Lab 4 : Magnaflux Test

1. There are several methods of magnetic particle testing (ASTME 709 or IS10543 and IS 12147). All these methods are used to detect various kinds of flaws in ferromagnetic components such as welding, casting and forgings of iron and steel.

2. The component to be inspected for flaws is magnetized and the inspection medium is applied to the component, or magnetization of the component application of inspection medium can be done simultaneously.

3. In the dry method of inspection, a special fine ferromagnetic powder is applied on the surface by means of a hand shaker, vibrating screen or by any other suitable method so that the powder uniformly distributes on the surface of the component (IS 10543).

4. In the wet method of inspection, a liquid containing fine ferromagnetic particle suspended in some carrier such as kerosene or petroleum oil is applied by some suitable method such as dipping, spraying or brushing (IS12147)

5. Magnetization of the component is done either by using an external magnetic yoke coil or by passing an electric through it. A magnetic pole is formed at the crack or flaws, which cause the magnetic powder to concentrate on this area and the flow gets easily detected.

6. When the part is magnetized lengthwise transverse cracks are easily detected. This is done by energizing a coil around the bar.(Fig.a)

7. When part is magnetized crosswise by a circular magnetic field, lengthwise cracks are easily detected. This is done by passing an electric current, either alternating or direct,through the component. The use or alternating currents limits the test for detection of only those flaws which are open at the surface. This is due to the fact that alternating currents try to flow from near the surface i.e. skin effect. However direct current magnetization makes it possible to detect surface as well as sub surface discontinuities.(Fig.b)