the buckle to form a complete package;

[0041] The machine tool clamp only clamps the positioning boss outside the profiling fixture 1 to avoid direct contact with the surface of the bellows to prevent clamping damage (the clamping force is controlled at 0.5kN-0.8kN to avoid excessive squeezing).

[0042] S2. Step-by-step single-end stretch forming

[0043] Stretching device: The power drive mechanism 3 adopts an air cylinder or an oil cylinder, and the output end is connected to a special bellows chuck, which has a built-in split semicircular clamping block (clamping surface accuracy ±0.02mm) that is the same as the fixture.

[0044] Step-by-step process:

[0045] S2a. Left end stretch:

[0046] Insert the first corrugated section at the left end of the bellows into the clamping block of the power end chuck and lock it;

[0047] The right clamping block remains stationary (fixed to the machine tool base, static friction force ≥ 5kN);

[0048] The cylinder applies axial tension to 3 kN (suitable for 0.18 mm wall thickness) at a rate of 1.5 kN / s, maintains pressure for 10 seconds, and extends the left end to form a straight section 4 with a length of 20 mm, while generating a gradual transition zone 21.

[0049] S2b. Right end stretch:

[0050] Release the right side fixation and insert the right end corrugated section into the power end chuck;

[0051] The straight section 4 that was originally stretched on the left side was changed to be fixed at the static end (the fixing stability was enhanced by auxiliary tooling);

[0052] Repeat the stretching operation to form the straight segment on the right end.

[0053] The step-by-step stretching avoids the superposition of bidirectional stresses, and the cross-sectional convergence shape of the transition zone 21 is smoother (the curvature radius R ≥ 1.0 mm, adapted to small wave distance).

[0054] S3. Precision post-processing of straight sections (through CNC lathe)

[0055] (It should be noted that the CNC lathe tool set is existing technology, with tools No. 1 to No. 5 respectively installed on the top, and the tool accuracy level is IT5).

[0056] Tool No. 1: Cut off the clamping sections at both ends (the parts that were not extended during the original stretching), leaving a straight section length of 20±0.1mm;

[0057] Tool No. 2 (bulging tool 31): The hydraulic bulging die injection pressure is 5 MPa (fluctuation range ≤ ± 0.2 MPa), which expands the inner diameter of the straight section from 7.0 mm to 7.5 mm (bulging amount 5.7%).

[0058] Tool No. 3: A composite tool simultaneously trims the inner and outer contours of the straight section—turning the outer diameter to 8.0±0.03mm and boring the inner diameter to 6.8±0.03mm (spindle speed 2500r / min, feed rate 0.04mm / r);

[0059] Tool No. 4: A special chamfering tool processes a 45° internal chamfer with a depth of 0.8mm along the straight end (chamfer surface roughness Ra ≤ 1.6μm);

[0060] Tool No. 5: Use the flexible shaft polishing wheel to polish the outer surface of the straight section, with a roughness of Ra ≤ 0.6 μm (polishing time 30s-40s).

[0061] Product performance verification

[0062] Gradual transition zone 21: the cross-sectional diameter changes from the peak of the corrugation section to the peak of the corrugation section. Smooth convergence to a straight segment (convergence length 3.0mm, 1.5 times the wave pitch), no stress concentration point;

[0063] Straight section accuracy: end face flatness 0.04mm (laser interferometer detection, detection range covers the entire end face), inner chamfer angle 45±1°;

[0064] Bending life: A dedicated testing machine performs 90° bending at a frequency of 1 time / second, with a support distance of 80mm (10 times the pipe diameter). No cracks or leakage are observed after 165 times (far exceeding the requirement of ≥150 times).

[0065] Example: Specific implementation of step S2a

[0066] Workflow:

[0067] 1. Cylinder drive mechanism

[0068] The power drive mechanism 3 uses an air or oil cylinder as its power source, with the cylinder piston rod rigidly connected to the chuck via a connector. When compressed air (pressure 0.3-0.5 MPa, stable output error ≤±0.02 MPa) pushes the piston, the piston rod retracts linearly at a rate of 2 mm / s, generating an axial tensile force of 1.5-4 kN (corresponding to a bellows wall thickness of 0.15-0.2 mm, with a 0.18 mm wall thickness corresponding to 3 kN).

