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1.0 Purpose and Scope of Application 1.1 Purpose: This procedure is established to ensure the quality of magnetic particle inspection and to provide accurate and reliable inspection data. 1.2 Scope of Application 1.1 These regulations apply to the detection and grading of surface or near-surface defects in equipment and its components made of ferromagnetic materials ； 1.2 These regulations apply to the methods and requirements for continuous electromagnetic yoke flux density testing and coil magnetization. 2.0 Basis for Preparation 2.1 This procedure is formulated in accordance with JB/T4730-2005.4 \"Non-destructive Testing of Pressure Equipment\" ； 2.2 This procedure is formulated with reference to \"Magnetic Particle Testing\" compiled by the Qualification Assessment Committee for Non-Destructive Testing Personnel of Boilers and Pressure Vessels. 3.0 Inspection Equipment and Materials 3.1 The equipment selected for this procedure is as follows: 3.1.1 AC electromagnetic yoke-type magnetic particle detector 3.1.2 Coil magnetization method ； 3.2 To ensure the reliability of magnetic particle inspection results, magnetic particle flaw detectors must be calibrated regularly, and random calibration may be carried out when necessary ； 3.3 Verification of the yoke lifting force: For portable AC yoke-type magnetic particle flaw detectors (with a yoke spacing of ≤200 mm), the lifting force must be at least 45 N (approximately 4.5 kg) ； 3.4 Magnetic Powder and Magnetic Suspension 3.4.1 Magnetic powder should have high magnetic permeability and low residual magnetism; it should not attract to each other. Common types include Fe3O4 and Fe2O3. Our company uses spray-can type black oil magnetic suspension and wet fluorescent magnetic powder ； 3.4.2 The particle size of magnetic powder should be uniform; the average particle size of wet magnetic powder is 2–10 μm, and the maximum particle size should not exceed 45 μm. Our company uses spray-can type black oil magnetic suspension and fluorescent magnetic powder ； 3.4.3 The color of the magnetic powder is selected to ensure a high contrast between the surface of the workpiece and the color of the magnetic powder. The common colors of non-fluorescent magnetic powder are black, white, and red; our company uses black for non-fluorescent magnetic powder ； 3.4.4 In special cases where non-fluorescent magnetic powder is used or when fluorescence magnetic powder is employed for inspection, it can be prepared on-site, but the following requirements must be met: a) For the preparation of wet non-fluorescent magnetic powder, kerosene is used as a dispersant, with an appropriate amount of transformer oil added as well. Typically, kerosene and transformer oil are used in equal amounts of 50% each. The concentration of its magnetic suspension is 10–20 g of magnetic powder per liter of suspension ； b). Preparation of wet fluorescent magnetic powder: It is prepared using kerosene as a dispersant, along with an appropriate amount of transformer oil. Typically, kerosene and transformer oil are used in equal amounts of 50% each. The concentration of its magnetic suspension is 1–3 g of fluorescent magnetic powder per liter of suspension ； c). The concentration of the prepared magnetic suspension must be tested as follows: 100 ml of the magnetic suspension is placed in a concentration measurement tube, and after 30 minutes of settling, if the volume of the precipitated non-fluorescent magnetic particles ranges from 1.2 to 2.4 ml, it is considered acceptable. After 30 minutes of precipitation with fluorescent magnetic powder, the volume of the magnetic powder precipitate was observed to be 0.1–0.5 ml. It should be noted that the magnetic suspension must be thoroughly stirred for at least 10 minutes before concentration measurement, to ensure that the magnetic particle particles are evenly dispersed throughout the suspension ； 4. 0 Magnetization methods: The yoke method and the coil magnetization method specified in these regulations both belong to the longitudinal magnetization method, and are mainly used to detect defects that are perpendicular to the axis of the workpiece or to the direction of the magnetic flux lines, or those at an angle greater than 45°, as shown in Figure 1 below. Figure 1 Longitudinal magnetization method: Types of magnetizing current and methods of applying current 5.1 Current source in yoke and coil magnetization methods – both are alternating current ； 5.2 Magnetic charging method: continuous magnetic charging method ； Continuous magnetization and power-on method: The power-on time is 1–3 seconds, during which magnetic powder is applied; once power supply is stopped, the application of magnetic powder also stops. The intervals between power-off periods should not exceed 1 second. To ensure an effective magnetization effect, magnetization must be repeated at least 2 times per inspection. It should be noted that current must be stopped at least 1 second after stopping the application of the magnetic suspension. 6.0 For each inspection area on the workpiece with a magnetization direction, at least 2 independent inspections shall be carried out, and the directions of the magnetic field lines in these 2 inspections should be roughly perpendicular to each other. If they cannot be perpendicular to each other for some reason, their intersection angle α must be ≥ 45°. When magnetization is performed using a rotating magnetic field, the inspection of the area under examination can be completed in one go without having to change the direction of the yoke. 7.0 Preparation of the surface of the workpiece to be inspected 7.1 The roughness of the surface of the workpiece to be inspected should be ≤25μm ； 7.2 The surface of the workpiece under inspection must be free of grease or any other substances that may attract magnetic powder ； 7.3 If there is a coating remaining on the surface of the workpiece to be inspected, and the thickness of that coating is less than 0.05 mm, it does not affect the inspection results; with the owner’s approval, magnetic particle testing can be carried out on the workpiece with the coating still in place ； 7.4 If the workpiece under inspection has blind holes or internal cavities, they should be sealed off ； 7.5 To improve the contrast between the workpiece surface and the magnetic particles, it is considered necessary to spray a thin layer of contrast enhancer evenly on the surface of the inspected area after cleaning. 8.0 Timing of Inspection 8.1 Magnetic particle testing of welds is generally carried out after welding, but for materials prone to delayed cracking, it should be performed 24 hours after welding ； 8.2 Magnetic particle testing of fasteners and forgings shall be carried out after the final heat treatment. 8.0 Magnetization specifications 9.1 Test pieces for measuring sensitivity: Standard test pieces are primarily used to evaluate the overall performance of magnetic particle inspection equipment, as well as magnetic particles and suspensions, in order to determine the effective magnetic field strength and direction on the surface of the workpiece under inspection. This procedure uses three types of test pieces, namely A1, C, and D, along with a magnetic field indicator. When using standard test pieces for magnetic particle inspection sensitivity verification, the magnetization specification value used should be sufficient to produce clear magnetic traces on the standard test pieces. The types, models, groove depths, and geometric dimensions of the A1, C, and D type test pieces are shown in Table 1 below: 9.1.1 Magnetic particle testing generally uses A1-30/100 type standard test pieces ； 9.1.2 Type C standard test pieces are mainly suitable for inspecting narrow areas such as weld grooves. When the A1-type standard test piece is inconvenient to use due to size constraints, the C-15/50-type standard test piece is generally an alternative option ； 9.1.3 When a more accurate determination of the magnetization state of the surface of the workpiece under inspection is required, or as specified by user requirements or technical standards, a D-type standard test piece can be used. 9.2 The magnetic field indicator (as shown in the figure below) is a rough verification tool used to indicate whether the surface of the workpiece under inspection, the direction of the magnetic field, the effective detection area, and the magnetization method are correct; it cannot be used as a quantitative indication of the magnetic field strength and its distribution. During continuous magnetization, the magnetic field indicator is placed on the surface being inspected, and the magnetic trace patterns on the indicator are observed to determine whether the aforementioned requirements are met. 9.3.1 When magnetizing a workpiece using a yoke, the magnitude of the magnetization current should be determined based on standard test pieces or lift force verification ；