【国外标准】 Standard Practice for Electromagnetic (Eddy Current) Examination of Copper and Aluminum Redraw Rod for Electrical Purposes

5.1 Eddy current instrumentation provides timely and useful information regarding the acceptability of copper and aluminum rod for quality control purposes, as well as providing for early warning that unacceptable rod is being produced. Eddy current testing is a nondestructive method of locating surface discontinuities in a product. Signals can be produced by discontinuities located on the surface of the rod. Since the density of eddy currents decreases nearly exponentially as the distance from the surface increases, deep-seated defects may be undetected.5.1.1 An exception is the detection of subsurface ferromagnetic inclusions with an additional, or shared, winding enveloped in a DC magnetic field and the addition of appropriate instrumentation. The coil winding, acting as a transducer, generates a voltage as the magnetized inclusion passes through, providing an electrical signal separate from the eddy current response to surface imperfections. The rod is transparent to the DC effect allowing high sensitivity to ferromagnetic inclusions, in the absence of eddy current noise. The method is inherently speed sensitive but is enhanced by high throughput speeds enabling the detection of small subsurface ferromagnetic inclusions which are particularly detrimental to rod quality.5.2 Some indications obtained by this practice may not be relevant to product quality. For example, a signal may be caused by minute flaws or irregularities, by anomalies in the material, or a combination thereof, that are not detrimental to the end use of the product. Nonrelevant indications, referred to as “noise,” can mask unacceptable discontinuities. On the other hand, relevant indications are those that may result from unacceptable discontinuities and should be determined by agreement between the user and the supplier. Any indication that is believed to be irrelevant shall be regarded as unacceptable until it is demonstrated by reexamination or other means to be nonrelevant.1.1 This practice covers the procedures that shall be followed in electromagnetic (eddy current) examination of copper and aluminum redraw rods for detecting discontinuities or imperfections of a severity likely to cause failure or markedly impair surface quality of the rod. These procedures are applicable for continuous lengths of redraw rod in diameters from 1/4 to 13/8 in. (6.4 to 35 mm) suitable for further fabrication into electrical conductors.1.2 This practice covers redraw rod made from tough-pitch or oxygen-free coppers. It can also be used for other types of copper, such as fire-refined high conductivity rod. It is also appropriate for aluminum and other nonferrous alloys used for electrical purposes.1.3 The procedures described in this practice are based on methods for making use of differential or absolute stationary encircling annular test coil systems.1.4 This practice does not establish acceptance criteria. Acceptance criteria must be established by the using parties.1.5 Units—The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.