Fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the pipe ends of steel pipes

Abstract

This application relates to the technical field of magnetic particle flaw detection equipment. Specifically, it is a fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the pipe ends of steel pipes. Through the synergistic effect of the composite magnetization component and the annular pulsating DC guiding magnetic yoke, a three-dimensional rotating dynamic composite magnetic field is formed at the pipe end of the steel pipe, effectively solving the problem of uneven magnetic field distribution in the pipe end area of traditional equipment and achieving dead-angle-free detection of the inner and outer surfaces. The stepped increasing section and the oscillating maintaining section of the pulsating magnetization power supply adjust the magnetic field strength to change with time, enabling the magnetic field to penetrate the wall thickness of the steel pipe during the detection process while avoiding the problem of magnetic saturation. The radial position of the circumferential magnetic yoke coil group and the axial position of the longitudinal magnetic yoke can be programmatically adjusted to support the detection of steel pipes with an outer diameter ranging from 80 mm to 820 mm. Synchronous detection of the inner and outer surfaces is achieved through a single composite magnetization component, avoiding the design of two sets of independent magnetization devices in traditional technologies and reducing costs.

Description

Technical Field

[0001] This application belongs to the technical field of magnetic particle flaw detection equipment, especially the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the pipe ends of steel pipes. Background Art

[0002] When using automatic magnetic particle flaw detection equipment, the two ends of the steel pipe (within about 300 mm) usually belong to the "undetectable area", that is, the blind area. This is because it is difficult for the magnetization device (such as a coil or a yoke) of the automatic equipment to form a uniform magnetic field distribution at the pipe end, resulting in a decrease in detection sensitivity. For the blind area at the pipe end, the existing conventional solution is to use the fluorescent magnetic particle flaw detection method for manual or semi-automatic supplementary detection.

[0003] Chinese Patent CN1752746A discloses a magnetic particle flaw detection method and device, which solves the blind area problem caused by uneven magnetic field distribution by synchronously moving the magnetization device and the nozzle device along the circumferential direction of the pipeline to form a dynamic magnetization area. However, it is necessary to realize the synchronous movement of the magnetic field and the nozzle device through a variable frequency motor, a yoke holding mechanism, etc., with high mechanical complexity and high manufacturing and maintenance costs; it generates a rotating magnetic field covering 360° through three-phase alternating current, and the change of the magnetic field intensity only depends on the current amplitude, and the dynamic characteristics of the magnetic field cannot be flexibly adjusted; if it is necessary to detect the inner and outer surfaces of the object to be detected at the same time, two sets of independent magnetization devices need to be configured, further increasing the volume and cost of the equipment. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: to solve the deficiencies in the prior art, and thus provide a fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the pipe ends of steel pipes, aiming to solve at least one of the above technical problems.

[0005] The technical solution adopted by the present invention to solve its technical problems is:

[0006] The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the pipe ends of steel pipes includes:

[0007] A frame, which constitutes the main support structure of the equipment;

[0008] A composite magnetization assembly, including a circumferential pulsating DC yoke coil group, a longitudinal pulsating DC coil, and an annular pulsating DC guiding yoke arranged on the frame, where:

[0009] The annular pulsating DC guiding yoke has an annular magnetic conduction structure concentric with the axis of the steel pipe, and is configured to conduct the axial magnetic field generated by the longitudinal pulsating DC coil and gradually increase the magnetic field intensity;

[0010] The circumferential pulsating DC yoke coil group includes two symmetrically arranged independent yoke units, and each yoke unit is movably arranged in the radial direction of the annular pulsating DC guiding yoke through a linear driving mechanism to form an adjustable circumferential magnetization channel;

[0011] A dynamic excitation system includes a pulsating magnetization power supply electrically connected to a composite magnetization component. The power supply is configured to output pulsating direct current with a preset frequency and duty cycle, where:

[0012] The pulsating direct current generates a time-varying circumferential magnetic field in the circumferential pulsating DC yoke coil group and a pulsating oscillating longitudinal magnetic field in the longitudinal pulsating DC coil at the same time;

[0013] The circumferential magnetic field and the longitudinal magnetic field are magnetically coupled through an annular pulsating DC guiding yoke to form a three-dimensional rotating dynamic composite magnetic field at the end of the steel pipe.

