ASTM A275/A275M-98
(Test Method)Standard Test Method for Magnetic Particle Examination of Steel Forgings
Standard Test Method for Magnetic Particle Examination of Steel Forgings
SCOPE
1.1 This test method provides a procedure for magnetic particle examination of steel forgings. The procedure will produce consistent results upon which acceptance standards can be based. This standard does not contain acceptance standards or recommended quality levels.
1.2 Only direct current or rectified alternating (full or half wave) current shall be used as the electric power source for any of the magnetizing methods. Alternating current is not permitted because its capability to detect subsurface discontinuities is very limited and therefore unsuitable. Note 1-Guide E709 may be utilized for magnetic particle examination in the field for machinery components originally manufactured from steel forgings.
1.3 The values stated in either inch-pound or SI units are to be regarded 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 must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.
1.4 This specification and the applicable material specifications are expressed in both inch-pound units and SI units. However, unless the order specifies the applicable "M" specification designation [SI units], the material shall be furnished to inch-pound units.
1.5 The minimum requirements for magnetic particle examination shall conform to practice standards of Practice E1444. If the requirements of this test method are in conflict with the requirements of Practice E1444, the requirements of this test method shall prevail.
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 and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
Designation: A 275/A 275M – 98
Standard Test Method for
Magnetic Particle Examination of Steel Forgings
This standard is issued under the fixed designationA275/A 275M; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 2. Referenced Documents
1.1 This test method provides a procedure for magnetic 2.1 ASTM Standards:
particle examination of steel forgings. The procedure will E 709 Guide for Magnetic Particle Examination
produce consistent results upon which acceptance standards E 1444 Practice for Magnetic Particle Examination
can be based. This standard does not contain acceptance 2.2 Other Document:
standards or recommended quality levels. Recommended Practice No. SNT-TC-1A, Supplement
1.2 Only direct current or rectified alternating (full or half B-Magnetic Particle Method
wave)currentshallbeusedastheelectricpowersourceforany
3. Terminology
of the magnetizing methods. Alternating current is not permit-
ted because its capability to detect subsurface discontinuities is 3.1 Definitions:
3.1.1 indication—the visual magnetic particle buildup re-
very limited and therefore unsuitable.
sulting from leakage fields in the magnetic field.
NOTE 1—Guide E 709E 709 may be utilized for magnetic particle
3.1.2 linear indication—an indication in which the length is
examination in the field for machinery components originally manufac-
at least three times the width. The minimum length of
tured from steel forgings.
indications to be considered linear shall be ⁄16 in. [1.6 mm].
1.3 The values stated in either inch-pound or SI units are to
3.1.3 magnetic flux—the product of the magnetic induction
be regarded as standard.Within the text, the SI units are shown
and the area of a surface (or cross section) when the magnetic
in brackets. The values stated in each system are not exact
induction is uniformly distributed and normal to the plane of
equivalents; therefore, each system must be used indepen-
the surface. The concept that the magnetic field is flowing
dently of the other. Combining values from the two systems
along the lines of force suggests that these lines are therefore
may result in nonconformance with the specification.
“flux” lines, and they are called magnetic flux.
1.4 This specification and the applicable material specifica-
3.1.4 magnetic particle method of examination— a method
tions are expressed in both inch-pound units and SI units.
for detecting discontinuities on or near the surface in suitably
However, unless the order specifies the applicable “M” speci-
magnetized materials, which employs finely divided magnetic
fication designation [SI units], the material shall be furnished
particles that tend to congregate in regions of leakage fields.
to inch-pound units.
3.1.5 nonrelevant indications—indications produced by
1.5 The minimum requirements for magnetic particle ex-
leakage fields. However, the conditions causing them are
amination shall conform to practice standards of Practice
present by design or accident, or other features of the part
E 1444E 1444. If the requirements of this test method are in
having no relation to the damaging flaws being sought. The
conflict with the requirements of Practice E 1444E 1444, the
term signifies that such an indication has no relation to the
requirements of this test method shall prevail.
discontinuities that might constitute defects.
1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Basis of Application
responsibility of the user of this standard to establish appro-
4.1 When in accordance with the requirements of the
priate safety and health practices and determine the applica-
inquiry, contract, order, or specifications, forgings are fur-
bility of regulatory limitations prior to use.
nished subject to magnetic particle examination, the manufac-
turer and the purchaser shall be in agreement concerning the
This test method is under the jurisdiction of ASTM Committee A-1 on Steel,
following:
Stainless Steel and RelatedAlloys, and is the direct responsibility of Subcommittee
A01.06 on Steel Forgings and Billets.
