ASTM A341/A341M-16(2022)
(Test Method)Standard Test Method for Direct Current Magnetic Properties of Soft Magnetic Materials Using D-C Permeameters and the Point by Point (Ballistic) Test Methods
Standard Test Method for Direct Current Magnetic Properties of Soft Magnetic Materials Using D-C Permeameters and the Point by Point (Ballistic) Test Methods
SIGNIFICANCE AND USE
3.1 Permeameters require the use of yokes to complete the magnetic circuit and are therefore inherently less accurate than ring test methods. Refer to Test Method A596/A596M for further details on ring test methods. However, when testing certain shapes as bars or when magnetic field strength in excess of 200 Oe [16 kA/m] is required, permeameters are the only practical means of measuring magnetic properties.
3.2 This test method is suitable for specification acceptance, service evaluation, research and development and design.
3.3 When the test specimen is fabricated from a larger sample and is in the same condition as the larger sample, it may not exhibit magnetic properties representative of the original sample. In such instances the test results, when viewed in context of past performance history, will be useful for judging the suitability of the material for the intended application.
SCOPE
1.1 This test method provides dc permeameter tests for the basic magnetic properties of soft magnetic materials in the form of bars, rods, wire, or strip specimens which may be cut, machined, or ground from cast, compacted, sintered, forged, extruded, rolled, or other fabricated materials. It includes tests for determination of the normal induction under symmetrically cyclically magnetized (SCM) conditions and the hysteresis loop (B-H loop) taken under conditions of rapidly changing or steep wavefront reversals of the direct current magnetic field strength. This method has been historically referred to as the ballistic test method. For testing hard or permanent magnet materials, Test Method A977/A977M shall be used.
1.2 This test method shall be used in conjunction with Practice A34/A34M.
1.3 This test method covers a range of magnetic field strength in the specimen from about 0.05 Oe [4 A/m] up to above 5000 Oe [400 kA/m] through the use of several permeameters. The separate permeameters cover this test region in several overlapping ranges.
1.4 Normal induction and hysteresis properties may be determined over the magnetic flux density range from essentially zero to the saturation induction for most materials.
1.5 Recommendations of the useful magnetic field strength range for each of the permeameters are shown in Table 1.2 Permeameters particularly well suited for general testing of soft magnetic materials are shown in boldface. Also, see Sections 3 and 4 for general limitations relative to the use of permeameters.
1.6 The symbols and abbreviated definitions used in this test method appear with Fig. 1 and in appropriate sections of this document. For the official definitions, see Terminology A340. Note that the term magnetic flux density used in this document is synonymous with the term magnetic induction.
FIG. 1 Basic Circuit Using Permeameter
Note 1:
A1—Multirange ammeter (main current)
A2—Multirange ammeter (hysteresis current)
B—Magnetic flux density test position for Switch S3
F—Electronic Fluxmeter
H—Magnetic field strength test position for Switch S3
N1—Magnetizing coil
N2—Magnetic flux sensing (B) coil
N3—Magnetic field strength (H) sensing coil
R1—Main current control rheostat
R2—Hysteresis current control rheostat
S1—Reversing switch for magnetizing current
S2—Shunting switch for hysteresis current control rheostat
S3—Fluxmeter selector switch
SP—Specimen
1.7 Warning—Mercury has been designated by EPA and many state agencies as a hazardous material that can cause central nervous system, kidney, and liver damage. Mercury, or its vapor, may be hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury-containing products. See the applicable product Material Safety Data Sheet (MSDS) for details and EPA’s website (http://www.epa.gov/mercury/faq.htm ) for additional information. Users should be aware that selling mercury or mercury-containing products, or both, in your state may be p...
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Standards Content (Sample)
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.
Designation: A341/A341M − 16 (Reapproved 2022)
Standard Test Method for
Direct Current Magnetic Properties of Soft Magnetic
Materials Using D-C Permeameters and the Point by Point
(Ballistic) Test Methods
This standard is issued under the fixed designationA341/A341M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision.Anumber 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 U.S. Department of Defense.
