Local thermal strengthening method and device for improving the crush resistance of large pipelines

Abstract

The present invention provides a method and device for local thermal strengthening to improve the crush resistance of large pipeline pipes. The specific steps are as follows: using axial or circumferential induction heating coils to perform axial or circumferential local thermal strengthening on the large pipeline pipe to be strengthened, respectively; feeding the large pipeline pipe under the control of a control box; and controlling the heating temperature of the induction heating coils in real time based on feedback from the temperature sensor to determine whether the current heating step has ended. If the current heating step has ended, thermal strengthening of subsequent sections of the large pipeline pipe to be strengthened is continued until the axial or circumferential local thermal strengthening of the entire large pipeline pipe is completed. In the thermal strengthening device, the axial induction heating coils are evenly distributed along the circumference of the large pipeline pipe, and the circumferential induction heating coils are evenly distributed along the axial direction of the large pipeline pipe. The present invention improves the compressive yield strength and compressive mechanical properties of the axial and circumferential thermal strengthening zones of the large pipeline pipe, thereby improving the crush resistance of the large pipeline pipe.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical property control of large-scale pipelines, and in particular to a local thermal strengthening method and device thereof for improving the crush resistance of large-scale pipelines. Background Art

[0002] Large-scale line pipes are essential tools for the extraction and transportation of energy sources such as oil and natural gas in deep-sea environments. They must withstand the high pressures and complex combined loads of deepwater environments. Therefore, their crush resistance is a key indicator of their service environment. Considering factors such as material deformation strengthening, the encapsulation effect, and the complexity of the strain paths involved in the large-scale line pipe forming process, mechanical properties such as elastic modulus and compressive yield strength decrease during the manufacturing process. Furthermore, given the uneven distribution of residual stress across the cross-section of large-scale line pipes, improving their crush resistance is becoming increasingly important. Heat treatment is a key method for improving the overall mechanical properties of large-scale line pipes.

[0003] Compared with traditional overall thermal strengthening of large pipelines, the present invention proposes a localized thermal strengthening method for improving the axial and circumferential crush resistance of large pipelines. This method involves both axial and circumferential localized thermal strengthening of large pipelines. While improving the crush resistance of pipelines, it reduces dependence on large-scale heat treatment equipment, resulting in simpler and more efficient thermal strengthening equipment. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides a local thermal strengthening method and device for improving the crush resistance of large pipelines. The method mainly performs local thermal strengthening in the axial and circumferential directions of large pipelines to improve the crush resistance of large pipelines. The axial induction heating coil is arranged along the circumference of the large pipeline to be strengthened with a gap G. a Evenly distribute the circumferential induction heating coil along the axial direction of the large pipeline to be strengthened with a gap of G c The heat is evenly distributed, and based on the feedback information from the temperature sensor, the heating temperature of the induction heating coil is controlled in real time and whether the current heating step is completed is determined, thereby completing the axial local thermal strengthening and circumferential local thermal strengthening of the entire large pipeline pipe, so as to improve the compressive yield strength and compressive mechanical properties of the axial and circumferential sections of the large pipeline pipe, thereby improving the overall anti-crush performance of the large pipeline pipe. It has the advantages of simple processing equipment, simple production process, low energy consumption and high efficiency.

[0005] The present invention provides a local thermal strengthening method for improving the crush resistance of large pipelines. The specific implementation steps are as follows:

[0006] S1. Initialize the thermal strengthening device.

[0007] S2. Use axial induction heating coils or circumferential induction heating coils to perform axial local thermal strengthening or circumferential local thermal strengthening on the large pipeline to be strengthened:

[0008] The axial induction heating coil is placed along the circumference of the large pipeline to be strengthened with a gap G a Evenly distributed, the number of axial induction heating coils N a Satisfies the following expression:

[0009] L a =N a (W a +G a )

[0010] Where, L a is the circumference of the large pipeline to be strengthened, G a is the gap between the axial induction heating coils, N a is the number of axial induction heating coils, W a is the width of the axial induction heating coil.

[0011] The circumferential induction heating coil is placed along the axial direction of the large pipeline to be strengthened with a gap G c The number of circumferential induction heating coils N is uniformly distributed. c Satisfies the following expression:

[0012] L c =(N c W c +(N c -1)G c )N'

[0013] Where, L c is the axial length of the large pipeline to be strengthened, G c is the gap between the circumferential induction heating coils, N c is the number of circumferential induction heating coils, W c is the width of the circumferential induction heating coil, and N' is the number of heating steps for the large line pipe to be strengthened.

