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1. Scope of application 1.1 This process is applicable only to the inspection of surface and near-surface defects in workpieces. 1.2 This process is applicable to: a) ferromagnetic workpieces. b) Alternating current, yoke method or rotating magnetic field wet continuous non-fluorescent testing. 2. Flaw detection personnel: Those engaged in magnetic particle inspection must receive technical training and hold a qualification certificate of level II or above issued by the Non-Destructive Testing Committee of the Ministry of Labor. 3. Execution standard: Chapter 4 of JB4730. 4. Selection of equipment, magnetic powder, and sensitivity test pieces. 4.1 Equipment: a) For the magnetic particle method, magnetic particle flaw detectors of the models B310OPD, MP-A3, and DE-EDⅡ should be used; when the pole spacing is 200 mm, the lifting force should be at least 44 N. b) Transverse magnetic field method: A magnetic particle flaw detector of model DE-EDⅡ is used. 4.2 Magnetic Powder: Black magnetic paste produced by the Shanghai Materials Research Society is used, with water as the medium; the concentration of the magnetic suspension is 10–20 g/1. 4.3 Sensitivity test pieces: Type A (30/100) shall be used. 5. Requirements for the working surface: The surface of the workpiece to be inspected must be clean, free of grease, rust, scale, coatings, flux, and welding spatter. Inspection by ultrasonic testing can only be carried out after the surface has passed a visual inspection. 6. Timing of inspection: It is carried out before and after the post-weld pressure test. 7. Inspection steps 7.1 Before inspection, place the side of the Type A test piece without artificial defects facing outward, and attach it smoothly to the surface of the workpiece under inspection using transparent tape; make sure that the tape does not cover the artificial defects on the test piece. 7.2 To increase the detection rate, a layer of contrast enhancer is applied to the surface of the workpiece (including the test piece), with a thickness of no more than 20 μm. 7.3 Use a pressure sprayer to apply the magnetic suspension. During operation, ensure that the entire inspection surface is properly wetted by the magnetic suspension before applying it. The application of the magnetic suspension must be completed within the power-on time, which is 1–3 seconds; after stopping the application for 1 second, cease magnetization. The flow rate of the magnetic suspension on the inspection surface should not be too fast, in order to prevent the magnetic marks formed from being disrupted by the flowing magnetic suspension. 7.4 Magnetization direction and overlap ratio 7.4.1 Yoke method: The weld surface shall be subjected to magnetization testing in at least two different directions; the magnetic field lines in these two directions should be perpendicular to each other. The magnetic spacing is 50–200 mm, and the effective testing area extends 50 mm on either side of the line connecting the poles. Within this area, there should be an overlap of 15 mm between the magnetized regions each time. 7.4.2 Rotating magnetic field: The magnetized areas should overlap by 15 mm each time. 8 Re-inspection: A re-inspection is required in any of the following situations: a) The sensitivity test using a sensitivity gauge shows that the sensitivity is not satisfactory; b) There is a dispute between the supplier and the buyer, or if it is deemed necessary for other reasons; c) In the case of areas that have been repaired. 9. Assessment of the severity level of defect indications 9.1 Classification of defect indication traces: a) Unless it can be confirmed that the indication trace is caused by external factors or improper operation, any indication trace of 0.5 mm or more should be considered a defect indication trace. b) Defects with a length-to-width ratio greater than 3 that show traces are treated as linear defects. c) When the angle between the long axis of the defect flaw and the workpiece axis or generatrix is greater than 30°, it is treated as a transverse defect; otherwise, it is treated as a longitudinal defect. d) When two or more defective magnetic marks are on the same straight line and the distance between them is 2 mm or less, they are treated as one defect, with its length being the sum of the lengths of the two defects plus the distance between them. e) Defect magnetic traces with a length of less than 0.5 mm are not counted; the number and location of all magnetic traces must be recorded. 9.2 The following defects are not permitted: a) white spots with any cracks; b) any transverse defects; c) linear defects on the weld with a length greater than 1.5 mm; d) circular defects with a single dimension equal to or greater than 4 mm. 9.3 The grading of the cumulative length of defect indications is based on Table 9.3: Table 9.3 Assessment Dimensions 35×100 Grade I II ≤2 III ≤4 IV ≤8 V Greater than Grade IV 10. Acceptable inspection grade: Grade I