A method for forming a small-diameter thick-walled tube by peeling and spinning
Through multiple rounds of powerful spinning processes and specialized equipment, the problems of peeling, bulging, and cracking of small-diameter thick-walled tubes during the spinning process have been solved, achieving high-precision forming at high efficiency and low cost, suitable for medium-batch production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN BOSAI SPINNING TECH CO LTD
- Filing Date
- 2026-03-26
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies suffer from problems such as poor surface quality, high equipment requirements, low processing efficiency, and high costs when processing small-diameter thick-walled tubes. In particular, defects such as peeling, bulging, and cracking are prone to occur during the spinning process, and traditional methods are not suitable for medium-batch production.
Employing a multi-wheel high-power spinning process and equipped with multi-wheel spinning equipment, the design of the blank peeling structure, peeling wheels, and spinning process parameters eliminates the need for intermediate grinding or turning during the spinning process. By utilizing the synergistic effect of the peeling wheels and forming wheels, the surface deformed material is precisely peeled off, ensuring the stability and high precision of the spinning process.
It achieves high-precision forming of small-diameter thick-walled tubes, reduces intermediate processing steps, improves processing efficiency and raw material utilization, reduces equipment and maintenance costs, and meets the high-strength and lightweight requirements of pipelines for aircraft and spacecraft.
Smart Images
Figure CN121893038B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of spinning forming technology, and more specifically, to a method for peeling and spinning small-diameter thick-walled tubes. Background Technology
[0002] With the increasing demands for large carrying capacity and high payload in aircraft and spacecraft, the requirements for lightweighting various pipelines and support connectors are becoming increasingly stringent. Reducing component size and increasing component strength are becoming more urgent, making the application of small-diameter, thick-walled spun tubes a crucial way to meet these needs. Currently, small-diameter, thick-walled tubes are mainly manufactured using rolling, extrusion, and traditional spinning methods. Rolling is suitable for large batches of thick-walled tubes with relatively low dimensional accuracy requirements. Extrusion requires high-tonnage equipment and has high production costs. Spinning of these parts has always resulted in poor surface quality. Grinding or turning the outer surface is necessary between spinning passes to reduce peeling defects; otherwise, the spinning process cannot continue. Without intermediate processing, defects will amplify, leading to material bulging, cracking, and breakage. Intermediate processing increases processing costs and reduces processing efficiency, making it unsuitable for medium-batch production.
[0003] Therefore, a special spinning method is urgently needed to suppress and overcome the peeling defect during the spinning process. In view of this, we propose a peeling-spinning forming method for small-diameter thick-walled tubes. Summary of the Invention
[0004] The purpose of this invention is to provide a peeling-spinning forming method for small-diameter thick-walled tubes to solve the problems mentioned in the background art.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] A method for peeling and spinning small-diameter thick-walled pipes employs a multi-round high-power spinning process. The matching multi-rotor spinning equipment is equipped with forming and peeling rollers. By designing the blank peeling structure, peeling roller tooling parameters, and spinning process parameters, and implementing the spinning process according to specifications, no grinding, turning, or other mechanical processing or polishing of the pipe's outer surface is required between each spinning pass or throughout the entire process. The method includes the following steps:
[0007] Step 1: Spinning blank design. Design the peeling layer structure at the starting position of the blank and determine the key parameters such as peeling depth h1, length before peeling L1, total peeling length L2, and peeling cutting angle α. The peeling depth is 1 / 10-1 / 20 of the raw material thickness, and the peeling depth is negatively correlated with the strength of the raw material.
[0008] Step 2: Design of the peeling roller, including the key structural parameters such as the tilt angle, peeling fillet radius, and peeling cut angle β.
[0009] Step 3: Design spinning parameters. Determine the spinning speed, feed rate, and thinning amount for multiple spinning passes. The thinning amount for multiple passes should be designed according to the principle of average distribution. The thinning rate of each spinning pass should be 23-35%, and the thinning rate of a single pass should not be less than 20% and not more than 40%.
[0010] Step four, the spinning process is carried out, which involves sequentially completing the blank machining, blank installation, machining program preparation, peeling wheel tool setting, axial position adjustment of the spinning wheel and spinning. During the machining process, the peeling wheel peels off the deformed material on the surface of the pipe and collects it, and the forming wheel completes the thinning and forming of the pipe.
[0011] Preferably, the design of the blank peeling layer structure in step one is designed to address the characteristic that the material is prone to peeling defects due to repeated deformation caused by bulging, squeezing, and torsion during the high-pressure spinning initiation stage. The spinning initiation stage is the stage in which the material gradually deforms under the extrusion of the spinning wheel. The design of the peeling cutting angle α needs to meet the requirements of facilitating the intervention of the peeling spinning wheel after the material is deformed, reducing the cutting force of the peeling material, and reducing the wear of the spinning wheel.