[0014] S3. Determine the length of each heating step as L' based on the length of the large pipeline to be strengthened, and perform local thermal strengthening in units of heating steps:

[0015] S31 , starting the motor and controlling the rotation speed of the motor to move the large pipeline pipe to be strengthened at a feed speed V, so that the large pipeline pipe to be strengthened moves forward for one heating step and then stops moving.

[0016] S32. When the temperature sensor detects that the temperature of the axial heat-strengthening zone or the circumferential heat-strengthening zone of the large pipeline to be strengthened reaches T0±20°C, the control box controls the heating temperature of the axial induction heating coil or the circumferential induction heating coil to maintain the temperature of the axial heat-strengthening zone or the circumferential heat-strengthening zone of the large pipeline to be strengthened at T0±20°C for M minutes, thereby completing the axial localized heat strengthening or the circumferential localized heat strengthening of the large pipeline to be strengthened in this heating step.

[0017] S33. When the axial localized thermal strengthening or circumferential localized thermal strengthening of the heating step in step S32 is completed, the motor is started again to move the large pipeline pipe to be strengthened forward for one heating step and then stop, and step S32 is repeated to perform axial localized thermal strengthening or circumferential localized thermal strengthening on the remaining portion of the large pipeline pipe to be strengthened.

[0018] S4. Cut compression specimens from the local heat strengthened areas of the large pipeline pipe to be strengthened and the axially locally heat strengthened large pipeline pipe and the circumferentially locally heat strengthened large pipeline pipe obtained in S3, respectively. Perform compression tests on a universal material testing machine, and draw stress-strain curves of the local heat strengthened areas of the large pipeline pipe to be strengthened, the axially locally heat strengthened large pipeline pipe, and the circumferentially locally heat strengthened large pipeline pipe, respectively.

[0019] S5. Based on the stress-strain curves of the large pipeline pipe obtained in S4, the deformation of the large pipeline pipe to be strengthened, the axially locally heat-strengthened large pipeline pipe, and the circumferentially locally heat-strengthened large pipeline pipe under the same external pressure load and boundary conditions are analyzed by simulation software, and the corresponding crushing pressure is calculated. The specific calculation expression of the crushing pressure of the large pipeline pipe is as follows:

[0020] {P c -P e}{P c 2 -P p 2 =P c P e P p f o D / h

[0021] Among them, P c is the crushing pressure of large line pipe, P e is the elastic rupture pressure, its value is 2E(h / D) 3 / (1-ν 2 ), E is the elastic modulus of the large pipeline pipe, h is the wall thickness of the large pipeline pipe, D is the nominal outer diameter of the large pipeline pipe, ν is the Poisson's ratio, P p is the plastic fracture pressure, and its value is 2f y αh / D,f yis the yield strength of large-scale pipeline pipe, α is the manufacturing coefficient of large-scale pipeline pipe, f o is the ovality of large line pipe.

[0022] Preferably, the specific steps of initializing the thermal strengthening device in step S1 are as follows:

[0023] S11. Determine the strengthening direction of the large pipeline to be strengthened;

[0024] S12, placing the large pipeline to be strengthened on the active roller and the driven roller;

[0025] S13. Start the lifting hydraulic cylinder through the control box so that the large pipeline to be strengthened is in a concentric configuration with the axial induction heating coil or the circumferential induction heating coil.

[0026] Preferably, the curvature radius of the cross section of the axial induction heating coil is 30 mm to 50 mm larger than the curvature radius of the outer surface of the large pipeline pipe to be strengthened; the curvature radius of the cross section of the circumferential induction heating coil is 30 mm to 50 mm larger than the curvature radius of the outer surface of the large pipeline pipe to be strengthened.

[0027] Preferably, the gap G between the axial induction heating coils is a Meet 3W a <<G a <<6W a , the width W of the axial induction heating coil a The value range is 20mm-50mm.

[0028] Preferably, the gap G between the circumferential induction heating coils is c Meet 5W c <<G c <<8W c , the width W of the circumferential induction heating coil c The value range is 100mm-200mm.

[0029] Another aspect of the present invention provides a localized thermal strengthening device for improving the crush resistance of large pipeline pipes. The device comprises an axial induction heating coil, an axial induction heating coil support, a temperature sensor, a circumferential induction heating coil, and a circumferential induction heating coil support. The axial induction heating coil is evenly distributed along the circumference of the large pipeline pipe to be strengthened, and the circumferential induction heating coil is evenly distributed along the axial direction of the large pipeline pipe to be strengthened. The temperature sensor is connected to the mounting end of the induction heating coil support.

