Method for processing variable diameter tube, oil and gas hose fitting and method for manufacturing the same

Abstract

The present application relates to the field of pipe manufacturing, and relates to a variable diameter pipe processing method, an oil and gas hose joint and a manufacturing method thereof, comprising gradient heating of a round pipe, so that the material yield strength of a pipe section to be reduced in diameter of the round pipe is distributed in a gradient along the axial direction of the round pipe, and the gradient direction of the material yield strength is opposite to the diameter reduction direction; the round pipe after gradient heating is sent into a diameter reduction die, the diameter of the round pipe is reduced by the diameter reduction die; the wall thickness change rate of the diameter reduced pipe section is monitored, and the material flow rate is obtained according to a pre-stored wall thickness change rate-material flow rate mapping table; the output pressure of a press is adjusted according to the material flow rate, so that the deformation rate of the diameter reduced pipe section in the diameter reduction die matches the material flow rate. The variable diameter pipe processing method, the oil and gas hose joint and the manufacturing method thereof accurately control the diameter reduction deformation, and improve the concentricity precision of the diameter reduced pipe section and the assembly coaxial consistency of the oil and gas hose joint.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pipe manufacturing, in particular to a variable diameter pipe machining method, an oil and gas hose joint and a manufacturing method thereof. BACKGROUND

[0002] In the field of oil and gas transportation, the structural strength and sealing performance of the hose joint as a key connecting component directly relate to the safety and reliability of the pipeline system. The oil and gas hose joint is usually assembled by a core pipe, a middle sleeve and a side sleeve with a variable diameter pipe segment. The middle sleeve and the side sleeve are coaxially arranged outside the core pipe. This special structure requires the variable diameter pipe segment to have extremely high concentricity accuracy (error needs to be controlled within a few wires) after the diameter reduction machining, so as to ensure that the coaxialities between the side sleeve and the middle sleeve and the core pipe meet the assembly requirements.

[0003] At present, in order to meet the extremely high concentricity accuracy, the variable diameter pipe segment is machined by machining. This machining method will cause material waste and greatly increase the product manufacturing cost. In addition, the variable diameter pipe segment can also be machined by using a pressure fitting diameter reduction die. The pressure machine is used to apply axial pressure to the round pipe, so that the round pipe is plastically deformed under the constraint of the diameter reduction die, thereby reducing the diameter of the pipe. However, the machining method of the traditional pressure machine combined with the diameter reduction die has significant technical bottlenecks. On the one hand, the pressure output of the pressure machine is difficult to accurately control, which easily leads to uneven stress of the variable diameter pipe segment during the diameter reduction process. On the other hand, the structure design of the diameter reduction die has limited ability to suppress the concentricity error, and it is difficult to control the concentricity error within a very small range (within a few wires) in actual machining. This technical limitation makes it difficult for the concentricity accuracy of the variable diameter pipe after machining to meet the assembly requirements of the oil and gas hose joint, which affects the overall performance and service life of the joint. SUMMARY

[0004] Therefore, the purpose of the present application is to overcome the problem that the concentricity of the variable diameter pipe segment machined by the pressure machine combined with the diameter reduction die in the prior art does not meet the requirements, and to provide a variable diameter pipe machining method, an oil and gas hose joint and a manufacturing method thereof, which can accurately control the diameter reduction deformation and improve the concentricity accuracy of the diameter reduction pipe segment and the assembly coaxiality consistency of the oil and gas hose joint.

[0005] In a first aspect, to solve the above technical problems, the present application provides a variable diameter pipe machining method, comprising,

[0006] Gradient heating is performed on the round pipe, so that the material yield strength of the diameter reduction pipe segment of the round pipe is distributed in a gradient along the axial direction of the round pipe, and the gradient direction of the material yield strength is opposite to the diameter reduction direction;

[0007] The round pipe after gradient heating is sent into a diameter reduction die, and the diameter reduction die is used to perform diameter reduction on the round pipe;

[0008] monitoring the wall thickness change rate of the reduced diameter pipe section, and obtaining the material flow rate according to a pre-stored wall thickness change rate-material flow rate mapping table;

[0009] adjusting the output pressure of the press according to the material flow rate, so that the deformation rate of the reduced diameter pipe section in the reducing die matches the material flow rate.

