High-temperature pipeline magnetostrictive guided wave sensor and monitoring method

Abstract

The invention discloses a high-temperature pipeline magnetostrictive guided wave sensor and a monitoring method, and relates to the field of ultrasonic nondestructive testing. According to the sensor, a wrinkled iron-cobalt alloy belt is used as a sensitive element, and the sensor is in dry coupling contact with a to-be-detected pipeline; the high-temperature-resistant static magnetic field coil is wound on the outer side of the aluminum pre-tightening ring in a solenoid mode, and a bias pulse excitation mode is adopted. Alternately winding the bottom end of the wrinkle structure of the wrinkle-type ferrocobalt alloy belt and the back surface of the belt material, controlling the wrinkle-type ferrocobalt alloy belt to excite a guided wave signal in a pulse section, and receiving the guided wave signal in a bias section; the dynamic magnetic field and the static magnetic field generated by the two groups of coils are perpendicular in direction, and torsional mode guided waves are generated in the high-temperature pipeline based on the reverse Weidmann effect. The sensor is easy to install and stable in performance, the whole structure is resistant to high temperature for a long time, and the engineering problem of high-temperature failure is solved. The method provided by the invention comprises the steps of optimizing pre-tightening force, pulse voltage and bias current parameters, so that the transduction efficiency is improved, and the capability of detecting new defects of the pipeline in high-temperature and variable-temperature states is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic guided wave nondestructive testing, and in particular to a high-temperature pipeline magnetostrictive guided wave sensor and a monitoring method. Background Art

[0002] High-temperature pipelines are widely used in fields such as petrochemicals, thermal power generation, and the nuclear industry, and are often used to transport high-temperature liquid and gas raw materials. Some pipelines are subjected to long-term service under extreme conditions such as variable temperature and load. They are prone to local cracking and corrosion defects caused by factors such as high-temperature creep and material degradation, leading to accidents such as pipeline bursts and toxic substance leaks, posing significant risks to the normal operation of industrial equipment and the personal safety of employees. In the structural health assessment of pipelines at room temperature (below 120°C), magnetostrictive guided wave sensors are widely used in engineering due to their advantages such as long detection distance, small node size, and easy signal analysis. However, in the actual production and processing of high-temperature pipelines (greater than 120°C), these sensors face problems such as coupling agent failure, coil damage, and permanent magnet demagnetization, making it difficult for them to operate stably for a long time, and they may even be directly damaged when in contact with the pipe wall. Some adaptations, such as water-cooling loops, high-temperature epoxy resin coupling, and high-temperature magnet excitation, can partially improve the temperature resistance of magnetostrictive guided wave sensors. However, water-cooling loops only support short-term high-temperature contact coupling. High-temperature epoxy resin has a maximum temperature resistance of 300°C and is prone to aging after repeated temperature cycling. High-temperature magnets have a maximum temperature resistance of 350°C and the excitation strength cannot be adjusted, resulting in low sensor conversion efficiency. Currently, no magnetostrictive guided wave sensors can stably operate long-term on pipeline surfaces above 500°C, and conventional guided wave monitoring and signal analysis methods are inapplicable in high-temperature pipelines.

