ASTM D5061-19

Standard Test Method for Microscopical Determination of the Textural Components of Metallurgical Coke

SIGNIFICANCE AND USE
5.1 The determination of the volume percent of the textural components in coke is useful to characterize the optical properties of coke as it relates to utilization. Specifically, the technique has been used as an aid in determining coal blend proportions, and recognition of features present in the coke that can be responsible for coke quality or production problems such as reduced coke strength or difficulty in removing coke from commercial coke ovens, or both. The study of coke textures is also useful in promoting a better understanding of coke reactivity, and the relationship between coal petrography and its conversion to coke.5  
5.2 This test method is used in scientific and industrial research, but not for compliance or referee tests.
SCOPE
1.1 This test method covers the equipment and procedures used for determining the types and amounts of coke carbon forms and associated recognizable coal- and process-derived textural components in metallurgical coke in terms of volume percent. This test method does not include coke structural components such as coke pores, coke wall dimensions, or other structural associations.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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

• Status: Published
• Publication Date: 14-Mar-2019
• ICS: 77.020 - Production of metals
• Technical Committee: D05 - Coal and Coke
• Drafting Committee: D05.28 - Petrographic Analysis of Coal and Coke

Relations

• Replaces: ASTM D5061-16 - Standard Test Method for Microscopical Determination of the Textural Components of Metallurgical Coke
• Effective Date: 15-Mar-2019
• Refers: ASTM D121-15(2024) - Standard Terminology of Coal and Coke
• Effective Date: 01-Mar-2024
• Refers: ASTM D3997/D3997M-16 - Standard Practice for Preparing Coke Samples for Microscopical Analysis by Reflected Light
• Effective Date: 01-Oct-2016
• Refers: ASTM D121-15 - Standard Terminology of Coal and Coke
• Effective Date: 01-Sep-2015
• Refers: ASTM D121-09a - Standard Terminology of Coal and Coke
• Effective Date: 01-Oct-2009
• Refers: ASTM D3997/D3997M-97(2009) - Standard Practice for Preparing Coke Samples for Microscopical Analysis by Reflected Light
• Effective Date: 01-Sep-2009
• Refers: ASTM D121-09 - Standard Terminology of Coal and Coke
• Effective Date: 01-Feb-2009
• Refers: ASTM D121-08 - Standard Terminology of Coal and Coke
• Effective Date: 15-Feb-2008
• Refers: ASTM D121-07 - Standard Terminology of Coal and Coke
• Effective Date: 01-May-2007
• Refers: ASTM D121-05 - Standard Terminology of Coal and Coke
• Effective Date: 01-May-2005
• Refers: ASTM D121-04a - Standard Terminology of Coal and Coke
• Effective Date: 01-Oct-2004
• Refers: ASTM D121-04 - Standard Terminology of Coal and Coke
• Effective Date: 01-Jul-2004
• Refers: ASTM D121-01a - Standard Terminology of Coal and Coke
• Effective Date: 10-Nov-2001
• Referred By: ASTM D7448-16 - Standard Practice for Establishing the Competence of Laboratories Using ASTM Procedures in the Sampling and Analysis of Coal and Coke (Withdrawn 2024)
• Effective Date: 15-Mar-2019

Overview

ASTM D5061-19: Standard Test Method for Microscopical Determination of the Textural Components of Metallurgical Coke provides guidance on the equipment and procedures required to determine the volume percent of different textural components in metallurgical coke. This test method utilizes a microscopical approach to identify and quantify the various carbon forms and recognizable coal- or process-derived components within metallurgical coke. The results offer critical insights into the optical properties of coke, which are directly related to its performance and utilization, such as coke strength and reactivity.

Key Topics

• Textural Component Analysis: The standard categorizes the textural components of metallurgical coke into three major groups:

  • Binder phase carbon forms (various anisotropic and isotropic structures)
  • Filler phase carbon forms (organic and inorganic inerts, including coal-related minerals)
  • Miscellaneous materials (e.g., sooty, spherulitic, and pyrolytic carbons)

• Microscopical Identification: Using high-quality reflected-light microscopy, analysts observe and classify component types based on optical properties such as reflectance, anisotropy, color, and morphology.