[0014] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the end of the steel pipe of the present invention, the output voltage waveform of the pulsating magnetization power supply includes continuous working cycles, and each cycle includes:

[0015] A stepped increasing section: The voltage gradually increases from an initial value V0 to a peak value Vmax in an arithmetic sequence, where V0 ∈ [5V, 10V], Vmax ∈ [45V, 50V], and the step size ΔV ∈ [5V, 10V];

[0016] An oscillation maintaining section: After reaching Vmax, the output voltage pulsates periodically within a preset oscillation range [Vmax - ΔVd, Vmax] at a frequency f ∈ [10Hz, 100Hz], where ΔVd ∈ [3V, 5V].

[0017] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the end of the steel pipe of the present invention, the voltage change rate of the stepped increasing section can be programmably set to a linear increasing mode or an exponential increasing mode, and the time constant τ of the exponential increasing mode ∈ [0.1s, 0.5s].

[0018] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the end of the steel pipe of the present invention, the periodic pulsating oscillation waveform of the oscillation maintaining section is at least one of a square wave, a triangular wave, or a sine wave, and there is a zero voltage interval with a duration t ∈ [10ms, 50ms] between adjacent cycles.

[0019] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the end of the steel pipe of the present invention, the frame includes a chassis and a moving frame. The moving frame is slidably arranged on the chassis along the axial direction of the steel pipe, and a liftable and slidable mounting back plate is arranged on the moving frame.

[0020] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the end of the steel pipe of the present invention, the longitudinal pulsating DC coil is horizontally slidably arranged on the mounting back plate for adapting to the flaw detection of the inner and outer surfaces of steel pipes with different diameters and wall thicknesses.

[0021] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end of the present invention, the two yoke units of the circumferential pulsating DC yoke coil group are slidably arranged on the mounting backboard, and the included angle between the two yoke units is 120°.

[0022] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end of the present invention, a cantilever bracket is fixed to the bottom of the mounting backboard, and the annular pulsating DC guiding yoke is fixedly arranged on the cantilever bracket.

[0023] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end of the present invention, the magnetic head of the yoke unit is elastically and floatingly connected to its mounting seat, and the floating direction is parallel to the radial direction of the steel pipe.

[0024] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end of the present invention, the longitudinal pulsating DC coil is elastically and floatingly connected to its mounting seat, and the floating direction is parallel to the axis of the steel pipe.

[0025] The beneficial effects of the present invention are as follows:

[0026] (1) Through the synergistic effect of the composite magnetization component and the annular pulsating DC guiding yoke, a three-dimensional rotating dynamic composite magnetic field is formed at the end of the steel pipe, effectively solving the problem of uneven magnetic field distribution in the pipe end area of traditional equipment and realizing non-dead-angle detection of the inner and outer surfaces;

[0027] (2) The stepped increasing section and the oscillating maintaining section of the pulsating magnetization power supply adjust the magnetic field strength changing with time, enabling the magnetic field to penetrate the wall thickness of the steel pipe during the detection process and avoiding the problem of magnetic saturation;

[0028] (3) The closed magnetic circuit design of the annular magnetic conductive structure significantly improves the longitudinal magnetic field strength and enhances the magnetic powder aggregation ability for micro defects;

[0029] (4) The radial position of the circumferential yoke coil group and the axial position of the longitudinal yoke can be programmably adjusted, supporting the detection of steel pipes with an outer diameter ranging from 80 mm to 820 mm;

[0030] (5) Synchronous detection of the inner and outer surfaces is achieved through a single composite magnetization component, avoiding the design of two sets of independent magnetization devices in traditional technologies and reducing costs. Description of the Drawings

[0031] The technical solutions of the present application will be further described below in conjunction with the drawings and embodiments.