[0003] Based on the above shortcomings of the prior art, there is an urgent need for a high-temperature pipeline magnetostrictive guided wave sensor with a long-term temperature resistance of more than 500°C and a corresponding high-temperature pipeline magnetostrictive guided wave monitoring method. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-temperature pipeline magnetostrictive guided wave sensor and monitoring method to meet the engineering needs of structural health assessment during the production process of high-temperature pipelines.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] In one aspect, the present invention provides a magnetostrictive guided wave sensor for high-temperature pipelines, comprising a corrugated iron-cobalt alloy strip, a high-temperature-resistant guided wave excitation coil, a fiberglass strip, an aluminum preload ring, a preload adjustment knob, a thin film preload detection unit, and a high-temperature-resistant static magnetic field coil. This sensor, based on the inverted Widmanst effect, combines a high-temperature-resistant guided wave excitation coil with a high-temperature-resistant static magnetic field coil to excite mutually perpendicular dynamic and static magnetic fields, thereby generating non-dispersive T(0,1) torsional guided waves in the pipeline. The sensor's core sensitive element is a corrugated iron-cobalt alloy strip. The strip is first cold-rolled from an iron-cobalt alloy raw material into a thin strip with a thickness of 0.1mm-0.3mm. A die is then used to stamp the strip lengthwise to create several adjacent corrugations, spaced 5mm-20mm apart. Flat sections of the strip remain between the corrugations. The cross-section of each corrugation is a combination of an upper semicircular arc with a radius of 1.5mm-3mm and two rounded transition corners, with the arc and the rounded corners curving in opposite directions. The high-temperature guided wave excitation coil is made of refractory mica wire, capable of operating at temperatures exceeding 600°C. It is alternately wound around the base of the corrugated iron-cobalt alloy ribbon and the back of the ribbon, creating a flat coupling surface at the bottom. This winding pattern provides the circumferential dynamic magnetic field required to excite the guided wave while maximizing the sensor's coupling contact area. A fiberglass tape, no thicker than 5mm and 5-10mm wider than the ribbon, is wrapped around the outer uneven surface of the ribbon, providing thermal insulation and preload buffering. Its high acoustic impedance also enhances the efficiency of guided wave energy transfer. An aluminum preload ring, consisting of a C-shaped clamp and a bolt at its opening, is wrapped around the fiberglass tape. The preload adjustment knob tightens the inner component, maintaining a tight dry coupling with the pipe under test. The film preload detection unit is made of a folded resistance wire less than 0.1mm thick. It is glued and fixed between the fiberglass tape and the aluminum preload ring to assess the sensor's installation preload. A high-temperature static magnetic field coil is made of a fire-resistant mica wire capable of operating at temperatures exceeding 600°C. It is spirally wound between two bolts on the outside of the tightened aluminum preload ring, replacing conventional permanent magnets to provide a biased static magnetic field. This fundamentally avoids the problem of permanent magnet demagnetization at high temperatures. To enhance the amplitude of the sensor's guided wave signal at high temperatures, the high-temperature static magnetic field coil uses a bias pulse excitation method. This synchronously controls the high-temperature guided wave excitation coil during pulse excitation and bias reception. Compared to conventional electromagnet DC excitation schemes, pulse excitation enhances the energy of the guided wave, while the subsequent bias stage ensures the stability of the received guided wave echo signal.

[0007] On the other hand, the present invention also provides a method for monitoring magnetostrictive guided waves in high-temperature pipelines, comprising the following steps:

[0008] Step 1: Install the high-temperature pipeline magnetostrictive guided wave sensor, connect the film preload detection unit to the resistance-pressure conversion circuit, and rotate the preload adjustment knob until the preload displayed by the conversion circuit is 0.05MPa-0.1MPa. At this point, the sensor has made preliminary contact with the pipeline, but the parameters have not yet reached the optimal level.

[0009] Step 2: Place a guided wave transduction efficiency evaluation sensor node 1 meter axially from the installed high-temperature pipeline magnetostrictive guided wave sensor. This node contains a calibrated clamp-type magnetostrictive sensor and the epoxy resin layer required for coupling. Simultaneously connect the high-temperature pipeline magnetostrictive guided wave sensor and the guided wave transduction efficiency evaluation sensor node to a guided wave transduction efficiency test device. The device contains two independent guided wave excitation and receiving channels, and has bias pulse excitation and guided wave one-excitation-one-receiver functions.

[0010] Step 3: Operate the guided wave transduction efficiency test equipment in the excitation and reception mode of the high-temperature pipeline magnetostrictive guided wave sensor and the guided wave transduction efficiency evaluation sensor node. Rotate the preload adjustment knob to gradually increase the value by 0.02 MPa, and perform the guided wave excitation and reception test simultaneously. When the guided wave transduction efficiency equipment shows that the peak value of the direct wave peak changes from an upward trend to a downward trend, stop rotating the preload adjustment knob. At this time, the coupling state is optimal.