• Volume Percent Determination: The method requires counting a statistically significant number of observation points across prepared samples to determine the volume percentages of each category.

• Precision and Repeatability: The method provides robust guidelines for repeatability and reproducibility, ensuring reliability in interlaboratory environments.

• Reporting Requirements: Results are reported as volume percent for each category, supporting targeted diagnostics for coke plant operational optimization.

Applications

The ASTM D5061-19 standard is applied in scientific and industrial research to:

• Coal Blend Optimization: Help in determining optimal coal blend proportions by understanding the relationship between coal petrography and coke optical textures.
• Coke Quality Assessment: Enable recognition of features that may affect coke strength or cause removal difficulties from commercial coke ovens.
• Problem Diagnosis: Identify process-related or raw material issues that impact coke production, such as abnormal structural phases or inerts.
• Understanding Coke Reactivity: Provide data supporting studies on the reactivity of coke and its behavior in metallurgical processes.
• Process Control and Product Development: Support research and process refinement, enhancing the predictability and quality of coke production.

This method is not intended for compliance or referee tests but serves as a valuable research and diagnostic tool for laboratories, metallurgical plants, and academic institutions involved in coke characterization.

Related Standards

• ASTM D121: Terminology of Coal and Coke
• ASTM D3997/D3997M: Practice for Preparing Coke Samples for Microscopical Analysis by Reflected Light
• ISO 5725-6: Accuracy (Trueness and Precision) of Measurement Methods and Results – Part 6: Use in Practice of Accuracy Values

Practical Value

By standardizing the microscopical determination of metallurgical coke textural components, ASTM D5061-19 helps improve consistency in product analysis and troubleshooting across laboratories. Its adoption enables informed decisions for raw material selection, process optimization, and quality assurance in coke production, contributing to efficient and reliable steelmaking and industrial applications. For those involved in the petrographic analysis of coal or working to enhance coke performance, this test method is an essential reference for robust and comparative analysis.

Keywords: metallurgical coke, coke textural components, carbon forms, coke microscopy, petrographic analysis, coke quality, ASTM D5061-19, coal blend, coke reactivity, coke production optimization

