Magnetic portable magnetic particle inspection machine common magnetization mode list

In the process of operation, the magnetization of the workpiece is still a more important part. Magnetization refers to the process of generating a magnetic field inside the workpiece under the action of an external magnetic field called the magnetization of the workpiece. There are many magnetization methods in the detection of magnetic particle flaw detection machine, and we can be divided into different categories according to different standards.

1, according to the use of current direct magnetization method and indirect magnetization method.

2, can be divided into circumferential magnetization method, longitudinal magnetization method, composite magnetization method, in these methods, the detection orientation of circumferential magnetization and the workpiece axial parallel defect direct conduction method, used for magnetic particle flaw detection machine on the rod or rod workpiece magnetization work.

3, according to the type of current used can be divided into direct current magnetization method, alternating current magnetization method.

Magnetization during the operation of the flaw detection machine:

1. Circumferential magnetization

Refers to the direct electricity to the workpiece, or the current through the central hole of the workpiece conductor, designed to establish a closed magnetic field in the workpiece around the workpiece and perpendicular to the axis of the workpiece, the magnetic field line has a closed shape. Circumferential magnetization is mainly used to find defects parallel to the workpiece, that is, defects parallel to the direction of the current.

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2. Longitudinal magnetization

Refers to the method of magnetizing the workpiece in a long direction by passing an electric current through the coil surrounding the workpiece, and the line of magnetic force in the workpiece is parallel to the axis line of the coil. It is mainly used to find defects attached vertically to the workpiece shaft. Magnetizing with an electromagnetic yoke so that the line of magnetic force is parallel to the longitudinal axis of the workpiece also belongs to this category.

3. Multi-directional magnetization

A magnetic field whose size and direction change with time in a circular, elliptical or helical shape is generated in the workpiece by composite magnetization. Because the direction of the magnetic field constantly changes on the workpiece, it is possible to check for defects in different directions.

The influence of kinematic viscosity of magnetic powder used in portable magnetic particle flaw detection machine on flaw detection

Source: | Release Date: 2021-04-15

The main factors that influence the magnetic particle size, magnetic particle, kinematic viscosity and color of magnetic particle and magnetic suspension are the magnetic particle size, magnetic particle magnetism, magnetic particle and magnetic suspension.

Kinematic viscosity of magnetic powder refers to the viscosity of carrier fluid in magnetic suspension. If the kinematic viscosity of magnetic suspension is too high. When the normal magnetization time is 3 ~ 5s, the defect of the leakage magnetic field is difficult to adsorb magnetic powder, resulting in missed detection. The fluidity of the dry magnetic powder is significantly different from the kinematic viscosity of the wet magnetic suspension. When magnetized by direct current, the current flows under the near surface of the part. Magnetic particles fall on the surface and do not produce fluidity. When there is a defect near the surface, the leakage magnetic field jumps to the surface to adsorb magnetic powder and observe the magnetic trace. When the AC magnetized parts, due to the skin effect, the leakage magnetic field forms N pole S pole and adsorbs magnetic powder.

The influence of the color of magnetic powder on the detection of defects compared with the workpiece background. Generally, the magnetic powder prepared by wet magnetic suspension is usually black or brown, while the dry method has different colors such as black, white, and blue. When inspecting parts, wet or dry magnetic particle should be selected according to the surface color state of the parts. Then select the variety specifications of magnetic powder. At present, most of the fluorescent water-based magnetic suspension and fluorescent water-based concentrate are used in wet parts detection, which can be used by adding clean tap water and dispersing the concentrate in proportion. In the case of dry inspection, when the background contrast of the part is fuzzy, the contrast enhancer can be used to spray a thin layer of white paint on the background to enhance the observation of the defect magnetic mark.

Discrimination of magnetic powder used in flaw detection machine:

The magnetic powder used for inspection is the oxide of iron, which becomes fine particles after grinding and screening, with a particle size of 150 ~ 200 mesh (0.1 ~ 0.07mm). When the workpiece is magnetized, if there is a defect on the surface of the workpiece, magnetic leakage is generated due to the increase of the magnetic resistance at the defect, forming a local magnetic field, and the magnetic powder shows the shape and position of the defect here, so as to determine the existence of the defect. The magnetic particle flaw detector can be divided into DC magnetization method, half-wave DC magnetization method, and AC magnetization method according to the different magnetization current. It can be divided into black magnetic powder, red magnetic powder, white magnetic powder and magnetic powder.

The black one is Fe3O4 magnetic powder. Black magnetic marks are usually formed on the surface of the workpiece, which is the most widely used magnetic powder in the flaw detection machine.

Red magnetic powder is a highly permeable iron red Fe2O3 powder. In the condition of black metal and the surface color of the workpiece is brown, the red magnetic powder has a higher contrast when tested.

White magnetic powder is made from aluminum or magnesium Fe3O4 by synthesizing a silver white or white powder on a black surface of magnetic powder. The white black magnetic powder is suitable for the magnetic detection surface of the workpiece, with high contrast and good display effect.

Magnetic powder is a colloidal mixture composed of material, magnetic powder and gelatin in a certain proportion, made by mechanical method... This magnetic powder can generate brightness in the dark room with wood external irradiation, so it is suitable for surface inspection of various workpieces, especially for workpieces with dark surface and high sensitivity.

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