Magnetic Particle Inspection
Our customers can avail from us Magnetic Particle Inspection services. It is a non destructive method which is used for the detection of sub surface and surface defects. In this process externally applied magnetic field is used which removes the material flux from the area of the defect.
If there is any defected material, the magnetic field is get distorted which cause leakage of the magnetic fields at the flaw. In the surface magnetic field is goes to a considerable distance and in air the megnatism is very strong. Therefore the size of the distortion is larger than that of the defect and is made visible at the surface of the part by means of the small particles that are pulled to the leakage fields.The particle inspection method use perfectly divided iron or magnetic iron oxide particles held in suspension in a suitable liquid. this fluid is known as carrier and its particles are colored or coated with fluorescent dyes that are visible with a hand-held ultraviolet light. in order to know the area where magnetic field pop out from the surface, the suspension is painted over the magnetized specimen at the time of magnetization with a direct current or with an electromagnet. By doing this, the magnetic particles are attracted to the surface field and hold on the edges of the fault to show it as a build up of particles.
This type of inspection can be applied to the raw material in a steel mill, in the starting stage of manufacturing, or mostly to the machines parts. It is also used for checking the structural parts that have been in service for some time to find the failing cracks.
Common test methods used include
BS6072:1981 (1986 - AMD 4843) - Magnetic Flow - Colour Contrast Method, and ASTM E709.
According to the Left hand rule, there are two methods of magnetizing a part, longitudinal and circular magnetization. In Longitudinal Magnetization the current is passes through a coil and the magnetic flux lines go through the part. In Circular magnetization passes current through the part and establishes a magnetic field around the part. There are two different method used as cracks can only be seen at 45 to 90 degrees to the magnetic flux lines. Our offered services can not be used for non-magnetic ferrous materials and non-ferrous materials like austenitic stainless steels.