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: D5061 − 19
Standard Test Method for
Microscopical Determination of the Textural Components of
Metallurgical Coke
This standard is issued under the fixed designation D5061; 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 Practice of Accuracy Values
1.1 This test method covers the equipment and procedures
3. Terminology
used for determining the types and amounts of coke carbon
forms and associated recognizable coal- and process-derived
3.1 Definitions—For additional definitions of terms used in
textural components in metallurgical coke in terms of volume
this test method, refer to Terminology D121.
percent. This test method does not include coke structural
3.2 Definitions of Terms Specific to This Standard:
componentssuchascokepores,cokewalldimensions,orother
3.2.1 anisotropic, adj—exhibiting optical properties of dif-
structural associations.
ferent values when viewed with an optical microscope having
1.2 The values stated in SI units are to be regarded as
mutuallyexclusivepolarizedlight,forexample,crossednicols.
standard. No other units of measurement are included in this
3.2.2 binder phase, n—a continuous solid carbon matrix
standard.
formed during the thermoplastic deformation of those coal
1.3 This standard does not purport to address all of the
macerals that become plastic during carbonization.
safety concerns, if any, associated with its use. It is the
3.2.2.1 Discussion—The binder phase material is formed
responsibility of the user of this standard to establish appro-
from the thermoplastic deformation of reactive (vitrinite and
priate safety, health, and environmental practices and deter-
liptinite) and semi-inert (semifusinite) coal macerals of metal-
mine the applicability of regulatory limitations prior to use.
lurgical bituminous coals. During thermoplasticity, the inert
1.4 This international standard was developed in accor-
coalmaceralandmineralarepartlyorwhollyincorporatedinto
dance with internationally recognized principles on standard-
thebinderphase.Also,mostofthecokeporesarelocatedinthe
ization established in the Decision on Principles for the
binder phase.
Development of International Standards, Guides and Recom-
3.2.3 carbon form, n—microscopically distinguishable car-
mendations issued by the World Trade Organization Technical
bonaceous textural components of coke, but excluding mineral
Barriers to Trade (TBT) Committee.
carbonates.
2. Referenced Documents
3.2.3.1 Discussion—Carbon forms are recognized on the
basisoftheirreflectance,anisotropy,andmorphology.Theyare
2.1 ASTM Standards:
derived from the organic portion of coal and can be anisotropic
D121 Terminology of Coal and Coke
or isotropic.
D3997/D3997M Practice for Preparing Coke Samples for
Microscopical Analysis by Reflected Light
3.2.4 circularanisotropicphase,n—agroupofbinder-phase
2.2 ISO Standard:
anisotropic carbon textures that are distinguished by approxi-
ISO 5725-6: 1994 Accuracy (Trueness and Precision) of
mately circular domains (that is length equals width) and
Measurement Methods and Results – Part 6: Use in
composed of fine circular (0.5 µm to 1.0 µm), medium circular
(1.0 µm to 1.5 µm), and coarse circular (1.5 µm to 2.0 µm) size
This test method is under the jurisdiction of ASTM Committee D05 on Coal
categories.
and Coke and is the direct responsibility of Subcommittee D05.28 on Petrographic
3.2.5 coke pore, n—a microscopically distinguishable void
Analysis of Coal and Coke.
Current edition approved March 15, 2019. Published June 2019. Originally
that is a structural element of coke.
approved in 1992. Last previous edition approved in 2016 as D5061 – 16. DOI:
3.2.5.1 Discussion—Coke pores are considered to be nearly
10.1520/D5061-19.
spherical-shaped voids created by the entrapment of gaseous
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
volatiles during the solidification of thermoplastic coal.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
However,othertypesofvoidscanbedistinguishedincokethat
the ASTM website.
include fractures or cracks, interconnected and elongated
Available from International Organization for Standardization (ISO), ISO
pores, and the open cell lumens of fusinite and semifusinite.
Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
Geneva, Switzerland, http://www.iso.org. The size and shape of the voids are coal rank and grade, and to
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5061 − 19
some degree, process dependent. Pore sizes vary from tens of 3.2.15 ribbon anisotropic phase, n—agroupofbinder-phase