1. Scope 1.6 Thesymbolsandabbreviateddefinitionsusedinthistest
method appear with Fig. 1 and in appropriate sections of this
1.1 This test method provides dc permeameter tests for the
document. For the official definitions, see Terminology A340.
basic magnetic properties of soft magnetic materials in the
Notethatthetermmagneticfluxdensityusedinthisdocument
form of bars, rods, wire, or strip specimens which may be cut,
is synonymous with the term magnetic induction.
machined, or ground from cast, compacted, sintered, forged,
extruded, rolled, or other fabricated materials. It includes tests
1.7 Warning—Mercury has been designated by EPA and
fordeterminationofthenormalinductionundersymmetrically
many state agencies as a hazardous material that can cause
cyclically magnetized (SCM) conditions and the hysteresis
central nervous system, kidney, and liver damage. Mercury, or
loop (B-H loop) taken under conditions of rapidly changing or
its vapor, may be hazardous to health and corrosive to
steep wavefront reversals of the direct current magnetic field
materials.Cautionshouldbetakenwhenhandlingmercuryand
strength. This method has been historically referred to as the
mercury-containing products. See the applicable product Ma-
ballistic test method. For testing hard or permanent magnet
terial Safety Data Sheet (MSDS) for details and EPA’s website
materials, Test Method A977/A977M shall be used.
(http://www.epa.gov/mercury/faq.htm)foradditionalinforma-
1.2 This test method shall be used in conjunction with
tion. Users should be aware that selling mercury or mercury-
Practice A34/A34M.
containingproducts,orboth,inyourstatemaybeprohibitedby
state law.
1.3 This test method covers a range of magnetic field
strength in the specimen from about 0.05 Oe [4 A/m] up to
1.8 The values and equations stated in customary (cgs-emu
above 5000 Oe [400 kA/m] through the use of several
and inch-pound) or SI units are to be regarded separately as
permeameters. The separate permeameters cover this test
standard. Within this standard, SI units are shown in brackets
region in several overlapping ranges.
except for the sections concerning calculations where there are
1.4 Normal induction and hysteresis properties may be
separate sections for the respective unit systems. The values
determined over the magnetic flux density range from essen-
stated in each system may not be exact equivalents; therefore,
tially zero to the saturation induction for most materials.
each system shall be used independently of the other. Combin-
ingvaluesfromthetwosystemsmayresultinnonconformance
1.5 Recommendations of the useful magnetic field strength
with this standard.
range for each of the permeameters are shown in Table 1.
Permeameters particularly well suited for general testing of
1.9 This standard does not purport to address all of the
soft magnetic materials are shown in boldface. Also, see
safety concerns, if any, associated with its use. It is the
Sections 3 and 4 for general limitations relative to the use of
responsibility of the user of this standard to establish appro-
permeameters.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
This test method is under the jurisdiction of ASTM Committee A06 on
1.10 This international standard was developed in accor-
MagneticPropertiesandisthedirectresponsibilityofSubcommitteeA06.01onTest
dance with internationally recognized principles on standard-
Methods.
Current edition approved Oct. 1, 2022. Published October 2022. Originally
ization established in the Decision on Principles for the
approved in 1969. Last previous edition approved in 2016 as A341/A341M–16.
Development of International Standards, Guides and Recom-
DOI: 10.1520/A0341_A0341M-16R22.
2 mendations issued by the World Trade Organization Technical
The boldface numbers in parentheses refer to a list of references at the end of
this standard. Barriers to Trade (TBT) Committee.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A341/A341M − 16 (2022)
TABLE 1 Permeameters
A
Magnetizing Coil
Useful Magnetic Field Strength Range
H Measuring Reluctance
D
Permeameter Surrounds References
B
Device Compensation
Oe kA/m Specimen
Babbit 40/1000 3.2/80 I, HC yes yes (1,2)
Burroughs 0.1/300 0.008/24 I yes yes (1,3,4,5)
C
Fahy Simplex 0.1/300 0.008/24 HC no no (1,4,5,6,7)
Fahy Simplex
100/2500 8/200 HC no no (1,3)
C
Super H adapter
Full range 0.05/1400 0.004/112 HC yes yes (1,8)
High H 100/5000 8/400 FC yes no (1,5,7,9)
Iliovici 0.5/500 0.04/400 I, HC yes yes (4,10,11)
IEC Type A 0.1/2500 0.008/200 HC, HP no yes IEC 60404-4
IEC Type B 0.1/630 0.008/50 RCC no no IEC 60404-4
Isthmus 100/20 000+ 8/1600+ HC, HP no no (1,4,12,13)
MH 0.1/300 0.008/24 FC yes yes (1,6,14)
NPL 0.5/2500 0.04/200 I, HC yes yes (15)
Saturation 100/4000 8/320 HC no yes (5,16,17)
A
Although the permeameters are capable of being used at the lower end of the measurement range, the measurement accuracy is reduced.