[0011] Step 4: The pulse voltage of the high-temperature resistant static magnetic field coil is set to 100V by the waveguide transduction efficiency test equipment, and gradually increased by 25V. The waveguide excitation reception test is performed simultaneously. When the waveguide transduction efficiency equipment shows that the peak value of the direct wave peak changes from an upward trend to a downward trend, the voltage increase is stopped. At this time, the pulse voltage in the high-temperature resistant static magnetic field coil is optimal;

[0012] Step 5: Operate the guided wave transduction efficiency test equipment in a one-excitation-one-receive mode for excitation of the guided wave transduction efficiency evaluation sensor node and reception of the high-temperature pipeline magnetostrictive guided wave sensor. Set the bias current passed into the high-temperature resistant static magnetic field coil to 0.5A and increase it in steps of 0.1A. Simultaneously perform the guided wave excitation and reception test. When the guided wave transduction efficiency equipment shows that the direct wave peak value changes from an upward trend to a downward trend, stop increasing the current. At this time, the bias current in the high-temperature resistant static magnetic field coil is optimal.

[0013] Step 6: Remove the waveguide efficiency evaluation sensor node and disconnect the waveguide transduction efficiency test equipment, connect the high-temperature pipeline magnetostrictive waveguide sensor to the waveguide long-term monitoring equipment with the same excitation and acquisition hardware structure, and set the optimal coupling state, pulse voltage and bias current parameters of steps 3 to 5, and perform subsequent waveguide long-term monitoring according to fixed values.

[0014] Step seven: Regularly obtain the self-excited and self-received signals of the high-temperature pipeline magnetostrictive guided wave sensor through the guided wave long-term monitoring equipment, and compensate the wave velocity and amplitude of the guided wave monitoring signal according to the real-time recorded operating temperature. The compensated signal is subtracted from the baseline signal calibrated with the initial state of the pipeline to identify new defects in the tested pipeline.

[0015] In step seven, an adaptive wave velocity and amplitude compensation method is used to solve the problem of violent fluctuations of the waveguide monitoring signal under high temperature conditions and to improve the probability of identifying defects from the residual signal after baseline subtraction. Compared with the existing temperature compensation method, the method described in the present invention is more suitable for high-temperature waveguide signals, and the calculation process is easy to implement. First, a database of high-temperature pipeline initial state waveguide signals at different temperatures T is recorded, where the lowest temperature value recorded in the database is T0, and the data point label is n. The horizontal coordinate d of the echo peak point corresponding to the same high-energy reflector in the database is n (T) is used as a reference, and the wave velocity stretching function f(β1,β2,T) is fitted, where β1 and β2 are the quadratic and linear fitting parameters calculated from all data points in the library, as shown in the following formula:

[0016] (β1,β2)=arg min∑[(d n (T)-β1T 2 -β2T) 2 ]

[0017] The velocity stretching function f(β1,β2,T) means the multiple of the guided wave velocity change relative to the lowest temperature value T0 in the database at temperature T, as shown in the following formula:

[0018]

[0019] The raw one-dimensional guided wave monitoring signal collected in real time is u0(t,T), where t is the time corresponding to each sampling point in the monitoring signal, and T is the temperature during monitoring. Therefore, u0(t,T) represents the amplitude of the guided wave monitoring signal at time t at temperature T. The time t term in u0(t,T) is multiplied by the velocity stretching function f(β1,β2,T) to perform a transverse time stretch on the signal to compensate for the velocity changes caused by temperature drift. u1(t,T) represents the amplitude of the guided wave monitoring signal at time t at temperature T after velocity compensation, and is calculated using the following formula:

[0020] u1(t,T)=u0(t·f(β1,β2,T),T)

[0021] Intercept the echo signal of each characteristic structure j in the database and count its peak-to-peak value c respectively j,n (T) and the pipe temperature T during calibration, the amplitude stretching function g(α 1,j ,α 2,j ,T),α1,j , α 2,j are the fitting parameters of the quadratic term and the linear term calculated from all data points in the database with respect to the characteristic structure j, as follows:

[0022] (α 1,j ,α 2,i )=arg min∑[(c j,n (T)-α 1,j T 2 -α 2,j T) 2 ]

[0023] Amplitude stretching function g(α 1,j ,α 2,j ,T) means the multiple of the signal amplitude of characteristic structure j at temperature T relative to the lowest temperature value T0 in the database, as shown in the following formula:

[0024]

[0025] Multiply u1(t,T) by the amplitude stretching function g(α 1,j ,α 2,j ,T), longitudinal amplitude stretching is performed on the signal to compensate for the characteristic echo amplitude change caused by temperature drift. u2(t,T) is the amplitude of the guided wave monitoring signal at temperature T at time t after amplitude compensation, and is calculated by the following formula:

[0026] u2(t,T)=u1(t,T)·g(α 1,j ,α 2,j ,T)

[0027] Compare the amplitude-compensated signal u2(t,T) with the lowest temperature reference signal u in the database d (t, T0) performs baseline subtraction, when the residual signal after subtraction is higher than u d If the wave packet is 3% of the peak value of (t, T0), it is judged that the pipeline has new defects.