angstroms to tens of millimetres in any given coke. anisotropic carbon textures distinguished by their ribbon-like
domains (that is, length (L) to width (W) ratio of L>4W), and
3.2.6 coke reactivity, n—a measure of the mass loss when
subdivided based on domain width as fine ribbon (2.0 µm to
coke, held at a designated temperature, is contacted with
12.0 µm), medium ribbon (12.0 µm to 25.0 µm), and coarse
gaseous carbon dioxide over a specific time interval.
ribbon (> 25.0 µm) size categories.
3.2.7 coke wall, n—apredominantlycarbonaceouslayerthat
3.2.16 textural component, n—the collective term used to
encloses a coke pore and which is a structural element and
describe carbon forms and recognizable coal- and process-
essence of coke.
derived components (binder-phase, filler-phase, and miscella-
3.2.8 depositional carbon, n—a group of carbon forms that
neous material) in coke.
are formed from cracking and nucleation of gas-phase hydro-
3.2.17 vitrinite type, n—reflectance classes of vitrinite
carbon molecules during coal carbonization.
which span 0.1 % reflectance intervals.
3.2.8.1 pyrolytic carbon, n—an anisotropic carbon form that
3.2.17.1 Discussion—This term is commonly referred to as
is formed by the deposition of carbon parallel to an inert
V-Type. For example, V-type 6 includes vitrinite reflectance
substrate causing the resulting texture to appear ribbon-like.
values from 0.6 % through 0.69 %.
3.2.8.2 sooty carbon, n—an isotropic carbon form com-
prised of approximately spherical particles of less than 1 µm
4. Summary of Test Method
diameter sometimes referred to as combustion black.
4.1 The textural components of coke (coke carbon forms
3.2.8.3 spherulitic carbon, n—a spherical anisotropic car-
and associated coal- and process-related components) in a
bon form sometimes referred to as thermal black that is formed
representative crushed particulate coke sample, prepared in the
by the deposition of carbon concentrically around a nucleus.
form of a briquetted, polished specimen as described in
3.2.9 domain, n—a region of anisotropy in a carbon form
Practice D3997/D3997M, are identified under a microscope
that is distinctively marked by its isochromatic boundary and
according to their degree of anisotropism, carbon form domain
cleavage.
sizes, boundary size, color of individual isochromatic domains,
3.2.10 filler phase, n—a discontinuous solid formed from their morphology, relative reflectance, and other optical prop-
erties. The proportions of these textural components in a
coal macerals and minerals that do not deform thermoplasti-
cally during carbonization. sample are determined by observing a statistically adequate
number of points, and summing those representative of each
3.2.10.1 Discussion—The filler phase material is formed
from coal macerals that are inert with respect to development component. Only area proportions of components are observed
on the briquette surface. However, the area and volume
of thermoplasticity (inertinite), the inorganic components of
coal (minerals), as well as normally reactive coal entities that proportions are the same when the components are randomly
distributed throughout the sample.
are noncoking or have been rendered inert by thermal
oxidation, natural weathering, or brecciation. These inert 4.1.1 Colorphotomicrographsofthetexturalcomponentsof
materials possess their original morphologies, but their reflec- metallurgical coke illustrating their microscopic features are
4,5
tance and chemical properties have been altered prior to or available from various publications and websites.
during carbonization.
5. Significance and Use
3.2.11 green coke, n—carbonaceous binder or filler phase
material that has exceeded the temperature of thermoplasticity,
5.1 The determination of the volume percent of the textural
but has not obtained the temperature of metallurgical coke.
components in coke is useful to characterize the optical
3.2.11.1 Discussion—Green coke is recognized on the basis
properties of coke as it relates to utilization. Specifically, the
of relative reflectance in comparison to fully carbonized coke.
technique has been used as an aid in determining coal blend
Green coke exhibits varying degrees of lower reflectance than
proportions,andrecognitionoffeaturespresentinthecokethat
fully carbonized coke.
can be responsible for coke quality or production problems
such as reduced coke strength or difficulty in removing coke
3.2.12 incipient anisotropic phase, n—a binder-phase car-
from commercial coke ovens, or both. The study of coke