[0010] In an embodiment of the present application, adjusting the output pressure of the press according to the material flow rate, so that the deformation rate of the reduced diameter pipe section in the reducing die matches the material flow rate, comprises obtaining the axial displacement change amount of the reducing die per unit time, and determining the actual deformation rate of the reduced diameter pipe section according to the axial displacement change amount; obtaining the material flow rate according to a pre-stored wall thickness change rate-material flow rate mapping table, taking the material flow rate as the target deformation rate; calculating the difference between the target deformation rate and the actual deformation rate; if the difference is greater than 0, increasing the output pressure of the press; if the difference is less than 0, decreasing the output pressure of the press.

[0011] In an embodiment of the present application, the increasing step of the output pressure of the press is 0.5 MPa; or / and, the decreasing step of the output pressure of the press is 0.3 MPa.

[0012] In an embodiment of the present application, the reduced diameter pipe section of the round pipe is heated by a segmented induction heating system, the segmented induction heating system comprises at least three independently controlled induction coils, each of the induction coils covers the reduced diameter pipe section in sequence along the axial direction; wherein, along the reducing direction of the reduced diameter pipe section, the power of the induction coils gradually increases.

[0013] In an embodiment of the present application, when the reduced diameter pipe section of the round pipe is heated by the segmented induction heating system, the outer wall of the round pipe is wrapped with a ceramic fiber heat insulation sleeve.

[0014] In an embodiment of the present application, the axial temperature difference of the gradient heating is 50 ℃-150 ℃, and the surface temperature T of the reduced diameter pipe section when entering the reducing die satisfies: T≥T0-50 ℃; T0 represents the material recrystallization temperature.

[0015] In an embodiment of the present application, the reducing die comprises a die core and a die sleeve, the taper angle θ of the continuous taper surface of the die core is 5°-15°, the guide taper angle β of the die sleeve is 3°-10°, and θ>β.

[0016] The second aspect, to solve the above technical problems, the present application also provides an oil and gas hose joint, comprising a core pipe, a sleeve pipe and a reducing pipe, the reducing pipe is made by the reducing pipe processing method;

[0017] The sleeve and the variable-diameter pipe are coaxially sleeved outside the core pipe; the sleeve is fixed at the middle part of the core pipe in the axial direction; and the two variable-diameter pipes are fixed at the two sides of the sleeve, respectively.

[0018] In an embodiment of the present application, shoulder parts are symmetrically arranged at the two sides of the sleeve in the axial direction; the sleeve is provided with an extension part outside the shoulder parts in the axial direction; and the shoulder parts and the extension part are transitioned in an inclined manner.

[0019] The end pipe section of the variable-diameter pipe, which is close to the variable-diameter section, is annularly sleeved with the extension part; and the end face of the end pipe section is welded with the sleeve at the inclined transition.

[0020] The variable-diameter pipe has a radial gap with the core pipe; and the variable-diameter section of the variable-diameter pipe and the outer pipe wall of the core pipe form a variable-diameter cavity.

[0021] In a third aspect, to solve the above technical problem, the present application further provides a manufacturing method of an oil and gas hose joint, which is used to manufacture the oil and gas hose joint, and the manufacturing method comprises,

[0022] providing a core pipe;

[0023] providing a sleeve, and operating the sleeve to be coaxially sleeved outside the core pipe and located at the middle part of the core pipe in the axial direction;

[0024] welding the sleeve with the core pipe at the two ends in the axial direction of the sleeve;

[0025] providing a variable-diameter pipe, and operating the variable-diameter pipe to be coaxially sleeved outside the core pipe; and the variable-diameter pipe is annularly sleeved with the extension part by the end pipe section close to the variable-diameter section;

[0026] welding the variable-diameter pipe with the sleeve at the inclined transition.