[0032] Figure 1 It is a schematic diagram of the equipment body structure of Embodiments 1-3 of the present application;

[0033] Figure 2 It is a schematic diagram of the control principle of the circumferential yoke circuit of Embodiments 1-3 of the present application;

[0034] Figure 3 It is the schematic diagram of the longitudinal coil and yoke circuit control for Embodiments 1-3 of the present application;

[0035] Figure 4 It is the schematic diagram of the voltage pulsating with time for Embodiment 1 of the present application;

[0036] Figure 5 It is the schematic diagram of the voltage pulsating with time for Embodiment 2 of the present application;

[0037] Figure 6 It is the schematic diagram of the voltage pulsating with time for Embodiment 3 of the present application;

[0038] Figure 7 It is the schematic diagram of the magnetic field distribution plane for Embodiments 1-3 of the present application;

[0039] Figure 8 It is the schematic diagram of the three-dimensional rotating composite magnetic field distribution for Embodiment 3 of the present application;

[0040] The reference signs in the figure are:

[0041] Frame 10, circumferential pulsating DC yoke coil group 11, longitudinal pulsating DC coil 12, annular pulsating DC guiding yoke 13, linear driving mechanism 14;

[0042] Chassis 101, moving frame 102, mounting backplane 103, driving cylinder 104. Detailed implementation manners

[0043] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0044] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation on the protection scope of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0045] In the description of this application, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

[0046] The technical solution of this application will be described in detail below with reference to the drawings and in combination with embodiments.

[0047] This embodiment provides a fluorescent magnetic particle flaw detection device for the inner and outer surfaces of the pipe end of a steel pipe, and its structure is referred to Figure 1 , including: a frame 10, a composite magnetization assembly, a dynamic excitation system, and a fluorescent magnetic particle spraying device (the fluorescent magnetic particle spraying device is a conventional device in this technical field and is not marked in the figure). The composite magnetization assembly includes a circumferential pulsating DC yoke coil group 11, a longitudinal pulsating DC coil 12, and an annular pulsating DC guiding yoke 13 arranged on the frame 10.

[0048] The annular pulsating DC guiding yoke 13 has an annular magnetic conduction structure concentric with the axis of the steel pipe, configured to conduct the magnetic path of the axial magnetic field generated by the longitudinal pulsating DC coil 12 and gradually increase the magnetic field intensity; the annular magnetic conduction structure forms a closed magnetic path with a high magnetic permeability material (silicon steel or soft magnetic alloy), and confines the axial magnetic field generated by the longitudinal yoke coil 12 within the annular path. This structure reduces the dissipation of magnetic lines of force, ensures that the magnetic field acts concentratedly on the pipe end area, and optimizes the magnetic path distribution especially for the detection requirements of the inner and outer surfaces. At the end of the annular magnetic conduction structure (near the pipe end area), the magnetic field intensity reaches a peak due to the concentration and superposition effect of the magnetic path, ensuring the high-sensitivity aggregation of fluorescent magnetic particles at the defects.

[0049] The circumferential pulsating DC yoke coil group 11 includes two symmetrically arranged independent yoke units, and each yoke unit is movably arranged in the radial direction of the annular pulsating DC guiding yoke 13 through a linear driving mechanism 14 to form an adjustable circumferential magnetization channel.

[0050] Specifically, the frame 10 constitutes the main supporting structure of the equipment. The frame 10 includes a chassis 101 and a mobile frame 102. The mobile frame 102 is slidably set on the chassis 101 along the axial direction of the steel pipe through a guide rail slider assembly, and a driving cylinder 104 is set between the chassis 101 and the mobile frame 102 to drive the mobile frame 102 to slide on the chassis 101. A lifting and sliding mounting backplate 103 is set on the mobile frame 102 through the guide rail slider assembly. A first screw nut transmission mechanism is set between the mounting backplate 103 and the mobile frame 102, and the first screw nut transmission mechanism is driven by a first servo motor to drive the mounting backplate 103 to lift and lower.

