EN 10247:2017

Micrographic examination of the non-metallic inclusion content of steels using standard pictures

This draft European Standard defines a method of microscopic non-metallic endogenous inclusion assessment using picture charts.
The method does not apply to particles of a length or diameter less than 3,0 µm or a width smaller than 2,0 µm. If defined by a product standard or agreement between the involved parties for certain special products, inclusions with a width below 2,0 µm can be evaluated by length alone.Inclusions with dimensions exceeding the upper limits in Table 2 are evaluated as belonging to the maximum class and noted separately with their true dimensions (see 7.5.6).
It is assumed, if particles are elongated or if there are stringers of particles, that they are parallel to each other. Other arrangements are not covered by this draft standard. This draft European Standard applies to samples with a microscopic precipitation approaching random distribution.
From the data of measurements obtained by this method, evaluation according to other standards can be established.
This draft European Standard does not apply to free cutting steels.
NOTE   The basic principle of this draft European Standard allows the determination of non-metallic inclusion content by image analysis techniques.

Metallographische Prüfung des Gehaltes nichtmetallischer Einschlüsse in Stählen mit Bildreihen

Dieser Europäische Normentwurf legt ein Verfahren zur mikroskopischen Kennzeichnung von nichtmetallischen endogenen Einschlüssen unter Verwendung von Richtreihenbildern fest.
Das Verfahren gilt nicht für Teilchen mit einer Länge oder einem Durchmesser kleiner als 3,0 µm oder einer Breite kleiner als 2,0 µm. Sofern in einer Produktnorm oder durch Vereinbarung zwischen den Beteiligten für spezielle Produkte festgelegt, können Einschlüsse mit einer Breite kleiner als 2,0 µm ausschließlich nach ihrer Länge bewertet werden. Einschlüsse, deren Maße die in Tabelle 2 angegebenen oberen Grenzen überschreiten, werden als zugehörig zur größten Klasse gewertet und gesondert mit ihren tatsächlichen Maßen aufgezeichnet (siehe 7.5.6).
Es wird vorausgesetzt, falls Teilchen gestreckt sind oder falls zeilenförmige Anordnungen von Teilchen auftreten diese parallel zueinander liegen. Andere Anordnungen werden durch diesen Normentwurf nicht berück¬sichtigt. Dieser Europäische Normentwurf gilt für Proben mit mikroskopischen Agglomerationen unter der Annahme einer makroskopisch regellosen Verteilung.
Aus den mit den hier beschriebenen Verfahren erzielten Messwerten kann eine Auswertung nach anderen Normen abgeleitet werden.
Dieser Europäische Normentwurf gilt nicht für Automatenstähle.
ANMERKUNG   Das Grundprinzip dieses Europäischen Normentwurfes ermöglicht die Bestimmung des Gehaltes an nichtmetallischen Einschlüssen mittels Bildanalysetechnik.

Détermination micrographique de la teneur en inclusions non-métalliques des aciers à l'aide d'images-types

Ce projet de Norme européenne définit une méthode de cotation des inclusions microscopiques endogènes non-métalliques à l'aide d'images types.
La méthode ne s'applique pas aux particules de longueur ou diamètre inférieure à 3,0 µm ou de largeur inférieure à 2,0 µm. Lorsque cela est défini dans la norme de produit ou par accord entre les parties intéressées, les inclusions de largeur inférieure à 2,0 µm peuvent être évaluées uniquement selon leur longueur. Les inclusions allongées de longueur supérieure aux limites indiquées au Tableau 2 sont comptées comme faisant partie de la classe maximum et notées séparément avec leurs dimensions réelles (voir 7.5.6)
Il est admis que si les particules sont allongées ou si elles sont en amas, elles sont parallèles entre elles. D'autres dispositions ne sont pas couvertes par ce projet de Norme. Ce projet de Norme européenne s'applique aux échantillons présentant une ségrégation microscopique présentant une distribution au hasard.
À partir des données des mesures obtenues par la présente méthode, une évaluation selon d'autres normes peut être établie.
Ce projet de Norme européenne n'est pas adapté aux aciers de décolletage.
NOTE   Le principe de base de ce projet de Norme européenne permet la détermination de la teneur inclusionnaire par les techniques d'analyse d'image.