[0012] Preferably, the spinning equipment is a horizontal four-wheel spinning equipment, with the four wheels distributed at 90 degrees and fixed to the machine tool frame. The upper and lower wheels are peeling wheels, and the left and right wheels are forming wheels, so as to achieve symmetrical force during the spinning process and reduce the off-center load on the spinning mandrel. The number of peeling wheels and forming wheels can be increased or decreased according to the processing requirements. The more peeling wheels there are, the thinner the material peeled by a single wheel is, the more stable the spinning process is, the less wear the wheels are, and the more coherent and easy-to-collect the peeled iron filings are.
[0013] Preferably, in step two, the tilt angle of the peeling roller is the angle formed by the axis of the peeling roller and the axis of the spinning mandrel. This tilt angle is controlled within 0.5 degrees to facilitate the shoveling of the material and reduce the axial peeling force. The peeling radius R of the peeling roller is selected as 1-2 mm. The peeling cut angle β of the peeling roller is designed to be between 110-150°, and satisfies β≥ the peeling cut angle α of the raw material + 90°.
[0014] Preferably, in step three, the spinning speed is selected as 100-300 r / min. The spinning speed and feed rate are designed to be adapted to the tonnage of the spinning machine. When the tonnage of the spinning machine is large, high speed and high feed parameters are selected, and when the tonnage is small, low speed and low feed parameters are selected.
[0015] Preferably, the thinning amount of the multi-pass spinning in step three follows the principle of average distribution. The thinning rate of the first pass is designed to be 30%, i.e., (t-t1) / t=30%, where t is the thickness of the raw material and t1 is the thickness after the first pass spinning. The thinning rate of a single pass shall not exceed 40% and shall not be less than 20%. If it exceeds 40%, it will easily lead to an increase in material bulging and an increase in the amount of material peeled off by the peeling wheel, which will not only waste raw materials but also easily cause wear or chipping of the wheel. If it is less than 20%, the bulging of the material before deformation will be reduced, and the peeling wheel will not have an obvious effect on inhibiting peeling defects.
[0016] Preferably, in step four, the blank machining is performed by turning the blank on a CNC lathe according to the peeling layer structure designed in step one, and forming the peeling structure.
[0017] Preferably, the specific operation of the peeling roller in step four is as follows: the R-angle of the peeling roller is brought close to the peeling structure of the raw material, and a feeler gauge with a thickness of 0.01-0.1mm is used to check the gap so that the outermost R-angle of the roller is within the length L1 before peeling, and the gap between the R-angle of the roller and the inclined surface of the peeling angle is less than 0.1mm.
[0018] Preferably, the axial position adjustment of the spinning wheels in step four is as follows: first, the axial positions of each stripping spinning wheel are adjusted to be synchronized, then the axial positions of each forming spinning wheel are adjusted to be synchronized, and after the position adjustment is completed, the spinning process is executed.
[0019] Preferably, the negative correlation between the peeling depth and the strength of the raw material in step one is as follows: the lower the strength of the raw material, the greater the amount of material bulging and the more significant the tendency to produce peeling defects during the spinning process, and the greater the peeling depth within the range of 1 / 10-1 / 20 of the raw material thickness; during the processing, the surface deformed material peeled off by the peeling wheel is collected by a material collection device to ensure the stability of the forming wheel spinning process.
[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0021] (1) The method described in this invention addresses the industry pain points of existing rolling, extrusion, and traditional spinning processes for small-diameter thick-walled tubes, such as poor surface quality, high equipment requirements, low processing efficiency, and high costs. Through the systematic design of billets, spinning wheels, and process parameters, and the standardized spinning operation process, a technological breakthrough in the precision and powerful spinning forming of small-diameter thick-walled tubes is achieved. From the source of the process, a billet peeling layer structure is designed to address the high incidence of peeling defects in the spinning stage. Combined with the precise peeling of surface material by the peeling spinning wheel, the generation of surface defects such as peeling, bulging, and cracking during the spinning process is completely suppressed. The symmetrical layout of the spinning wheel, synchronous adjustment, and reasonable thinning rate design effectively reduce the off-center load of the spinning mandrel, ensuring the uniformity of the tube wall thickness and the accuracy of the shape and position. After processing, the tube can meet the high-precision usage requirements without secondary processing. At the same time, the material deformation is uniform during the spinning process, without secondary surface damage caused by intermediate grinding and turning. The surface mechanical properties of the tube are better, which can fully meet the high-strength and lightweight usage requirements of pipelines and connectors in fields such as aircraft and spacecraft.
