ASTM A341/A341M-00(2005)
(Test Method)Standard Test Method for Direct Current Magnetic Properties of Materials Using D-C Permeameters and the Ballistic Test Methods
Standard Test Method for Direct Current Magnetic Properties of Materials Using D-C Permeameters and the Ballistic Test Methods
SIGNIFICANCE AND USE
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 A 596/A 596M for further details on ring test methods. However, when testing certain shapes as bars or when magnetic field strength in excess of 200 Oe [15.9 or more kA/m] are required, permeameters are the only practical means of measuring magnetic properties.
This test method is suitable for specification acceptance, service evaluation, research and development and design.
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 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.
1.2 This test method shall be used in conjunction with Practice A 34/A 34M.
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 flux density range from essentially zero to intrinsic saturation for most materials.
1.5 Recommendations of the useful magnetic field strength range for each of the permeameters are shown in . 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 and in appropriate sections of this document. For the official definitions, see Terminology A 340. Note that the term flux density used in this document is synonymous with the term magnetic induction.
1.7 The values and equations stated in customary cgs-emu and inch-pound or SI units are to be regarded separately as standard. Within this standard, SI units are shown in brackets except for the sections concerning calculations where there are separate sections for the respective unit systems. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with this standard.
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.
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Designation:A341/A341M–00 (Reapproved 2005)
Standard Test Method for
Direct Current Magnetic Properties of Materials Using D-C
Permeameters and the Ballistic Test Methods
ThisstandardisissuedunderthefixeddesignationA341/A341M;thenumberimmediatelyfollowingthedesignationindicatestheyear
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 (e) 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 separate sections for the respective unit systems. The values
stated in each system may not be exact equivalents; therefore,
1.1 This test method provides dc permeameter tests for the
each system shall be used independently of the other. Combin-
basicmagneticpropertiesofmaterialsintheformofbars,rods,
ingvaluesfromthetwosystemsmayresultinnonconformance
wire, or strip specimens which may be cut, machined, or
with this standard.
ground from cast, compacted, sintered, forged, extruded,
1.8 This standard does not purport to address all of the
rolled, or other fabricated materials. It includes tests for
safety concerns, if any, associated with its use. It is the
determination of the normal induction under symmetrically
responsibility of the user of this standard to establish appro-
cyclically magnetized (SCM) conditions and the hysteresis
priate safety and health practices and determine the applica-
loop (B-H loop) taken under conditions of rapidly changing or
bility of regulatory limitations prior to use.
steep wavefront reversals of the direct current magnetic field
strength.
2. Referenced Documents
1.2 This test method shall be used in conjunction with
2.1 ASTM Standards:
Practice A34/A34M.
A34/A34M Practice for Sampling and Procurement Test-
1.3 This test method covers a range of magnetic field
ing of Magnetic Materials
strength in the specimen from about 0.05 Oe [4 A/m] up to
A340 Terminology of Symbols and Definitions Relating to
above 5000 Oe [400 kA/M] through the use of several
Magnetic Testing
permeameters. The separate permeameters cover this test
A596/A596M Test Method for Direct-Current Magnetic
region in several overlapping ranges.
Properties of Materials Using the Ballistic Method and
1.4 Normal induction and hysteresis properties may be
Ring Specimens
determined over the flux density range from essentially zero to
2.2 IEC Standard:
intrinsic saturation for most materials.
Publication 60404-4, Ed. 2.0 Magnetic Materials – Part 4:
1.5 Recommendations of the useful magnetic field strength
2 Methods of Measurement of D.C. Magnetic Properties of
range for each of the permeameters are shown in Table 1 .
Iron and Steel, IEC, 1995
Also,seeSections3and4forgenerallimitationsrelativetothe
2.3 Other Documents:
use of permeameters.
NIST Circular No. 74, pg. 269
1.6 Thesymbolsandabbreviateddefinitionsusedinthistest
NIST Scientific Paper 117, SPBTA
method appear with Fig. 1 and in appropriate sections of this
document. For the official definitions, see TerminologyA340.
3. Significance and Use
Note that the term flux density used in this document is
3.1 Permeameters require the use of yokes to complete the
synonymous with the term magnetic induction.
magneticcircuitandarethereforeinherentlylessaccuratethan
1.7 The values and equations stated in customary cgs-emu
ring test methods. Refer to Test Method A596/A596M for
and inch-pound or SI units are to be regarded separately as
further details on ring test methods. However, when testing
standard. Within this standard, SI units are shown in brackets
certainshapesasbarsorwhenmagneticfieldstrengthinexcess
exceptforthesectionsconcerningcalculationswherethereare
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee A06 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
MagneticPropertiesandisthedirectresponsibilityofSubcommitteeA06.01onTest Standards volume information, refer to the standard’s Document Summary page on
Methods. the ASTM website.