bon texture having a domain size (less than 0.5 µm) that is near
textures is also useful in promoting a better understanding of
the measuring resolution of the light microscope.
coke reactivity, and the relationship between coal petrography
3.2.13 isotropic phase, n—a binder-phase carbon texture
and its conversion to coke.
that exhibits optical properties that are the same in all direc-
5.2 This test method is used in scientific and industrial
tionswhenviewedwithanopticalmicroscopehavingmutually
exclusive polarized light, for example, crossed nicols. research, but not for compliance or referee tests.
3.2.14 lenticular anisotropic phase, n—a group of binder-
phase anisotropic carbon textures distinguished by their lens-
shaped domains (that is, length (L) to width (W) ratio of 2W <
Crelling, J.C., and Rimmer, S.M., Crelling’s Petrographic Atlas of Coals and
Carbons, Southern Illinois University Carbondale, Online, Available: http://
L <4W) and subdivided based on domain widths as fine
www.coalandcarbonatlas.siu.edu/, 2015.
lenticular (1.0 µm to 3.0 µm), medium lenticular (3.0 µm to
Gray, R. J., and DeVanney, K. F., “Coke Carbon Forms: Microscopic Classi-
8.0 µm), and coarse lenticular (8.0 µm to 12.0 µm) size catego-
fication and IndustrialApplications,” International Journal of Coal Geology, Vol 6,
ries. 1986, pp. 277–297.
D5061 − 19
6. Apparatus and kept separate shall be the following: one category for all
binder phase carbons (no discrimination to specific binder
6.1 Microscope—A high quality reflected-light microscope
phase components is necessary), organic inerts (fine), organic
with a vertical illuminator and rotating mechanical stage is
inerts(coarse),inorganicinerts(fine),inorganicinerts(coarse),
used, provided that the objective and eyepiece lenses permit
miscellaneous inerts (by type, such as noncoking vitrinite,
resolution of objects on the order of 0.5 µm.The objective lens
coked oxidized coal, coked brecciated coal, etc.), and others.
shall be of such construction that samples can be studied in oil
Filler phase materials relate back to the parent coal type.
with plane-polarized light. A minimum total magnification of
7.1.3 Miscellaneous Materials Determination—The compo-
approximately 500 diameters is recommended. Use of an
nents counted and kept separate shall be the following:
accessory plate (quartz, gypsum, or mica), an analyzer, and
depositional carbons (by type, that is, sooty, spherulitic, or
polarizer combination is recommended to achieve optimum
pyrolytic)andanyotherobservationssuchasadditives(breeze,
optical effect for discriminating among the various textural
anthracite, petroleum coke, etc.), coal, and green coke (by
components. Either a prism or a partially reflecting glass plate
relative degree). Due to the normally small occurrences or
may be employed in the illuminator. One eyepiece of the
absence of these components, they are commonly counted
microscope must be fitted with a special ruled graticule disc.
during the filler phase counting procedure described in 7.1.2.
6.1.1 Eyepiece Disc—The eyepiece shall contain a ruled
These miscellaneous materials generally relate to coke plant
graticule disc to enable size estimations and to provide a
processes and operational practices not directly related to
field-of-view grid for point counting. The design may be a
parent coal rank or type.
squared pattern (10 by 10 squares) containing a bolder
crosshair with one of the squares near the center crosshair
NOTE 1—The degree of detail necessary will dictate the specific
intersection divided into 25 subsquares. The ruled portion of
components quantified. The specified components to be counted in this
the disc shall cover at least one third of the field of view. test method assume that the operator is generating a detailed analysis. It
may be practical to lump some components together. This is up to the
6.1.2 Mechanical Stage—The mechanical stage shall be of
discretion of the operator or based on agreement between such parties
such type that the specimen can be quickly advanced by
involved.
definite fixed increments in two perpendicular directions (re-
ferred to as the X and Y directions).
8. Procedure
6.2 Counter—The counter shall be capable of recording
8.1 Mount the coke briquette on a glass slide containing
counts for at least eight components (preferably twelve or
modeling clay, level using a specimen leveling press, and place
more) equipped with a totalizer. The counter design can either
on the stage of the microscope. Use a few drops of immersion
be mechanical or electrical.
oi
...

