ASTM E45-18a(2023)

Standard Test Methods for Determining the Inclusion Content of Steel

SIGNIFICANCE AND USE
4.1 These test methods cover four macroscopic and five microscopic test methods (manual and image analysis) for describing the inclusion content of steel and procedures for expressing test results.  
4.2 Inclusions are characterized by size, shape, concentration, and distribution rather than chemical composition. Although compositions are not identified, Microscopic methods place inclusions into one of several composition-related categories (sulfides, oxides, and silicates—the last as a type of oxide). Paragraph 11.1.1 describes a metallographic technique to facilitate inclusion discrimination. Only those inclusions present at the test surface can be detected.  
4.3 The macroscopic test methods evaluate larger surface areas than microscopic test methods and because examination is visual or at low magnifications, these methods are best suited for detecting larger inclusions. Macroscopic methods are not suitable for detecting inclusions smaller than about 0.40 mm (1/64 in.) in length and the methods do not discriminate inclusions by type.  
4.4 The microscopic test methods are employed to characterize inclusions that form as a result of deoxidation or due to limited solubility in solid steel (indigenous inclusions). As stated in 1.1, these microscopic test methods rate inclusion severities and types based on morphological type, that is, by size, shape, concentration, and distribution, but not specifically by composition. These inclusions are characterized by morphological type, that is, by size, shape, concentration, and distribution, but not specifically by composition. The microscopic methods are not intended for assessing the content of exogenous inclusions (those from entrapped slag or refractories). In case of a dispute whether an inclusion is indigenous or exogenous, microanalytical techniques such as energy dispersive X-ray spectroscopy (EDS) may be used to aid in determining the nature of the inclusion. However, experience and knowledge of the casting proce...
SCOPE
1.1 These test methods cover a number of recognized procedures for determining the nonmetallic inclusion content of wrought steel. Macroscopic methods include macroetch, fracture, step-down, and magnetic particle tests. Microscopic methods include five generally accepted systems of examination. In these microscopic methods, inclusions are assigned to a category based on similarities in morphology, and not necessarily on their chemical identity. Metallographic techniques that allow simple differentiation between morphologically similar inclusions are briefly discussed. While the methods are primarily intended for rating inclusions, constituents such as carbides, nitrides, carbonitrides, borides, and intermetallic phases may be rated using some of the microscopic methods. In some cases, alloys other than steels may be rated using one or more of these methods; the methods will be described in terms of their use on steels.  
1.2 These test methods cover procedures to perform JK-type inclusion ratings using automatic image analysis in accordance with microscopic methods A and D.  
1.3 Depending on the type of steel and the properties required, either a macroscopic or a microscopic method for determining the inclusion content, or combinations of the two methods, may be found most satisfactory.  
1.4 These test methods deal only with recommended test methods and nothing in them should be construed as defining or establishing limits of acceptability for any grade of steel.  
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.6 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...

General Information

• Status: Published
• Publication Date: 31-Oct-2023
• ICS: 77.040.99 - Other methods of testing of metals
• Technical Committee: E04 - Metallography
• Drafting Committee: E04.09 - Inclusions

Relations

• Replaces: ASTM E45-18a - Standard Test Methods for Determining the Inclusion Content of Steel
• Effective Date: 01-Nov-2023
• Referred By: ASTM D8316-20a - Standard Test Method for Measuring Friction and Wear Properties of Extreme Pressure (EP) Lubricating Oils with the Roller-Disk Geometry Using SRV Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM A681-08(2022) - Standard Specification for Tool Steels Alloy
• Effective Date: 01-Nov-2023
• Referred By: ASTM E7-22 - Standard Terminology Relating to Metallography
• Effective Date: 01-Nov-2023
• Referred By: ASTM D8503-23 - Standard Test Method for Determining the Scuffing Temperature Limit of Lubricating Oils Using the SRV Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM F1314-18 - Standard Specification for Wrought Nitrogen Strengthened 22 Chromium–13 Nickel–5 Manganese–2.5 Molybdenum Stainless Steel Alloy Bar and Wire for Surgical Implants (UNS S20910)
• Effective Date: 01-Nov-2023
• Referred By: ASTM E2142-08(2023) - Standard Test Methods for Rating and Classifying Inclusions in Steel Using the Scanning Electron Microscope
• Effective Date: 01-Nov-2023
• Referred By: ASTM D7217-22 - Standard Test Method for Determining Extreme Pressure Properties of Solid Bonded Films Using a High-Frequency, Linear-Oscillation (SRV) Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM D7421-19 - Standard Test Method for Determining Extreme Pressure Properties of Lubricating Oils Using High-Frequency, Linear-Oscillation (SRV) Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM E2283-08(2019) - Standard Practice for Extreme Value Analysis of Nonmetallic Inclusions in Steel and Other Microstructural Features
• Effective Date: 01-Nov-2023
• Referred By: ASTM F1586-21 - Standard Specification for Wrought Nitrogen Strengthened 21Chromium-10Nickel-3Manganese-2.5Molybdenum Stainless Steel Alloy Bar for Surgical Implants (UNS S31675)
• Effective Date: 01-Nov-2023
• Referred By: ASTM F2332-06(2022) - Standard Specification for Annular Ball Bearings for Instruments and Precision Rotating Components
• Effective Date: 01-Nov-2023
• Referred By: ASTM F561-19 - Standard Practice for Retrieval and Analysis of Medical Devices, and Associated Tissues and Fluids
• Effective Date: 01-Nov-2023
• Referred By: ASTM C1187-20a - Standard Guide for Establishing Surveillance Test Program for Boron-based Neutron Absorbing Material Systems for Use in Nuclear Fuel Storage Racks in Pool Environment
• Effective Date: 01-Nov-2023
• Referred By: ASTM E235/E235M-23 - Standard Specification for Type K and Type N Mineral-Insulated, Metal-Sheathed Thermocouples for Nuclear or for Other High-Reliability Applications
• Effective Date: 01-Nov-2023

Overview

ASTM E45-18a(2023) - Standard Test Methods for Determining the Inclusion Content of Steel provides internationally recognized procedures for evaluating nonmetallic inclusions in wrought steel. Developed by ASTM, this standard details both macroscopic and microscopic test methods for characterizing inclusion populations by size, shape, concentration, and distribution. While the standard focuses primarily on inclusion morphology rather than chemical composition, it also touches on procedures for using automatic image analysis and outlines best practices for expressing test results. These methods ensure consistency and accuracy in determining steel cleanliness, which is a crucial factor in steel's performance for critical industrial applications.

