ASTM A342/A342M-21

Standard Test Methods for Permeability of Weakly Magnetic Materials

SIGNIFICANCE AND USE
3.1 This test method is suitable for specification acceptance, design purposes, service evaluation, regulatory statutes, manufacturing control, and research and development.  
3.2 Because of the restrictions on the specimen shape and size, this test method is most often used to evaluate semifinished product before fabrication of parts.
SCOPE
1.1 These test methods cover four procedures for determination of the permeability [relative permeability]2 of materials having a relative permeability not exceeding 6.0.  
1.2 The test methods covered are as follows:  
1.2.1 Test Method 1—Fluxmetric Method is suitable for materials with relative permeabilities between 1.0 and 4.0. This method permits the user to select the magnetic field strength at which the permeability is to be measured.  
1.2.2 Test Method 2—Permeability of Paramagnetic Materials has been eliminated as an acceptable method of test.  
1.2.3 Test Method 3—Low Mu Permeability Indicator is suitable for measuring the permeability of a material as “less than” or “greater than” that of calibrated standard inserts with relative permeabilities between 1.01 and 6.0, as designated for use in a Low-Mu Permeability Indicator.3 In this method, a small volume of specimen is subjected to a local magnetic field that varies in magnitude and direction, so it is not possible to specify the magnetic field strength at which the measurement is made.  
1.2.4 Test Method 4—Flux Distortion is suitable for materials with relative permeabilities between 1.0 and 2.0. In this method, a small volume of specimen is subjected to a local magnetic field that varies in magnitude and direction, so it is not possible to specify the magnetic field strength at which the measurement is made.4  
1.2.5 Test Method 5—Vibrating Sample Magnetometry is suitable for materials with relative permeabilities between 1.0 and 4.0. This test method permits the user to select the magnetic field strength at which the permeability is to be measured.  
1.3 Materials typically tested by these methods such as austenitic stainless steels may be weakly ferromagnetic. That is, the magnetic permeability is dependent on the magnetic field strength. As a consequence, the results obtained using the different methods may not closely agree with each other. When using Methods 1 and 5, it is imperative to specify the magnetic field strength or range of magnetic field strengths at which the permeabilities have been determined.  
1.4 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.  
1.5 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.  
1.6 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.

General Information

• Status: Published
• Publication Date: 31-Jan-2021
• ICS: 29.030 - Magnetic materials
• Technical Committee: A06 - Magnetic Properties
• Drafting Committee: A06.01 - Test Methods