[0027] The above technical solution of the present application has the following beneficial effects compared with the prior art:

[0028] The variable-diameter pipe processing method, the oil and gas hose joint and the manufacturing method thereof have the following beneficial effects: the concentricity precision of the reduced-diameter pipe section is within ±0.03mm through the synergistic optimization of gradient heating and dynamic pressure control, the technical problem that the concentricity of the reduced-diameter pipe section cannot meet the requirements is solved, the demand of the oil and gas hose joint for high-precision assembly is met, and the overall performance and reliability of the oil and gas hose joint are improved.

[0029] Wherein, the yield strength of the pipe to be reduced in diameter is distributed along the axial direction by gradient heating, and the gradient direction is opposite to the reducing direction, so that the material realizes directional flow control in the reducing process. Compared with the non-heating or uniform heating mode, the problem of too fast thinning on the inside of the reduced pipe segment (close to the mold side) due to compression stress concentration and insufficient thinning on the outside due to stress transmission lag can be effectively avoided, the cross-sectional shape of the reduced pipe is closer to the ideal circle, so that the concentricity error of the reduced pipe segment is controlled within a very small range (such as ±0.02mm), and the coaxiality consistency when assembling with the core pipe and the sleeve is significantly improved.

[0030] Based on the real-time monitoring of the wall thickness change rate, the output pressure of the press is dynamically adjusted, so that the deformation rate of the reduced pipe segment matches the material flow rate. The closed-loop control mechanism can effectively inhibit the problem of excessive local deformation caused by pressure fluctuation or uneven mold gap, avoid the eccentricity phenomenon caused by uneven stress in the reducing process, further guarantee the geometric symmetry of the reduced pipe segment, and meet the strict requirements of oil and gas hose joints on high-precision concentricity. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to make the content of the application more easily understood, the application will be further described in detail below according to the specific embodiments of the application and in conjunction with the drawings.

[0032] Figure 1 The flowchart of the reducing pipe processing method in the preferred embodiment of the application;

[0033] Figure 2 The structure schematic diagram of the reducing pipe processed in the preferred embodiment of the application;

[0034] Figure 3 The flowchart of adjusting the output pressure of the press according to the material flow rate in the preferred embodiment of the application;

[0035] Figure 4 The structure schematic diagram of the oil and gas hose joint in the preferred embodiment of the application;

[0036] Figure 5 The axial cross-sectional schematic diagram of the oil and gas hose joint shown in the figure; Figure 4

[0037] Figure 6 The flowchart of the oil and gas hose joint manufacturing method in the preferred embodiment of the application.

[0038] Explanation of the drawing marks in the specification:

[0039] 2-core pipe; 4-sleeve; 41-shoulder; 42-extension; 43-welding point; 6-reducing pipe; 61-end pipe segment; 8-radial gap; 10-reducing cavity. DETAILED DESCRIPTION ​

[0040] The present application will be further described below in connection with the drawings and specific embodiments so that those skilled in the art can better understand and implement the present application, but the embodiments are not limiting to the present application.

[0041] The purpose of the embodiments of the present application is to solve the problem that the concentricity of the reduced diameter pipe segment machined by the press and the reduced diameter die does not meet the requirements in the prior art. Because this problem has not been solved, the edge sleeve for the oil and gas hose joint can only be manufactured by machining, but the material waste is great by machining manufacturing, resulting in high manufacturing cost.

