ASTM E1245-03(2023)
(Practice)Standard Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic Image Analysis
Standard Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic Image Analysis
SIGNIFICANCE AND USE
5.1 This practice is used to assess the indigenous inclusions or second-phase constituents of metals using basic stereological procedures performed by automatic image analyzers.
5.2 This practice is not suitable for assessing the exogenous inclusions in steels and other metals. Because of the sporadic, unpredictable nature of the distribution of exogenous inclusions, other methods involving complete inspection, for example, ultrasonics, must be used to locate their presence. The exact nature of the exogenous material can then be determined by sectioning into the suspect region followed by serial, step-wise grinding to expose the exogenous matter for identification and individual measurement. Direct size measurement rather than application of stereological methods is employed.
5.3 Because the characteristics of the indigenous inclusion population vary within a given lot of material due to the influence of compositional fluctuations, solidification conditions and processing, the lot must be sampled statistically to assess its inclusion content. The largest lot sampled is the heat lot but smaller lots, for example, the product of an ingot, within the heat may be sampled as a separate lot. The sampling of a given lot must be adequate for the lot size and characteristics.
5.4 The practice is suitable for assessment of the indigenous inclusions in any steel (or other metal) product regardless of its size or shape as long as enough different fields can be measured to obtain reasonable statistical confidence in the data. Because the specifics of the manufacture of the product do influence the morphological characteristics of the inclusions, the report should state the relevant manufacturing details, that is, data regarding the deformation history of the product.
5.5 To compare the inclusion measurement results from different lots of the same or similar types of steels, or other metals, a standard sampling scheme should be adopted such as described in Test Method...
SCOPE
1.1 This practice describes a procedure for obtaining stereological measurements that describe basic characteristics of the morphology of indigenous inclusions in steels and other metals using automatic image analysis. The practice can be applied to provide such data for any discrete second phase.
Note 1: Stereological measurement methods are used in this practice to assess the average characteristics of inclusions or other second-phase particles on a longitudinal plane-of-polish. This information, by itself, does not produce a three-dimensional description of these constituents in space as deformation processes cause rotation and alignment of these constituents in a preferred manner. Development of such information requires measurements on three orthogonal planes and is beyond the scope of this practice.
1.2 This practice specifically addresses the problem of producing stereological data when the features of the constituents to be measured make attainment of statistically reliable data difficult.
1.3 This practice deals only with the recommended test methods and nothing in it should be construed as defining or establishing limits of acceptability.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in 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
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: E1245 − 03 (Reapproved 2023)
Standard Practice for
Determining the Inclusion or Second-Phase Constituent
Content of Metals by Automatic Image Analysis
This standard is issued under the fixed designation E1245; 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.
INTRODUCTION
This practice may be used to produce stereological measurements that describe the amount, number,
size, and spacing of the indigenous inclusions (sulfides and oxides) in steels. The method may also be
applied to assess inclusions in other metals or to assess any discrete second-phase constituent in any
material.
1. Scope 1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This practice describes a procedure for obtaining stereo-
ization established in the Decision on Principles for the
logical measurements that describe basic characteristics of the
Development of International Standards, Guides and Recom-
morphology of indigenous inclusions in steels and other metals
mendations issued by the World Trade Organization Technical
using automatic image analysis. The practice can be applied to
Barriers to Trade (TBT) Committee.
provide such data for any discrete second phase.
NOTE 1—Stereological measurement methods are used in this practice 2. Referenced Documents
to assess the average characteristics of inclusions or other second-phase
2.1 ASTM Standards:
particles on a longitudinal plane-of-polish. This information, by itself,
E3 Guide for Preparation of Metallographic Specimens
does not produce a three-dimensional description of these constituents in
space as deformation processes cause rotation and alignment of these
E7 Terminology Relating to Metallography
constituents in a preferred manner. Development of such information
E45 Test Methods for Determining the Inclusion Content of
requires measurements on three orthogonal planes and is beyond the scope
Steel
of this practice.
E768 Guide for Preparing and Evaluating Specimens for
1.2 This practice specifically addresses the problem of
Automatic Inclusion Assessment of Steel
producing stereological data when the features of the constitu-
ents to be measured make attainment of statistically reliable
3. Terminology
data difficult.
3.1 Definitions:
1.3 This practice deals only with the recommended test
3.1.1 For definitions of terms used in this practice, see
methods and nothing in it should be construed as defining or Terminology E7.
establishing limits of acceptability.
3.2 Symbols:
1.4 The values stated in SI units are to be regarded as 2
¯
A = the average area of inclusions or particles, μm .
standard. No other units of measurement are included in this
A = the area fraction of the inclusion or constituent.
A
standard.
