ASTM A966-15(R2020) pdf free download

ASTM A966-15(R2020) pdf free download.Standard Practice for Magnetic Particle Examination of Steel Forgings Using Alternating Current
1. Scope
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 A275/ A275M 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 necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.6 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
5. Significance and Use
5.1 For ferromagnetic materials, magnetic particle examina- tion 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 in- cluded as mandatory requirements in some forging standards such as Specifications A508/A508M and A963/A963M. 5.2 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 proce- dure 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 con- ducting the magnetic particle examination. 5.3 The presence ofresidual magnetic fields in a component may be undesirable, and an advantage ofthe use ofan ac power source for magnetic particle examination is that an acceptable level of demagnetization can be readily achieved.
11. Methods of Magnetization
11.1 The forging may be magnetized either by passing current through the piece or by inducing a magnetic field by means of a central conductor, by coils, or by yoke. 11.1.1 Continuous Method—In the continuous method the inspection medium is applied to the surface under examination while the current is still flowing. The alternating current source generates high amperage current in pulses ofup to 1 s duration. The duration of this flow shall allow at least three pulses of current, or in the case where machines supply continuous current flow, a minimum shot of 1 ⁄ 5 to 1 ⁄ 2 s duration should be applied. 11.1.2 The surge and residual methods are not applicable to this practice. 11.2 At least two separate examinations shall be carried out on each area. The second examination shall be with the lines of magnetic flux approximately perpendicular to those used for the first examination in that area. A different means of magnetization may be used for the second examination. Mag- netizing in more than one direction cannot normally be accomplished simultaneously. An exception to the above rule is overall sequential multivector magnetization whereby several magnetizing circuits are provided for sequentially magnetizing a part in multiple directions depending on the locations of the current connectors. By this technique, indications of any orientation can be detected with a single application of magnetic particles.