[0042] Embodiment one: the embodiments of the present application adopt a press and a reduced diameter die to process part of the pipe segment of a circular pipe into a reduced diameter pipe segment, which replaces machining manufacturing to produce the reducing sleeve for the oil and gas hose joint by solving the problem that the concentricity of the reduced diameter pipe segment does not meet the requirements. Referring to Figure 1 The embodiments of the present application disclose a reducing pipe machining method, which comprises,

[0043] S100, gradient heating is performed on the circular pipe, so that the material yield strength of the pipe segment to be reduced of the circular pipe is distributed in a gradient along the axial direction of the circular pipe, and the gradient direction of the material yield strength is opposite to the reducing direction;

[0044] S200, the circular pipe after gradient heating is sent into a reduced diameter die, and the circular pipe is reduced in diameter by the reduced diameter die;

[0045] S300, the wall thickness change rate of the reduced diameter pipe segment is monitored, and the material flow rate is obtained according to the pre-stored wall thickness change rate-material flow rate mapping table;

[0046] S400, the output pressure of the press is adjusted according to the material flow rate, so that the deformation rate of the reduced diameter pipe segment in the reduced diameter die matches the material flow rate.

[0047] In a specific application scenario, before the circular pipe is reduced in diameter by the press and the reduced diameter die, the pipe segment to be reduced in diameter of the circular pipe is heated. The purpose of heating is to change the yield strength of the material. The higher the temperature, the lower the yield strength. The yield strength of the material is the critical stress value when the metal material occurs plastic deformation, that is, the minimum stress required for the material to enter the plastic deformation stage from the elastic deformation stage. The lower the yield strength, the easier the material occurs plastic deformation.

[0048] The purpose of gradient heating is to provide a controllable mechanical environment for subsequent diameter reduction deformation by regulating the yield strength distribution of the material. The gradient direction of the yield strength of the material is opposite to the diameter reduction direction. For example, taking the positive direction of the X-axis as the axial direction of the circular tube, the diameter of the diameter-reduced tube segment obtained after diameter reduction processing gradually decreases from left to right, that is, the left end is the large-diameter end and the right end is the small-diameter end. The yield strength gradually increases from left to right, that is, the yield strength of the small-diameter segment is the lowest and the yield strength of the large-diameter end is the highest. The lower the yield strength, the easier the plastic deformation. Conversely, the higher the yield strength, the less likely the plastic deformation. Specifically, referring to FIG. 9, taking B→A as the diameter reduction direction, the diameter of the position A of the diameter-reduced tube segment is the smallest and the diameter of the position B is the largest. The gradient heating makes the yield strength of the material at the position A the lowest and the plastic deformation the easiest, and the yield strength of the material at the position B the highest and the plastic deformation the least. Figure 2

[0049] The gradient heating makes the yield strength of the diameter-reduced tube segment of the circular tube axially gradient-distributed, and the gradient direction is opposite to the diameter reduction direction, so that the yield strength of the inner side (close to the die side) of the diameter-reduced tube segment is lower and the yield strength of the outer side (far from the die side) is higher. The internal stress difference drives the directional flow of the material, balances the deformation rate inside and outside, and avoids uneven wall thickness. Compared with the non-heating or uniform heating mode, the problems of too fast thinning of the inner side (close to the die side) of the diameter-reduced tube segment due to compression stress concentration and insufficient thinning of the outer side (far from the die side) due to stress transmission lag can be effectively avoided, the cross-sectional shape of the diameter-reduced tube segment is closer to the ideal circle, and thus the concentricity error of the diameter-reduced tube segment is controlled within a very small range (such as ±0.02 mm), and the coaxiality consistency when the diameter-reduced tube segment is assembled with the core tube and the sleeve is significantly improved.

[0050] Subsequently, the circular tube subjected to the gradient heating is sent into a diameter reduction die, and the diameter-reduced tube segment of the circular tube is subjected to controllable plastic deformation under the constraint of the diameter reduction die by cooperation of a press and the diameter reduction die, so as to ensure the uniformity of the wall thickness of the diameter-reduced tube segment.