[0022] (2) It eliminates the need for grinding, turning or polishing of the outer surface of the pipe during each spinning pass and throughout the entire process, directly eliminating the intermediate processing steps of the traditional spinning process and greatly shortening the processing cycle of a single pipe. The spinning speed, feed rate and equipment tonnage are designed to be compatible, taking into account both forming stability and processing speed. Moreover, the process operation is standardized and highly replicable, solving the problem of processing interruption caused by defects in traditional spinning. The processing continuity is greatly improved, perfectly adapting to the processing needs of small diameter thick-walled pipes in medium batches, and making up for the shortcomings of existing through rolling (only suitable for large batches) and extrusion (low processing efficiency). In terms of raw materials, the stripped surface deformed iron filings are continuous, easy to collect, and recyclable. The reasonable thinning rate design avoids waste of raw materials caused by excessive stripping, significantly improving the utilization rate of raw materials. In terms of tooling and equipment, the exclusive structural design of the stripping roller reduces the probability of roller wear and chipping, significantly extending the service life of the roller. At the same time, the symmetrical force design reduces the impact of mandrel off-center load, reducing the maintenance and wear costs of the equipment. In terms of equipment investment, there is no need for large-tonnage special equipment required for extrusion processes. Processing can be achieved by relying on conventional multi-rotor spinning equipment, which greatly reduces the cost of equipment purchase and use. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the peeling and spinning method (cross-sectional view perpendicular to the mandrel centerline).
[0024] Figure 2 Design drawing for raw materials in the peeling and spinning process;
[0025] Figure 3 Design drawing of the peeling spinneret for the peeling spinning method;
[0026] Figure 4This is a schematic diagram of the peeling and spinning forming process.
[0027] The labels in the diagram are as follows: 1. Peeling roller; 2. Forming roller one; 3. Spinning mandrel; 4. Spinning material; 5. Peeling material; 6. Stopping device; φB, outer diameter of raw material; φA, inner diameter of raw material; t, thickness of raw material. Detailed Implementation
[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example
[0029] Please see Figures 1-4 A method for peeling and spinning small-diameter thick-walled pipes is disclosed. This method is applicable to forward or reverse flow spinning of straight cylindrical or small-conical pipe fittings with a nominal diameter less than 70mm and a finished nominal wall thickness greater than 10mm. It employs a multi-wheel high-power spinning process, with a matching multi-wheel spinning equipment equipped with forming and peeling wheels. By designing the blank peeling structure, peeling wheel tooling parameters, and spinning process parameters, and implementing the spinning process according to specifications, no machining or polishing treatment is required on the outer surface of the pipe fitting between spinning passes or throughout the entire spinning process. The method includes the following steps:
[0030] Step 1: Spinning blank design. Design the peeling layer structure at the starting position of the blank. The core is to determine four key parameters: peeling depth h1, length before peeling L1, total peeling length L2, and peeling cutting angle α. The peeling depth is 1 / 10 to 1 / 20 of the raw material thickness, and the peeling depth is negatively correlated with the strength of the raw material.
[0031] Specifically, the design of the billet peeling layer structure addresses the characteristic of the material being prone to peeling defects due to repeated deformation caused by bulging, compression, and torsion during the high-pressure spinning initiation stage. The initiation stage is when the material gradually deforms under the extrusion of the spinning wheel. The design of the peeling entry angle α needs to meet the requirements of facilitating the intervention of the peeling spinning wheel after material deformation, reducing the cutting force on the peeled material, and minimizing spinning wheel wear. This step, through targeted structural design at the billet initiation position, precisely defines the depth of the surface repeated rolling zone, providing a structural foundation for precise peeling by the peeling spinning wheel from the process source. This effectively avoids the problem of peeling defects occurring frequently during the initiation stage. Simultaneously, the reasonable peeling entry angle design reduces the contact impact between the subsequent peeling spinning wheel and the billet, extending the tooling service life.
[0032] The peeling depth is negatively correlated with the strength of the raw material. Specifically, the lower the strength of the raw material, the greater the material bulge and the more significant the tendency for peeling defects to occur during the spinning process. The peeling depth is larger within the range of 1 / 10 to 1 / 20 of the raw material thickness. During the processing, the surface deformed material peeled off by the peeling wheel is collected by a material collection device to ensure the stability of the spinning process of the forming wheel. This depth design principle realizes the process adaptability of raw materials with different strengths. By dynamically adjusting the peeling depth to accurately match the spinning deformation characteristics of the material, the peeling tendency of materials with different strengths is fundamentally suppressed. The timely collection of surface deformed material avoids the peeled iron filings from adhering to the surface of the pipe or being drawn into the spinning process, ensuring the cleanliness of the spinning environment of the forming wheel and further improving the stability of the spinning process.
[0033] Step 2: Design of the peeling roller, including the key structural parameters such as the tilt angle, peeling fillet radius, and peeling cut angle β.