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: A342/A342M − 21
Standard Test Methods for
1
Permeability of Weakly Magnetic Materials
This standard is issued under the fixed designationA342/A342M; 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 not possible to specify the magnetic field strength at which the
4
measurement is made.
1.1 These test methods cover four procedures for determi-
2 1.2.5 Test Method 5—Vibrating Sample Magnetometry is
nation of the permeability [relative permeability] of materials
suitable for materials with relative permeabilities between 1.0
having a relative permeability not exceeding 6.0.
and 4.0. This test method permits the user to select the
1.2 The test methods covered are as follows:
magnetic field strength at which the permeability is to be
1.2.1 Test Method 1—Fluxmetric Method is suitable for
measured.
materialswithrelativepermeabilitiesbetween1.0and4.0.This
1.3 Materials typically tested by these methods such as
method permits the user to select the magnetic field strength at
austenitic stainless steels may be weakly ferromagnetic. That
which the permeability is to be measured.
is, the magnetic permeability is dependent on the magnetic
1.2.2 Test Method 2—Permeability of Paramagnetic Mate-
field strength.As a consequence, the results obtained using the
rials has been eliminated as an acceptable method of test.
differentmethodsmaynotcloselyagreewitheachother.When
1.2.3 Test Method 3—Low Mu Permeability Indicator is
usingMethods1and5,itisimperativetospecifythemagnetic
suitable for measuring the permeability of a material as “less
field strength or range of magnetic field strengths at which the
than” or “greater than” that of calibrated standard inserts with
permeabilities have been determined.
relative permeabilities between 1.01 and 6.0, as designated for
3
1.4 The values and equations stated in customary (cgs-emu
use in a Low-Mu Permeability Indicator. In this method, a
smallvolumeofspecimenissubjectedtoalocalmagneticfield and inch-pound) or SI units are to be regarded separately as
standard. Within this standard, SI units are shown in brackets
that varies in magnitude and direction, so it is not possible to
specifythemagneticfieldstrengthatwhichthemeasurementis exceptforthesectionsconcerningcalculationswherethereare
separate sections for the respective unit systems. The values
made.
stated in each system may not be exact equivalents; therefore,
1.2.4 Test Method 4—Flux Distortion is suitable for mate-
each system shall be used independently of the other. Combin-
rials with relative permeabilities between 1.0 and 2.0. In this
ingvaluesfromthetwosystemsmayresultinnonconformance
method, a small volume of specimen is subjected to a local
with this standard.
magnetic field that varies in magnitude and direction, so it is
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1 responsibility of the user of this standard to establish appro-
These test methods are under the jurisdiction of ASTM Committee A06 on
Magnetic Properties and are the direct responsibility of Subcommittee A06.01 on priate safety, health, and environmental practices and deter-
Test Methods.
mine the applicability of regulatory limitations prior to use.
Current edition approved Feb. 1, 2021. Published February 2021. Originally
1.6 This international standard was developed in accor-
approved in 1949. Last previous edition approved in 2014 as A342/A342M–14.
dance with internationally recognized principles on standard-
DOI: 10.1520/A0342_A0342M-21.
2
Test Methods 1 and 5 actually measure magnetic susceptibility. The perme-
ization established in the Decision on Principles for the
ability (µ) [relative permeability (µ )] is related to the susceptibility (κ)bythe
r
Development of International Standards, Guides and Recom-
equations:
mendations issued by the World Trade Organization Technical
µ=1+4πκ (cgs-emu)
µ =1+κ (SI) Barriers to Trade (TBT) Committee.
r
The term permeability has been retained in these test methods because of its
widespread commercial and technological usage.
3 4
Thesolesourceofsupplyoftheapparatusknowntothecommitteeatthistime ThesolesourceofsupplyoftheapparatusknowntotheCommitteeatthistime
is Low-Mu Permeability Indicator, manufactured by Severn Engineering Co., Inc., is the Magnetoscop manufactured by INSTITUT DR. P
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: A342/A342M − 14 A342/A342M − 21
Standard Test Methods for
1
Permeability of Weakly Magnetic Materials
This standard is issued under the fixed designation A342/A342M; 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 U.S. Department of Defense.
1. Scope
2
1.1 These test methods cover four procedures for determination of the permeability [relative permeability] of materials having
a relative permeability not exceeding 6.0.
1.2 The test methods covered are as follows:
1.2.1 Test Method 1—Fluxmetric Method is suitable for materials with relative permeabilities between 1.0 and 4.0. This method
permits the user to select the magnetic field strength at which the permeability is to be measured.
1.2.2 Test Method 2—Permeability of Paramagnetic Materials has been eliminated as an acceptable method of test.
1.2.3 Test Method 3—Low Mu Permeability Indicator is suitable for measuring the permeability of a material as “less than” or
“greater than” that of calibrated standard inserts with permeability relative permeabilities between 1.01 and 6.0, as designated for
3
use in a Low-Mu Permeability Indicator. In this method, a small volume of specimen is subjected to a local magnetic field that
varies in magnitude and direction, so it is not possible to specify the magnetic field strength at which the measurement is made.
1.2.4 Test Method 4—Flux Distortion is suitable for materials with permeability relative permeabilities between 1.0 and 2.0. In
this method, a small volume of specimen is subjected to a local magnetic field that varies in magnitude and direction, so it is not
4
possible to specify the magnetic field strength at which the measurement is made.
1.2.5 Test Method 5—Vibrating Sample Magnetometry is suitable for materials with permeability relative permeabilities between
1.0 and 4.0. This test method permits the user to select the magnetic field strength at which the permeability is to be measured.
1
These test methods are under the jurisdiction of ASTM Committee A06 on Magnetic Properties and are the direct responsibility of Subcommittee A06.01 on Test
Methods.
Current edition approved May 1, 2014Feb. 1, 2021. Published May 2014February 2021. Originally approved in 1949. Last previous edition approved in 20122014 as
A342/A342MA342/A342M – 14.–04 (2012). DOI: 10.1520/A0342_A0342M-14.10.1520/A0342_A0342M-21.
2
Test Methods 1 and 5 actually measure magnetic susceptibility. The permeability (μ) [relative permeability (μ )] is related to the susceptibility (κ) by the equations:
r
μ = 1 + 4πκ (cgs-emu)
μ = 1 + κ (SI)
r
The term permeability has been retained in these test methods because of its widespread commercial and technological usage.
3
The sole source of supply of the apparatus known to the committee at this time is Low-Mu Permeability Indicator, manufactured by Severn Engineering Co., Inc., 555
Stage Rd., Suite 1A, Auburn, AL 36830, http://www.severnengineering.com. (Indicators can be returned for recalibration.) If you are the user of this test method is aware
of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible
1
technical committee, which you may attend.
4
The sole source of supply of the apparatus known to the Committee at this time is the Magnetoscop manufactured by INSTITUT DR. POERSTER GmbH & Co. KG.
in Laisen 70, 72766, Reutlingen, Germany. (Probes can be returned for calibration.) If you are aware of alternatethe user of this test method is aware of alternative suppliers,
1
please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee,
which you may attend.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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A342/A342M − 21
1.3 Materials typically tested by these methods such as austenitic stainless steels may be weakly ferromagnetic. That is, the
magnetic permeability is dependent on the magnetic field strength. As a consequence, the results obtained using the different
methods may not closely agree with each o
...