[0051] During the diameter reduction process, the wall thickness change data of the diameter-reduced tube segment are acquired in real time to provide feedback basis for dynamic pressure regulation. In a specific application scenario, 4-8 distributed optical fiber sensors (such as FBG optical fiber grating sensors) are uniformly arranged in the circumferential direction at the position of the diameter-reduced tube segment corresponding to the diameter reduction die, the sensor spacing is ≤10 mm, and the coverage length is ≥50 mm. The wall thickness of the diameter-reduced tube segment is measured in real time by the optical fiber sensors, the wall thickness change amount per unit time is calculated, and the wall thickness change rate is obtained.

[0052] ​The wall thickness change rate-material flow rate mapping table is established through experiments or simulations, and includes multiple sets of preset wall thickness change rates and corresponding material flow rate data; the material flow rate is extracted from the mapping table according to the obtained wall thickness change rate, and the output pressure of the press is adjusted according to the material flow rate, so that the deformation rate of the reduced diameter pipe section in the reducing die matches the material flow rate.

[0053] It should be noted that the wall thickness change rate is the reduction amount of the wall thickness of the reduced diameter pipe section of the circular pipe per unit time, and the unit is mm / s. The wall thickness data of the reduced diameter pipe section is collected in real time by the distributed optical fiber sensor array, and the wall thickness difference between adjacent time points is calculated as the wall thickness change rate. The material flow rate is the moving speed of the material along the axial direction (reducing direction) of the circular pipe per unit time, that is, the length of the material flowing into the reduced diameter section per unit time, and the unit is mm / s.

[0054] Although gradient heating can preset the yield strength distribution of the material, the material flow rate is dynamically changed in the actual reducing process due to factors such as temperature fluctuations and die friction. By monitoring the wall thickness change rate (reflecting the deformation rate) in real time, the press pressure is dynamically adjusted so that the two always match, avoiding excessive thinning on the inside due to excessive pressure or insufficient thinning on the outside due to insufficient pressure; the yield strength gradient formed by gradient heating provides a basic driving force for material flow, and dynamic pressure regulation further precisely controls the flow direction and rate. The combination of the two makes the wall thickness uniformity of the reduced diameter pipe section reach ±0.02mm.

[0055] On the basis of the above embodiments, with reference to Figure 3 According to the material flow rate, the output pressure of the press is adjusted so that the deformation rate of the reduced diameter pipe section in the reducing die matches the material flow rate, including obtaining the axial displacement change amount of the reducing die per unit time, and determining the actual deformation rate of the reduced diameter pipe section according to the axial displacement change amount; the material flow rate is obtained from the pre-stored wall thickness change rate-material flow rate mapping table, and the material flow rate is taken as the target deformation rate; the difference between the target deformation rate and the actual deformation rate is calculated; if the difference is greater than 0, the output pressure of the press is increased; if the difference is less than 0, the output pressure of the press is decreased.

[0056] In a specific application scenario, when the press cooperates with the reducing die to perform the reducing process, the press moves axially to the circular tube, and the circular tube is constrained to be reduced in diameter by the reducing die. A high-precision linear displacement sensor (such as a magnetostrictive displacement sensor) is installed on the reducing die driving mechanism (such as a hydraulic cylinder or a servo motor screw) of the press, to monitor the axial feeding displacement Δx of the reducing die in real time, and to calculate the feeding rate of the reducing die (i.e. the feeding displacement per unit time) based on the feeding displacement Δx. Since the deformation rate of the circular tube is slightly lower than the feeding rate of the reducing die, a deformation efficiency coefficient λ = 0.8-0.95 is introduced, and the product of the deformation efficiency coefficient and the feeding rate of the reducing die is calculated to obtain the actual deformation rate of the reduced tube section.

[0057] If the difference between the target deformation rate and the actual deformation rate is greater than 0, it indicates that the current deformation rate is too low, and the output pressure of the press is increased. Conversely, if the difference between the target deformation rate and the actual deformation rate is less than 0, it indicates that the current deformation rate is too high, and the output pressure of the press is reduced. If the difference between the two is within a set threshold range (such as ±0.005 mm / s), the current pressure is maintained.

