Fluorescent magnetic powder inspection equipment for inner and outer surfaces of pipe end of steel pipe

Abstract

The invention relates to the technical field of magnetic powder inspection equipment, in particular to fluorescent magnetic powder inspection equipment for the inner surface and the outer surface of the pipe end of a steel pipe. The problem of non-uniform magnetic field distribution of traditional equipment in a pipe end area is effectively solved, and dead-angle-free detection of inner and outer surfaces is realized; the stepped increasing section and the oscillation maintaining section of the pulsating magnetization power supply adjust the magnetic field intensity to change along with time, so that the magnetic field can penetrate through the wall thickness of the steel pipe in the detection process, and the problem of magnetic saturation can be avoided; the radial position of the circumferential magnet yoke coil assembly and the axial position of the longitudinal magnet yoke can be adjusted in a programmable mode, and detection of a steel pipe with the outer diameter ranging from 80 mm to 820 mm is supported; the inner surface and the outer surface are synchronously detected through the single composite magnetization assembly, the design of two sets of independent magnetization devices in the traditional technology is avoided, and the cost is reduced.

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. By synchronously moving the magnetization device and the nozzle device along the circumferential direction of the pipeline to form a dynamic magnetization area, the problem of the blind area caused by uneven magnetic field distribution is solved. However, it is necessary to realize the synchronous movement of the magnetic field and the nozzle device through a frequency conversion 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 strength only depends on the current amplitude, and the dynamic characteristics of the magnetic field cannot be adjusted flexibly; 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: The fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the pipe ends of steel pipes includes: A frame, constituting the main support structure of the equipment; 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: The annular pulsating DC guiding yoke has an annular magnetic conduction structure concentric with the axis of the steel pipe, configured to guide the axial magnetic field generated by the longitudinal pulsating DC coil and gradually increase the magnetic field strength; 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; 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: When the pulsating direct current is generated in the circumferential pulsating DC yoke coil group, a time-varying circumferential magnetic field is generated, and at the same time, a pulsating oscillating longitudinal magnetic field is generated in the longitudinal pulsating DC coil; 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.

[0006] 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 output voltage waveform of the pulsating magnetization power supply includes continuous working cycles, and each cycle includes: Stepped increasing section: The voltage gradually increases from the initial value V0 to the peak value Vmax in an arithmetic sequence, where V0 ∈ [5V, 10V], Vmax ∈ [45V, 50V], and the step size ΔV ∈ [5V, 10V]; Oscillation maintenance 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].

[0007] 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 voltage change rate of the stepped increasing section can be programmed to be set in a linear increasing mode or an exponential increasing mode, where the time constant τ of the exponential increasing mode ∈ [0.1s, 0.5s].

[0008] 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 periodic pulsating oscillation waveform of the oscillation maintenance 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.

[0009] 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 frame includes a chassis and a moving frame. The moving frame is slidably arranged on the chassis along the axis direction of the steel pipe, and a liftable and slidable mounting backboard is arranged on the moving frame.

[0010] 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 horizontally slidably arranged on the mounting backboard for adapting to the flaw detection of the inner and outer surfaces of steel pipes with different diameters and wall thicknesses.

[0011] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe end of the present invention, 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°.

[0012] 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 at the bottom of the installation backboard, and the annular pulsating DC guiding magnetic yoke is fixedly arranged on the cantilever bracket.

[0013] 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 magnetic 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.

[0014] 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.

[0015] The beneficial effects of the present invention are as follows: (1) 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 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; (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; (3) The closed magnetic circuit design of the annular magnetic conductive structure significantly improves the longitudinal magnetic field strength and enhances the magnetic particle aggregation ability for micro defects; (4) The radial position of the circumferential magnetic yoke coil group and the axial position of the longitudinal magnetic yoke can be programmably adjusted, supporting the detection of steel pipes with an outer diameter ranging from 80 mm to 820 mm; (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

[0016] The technical solutions of the present application will be further described below with reference to the drawings and embodiments.