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: D5061 − 16 D5061 − 19
Standard Test Method for
Microscopical Determination of the Textural Components of
Metallurgical Coke
This standard is issued under the fixed designation D5061; 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
1.1 This test method covers the equipment and procedures used for determining the types and amounts of coke carbon forms
and associated recognizable coal- and process-derived textural components in metallurgical coke in terms of volume percent. This
test method does not include coke structural components such as coke pores, coke wall dimensions, or other structural associations.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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 safety, health, and healthenvironmental 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.
2. Referenced Documents
2.1 ASTM Standards:
D121 Terminology of Coal and Coke
D3997/D3997M Practice for Preparing Coke Samples for Microscopical Analysis by Reflected Light
2.2 ISO Standard:
ISO 5725-6: 1994 Accuracy (Trueness and Precision) of Measurement Methods and Results – Part 6: Use in Practice of
Accuracy Values
3. Terminology
3.1 Definitions—For additional definitions of terms used in this test method, refer to Terminology D121.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 anisotropic, adj—exhibiting optical properties of different values when viewed with an optical microscope having
mutually exclusive polarized light, for example, crossed nicols.
3.2.2 binder phase, n—a continuous solid carbon matrix formed during the thermoplastic deformation of those coal macerals
that become plastic during carbonization.
3.2.2.1 Discussion—
The binder phase material is formed from the thermoplastic deformation of reactive (vitrinite and liptinite) and semi-inert
(semifusinite) coal macerals of metallurgical bituminous coals. During thermoplasticity, the inert coal maceral and mineral are
partly or wholly incorporated into the binder phase. Also, most of the coke pores are located in the binder phase.
This test method is under the jurisdiction of ASTM Committee D05 on Coal and Coke and is the direct responsibility of Subcommittee D05.28 on Petrographic Analysis
of Coal and Coke.
Current edition approved April 1, 2016March 15, 2019. Published April 2016June 2019. Originally approved in 1992. Last previous edition approved in 20072016 as
D5061 - 07.D5061 – 16. DOI: 10.1520/D5061-16.10.1520/D5061-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, http://www.iso.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5061 − 19
3.2.3 carbon form, n—microscopically distinguishable carbonaceous textural components of coke, but excluding mineral
carbonates.
3.2.3.1 Discussion—
Carbon forms are recognized on the basis of their reflectance, anisotropy, and morphology. They are derived from the organic
portion of coal and can be anisotropic or isotropic.
3.2.4 circular anisotropic phase, n—a group of binder-phase anisotropic carbon textures that are distinguished by approximately
circular domains (that is length equals width) and composed of fine circular (0.5(0.5 μm to 1.0-μm),1.0 μm), medium circular
(1.0(1.0 μm to 1.5-μm),1.5 μm), and coarse circular (1.5(1.5 μm to 2.0-μm)2.0 μm) size categories.
3.2.5 coke pore, n—a microscopically distinguishable void that is a structural element of coke.
3.2.5.1 Discussion—
Coke pores are considered to be nearly spherical-shaped voids created by the entrapment of gaseous volatiles during the
solidification of thermoplastic coal. However, other types of voids can be distinguished in coke that include fractures or cracks,
interconnected and elongated pores, and the open cell lumens of fusinite and semifusinite. The size and shape of the voids are coal
rank and grade, and to some degree, process dependent. Pore sizes vary from tens of angstroms to tens of millimetres in any given
coke.
3.2.6 coke reactivity, n—a measure of the mass loss when coke, held at a designated temperature, is contacted with gaseous
carbon dioxide over a specific time interval.
3.2.7 coke wall, n—a predominantly carbonaceous layer that encloses a coke pore and which is a structural element and essence
of coke.
3.2.8 depositional carbon, n—a group of carbon forms that are formed from cracking and nucleation of gas-phase hydrocarbon
molecules during coal carbonization.
3.2.8.1 pyrolytic carbon, n—an anisotropic carbon form that is formed by the deposition of carbon parallel to an inert substrate