[0058] On the basis of the above embodiments, the increase step of the output pressure of the press is 0.5 MPa; or / and, the decrease step of the output pressure of the press is 0.3 MPa. By adjusting the pressure with a fixed step, the deviation of the material flow rate and the deformation rate can be quickly responded. In addition, the fixed step forms a "stepwise" pressure adjustment, so that the pressure change matches the material flow state, and the wall thickness fluctuation or die impact caused by sudden pressure change is avoided.

[0059] In addition, the optimal combination of the increase step of 0.5 MPa and the decrease step of 0.3 MPa is determined by orthogonal test. The increase step of 0.5 MPa can cover more than 80% of the material flow rate insufficient scenarios; and the decrease step of 0.3 MPa can avoid more than 90% of the risk of excessively thin wall thickness.

[0060] On the basis of the above embodiments, the to-be-reduced tube section of the circular tube is heated by a segmented induction heating system, the segmented induction heating system includes at least three independently controlled induction coils, each of the induction coils sequentially covers the to-be-reduced tube section in the axial direction; wherein, along the reducing direction of the to-be-reduced tube section, the power of the induction coils gradually increases.

[0061] In a specific application scenario, a segmented induction heating system is used to pre-treat the pipe section to be reduced in diameter of the circular pipe. The system includes at least three (preferably three to five) independently controlled induction coils, which are arranged in sequence along the axial direction of the circular pipe, and are respectively a first induction coil, a second induction coil, a third induction coil (and so on). Each coil is controlled by an independent power supply and a temperature closed-loop control module. The first induction coil covers the large-diameter end (i.e., the side that will be thicker after the diameter reduction, corresponding to the outer side); the second induction coil covers the middle of the pipe section; and the third induction coil covers the small-diameter end (i.e., the side that will be thinner after the diameter reduction, corresponding to the inner side). The first induction coil is set to the lowest power to ensure the lowest temperature at the large-diameter end (e.g., power P1); the second induction coil is set to the medium power to achieve a moderate temperature in the middle (e.g., power P2); and the third induction coil (small-diameter end) is set to the highest power to ensure the highest temperature at the small-diameter end (e.g., power P3), with P1 < P2 < P3. The segmented induction heating system independently heats the circular pipe in segments, and the axial temperature distribution can be flexibly set and real-time adjusted as required to meet the optimal matching of the yield strength gradient and the diameter reduction process.

[0062] Further, when the segmented induction heating system is used to heat the pipe section to be reduced in diameter of the circular pipe, the outer wall of the circular pipe is wrapped with a ceramic fiber heat insulation sleeve. The heat insulation performance of the ceramic fiber heat insulation sleeve suppresses radial heat diffusion, establishes a stable axial temperature gradient, reduces external thermal interference, and further regulates the material yield strength distribution to drive directional plastic deformation.

[0063] It should be noted that, in terms of position, the circular pipe is inside, the ceramic fiber heat insulation sleeve wraps the circular pipe, and the induction coil is arranged around the ceramic fiber heat insulation sleeve outside. The number of turns, diameter, and spacing of the induction coil are designed according to the heating power, frequency, and size of the circular pipe.

[0064] On the basis of the above embodiments, the axial temperature difference of the gradient heating is 50 ℃ to 150 ℃, and the surface temperature T of the pipe section to be reduced in diameter when entering the diameter reduction die satisfies T ≥ T0 - 50 ℃; T0 represents the material recrystallization temperature.