[0017] Figure 1 It is a schematic diagram of the equipment body structure of Embodiments 1-3 of the present application; Figure 2 It is a schematic diagram of the control principle of the circumferential magnetic yoke circuit of Embodiments 1-3 of the present application; Figure 3 It is a schematic diagram of the control principle of the longitudinal coil and magnetic yoke circuit of Embodiments 1-3 of the present application; Figure 4 It is a schematic diagram of the pulsating change of voltage with time in Embodiment 1 of the present application; Figure 5 It is a schematic diagram of the pulsating change of voltage with time in Embodiment 2 of the present application; Figure 6It is a schematic diagram showing the pulsating change of voltage over time in Embodiment 3 of the present application; Figure 7 It is a schematic plan view of the magnetic field distribution in Embodiments 1 - 3 of the present application; Figure 8 It is a schematic diagram of the three - dimensional rotating composite magnetic field distribution in Embodiment 3 of the present application; The reference numerals in the figure are: Frame 10, circumferential pulsating DC yoke coil group 11, longitudinal pulsating DC coil 12, annular pulsating DC guiding yoke 13, linear drive mechanism 14; Chassis 101, moving frame 102, mounting backplane 103, driving cylinder 104. Detailed implementation manners

[0018] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0019] 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. It 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 specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may 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.

[0020] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection", "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0021] The technical solutions of the present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0022] 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.

[0023] 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 axial magnetic field generated by the longitudinal pulsating DC coil 12 and gradually increase the magnetic field strength; the annular magnetic conduction structure forms a closed magnetic circuit with a high magnetic permeability material (silicon steel or soft magnetic alloy), confining 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, ensuring that the magnetic field acts concentratedly on the end region of the steel pipe, especially optimizing the magnetic circuit distribution for the detection requirements of the inner and outer surfaces. At the end of the annular magnetic conduction structure (near the end region of the steel pipe), the magnetic field strength reaches a peak due to the concentration and superposition effects of the magnetic circuit, ensuring a high-sensitivity aggregation of fluorescent magnetic particles at the defects.

[0024] The circumferential pulsating DC yoke coil group 11 includes two symmetrically arranged independent yoke units. Each yoke unit is movably arranged in the radial direction of the annular pulsating DC guiding yoke 13 through a linear driving mechanism 14, forming an adjustable circumferential magnetization channel.

[0025] Specifically, the frame 10 constitutes the main support structure of the equipment. The frame 10 includes a chassis 101 and a moving frame 102. The moving frame 102 is slidably arranged on the chassis 101 along the axis direction of the steel pipe through a guide rail slider assembly. A driving cylinder 104 is arranged between the chassis 101 and the moving frame 102 to drive the moving frame 102 to slide on the chassis 101. An installable backboard 103 that can be lifted and slid is arranged on the moving frame 102 through a guide rail slider assembly. A first lead screw nut transmission mechanism is arranged between the installable backboard 103 and the moving frame 102, and the first servo motor drives the first lead screw nut transmission mechanism to drive the installable backboard 103 to perform a lifting action.

[0026] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the pipe ends of this embodiment, a set of horizontal guide rail slider assemblies and two sets of inclined guide rail slider assemblies are arranged on the installable backboard 103. The two sets of inclined guide rail slider assemblies are symmetrically arranged on both sides of the horizontal guide rail slider assembly, and the included angle between the two sets of inclined guide rail slider assemblies is 120°.

[0027] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe ends in this embodiment, a first mounting seat is installed on the horizontal guide rail slider assembly, and a second mounting seat is installed on each of the two inclined guide rail slider assemblies. Three linear drive mechanisms 14 are installed on the mounting backboard 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 gear-rack transmission component. Among them, the rack is fixedly connected to the first mounting seat or the second mounting seat, and the power output shaft of the servo motor is coaxially connected to the gear, so as to drive the first mounting seat or the second mounting seat to slide along its guide rail.