Current edition approved Nov. 1, 2005. Published November 2005. Originally Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
approved in 1969. Last previous edition approved in 2000 as A341/A341M–00. 4th Floor, New York, NY 10036.
2 5
The boldface numbers in parentheses refer to a list of references at the end of Available from National Institute of Standards and Technology (NIST), 100
this standard. Bureau Dr., Stop 3460, Gaithersburg, MD 20899-3460.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
A341/A341M–00 (2005)
TABLE 1 Permeameters
A
Magnetizing Coil
Useful Magnetic Field Strength Range
H Measuring Reluctance
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.
test specimen. The field gradients in both of these directions
willdifferinthevariouspermeameters.AlsotheH-sensingand
B-sensing coils of the different permeameters are not identical
in area, in turns, or in length or identically located. Although
test specimens are prepared to have uniform physical cross
section, they may have undetected nonuniform magnetic prop-
erties radially or axially along the specimen length adjacent to
the H or B coils. Some permeameters may also introduce
clamping strains into the test specimen. For the above reasons
test results obtained on a test specimen with one type per-
meameter may not agree closely with those obtained on the
same test specimen using another type of permeameter.
NOTE 1—
A —Multirange ammeter (main current)
5. Apparatus
A —Multirange ammeter (hysteresis current)
B—Flux density test position for Switch S
5.1 Because of the differences in physical construction of
F—Electronic Integrator
the various permeameters listed in Table 1, no standard list of
H—Magnetic field strength test position for Switch S
components is given. When used with a particular type of
N —Magnetizing coil
permeameter, the components should conform to the general
N —Flux sensing (B) coil
N —Magnetic field strength sensing coil requirementslistedbelow.Abasicschematicofapermeameter
R —Main current control rheostat
1 is shown in Fig. 1.
R —Hysteresis current control rheostat
5.2 Permeameter—The particular permeameter used shall
S —Reversing switch for magnetizing current
be of high quality construction. The yokes should be made of
S —Shunting switch for hysteresis current control rheostat
high permeability alloy such as oriented or nonoriented silicon
S —Integrator selector switch
SP—Specimen iron or nickel-iron alloy, although low carbon steel or iron is
FIG. 1 Basic Circuit Using Permeameter
acceptable in certain instances. The preferred yolk dimensions
are listed in the appended references (see Table 1). Deviations
fromthesedimensionsshouldbesuchthattheyolkisoperating
of200Oe[15.9ormorekA/m]arerequired,permeametersare
at or below the point of maximum permeability for the highest
the only practical means of measuring magnetic properties.
test flux densities encountered. Yoke construction may consist
3.2 Thistestmethodissuitableforspecificationacceptance,
of either stacked laminations or stripwound C cores suitably
service evaluation, research and development and design.
bolted or adhesive bonded together.
3.3 When the test specimen is fabricated from a larger
sampleandisinthesameconditionasthelargersample,itmay 5.3 Power Supply—The magnetizing current shall be sup-
not exhibit magnetic properties representative of the original plied by either storage batteries or dc power supplies. Bipolar
sample. In such instances the test results, when viewed in programmable linear power supplies have been found to be
context of past performance history, will be useful for judging wellsuitedforthisuse.Thesourceofdccurrentmustbestable,
the suitability of the material for the intended application. have negligible ripple and be capable of quickly returning to
the stable state after switching. When programmable power
4. Interferences
suppliesareused,eitherdigitaloranalogprogrammingsignals
4.1 In general, permeameters do not maintain a uniform are permissible provided that equal but opposite polarity
magneticfieldineithertheaxialorradialdirectionsaroundthe current cycling is possible.
A341/A341M–00 (2005)
TABLE 2 Number of Test Strips
5.4 Main-Current-Control Rheostats, R —When used,
these rheostats must have sufficient power rating and heat- Nominal Thickness Gage Number of
in. mm Number Strips
dissipating capacity to handle the voltage and largest test
0.0100 to 0.0250 0.254 to 0.635 32 to 24, incl 12
current and must contain sufficient resistance to limit the test
0.0280 to 0.0435 0.711 to 1.105 23 to 19, incl 8
0.0500 and over 1.27 and over 18 and thicker 4
currentstothoserequiredforthelowestmagneticfieldstrength
to be used.