Key Topics

• Macroscopic Methods

  • Macroetch, fracture, step-down, and magnetic particle tests allow examination of large surface areas at low magnification.
  • Macroscopic methods best detect larger inclusions (over 0.40 mm in length) and are not suitable for fine inclusions or discriminating inclusion types.

• Microscopic Methods

  • Five widely accepted systems are included, some employing manual rating and others using automatic image analysis.
  • Inclusions are categorized primarily by size, shape, concentration, and distribution, not by chemical identity.
  • Typical classification covers sulfides, oxides, silicates, and globular oxides.

• Inclusion Characterization

  • Methods rate inclusion severity based on morphological characteristics.
  • Reference charts and rating fields standardize the comparison and reporting of inclusion content.

• Sampling and Preparation

  • Proper statistical sampling and specimen preparation are necessary for representative and accurate results.
  • Recommendations are provided for specimen geometry and surface preparation.

• Significance and Use

  • Test results may help qualify steel for shipment or production quality control but do not specify acceptability limits for steel grades.
  • Both macroscopic and microscopic methods may be combined or selected based on specific steel properties and application requirements.

Applications

The ASTM E45-18a(2023) standard impacts numerous sectors where steel inclusions can affect performance and reliability, such as:

• Quality Control in Steel Production
  Routine rating of inclusion content is vital for steel manufacturers, ensuring product quality and compliance with customer requirements.

• Automotive and Aerospace Industries
  These industries require ultra-clean steels for structural components and safety-critical parts. Inclusion rating informs material selection and certification.

• Material Research and Development
  Metallurgists and materials scientists use these methods to understand steel behavior, refine production processes, or develop new alloys.

• Purchaser and Supplier Agreements
  Detailed inclusion ratings underpin technical contracts, facilitating mutual understanding and transparency between manufacturers and buyers.

Related Standards

To aid in specimen preparation, evaluation, and broader application, several related standards are referenced in ASTM E45-18a(2023):

• ASTM E3: Guide for Preparation of Metallographic Specimens
• ASTM E7: Terminology Relating to Metallography
• ASTM E381: Method of Macroetch Testing Steel Bars, Billets, Blooms, and Forgings
• ASTM E709: Guide for Magnetic Particle Testing
• ASTM E768: Guide for Preparing and Evaluating Specimens for Automatic Inclusion Assessment
• ASTM E1245: Practice for Determining Inclusion Content by Automatic Image Analysis
• ASTM E1444/E1444M: Practice for Magnetic Particle Testing for Aerospace
• ASTM E1951: Guide for Calibrating Reticles and Light Microscope Magnifications
• SAE J422: Recommended Practice for Determination of Inclusions in Steel
• ISO 3763/ISO 4967: International standards for inclusion rating methods.

Practical Value

Implementing ASTM E45-18a(2023) ensures consistent, objective evaluation of steel inclusion content, directly impacting steel cleanliness assurance. Accurate detection and classification of nonmetallic inclusions contribute to improved steel performance, reduced product failures, and heightened confidence in critical applications. For producers, adherence to this standard enhances competitiveness and global market access, while users benefit from reliable, high-quality steel products.