[0028] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe ends in this embodiment, the two magnetic yoke units of the circumferential pulsating DC magnetic yoke coil group 11 are respectively installed on the two second mounting seats, and an elastic floating connection is adopted between the two magnetic yoke units and the second mounting seats. Its specific structure is provided with a guide rod linear bearing assembly parallel to the direction of its guide rail between the magnetic yoke unit and the second mounting seat, and a tension spring is connected between the magnetic yoke unit and the second mounting seat. The magnetic yoke unit is pulled close to the steel pipe by the tension of the tension spring. When the magnetic yoke unit contacts or collides with the outer wall of the steel pipe, it plays the role of elastic floating fitting. At the same time, when the steel pipe accidentally touches or collides with the magnetic head, it can play a protective role through elastic avoidance.

[0029] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe ends 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 close to the end of the steel pipe through the compression spring. Similarly, when the magnetic head of the longitudinal pulsating DC coil 12 contacts the end of the steel pipe, it plays the role of elastic floating fitting. At the same time, when the steel pipe accidentally touches or collides with the magnetic head, it can play a protective role through elastic avoidance.

[0030] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe ends in this embodiment, a cantilever bracket extending along the length direction of the steel pipe is fixedly connected to the bottom of the mounting backboard 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.

[0031] It should be noted that the inner diameter of the annular pulsating DC guiding magnetic yoke 13 should be larger 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.

[0032] Preferably, for the fluorescent magnetic particle flaw detection equipment for the inner and outer surfaces of the steel pipe ends in this embodiment, the dynamic excitation system includes a pulsating magnetization power supply electrically connected to the composite magnetization component. The power supply is configured to output pulsating direct current with a preset frequency and duty cycle, where: When pulsating direct current is generated in the circumferential pulsating direct current yoke coil group 11, a time-varying circumferential magnetic field is generated, and at the same time, a pulsating oscillating longitudinal magnetic field is generated in the longitudinal pulsating direct current coil 12; Refer to Figure 7 and Figure 8 , the circumferential magnetic field and the longitudinal magnetic field are magnetically coupled through the annular pulsating direct current guiding yoke 13 to form a three-dimensional rotating dynamic composite magnetic field at the end of the steel pipe.

[0033] Preferably, for the fluorescent magnetic particle flaw detection equipment on the inner and outer surfaces of the end of the steel pipe in this embodiment, the output voltage waveform of the pulsating magnetization power supply includes continuous working cycles, and each cycle includes: Stepped increasing section: The voltage is gradually increased 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]; Oscillation maintenance section: After reaching Vmax, the output voltage pulsates periodically within the preset oscillation range [Vmax - ΔVd, Vmax] at a frequency f ∈ [10Hz, 100Hz], where ΔVd ∈ [3V, 5V].

[0034] Preferably, for the fluorescent magnetic particle flaw detection equipment on the inner and outer surfaces of the end of the steel pipe in this embodiment, the voltage change rate in the stepped 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 ∈ [0.1s, 0.5s].

[0035] Preferably, for the fluorescent magnetic particle flaw detection equipment on the inner and outer surfaces of the end of the steel pipe in this embodiment, the periodic pulsating oscillation waveform in the oscillation maintenance 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.

[0036] The following is a detailed description in combination with specific parameters.

[0037] Embodiment 1: The circuit working process of this non-contact fluorescent magnetic particle flaw detection equipment for the end of the steel pipe is based on PLC control. The magnetic field is excited through the pulsating magnetization voltage waveform, and the defect detection is completed in combination with the 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: a. Power input and system initialization After the equipment is powered on, the three-phase AC power supply (L1 / L2 / L3 AC380V) is input into the main circuit through the circuit breaker, and the fuse provides short-circuit protection; 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); 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.

[0038] b. Operator input Set the detection parameters through the touch screen: Stepped increase section: Select the linear / exponential increase mode and set V0, Vmax, ΔV (or time constant τ).