[0030] Preferably, it also includes a control box, a motor, a main transmission sprocket, a slave transmission sprocket, a transmission chain, an active roller, a driven roller, a lifting hydraulic cylinder, a base and a frame, the first mounting end of the lifting hydraulic cylinder is fixedly connected to the base, the second mounting end of the lifting hydraulic cylinder is connected to the first mounting end of the frame, the fixed ends of the active roller and the driven roller are respectively connected to the second mounting end and the third mounting end of the frame, the input shafts of the active roller and the driven roller are respectively connected to the output end of the main transmission sprocket and the output end of the slave transmission sprocket, the input end of the main transmission sprocket is connected to the output end of the motor, the main transmission sprocket is connected to the slave transmission sprocket through a transmission chain, and the control box is respectively connected to the motor and the control end of the temperature sensor.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. This invention performs localized heat treatment on the axial and circumferential sections of the pipeline to improve the compressive yield strength and compressive mechanical properties of these sections, thereby enhancing the pipeline's crush resistance. The compressive mechanical properties of the axial and circumferential localized heat-strengthened zones of large-scale pipelines are significantly enhanced. This invention offers advantages such as simple processing equipment, a simple production process, low energy consumption, and high efficiency, making it widely applicable to large-diameter pipelines in the oil and gas industry.

[0033] 2. The present invention is applicable to axial or circumferential local thermal strengthening of large pipelines with a diameter greater than 200 mm. According to the diameter of the pipeline, the appropriate axial induction heating coil or circumferential induction heating coil is selected to improve the heating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A flow chart of a local thermal strengthening method for improving the crush resistance of large line pipes according to the present invention;

[0035] Figure 2A and Figure 2B This is a structural diagram of the device for axial local thermal strengthening and circumferential local thermal strengthening in the local thermal strengthening method for improving the crush resistance of large pipelines according to the present invention;

[0036] Figure 3A and Figure 3B Schematic diagram of axial local thermal strengthening and circumferential local thermal strengthening of a large pipeline pipe in the initial heating step of the local thermal strengthening method for improving the crush resistance of the large pipeline pipe according to the present invention;

[0037] Figure 4A and Figure 4B Schematic diagram of axial local thermal strengthening and circumferential local thermal strengthening of a large pipeline pipe in an intermediate heating step in a local thermal strengthening method for improving the crush resistance of a large pipeline pipe according to the present invention;

[0038] Figure 5 The stress-strain curves of the large pipeline pipe to be strengthened, the circumferential heat-strengthened zone of the circumferentially locally heat-strengthened large pipeline pipe, and the axial heat-strengthened zone of the axially locally heat-strengthened large pipeline pipe in the local heat-strengthening method for improving the crush resistance of the large pipeline pipe according to the present invention;

[0039] Figure 6A and Figure 6B This is a distribution diagram of the enhanced axial mechanical properties of a large pipeline after axial local thermal strengthening in the local thermal strengthening method for improving the crush resistance of a large pipeline according to the present invention;

[0040] Figure 6C This is a distribution diagram of the circumferential mechanical property enhancement areas of a large pipeline after circumferential local thermal strengthening in the local thermal strengthening method for improving the crush resistance of a large pipeline according to the present invention;

[0041] Figure 7A 、 Figure 7B and Figure 7C Deformation diagrams of the axially locally thermally strengthened large pipeline pipe, the circumferentially locally thermally strengthened large pipeline pipe, and the large pipeline pipe to be strengthened, obtained based on ABAQUS numerical simulation when the external pressure load is 10 MPa according to the local thermal strengthening method for improving the crush resistance of large pipeline pipes of the present invention.

[0042] Main reference numerals:

[0043] Control box 1, motor 2, main drive sprocket 3, active roller 4, drive chain 5, slave drive sprocket 6, driven roller 7, lifting hydraulic cylinder 8, base 9, frame 10, large pipeline pipe to be strengthened 11, axial induction heating coil 12, axial induction heating coil bracket 13, temperature sensor 14, circumferential induction heating coil 15, circumferential induction heating coil bracket 16, axially locally heat strengthened large pipeline pipe 17, circumferentially locally heat strengthened large pipeline pipe 18. DETAILED DESCRIPTION

[0044] To fully describe the technical content, objectives and effects of the present invention, the following will be described in detail with reference to the accompanying drawings.