[0051] Preferably, the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end of this embodiment is provided with a set of horizontal guide rail slider assemblies and two sets of inclined guide rail slider assemblies on the mounting back plate 103, and the two sets of inclined guide rail slider assemblies are symmetrically arranged on both sides of the horizontal guide rail slider assembly, and the angle between the two sets of inclined guide rail slider assemblies is 120°.

[0052] Preferably, in the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe ends of this embodiment, a first mounting seat is installed on the horizontal guide rail slider assembly, a second mounting seat is installed on each of the two groups of inclined guide rail slider assemblies, and three groups of linear drive mechanisms 14 are installed on the mounting back plate 103, which are respectively used to drive the first mounting seat and the two second mounting seats to move along their respective guide rails. The linear drive mechanism 14 includes a servo motor and a rack and pinion transmission assembly, wherein the rack is fixedly connected to the first mounting seat or the second mounting seat, and the servo motor power output shaft is coaxially connected to the gear, thereby driving the first mounting seat or the second mounting seat to slide along the guide rail where it is located.

[0053] Preferably, in the fluorescent magnetic particle inspection equipment for the inner and outer surfaces of steel pipe ends of this embodiment, the two yoke units of the circumferentially pulsating DC yoke coil assembly 11 are respectively mounted on two second mounting seats. The two yoke units are elastically and floatingly connected to the second mounting seats. Specifically, a guide rod linear bearing assembly parallel to the guide rail on which they are located is provided between the yoke units and the second mounting seats, and a tension spring is connected between the yoke units and the second mounting seats. The tension of the tension spring pulls the yoke units toward the steel pipe. When the yoke units contact or collide with the outer wall of the steel pipe, they elastically float and fit. Furthermore, the elastic avoidance function provides protection against accidental contact or collision between the steel pipe and the magnetic head.

[0054] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end in this embodiment, the longitudinal pulsating DC coil 12 is installed on the first mounting seat, and the magnetic head of the longitudinal pulsating DC coil 12 is slidably arranged on its body along the axis direction of the steel pipe. A compression spring is arranged between its body and the magnetic head, and the magnetic head is elastically pushed by the compression spring to approach the end of the steel pipe. Similarly, when the magnetic head of the longitudinal pulsating DC coil 12 contacts the end of the steel pipe, it plays a role of elastic floating fitting, and at the same time, when the steel pipe touches or collides with the magnetic head by mistake, it can play a protective role through elastic avoidance.

[0055] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end in this embodiment, a cantilever bracket extending along the length direction of the steel pipe is fixedly connected to the bottom of the mounting back plate 103, and the annular pulsating DC guiding magnetic yoke 13 is fixedly connected to the cantilever bracket. During the flaw detection operation, the steel pipe needs to pass through the inner cavity of the annular magnetic conduction structure.

[0056] It should be noted that the inner diameter of the annular pulsating DC guiding magnetic yoke 13 should be greater than the outer diameter of the steel pipe to enable the steel pipe to pass through the inner cavity of the annular pulsating DC guiding magnetic yoke 13 without obstruction.

[0057] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end in this embodiment, the dynamic excitation system includes a pulsating magnetization power supply electrically connected to the composite magnetization assembly. The power supply is configured to output pulsating direct current with a preset frequency and duty cycle, where:

[0058] The pulsating direct current generates a time-varying circumferential magnetic field in the circumferential pulsating DC magnetic yoke coil group 11, and at the same time generates a pulsating oscillating longitudinal magnetic field in the longitudinal pulsating DC coil 12;

[0059] Refer to Figure 7 and Figure 8 , the circumferential magnetic field and the longitudinal magnetic field are magnetically coupled through the annular pulsating DC guiding magnetic yoke 13 to form a three-dimensional rotating dynamic composite magnetic field at the end of the steel pipe.