causing the resulting texture to appear ribbon-like.
3.2.8.2 sooty carbon, n—an isotropic carbon form comprised of approximately spherical particles of less than 1-μm1 μm
diameter sometimes referred to as combustion black.
3.2.8.3 spherulitic carbon, n—a spherical anisotropic carbon form sometimes referred to as thermal black that is formed by the
deposition of carbon concentrically around a nucleus.
3.2.9 domain, n—a region of anisotropy in a carbon form that is distinctively marked by its isochromatic boundary and cleavage.
3.2.10 filler phase, n—a discontinuous solid formed from coal macerals and minerals that do not deform thermoplastically
during carbonization.
3.2.10.1 Discussion—
The filler phase material is formed from coal macerals that are inert with respect to development of thermoplasticity (inertinite),
the inorganic components of coal (minerals), as well as normally reactive coal entities that are noncoking or have been rendered
inert by thermal oxidation, natural weathering, or brecciation. These inert materials possess their original morphologies, but their
reflectance and chemical properties have been altered prior to or during carbonization.
3.2.11 green coke, n—carbonaceous binder or filler phase material that has exceeded the temperature of thermoplasticity, but
has not obtained the temperature of metallurgical coke.
3.2.11.1 Discussion—
Green coke is recognized on the basis of relative reflectance in comparison to fully carbonized coke. Green coke exhibits varying
degrees of lower reflectance than fully carbonized coke.
3.2.12 incipient anisotropic phase, n—a binder-phase carbon texture having a domain size (less than 0.5 μm) that is near the
measuring resolution of the light microscope.
3.2.13 isotropic phase, n—a binder-phase carbon texture that exhibits optical properties that are the same in all directions when
viewed with an optical microscope having mutually exclusive polarized light, for example, crossed nicols.
D5061 − 19
3.2.14 lenticular anisotropic phase, n—a group of binder-phase anisotropic carbon textures distinguished by their lens-shaped
domains (that is, length (L) to width (W) ratio of 2W < L < 4W) and subdivided based on domain widths as fine lenticular
(1.0(1.0 μm to 3.0-μm),3.0 μm), medium lenticular (3.0(3.0 μm to 8.0-μm),8.0 μm), and coarse lenticular (8.0(8.0 μm to
12.0-μm)12.0 μm) size categories.
3.2.15 ribbon anisotropic phase, n—a group of binder-phase anisotropic carbon textures distinguished by their ribbon-like
domains (that is, length (L) to width (W) ratio of L > 4W), and subdivided based on domain width as fine ribbon (2.0(2.0 μm to
12.0-μm),12.0 μm), medium ribbon (12.0(12.0 μm to 25.0-μm),25.0 μm), and coarse ribbon (>25.0-μm)(> 25.0 μm) size categories.
3.2.16 textural component, n—the collective term used to describe carbon forms and recognizable coal- and process-derived
components (binder-phase, filler-phase, and miscellaneous material) in coke.
3.2.17 vitrinite type, n—reflectance classes of vitrinite which span 0.1 % reflectance intervals.
3.2.17.1 Discussion—
This term is commonly referred to as V-Type. For example, V-type 6 includes vitrinite reflectance values from 0.60.6 % through
0.69 %.
4. Summary of Test Method
4.1 The textural components of coke (coke carbon forms and associated coal- and process-related components) in a
representative crushed particulate coke sample, prepared in the form of a briquetted, polished specimen as described in Practice
D3997/D3997M, are identified under a microscope according to their degree of anisotropism, carbon form domain sizes, boundary
size, color of individual isochromatic domains, their morphology, relative reflectance, and other optical properties. The proportions
of these textural components in a sample are determined by observing a statistically adequate number of points, and summing those
representative of each component. Only area proportions of components are observed on the briquette surface. However, the area
and volume proportions are the same when the components are randomly distributed throughout the sample.
4.1.1 Color photomicrographs of the textural components of metallurgical coke illustrating their microscopic features are
4,5
available from various publications and websites.
5. Significance and Use
5.1 The determination of the volume percent of the textural components in coke is useful to characterize the optical properties