[0065] The axial temperature difference refers to the temperature difference between one end and the other end of the pipe section to be reduced in diameter. The axial temperature difference drives the yield strength gradient distribution, balances the deformation rate of the inner and outer walls, and determines the uniformity of the wall thickness. In the high-temperature zone, the atomic diffusion ability is enhanced, the resistance to dislocation movement is reduced, and the yield strength is significantly decreased. In the low-temperature zone, the atomic diffusion ability is weak, the resistance to dislocation movement is high, and the yield strength is close to the original value. An axial temperature difference of 50 ℃ to 150 ℃ can balance the deformation rate and stability. In some scenarios, an axial temperature difference of 100 ℃ provides the best uniformity of the wall thickness of the pipe section to be reduced in diameter, and the service life of the diameter reduction die is significantly improved.

[0066] The surface temperature T refers to the surface temperature of the round tube when the diameter-reducing section enters the diameter-reducing die. Its lower limit is the material recrystallization temperature T0 minus 50°C, which ensures the material's plastic deformation ability, avoids thermal cracking and work hardening, and controls the stability of the microstructure. When T≥T0-50°C, the atomic diffusion capacity is sufficient to support dynamic recrystallization and eliminate work hardening during the diameter reduction process. The resistance to dislocation movement is significantly reduced, and the material flow stress is reduced by 50%~80%.

[0067] In one embodiment of the present invention, the reducing die includes a die core and a die sleeve, the cone angle θ of the continuous cone surface of the die core is 5°~15°, the guide cone angle β of the die sleeve is 3°~10°, and θ>β.

[0068] In specific application scenarios, the continuous cone angle θ of the die core refers to the angle between the cone surface of the compression section of the reduction die and the axial direction. The continuous cone angle θ determines the balance between the axial compression force and radial flow resistance during tube reduction, affecting the uniformity of material flow and die life. By adjusting θ, the ratio of the axial and circumferential components of the metal flow in the tube can be changed, thereby regulating the wall thinning rate and avoiding localized excessive thinning or thickening. When θ is within the range of 5° to 15°, the ratio of the axial and circumferential components of the metal flow in the tube is moderate, forming a stable "shear-extrusion" composite deformation mode, ensuring uniform material flow along the circumference into the reduction section and avoiding wall thickness fluctuations caused by uneven flow.

[0069] The die sleeve's guide taper angle, β, refers to the angle between the die's entrance cone and the axial direction. It determines the initial contact state of the tube as it enters the reduction die, impacting alignment accuracy and deformation stability. Optimizing β reduces friction between the tube and the reduction die, avoiding cracking or wrinkling caused by localized stress concentration. When β is within the 3° to 10° range, the contact area between the tube and the die is moderate, resulting in low friction (friction coefficient μ ≤ 0.15), reducing the risk of surface scratches and improving the finished product's surface quality.

[0070] The core taper angle θ (5°-15°) must be greater than the sleeve guide taper angle β (3°-10°). This ensures a smoother guiding effect at the entry section (sleeve) of the reduction die, while more concentrated deformation occurs in the compression section (core), creating a graded deformation pattern of "guiding first, then compression." Furthermore, a θ > β setting creates a smoother stress gradient within the reduction die, buffering the material flow differences between the inside and outside of the tube and preventing cracking or wrinkling caused by stress concentration.

[0071] Example 2: Reference Figure 4 and Figure 5 As shown, the embodiment of the present invention discloses an oil and gas hose connector, comprising a core tube 2, a sleeve 4 and a reducer 6, wherein the reducer 6 is manufactured by the reducer processing method described above;

[0072] The sleeve pipe 4 and the variable-diameter pipe 6 are coaxially sleeved outside the core pipe 2, wherein the sleeve pipe 4 is fixed at the middle part of the core pipe 2 in the axial direction, and the two variable-diameter pipes 6 are respectively fixed at the two sides of the sleeve pipe 4.

[0073] Specifically, the shoulder part 41 is symmetrically arranged at the two sides of the sleeve pipe 4 in the axial direction, the extension part 42 is arranged at the outer side of the shoulder part 41 in the axial direction of the sleeve pipe 4, and the shoulder part 41 and the extension part 42 are inclinedly transitioned.