[0060] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end in this embodiment, the output voltage waveform of the pulsating magnetization power supply includes continuous working cycles, and each cycle includes:

[0061] Stepwise increasing section: The voltage gradually increases from the initial value V0 to the peak value Vmax in an arithmetic sequence, where V0 ∈ [0V, 10V], Vmax ∈ [45V, 50V], and the step size ΔV ∈ [5V, 10V];

[0062] Oscillation maintenance section: After reaching Vmax, the output voltage pulsates and oscillates periodically within the preset oscillation range [Vmax - ΔVd, Vmax] at a frequency f ∈ [10Hz, 100Hz], where ΔVd ∈ [3V, 5V].

[0063] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end in this embodiment, the voltage change rate in the stepwise increasing section can be programmably set to a linear increasing mode or an exponential increasing mode, where the time constant τ of the exponential increasing mode belongs to [0.1 s, 0.5 s].

[0064] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end in this embodiment, the periodic pulsating oscillation waveform in the oscillation maintaining section is at least one of a square wave, a triangular wave, or a sine wave, and there is a zero-voltage interval with a duration t ∈ [10 ms, 50 ms] between adjacent periods.

[0065] The following is a detailed description in combination with specific parameters.

[0066] Embodiment 1: The circuit working process of the non-contact fluorescent magnetic particle flaw detection equipment for the steel pipe end is based on PLC control. A magnetic field is excited through a pulsating magnetization voltage waveform, and defect detection is completed in combination with a feedback mechanism. Combining Figure 2 with the circuit diagram, the following is a step-by-step description of the formation principle and specific operation process of the circumferential pulsating magnetic field:

[0067] a. Power input and system initialization

[0068] After the equipment is powered on, a three-phase AC power supply (L1 / L2 / L3 AC380V) is input into the main circuit through a circuit breaker, and a fuse provides short-circuit protection;

[0069] The PLC, touch screen, and sensor are powered on and started. The touch screen loads the human-machine interface and displays the default parameters (V0 = 0V, Vmax = 50V, ΔV = 50V);

[0070] The PLC detects the status of the SCR module, the contacts of the thermal relay (FR), and the feedback signal of the ammeter. After confirming no faults, it enters the standby mode.

[0071] b. Operator input

[0072] Set the detection parameters through the touch screen:

[0073] Stepwise increasing section: Select the linear / exponential increasing mode and set V0, Vmax, ΔV (or the time constant τ).

[0074] Oscillation maintaining section: Select the waveform type (square wave, frequency f, oscillation amplitude ΔVd, and zero-voltage interval t.

[0075] Start instruction:

[0076] Click the "Start" button, and the PLC sends an enabling signal to the SCR trigger circuit. The main circuit breaker closes, and the equipment enters the operating state.

[0077] Stepwise increasing section: The voltage is gradually increased, and the PLC outputs an instruction:

[0078] Linear increase: The PLC outputs voltage commands with an equal difference (V0 → V0+ΔV →...→ Vmax) at a fixed time interval (150 ms / step).

[0079] The PLC outputs a linear increase command to control the SCR firing angle to gradually decrease at a fixed time interval (150 ms / step), so that the main circuit current increases from V0 = 0V to Vmax = 50V in an arithmetic sequence (ΔV = 5V / step).

[0080] The ammeter monitors the excitation current in real time. If the detected current exceeds the threshold value Imax = 150A, the PLC immediately triggers an alarm and pauses the increase.

[0081] Oscillation maintenance section: The PLC switches to the square wave output mode, periodically switches the voltage command (50V - 45V) at a frequency f = 100Hz, and the duty cycle is 50% (i.e., 10ms per cycle).

[0082] After each square wave cycle ends, the PLC inserts a zero voltage interval (t = 5ms), the SCR trigger circuit is completely turned off, and the main circuit current returns to zero to eliminate the residual magnetic field. Refer to the waveform diagram Figure 4 (Linear increase + square wave oscillation waveform, total duration 2.348 seconds, sampling points 2295).

[0083] The fluorescent magnetic particle spraying device sprays the magnetic suspension during the zero voltage interval, and the alternating magnetic field drives the magnetic particles to flow on the surface of the steel pipe, and the cracks are clearly imaged under the ultraviolet lamp.