of coke as it relates to utilization. Specifically, the technique has been used as an aid in determining coal blend proportions, and
recognition of features present in the coke that can be responsible for coke quality or production problems such as reduced coke
strength or difficulty in removing coke from commercial coke ovens, or both. The study of coke textures is also useful in promoting
a better understanding of coke reactivity, and the relationship between coal petrography and its conversion to coke.
5.2 This test method is used in scientific and industrial research, but not for compliance or referee tests.
6. Apparatus
6.1 Microscope—A high quality reflected-light microscope with a vertical illuminator and rotating mechanical stage is used,
provided that the objective and eyepiece lenses permit resolution of objects on the order of 0.5 μm. The objective lens shall be of
such construction that samples can be studied in oil with plane-polarized light. A minimum total magnification of approximately
500 diameters is recommended. Use of an accessory plate (quartz, gypsum, or mica), an analyzer, and polarizer combination is
recommended to achieve optimum optical effect for discriminating among the various textural components. Either a prism or a
partially reflecting glass plate may be employed in the illuminator. One eyepiece of the microscope must be fitted with a special
ruled graticule disc.
6.1.1 Eyepiece Disc—The eyepiece shall contain a ruled graticule disc to enable size estimations and to provide a field-of-view
grid for point counting. The design may be a squared pattern (10 by 10 squares) containing a bolder crosshair with one of the
squares near the center crosshair intersection divided into 25 subsquares. The ruled portion of the disc shall cover at least one third
of the field of view.
6.1.2 Mechanical Stage—The mechanical stage shall be of such type that the specimen can be quickly advanced by definite
fixed increments in two perpendicular directions (referred to as the X and Y directions).
6.2 Counter—The counter shall be capable of recording counts for at least eight components (preferably twelve or more)
equipped with a totalizer. The counter design can either be mechanical or electrical.
Crelling, J.C., and Rimmer, S.M., 2015, Crelling’s Petrographic Atlas of Coals and Carbons, Southern Illinois University Carbondale, http://
www.coalandcarbonatlas.siu.edu/.Online, Available: http://www.coalandcarbonatlas.siu.edu/, 2015.
Gray, R. J., and DeVanney, K. F., “Coke Carbon Forms: Microscopic Classification and Industrial Applications,” International Journal of Coal Geology, Vol 6, 1986,
pp. 277–297.
D5061 − 19
6.3 Immersion Oil—The oil shall be a nondrying, noncorrosive, noncarcinogenic type having similar properties as used for coal
microscopic techniques.
TABLE 1 Classification of Coke Textural Components
Binder Phase
Domain Dimensions
Parent Coal Bituminous
Length (L) to Width (W) A
Vitrinite Type Coal (Volatility)
Width, μm
Relation
Isotropic 0.0 None 6, 7 high
Incipient (anisotropic) 0.5 L = W 8 high
Circular (anisotropic)
Fine circular 0.5–1.0 L = W 9 high
Fine circular 0.5 to 1.0 L = W 9 high
Medium circular 1.0–1.5 L = W 10 high
Medium circular 1.0 to 1.5 L = W 10 high
Coarse circular 1.5–2.0 L < W 11 high to medium
Coarse circular 1.5 to 2.0 L < W 11 high to medium
Lenticular (anisotropic)
Fine lenticular 1.0–3.0 L $ 2W,L < 4 W 12 high to medium
Fine lenticular 1.0 to 3.0 L $ 2W,L < 4 W 12 high to medium
Medium lenticular 3.0–8.0 L > 2W,L < 4W 13 medium
Medium lenticular 3.0 to 8.0 L > 2W,L < 4W 13 medium
Coarse lenticular 8.0–12.0 L > 2W,L # 4W 14 medium to low
Coarse lenticular 8.0 to 12.0 L > 2W,L # 4W 14 medium to low
Ribbon (anisotropic)
Fine ribbon 2.0–12.0 L > 4W 15 medium to low
Fine ribbon 2.0 to 12.0 L > 4W 15 medium to low
Medium ribbon 12.0–25.0 L > 4W 16 low
Medium ribbon 12.0 to 25.0 L > 4W 16 low
Coarse ribbon 25.0 + L > 4W 17, 18 low
Filler Phase
Size, μm Precursor Material
Organic inerts:
Fine <50 micrinite, macrinite, inertodetrinite
Fine < 50 micrinite, macrinite, inertodetrinite
Coarse $50 semifusinite, fusinite, macrinite
Coarse $ 50 semifusinite, fusinite, macrinite
Miscellaneous inerts:
Oxidized coal (coke) . oxidized coal
Brecciated coal (coke) . brecciated coal
Noncoking vitrinite (coke) . vitrinite too high or low in rank
Inorganic inerts: . various types of mineral matter
Fine <50 coal mineral matter and bone coal
Fine <
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