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: E45 − 18a (Reapproved 2023)
Standard Test Methods for
Determining the Inclusion Content of Steel
This standard is issued under the fixed designation E45; 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 1.7 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 These test methods cover a number of recognized
ization established in the Decision on Principles for the
procedures for determining the nonmetallic inclusion content
Development of International Standards, Guides and Recom-
of wrought steel. Macroscopic methods include macroetch,
mendations issued by the World Trade Organization Technical
fracture, step-down, and magnetic particle tests. Microscopic
Barriers to Trade (TBT) Committee.
methods include five generally accepted systems of examina-
tion. In these microscopic methods, inclusions are assigned to
2. Referenced Documents
a category based on similarities in morphology, and not
2.1 ASTM Standards:
necessarily on their chemical identity. Metallographic tech-
E3 Guide for Preparation of Metallographic Specimens
niques that allow simple differentiation between morphologi-
E7 Terminology Relating to Metallography
cally similar inclusions are briefly discussed. While the meth-
E381 Method of Macroetch Testing Steel Bars, Billets,
ods are primarily intended for rating inclusions, constituents
Blooms, and Forgings
such as carbides, nitrides, carbonitrides, borides, and interme-
E709 Guide for Magnetic Particle Testing
tallic phases may be rated using some of the microscopic
E768 Guide for Preparing and Evaluating Specimens for
methods. In some cases, alloys other than steels may be rated
Automatic Inclusion Assessment of Steel
using one or more of these methods; the methods will be
E1245 Practice for Determining the Inclusion or Second-
described in terms of their use on steels.
Phase Constituent Content of Metals by Automatic Image
1.2 These test methods cover procedures to perform JK-type
Analysis
inclusion ratings using automatic image analysis in accordance
E1444/E1444M Practice for Magnetic Particle Testing for
with microscopic methods A and D.
Aerospace
1.3 Depending on the type of steel and the properties
E1951 Guide for Calibrating Reticles and Light Microscope
required, either a macroscopic or a microscopic method for
Magnifications
determining the inclusion content, or combinations of the two
2.2 SAE Standards:
methods, may be found most satisfactory.
J422, Recommended Practice for Determination of Inclu-
sions in Steel
1.4 These test methods deal only with recommended test
methods and nothing in them should be construed as defining 2.3 Aerospace Material Specifications:
or establishing limits of acceptability for any grade of steel. AMS 2300, Premium Aircraft-Quality Steel Cleanliness:
Magnetic Particle Inspection Procedure
1.5 The values stated in SI units are to be regarded as
AMS 2301, Aircraft Quality Steel Cleanliness: Magnetic
standard. The values given in parentheses after SI units are
Particle Inspection Procedure
provided for information only and are not considered standard.
AMS 2303, Aircraft Quality Steel Cleanliness: Martensitic
1.6 This standard does not purport to address all of the
Corrosion-Resistant Steels Magnetic Particle Inspection
safety concerns, if any, associated with its use. It is the
Procedure
responsibility of the user of this standard to establish appro-
AMS 2304, Special Aircraft-Quality Steel Cleanliness: Mag-
priate safety, health, and environmental practices and deter-
netic Particle Inspection Procedure
mine the applicability of regulatory limitations prior to use.
1 2
These test methods are under the jurisdiction of ASTM Committee E04 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Metallography and is the direct responsibility of Subcommittee E04.09 on Inclu- contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
sions. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2023. Published November 2023. Originally the ASTM website.
approved in 1942. Last previous edition approved in 2018 as E45 –18a. DOI: Available from SAE International (SAE), 400 Commonwealth Dr., Warrendale,
10.1520/E0045-18AR23. PA 15096-0001, http://www.sae.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E45 − 18a (2023)
2.4 ISO Standards: 4. Significance and Use
ISO 3763, Wrought Steels—Macroscopic Methods for As-
4.1 These test methods cover four macroscopic and five
sessing the Content of Nonmetallic Inclusions
microscopic test methods (manual and image analysis) for
ISO 4967, Steel—Determination of Content of Nonmetallic
describing the inclusion content of steel and procedures for
Inclusions—Micrographic Methods Using Standard Dia-
expressing test results.
grams
4.2 Inclusions are characterized by size, shape,
2.5 ASTM Adjuncts:
5 concentration, and distribution rather than chemical composi-
Inclusions in Steel Plates I-A and II
tion. Although compositions are not identified, Microscopic
Four Photomicrographs of Low Carbon Steel
methods place inclusions into one of several composition-
related categories (sulfides, oxides, and silicates—the last as a
3. Terminology
type of oxide). Paragraph 11.1.1 describes a metallographic
3.1 Definitions:
technique to facilitate inclusion discrimination. Only those
3.1.1 For definitions of terms used in these test methods, see
inclusions present at the test surface can be detected.
Terminology E7.
4.3 The macroscopic test methods evaluate larger surface
3.1.2 Terminology E7 includes the term inclusion count;
areas than microscopic test methods and because examination
since some methods of these test methods involve length
is visual or at low magnifications, these methods are best suited
measurements or conversions to numerical representations of
for detecting larger inclusions. Macroscopic methods are not
lengths or counts, or both, the term inclusion rating is
suitable for detecting inclusions smaller than about 0.40 mm
preferred.
( ⁄64 in.) in length and the methods do not discriminate
3.2 Definitions of Terms Specific to This Standard:
inclusions by type.
3.2.1 aspect ratio—the length-to-width ratio of a micro-
structural feature.
4.4 The microscopic test methods are employed to charac-
terize inclusions that form as a result of deoxidation or due to
3.2.2 discontinuous stringer—three or more Type B or C
limited solubility in solid steel (indigenous inclusions). As
inclusions aligned in a plane parallel to the hot working axis
stated in 1.1, these microscopic test methods rate inclusion
and offset by no more than 15 μm, with a separation of less than
severities and types based on morphological type, that is, by
40 μm (0.0016 in.) between any two nearest neighbor inclu-
size, shape, concentration, and distribution, but not specifically
sions.
by composition. These inclusions are characterized by morpho-
3.2.3 inclusion types—for definitions of sulfide-, alumina-,
logical type, that is, by size, shape, concentration, and
and silicate-type inclusions, see Terminology E7. Globular
distribution, but not specifically by composition. The micro-
oxide, in some methods refers to isolated, relatively nonde-
scopic methods are not intended for assessing the content of
formed inclusions with an aspect ratio not in excess of 2:1. In