Current edition approved Sept. 10, 1998. Published December 1998. Originally
published as A 275 – 44 T. Last previous edition A 275 – 96. Annual Book of ASTM Standards, Vol 03.03.
2 4
For ASME Boiler and Pressure Vessel Code applications see related Method Available from American Society for Nondestructive Testing, 4153 Arlingate
SA-275/SA-275M in Section II of that Code. Plaza, Caller #28515, Columbus, OH 43228-0518.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
A 275/A 275M – 98
4.1.1 The locations on the forgings that are to be subjected 9.3 Rough surfaces hamper the mobility of magnetic pow-
to magnetic particle examination. ders due to mechanical trapping which in turn produces false
4.1.2 The type, size, number, location, and orientation of indications. Such areas should be surface ground. If grinding is
indications that are to be considered injurious. impractical,apapertapeoverlay(asdescribedin14.1.1.2)may
4.1.3 The method of application of magnetic particles, eliminate the problem.
demagnetization requirements and magnetic field strengths.
4.2 In cases where large undercuts in the forgings are to be
10. Methods of Magnetization
taken by the purchaser, the manufacturer shall be given the
10.1 The forging may be magnetized either by passing
privilege (when the design permits) of machining slots or
current through the piece or by inducing a magnetic field by
grooves in the rough-machined forging to explore the internal
means of a central conductor or by coils.
conditions prior to shipping.
10.1.1 Continuous Method—In the continuous method, the
4.3 Acceptance standards.
inspection medium is applied to the surface under inspection
while the current is still flowing. The current source generates
5. Personnel Requirements
high amperage current in pulses of up to 1-s duration. The
5.1 Personnel performing the magnetic particle examination
duration of this flow shall allow at least three pulses of current
tothistestmethodshallbequalifiedandcertifiedinaccordance
or in the case where machines supply continuous current flow
with a written procedure conforming to Recommended Prac-
1 1
a minimum shot of ⁄5 to ⁄2-s duration should be applied.
tice No. SNT-TC-1A or another national standard that is
10.1.2 Surge Method—In the surge method a high-
acceptable to both the purchaser and the supplier.
magnetizing force is applied and then reduced to a lower
continuous value, which is maintained during application of
6. Stage of Inspection
the inspection medium.
6.1 Unless otherwise specified by the purchaser, acceptance
10.1.3 Residual Method—Intheresidualmethodtheinspec-
inspection shall be performed on a forging in the final
tion medium is applied to the surface under inspection after the
machined surface condition and final thermally treated condi-
magnetizing current has ceased to flow. The effectiveness of
tion (including stress relief) or within 0.030 in. [0.8 mm] of the
thismethoddependsuponthestrengthofthemagnetizingforce
final machined surface.
and the retentivity of the piece, which in turn depends upon
such factors as chemical composition, heat treatment, etc. The
7. Magnetizing Apparatus
residual method is not acceptable for forgings being inspected
7.1 Rectified alternating (full or half wave) or direct-current
to comply with some regulatory bodies; it shall be used,
electric power sources may be used. When current is passed
therefore, only when approved by the purchaser.
through the part itself, the equipment shall consist of contact-
10.2 At least two separate examinations shall be carried out
ing or clamping elements with sufficient surface area and
on each area.The second examination shall be with the lines of
clamping pressure to allow the required current to flow without
magnetic flux approximately perpendicular to those used for
damaging (burning) the part being examined.
the first examination in that area. A different means of
7.2 Portable electromagnetic (ac-dc) yokes may be used in
magnetizing may be used for the second examination. Magne-
the dc mode as a magnetizing apparatus, provided the sensi-
tizing in more than one direction cannot be accomplished
tivity to detect crack-like defects is demonstrated to be at least
simultaneously.
equivalent to that of the direct-magnetization method.
NOTE 2—An exception to the above rule is overall sequential multi-
8. Magnetic Particles
vector magnetization whereby several magnetizing circuits are provided
for sequentially magnetizing a part in multiple directions depending upon
8.1 The inspection medium shall consist of finely divided
the locations of the current connectors. By this technique, flaws of any
ferromagnetic particles, which may be suspended in a suitable
orientation can be detected with a single application of magnetic particles.
liquid medium, or used in dry powder form.
