ASTM E1312-99(2004)e1

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e1
Designation:E1312–99 (Reapproved 2004)
Standard Practice for
Electromagnetic (Eddy-Current) Examination of
Ferromagnetic Cylindrical Bar Product Above the Curie
Temperature
This standard is issued under the fixed designation E 1312; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Editorial changes were made to provide consistent terminology, where applicable in May 2004.
1. Scope 2.2 Other Documents:
SNT-TC-1A Recommended Practice for Personnel Qualifi-
1.1 This practice covers procedures for eddy-current exami-
cation and Certification in Nondestructive Testing
nation of hot ferromagnetic bars above the Curie temperature
ANSI/ASNT-CP-189 Standard for Qualification and Certi-
where the product is essentially nonmagnetic, but below
fication of NDT Personnel
2100°F [1149°C].
2.3 AIA Standard:
1.2 This practice is intended for use on bar products having
1 NAS 410 Certification and Qualification of Nondestructive
diameters of ⁄2 in. [12.7 mm] to 8 in. [203 mm] at linear
Testing Personnel
throughput speeds up to 1200 ft/min [366 m/min]. Larger or
smaller diameters may be examined by agreement between the
3. Terminology
using parties.
3.1 Definitions—Terminology E 1316 shall apply to the
1.3 Thepurposeofthispracticeistoprovideaprocedurefor
terms used in this practice.
in-line eddy-current examination of bars during processing for
the detection of major or gross surface discontinuities.
4. Summary of Practice
1.3.1 The types of discontinuities capable of being detected
4.1 Principle—The major advantage of examining ferro-
are commonly referred to as: slivers, laps, seams, roll-ins
magnetic bar product above the Curie temperature with eddy
(scale, dross, and so forth), and mechanical damage such as
currents is the enhanced signal-to-noise ratio obtained without
scratches, scores, or indentations.
the need for magnetic saturation.
1.4 This practice does not establish acceptance criteria.
4.2 Sensors—This examination may be performed with
They must be specified by agreement between the using
various types or designs of encircling coils or with probe coils
parties.
that are fixed or rotating.
1.5 This practice does not purport to address all of the
4.2.1 One or more exciter or sensor coils is used to encircle
safety concerns, if any, associated with its use. It is the
the bar through which the product to be examined is passed.
responsibility of the user of this practice to establish appro-
When the hot bar is in close proximity to the sensing and
priate safety and health practices and determine the applica-
exciting coils, eddy currents are induced in the hot product by
bility of regulatory limitations prior to use.
an alternating current. The sensing coil detects the electromag-
netic flux related to these currents. Changes or disruptions in
2. Referenced Documents
2 the normal flux pattern indicate the presence of discontinuities.
2.1 ASTM Standards:
This technique is capable of examining the entire circumfer-
E 543 Practice for EvaluatingAgencies Performing Nonde-
ence without contacting the product.
structive Testing
4.2.2 The surface can also be examined with probe coils
E 1316 Terminology for Nondestructive Examinations
having one or more exciters and sensors which are spaced in
close proximity to the product surface. The probe is usually
1 small and does not encircle the product, making it necessary to
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
rotateeithertheprobesortheproducttoobtain100%coverage
structive Testing and is the direct responsibility of Subcommittee E7.07 on
Electromagnetic Method.
Current edition approved May 1, 2004. Published June 2004. Originally
approved in 1989. Last previous edition approved in 1999 as E 1312 - 99.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available fromTheAmerican Society for NondestructiveTesting (ASNT), P.O.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518.
Standards volume information, refer to the standard’s Document Summary page on Available from the Aerospace Industries Association of America, Inc., 1250
the ASTM website. Eye Street, N.W., Washington, DC 20005.
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E1312–99 (2004)
of the circumference. This is essentially a contact technique and evaluated as described in Practice E 543. The applicable
because the coil is fixtured in a device that rides on the edition of Practice E 543 shall be specified in the contractual
circumferencetomaintainafixeddistancebetweenthecoiland agreement.
product surface. 6.3 Acceptance Criteria—Since acceptance criteria are not
4.2.3 Discontinuities cause either a change in phase or specified in this practice, they shall be specified in the
signal amplitude when detected by the sensing coil. These contractual agreement.
signals are amplified and processed to activate marking or
7. Apparatus
recording devices, or both. Relative severity of the imperfec-
7.1 Electronic Apparatus, should be capable of energizing
tion can be indicated by the signal amplitude generated by the
the test coils or probes with alternating current at selectable
flux change or the degree of change in phase.
frequencies from 400 Hz to 100 kHz. Either manual or
4.2.4 Caution must be exercised in establishing reference
remotely operated switches can be used for frequency selec-
standards because flux changes caused by natural discontinui-
tion. The equipment should include a detector display (CRT,
ties might differ significantly from those generated by artificial
meters), phase discriminator, filters, modulators, recorders, and
discontinuities.
alarming/marking devices required for particular applications.
7.2 Sensors, whether probe or encircling coils, should op-
5. Significance and Use
erate through a frequency range from 400 Hz to 100 kHz.
5.1 The purpose of this practice is to describe a procedure
7.2.1 The sensor windings must be cooled (such as water
for in-line-eddy-current examination of hot cylindrical bars in
jackets) to control the sensor operating temperature and pre-
the range of diameters listed in 1.2 for large and repetitive
vent thermal damage to the sensors.
discontinuities that may form during processing.
7.2.2 Magneticorelectrostaticshieldsmightbenecessaryto
5.2 The discontinuities in bar product capable of being
suppress extraneous electrical transient noise. Electrostatic
detected by the electromagnetic method are listed in 1.3.1. The
shields usually float above ground at the sensor and are
method is capable of detecting surface and some subsurface
connected to a cable and then to the preamplifier shield.
discontinuities that are typically in the order of 0.030 in. [0.75
1 1
7.2.3 Constant spacing, ranging from ⁄16 in. [1.6 mm] to ⁄4
mm] and deeper, but some shallower discontinuities might also
in. [6.4 mm] between the sensors and product surface is
be found.
obtained with positioning mechanisms usually equipped with
5.3 Discontinuities that are narrow and deep, but short in
product guiding devices to prevent mechanical damage to the
length,arereadilydetectablebybothprobeandencirclingcoils
sensors.
because they cause abrupt flux changes. Surface and subsur-
7.3 Transport Mechanism—A conveyor or other type of
face discontinuities (if the electromagnetic frequency provides
mechanical device should be employed to pass the product
sufficient effective depth of penetration) can be detected by this
through or past the sensors. It should operate at production (or
method.
system) speeds with a minimum vibration of the sensors or
5.3.1 Discontinuities such as scratches or seams that are
product, and should maintain alignment of the sensors and
continuous and uniform for the full length of cut length bars or
product within the specified tolerances. Some systems may
extend for extensive linear distances in coiled product may not
require the transport to rotate either the bar, the sensors, or
always be detected when encircling co
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