B
I—magnetizing current; HC—fixed H coil; FC—flip coil; HP—Hall probe; RCC —Rogowski-Chattock coil.
C
Fahy permeameters require a standard of known magnetic properties for calibration of the H coil.
D
The boldface numbers in parentheses refer to a list of references at the end of this standard.
NOTE 1—
A —Multirange ammeter (main current)
A —Multirange ammeter (hysteresis current)
B—Magnetic flux density test position for Switch S
F—Electronic Fluxmeter
H—Magnetic field strength test position for Switch S
N —Magnetizing coil
N —Magnetic flux sensing (B) coil
N —Magnetic field strength (H) sensing coil
R —Main current control rheostat
R —Hysteresis current control rheostat
S —Reversing switch for magnetizing current
S —Shunting switch for hysteresis current control rheostat
S —Fluxmeter selector switch
SP—Specimen
FIG. 1 Basic Circuit Using Permeameter
A341/A341M − 16 (2022)
2. Referenced Documents clamping strains into the test specimen. For the above reasons
3 test results obtained on a test specimen with one type per-
2.1 ASTM Standards:
meameter may not agree closely with those obtained on the
A34/A34MPractice for Sampling and Procurement Testing
same test specimen using another type of permeameter.
of Magnetic Materials
A340Terminology of Symbols and Definitions Relating to
5. Apparatus
Magnetic Testing
A596/A596MTest Method for Direct-Current Magnetic
5.1 Because of the differences in physical construction of
PropertiesofMaterialsUsingthePointbyPoint(Ballistic) the various permeameters listed in Table 1, no standard list of
Method and Ring Specimens
components is given. When used with a particular type of
A977/A977MTestMethodforMagneticPropertiesofHigh- permeameter, the components should conform to the general
Coercivity Permanent Magnet Materials Using Hyster-
requirementslistedbelow.Abasicschematicofapermeameter
esigraphs is shown in Fig. 1.
2.2 IEC Standard:
5.2 Permeameter—The particular permeameter used shall
Publication 60404-4,Ed. 2.2 Magnetic Materials – Part 4:
be of high quality construction. The yokes should be made of
Methods of Measurement of D.C. Magnetic Properties of
high permeability alloy such as oriented or nonoriented silicon
IronandSteel,IEC,1995PlusAmendments1in2000and
iron or nickel-iron alloy, although low carbon steel or iron is
2 in 2008
acceptable in certain instances.The preferred yoke dimensions
2.3 Other Documents:
are listed in the appended references (see Table 1). Deviations
NISTCircular No. 74, pg. 269
from these dimensions should be such that the yoke is
NISTScientific Paper 117, SPBTA
operating at or below the point of maximum permeability for
the highest test magnetic flux densities encountered. Yoke
3. Significance and Use
construction may consist of either stacked laminations or
stripwound C cores suitably bolted or adhesive bonded to-
3.1 Permeameters require the use of yokes to complete the
magnetic circuit and are therefore inherently less accurate than gether.
ring test methods. Refer to Test Method A596/A596M for
5.3 Power Supply—The magnetizing current shall be sup-
further details on ring test methods. However, when testing
plied by either storage batteries or dc power supplies. Linear
certainshapesasbarsorwhenmagneticfieldstrengthinexcess
power supplies have been found to be well suited for this use.
of 200 Oe [16 kA/m] is required, permeameters are the only
The source of dc current must be stable, have negligible ripple
practical means of measuring magnetic properties.
and be capable of quickly returning to the stable state after
3.2 Thistestmethodissuitableforspecificationacceptance, switching. When programmable power supplies are used,
service evaluation, research and development and design. either digital or analog programming signals are permissible
provided that equal but opposite polarity current cycling is
3.3 When the test specimen is fabricated from a larger
possible.
sampleandisinthesameconditionasthelargersample,itmay
5.4 Main-Current-ControlRheostats,R —Whenused,these
not exhibit magnetic properties representative of the original
sample. In such instances the test results, when viewed in rheostatsmusthavesufficientpowerratingandheat-dissipating
capacitytohandlethevoltageandlargesttestcurrentandmust
context of past performance history, will be useful for judging
the suitability of the material for the intended application. provide sufficient resistance to limit the test currents to those
required for the lowest magnetic field strength to be used.