[0084] Magnetic field pulsation effect: The periodically changing voltage causes the magnetization coil to generate an alternating magnetic field, the magnetic particles flow on the surface of the steel pipe and gather at the cracks, and the fluorescent imaging enhances the visibility of the defects.

[0085] Example 2: Refer to Figure 5 the waveform diagram (exponential increase + triangular wave, total duration 2.376 seconds, sampling points 2290). Different from Example 1, in the stepwise increase section, the PLC selects the exponential increase mode and dynamically adjusts the output voltage according to the formula V(t) = Vmax-(Vmax-V0) * e^(-t / τ) (τ = 0.15s), so that the voltage quickly approaches Vmax = 50V from V0 = 0V.

[0086] The SCR firing angle is adjusted according to the exponential law, and the conduction time gradually increases, and the main circuit current rises smoothly.

[0087] Oscillation maintenance section (ramp triangular wave mode): The PLC generates a triangular wave signal, the voltage linearly decreases from 50V to 45V (ΔVd = 5V), and then rises back to 50V, the period T = 1 / f = 10ms (f = 100Hz), and the rise / fall time is 5ms each.

[0088] After each triangular wave cycle, a zero-voltage interval (t = 30 ms) is inserted to ensure complete reset of the magnetic field.

[0089] Feedback optimization: The magnetic field intensity feedback module collects the magnetic field data at the end of the steel pipe in real time. If the intensity is lower than the set value (e.g., when the detected wall thickness of the steel pipe > 15 mm), the PLC automatically increases ΔVd to 6V to improve the sensitivity.

[0090] Example 3: Refer to Figure 6 the waveform diagram (sine wave with zero interval, total duration 2.29 seconds, sampling points 2300). Different from Example 1 and 2, in this example, the oscillation maintenance section uses a sine wave mode: The PLC calls the built-in DDS module to generate a sine modulation signal with a frequency f = 100 Hz and an amplitude ΔVd = 5V, which is superimposed on the reference voltage Vbase = 47.5V, that is, V(t) = 47.5 + 2.5sin(2π×100t), to form a complete sine wave output.

[0091] Among them, 5 ms of zero voltage is inserted every 5 sine cycles (50 ms), and it is in the zero voltage state for 9.1% of the time. The phase continuity of the sine wave is ensured by the DDS module to avoid waveform distortion.

[0092] Dynamic adjustment: The ammeter and the magnetic field intensity feedback module are data-fused, and the PLC dynamically adjusts f (10 Hz~100 Hz) and ΔVd (3V~5V) according to the real-time detection results to optimize the defect detection rate of different pipe diameters.

[0093] Safety protection: If it is detected that the SCR trigger circuit is overheated or the current suddenly changes, the PLC immediately cuts off the main circuit and starts the emergency cooling system.

[0094] The working principle and operation process of the longitudinal pulsating magnetic field are the same as those of the circumferential pulsating magnetic field, so they will not be elaborated here. The circuit control diagram refers to Figure 3 .

[0095] The working process of this equipment is as follows:

[0096] (1) Taking the detection of a steel pipe with an outer diameter of 150 mm as an example, the steel pipe is horizontally hoisted and placed on the auxiliary clamping position (V-shaped support seat) outside the frame 10, and the pipe end is fixed by a pneumatic clamp to ensure that its axis is concentric with the annular pulsating DC guiding yoke structure.

[0097] (2) Input the steel pipe parameters (outer diameter 150 mm, wall thickness 10 mm) at the control terminal, and the system automatically generates the following parameter configurations: The displacement of the linear drive mechanism 14 is 350 mm (so that the circumferential yoke coil group 11 is 5 mm away from the steel pipe surface), driven by a servo motor, and the positioning accuracy is ±0.1 mm.

[0098] Stepped increasing section of the pulsating magnetization power supply: Initial voltage V0 = 0V, peak voltage Vmax = 50V, step size ΔV = 5V, using a linear increasing mode (time constant τ = 0.3s);

[0099] Oscillation maintenance section: Sinusoidal oscillation, frequency f = 100Hz, oscillation range 45V, 50V (ΔVd = 5V), zero voltage interval t = 30ms.

