Analysis on the working principle and precautions of magnetic particle detector
Today I'm going to tell you about a new type of testing equipment, which is magnetic particle detector. Have you heard of it? How much do you know about it? Next, I will tell you the working principle and precautions of the magnetic particle detector.
Magnetic particle flaw detector must use magnetizing current to excite magnetized parts. After magnetization, this part can make magnetic field current as magnetizing current. Magnetizing current includes alternating current, direct current, rectifier and impulse current, which is the most commonly used alternating current in China at present. It is suitable for the detection of cracks and minor defects on the surface and near surface of crankshaft, camshaft, spline shaft and other small and medium-sized parts due to casting, quenching, processing, fatigue and other reasons by wet magnetic particle method. It is the preferred model for single piece inspection, small batch sampling inspection and large batch inspection.
It is based on the basic theory of leakage magnetic field. When the tested part is magnetized in the external magnetic field, an induction magnetic field is established in the part. When there is a defect on the external surface or near the surface of the part, and the direction is at a certain angle with the direction of the induction magnetic field, the magnetic field line of the induction magnetic field will not continuously leak out, forming a leakage magnetic field on the surface of the part, and forming magnetic poles on both sides of the defect. The magnetic particle is scattered on the outer surface of the part, and the magnetic pole on the work piece is formed to absorb the magnetic particle due to the discontinuity. The accumulation of the magnetic particle is obvious magnetic mark which can be observed directly by the naked eye. The appearance of the magnetic mark shows a series of images such as the length, direction and outline of the defect, so as to show the defect location of the part.
Precautions for magnetic particle detector;
1. Connect the horseshoe yoke probe with the connecting wire, then turn on the machine, press the up and down direction keys to make the yellow triangle mark on; press the confirmation key on the detection items to enter the detection. Start the flaw detection; after that, adjust the magnetic opening distance of the flaw detector properly according to the size of the flaw detection workpiece.
2. When performing flaw detection on the flaw detection surface of the workpiece, there shall be overlapping, and the overlapping area shall not be less than 25 mm each time, so as to achieve multi-directional flaw detection. When it is found that there is aggregation of magnetic particles, it is necessary to analyze the causes of the formation of magnetic traces in time, and correctly judge the related and non related magnetic traces. It is necessary to correctly judge the characteristics of various magnetic traces.
3. After taking the picture of magnetic trace display, press the up and down direction keys to stop the cursor on the function item, and press the confirm key to display the storage dialog box on the screen (or directly press the storage; key)
4. During dry powder flaw detection, the surface of workpiece shall be dry. Apply proper dry magnetic powder evenly to the flaw detection range of the workpiece, slowly move the yoke probe on the detection surface of the workpiece at a speed of less than 40mm / s, and conduct multi-directional vertical flaw detection, so that the two magnets and the detected workpiece are in good contact. Observe whether there is magnetic particle aggregation when the magnetic particle flows. If there is any abnormal change, change the opening of the yoke, adjust the magnetic field strength, and repeat the flaw detection.
Well, the working principle and precautions of the magnetic particle detector are introduced here for you. I hope you can understand them.