exogenous inclusions (those from entrapped slag or refracto-
other methods, oxides are divided into deformable and nonde-
ries). In case of a dispute whether an inclusion is indigenous or
formable types.
exogenous, microanalytical techniques such as energy disper-
3.2.4 JK inclusion rating—a method of measuring nonme-
sive X-ray spectroscopy (EDS) may be used to aid in deter-
tallic inclusions based on the Swedish Jernkontoret procedures;
mining the nature of the inclusion. However, experience and
Methods A and D of these test methods are the principal JK
knowledge of the casting process and production materials,
rating methods, and Method E also uses the JK rating charts.
such as deoxidation, desulfurization, and inclusion shape
3.2.5 stringer—an individual inclusion that is highly elon- control additives as well as refractory and furnace liner
compositions must be employed with the microanalytical
gated in the deformation direction or three or more Type B or
C inclusions aligned in a plane parallel to the hot working axis results to determine if an inclusion is indigenous or exogenous
and offset by no more than 15 μm, with a separation of less than
4.5 Because the inclusion population within a given lot of
40 μm (0.0016 in.) between any two nearest neighbor inclu-
steel varies with position, the lot must be statistically sampled
sions.
in order to assess its inclusion content. The degree of sampling
3.2.6 threshold setting—isolation of a range of gray level
must be adequate for the lot size and its specific characteristics.
values exhibited by one constituent in the microscope field.
Materials with very low inclusion contents may be more
accurately rated by automatic image analysis, which permits
3.2.7 worst-field rating—a rating in which the specimen is
more precise microscopic ratings.
rated for each type of inclusion by assigning the value for the
highest severity rating observed of that inclusion type any-
4.6 Results of macroscopic and microscopic test methods
where on the specimen surface.
may be used to qualify material for shipment, but these test
methods do not provide guidelines for acceptance or rejection
purposes. Qualification criteria for assessing the data devel-
oped by these methods can be found in ASTM product
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org.
standards or may be described by purchaser-producer agree-
Available from ASTM International Headquarters. Order Adjunct No.
ments. By agreements between producer and purchaser, these
ADJE004502A. Original adjunct produced in 1983. Adjunct revised in 2011.
test methods may be modified to count only certain inclusion
Available from ASTM International Headquarters. Order Adjunct No.
ADJE004501. Original adjunct produced in 1983. types and thicknesses, or only those inclusions above a certain
E45 − 18a (2023)
severity level, or both. Also, by agreement, qualitative prac- method for fracture surface inclusion ratings. In some
tices may be used where only the highest severity ratings for instances, indications as small as 0.40 mm ( ⁄64 in.) in length
are recorded.
each inclusion type and thickness are defined or the number of
fields containing these highest severity ratings are tabulated. 5.1.3 Step-Down Method—The step-down test method is
used to determine the presence of inclusions on machined
4.7 These test methods are intended for use on wrought
surfaces of rolled or forged steel. The test sample is machined
metallic structures. While a minimum level of deformation is
to specified diameters below the surface and surveyed for
not specified, the test methods are not suitable for use on cast
inclusions under good illumination with the unaided eye or
structures or on lightly worked structures.
with low magnification. In some instances, test samples are
machined to smaller diameters for further examination after the
4.8 Guidelines are provided to rate inclusions in steels
original diameters are inspected. This test is essentially used to
treated with rare earth additions or calcium-bearing com-
determine the presence of inclusions 3 mm ( ⁄8 in.) in length
pounds. When such steels are evaluated, the test report should
and longer.
describe the nature of the inclusions rated according to each
5.1.4 Magnetic Particle Method—The magnetic particle
inclusion category (A, B, C, D).
method is a variation of the step-down method for ferromag-
4.9 In addition to the Test Methods E45 JK ratings, basic
netic materials in which the test sample is machined,
(such as used in Practice E1245) stereological measurements
magnetized, and magnetic powder is applied. Discontinuities
(for example, the volume fraction of sulfides and oxides, the
as small as 0.40 mm ( ⁄64 in.) in length create magnetic leakage
number of sulfides or oxides per square millimeter, the spacing
fields that attract the magnetic powder, thereby outlining the
between inclusions, and so forth) may be separately deter-
inclusion. See Practice E1444/E1444M and Guide E709 on
mined and added to the test report, if desired for additional
magnetic particle examinations for more details of the proce-
information. This practice, however, does not address the
dure. Refer to Aerospace Materials Specifications AMS 2300,
measurement of such parameters.
AMS 2301, AMS 2303, and AMS 2304.
5.2 Advantages:
MACROSCOPIC METHODS
5.2.1 These test methods facilitate the examination of speci-
mens with large surface areas. The larger inclusions in steel,
5. Macroscopical Test Methods Overview which are the main concern in most cases, are not uniformly
distributed and the spaces between them are relatively large, so
5.1 Summary:
that the chances of revealing them are better when larger
5.1.1 Macro-etch Test—The macro-etch test is used to
specimens are examined.
indicate inclusion content and distribution, usually in the cross
5.2.2 Specimens for macroscopic examination may be
section or transverse to the direction of rolling or forging. In
quickly prepared by machining and grinding. A highly polished
some instances, longitudinal sections are also examined. Tests
surface is not necessary. The macroscopic methods are suffi-
are prepared by cutting and machining a section through the
ciently sensitive to reveal the larger inclusions.
desired area and etching with a suitable reagent. A solution of
5.3 Disadvantages:
one part hydrochloric acid and one part water at a temperature
5.3.1 These test methods do not distinguish among the
of 71 °C to 82 °C (160 °F to 180°F) is widely used. As the
different inclusion shapes.
name of this test implies, the etched surface is examined
5.3.2 They are not suitable for the detection of small
visually or at low magnification for inclusions. Details of this
globular inclusions or of chains of very fine elongated inclu-
test are included in Method E381. The nature of questionable
sions.
indications should be verified by microscopic examination or
5.3.3 The magnetic particle method can lead to incorrect
other means of inspection.
interpretation of microstructural features such as streaks of
5.1.1.1 Sulfides are revealed as pits when the standard
retained austenite, microsegregation, or carbides in certain
etchant described in 5.1.1 is used.
alloys; this is particularly likely if high magnetization currents