[0100] (3) Generation and magnetization process of the composite rotating magnetic field. Taking the composite magnetic field of Example 3 as an example, refer to Figure 8 (Distribution diagram of the three-dimensional rotating composite magnetic field at the end of the steel pipe, coupling effect of circumferential magnetic field and longitudinal magnetic field).

[0101] Longitudinal magnetic field excitation: A pulsating direct current is passed through the longitudinal yoke coil 12, and the initial magnetic field intensity is 1.8T (in the axial direction of the steel pipe). Through the closed magnetic conduction loop of the annular pulsating direct current guiding yoke 13, the magnetic field is guided to the end of the steel pipe, and the intensity is increased to 2.5T (outer surface) and 2.0T (inner surface).

[0102] Circumferential magnetic field regulation: The two independent yoke units of the circumferential yoke coil group 11 are synchronously moved radially along the annular magnetic conduction structure to the 350mm position under the drive of the servo motor to form a magnetization channel adapted to the outer diameter of the steel pipe. After passing a time-varying current, a circumferential magnetic field with a peak intensity of 2.0T is generated.

[0103] Three-dimensional rotating dynamic composite magnetic field coupling: The longitudinal magnetic field and the circumferential magnetic field are coupled through the annular pulsating direct current guiding yoke 13 to form a spiral three-dimensional dynamic magnetic field at the end of the steel pipe (as Figure 8 shown), the magnetic field covers the inner and outer surfaces of the steel pipe, and the intensity gradient decreases from the pipe end to the pipe body direction (the peak value in the pipe end area reaches 2.5T).

[0104] (4) After magnetization is started, the built-in high-pressure spray gun of the equipment evenly sprays the fluorescent magnetic powder suspension (magnetic powder particle size 3 - 5μm) onto the inner and outer surfaces of the steel pipe end. The spray gun angle matches the magnetic field direction to ensure that the magnetic powder accumulates along the defect leakage magnetic field.

[0105] Dynamic magnetic field regulation: Stepped increasing stage: The voltage linearly increases from 0V to 50V (taking 1.5s), the magnetic field intensity gradually increases, penetrates the steel pipe wall thickness and initially adsorbs the magnetic powder;

[0106] Oscillation maintenance stage: Sinusoidal oscillation (100Hz) combined with zero voltage interval (30ms), periodically switching the magnetic field intensity, eliminating the magnetic powder residue in the non-defect area, and at the same time enhancing the magnetic trace contrast of micro-cracks.

[0107] (5) Ultraviolet excitation and image acquisition

[0108] The surface of the steel pipe is irradiated with an ultraviolet lamp (wavelength 365 nm) to excite the fluorescent magnetic powder to emit light. An integrated CCD camera captures high-definition images at a rate of 30 fps to ensure dynamic capture of magnetic marks.

[0109] Image processing and defect recognition: The image processing unit adopts the following process. Noise reduction: Median filtering is used to eliminate background noise. Edge detection: The Canny algorithm is used to extract the contour of the magnetic mark. Quantitative analysis: Calculate the defect length (accuracy ±0.2 mm) and depth (based on the inversion model of magnetic mark width and magnetic field strength).

[0110] Result output: The detection report is automatically generated, including the defect location (polar coordinates), size and confidence level. If a crack with a length > 2 mm is detected, the system triggers an audible and visual alarm and marks it as a "critical defect".

[0111] (6) Equipment reset and cyclic detection

[0112] Magnetic field shutdown and mechanism reset: After the magnetization power supply is cut off, the circumferential magnetic yoke coil group 11 returns to its initial position under the drive of the servo motor, and the pneumatic fixture releases the steel pipe.

[0113] Automated cycle: The inspected steel pipe is removed through the conveyor roller table, and the next steel pipe automatically enters the working station. The whole process takes ≤  120 seconds and supports continuous detection.