Mikrografsko ugotavljanje deleža nekovinskih vključkov v jeklih z uporabo standardnih slik

Ta osnutek evropskega standarda opredeljuje metodo mikroskopskega ugotavljanja deleža nekovinskih vključkov v jeklih z uporabo slik.
Metoda se ne uporablja za delce dolžine ali premera manj kot 3,0 μm ali širine, manjše od 2,0 μm. Če tako določa standard za izdelek ali sporazum med vpletenimi strankami za določene posebne izdelke, je mogoče ugotoviti delež vključkov s širino pod 2,0 μm samo po dolžini. Ugotavljanje deleža vključkov z merami, ki presegajo zgornje meje v tabeli 2, se izvaja ob predpostavki, da pripadajo najvišjemu razredu in se posebej zabeležijo s svojimi dejanskimi dimenzijami (glej 7.5.6).
Če so delci podolgovati ali če obstajajo ostanki delcev, se predpostavlja, da so med seboj vzporedni. Druge ureditve niso zajete v osnutku tega standarda. Ta osnutek evropskega standarda se uporablja za vzorce z mikroskopskimi usedlinami, ki se približujejo naključni porazdelitvi.
Iz podatkov meritev, pridobljenih s to metodo, je mogoče izvesti vrednotenje v skladu z drugimi standardi.
Ta osnutek evropskega standarda se ne uporablja za avtomatna jekla.
OPOMBA: Osnovno načelo tega osnutka evropskega standarda omogoča določanje vsebnosti nekovinskih vključkov s pomočjo tehnik za analizo slike.

General Information

• Status: Published
• Publication Date: 11-Jul-2017
• Withdrawal Date: 30-Jan-2018
• ICS: 77.040.99 - Other methods of testing of metals
• Technical Committee: ECISS/TC 101 - Test methods for steel (other than chemical analysis)
• Drafting Committee: ECISS/TC 101 - Test methods for steel (other than chemical analysis)
• Current Stage: 9093 - Decision to confirm - Review Enquiry
• Start Date: 29-May-2024
• Completion Date: 14-Apr-2025
• Ref Project: SIST EN 10247:2017 - Micrographic examination of the non-metallic inclusion content of steels using standard pictures

Relations

• Replaces: EN 10247:2007 - Micrographic examination of the non-metallic inclusion content of steels using standard pictures
• Effective Date: 10-Jul-2013

Overview

EN 10247:2017 (CEN) specifies a micrographic method for assessing the non‑metallic inclusion content of steels using standard picture charts. The standard defines microscopic evaluation procedures that yield results in physical units (length, diameter, area) and supports both manual chart-based assessment and image analysis techniques. EN 10247:2017 supersedes EN 10247:2007 and provides clarified mathematical principles for the chart and updated assessment rules.

Key topics and requirements

• Scope and limits

  • Applies to microscopic endogenous (internal) non‑metallic inclusions in steels using picture charts.
  • Does not apply to particles with length or diameter < 3.0 µm or width < 2.0 µm, unless a product standard or agreement permits width‑only assessment for special products.
  • Excludes free‑cutting steels and non‑covered arrangement types (e.g., non‑parallel stringers).
  • Inclusions larger than chart upper limits are recorded as the maximum class with true dimensions noted.

• Assessment methods

  • Three principal rating methods are defined: worst inclusion (P), worst field (M), and average field (K), allowing flexible use depending on specification or quality objective.
  • Classification begins with length (row index) and covers diameter/width and area as appropriate.

• Practical microscope and sampling requirements

  • Guidance on sampling, specimen preparation, magnification, field of view, and microscope/eyepiece graticule setup to ensure reproducible results.
  • Rules for scanning, handling mixed‑size inclusions in a field, and recording results.
  • Annexes provide calculation bases, chart construction, shape factors and recommended eyepiece graticule details.

• Image analysis

  • The standard’s principles allow substitution of manual chart comparison by image analysis techniques, maintaining equivalent precision.

Applications and users

• Typical users:
  • Metallurgists, quality engineers, inspection labs, steel producers, and R&D teams.
  • Organizations specifying steel cleanliness in contracts or product standards.
• Practical uses:
  • Quality control and incoming material inspection.
  • Verifying compliance with product specifications that reference inclusion ratings.
  • Failure analysis, process optimization and microstructural research where inclusion morphology affects performance.

Related standards

• EN 10247:2017 is intended to interoperate with product standards and other inclusion‑rating methods; results from this method can be converted to alternative standards' formats when required. For product‑specific rules, follow the applicable product standard or contractual agreement.

