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What Common Problems Can Be Detect By Portable Magnetic Flaw Detector
Jun 12, 2018

Portable magnetic flaw detector

1, the principle of magnetic particle inspection

Its basic principle is: When the workpiece is magnetized, if there is a defect on the surface of the workpiece, leakage magnetic flux will be generated due to the increased magnetic resistance at the defect, and a local magnetic field will be formed. The magnetic powder will show the shape and position of the defect here, thereby judging the defect. The presence. The

2, the basics of magnetic flaw detector

A, according to the workpiece magnetization direction, can be divided into circumferential magnetization method, longitudinal magnetization method, composite magnetization method and rotational magnetization method. The

B, according to the use of different magnetization current can be divided into: DC magnetization method, half-wave DC magnetization method, and AC magnetization method. The

C, according to the detection of magnetic powder used in the preparation of different, can be divided into dry powder method and wet powder method. The

3, the flaw of magnetic particle inspection

Magnetic particle inspection equipment is simple, easy to operate, rapid inspection, high detection sensitivity, can be used to find the surface or near surface defects of ferromagnetic materials nickel, cobalt and its alloys, carbon steel and certain alloy steel; it is suitable for Inspection of thin-walled parts or weld surface cracks can also reveal a certain depth and size of incomplete penetration defects; however, it is difficult to find pores, pinching flaws, and defects hidden deep in the weld.

4. defect magnetic mark type

A a variety of defects in the nature of the magnetic mark;

B material slag brought about by the pattern of magnetic marks;

C slag, pores bring a bit of magnetic marks. The

5., the cause of magnetic leakage

Since the ferromagnetic material's magnetic permeability is much larger than the non-ferromagnetic material's magnetic permeability, the magnetic flux density after the workpiece is magnetized is B = μH to analyze the unit area of the workpiece through the B magnet wire, and the unit in the defect area Area can not allow B magnetic lines to pass through, forcing a part of the magnetic force lines into the material below the defect, other magnetic lines have to be forced out of the surface of the workpiece to form a leakage magnetic flux, magnetic powder will be attracted by the magnetic leakage caused by this. The

6. The magnetic flux leakage factors

1), the permeability of the defect: the smaller the magnetic permeability of the defect, the stronger the magnetic leakage. The

2) magnetization magnetic field strength (magnetization force) size: the greater the magnetizing force, the stronger the magnetic flux leakage. The

3) The shape and size of the workpiece to be inspected, the shape and size of the defect, the depth of burial, etc.: When the other conditions are the same, the leakage of the magnetic pores buried in the same depth at the surface is less than that of the transverse crack