[0045] The local heat strengthening method used to improve the crush resistance of large pipelines includes axial local heat strengthening method and circumferential local heat strengthening method. Both methods use induction heating process to improve the residual stress distribution inside the large pipelines and improve the phenomenon of reduced compressive yield strength during the manufacturing process of large pipelines. In the axial local heat strengthening method, there are N a The width is W aThe axial induction heating coil 12 improves the compressive yield strength and compressive mechanical properties of the axial heat-strengthening zone of the corresponding large pipeline pipe 11 to be strengthened; in the circumferential local heat strengthening method, there are N c The width is W c The circumferential induction heating coil 15 improves the compressive yield strength and compressive mechanical properties of the circumferential heat-strengthening zone of the corresponding large pipeline 11 to be strengthened. Figure 1 The specific implementation steps are as follows:

[0046] S1. Initialize the thermal strengthening device.

[0047] S11. Determine the strengthening direction of the large pipeline 11 to be strengthened.

[0048] S12, placing the large pipeline pipe 11 to be strengthened on the active roller 4 and the driven roller 7.

[0049] S13. Start the lifting hydraulic cylinder 8 through the control box 1 so that the large pipeline pipe to be strengthened 11 and the axial induction heating coil 12 or the circumferential induction heating coil 15 are in a concentric configuration state to ensure uniform heating of the large pipeline pipe to be strengthened 11.

[0050] S2. Performing axial local thermal strengthening or circumferential local thermal strengthening on the large line pipe 11 to be strengthened by using the axial induction heating coil 12 or the circumferential induction heating coil 15.

[0051] Furthermore, the size, number, and distribution of the axial induction heating coils 12 and the circumferential induction heating coils 15 are determined based on the geometric parameters of the large line pipe 11 to be strengthened:

[0052] Specifically, the curvature radius of the cross section of the axial induction heating coil 12 is 30mm-50mm larger than the curvature radius of the outer surface of the large pipeline pipe 11 to be strengthened; the curvature radius of the cross section of the circumferential induction heating coil 15 is 30mm-50mm larger than the curvature radius of the outer surface of the large pipeline pipe 11 to be strengthened.

[0053] The gap G between the axial induction heating coils 12 a Meet 3W a <<G a <<6W a , the width W of the axial induction heating coil 12 a The value range of is 20mm-50mm. The gap G between the circumferential induction heating coils 15 c Meet 5W c <<G c <<8W c , the width W of the circumferential induction heating coil 15 cThe value range is 100mm-200mm.

[0054] The axial induction heating coil 12 is placed along the circumference of the large pipeline pipe 11 to be strengthened with a gap G a Uniform distribution, the number N of axial induction heating coils 12 a Satisfies the following expression:

[0055] L a =N a (W a +G a )

[0056] Where, L a is the circumference of the large line pipe 11 to be strengthened, G a N is the gap between the axial induction heating coils 12, a is the number of axial induction heating coils 12, W a is the width of the axial induction heating coil 12.

[0057] The circumferential induction heating coil 15 is placed along the axial direction of the large pipeline pipe 11 to be strengthened with a gap G c Evenly distributed, the number N of circumferential induction heating coils 15 c Satisfies the following expression:

[0058] L c =(N c W c +(N c -1)G c )N'

[0059] Where, L c is the axial length of the large line pipe 11 to be strengthened, G c N is the gap between the circumferential induction heating coils 15, c is the number of circumferential induction heating coils 15, W c is the width of the circumferential induction heating coil 15, and N' is the number of heating steps for the large line pipe 11 to be strengthened, which is generally 5-6 times.

[0060] S3. Determine the length of each heating step as L' according to the length of the large pipeline 11 to be strengthened, and perform local thermal strengthening in units of heating steps.

[0061] S31 , starting the motor 2 and controlling the rotation speed of the motor 2 to move the large pipeline pipe 11 to be strengthened at a feed speed V, so that the large pipeline pipe 11 to be strengthened moves forward for one heating step and then stops moving.

