ASTM A966/A966M-08

For ferromagnetic materials, magnetic particle examination is widely specified for the detection of surface and near-surface flaws such as cracks, laps, seams, and linearly oriented nonmetallic inclusions. Such examinations are included as mandatory requirements in some forging standards such as Specifications A 508/A 508M and A 963/A 963M.

Use of alternating current as the power source for magnetic particle examination imposes a significant restriction on the detection of subsurface indications, so that the procedure is essentially limited to the finding of flaws that are open to the surface. Attention therefore is drawn to the need to have the component in the finish-machined condition before conducting the magnetic particle examination.

The presence of residual magnetic fields in a component may be undesirable, and an advantage of the use of an AC power source for magnetic particle examination is that an acceptable level of demagnetization can be readily achieved.

1.1 This practice covers a procedure for the magnetic particle examination of steel forgings using alternating current as the power source. The procedure will produce consistent results upon which acceptance standards can be based. This practice does not contain acceptance limits or recommended quality levels.

1.2 Only alternating 50–60 cycle current shall be used as the electric power source for any of the magnetizing methods.

1.3 When subsurface indications are sought in forgings, then dc magnetization in accordance with Practice A 275/A 275M should be used.

1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the specification. Unless the order specifies the applicable “M” specification designation [SI units], the inch-pound units shall be used.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.