5.1.1.2 Only large oxides are revealed by this test method.
are employed.
5.1.2 Fracture Test—The fracture test is used to determine
the presence and location of inclusions as shown on the
MICROSCOPIC METHODS
fracture of hardened slices approximately 9 mm to 13 mm
3 1
( ⁄8 in. to ⁄2 in.) thick. This test is used mostly for steels where
6. Microscopic Test Methods Overview
it is possible to obtain a hardness of approximately 60 HRC
and a fracture grain size of 7 or finer. Test specimens should not
6.1 Microscopic methods are used to characterize the size,
have excessive external indentations or notches that guide the distribution, number, and type of inclusions on a polished
fracture. It is desirable that fracture be in the longitudinal
specimen surface. This may be done by examining the speci-
direction approximately across the center of the slice. The men with a light microscope and reporting the types of
fractured surfaces are examined visually and at magnifications
inclusions encountered, accompanied by a few representative
up to approximately ten diameters, and the length and distri- photomicrographs. This method, however, does not lend itself
bution of inclusions is noted. Heat tinting, or blueing, will
to a uniform reporting style. Therefore, standard reference
increase visibility of oxide stringers. ISO 3763 provides a chart charts depicting a series of typical inclusion configurations
E45 − 18a (2023)
(size, type, and number) were created for direct comparison even in different portions of the same ingot. It is essential that
with the microscopic field of view. A method using image the unit lot of steel, the inclusion content of which is to be
analysis to make these comparisons has also been developed.
determined, shall not be larger than one heat. Sufficient
samples should be selected to represent the lot adequately. The
6.2 Various reference charts of this nature have been de-
exact sampling procedure should be incorporated in the indi-
vised such as the JK chart and the SAE chart found in SAE
vidual product requirements or specifications. For semifinished
Recommended Practice J422 of the SAE Handbook. The
products, the specimens should be selected after the material
microscopic methods in Test Methods E45 use refined com-
has been sufficiently cropped and suitable discards made. If the
parison charts based on these charts. Method A (Worst Fields),
locations of the different ingots and portions of ingots in the
Method D (Low Inclusion Content) and Method E (SAM
heat cannot be identified in the lot being tested, random
Rating) use charts based on the JK chart while Method C
sampling should involve a greater number of test specimens for
(Oxides and Silicates) uses the SAE chart. ISO Standard 4967
an equivalent weight of steel. A value for the inclusion content
also uses the JK chart.
of an isolated piece of steel, even if accurately determined,
6.3 No chart can represent all of the various types and forms
should not be expected to represent the inclusion content of the
of inclusions. The use of any chart is thus limited to determin-
whole heat.
ing the content of the most common types of inclusions, and it
must be kept in mind that such a determination is not a
6.9 The size and shape of the wrought steel product tested
complete metallographic study of inclusions.
has a marked influence on the size and shape of the inclusions.
During reduction from the cast shape by rolling or forging, the
6.4 An alternate to comparison (chart) methods such as
inclusions are elongated and broken up according to the degree
Methods A, C and D may be found in Method B. Method B
of reduction of the steel cross section. In reporting results of
(Length) is used to determine inclusion content based on
inclusion determinations, therefore, the size, shape, and
length. Only inclusions 0.127 mm (0.005 in.) or longer are
method of manufacture of the steel from which the specimens
recorded regardless of their type. From this method one may
were cut must be stated. In comparing the inclusion content of
obtain data such as length of the longest inclusion and average
different steels, they must all be rolled or forged as nearly as
inclusion length. In addition, photomicrographs may also be
possible to the same size and shape, and from cast sections of
taken to characterize the background inclusions that were not
about the same size. Specimens cut lengthwise or parallel to
long enough to measure.
the direction of rolling or forging shall be used.
6.5 The advantages of the microscopic methods are:
6.5.1 Inclusions can be characterized as to their size, type,
6.10 It may be convenient, in order to obtain more readily
and number.
comparable results, to forge coupons from larger billets. These
6.5.2 Extremely small inclusions can be revealed.
forged sections may then be sampled in the same way as rolled
sections. Exercise care, however, to crop specimens of suffi-
6.6 A disadvantage of the microscopic methods is that
cient length from the billets for forging; otherwise, there is
individual rating fields are very small (0.50 mm ). This limits
danger of the shear-dragged ends being incorporated in the
the practical size of the specimen, as it would simply take a
specimens. Such distorted material will give a false result in
prohibitive number of fields to characterize a large specimen.
the inclusion determination. To avoid this, it is helpful to saw
The result obtained by a microscopic characterization of the
the ends of the billet length for forging and to take the
inclusions in a large section is governed by chance if local
specimen from the middle of the forged length.
variations in the inclusion distribution are substantial. The end
use of the product determines the importance of the micro-
6.11 Several of the methods described in these test methods
scopic results. Experience in interpreting these results is
require that a specific area of the prepared surface of the
necessary in order not to exaggerate the importance of small
specimen is surveyed, and all the significant inclusions ob-
inclusions in some applications.
served be recorded and expressed in the results. The reported
6.7 In determining the inclusion content, it is important to
result for each specimen examined is, therefore, a more
realize that, whatever method is used, the result actually
accurate representation of the inclusion content than a photo-
applies only to the areas of the specimens that were examined.
micrograph or diagram. A disadvantage of the Worst Field
For practical reasons, such specimens are relatively small
approach is that no such distribution of inclusion ratings is
compared with the total amount of steel represented by them.
obtained.
For the inclusion determination to have any value, adequate
6.12 To make comparisons possible between different heats
sampling is just as necessary as a proper method of testing.
and different parts of heats, the results shall be expressed in
6.8 Steel often differs in inclusion content not only from
such a manner that an average for the inclusion content of the
heat to heat, but also from ingot to ingot in the same heat and
different specimens in the heat can be obtained. When the
lengths of the inclusions are measured, the simplest number is