[0034] Specifically, in step two, the tilt angle of the peeling roller is the angle formed by the axis of the peeling roller and the axis of the spinning mandrel. This tilt angle is controlled within 0.5 degrees to facilitate material lifting and reduce axial peeling force. The peeling radius R of the peeling roller is selected as 1-2 mm. The peeling entry angle β of the peeling roller is designed between 110-150°, and satisfies β≥ the raw material peeling entry angle α+90°. This step, with its dedicated structural design for the peeling roller, is the core tooling guarantee for effectively peeling off the surface deformed material: the small tilt angle ensures effective peeling of the surface deformed material. The smooth scooping of the material significantly reduces the axial peeling force, minimizes the axial force offset of the spinning mandrel, and extends the mandrel's service life. The reasonable peeling radius avoids the dual problems of spinning wheel breakage and wear and peeling failure, achieving a balance between effective peeling and tooling durability. The peeling spinning wheel cutting angle design, which is adapted to the blank peeling cutting angle, ensures the precise matching between the peeling spinning wheel and the blank peeling structure, reduces cutting resistance, and achieves smooth and continuous peeling of the surface material, avoiding problems such as material tearing and pipe surface scratches caused by unsuitable cutting angles.
[0035] Step 3: Design spinning parameters. Determine the spinning speed, feed rate, and thinning amount for multiple spinning passes. The thinning amount for multiple passes should be designed according to the principle of average distribution. The thinning rate of each spinning pass should be 23-35%, and the thinning rate of a single pass should not be less than 20% and not more than 40%.
[0036] Specifically, the spinning speed is selected from 100-300 r / min. The spinning speed and feed rate are designed to be adapted to the tonnage of the spinning machine. When the spinning machine has a larger tonnage, a high speed and high feed parameters are selected, and when the tonnage is smaller, a low speed and low feed parameters are selected. This matching design of speed and feed rate takes into account the dual stability of the material separation process and the spinning forming process. It avoids the shaking in the spinning process and uneven wall thickness of the pipe due to the mismatch between parameters and equipment tonnage. It can also reasonably improve the processing efficiency according to the equipment capacity and adapt to the processing needs of medium batch.
[0037] In this multi-pass spinning process, the thinning amount follows an average distribution principle. The first pass's thinning rate is designed to be 30%, i.e., (t-t1) / t=30%, where t is the raw material thickness and t1 is the thickness after the first pass spinning. The single-pass thinning rate must not exceed 40% or be less than 20%. Exceeding 40% easily leads to increased material bulging, resulting in more material being peeled off by the peeling roller, wasting raw materials and causing roller wear or chipping. Below 20%, the bulging before material deformation decreases, and the peeling roller's effect on suppressing peeling defects is not significant. A reasonable thinning rate design is the core process parameter requirement of this method. An average distribution of thinning ensures uniform material deformation, avoiding defects caused by excessive local deformation. 30% The first-pass thinning rate has been empirically verified to control material bulging within a reasonable range while ensuring forming efficiency, thus optimizing the peeling effect of the peeling roller. The upper and lower limits of the single-pass thinning rate not only avoid the waste of raw materials and tooling wear caused by excessive thinning, but also prevent peeling process failure caused by insufficient thinning, achieving synergistic optimization of forming quality, raw material utilization and tooling life.
[0038] Step four, the spinning process is carried out, which involves sequentially completing the blank machining, blank installation, machining program preparation, peeling wheel tool setting, axial position adjustment of the spinning wheel and spinning. During the machining process, the peeling wheel peels off the deformed material on the surface of the pipe and collects it, and the forming wheel completes the thinning and forming of the pipe.
[0039] Specifically, the blank machining involves turning the blank on a CNC lathe according to the peeling layer structure designed in step one, shaping the peeling structure. The precise machining of the blank peeling layer structure by the CNC lathe ensures the accuracy of the blank structure dimensions, providing a blank foundation for the subsequent precise tool setting and effective peeling of the peeling wheel, and avoiding problems such as peeling position deviation and incomplete peeling caused by blank structure errors.
[0040] The specific operation of the peeling roller setting is as follows: the radius (R) of the peeling roller is brought close to the peeling structure of the raw material, and a feeler gauge with a thickness of 0.01-0.1mm is used to check the gap, so that the outermost edge of the roller forming R angle is within the length L1 before peeling, and the gap between the roller R angle and the peeling angle slope is less than 0.1mm. The high-precision setting operation achieves accurate fit between the peeling roller and the blank peeling structure, ensuring the accuracy of peeling depth and peeling position, avoiding problems such as incomplete peeling in some areas and over-peeling of the pipe surface caused by setting errors, thus ensuring the effectiveness of the peeling process from the operational level.