[0069] 2. Single corrugated segment fixed operation

[0070] The stretched end of the bellows is only embedded in a single corrugated segment (such as the first corrugated segment 2 at the left end), and the clamping structure holds the single wave crest tightly to ensure that the clamping force is concentrated on a complete waveform (when the wave pitch is 2.0mm, the clamping width is 2.5±0.03mm).

[0071] 3. Formation principle of gradual transition zone 21

[0072] Under the action of cylinder pulling force, the crest and trough materials of corrugated section 2 extend axially:

[0073] The crest part (curvature radius R = 0.5 mm) is subjected to radial pressure, and the metal flows in the axial direction;

[0074] The trough area (curvature radius R = 1.0 mm) is dominated by tensile stress;

[0075] The double stress field coupling makes the connection area form a gradual transition zone 21 with a length of 3.0 mm, and the cross-sectional diameter changes from the peak of the corrugated section to the peak of the corrugated section. Linear convergence to straight segment 4 (convergence angle 2.1°), the cross-sectional profile curvature is continuous without sudden changes (verified by 3D scanning, the curvature derivative change rate is ≤0.04 / mm).

[0076] Specific implementation of step S3

[0077] Radial bulging processing

[0078] Bulging tool 31 execution process:

[0079] ① Place the straight segment 4 in the split-type cavity of the bulging tool 31. The initial inner diameter of the cavity is equal to the outer diameter of the straight segment (8.0 mm, tolerance ±0.01 mm);

[0080] ②The hydraulic system drives the conical mandrel to advance 3mm axially (mandrel cone angle 24°), and the split die expands radially;

[0081] ③ Bulging amount control: The expansion amount ΔD is strictly set according to 5%-8% of the pipe diameter (ΔD = 0.4-0.64mm for DN8 pipe, 0.5mm in this embodiment), and is accurately controlled (error ≤ ± 0.01mm) through the geometric relationship between the core shaft displacement s and the radial expansion amount d (d = s × tan12°).

[0082] In one embodiment of the present application, Figures 1-4 As shown, the middle corrugated section 2 and the straight sections 4 at both ends are an integrally formed structure, the cross-sectional profile of the gradual transition zone 21 at the connection is smoothly convergent, the end face flatness of the straight section 4 is ≤0.1mm and has a 45° inner chamfer, and the number of 90-degree bends is ≥150 times.

[0083] In the specific implementation process, the integrally formed structure of the middle corrugated section 2 and the straight sections 4 at both ends is achieved through the following process:

[0084] First, the middle corrugated section 2 is positioned and fixed using a profiling fixture 1. The curved clamping portion 11 of the profiling fixture 1 precisely matches the corrugated tube's waveform (corrugation fit ≥ 95%). The inner anti-slip structure 12 fits into the gaps between the troughs, ensuring that the middle corrugated section 2 is rigidly positioned in both the axial and radial directions (radial displacement ≤ 0.03mm). Subsequently, a power drive mechanism 3 applies axial tension to both ends of the corrugated tube. Under this tension, the material at both ends of the middle corrugated section 2 expands axially (at a rate of 0.5mm / s-1mm / s), gradually forming the straight sections 4 at both ends. This entire process requires no welding, resulting in the middle corrugated section 2 and the straight sections 4 forming a continuous, integrated structure.

[0085] The smooth convergence shape of the gradual transition zone 21 at the connection is formed during the stretching process of the straight section 4 and the middle corrugated section 2. When the power drive mechanism 3 applies axial tension, the tension size matches the thickness of the bellows material (0.12mm wall thickness corresponds to 1.5kN-2kN, 0.2mm wall thickness corresponds to 4kN-5kN), and the stretching rate is controlled at 5mm / s, so that the crest and trough materials of the corrugated section 2 are uniformly extended along the axial direction. The crest is subjected to radial pressure and the trough is subjected to tensile stress. Under the coupling of the two stress fields, the connection area naturally forms a gradual transition zone 21, and its cross-sectional profile changes from the crest diameter of the middle corrugated section 2 (such as ) smoothly converges to the diameter of straight segment 4 (such as ), the convergence length (such as 3.0mm) is ≥1.5 times the corrugation pitch, the cross-sectional profile curvature is continuous without mutation, and the curvature derivative change rate is ≤0.04 / mm to ensure uniform stress distribution.