[0028] The beneficial effects of the present invention are:

[0029] 1. After being wrapped around the high-temperature resistant guided wave excitation coil, the corrugated iron-cobalt alloy strip can still maintain a flat contact surface with the high-temperature pipeline. Combined with the aluminum pre-tightening ring mechanical dry coupling solution, it fundamentally solves the problem of high-temperature failure of conventional magnetostrictive guided wave sensor components and coupling agents.

[0030] 2. The use of high-temperature resistant static magnetic field coils instead of conventional permanent magnet excitation improves the applicable temperature and operating stability of the magnetostrictive waveguide sensor; the use of a dual-coil combination bias pulse-waveguide excitation scheme can enhance the transduction efficiency of the sensor at high temperatures.

[0031] 3. Based on the initial state guided wave signal database, the wave velocity and amplitude stretching functions are fitted to compensate for the guided wave monitoring signal under high temperature, reducing the interference of temperature fluctuations of high-temperature pipeline operation on the guided wave signal, thereby increasing the probability of identifying defects from the residual signal after baseline subtraction.

[0032] It should be noted that the sensor of the present invention is an optimized solution, and the method of the present invention is not limited to the waveguide sensor of the present invention. Other waveguide sensors can also be applied to the method of the present invention.

[0033] Other features and advantages of the present invention will be set forth in the following description, and in part will be apparent from the description, or may be learned by practicing embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic structural diagram of a magnetostrictive guided wave sensor for high-temperature pipelines according to the present invention;

[0035] Figure 2 Schematic diagram of the torsional mode guided wave excited by the magnetostrictive guided wave sensor for high-temperature pipelines of the present invention;

[0036] Figure 3 Schematic diagram of bias pulse excitation and waveguide synchronous control excitation of the high-temperature pipeline magnetostrictive guided wave sensor of the present invention;

[0037] Figure 4 This is a schematic flow chart of the magnetostrictive guided wave monitoring method for high-temperature pipelines according to the present invention;

[0038] Figure 5 Schematic diagram of the guided wave signal velocity, amplitude compensation and defect identification of the magnetostrictive guided wave monitoring method for high-temperature pipelines according to the present invention;

[0039] In the figure: 1-high-temperature pipeline, 2-corrugated iron-cobalt alloy belt, 3-high-temperature resistant guided wave excitation coil, 4-glass fiber belt, 5-aluminum preload ring, 6-preload adjustment knob, 7-film preload detection unit, 8-high-temperature resistant static magnetic field coil, 9-dynamic magnetic field, 10-static magnetic field, 11-magnetostrictive force, 12-torsional mode guided wave. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The present invention will be further described below in conjunction with the accompanying drawings and the above embodiments. The specific implementation examples provided below are only illustrative and not restrictive, and should not be used to limit the scope of protection of the present invention.

[0041] like Figure 1As shown, clean an area slightly larger than the sensor on the surface of the high-temperature pipe 1 to be tested, and remove the covering insulation layer and other attachments. Place the flat surface of the corrugated iron-cobalt alloy strip 2 wrapped with the high-temperature resistant waveguide excitation coil 3 against the outer wall of the high-temperature pipe 1, and apply external force to temporarily fix it. Cut a glass fiber strip 4 of the corresponding length to cover the upper layer of the corrugated iron-cobalt alloy strip 2, wrap the aluminum preload ring 5 around the outside of the glass fiber strip 4, and add a thin film preload detection unit 7 between the two layers. Tighten the aluminum preload ring 5 using the preload adjustment knob 6, and wind the high-temperature resistant static magnetic field coil 8 on the flat area in the middle to complete the preliminary installation of the sensor.