10.3 The two general types of magnetization with regard to
8.2 The size and shape of the particles, and their magnetic
direction are longitudinal and circular, as follows:
properties, both individually and collectively, are important
(see Section 11). 10.3.1 Longitudinal—When a forging is magnetized longi-
tudinally, the magnetic flux lines are usually parallel to the axis
9. Surface Preparation
of the piece. A longitudinally magnetized piece always has
9.1 Thesensitivityofthemagneticparticleexaminationwill definite poles readily detectable by compass or magnetometer.
Longitudinalmagnetizationisusuallyaccomplishedbyplacing
depend to a considerable extent upon the condition of the
surface being tested. Defects may be satisfactorily revealed on the forging within a solenoid, often formed by wrapping cable
around the piece (Fig. 1). For special applications, magnetic
shot-blasted or otherwise cleaned forged surfaces, or on
surfaces having small amounts of heat-treating scale without yokes can be used (Fig. 2) when requirements of 7.2 are met.
any special surface preparation; however, loose scale must be 10.3.2 Circular—Circular magnetization is obtained by
removed. To reveal fine defects, the surfaces to be inspected passing a current directly through the piece (Fig. 3), or induced
should be smooth machined to at least a 250-µin. [6.35-µm] through a conductor (Fig. 4), or conductors threaded (Fig. 5)
finish. through an opening in the piece. Localized circular magenti-
9.2 The surfaces shall be free of grease, oils, or other zation may be obtained by passing current through the local
substances to which the particles may adhere. areas by use of prod-type contacts (Fig. 6).
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
A 275/A 275M – 98
FIG. 5 Circular Magnetization, Current Through Conductors
Threaded Through Forging
FIG. 1 Longitudinal Magnetization
FIG. 6 Circular Magnetization with “Prod” Type Contact
Electrodes
ones just below the point at which excessive adherence of the
particles begins to occur over the surface being inspected.
10.5.1 Coil Magnetization—When coil magnetization is
used, the magnetic field strength is directly proportional to the
FIG. 2 Longitudinal Magnetization, with Yoke
current (ampere-turns if a coil or solenoid is used) and
inversely proportional to the thickness of the section being
inspected.
10.5.1.1 Longitudinal Magnetization—For encircling coils
(Fig. 1), the turns of the coil shall be kept closely together.The
field strength decreases as distance from the coil increases and
long parts must be magnetized in sections. If the area to be
inspected extends beyond 6 in. [150 mm] on either side of the
coils,theadequacyofthefieldshallbedemonstratedbytheuse
of field indicators (see 10.5.6).
(1) Small Forgings—Magnetizing force shall be 35 000
FIG. 3 Circular Magnetization, Current Directly Through Forging ampere-turns divided by the sum of 2 plus the “length over
diameter” ratio of the test part. For example, a part 10 in. [250
mm]longby2in.[50mm]inoutsidediameterhasan L/Dratio
of 5. Therefore, 35 000/(2+5) = 5000 ampere-turns; if a 5-turn
coil is used, the current required is 5000/5 or 1000 A. This
formula provides an adequate field strength on small parts
having an L/D ratio of 4 or greater. For parts having a smaller
L/D ratio, adequate field strengths shall be demonstrated by the
use of a field indicator (see 10.5.6).The graph in Fig. 7 may be
used to determine the ampere-turns required for each L/D
relationship.
FIG. 4 Circular Magnetization, Current Through a Conductor
(2) Large Forgings—For large forgings the magnetizing
force shall be in the range from 1200 to 4500 ampere-turns.A
10.4 The magnetic field is confined almost entirely to the field indicator (see 10.5.6) shall be used to demonstrate the
piece and there may be no external manifestation of the presence of an adequate field strength over the area to be
magnetized condition. Indications will appear strongest in the inspected.
direction perpendicular to the direction of the magnetic field. 10.5.1.2 Circular Magnetization (Fig. 5)—For circular
10.5 Field Strength—The minimum field strength that will magnetization with through coils, use the current with amper-
reveal and permit classification of all objectionable defects age as specified in 10.5.2 divided by the number of turns in the
shall be used. The maximum field strengths practical are the coil.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
A 275/A 275M – 98
10.5.3.3 A remote control switch, which may be built into
the prod handles, shall be provided to permit the current to be
turned on after the prods have been properly positioned and to
turn if off before the prods are removed in order to prevent
arcing.
10.5.3.4 Examination Coverage—Examinations shall be
conducted with sufficient overlap to assure 100 % coverage at
the established sensitivity.
10.5.3.5 Direction of Magnetization—At least two separate
exam
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.