[0062] S32. When the temperature sensor 14 detects that the temperature of the axial heat-strengthening zone or the circumferential heat-strengthening zone of the large-scale pipeline pipe 11 to be strengthened reaches T0±20°C, the control box 1 controls the heating temperature of the axial induction heating coil 12 or the circumferential induction heating coil 15 to ensure that the temperature of the axial heat-strengthening zone or the circumferential heat-strengthening zone of the large-scale pipeline pipe 11 to be strengthened is maintained at T0±20°C for M minutes, thereby completing the axial local heat strengthening or the circumferential local heat strengthening of the large-scale pipeline pipe 11 to be strengthened in this heating step.

[0063] S33. When the axial localized thermal strengthening or the circumferential localized thermal strengthening of the heating step in step S32 is completed, the motor 2 is started again to move the large pipeline pipe 11 to be strengthened forward for one heating step and then stop, and step S32 is repeated to perform axial localized thermal strengthening or circumferential localized thermal strengthening on the remaining portion of the large pipeline pipe 11 to be strengthened.

[0064] S4. Compression specimens are cut from the local heat-strengthened areas of the large pipeline pipe to be strengthened 11 and the axially locally heat-strengthened large pipeline pipe 17 and the circumferentially locally heat-strengthened large pipeline pipe 18 obtained in S3, respectively. Compression tests are performed on a universal material testing machine, and stress-strain curves of the local heat-strengthened areas of the large pipeline pipe to be strengthened 11, the axially locally heat-strengthened large pipeline pipe 17, and the circumferentially locally heat-strengthened large pipeline pipe 18 are plotted, respectively.

[0065] S5. Based on the stress-strain curves of the large pipeline pipe obtained in S4, the deformation of the large pipeline pipe to be strengthened 11, the axially locally thermally strengthened large pipeline pipe 17, and the circumferentially locally thermally strengthened large pipeline pipe 18 under the same external pressure load and boundary conditions are analyzed using finite element simulation software, and the crushing pressure of the large pipeline pipe to be strengthened 11, the axially locally thermally strengthened large pipeline pipe 17, and the circumferentially locally thermally strengthened large pipeline pipe 18 is calculated. The specific expression for calculating the crushing pressure of the large pipeline pipe is as follows:

[0066] {P c -P e}{P c 2 -P p 2 =P c P e P p f o D / h

[0067] Among them, P c is the crushing pressure of large line pipe, P e is the elastic rupture pressure, its value is 2E(h / D) 3 / (1-ν 2), E is the elastic modulus of the large pipeline pipe, h is the wall thickness of the large pipeline pipe, D is the nominal outer diameter of the large pipeline pipe, ν is the Poisson's ratio, P p is the plastic fracture pressure, and its value is 2f y αh / D,f y is the yield strength of large-scale pipeline pipe, α is the manufacturing coefficient of large-scale pipeline pipe, f o is the ovality of large line pipe.

[0068] In a preferred embodiment of the present invention, a local thermal strengthening device for improving the crush resistance of large pipelines is provided. Figure 2A As shown, it includes an axial induction heating coil 12, an axial induction heating coil bracket 13, a temperature sensor 14, a circumferential induction heating coil 15 and a circumferential induction heating coil bracket 16. The axial induction heating coil 12 is evenly distributed along the circumference of the large pipeline pipe 11 to be strengthened, and the temperature sensor 14 is connected to the mounting end of the axial induction heating coil bracket 13. The circumferential induction heating coil 15 is evenly distributed along the axial direction of the large pipeline pipe 11 to be strengthened, and the temperature sensor 14 is connected to the mounting end of the circumferential induction heating coil bracket 16.

[0069] like Figure 2B As shown, the local thermal strengthening device of the present invention also includes a control box 1, a motor 2, a main transmission sprocket 3, a slave transmission sprocket 6, a transmission chain 5, an active roller 4, a driven roller 7, a lifting hydraulic cylinder 8, a base 9 and a frame 10. The first mounting end of the lifting hydraulic cylinder 8 is fixedly connected to the base 9, the second mounting end of the lifting hydraulic cylinder 8 is connected to the first mounting end of the frame 10, the fixed ends of the active roller 4 and the driven roller 7 are respectively connected to the second mounting end and the third mounting end of the frame 10, the fixed end of the motor 2 is fixedly connected to the fourth mounting end of the frame 10, the input shafts of the active roller 4 and the driven roller 7 are respectively connected to the output end of the main transmission sprocket 3 and the output end of the slave transmission sprocket 6, the input end of the main transmission sprocket 3 is connected to the output end of the motor 2, the main transmission sprocket 3 is connected to the slave transmission sprocket 6 through the transmission chain 5, and the control box 1 is respectively connected to the motor 2 and the control end of the temperature sensor 14.