4. Interferences
5.5 Hysteresis-Current-Control Rheostats, R —When used,
4.1 In general, permeameters do not maintain a uniform
these rheostats must have the same characteristics as the
magneticfieldineithertheaxialorradialdirectionsaroundthe
main-current control rheostats.
test specimen. The field gradients in both of these directions
5.6 Main-Current Ammeter, A —Magnetizing current mea-
willdifferinthevariouspermeameters.AlsotheH-sensingand
surement shall be conducted using a digital ammeter or
B-sensing coils of the different permeameters are not identical
combination of a digital voltmeter and precision current
in area, in turns, or in length or identically located. Although
sensing resistor with an overall accuracy of better than 0.25%
test specimens are prepared to have uniform physical cross
when the magnetic field strength will be determined from the
section, they may have undetected nonuniform magnetic prop-
current. In those permeameters where the magnetic field
erties radially or axially along the specimen length adjacent to
strength is determined by other means, such as Hall probes or
the H or B coils. Some permeameters may also introduce
H coils, lower accuracy analog instruments can be used. In
such permeameters, the ammeter is used to prevent excessive
currents from being applied and, based on past experience, to
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM roughly establish the required magnetic field strength.
Standards volume information, refer to the standard’s Document Summary page on
5.7 Hysteresis-Current Ammeter, A —The requirements of
the ASTM website. 2
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St., 5.6 shall apply. In general, a separate ammeter is not required.
4th Floor, New York, NY 10036.
5.8 Reversing Switch, S —When nonprogrammable dc cur-
Available from National Institute of Standards and Technology (NIST), 100 1
Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov. rent sources such as storage batteries are used, a current
A341/A341M − 16 (2022)
TABLE 2 Number of Test Strips
reversing switch is required. The reversing switch should be
either a high quality knife switch, mechanical or electrical Nominal Thickness Number of
in. mm Strips
solenoid-operatedcontractorsormercuryswitcheshavinghigh
0.0100 to 0.0250 0.254 to 0.635 12
current rating and the ability to maintain uniform contact
0.0280 to 0.0435 0.711 to 1.105 8
resistance of equal magnitude in both current directions. 0.0500 and over 1.27 and over 4
Switches with contact bounce or other multiple contacting
behavior on make or break must be avoided. Because of the
presence of leakage currents in the open condition, solid state
6.3 When the material is in flat-rolled form and is to be
relays are not permitted.
evaluated as half transverse-half longitudinal, the specimen
shall be sheared to have strips in accordance with Table 2
5.9 Hysteresis Switch, S —This single pole switch must
conform to the same requirements as the reversing Switch, S . exceptthatmultiplesoffourarenotrequired.Whenmaterialis
to be evaluated in one direction, it shall conform to this table
5.10 Fluxmeter, F—Because of their superior accuracy,
or to the requirements for best test quality in a particular
stability, and ease of operation, electronic fluxmeters shall be
permeameter. For strip and sheet less than 0.0100 in.
used to measure the magnetic flux density and, if an H-coil is
[0.254mm] in thickness, the cross-sectional area shall be not
used, the magnetic field strength. Fluxmeters using either
2 2
less than 0.31 in. [200 mm ] and not more than 0.62
operational amplifier and capacitor feedback (analog integra-
2 2
in. [400mm ].
tor) or analog to digital conversion and digital integration are
permitted. The accuracy of the fluxmeter must be better than 6.4 When the test specimen for strip materials is to be half
1% full scale. If analog display meters are used to read the transverseandhalflongitudinal,thepreferredmethodistotest
value of magnetic flux, the measurement should be made on thetransversestripsasonespecimenandthelongitudinalstrips
theuppertwo-thirdsofthescale.Analogfluxmetersmust
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