[0041] The axial position adjustment of the spinning wheels is as follows: first, the axial positions of each stripping spinning wheel are adjusted to be synchronized, and then the axial positions of each forming spinning wheel are adjusted to be synchronized. After the position adjustment is completed, the spinning process is executed. The synchronization adjustment of the spinning wheels ensures that the multiple stripping spinning wheels and multiple forming spinning wheels are subjected to uniform force and move synchronously during the spinning process. This avoids defects such as excessive local force on the pipe fittings, uneven wall thickness, and surface ripples caused by asynchronous spinning wheels. At the same time, it reduces the off-center load impact of the spinning mandrel and improves the overall stability of the equipment and tooling.
[0042] The preferred spinning equipment is a horizontal four-wheel spinning machine. The four wheels are distributed at 90 degrees and fixed to the machine tool frame. The upper and lower wheels are peeling wheels, and the left and right wheels are forming wheels, achieving symmetrical force distribution during the spinning process and reducing the eccentric load on the spinning mandrel. The number of peeling and forming wheels can be adjusted according to processing requirements. A higher number of peeling wheels allows for thinner material peeled by each wheel, resulting in a more stable spinning process, less wheel wear, and more continuous and easily collected peeled iron filings. The symmetrical layout of the horizontal four-wheel design ensures stable spinning. The method achieves symmetrical force distribution during the spinning process, significantly reducing the mandrel eccentricity load from the equipment structure level, and ensuring the uniformity of wall thickness and dimensional accuracy of small-diameter thick-walled tubes. The flexible adaptability of the number of spinning wheels allows the process to be adjusted according to different pipe specifications and processing requirements, thus expanding the applicability of the method. At the same time, more stripping spinning wheels can achieve thinner and batch stripping of surface material, further improving the stability of the spinning process, reducing the load on a single spinning wheel, reducing wear, and making it easier to collect continuous iron filings, ensuring a clean processing environment and the continuity of the spinning process. Example
[0043] Using a straight cylindrical 45 steel thick-walled pipe with a nominal diameter of 60mm and a finished nominal wall thickness of 14mm as the processing object, a reverse flow spinning process is adopted, and a horizontal four-wheel spinning equipment is used to complete the processing. By designing the blank peeling structure, peeling wheel tooling parameters, and spinning process parameters, it is possible to achieve that no grinding, turning, or other mechanical processing or polishing treatment is required on the outer surface of the pipe between each spinning pass and throughout the entire spinning process. This effectively suppresses peeling defects during the spinning process, improves the surface quality of the pipe, and enhances processing efficiency. The specific implementation steps of this method are as follows:
[0044] Step 1: Spinning blank design
[0045] In this embodiment, the processing object is a small-diameter thick-walled tube, which falls into the category of tubes that are prone to peeling defects during high-pressure spinning. Therefore, a special peeling layer structure is designed for the starting position of the billet. The core is to determine four key parameters: peeling depth h1, length before peeling L1, total peeling length L2, and peeling cutting angle α. The peeling depth is set to 1 / 10-1 / 20 of the raw material thickness. At the same time, the peeling depth is negatively correlated with the strength of the raw material.
[0046] In this embodiment, the 45 steel billet is in a hot-rolled state with a nominal wall thickness of 20mm. Considering its material strength characteristics (medium strength, moderate bulging during spinning), the peeling depth h1=1mm (1 / 20 of the raw material thickness, which meets the parameter range requirements) is selected. To facilitate the intervention of the peeling roller, reduce the cutting force, and reduce roller wear, the peeling cutting angle α=15° is designed. The design of the peeling length before peeling is L1=15mm and the total peeling length is L2=40mm. The design of this billet peeling layer structure specifically addresses the peeling problem in the starting stage of strong spinning. The starting stage is when the material gradually deforms under the extrusion of the roller. During this stage, the material is prone to peeling defects due to repeated bulging, extrusion, and torsion. The preset peeling layer structure can accurately define the depth of the repeated rolling zone on the surface, providing a structural basis for the subsequent peeling process of the peeling roller.
[0047] The specific implementation requirement that the peeling depth is negatively correlated with the strength of the raw material is as follows: If the 20 steel billet with lower strength is used in this embodiment, the material bulge will be greater and the tendency to produce peeling defects will be more significant during the spinning process. At this time, the peeling depth needs to be adjusted to 1.5-2mm (1 / 10-1 / 13 of the thickness of the raw material); if the 40Cr billet with higher strength is used, the peeling depth can be adjusted to 0.8-1mm to adapt to the spinning deformation characteristics of materials with different strengths.
[0048] Step Two: Design of the Peeling Spinner
[0049] Based on the structural parameters of the blank peeling layer in step one, a special structural design is carried out for the peeling roller of the horizontal four-roller spinning equipment. The core is to determine three key structural parameters: tilt angle, peeling fillet radius R, and peeling cutting angle β. The forming roller adopts a conventional high-strength spinning forming roller structure. The structural design of the peeling roller and the forming roller are compatible to ensure the synergy of the spinning process.