[0114] Inspired by the ideal embodiments of the present application described above, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this application. The technical scope of this application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. Fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the pipe ends of steel pipes, characterized in that, Comprising: A frame (10), constituting the main support structure of the device; A composite magnetization assembly, including a circumferential pulsating DC yoke coil group (11), a longitudinal pulsating DC coil (12), and an annular pulsating DC guiding yoke (13) disposed on the frame (10), wherein: The annular pulsating DC guiding yoke (13) has an annular magnetic conduction structure concentric with the axis of the steel pipe, configured to conduct the magnetic circuit of the axial magnetic field generated by the longitudinal pulsating DC coil (12) and gradually increase the magnetic field intensity; The circumferential pulsating DC yoke coil group (11) includes two symmetrically arranged independent yoke units, and each yoke unit is movably disposed in the radial direction of the annular pulsating DC guiding yoke (13) through a linear driving mechanism (14) to form an adjustable circumferential magnetization channel; A dynamic excitation system, including a pulsating magnetization power supply electrically connected to the composite magnetization assembly, and the power supply is configured to output pulsating direct current with a preset frequency and duty cycle, wherein: The pulsating direct current generates a time-varying circumferential magnetic field in the circumferential pulsating DC yoke coil group (11), and simultaneously generates a pulsating oscillating longitudinal magnetic field in the longitudinal pulsating DC coil (12); The circumferential magnetic field and the longitudinal magnetic field are magnetically coupled through the annular pulsating DC guiding yoke (13) to form a three-dimensional rotating dynamic composite magnetic field at the end of the steel pipe.

2. The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end according to claim 1, characterized in that, The output voltage waveform of the pulsating magnetization power supply includes continuous working cycles, and each cycle includes: A stepwise increasing section: The voltage is gradually increased from an initial value V0 to a peak value Vmax in an arithmetic sequence, where V0 ∈ [0V, 10V], Vmax ∈ [45V, 50V], and the step size ΔV ∈ [5V, 10V]; An oscillating maintaining section: After reaching Vmax, the output voltage pulsates periodically within a preset oscillation interval [Vmax - ΔVd, Vmax] at a frequency f ∈ [10Hz, 100Hz], where ΔVd ∈ [3V, 5V].

3. The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end according to claim 2, characterized in that, The voltage change rate of the stepwise increasing section can be programmably set to a linear increasing mode or an exponential increasing mode, and the time constant τ of the exponential increasing mode ∈ [0.1s, 0.5s].

4. The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end according to claim 2, characterized in that, The periodic pulsating oscillation waveform of the oscillating maintaining section is at least one of a square wave, a triangular wave, or a sine wave, and there is a zero voltage interval with a duration t ∈ [10ms, 50ms] between adjacent cycles.

5. The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end according to any one of claims 1-4, characterized in that, The frame (10) includes a chassis (101) and a moving frame (102), the moving frame (102) is slidably disposed on the chassis (101) along the axis direction of the steel pipe, and a liftable and slidable mounting backboard (103) is disposed on the moving frame (102).

6. The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end according to claim 5, characterized in that, The longitudinal pulsating DC coil (12) is horizontally slidably disposed on the mounting backboard (103) for detecting the internal and external surfaces of steel pipes with different diameters and wall thicknesses.

7. The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end according to claim 6, characterized in that, The two yoke units of the circumferential pulsating DC yoke coil group (11) are slidably disposed on the mounting backboard (103), and the included angle between the two yoke units is 120°.

8. The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end according to claim 7, characterized in that, A cantilever bracket is fixed at the bottom of the mounting backboard (103), and the annular pulsating DC guiding yoke (13) is fixedly disposed on the cantilever bracket.

9. The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end according to claim 1, characterized in that, The magnetic head of the yoke unit is elastically and floatingly connected to its mounting seat, and the floating direction is parallel to the radial direction of the steel pipe.

10. The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end according to claim 1, characterized in that, The longitudinal pulsating DC coil (12) is elastically and floatingly connected to its mounting seat, and the floating direction is parallel to the axis of the steel pipe.

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