ABSTRACT
In NDT, demagnetization reduces the flux density level in an object to a level at which its external fields do not cause problems in subsequent use. It is required (i) if the part is to become a moving component of an assembly and might pick up particles that would cause wear, (ii) if the MFL field might interfere with cleaning of the part or affect nearby instruments, (iii) if the part is to be magnetized to a lower level in another direction, and (iv) the MFL field would interfere with processes such as welding or machining. 58 Demagnetization to a specific external field strength level is often specified by procedural codes, and can easily be measured outside the part with a gaussmeter, or by using an encircling coil. Typically no more than 8 A/cm (10 Oe) might be specified. In this chapter, commonly used forms of de- and remagnetization are outlined.