[0050] The peeling roller tilt angle is the angle formed by the axis of the peeling roller and the axis of the spinning mandrel. In this embodiment, it is designed to be 0.3° (controlled within 0.5 degrees). This angle setting facilitates the peeling roller to pick up the surface material of the blank and can effectively reduce the axial peeling force, avoiding the mandrel from being deflected by axial force during the spinning process.
[0051] Peeling radius: In this embodiment, R=1.5mm is selected. This value avoids the problem of the corner radius being too large to achieve effective peeling, and also prevents the problem of the rotating wheel breaking and wearing due to the corner radius being too small.
[0052] Peeling cut angle: In this embodiment, β=120° is designed to meet the design requirement that β≥ raw material peeling cut angle α+90° (15°+90°=105°, 120°≥105°), which is compatible with the blank peeling cut angle and ensures the cutting effect of the peeling roller.
[0053] In this embodiment, the installation and locking device of the peeling roller is matched to prevent the peeling roller from axial and radial displacement during the spinning process, thus ensuring peeling accuracy. Multiple peeling rollers adopt the same structural design parameters to ensure the consistency of symmetrical peeling.
[0054] Step 3: Spinning Parameter Design
[0055] This embodiment employs multi-wheel synchronous spinning. The core spinning parameters are rotation speed, feed rate, and thinning amount of multiple spinning passes. The peeling depth has been preset in step one and will not be adjusted in this step. All parameter designs take into account the stability of the material separation process and the stability of the spinning forming process, adapting to the spinning deformation characteristics of small-diameter thick-walled tubes and the tonnage characteristics of the 50-ton horizontal four-wheel spinning equipment used in this embodiment.
[0056] Rotation speed and feed rate: In this embodiment, the spinning mill has a tonnage of 50 tons, and the spinning speed is selected as 200 r / min (within the range of 100-300 r / min). The feed rate is designed to be 0.2 mm / r to achieve the adaptation of high speed and high feed. If a smaller tonnage spinning mill with a tonnage of less than 30 tons is used, the speed can be adjusted to 120 r / min and the feed rate to 0.1 mm / r.
[0057] Thinning amount and thinning rate: In this embodiment, the raw material wall thickness t=20mm and the finished product wall thickness is 14mm. The forming requirements can be achieved by single-pass high-strength spinning. The thinning amount is designed according to the principle of average distribution. The thinning rate of the first pass is 30%, that is, (t-t1) / t=30% (t1 is the thickness after the first pass spinning, t1=20-20×30%=14mm), which just meets the finished product wall thickness requirements;
[0058] If processing pipes with thicker finished walls (e.g., 16mm, raw material wall thickness 22mm), a two-pass spinning process can be used. The first pass has a thinning rate of 30% (t1=15.4mm), and the second pass has a thinning rate of 22.1% (both within the empirical range of 23-35%). All passes must adhere to the limitation that the single-pass thinning rate should not be less than 20% and not more than 40%. If the single-pass thinning rate exceeds 40%, it will lead to a significant increase in material bulge, resulting in more material being peeled off by the peeling roller, which wastes raw materials and easily causes wear and chipping of the roller. If the single-pass thinning rate is less than 20%, the bulge before material deformation is too small, and the effect of the peeling roller in suppressing peeling defects will be significantly reduced, thus losing the design significance of the peeling process.
[0059] This step involves developing a CNC machining program based on the aforementioned spinning parameters. The program primarily provides control over the spinning trajectory, feed speed, and rotational speed changes of the forming spinning wheel. The peeling spinning wheel maintains a fixed position and rotational speed to achieve synchronous follow-up peeling.
[0060] Step 4: Implementation of the spinning process
[0061] Based on the above blank, spinning wheel, and parameter design, spinning is carried out according to the established process. The blank machining, blank installation, machining program compilation, stripping spinning wheel tool setting, spinning wheel axial position adjustment, and spinning are completed in sequence. During the processing, the stripping spinning wheel completes the stripping and collection of the deformed material on the surface of the pipe fitting, and the forming spinning wheel completes the thinning and forming of the pipe fitting. No machining or polishing treatment is required on the outer surface of the pipe fitting throughout the process.
[0062] Billet machining: The hot-rolled 45 steel billet is clamped on a CNC lathe and precision machined according to the peeling layer structure (h1=1mm, α=15°, L1=15mm, L2=40mm) designed in step one. The peeling layer structure is precisely machined to ensure the dimensional accuracy of the billet's starting position. The form and position tolerance of the billet after machining is controlled within 0.02mm.
[0063] Blank installation: The blank with the processed peel layer structure is fixed on the spinning mandrel of the horizontal four-wheel spinning equipment by a hydraulic chuck using a reverse flow spinning clamping method. The clearance between the blank and the mandrel is controlled at 0.01-0.03mm to prevent the blank from slipping or shifting during the spinning process.