[0039] Oscillation maintenance section: Select the waveform type (square wave, frequency f, oscillation amplitude ΔVd, and zero voltage interval t).

[0040] Start instruction: Click the "Start" button. The PLC sends an enable signal to the SCR trigger circuit, the main circuit breaker closes, and the device enters the operating state.

[0041] Stepped increase section: The voltage is gradually increased. The PLC outputs instructions: Linear increase: The PLC outputs arithmetic voltage instructions (V0 → V0 + ΔV →... → Vmax) at a fixed time interval (150 ms / step).

[0042] The PLC outputs linear increase instructions and controls the SCR trigger 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).

[0043] 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.

[0044] Oscillation maintenance section: The PLC switches to the square wave output mode and periodically switches the voltage instructions (50V - 45V) at a frequency f = 100Hz, with a duty cycle of 50% (i.e., 10 ms per cycle).

[0045] 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. The waveform diagram refers to Figure 4 (Linear increase + square wave oscillation waveform, total duration 2.348 seconds, sampling points 2295).

[0046] The fluorescent magnetic particle spraying device sprays the magnetic suspension liquid during the zero voltage interval. 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.

[0047] 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, enhancing the visibility of the defects through fluorescent imaging.

[0048] Example 2: Refer to Figure 5 the waveform diagram (exponential increase + triangular wave, total duration 2.376 s, 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 = 0.15 s), so that the voltage rapidly approaches Vmax = 50 V from V0 = 0 V.

[0049] The SCR firing angle is adjusted according to an exponential law, and the conduction time gradually extends, and the main circuit current rises smoothly.

[0050] Oscillation maintenance section (ramp triangular wave mode): The PLC generates a triangular wave signal, the voltage linearly drops from 50 V to 45 V (ΔVd = 5 V), and then rises back to 50 V. The period T = 1 / f = 10 ms (f = 100 Hz), and the rise / fall time is 5 ms each.

[0051] A zero voltage interval (t = 30 ms) is inserted after each triangular wave period to ensure complete magnetic field reset.

[0052] Feedback optimization: The magnetic field intensity feedback module real-time collects the magnetic field data at the end of the steel pipe. If the intensity is lower than the set value (such as when it is detected that the wall thickness of the steel pipe > 15 mm), the PLC automatically increases ΔVd to 6 V to improve the sensitivity.

[0053] Example 3: Refer to Figure 6 the waveform diagram (sine wave with zero interval, total duration 2.29 s, sampling points 2300). Different from Examples 1 and 2, in this example, the sine wave mode is adopted in the oscillation maintenance section: The PLC calls the built-in DDS module to generate a sine modulation signal with a frequency f = 100 Hz and an amplitude ΔVd = 5 V, which is superimposed on the reference voltage Vbase = 47.5 V, that is, V(t)=47.5 + 2.5sin(2π×100t), to form a complete sine wave output.

[0054] Among them, 5 ms of zero voltage is inserted every 5 sine periods (50 ms), and 9.1% of the time is in the zero voltage state. The phase continuity of the sine wave is guaranteed by the DDS module to avoid waveform distortion.

[0055] Dynamic adjustment: The data of the ammeter and the magnetic field intensity feedback module are fused, and the PLC dynamically adjusts f (10 Hz~100 Hz) and ΔVd (3 V~5 V) according to the real-time detection results to optimize the defect detection rate of different pipe diameters.

[0056] 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.

[0057] 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. Refer to the circuit control diagram Figure 3 .

[0058] The working process of this equipment is as follows: (1) Taking the inspection 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 ends are fixed by pneumatic clamps to ensure that its axis is concentric with the annular pulsating DC guiding magnetic yoke structure.

[0059] (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 distance between the circumferential magnetic yoke coil group 11 and the steel pipe surface is 5 mm), driven by a servo motor, and the positioning accuracy is ±0.1 mm.