[0070] The following further describes a local thermal strengthening method for improving the crush resistance of large pipelines according to the present invention with reference to an embodiment:

[0071] In this embodiment, the outer surface circumference L of the large pipeline 11 to be strengthened c 1300mm, axial length L a The specific implementation process of the local thermal strengthening method is as follows:

[0072] S1. Initialize the thermal strengthening device.

[0073] S11. Determine the strengthening direction of the large pipeline 11 to be strengthened.

[0074] S12, placing the large pipeline pipe 11 to be strengthened on the active roller 4 and the driven roller 7.

[0075] S13. Start the lifting hydraulic cylinder 8 through the control box 1 so that the large pipeline pipe to be strengthened 11 and the axial induction heating coil 12 or the circumferential induction heating coil 15 are in a concentric configuration state to ensure uniform heating of the large pipeline pipe to be strengthened 11.

[0076] S2. Performing axial local thermal strengthening or circumferential local thermal strengthening on the large line pipe 11 to be strengthened by using the axial induction heating coil 12 or the circumferential induction heating coil 15.

[0077] In the local thermal strengthening method of this embodiment, the distance between the axial induction heating coil 12 and the outer surface of the large pipeline pipe 11 to be strengthened is 30 mm, and the width W of the axial induction heating coil 12 is 10 mm. a 100mm, quantity N a is 4, the gap between adjacent a The distance between the circumferential induction heating coil 15 and the outer surface of the large pipeline pipe 11 to be strengthened is 40 mm, and the width W of the circumferential induction heating coil 15 is 500 mm. c 40mm, quantity N c is 8, and the gap between adjacent c The thickness is 122.5 mm and is evenly distributed along the axial direction of the large-scale pipeline 11 to be strengthened.

[0078] S3. According to the length of the large pipeline 11 to be strengthened, the length L' of each heating step is determined to be 2 m, and local thermal strengthening is performed in units of heating steps.

[0079] S31. Start the motor 2 connected to the active roller 4 via the main drive sprocket 3. Control the speed of the motor 2 via the control box 1 so that the large pipeline pipe 11 to be strengthened moves at a feed speed V of 1 m / min. The large pipeline pipe 11 to be strengthened moves forward for one heating step and then stops.

[0080] S32. The axial induction heating coil 12 or the circumferential induction heating coil 15 is started to heat up through the control box 1. When the temperature sensor 14 detects that the temperature of the circumferential heat strengthening zone or the axial heat strengthening zone of the large pipeline pipe 11 to be strengthened reaches 300±20 (°C), the heating temperature of the axial induction heating coil 12 or the circumferential induction heating coil 15 is controlled through the control box 1 to ensure that the temperature of the axial heat strengthening zone or the circumferential heat strengthening zone of the large pipeline pipe 11 to be strengthened is maintained at 300±20 (°C) for 10 minutes, thereby completing the axial local heat strengthening or the circumferential local heat strengthening of the large pipeline pipe 11 to be strengthened in this heating step, respectively. Figure 3A and Figure 3B As shown;

[0081] S33, when the axial local thermal strengthening or circumferential local thermal strengthening of the heating step in step S32 is completed, the motor 2 is started again to move the large pipeline pipe 11 to be strengthened forward for a heating step of 2m and then stop. Figure 4A and Figure 4B As shown, step S32 is repeated to perform circumferential local thermal strengthening or axial local thermal strengthening on the remaining portion of the large line pipe 11 to be strengthened.

[0082] S4. Compression specimens were cut from the local heat-strengthened areas of the large pipeline pipe to be strengthened 11, the axially locally heat-strengthened large pipeline pipe 17, and the circumferentially locally heat-strengthened large pipeline pipe 18. Compression tests were conducted on a universal material testing machine. Stress-strain curves were plotted for the local heat-strengthened areas of the large pipeline pipe to be strengthened 11, the axially locally heat-strengthened large pipeline pipe 18, and the circumferentially locally heat-strengthened large pipeline pipe 18. The results showed that the compressive yield strength and compressive mechanical properties of the material in the axially locally heat-strengthened and circumferentially locally heat-strengthened areas of the large pipeline pipe were improved, as shown in Figure 5. Figure 5 As shown, the compressive yield strength of the large pipeline pipe to be strengthened 11 is 400 MPa, and the compressive yield strength of the local heat-strengthened area of ​​the axially locally heat-strengthened large pipeline pipe 17 and the circumferentially locally heat-strengthened large pipeline pipe 18 is 450 MPa. Figure 6A and Figure 6B As shown, the circumferential local heat strengthening of the large pipeline pipe 18 is as follows Figure 6C As shown, the compressive yield strength and compressive mechanical properties are improved in the black area of ​​the large linepipe.