Keywords: EN 10247:2017, micrographic examination, non‑metallic inclusions, steels, inclusion assessment, picture charts, CEN, metallography, image analysis, worst inclusion method, average field method.

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2017
0LNURJUDIVNRXJRWDYOMDQMHGHOHåDQHNRYLQVNLKYNOMXþNRYYMHNOLK]XSRUDER
VWDQGDUGQLKVOLN
Micrographic examination of the non-metallic inclusion content of steels using standard
pictures
Metallographische Prüfung des Gehaltes nichtmetallischer Einschlüsse in Stählen mit
Bildreihen
Détermination micrographique de la teneur en inclusions non-métalliques des aciers à
l'aide d'images- types
Ta slovenski standard je istoveten z: EN 10247:2017
ICS:
77.040.99 Druge metode za Other methods of testing of
preskušanje kovin metals
77.080.20 Jekla Steels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 10247
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2017
EUROPÄISCHE NORM
ICS 77.040.99 Supersedes EN 10247:2007
English Version
Micrographic examination of the non-metallic inclusion
content of steels using standard pictures
Détermination micrographique de la teneur en Metallographische Prüfung des Gehaltes
inclusions non-métalliques des aciers à l'aide d'images- nichtmetallischer Einschlüsse in Stählen mit Bildreihen
types
This European Standard was approved by CEN on 18 January 2017.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 10247:2017 E
worldwide for CEN national Members.

Contents Page
European foreword . 5
Introduction . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Symbols and abbreviations . 10
5 Principles . 12
6 Brief practical guide . 13
6.1 Basic rules for evaluation . 13
6.2 Evaluation according to the default rating methods . 14
7 Sampling . 14
7.1 General . 14
7.2 Degree of reduction . 15
7.3 Size and location of test area . 15
7.4 Number of specimens . 15
7.5 Preparation of specimens . 16
8 Test method . 16
8.1 Magnification . 16
8.2 Microscope settings for image analysis and manual analysis . 16
8.3 Field of view . 17
8.4 Definition of the pictures of the chart . 17
8.4.1 Size and Shape . 17
8.4.2 Parameters . 17
8.4.3 Arrangement of the pictures . 17
8.5 Procedure. 18
8.5.1 General . 18
8.5.2 Several inclusions of mixed sizes in one field . 18
8.5.3 Scanning . 18
8.5.4 Assessment and evaluation . 19
8.5.5 Evaluation of different types of inclusions . 19
8.5.6 Recording of results . 19
9 Types of assessment . 19
9.1 Worst inclusion method: method P . 19
9.1.1 Principle . 19
9.1.2 Evaluation of P (worst length) . 20
L
9.1.3 Evaluation of P (worst diameter). 20
d
9.1.4 Evaluation of P (worst area) . 20
a
9.2 Worst field method: method M. 20
9.2.1 Principle . 20
9.2.2 Evaluation of M (rating according to number) . 20
n
9.2.3 Evaluation of M (rating according to length) . 20
L
9.2.4 Evaluation of M (rating according to diameter) . 20
d
9.2.5 Evaluation of M (rating according to area) . 21
a
9.3 Average field method: method K . 21
9.3.1 Principle . 21
9.3.2 Scanning of a specimen for average field assessment . 21
9.3.3 Evaluation. 21
9.3.4 Evaluation of K , K for elongated and K , K for globular inclusions. 21
n L n d
9.3.5 Evaluation of K and K . 22
n a
10 Test report . 22
Annex A (normative) Type of inclusions . 34
Annex B (normative) Parameters and assessments to be used if not otherwise specified . 37
Annex C (informative) Examples for inclusions of different types . 38
Annex D (informative) Shape factor . 42
Annex E (informative) Examples for magnification . 43
Annex F (informative) Details of the eyepiece graticules . 45
Annex G (normative) Manufacturing specifications of the eyepiece graticule. 46
G.1 General . 46
G.2 Narrow field microscopes. 46
G.3 Broad field microscopes . 48
Annex H (normative) Calculation basis for the pictures of the chart . 50
Annex I (normative) Rules for classification . 52
I.1 Definition of classes . 52
I.2 Classification of length . 52
I.3 Classification of width . 52
I.4 Classification of diameter . 52
Annex J (informative) Comparison of inclusion types in different standards . 53
Annex K (informative) Worst inclusion assessment . 54
Annex L (informative) Worst field assessment . 58
L.1 General . 58
L.2 Evaluation of M . 58
n
L.3 Evaluation of M , M and M . 58
n L d
L.4 Evaluation of M and M . 58
n a
Annex M (informative) Average field assessment . 62
M.1 General . 62
M.2 Evaluation of K , K and K . 62
n L d
M.3 Evaluation of K and K . 62
n a
M.4 Restricted assessment . 62
Annex N (normative) Calculation basis for the assessment . 74
N.1 Worst inclusion assessment . 74
N.2 Worst field assessment . 74
N.3 Average field . 75
Annex O (informative) Edge Errors correction . 77
O.1 General . 77
O.2 Measurement . 77
O.3 Large inclusions . 77
Annex P (normative) Calculation of average values of parameters for one class . 79
Annex Q (normative) Average values of parameters . 80
Bibliography . 81