[0042] like Figure 2 As shown, the flat surface of the corrugated iron-cobalt alloy strip 2 can fit tightly against the high-temperature pipeline 1. Based on the principle of electromagnetic induction, the high-temperature-resistant guided wave excitation coil 3 generates a circumferential dynamic magnetic field 9, while the high-temperature-resistant static magnetic field coil 8 generates an axial static magnetic field 10. The magnetic fields generated by these two sets of coils are perpendicular to each other. Based on the inverted Widmanstätten effect, a shear magnetostrictive force 11 is generated in the corrugated iron-cobalt alloy strip 2, which is transmitted to the high-temperature pipeline 1 to form a torsional mode guided wave 12.

[0043] like Figure 3 As shown, the high-temperature resistant static magnetic field coil 8 adopts a bias pulse excitation method, which is realized by an external pulse charge and discharge circuit. The entire excitation current is divided into a pulse segment and a bias segment, and the high-temperature resistant waveguide excitation coil 3 is synchronously controlled to excite in the pulse segment and receive in the bias segment. Pulse segment excitation can enable the high-temperature resistant static magnetic field coil 8 to generate a stronger static magnetic field 10, thereby increasing the energy of the waveguide excitation, while the bias segment reception can improve the stability of the echo signal. The above scheme not only improves the transducer efficiency of the sensor under high temperature conditions, but also avoids the problem of high-temperature failure of conventional permanent magnets and coils.

[0044] After the initial installation of the sensor, Figure 4 The following process demonstrates the magnetostrictive guided wave monitoring method for high-temperature pipelines. By combining a sensor node for evaluating the efficiency of guided wave transduction with testing equipment, the sensor's coupling preload, pulse excitation voltage, and bias current parameters are optimized and adjusted. After determining the optimal monitoring parameters, the sensor is connected to long-term monitoring equipment, which periodically excites the receiving guided wave with fixed parameters. Defects are identified by measuring the amplitude of the residual guided wave signal compared to the initial state.

[0045] Reference Figure 5 The method performs velocity and amplitude temperature compensation and defect identification on the guided wave monitoring signal. First, the initial state guided wave signal database is established to record the initial state guided wave signals of high-temperature pipelines at different temperatures T. The temperature-related velocity stretching function f(β1,β2,T) and amplitude stretching function g(α 1,j ,α 2,j,T), as shown in the following formula:

[0046] (β1,β2)=arg min∑[(d n (T)-β1T 2 -β2T) 2 ]

[0047]

[0048] (α 1,j ,α 2,j )=arg min∑[(c j,n (T)-α 1,j T 2 -α 2,j T) 2 ]

[0049]

[0050] Where the data point labels are n, d n (T) is the horizontal coordinate of the peak echo point corresponding to the same high-energy reflector in the database, c j,n (T) is the echo signal amplitude of each characteristic structure j, T0 is the lowest temperature in the database, β1 and β2 are the wave velocity fitting parameters of the quadratic term and the linear term, α 1,j , α 2,j are the amplitude fitting parameters of the quadratic term and the linear term about the characteristic structure j. By stretching the function f(β1,β2,T), g(α 1,j ,α 2,j ,T) to compensate the online monitoring signal u0(t,T), where t is the time corresponding to each sampling point in the monitoring signal, and T is the temperature during monitoring, as shown in the following formula:

[0051] u1(t,T)=u0(t·f(β1,β2,T),T)

[0052] u2(t,T)=u1(t,T)·g(α 1,j ,α 2,j ,T)

[0053] Compare the amplitude-compensated signal u2(t,T) with the lowest temperature reference signal u in the database d (t, T0) performs baseline subtraction, when the residual signal after subtraction is higher than u d If the wave packet is 3% of the peak value of (t, T0), it is judged that the pipeline has new defects.

[0054] Through this embodiment, magnetostrictive guided wave monitoring can be effectively performed on high-temperature pipelines above 500° C., which has important application value and promotion significance.