that for the aggregate length of all the inclusions per area
The JK chart derives its name from its sponsors Jernkontoret, the Swedish
examined; however, it may be desirable not merely to add the
Ironmasters Association.
lengths but also to weight the inclusions according to their
Note that while these methods are called comparison chart methods, the
individual lengths. The length of the largest inclusion found
procedure used may also consist of length measurements or counts of inclusions, or
both. and the total number of inclusions may also be expressed.
E45 − 18a (2023)
7. Sampling
7.1 To obtain a reasonable estimate of inclusion variations
within a lot, at least six locations, chosen to be as representa-
tive of the lot as possible, should be examined. In this context,
a lot shall be defined as a unit of material processed at one time
and subjected to similar processing variables. In no case should
more than one heat be in the same lot. For example if a lot
consists of one heat, sampling locations might be in the product
obtained from the top and bottom of the first, middle, and last
usable ingots in the pouring sequence. For strand cast or
NOTE 1—Method also applicable to square sections.
bottom pour processing, a similar sampling plan per heat
NOTE 2—a denotes distance equal to surface removal.
should be invoked.
FIG. 2 Quarter Section Specimen from Round Section for Mag-
netic Particle Test, Forging and Machining
7.2 For cases in which a definite location within a heat,
ingot, or other unit lot is unknown, statistical random sampling
with a greater number of specimens should be employed.
8.2.1 For wide products, the one-quarter point along the
7.3 Ratings obtained will vary with the amount of reduction
product width is commonly used to provide representative
of the product. For materials acceptance or for comparison
material.
among heats, care must be taken to sample at the correct stage
8.2.2 For round sections, the manner of cutting a specimen
of processing.
from a 38 mm (1.5-in.) diameter section is shown in Fig. 3. A
disk at least 12 mm (0.474 in.) thick is cut from the product.
8. Test Specimen Geometry
The quarter-section indicated in Fig. 3 is cut from the disk and
8.1 The minimum polished surface area of a specimen for
the shaded area is polished. Thus the specimen extends at least
the microscopic determination of inclusion content is 160
12 mm along the length of the product from the outside to the
2 2
mm (0.25 in. ). It is recommended that a significantly large
center.
area should be obtained so that the measurements may be made
8.2.3 For large sections, each specimen shall be taken from
within the defined area away from the edges of the sample. The
the mid-radius location, as shown by the shaded area in Fig. 4.
polished surface must be parallel to the longitudinal axis of the
The specimen face to be polished extends at least 12 mm
product. In addition, for flat-rolled products, the section shall
parallel to the longitudinal axis of the billet and at least 19 mm
also be perpendicular to the rolling plane; for rounds and
(0.75 in.) in the longitudinal radial plane, with the polished
tubular shapes, the section shall be in the radial direction. In all
face midway between the center and the outside of the billet.
cases, the polished surface shall be parallel to the hot-working
Such midway sampling is used to decrease the number of
axis. Studies have demonstrated that inclusion length measure-
specimens polished and examined. Other areas, such as the
ments are significantly affected if the plane of polish is angled
center and the surface, may be examined as well, provided the
more than 6° from the longitudinal hot-working direction.
sampling procedure used is stated in the results. A billet or bar
8.1.1 Sections less than 0.71 mm in thickness shall not be
about 50 mm to 100 mm (2 in. to 4 in.) round or square is the
analyzed using Test Methods E45.
preferred size from which specimens should be taken;
however, larger or smaller sizes may be used, provided the
8.2 Thick Section (Product Section Size Greater than 9.5
product sizes are reported with the results.
mm (0.375 in.) Thick, Such as Forgings, Billet, Bar, Slab,
Plate, and Pipe):
8.3 Thin Sections (Product Section Sizes 9.5 mm (0.375 in.)
Thick or Less; Strip, Sheet, Rod, Wire, and Tubing)—Full cross
section longitudinal specimens shall be cut in accordance with
Allmand, T. R., and Coleman, D. S., “The Effect of Sectioning Errors on
the following plan:
Microscopic Determinations of Non-Metallic Inclusions in Steels,” Metals and
Materials, Vol 7, 1973, pp. 280–283.
NOTE 1—This method is also applicable to round sections.
NOTE 2—a denotes surface removal. NOTE 1—Inch-pound equivalents: 12 mm = 0.47 in.; 19 mm = 0.75 in.
FIG. 1 Quarter Section Specimen from Square Section for Mag- FIG. 3 Specimen from 1 ⁄2-in. (38.1 mm) Round Section for Micro-
netic Particle Test, Machine Only scopic Test
E45 − 18a (2023)
9.3 Inclusion retention is generally easier to accomplish in
hardened steel specimens than in the annealed condition. If
inclusion retention is inadequate in annealed specimens, they
should be subjected to a standard heat treatment cycle using a
relatively low tempering temperature. After heat treatment, the
specimen must be descaled and the longitudinal plane must be
reground below any decarburization. This recommendation
only applies to heat-treatable steel grades.
9.4 Mounting of specimens is not required if unmounted
specimens can be properly polished.
10. Calibration and Standardization
10.1 Recommended calibration guidelines can be found in
Guide E1951.
10.2 For image analysis, a stage micrometer and a ruler,
both calibrated against devices traceable to a recognized
FIG. 4 Specimen from Large Bar or Billet for Microscopic Test
national standards laboratory, such as the National Institute for
Standards and Technology (NIST), are used to determine the
magnification of the system and calibrate the system in
8.3.1 For 0.95 mm to 9.5 mm (0.0375 in. to 0.375 in.) cross
accordance with the manufacturer’s recommended procedure.
section thicknesses inclusively, a sufficient number of pieces
For example, the ruler is superimposed over the magnified
from the same sampling point are mounted to provide approxi-
image of the stage micrometer on the monitor. The apparent
2 2
mately 160 mm (0.25 in. ) of polished specimen surface.
(magnified) distance between two known points on the stage
(Example: For a sheet 1.27 mm (0.050 in.) thick, select seven
micrometer is measured with the ruler. The magnified distance
or eight longitudinal pieces uniformly across the sheet width to
is divided by the true distance to determine the screen
provide one specimen).
magnification. The pixel dimensions can be determined from
8.3.2 For cross section thicknesses less than 0.95 mm, ten
the number of pixels for a known horizontal or vertical
longitudinal pieces from each sampling location shall be
dimension on the monitor. Divide the known length of a scale
mounted to provide a suitable specimen surface for polishing.
or mask by the number of pixels representing that length on the
(Dependent on material thickness and piece length, the pol-
monitor to determine the pixel size for each possible screen