A = the area of the detected feature.
i
1.5 This standard does not purport to address all of the A = the measurement area (field area, mm ).
T
H = the total projected length in the hot-working
safety concerns, if any, associated with its use. It is the
T
direction of the inclusion or constituent in the
responsibility of the user of this standard to establish appro-
field, μm.
priate safety, health, and environmental practices and deter-
¯
L = the average length in the hot-working direction
mine the applicability of regulatory limitations prior to use.
of the inclusion or constituent, μm.
This practice is under the jurisdiction of ASTM Committee E04 on Metallog-
raphy and is the direct responsibility of Subcommittee E04.14 on Quantitative
Metallography. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 1, 2023. Published April 2023. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1988. Last previous edition approved in 2016 as E1245 – 03(2016). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E1245-03R23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1245 − 03 (2023)
example, ultrasonics, must be used to locate their presence.
L = the true length of scan lines, pixel lines, or grid
T
The exact nature of the exogenous material can then be
lines (number of lines times the length of the
determined by sectioning into the suspect region followed by
lines divided by the magnification), mm.
serial, step-wise grinding to expose the exogenous matter for
n = the number of fields measured.
identification and individual measurement. Direct size mea-
N = the number of inclusions or constituents of a
A
given type per unit area, mm . surement rather than application of stereological methods is
N = the number of inclusions or constituent particles employed.
i
or the number of feature interceptions, in the
5.3 Because the characteristics of the indigenous inclusion
field.
population vary within a given lot of material due to the
N = the number of interceptions of inclusions or
L
influence of compositional fluctuations, solidification condi-
constituent particles per unit length (mm) of scan
tions and processing, the lot must be sampled statistically to
lines, pixel lines, or grid lines.
assess its inclusion content. The largest lot sampled is the heat
PP = the number of detected picture points.
i
lot but smaller lots, for example, the product of an ingot, within
PP = the total number of picture points in the field
T
the heat may be sampled as a separate lot. The sampling of a
area.
given lot must be adequate for the lot size and characteristics.
s = the standard deviation.
t = a multiplier related to the number of fields 5.4 The practice is suitable for assessment of the indigenous
examined and used in conjunction with the
inclusions in any steel (or other metal) product regardless of its
standard deviation of the measurements to deter- size or shape as long as enough different fields can be measured
mine the 95 % CI
to obtain reasonable statistical confidence in the data. Because
V = the volume fraction.
the specifics of the manufacture of the product do influence the
V
¯
X = the mean of a measurement.
morphological characteristics of the inclusions, the report
X = an individual measurement.
i should state the relevant manufacturing details, that is, data
λ = the mean free path (μm) of the inclusion or
regarding the deformation history of the product.
constituent type perpendicular to the hot-
5.5 To compare the inclusion measurement results from
working direction.
different lots of the same or similar types of steels, or other
∑X = the sum of all of a particular measurement over
metals, a standard sampling scheme should be adopted such as
n fields.
described in Test Methods E45.
∑X = the sum of all of the squares of a particular
measurement over n fields.
5.6 The test measurement procedures are based on the
95 % CI = the 95 % confidence interval.
statistically exact mathematical relationships of stereology for
% RA = the relative accuracy, %.
planar surfaces through a three-dimensional object examined
using reflected light (see Note 1).
4. Summary of Practice
5.7 The orientation of the sectioning plane relative to the
4.1 The indigenous inclusions or second-phase constituents
hot-working axis of the product will influence test results. In
in steels and other metals are viewed with a light microscope
general, a longitudinally oriented test specimen surface is
or a scanning electron microscope using a suitably prepared
employed in order to assess the degree of elongation of the
metallographic specimen. The image is detected using a
malleable (that is, deformable) inclusions.
television-type scanner tube (solid-state or tube camera) and
5.8 Oxide inclusion measurements for cast metals, or for
displayed on a high resolution video monitor. Inclusions are
wrought sections that are not fully consolidated, may be biased
detected and discriminated based on their gray-level intensity
by partial or complete detection of fine porosity or mi-
differences compared to each other and the unetched matrix.
croshrinkage cavities and are not recommended. Sulfides can
Measurements are made based on the nature of the discrimi-
be discriminated from such voids in most instances and such
nated picture point elements in the image. These measure-
measurements may be performed.
ments are made on each field of view selected. Statistical
evaluation of the measurement data is based on the field-to-
5.9 Results of such measurements may be used to qualify
field or feature-to-feature variability of the measurements.
material for shipment according to agreed upon guidelines
between purchaser and manufacturer, for comparison of differ-
5. Significance and Use
ent manufacturing processes or process variations, or to pro-
5.1 This practice is used to assess the indigenous inclusions
vide data for structure-property-behavior studies.
or second-phase constituents of metals using basic stereologi-
6. Interferences
cal procedures performed by automatic image analyzers.
