T-710 Scope
When specified by the referencing code section, the magnetic particle examination techniques described in the article shall be used. In general, this article is in conformance with SE-709, Standard Guide for Magnetic Particle Examination. This document provides details to be considered in the procedures used.
When this article is specified by a referencing code section, the magnetic particle method described in this article shall be used together with article 1, General Requirements. Definition of terms used in this article are in mandatory appendix II.
T-720 General
The magnetic particle examination method is applied to detect cracks and other discontinuities on the surfaces of ferromagnetic materials.
The sensitivity is greatest for surface discontinuities and diminishes rapidly with increasing depth of discontinuities below the surface. Typical types or discontinuities than can be detected by this method are cracks, laps, seams, cold shuts and laminations.
In Principle, this method involves magnetizing an area to be examined and applying ferromagnetic particles (the examination´s medium) to the surface. Particle patterns form on the surface where the magnetic field is forced out of the part and over discontinuities to cause a leakage field that attracts the particles. Particle patterns are usually characteristic of the type of discontinuity that is detected.
Whichever technique is used to produce the magnetic flux in the part, maximum sensitivity will be to linear discontinuities oriented perpendicular to the lines of flux. For optimum effectiveness in detecting all types of discontinuities, each area is to be examinated at least twice, with the lines of flux during one examination being approximately perpendicular to the lines of flux the other.
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