ished specimen area may be less than 160 mm . Because of
magnification. Not all systems use square pixels. Determine the
practical difficulties in mounting a group of more than ten
pixel dimensions in both horizontal and vertical orientations.
pieces, the reduced specimen area will be considered suffi-
Check the instruction manual to determine how corrections are
cient.) Note that when using the comparison procedures of
made for those systems that do not use square pixels.
Methods A, C, D and E, the thickness of the test specimen
10.2.1 Follow the manufacturer’s recommendations in ad-
cross section should not be less than the defined minimum
justing the microscope light source and setting the correct level
dimension of a single field of view. Therefore, the minimum
of illumination for the television video camera. For systems
thickness required is 0.71 mm for Methods A, D, and E, and
with 256 gray levels, the illumination is generally adjusted
0.79 mm for Method C. Thinner sections should be rated by
until the as-polished matrix surface is at level 254 and black is
other means.
at zero.
9. Preparation of Specimens
10.2.2 For modern image analyzers with 256 gray levels,
with the illumination set as described in 10.2.1, it is usually
9.1 Methods of specimen preparation must be such that a
polished, microscopically flat section is achieved in order that possible to determine the reflectance histogram of individual
inclusions as an aid in establishing proper threshold settings to
the sizes and shapes of inclusions are accurately shown. To
obtain satisfactory and consistent inclusion ratings, the speci- discriminate between oxides and sulfides. Oxides are darker
men must have a polished surface free of artifacts such as and usually exhibit gray levels below about 130 on the gray
pitting, foreign material (for example, polishing media), and
scale while the lighter sulfides generally exhibit values be-
scratches. When polishing the specimen it is very important
tween about 130 and 195. These numbers are not absolute and
that the inclusions not be pitted, dragged, or obscured. Speci-
will vary somewhat for different steels and different image
mens must be examined in the as-polished condition, free from
analyzers. After setting the threshold limits to discriminate
the effects of any prior etching (if used).
oxides and sulfides, use the flicker method of switching
back-and-forth between the live inclusion image and the
9.2 Metallographic specimen preparation must be carefully
detected (discriminated) image, over a number of test fields, to
controlled to produce acceptable quality surfaces for both
ensure that the settings are correct, that is, detection of sulfides
manual and image analysis. Guidelines and recommendations
are given in Practice E3, Test Methods E45, and Practice E768. or oxides by type and size is correct.
E45 − 18a (2023)
TABLE 1 Minimum Values for Severity Level Numbers
11. Classification of Inclusions and Calculation of
A,B
(Methods A, D, and E)
Severities
(mm (in.) at 100×, or count)
C
11.1 In these microscopic methods, inclusions are classified
Severity A B C D
0.5 3.7(0.15) 1.7(0.07) 1.8(0.07) 1
into four categories (called Type) based on their morphology
1.0 12.7(0.50) 7.7(0.30) 7.6(0.30) 4
and two subcategories based on their width or diameter.
1.5 26.1(1.03) 18.4(0.72) 17.6(0.69) 9
Categories A-Sulfide Type, B-Alumina Type, C-Silicate Type
2.0 43.6(1.72) 34.3(1.35) 32.0(1.26) 16
2.5 64.9(2.56) 55.5(2.19) 51.0(2.01) 25
and D-Globular Oxide Type define their shape while categories
3.0 89.8(3.54) 82.2(3.24) 74.6(2.94) 36
Heavy and Thin describe their thickness. Although the catego-
3.5 118.1(4.65) 114.7(4.52) 102.9(4.05) 49
ries contain chemical names that imply knowledge of their
4.0 149.8(5.90) 153.0(6.02) 135.9(5.35) 64
4.5 189.8(7.47) 197.3(7.77) 173.7(6.84) 81
chemical content, the ratings are based strictly on morphology.
5.0 223.0(8.78) 247.6(9.75) 216.3(8.52) 100
The chemical names associated with the various Types were
(μm (in.) at 1×, or count)
C
derived from historical data collected on inclusions found in Severity A B C D
0.5 37.0(.002) 17.2(.0007) 17.8(.0007) 1
these shapes or morphologies. The four categories, or Types,
1.0 127.0(.005) 76.8(.003) 75.6(.003) 4
are partitioned into Severity Levels based on the number or
1.5 261.0(.010) 184.2(.007) 176.0(.007) 9
length of the particles present in a 0.50 mm field of view. 2.0 436.1(.017) 342.7(.014) 320.5(.013) 16
2.5 649.0(.026) 554.7(.022) 510.3(.020) 25
These Severity Levels and inclusion Types are depicted in
3.0 898.0(.035) 822.2(.032) 746.1(.029) 36
Plate I-A and their numerical equivalents are found in Tables
3.5 1181.0(.047) 1147.0(.045) 1029.0 49
(.041)
1 and 2.
4.0 1498.0(.059) 1530.0(.060) 1359.0 64
11.1.1 Type A and C inclusions are very similar in size and
(.054)
shape. Therefore, discrimination between these Types is aided
4.5 1898.0(.075) 1973.0(.078) 1737.0 81
by metallographic techniques. Type A-Sulfide are light gray (.068)
5.0 2230.0(.088) 2476.0(.098) 2163.0 100
while Type C-Silicate are black when viewed under brightfield
(.085)
2 2 2
illumination. Discrimination between these types may also be
(mm/mm (in./in. ), or count/mm )
C
Severity A B C D
aided by viewing the questionable inclusions under darkfield or
0.5 0.074(1.88) 0.034(.864) 0.036(.914) 2
cross-polarized illumination where properly polished sulfide
1.0 0.254(6.45) 0.154(3.91) 0.152(3.86) 8
inclusions are dark and silicate inclusions appear luminescent.
1.5 0.522(3.64) 0.368(9.35) 0.352(8.94) 18
2.0 0.872(22.15) 0.686(17.32) 0.640 32
11.2 The B-type stringers consist of a number (at least three)
(16.26)
of round or angular oxide particles with aspect ratios less than 2.5 1.298(32.97) 1.110(28.19) 1.020 50
(25.91)
2 that are aligned nearly parallel to the deformation axis.
3.0 1.796(45.59) 1.644(41.76) 1.492 72
Particles within 615 μm of the centerline of a B-type stringer
(37.90)
are considered to be part of that stringer. The Type C-Silicate 3.5 2.362(59.99) 2.294(58.27) 2.058 98
(52.27)
stringers consist of one or more highly elongated oxides with
4.0 2.996(76.10) 3.060(77.72) 2.718 128
smooth surfaces aligned parallel to the deformation axis.
(69.04)
4.5 3.796(96.42) 3.946(100.2) 3.474 162
Aspect ratios are generally high, ≥ 2. The maximum permitted
(88.24)
separation between particles in a stringer is 40 μm. Any oxides
5.0 4.460(113.3) 4.952(125.8) 4.326 200
that have aspect ratios < 2, and are not part of a B- or C-type
(109.9)
stringer, are rated as D-types. No other shape restriction is
A
Note that length values in this table have been changed to be compatible with
applicable.
automated rating methods. The significant length changes occurred at minimum
rating levels of ⁄2 where manual methods are least accurate. Inclusion counts for
11.3 After the inclusions are categorized by Type, they must
Type D inclusions have also been revised. In this case, the changes are greatest
for high counts, which are above the levels of material acceptance standards.
be categorized by thickness or diameter. Inclusion width
B
VanderVoort, G. F., and Wilson, R. K., “Nonmetallic Inclusions and ASTM
parameters for classification into the Thin or Heavy category