[0055] The above description is only intended to help understand the method and core concept of the present invention; at the same time, for those skilled in the art, according to the concept of the present invention, there will be changes in the specific implementation and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A high-temperature pipeline magnetostrictive guided wave sensor, characterized by: It includes a corrugated iron-cobalt alloy strip, a high-temperature resistant guided wave excitation coil, a glass fiber strip, an aluminum preload ring, a preload adjustment knob, a film preload detection unit and a high-temperature resistant static magnetic field coil; the corrugated iron-cobalt alloy strip is first processed from the iron-cobalt alloy raw material into a thin strip of 0.1mm-0.3mm by cold rolling, and then a mold is used to stamp out several adjacent corrugated structures arranged at equal intervals of 5mm-20mm in the length direction of the strip, and the flat sections of the strip remain between the corrugated structures; the cross-section of a single corrugated structure is an upper semicircular arc with a radius of 1.5mm-3mm; the high-temperature resistant guided wave excitation coil is made of mica refractory wire that can work at temperatures above 600℃ The width of the glass fiber tape is 5mm-10mm larger than that of the corrugated iron-cobalt alloy tape, and the thickness does not exceed 5mm. It is wrapped around the non-flat surface of the outer side of the corrugated iron-cobalt alloy tape. The aluminum preload ring consists of a C-shaped clamp and a bolt at its opening, which covers the glass fiber tape from the outside. The inner part is tightened by rotating the preload adjustment knob at the bolt. The film preload detection unit is made of a folded resistance wire with a thickness of less than 0.1mm. It is glued and fixed between the glass fiber tape and the aluminum preload ring. The high-temperature resistant static magnetic field coil is made of a mica refractory wire that can operate at a temperature above 600°C. It is spirally wound between the two bolts on the outside of the tightened aluminum preload ring.

2. The high-temperature pipeline magnetostrictive guided wave sensor according to claim 1, characterized in that: The high-temperature resistant waveguide excitation coil and the high-temperature resistant static magnetic field coil are orthogonal to each other, and the directions of the generated dynamic magnetic field and static magnetic field are perpendicular. Based on the inverted Widmanst effect, torsional mode waveguide is generated inside the high-temperature pipeline; the high-temperature resistant static magnetic field coil adopts a bias pulse excitation method. The process includes an initial pulse segment with high magnetic field intensity and a subsequent bias segment with stable intensity. The high-temperature resistant waveguide excitation coil is synchronously controlled to excite the waveguide signal in the pulse segment, and the bias segment receives the waveguide signal.

3. A high-temperature pipeline magnetostrictive guided wave monitoring method based on the high-temperature pipeline magnetostrictive guided wave sensor according to claim 1, characterized in that: The steps include: Step 1: Install the high-temperature pipeline magnetostrictive guided wave sensor, connect the film preload detection unit to the resistance-pressure conversion circuit, and rotate the preload adjustment knob so that the preload displayed by the conversion circuit is 0.05MPa-0.1MPa; Step 2: Arrange a waveguide transducer efficiency evaluation sensor node on the pipe section 1 meter axially from the installed high-temperature pipeline magnetostrictive waveguide sensor. Simultaneously connect the high-temperature pipeline magnetostrictive waveguide sensor and the waveguide transducer efficiency evaluation sensor node to a waveguide transducer efficiency test device. The device contains two independent waveguide excitation and receiving channels, and has bias pulse excitation and waveguide one-excitation-one-receiver functions. Step 3: Operate the guided wave transduction efficiency test equipment in the excitation and reception mode of the high-temperature pipeline magnetostrictive guided wave sensor and the guided wave transduction efficiency evaluation sensor node. Rotate the preload adjustment knob to gradually increase the value by 0.02 MPa, and perform the guided wave excitation and reception test simultaneously. When the guided wave transduction efficiency equipment shows that the peak value of the direct wave peak changes from an upward trend to a downward trend, stop rotating the preload adjustment knob. At this time, the coupling state is optimal. Step 4: The pulse voltage of the high-temperature resistant static magnetic field coil is set to 100V by the waveguide transduction efficiency test equipment, and gradually increased by 25V. The waveguide excitation reception test is performed simultaneously. When the waveguide transduction efficiency equipment shows that the peak value of the direct wave peak changes from an upward trend to a downward trend, the voltage increase is stopped. At this time, the pulse voltage in the high-temperature resistant static magnetic field coil is optimal; Step 5: Operate the guided wave transduction efficiency test equipment in a one-excitation-one-receive mode for excitation of the guided wave transduction efficiency evaluation sensor node and reception of the high-temperature pipeline magnetostrictive guided wave sensor. Set the bias current passed into the high-temperature resistant static magnetic field coil to 0.5A and increase it in steps of 0.1A. Simultaneously perform the guided wave excitation and reception test. When the guided wave transduction efficiency equipment shows that the direct wave peak value changes from an upward trend to a downward trend, stop increasing the current. At this time, the bias current in the high-temperature resistant static magnetic field coil is optimal. Step 6: Remove the waveguide efficiency evaluation sensor node and disconnect the waveguide transduction efficiency test equipment. Connect the high-temperature pipeline magnetostrictive waveguide sensor to a long-term waveguide monitoring device with the same excitation and acquisition hardware structure. Set the optimal coupling state, pulse voltage, and bias current parameters from steps 3 to 5, and perform subsequent long-term waveguide monitoring at fixed values. Step seven: Regularly obtain the self-excited and self-received signals of the high-temperature pipeline magnetostrictive guided wave sensor through the guided wave long-term monitoring equipment, and compensate the wave velocity and amplitude of the guided wave monitoring signal according to the real-time recorded operating temperature. The compensated signal is subtracted from the baseline signal calibrated with the initial state of the pipeline to identify new defects in the tested pipeline.

