ASTM A799/A799M-10(2020)
(Practice)Standard Practice for Steel Castings, Stainless, Instrument Calibration, for Estimating Ferrite Content
Standard Practice for Steel Castings, Stainless, Instrument Calibration, for Estimating Ferrite Content
SIGNIFICANCE AND USE
4.1 The amount of ferrite present in an austenitic stainless steel has been shown to influence the strength, toughness, and corrosion resistance of this type of cast alloy. The amount of ferrite present tends to correlate well with the magnetic permeability of the steel. The methods described in this standard cover calibration practice for estimating ferrite by the magnetic permeability of the steel. The practice is inexpensive to use over large areas of the cast part and is nondestructive.
4.2 This practice has been used for research, alloy development, quality control, and manufacturing control.
4.2.1 Many instruments are available having different designs and different principles of operation. When the probe is placed on the material being investigated, a closed magnetic circuit is formed allowing measurement of the magnetic permeability. When calibrated with standards having known ferrite content, this permeability indicates the ferrite content of the material being analyzed. The estimated ferrite content is read from a calibrated dial or from a digital readout dial. Follow the manufacturer's instructions for proper calibration of the instrument.
4.3 Since this practice measures magnetic attraction and not ferrite directly, it is subject to all of the variables that affect magnetic permeability, such as the shape, size, orientation, and composition of the ferrite phase. These in turn are affected by thermal history. Ferrite measurements by magnetic methods have also been found to be affected by the surface finish of the material being analyzed.
4.4 Magnetic methods should not be used for arbitration of conflicts on ferrite content except when agreed upon between manufacturer and purchaser.
SCOPE
1.1 This practice covers the procedure for calibration of instruments to be used for estimating the ferrite content of the microstructure of cast stainless steels by magnetic response or measurement of permeability. This procedure covers both primary and secondary instruments.
1.1.1 A primary instrument is one that has been calibrated using National Institute of Standards and Technology-Standard Reference Material (NIST-SRM) thickness coating standards. It is a laboratory tool to be used with test specimens. Some primary instruments may be used to directly measure the ferrite content of castings.
1.1.2 A secondary instrument is one that has been calibrated by the use of secondary standards that have been measured by a calibrated primary instrument. Secondary instruments are to be used to directly measure the ferrite content of castings.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. 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 the standard.
1.2.1 Within the text, the SI units are shown in brackets.
1.3 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.
1.4 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
Relations
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: A799/A799M − 10 (Reapproved 2020)
Standard Practice for
Steel Castings, Stainless, Instrument Calibration, for
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Estimating Ferrite Content
This standard is issued under the fixed designationA799/A799M; 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.
1. Scope 2. Referenced Documents
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2.1 ASTM Standards:
1.1 This practice covers the procedure for calibration of
A941 TerminologyRelatingtoSteel,StainlessSteel,Related
instruments to be used for estimating the ferrite content of the
Alloys, and Ferroalloys
microstructure of cast stainless steels by magnetic response or
B499 Test Method for Measurement of Coating Thicknesses
measurement of permeability. This procedure covers both
by the Magnetic Method: Nonmagnetic Coatings on
primary and secondary instruments.
Magnetic Basis Metals
1.1.1 A primary instrument is one that has been calibrated
E562 Test Method for Determining Volume Fraction by
using National Institute of Standards andTechnology-Standard
Systematic Manual Point Count
Reference Material (NIST-SRM) thickness coating standards.
It is a laboratory tool to be used with test specimens. Some 2.2 NIST Standard:
primaryinstrumentsmaybeusedtodirectlymeasuretheferrite NIST-SRM Coating Thickness Standards
content of castings.
NOTE 1—The specific coating thickness standards previously refer-
1.1.2 Asecondary instrument is one that has been calibrated
enced in this practice are no longer available. Similar ones are now
by the use of secondary standards that have been measured by available from NIST.
a calibrated primary instrument. Secondary instruments are to
3. Terminology
be used to directly measure the ferrite content of castings.
3.1 Definitions—The definitions in Terminology A941 are
1.2 The values stated in either SI units or inch-pound units
applicable to this standard.
are to be regarded separately as standard. The values stated in
each system may not be exact equivalents; therefore, each 3.2 Definitions of Terms Specific to This Standard:
system shall be used independently of the other. Combining 3.2.1 ferrite, n—the body-centered cubic microconstituent
values from the two systems may result in nonconformance in stainless steel.
with the standard.
3.2.2 ferrite percentage, n—a value designating the ferrite
1.2.1 Within the text, the SI units are shown in brackets.
content of stainless steels.
3.2.2.1 Discussion—The Steel Founders’ Society of
1.3 This standard does not purport to address all of the
America (SFSA) has assigned ferrite percentages to the series
safety concerns, if any, associated with its use. It is the
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of NIST coating thickness standards. This assignment was
responsibility of the user of this standard to establish appro-
based on the magnetic attraction for a standard magnet by the
priate safety, health, and environmental practices and deter-
coating standards when compared with the magnetic attraction
mine the applicability of regulatory limitations prior to use.
of the same magnet by a series of cast stainless steels whose
1.4 This international standard was developed in accor-
ferrite content had been determined by an accurate metallo-
dance with internationally recognized principles on standard-
graphic point count. A similar assignment based on magnetic
ization established in the Decision on Principles for the
permeability was also established. Algebraic equations have
Development of International Standards, Guides and Recom-
now been derived from a plot of the thickness of these
mendations issued by the World Trade Organization Technical
standards and the assigned ferrite percentages. By the use of
Barriers to Trade (TBT) Committee.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
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This practice is under the jurisdiction of ASTM Committee A01 on Steel, contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee Standards volume information, refer to the standard’s Document Summary page on
A01.18 on Castings. the ASTM website.
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Current edition approved March 1, 2020. Published March 2020. Originally Aubrey, L. S., Weiser, P. F., Pollard, W. J., and Schoefer, E. A., “Ferrite
approved in 1982. Last previous edition approved in 2015 as A799/A799M – 10 MeasurementandControlinCastDuplexStainlessSteels,”StainlessSteelCastings,
(2015). DOI: 10.1520/A0799_A0799M-10R20. ASTM STP 756, ASTM Intern
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