Committee E04,” Standardization News, Vol 19, May 1991, pp 28–37.
C
are listed in Table 2. An inclusion whose width varies from
Maximum aspect ratio for Type D inclusions is < 2.
Thin to Heavy along its length shall be placed in the category
that best represents its whole. That is to say, if more of its
length falls into the Heavy range, classify it as Heavy. See 11.8
for instructions on reporting inclusions that exceed the limits of
(mm ), but the measurements must be made on contiguous
Table 1 or Table 2.
0.50 mm test areas. Severities are calculated based on the
11.4 Inclusions thinner than the 2 μm minimum listed in
limits given in Table 1. Note that these values are the minimum
Table 2 are not rated. That is, their lengths or numbers are not
length or number for each class. In general, severity values
included in the determination of Severity.
(calculated as described below) are rounded downward to the
11.5 After classification by type and thickness, the severity nearest half-severity level increment. For steels with particu-
levels are determined for the inclusions within 0.50 mm test larly low inclusion contents, severity values may be rounded
areas based upon the total Type A sulfide lengths per field, the down to the nearest quarter or tenth value, per agreement
total Type B or C stringer lengths per field, and the number of between producer and purchaser. However, because of the way
isolated D-type inclusions per field. These values can be D inclusion counts are defined (for 1 inclusion, the severity is
reported according to the length or number in each 0.50 mm 0.5 and for 0 inclusions, the severity is 0), there can be no
field or as the length per unit area or number per unit area subdivisions between 0 and 0.5 severities.
E45 − 18a (2023)
TABLE 2 Inclusion Width and Diameter Parameters
thin or thick. The antilog is determined and rounded downward
A
(Methods A and D)
to the nearest half-severity level increment.
Thin Series Heavy Series
Inclusion
11.7 Calculation of the severity numbers for D-type oxides
Width, min, Width, max, Width, min, Width, max,
Type
μm (in.) μm (in.) μm (in.) μm (in.)
is done in the same manner as for Types A, B, and C inclusions
A 2 (.00008) 4 (.00016) >4 (.00016) 12 (.0005)
except that the criterion is the number of oxides rather than
B 2 (.00008) 9 (.00035) >9 (.00035) 15 (.0006)
their length. Fig. 13 shows a log-log plot of the data in Table
C 2 (.00008) 5 (.0002) >5 (.0002) 12 (.0005)
D 2 (.00008) 8 (.0003) >8 (.0003) 13 (.0005)
1.
A
Any inclusion with maximum dimensions greater than the maximum for the
11.8 The fields shown in Plate I-A represent the total lengths
Heavy Series must be reported as oversized accompanied with its actual
dimensions.
of the A inclusions, the total stringer lengths of B and C
inclusions, the number of D inclusions, and their respective
limiting widths or diameters. If any inclusions are present that
11.6 Calculation of the severity number for Type A, B, and
are longer than the fields shown in Plate I-A, their lengths shall
C inclusions is based on a log-log plot of the data in Table 1 on
be recorded separately. If their widths or diameters are greater
Minimum Values for Inclusion Rating Numbers (Methods A
than the limiting values shown in Plate I-A and Table 2, they
and D). Such plots reveal a linear relationship between the
shall be recorded separately. Note that an oversize A, B, or C
severity numbers and the minimum total sulfide length (Type
inclusion or inclusion stringer still contributes to the determi-
A) and the minimum total stringer length (Types B & C) per
nation of a field’s Severity Level Number. Therefore, if an A,
0.50 mm field for each severity level as shown in Figs. 10-12.
B, or C inclusion is oversized either in length or thickness that
A least-square fit to the data in Table 1 has been used to
portion that is within the field boundaries shall be included in
produce the relationships in Table 6, which can be used to
the appropriate Thin or Heavy severity level measurement.
calculate the severity of Type A, B, and C inclusions, either
Likewise, if an oversize D inclusion is encountered in a field,
it is also included in the count that determines the D heavy
Vander Voort, G. F., and Golden, J. F., “Automating the JK Inclusion
rating. A Type D globular oxide may not exceed an aspect ratio
Analysis,” Microstructural Science, Vol 10, Elsevier Science Publishing Co., Inc.,
NY, 1982, pp. 277–290. of 2:1.
NOTE 1—The square mask will yield a field area of 0.50 mm on the specimen surface. A graphic representation of the maximum thickness of the Thin
and Heavy series of Types A, B, C, and D is on the left. Several oversized Type D are depicted on the right for convenience.
FIG. 5 Suggested Reticle or Overlay Grid For Methods A, D, and E
E45 − 18a (2023)
NOTE 1—Systematically scan the entire masked area. Methods A, B, C, and E permit adjustment of the field locations in order to maximize a severity
level number or facilitate a measurement. For Method D, the fields must remain contiguous and only features within the field are compared to Plate I-A.
NOTE 2—Method D will require a larger (10 mm × 17 mm) test area to facilitate placement of enough contiguous, 0.71 mm square fields to total 160
mm of polished surface area.
FIG. 6 Typical Scan Pattern for Microscopic Methods
composition must be provided to avoid confusion. Because
they are sulfides with a D-type morphology, they may be
referred to as D .
S
11.11 Complex inclusions, such as oxysulfides or duplex
inclusions, are also rated according to their morphology:
whether they are stringered or elongated (for aspect ratios ≥ 2)
or isolated (not part of a stringer and aspect ratio < 2); and then
by thickness. Isolated, globular particles are rated as D-types
by their average thickness. Complex D may be predominantly
s
(>50 % by area) sulfides or oxides and should be identified as
such. For example, if the oxide area is greater in a globular
oxysulfide, it could be called a D type. Stringered complex
OS
particles are rated by the aspect ratio of the individual particles;
if < 2, they are B-types, if ≥ 2 they are A- or C-types (separate
by gray level). For those complex inclusions with aspect ratios
≥ 2, they are classified as A-types if more than 50 % of the area
NOTE 1—One unit equals 0.127 mm (0.005 in.) on the specimen
surface.
is sulfide and C-types if more than 50 % of the area is oxide.
FIG. 7 Suggested Reticle or Overlay Grid for Method B
Report the composition, in general terms, to avoid confusion,
and state the nature of the inclusions, for example, “globular
calcium aluminates encapsulated with a thin film of calcium-
manganese sulfide,” or “irregular aluminates partially or fully
11.9 Oxides located at the tips of Type A-Sulfide inclusions
embedded in manganese sulfide stringers.”
are rated at Type D- Globular Oxides unless they are close
11.12 If producer-purchaser agreements limit the analysis to
enough together to meet the requirements of a Type
only certain inclusion types, thickness categories, or severity
B-Alumina.
limits, the scheme in Section 11 can be modified to analyze,
11.10 The indigenous inclusions in steels deoxidized with
measure, and store only the data of interest. It may also contain
rare earth elements or
...