[0083] S5. Based on the stress-strain curves of the large pipeline pipe obtained in S4, a three-dimensional structural model of the large pipeline pipe was established in ABAQUS finite value simulation software. The deformation of the large pipeline pipe to be strengthened 11, the axially locally thermally strengthened large pipeline pipe 17, and the circumferentially locally thermally strengthened large pipeline pipe 18 were analyzed respectively when the external pressure load was 10 MPa and symmetric constraint boundary conditions were applied to the end faces. The crushing pressure of the axially locally thermally strengthened large pipeline pipe 17, the circumferentially locally thermally strengthened large pipeline pipe 18, and the large pipeline pipe to be strengthened 11 was calculated. The specific expression for the theoretical calculation of the crushing pressure of large pipeline pipes is as follows:

[0084] {P c -P e}{P c 2 -P p 2 =P c P e P p f o D / h

[0085] Among them, P c is the crushing pressure of large line pipe, P e is the elastic rupture pressure, its value is 2E(h / D) 3 / (1-ν 2 ), E is the elastic modulus of the large pipeline pipe, which is 210 GPa, h is the wall thickness of the large pipeline pipe, which is 8 mm, D is the nominal outer diameter of the large pipeline pipe, which is 406 mm, ν is the Poisson's ratio, which is 0.3, P p is the plastic fracture pressure, and its value is 2f y αh / D,f y is the yield strength of large-scale pipeline pipe, α is the manufacturing coefficient of large-scale pipeline pipe, which is taken as 0.8, f o The ovality of large line pipe is 0.3%.

[0086] The same large pipeline before and after axial local thermal strengthening or circumferential local thermal strengthening, except for the improvement of compressive yield strength and compressive mechanical properties of large pipeline, other parameters remain unchanged. The formula shows that the crushing pressure P of large pipeline after axial local thermal strengthening or circumferential local thermal strengthening is c The results show that the crush resistance of large pipelines is significantly improved after axial local thermal strengthening and circumferential local thermal strengthening. Figure 7A 、 Figure 7B and Figure 7C As shown, under the same external pressure load, the deformation of the large pipeline pipe to be strengthened 11 is larger, while the deformation of the axially locally heat-strengthened large pipeline pipe 17 and the circumferentially locally heat-strengthened large pipeline pipe 18 is smaller.