4. The magnetostrictive guided wave monitoring method for high-temperature pipelines according to claim 3, characterized in that: In step 7, first record the initial state of the high-temperature pipeline guided wave signal database at different temperatures T, where the lowest temperature recorded in the database is T0 and the data point label is n. The horizontal coordinate d of the echo peak point corresponding to the same high-energy reflector in the database is n (T) is the reference, and the wave velocity stretching function f(β1,β2,T) is fitted, where T1 and β2 are the quadratic and linear fitting parameters calculated from all data points in the library, as shown in the following formula: (β1,β2)=arg minΣ[(d n (T)-β1T 2 -β2T) 2 ] The velocity stretching function f(β1,β2,T) means the multiple of the guided wave velocity change relative to the lowest temperature value T0 in the database at temperature T, as shown in the following formula: The raw one-dimensional guided wave monitoring signal collected in real time is u0(t,T), where t is the time corresponding to each sampling point in the monitoring signal, and T is the temperature during monitoring. Therefore, u0(t,T) represents the amplitude of the guided wave monitoring signal at time t at temperature T. The time t term in u0(t,T) is multiplied by the velocity stretching function f(β1,β2,T) to perform a transverse time stretch on the signal to compensate for the velocity changes caused by temperature drift. u1(t,T) represents the amplitude of the guided wave monitoring signal at time t at temperature T after velocity compensation, and is calculated using the following formula: u1(t,T)=u0(t·f(β1,β2,T),T) Intercept the echo signal of each characteristic structure j in the database and count its peak-to-peak value c respectively j,n (T) and the pipe temperature T during calibration, the amplitude stretching function g(α 1,j ,α 2,j ,T),α 1,j , α 2,j are the fitting parameters of the quadratic term and the linear term calculated from all data points in the database with respect to the characteristic structure j, as follows: (a 1,j ,a 2,j )=arg min∑[(c j,n (T)-a 1,j T 2 -a 2,j T) 2 ] Amplitude stretching function g(α 1,j ,α 2,j ,T) means the multiple of the signal amplitude of characteristic structure j at temperature T relative to the lowest temperature value T0 in the database, as shown in the following formula: Multiply u1(t,T) by the amplitude stretching function g(α 1,j ,α 2,j ,T), longitudinal amplitude stretching is performed on the signal to compensate for the characteristic echo amplitude change caused by temperature drift. u2(t,T) is the amplitude of the guided wave monitoring signal at temperature T at time t after amplitude compensation, and is calculated by the following formula: u2(t,T)=u1(t,T)·g(α 1,j ,α 2,j ,T) Compare the amplitude-compensated signal u2(t,T) with the lowest temperature reference signal u in the database d (t, T0) performs baseline subtraction, when the residual signal after subtraction is higher than u d If the wave packet is 3% of the peak value of (t, T0), it is judged that the pipeline has new defects.

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