[0064] Processing program compilation: Input the spinning parameters designed in step three (rotation speed 200r / min, feed rate 0.2mm / r, thinning rate 30%) into the equipment CNC system, compile the axial feed and radial extrusion trajectory program of the forming spinning wheel, and save the program after simulating the spinning process without interference.
[0065] Peeling roller setting: In this embodiment, the upper and lower rollers of the horizontal four-roller spinning equipment are peeling rollers, and the left and right rollers are forming rollers. First, the peeling rollers are precisely set: the R angle of the peeling roller is slowly brought closer to the peeling layer structure of the blank. A feeler gauge with a thickness of 0.05mm is used to check the gap. The radial position of the peeling roller is adjusted so that the outermost R angle of the forming roller is within the length L1 (15mm) before peeling, and the gap between the R angle of the roller and the peeling angle slope is less than 0.1mm. After the setting is completed, the radial position of the peeling roller is locked.
[0066] Axial position adjustment of the spinning wheels: Using the fine-tuning device of the equipment, first adjust the axial position of the upper and lower stripping spinning wheels to be completely synchronized, with the synchronization error controlled within 0.01mm. Then adjust the axial position of the left and right forming spinning wheels to be completely synchronized to avoid deformation of the mandrel and uneven wall thickness of the tube during the spinning process. After the position adjustment is completed, lock the axial position of all spinning wheels.
[0067] Spinning: Start the CNC machining program, the spinning mandrel drives the blank to rotate at a speed of 200r / min, the forming wheel performs axial feeding and radial extrusion according to the programmed program, and at the same time the peeling wheel follows to complete the peeling of the deformed material on the surface of the blank. The iron chips generated by peeling are in continuous strips and are collected in real time by the magnetic material collection device matched with the equipment to avoid the iron chips adhering to the surface of the pipe and affecting the forming quality.
[0068] The horizontal four-wheel spinning equipment used in this embodiment has four wheels evenly distributed at 90 degrees and fixed on the machine tool frame. The design of peeling wheels at the top and bottom and forming wheels on the left and right achieves symmetrical force distribution during the spinning process, effectively reducing the off-center load on the spinning mandrel and ensuring the uniformity of wall thickness of small-diameter thick-walled tubes. If processing small-diameter thick-walled tubes with larger diameters (such as 65-70mm), the number of wheels can be adjusted to six (4 peeling wheels + 2 forming wheels). With the increase in the number of peeling wheels, the material peeled by a single wheel is thinner, the spinning process is more stable, the wear of the wheels is greatly reduced, and the peeled iron filings are more coherent and easier to collect.
[0069] Processing effect of this embodiment
[0070] This embodiment uses the above-described peel-spinning forming method to process a 45 steel straight cylindrical thick-walled tube with a nominal diameter of 60mm and a finished wall thickness of 14mm. The outer surface of the tube is free from defects such as peeling, bulging, and cracking. The surface roughness Ra ≤ 1.6μm and the wall thickness uniformity error ≤ 0.05mm, which fully meets the requirements for high-precision small-diameter thick-walled tubes. There are no intermediate grinding or turning processes in the entire processing. The processing time of a single tube is shortened by more than 40% compared with the traditional spinning process, and the raw material utilization rate is increased by 25% (the peeled iron filings can be recycled and there is no grinding loss as in the traditional process). At the same time, the wear of the peeling roller and the forming roller is significantly reduced, and the service life of the equipment and tooling is increased by more than 30%.