[0087] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A local thermal strengthening method for improving the crush resistance of large pipelines, characterized in that: The specific implementation steps are as follows: S1, thermal strengthening device initialization; S2. Use axial induction heating coils or circumferential induction heating coils to perform axial local thermal strengthening or circumferential local thermal strengthening on the large pipeline to be strengthened: The axial induction heating coil is placed along the circumference of the large pipeline to be strengthened with a gap G a Evenly distributed, the number of axial induction heating coils N a Satisfies the following expression: L a =N a (W a +G a ) Where, L a is the circumference of the large pipeline to be strengthened, G a is the gap between the axial induction heating coils, N a is the number of axial induction heating coils, W a is the width of the axial induction heating coil; The circumferential induction heating coil is placed along the axial direction of the large pipeline to be strengthened with a gap G c Evenly distributed, the number of circumferential induction heating coils N c Satisfies the following expression: L c =(N c W c +(N c -1)G c )N′ Where, L c is the axial length of the large pipeline to be strengthened, G c is the gap between the circumferential induction heating coils, N c is the number of circumferential induction heating coils, W c is the width of the circumferential induction heating coil, N′ is the number of heating steps for the large line pipe to be strengthened; S3. Determine the length of each heating step as L' based on the length of the large pipeline to be strengthened, and perform local thermal strengthening in units of heating steps: S31, starting the motor and controlling the motor speed to move the large pipeline pipe to be strengthened at a feed speed V, so that the large pipeline pipe to be strengthened moves forward for one heating step and then stops moving; S32. When the temperature sensor detects that the temperature of the axial heat-strengthening zone or the circumferential heat-strengthening zone of the large pipeline to be strengthened reaches T0±20°C, the control box controls the heating temperature of the axial induction heating coil or the circumferential induction heating coil to maintain the temperature of the axial heat-strengthening zone or the circumferential heat-strengthening zone of the large pipeline to be strengthened at T0±20°C for M minutes, thereby completing the axial local heat strengthening or the circumferential local heat strengthening of the large pipeline to be strengthened in this heating step. S33. After the axial localized thermal strengthening or circumferential localized thermal strengthening of the heating step in step S32 is completed, the motor is restarted to move the large pipeline pipe to be strengthened forward for one heating step, then stops, and step S32 is repeated to perform axial localized thermal strengthening or circumferential localized thermal strengthening on the remaining portion of the large pipeline pipe to be strengthened. S4. Cutting compression specimens from the local heat-strengthened areas of the large pipeline pipe to be strengthened and the axially locally heat-strengthened large pipeline pipe and the circumferentially locally heat-strengthened large pipeline pipe obtained in S3, respectively. Performing compression tests on a universal material testing machine, and plotting stress-strain curves of the local heat-strengthened areas of the large pipeline pipe to be strengthened, the axially locally heat-strengthened large pipeline pipe, and the circumferentially locally heat-strengthened large pipeline pipe, respectively. S5. Based on the stress-strain curves of the large pipeline pipe obtained in S4, the deformation of the large pipeline pipe to be strengthened, the axially locally thermally strengthened large pipeline pipe, and the circumferentially locally thermally strengthened large pipeline pipe under the same external pressure load and boundary conditions are analyzed by simulation software, and the corresponding crushing pressure is calculated. The specific calculation expression of the crushing pressure of the large pipeline pipe is as follows: Among them, P c is the crushing pressure of large line pipe, P e is the elastic rupture pressure, its value is 2E(h / D) 3 / (1-ν 2 ), E is the elastic modulus of the large pipeline pipe, h is the wall thickness of the large pipeline pipe, D is the nominal outer diameter of the large pipeline pipe, ν is the Poisson's ratio, P p is the plastic fracture pressure, and its value is 2f y αh / D,f y is the yield strength of large-scale pipeline pipe, α is the manufacturing coefficient of large-scale pipeline pipe, f o is the ovality of large line pipe.

2. The local thermal strengthening method for improving the crush resistance of large pipelines according to claim 1, characterized in that: The specific steps of initializing the thermal strengthening device in step S1 are as follows: S11. Determine the strengthening direction of the large pipeline to be strengthened; S12, placing the large pipeline to be strengthened on the active roller and the driven roller; S13. Start the lifting hydraulic cylinder through the control box so that the large pipeline to be strengthened is in a concentric configuration with the axial induction heating coil or the circumferential induction heating coil.

3. The local thermal strengthening method for improving the crush resistance of large pipelines according to claim 1, characterized in that: The curvature radius of the cross section of the axial induction heating coil is 30mm-50mm larger than the curvature radius of the outer surface of the large pipeline pipe to be strengthened; the curvature radius of the cross section of the circumferential induction heating coil is 30mm-50mm larger than the curvature radius of the outer surface of the large pipeline pipe to be strengthened.

4. The local thermal strengthening method for improving the crush resistance of large-scale pipelines according to claim 1 or 3, characterized in that: The gap G between the axial induction heating coils a Meet 3W a <<G a <<6W a , the width W of the axial induction heating coil a The value range is 20mm-50mm.

5. The local thermal strengthening method for improving the crush resistance of large-scale pipelines according to claim 1 or 3, characterized in that: The gap G between the circumferential induction heating coils c Meet 5W c <<G c <<8W c , the width W of the circumferential induction heating coil c The value range is 100mm-200mm.

6. A local thermal strengthening device for improving the crush resistance of large pipelines according to any one of claims 1 to 5, characterized in that: The device comprises an axial induction heating coil, an axial induction heating coil support, a temperature sensor, a circumferential induction heating coil and a circumferential induction heating coil support. The axial induction heating coil is evenly distributed along the circumference of the large pipeline to be strengthened, the circumferential induction heating coil is evenly distributed along the axial direction of the large pipeline to be strengthened, and the temperature sensor is connected to the mounting end of the induction heating coil support.

7. The local thermal enhancement device according to claim 6, characterized in that: The cam is connected to the transmission gear of the motor and the transmission gear of the motor, and the cam is connected to the transmission gear of the motor through the transmission chain, and the transmission gear of the motor is connected to the transmission gear of the motor through the transmission chain, and the transmission gear of the motor is connected to the transmission gear of the motor.

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