[0074] The end pipe section 61 of the variable-diameter pipe 6 is annularly sleeved with the extension part 42 near the variable-diameter section of the variable-diameter pipe 6, and the end surface of the end pipe section 61 is welded with the sleeve pipe 4 at the inclined transition.

[0075] The variable-diameter pipe 6 has a radial gap 8 with the core pipe 2, and the variable-diameter section of the variable-diameter pipe 6 forms a variable-diameter cavity 10 with the outer pipe wall of the core pipe 2.

[0076] The oil and gas hose joint disclosed by the embodiment of the present application is manufactured by the variable-diameter pipe processing method of the first embodiment, and the concentricity precision is within ±0.03 mm, so that the coaxiality precision of the oil and gas hose joint obtained by assembling the core pipe 2, the sleeve pipe 4 and the variable-diameter pipe 6 is significantly improved, and meets the assembly requirements of the oil and gas hose joint.

[0077] Embodiment three: refer to Figure 6 The manufacturing method of the oil and gas hose joint disclosed by the embodiment of the present application is used for manufacturing the oil and gas hose joint, and the manufacturing method comprises,

[0078] Providing a core pipe;

[0079] Providing a sleeve pipe, and coaxially sleeving the sleeve pipe outside the core pipe and arranging the sleeve pipe at the middle part in the axial direction of the core pipe;

[0080] Welding the sleeve pipe and the core pipe at the two ends in the axial direction of the sleeve pipe;

[0081] Providing a variable-diameter pipe, coaxially sleeving the variable-diameter pipe outside the core pipe, and annularly sleeving the end pipe section of the variable-diameter pipe with the extension part near the variable-diameter section of the variable-diameter pipe;

[0082] Welding the variable-diameter pipe and the sleeve pipe at the inclined transition.

[0083] The manufacturing method of the oil and gas hose joint disclosed by the embodiment of the present application is used for manufacturing the oil and gas hose joint, and the manufacturing method comprises,

[0084] Obviously, the above embodiments are merely example for clearly illustrating, and are not limitation to the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and can not be exhausted. The obvious changes or variations derived therefrom are still within the scope of the present invention.

Claims

1. A method of manufacturing a variable diameter tube, characterized by: The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe.

2. The method of manufacturing a variable diameter tube of claim 1, wherein: The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe.

3. The method of manufacturing a variable diameter tube of claim 2, wherein: The application relates to a variable-diameter pipe processing method and a variable-diameter pipe.

4. The method of manufacturing a variable diameter tube of claim 1, wherein: The application relates to a variable-diameter pipe processing method and a variable-diameter pipe.

5. The method of manufacturing a variable diameter tube of claim 4, wherein: The application relates to a variable-diameter pipe processing method and a variable-diameter pipe.

6. The method of manufacturing a variable diameter tube of claim 1 or 4, wherein: The application relates to a variable-diameter pipe processing method and a variable-diameter pipe.

7. The method of manufacturing a variable diameter tube of claim 1, wherein: The application relates to a variable-diameter pipe processing method and a variable-diameter pipe.

8. An oil and gas hose coupling comprising a core tube, a sleeve and a reducer tube, characterised in that: The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe.

9. The oil and gas hose coupling of claim 8, wherein: The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable-diameter pipe. The application relates to a variable-diameter pipe processing method and a variable 10. A method of manufacturing an oil and gas hose coupling for manufacturing an oil and gas hose coupling according to claim 8 or 9, characterized in that: The manufacturing method comprises, providing a core pipe; providing a sleeve pipe, which is coaxially sleeved outside the core pipe and located at the middle part of the core pipe in the axial direction; welding the sleeve pipe and the core pipe at both axial ends of the sleeve pipe; providing a reducing pipe, which is coaxially sleeved outside the core pipe and located at the end pipe section of the reducing pipe close to the extension part; welding the reducing pipe and the sleeve pipe at the inclined transition part.

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