[0060] The stepped increasing section of the pulsating magnetization power supply: the initial voltage V0 = 0 V, the peak voltage Vmax = 50 V, the step size ΔV = 5 V, adopting a linear increasing mode (time constant τ = 0.3 s); The oscillation maintenance section: sinusoidal oscillation, frequency f = 100 Hz, oscillation range 45 V, 50 V (ΔVd = 5 V), zero voltage interval t = 30 ms.

[0061] (3) The generation and magnetization process of the composite rotating magnetic field. Taking the composite magnetic field of Embodiment 3 as an example, refer to Figure 8 (Three-dimensional rotating composite magnetic field distribution diagram at the end of the steel pipe, coupling effect of circumferential magnetic field and longitudinal magnetic field).

[0062] Longitudinal magnetic field excitation: A pulsating direct current is passed through the longitudinal magnetic yoke coil 12, and the initial magnetic field intensity is 1.8 T (in the axial direction of the steel pipe). Through the closed magnetic conduction loop of the annular pulsating DC guiding magnetic yoke 13, the magnetic field is guided to the end of the steel pipe, and the intensity is enhanced to 2.5 T (outer surface) and 2.0 T (inner surface).

[0063] Circumferential magnetic field adjustment: The two independent magnetic yoke units of the circumferential magnetic yoke coil group 11 are synchronously moved to the 350 mm position along the radial direction of the annular magnetic conduction structure 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 2.0 T is generated.

[0064] Three-dimensional rotating dynamic composite magnetic field coupling: The longitudinal magnetic field and the circumferential magnetic field are coupled through the annular pulsating DC guiding magnetic 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 2.5 T).

[0065] After magnetization is started, the built-in high-pressure spray gun of the device evenly sprays the fluorescent magnetic particle suspension (magnetic particle size 3 - 5μm) onto the inner and outer surfaces of the steel pipe end. The spray gun angle is matched with the magnetic field direction to ensure that the magnetic particles gather along the defect leakage magnetic field.

[0066] 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 magnetic particles; Oscillation maintenance stage: Sinusoidal wave oscillation (100Hz) is combined with a zero-voltage interval (30ms), the magnetic field intensity is periodically switched to eliminate magnetic particle residues in non-defect areas, and at the same time enhance the magnetic trace contrast of micro-cracks.

[0067] (5) Ultraviolet excitation and image acquisition The ultraviolet lamp (wavelength 365nm) irradiates the steel pipe surface to excite the fluorescent magnetic particles to emit light. The integrated CCD camera captures high-definition images at a rate of 30fps to ensure dynamic capture of magnetic traces.

[0068] Image processing and defect recognition: The image processing unit adopts the following process, noise reduction: Median filtering to eliminate background noise; Edge detection: Canny algorithm to extract the magnetic trace contour; Quantitative analysis: Calculate the defect length (accuracy ±0.2mm), depth (based on the magnetic trace width and magnetic field intensity inversion model).

[0069] Result output: The detection report is automatically generated, including the defect location (polar coordinates), size and confidence level. If a crack with a length > 2mm is detected, the system triggers an audible and visual alarm and marks it as a "critical defect".

[0070] (6) Equipment reset and cyclic detection Magnetic field shutdown and mechanism reset: After the magnetization power supply is cut off, the circumferential magnetic yoke coil group 11 returns to the initial position driven by the servo motor, and the pneumatic fixture releases the steel pipe.

[0071] Automated cycle: The inspected steel pipe is removed through the conveyor roller table, and the next steel pipe automatically enters the station. The whole process takes ≤120 seconds and supports continuous detection.

[0072] 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 end of a steel pipe, 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) arranged 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 path of the axial magnetic field generated by the longitudinal pulsating DC coil (12) and gradually enhance 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 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; 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 stepped 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 oscillating range [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 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].

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 arranged on the chassis (101) along the axis direction of the steel pipe, and a liftable and slidable mounting backplane (103) is arranged 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 arranged on the mounting backplane (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 arranged on the mounting backplane (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 backplane (103), and the annular pulsating DC guiding yoke (13) is fixedly arranged 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, wherein, 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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