6.1 Voids in the metal due to solidification, limited hot
5.2 This practice is not suitable for assessing the exogenous
ductility, or improper hot working practices may be detected as
inclusions in steels and other metals. Because of the sporadic,
oxides because their gray level range is similar to that of
unpredictable nature of the distribution of exogenous
oxides.
inclusions, other methods involving complete inspection, for
3 4
Vander Voort, G. F., “Image Analysis,” Vol 10, 9th ed., Metals Handbook: Underwood, E. E., Quantitative Stereology, Addison-Wesley Publishing Co.,
Materials Characterization, ASM, Metals Park, OH, 1986, pp. 309–322. Reading, MA, 1970.
E1245 − 03 (2023)
6.2 Exogenous inclusions, if present on the plane-of-polish, 8. Sampling
will be detected as oxides and will bias the measurements of
8.1 In general, sampling procedures for heat lots or for
the indigenous oxides. Procedures for handling this situation
product lots representing material from a portion of a heat lot
are given in 12.5.9.
are the same as described in Test Methods E45 (Microscopical
Methods) or as defined by agreements between manufacturers
6.3 Improper polishing techniques that leave excessively
and users.
large scratches on the surface, or create voids in or around
inclusions, or remove part or all of the inclusions, or dissolve
8.2 Characterization of the inclusions in a given heat lot, or
water-soluble inclusions, or create excessive relief will bias the
a subunit of the heat lot, improves as the number of specimens
measurement results.
tested increases. Testing of billet samples from the extreme top
and bottom of the ingots (after discards are taken) will define
6.4 Dust, pieces of tissue paper, oil or water stains, or other
worst conditions of oxides and sulfides. Specimens taken from
foreign debris on the surface to be examined will bias the
interior billet locations will be more representative of the bulk
measurement results.
of the material. Additionally, the inclusion content will vary
6.5 If the programming of the movement of the automatic
with the ingot pouring sequence and sampling should test at
stage is improper so that the specimen moves out from under
least the first, middle and last ingot teemed. The same trends
the objective causing detection of the mount or air (unmounted
are observed in continuously cast steels. Sampling schemes
specimen), measurements will be biased.
must be guided by sound engineering judgment, the specific
processing parameters, and producer-purchaser agreements.
6.6 Vibrations must be eliminated if they cause motion in
the image.
9. Test Specimens
6.7 Dust in the microscope or camera system may produce
9.1 In general, test specimen orientation within the test lot is
spurious indications that may be detected as inclusions.
the same as described in Test Methods E45 (Microscopical
Consequently, the imaging system must be kept clean.
Methods). The plane-of-polish should be parallel to the hot-
working axis and, most commonly, taken at the quarter-
7. Apparatus
thickness location. Other test locations may also be sampled,
for example, subsurface and center locations, as desired or
7.1 A reflected light microscope equipped with bright-field
objectives of suitable magnifications is used to image the required.
microstructure. The use of upright-type microscope allows for
9.2 The surface to be polished should be large enough in
easier stage control when selecting field areas; however, the
area to permit measurement of at least 100 fields at the
specimens will require leveling which can create artifacts, such
necessary magnification. Larger surface areas are beneficial
as scratches, dust remnants and staining, on the polished
whenever the product form permits. A minimum polished
surface (see 12.2.1). The use of inverted microscopes usually
surface area of 160 mm is preferred.
result in a more consistent focus between fields, thereby,
9.3 Thin product forms can be sampled by placing a number
requiring less focussing between fields and a more rapid
of longitudinally oriented pieces in the mount so that the
completion of the procedure. A scanning electron microscope
sampling area is sufficient.
also may be used to image the structure.
9.4 Guide E768 lists two accepted methods for preparing
7.2 A programmable automatic stage to control movement
steel samples for the examination of inclusion content using
in the x and y directions without operator attention is recom-
image analysis. The standard also lists a procedure to test the
mended (but not mandatory) to prevent bias in field selection
quality of the preparation using differential interference con-
and to minimize operator fatigue.
trast (DIC).
7.3 An automatic focus device may also be employed if
10. Specimen Preparation
found to be reliable. Such devices may be unreliable when
testing steels or metals with very low inclusion contents.
10.1 Metallographic specimen preparation must be carefully
controlled to produce acceptable quality surfaces for image
7.4 An automatic image analyzer with a camera of adequate
analysis. Guidelines and recommended practices are given in
sensitivity is employed to detect the inclusions, perform
Guides E3, E768, and Test Methods E45.
discrimination, and make measurements.
10.2 The polishing procedure must not
...
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