[0071] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for peeling and spinning small-diameter thick-walled tubes, applicable to forward or reverse flow spinning of straight cylindrical or small-conical tubes with a nominal diameter less than 70 mm and a finished nominal wall thickness greater than 10 mm, characterized in that, A multi-round high-intensity spinning process is adopted, with matching multi-rotor spinning equipment adapted to set forming and peeling rollers. By designing the blank peeling structure, peeling roller tooling parameters, and spinning process parameters, and implementing the spinning process according to specifications, it is possible to achieve the goal of eliminating the need for grinding, turning, machining, or polishing of the outer surface of the pipe fitting between each spinning pass and throughout the entire spinning process. This method includes the following steps in sequence: Step 1: Spinning blank design. Addressing the issue that materials are prone to peeling defects due to repeated deformation caused by bulging, compression, and torsion during the initial spinning stage of high-pressure spinning, a peeling layer structure is designed at the starting point of the spinning process. Key parameters are determined: peeling depth h1, pre-peeling length L1, total peeling length L2, and peeling entry angle α. The peeling depth is 1 / 10 to 1 / 20 of the raw material thickness, and it is negatively correlated with the raw material strength. Specifically, the lower the raw material strength, the greater the bulging during spinning and the more pronounced the tendency for peeling defects, corresponding to a larger peeling depth within the range of 1 / 10 to 1 / 20 of the raw material thickness. The initial spinning stage is the stage where the material gradually deforms under the extrusion of the spinning wheel. The design of the peeling entry angle α must meet the requirements of facilitating the intervention of the spinning wheel after material deformation, reducing the cutting force on the peeled material, and minimizing wheel wear. Step 2: Design of the peeling roller. This involves designing the key structural parameters of the peeling roller, including its tilt angle, peeling fillet radius R, and peeling entry angle β. The tilt angle of the peeling roller is the angle formed by the axis of the peeling roller and the axis of the spinning mandrel. This tilt angle should be controlled within 0.5 degrees to facilitate material lifting and reduce axial peeling force. The peeling fillet radius R of the peeling roller should be selected as 1-2 mm. The peeling entry angle β of the peeling roller should be designed between 110-150°, and satisfy β ≥ raw material peeling entry angle α + 90°. Step 3: Design spinning parameters. Determine the spinning speed, feed rate, and thinning amount for multiple spinning passes. The thinning amount for multiple passes should be designed according to the principle of average distribution. The thinning rate of each spinning pass should be 23-35%, and the thinning rate of a single pass should not be less than 20% and not more than 40%. Step four, the spinning process is carried out, which involves sequentially completing the blank machining, blank installation, machining program preparation, peeling wheel tool setting, axial position adjustment of the spinning wheel and spinning. During the machining process, the peeling wheel peels off the deformed material on the surface of the pipe and collects it, and the forming wheel completes the thinning and forming of the pipe.
2. The method for peeling and spinning small-diameter thick-walled tubes according to claim 1, characterized in that: The spinning equipment is a horizontal four-wheel spinning equipment. The four wheels are distributed at 90 degrees and fixed to the machine tool frame. The upper and lower wheels are peeling wheels, and the left and right wheels are forming wheels, which realizes symmetrical force during the spinning process and reduces the off-center load on the spinning mandrel. The number of peeling wheels and forming wheels can be increased or decreased according to processing requirements. The more peeling wheels there are, the thinner the material peeled by a single wheel is, the more stable the spinning process is, the less wear the wheels are made, and the peeled iron filings are more continuous and easier to collect.
3. The method for peeling and spinning small-diameter thick-walled tubes according to claim 1, characterized in that: In step three, the spinning speed is selected as 100-300 r / min. The spinning speed and feed rate are designed to be adapted to the tonnage of the spinning machine. When the tonnage of the spinning machine is large, high speed and high feed parameters are selected, and when the tonnage is small, low speed and low feed parameters are selected.
4. The method for peeling and spinning small-diameter thick-walled tubes according to claim 1, characterized in that: In step three, the thinning amount of the multi-pass spinning follows the principle of average distribution. The thinning rate of the first pass is designed to be 30%, i.e., (t-t1) / t=30%, where t is the thickness of the raw material and t1 is the thickness after the first pass spinning. The thinning rate of a single pass shall not exceed 40% and shall not be less than 20%. If it exceeds 40%, it will easily lead to an increase in material bulging and an increase in the amount of material peeled off by the peeling wheel, which will not only waste raw materials but also easily cause wear or chipping of the wheel. If it is less than 20%, the bulging of the material before deformation will be reduced, and the peeling wheel will not have an obvious effect on inhibiting peeling defects.
5. The method for peeling and spinning small-diameter thick-walled tubes according to claim 1, characterized in that: The blank machining described in step four involves turning the blank on a CNC lathe according to the peeling layer structure designed in step one, and shaping the peeling structure.
6. The method for peeling and spinning a small-diameter thick-walled tube according to claim 1, characterized in that: The specific operation of the peeling roller blade setting in step four is as follows: bring the R-angle of the peeling roller close to the peeling structure of the raw material, use a feeler gauge with a thickness of 0.01-0.1mm to check the gap, so that the outermost R-angle of the roller is within the length L1 before peeling, and the gap between the R-angle of the roller and the inclined surface of the peeling angle is less than 0.1mm.
7. The method for peeling and spinning small-diameter thick-walled tubes according to claim 1, characterized in that: The axial position adjustment of the spinning wheels in step four is as follows: first, adjust the axial position of each stripping spinning wheel to be synchronized, then adjust the axial position of each forming spinning wheel to be synchronized. After the position adjustment is completed, the spinning process is executed.
8. The method for peeling and spinning a small-diameter thick-walled tube according to claim 1, characterized in that: The negative correlation between the peeling depth and the strength of the raw material mentioned in step one is as follows: the lower the strength of the raw material, the greater the amount of material bulging and the more significant the tendency to produce peeling defects during the spinning process. The peeling depth is larger in the range of 1 / 10-1 / 20 of the raw material thickness. During the processing, the surface deformed material peeled off by the peeling wheel is collected by the material collection device to ensure the stability of the forming wheel spinning process.