[0086] Achieving a flatness of ≤0.1mm and a 45° internal chamfer on the end face of straight segment 4 relies on post-processing in S3. During CNC lathe machining, tool No. 1 first removes the unextended portion of straight segment 4, followed by tool No. 3, which simultaneously reshapes the inner and outer contours of straight segment 4. The lathe spindle speed is set at 2000-3000 rpm (adjusted according to the straight segment diameter: DN8 corresponds to 2500 rpm), with a feed rate of 0.04mm / r. Ceramic inserts (hardness HRC 60-62) are used to ensure a flat end face of straight segment 4. Next, tool No. 4 (a dedicated chamfering cutter) creates a 45° internal chamfer with a depth of 1.0mm along the end of straight segment 4 (the angle is controlled at 45±1°). After machining, high-precision flatness testing instruments, such as laser interferometers, confirm that the end face flatness of straight segment 4 can reach 0.05mm, meeting the ≤0.1mm requirement.

[0087] The performance of 150 or more 90-degree bends was verified using a dedicated testing machine: the formed bellows was fixed to the testing machine with the support spacing set to 10 times the bellows diameter (e.g., 80 mm for an 8 mm diameter). 90-degree reciprocating bends were performed at a frequency of 1 per second (bending radius ≥ 5 times the tube diameter). During the bending process, because the intermediate corrugated section 2 and the straight section 4 are integrally formed, the gradual transition zone 21 effectively eliminates stress concentration, providing structural stability for the straight section 4 and transition zone 21. Testing showed that the bellows could be bent up to 165 times without cracking or leakage, meeting the 150 or more requirement.

[0088] In summary, a method for straightening and forming a bellows without welding at both ends in an embodiment of the present application realizes the integrated forming of the straight section and the corrugated section through a non-welding process, solves the problems of leakage, insufficient strength and poor appearance caused by the existing welding process, and improves the reliability and processing efficiency of the bellows in the liquid cooling system.

[0089] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0090] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0091] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and deform the above embodiments within the scope of the present application.

Claims

1. A method for straightening and forming a corrugated pipe without welding at both ends, characterized in that: The following steps are involved: S1. Place the bellows on a machine tool and clamp the middle corrugated section (2) of the bellows with a profiling fixture (1). The profiling fixture (1) comprises four split semicircular clamping blocks, which, when closed, form a curved clamping portion (11) that matches the waveform of the bellows. The inner side of the clamping portion is provided with an anti-slip structure (12). The machine tool indirectly fixes the bellows by clamping the profiling fixture (1). S2. Use the power drive mechanism (3) to stretch the two ends of the corrugated tube in steps: S2a. The two semicircular clamping blocks at one end of the bellows are connected to the power drive mechanism (3), and the two semicircular clamping blocks at the other end remain stationary, applying axial tension to the connecting end to form a continuous straight section (4); S2b replace the bellows fixed position, repeat step S2a to stretch the other end; S3. The straight sections (4) at both ends are subjected to radial expansion, synchronous shaping of the inner and outer contours, inner chamfering and surface polishing in sequence to form an integrated structure without welding seams.

2. A method for straightening and forming a corrugated pipe without welding at both ends according to claim 1, characterized in that: In step S2a: The power drive mechanism (3) is a cylinder; When each end is stretched, only a single corrugated segment is fixed, and the tensile force is 5-15kN; A gradual transition zone (21) is formed at the connection between the straight section (4) and the corrugated section (2).

3. A method for straightening and forming a corrugated pipe without welding at both ends according to claim 1, characterized in that: In step S3, radial bulging is performed by expanding the straight section (4) radially through a bulging tool (31), and the bulging amount is controlled within 5%-8% of the tube diameter.

4. A weld-free corrugated pipe product, manufactured by the method according to any one of claims 1 to 3, characterized in that: The middle corrugated section (2) and the straight sections (4) at both ends are an integrally formed structure; The cross-sectional profile of the gradual transition zone (21) at the connection is in a smooth convergent shape; The end face flatness of the straight section (4) is ≤0.1 mm and has a 45° inner chamfer, and the number of 90-degree bends is ≥150 times.

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