5.5 Hysteresis-Current-Control Rheostats, R —When used,
these rheostats must have the same characteristics as the
5.12 Magnetic Field Strength Measuring Devices—Certain
main-current control rheostats.
permeameters do not or cannot use the magnetizing current to
5.6 Main-Current Ammeter, A —Magnetizing current mea-
determine the magnetic field strength accurately. Such per-
surement shall be conducted using a digital ammeter or
meameters instead use stationary H coils, flip coils, or Hall
combination of a digital voltmeter and precision shunt resistor
probes. When such devices are used, they shall be capable of
with an overall accuracy of better than 0.25% when the
determiningtheapparentmagneticfieldstrengthtoaccuracyof
magnetic field strength will be determined from the current. In
1.0% or better.
those permeameters where the magnetic field strength is
determined by other means, such as Hall probes or H coils, 6. Test Specimens
lower accuracy analog instruments can be used. In such
6.1 Test specimen area shall normally be determined from
permeameters, the ammeter is used to prevent excessive
mass, length, and density as indicated in 9.1 and 10.1. When
currents from being applied and, based on past experience, to
thetestspecimenismachinedorgroundtohaveaverysmooth
roughly establish the required magnetic field strength.
surface, the physical dimensions obtained from micrometer
5.7 Hysteresis-Current Ammeter, A —The requirements of measurements may be used to calculate the cross-sectional
5.6 shall apply. In general, a separate ammeter is not required. area.
6.2 Test specimens in bar form may be of round, square, or
5.8 Reversing Switch, S —When nonprogrammable dc cur-
rectangular cross-sectional shape. In some permeameters the
rent sources such as storage batteries are used, a current
bar specimen may be a half round or any shape having a
reversing switch is required. The reversing switch should be
uniform cross-sectional area. Certain permeameters must have
either a high quality knife switch, mechanical or electrical
a good magnetic joint between the ends of the test specimen
solenoid-operatedcontractorsormercuryswitcheshavinghigh
and the permeameter yoke or pole faces. Pole shoes may be
current rating and the ability to maintain uniform contact
necessary to create this joint. Generally, to achieve a good
resistance of equal magnitude in both current directions.
magnetic joint, the test specimen must be of square or
Switches with contact bounce or other multiple contacting
rectangular cross section and must be machined or ground to
behavior on make or break must be avoided. Because of the
have straight and parallel surfaces. For permeameters using
presence of leakage currents in the open condition, solid state
specimens butted to pole pieces, the specimen ends must be
relays are not permitted.
smooth and parallel.
5.9 Hysteresis Switch, S —This single pole switch must
6.3 When the material is in flat-rolled form and is to be
conform to the same requirements as the reversing Switch, S .
evaluated as half transverse-half longitudinal, the specimen
5.10 Integrator, F—Because of their superior accuracy,
shall be sheared to have strips in multiples of four in accor-
stability, and ease of operation, electronic charge integrators
dance with Table 2. When material is to be evaluated in one
are the preferred means of measuring magnetic flux. Integra-
direction, it shall conform to this table or to the requirements
tors using either operational amplifier and capacitor feedback
for best test quality in a particular permeameter. For gages No.
(analog integrator) or pulse counting are permitted. The accu-
33 and thinner, the cross-sectional area shall be not less than
2 2 2 2
racy of the integrator must be better than 1% full scale. If
0.31 in. [200 mm ] and not more than 0.62 in. [400 mm ].
analog display meters are used to read the value of flux, the
6.4 When the test specimen for strip materials is to be half
measurement should be made on the upper two-thirds of the
transverse and half longitudinal, the strips shall be positioned
scale. Analog integrators must have drift adjust circuitry and
to be composed of alternately transverse and longitudinal
−6
thedriftshouldnotexceed100Maxwell-turns[10 Wb-turns]
throughout the specimen and a transverse strip shall be placed
per minute on the most sensitive range. It is also desirable that
adjacent to the permeameter’s yoke or pole face.
theintegratorhaveappropriatescalingcircuitrytopermitdirect
6.5 For full testing accuracy, the length and size of the test
reading of either flux (f) or flux density (B). Ballistic galva-
specimen must meet the requirements of the permeameter
nometersormovingcoilfluxmetersarepermittedprovidedthe
being used. Generally, for most permeam
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