European foreword
This document (EN 10247:2017) has been prepared by Technical Committee ECISS/TC 101 “Test
methods for steel (other than chemical analysis)”, the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by January 2018, and conflicting national standards shall
be withdrawn at the latest by January 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 10247:2007.
The many changes in the current revision result from only a few basic adjustments. The length to width
limit ratio for globular inclusions has been changed from 1,3 to 3 (Annex I), and the mathematical
principles underlying the chart have been more clearly defined (Annex H). These two changes have led
to many numerical changes in Table 2 and Figure 11, where moreover some classes have been deleted
and others added. The rules of assessment have changed, most notably to allow stringer formation from
two particles upward (Subclause 3.1.2, Annex B), to exclude stringer formation between a stringer and
a single particle (Subclause 3.1.2), and to consistently define the classification of inclusions by shape,
arrangement, and colour (Clause 3, Annexes A and B). Finally, the assessment and recording sheets
have been redesigned to simplify manual use (Annexes K, L, and M).
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Introduction
This document establishes procedures for the assessment of inclusions in steels, based on their
morphology using standard pictures.
These procedures include principles that yield results coherent with consolidated individual inclusion
measurements and expressed in physical units.
The chart of standard pictures is derived from mathematical principles. In distinction to other inclusion
rating standards, in this standard the order of the classification begins with the length (row index q).
The results may be directly computed from field assessments. The same precision level is achieved by
using the same method in manual evaluation and computer controlled measurements.
2 2 2 2
The results are in physical units: length in μm/mm , number/mm , areas in μm /mm .
1 Scope
This European Standard defines a method of microscopic non-metallic endogenous inclusion
assessment using picture charts.
The method does not apply to particles of a length or diameter less than 3,0 µm or a width smaller than
2,0 µm. If defined by a product standard or agreement between the involved parties for certain special
products, inclusions with a width below 2,0 µm can be evaluated by length alone. Inclusions with
dimensions exceeding the upper limits in Table 2 are evaluated as belonging to the maximum class and
noted separately with their true dimensions (see 8.5.6).
It is assumed, if particles are elongated or if there are stringers of particles, that they are parallel to each
other. Other arrangements are not covered by this draft standard. This draft European Standard applies
to samples with a microscopic precipitation approaching random distribution.
From the data of measurements obtained by this method, evaluation according to other standards can
be established.
This draft European Standard does not apply to free cutting steels.
NOTE The basic principle of this draft European Standard allows the determination of non-metallic inclusion
content by image analysis techniques.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
(ISO/IEC 17025)
ISO 9042, Steels — Manual point counting method for statistically estimating the volume fraction of a
constituent with a point grid
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 General:
3.1.1
particle
single precipitate, in general non-metallic
3.1.2
stringer
arrangement of at least 2 particles, normally aligned, that meet the proximity conditions e ≤ 40 µm and
t ≤ 10 µm
Note 1 to entry: For formation of stringers particles with L < 3 µm or w < 2 µm are not taken into account
(see Figure 5).
Note 2 to entry: See Figure 3 for proximity conditions, Figure 7 and Annex B and Annex C for examples
3.1.3
inclusion
general designation of a ratable feature composed of at least one particle, defined by the size and
proximity of its constituents
Note 1 to entry: The inclusion can describe a single particle; a single stringer; or an agglomeration of stringers.
Note 2 to entry: Stringers that meet the proximity conditions e ≤ 40 µm and t ≤ 10 µm form an agglomeration of
stringers (see Figure 4). Formation of inclusions by combining stringers and single particles is not permitted.
Note 3 to entry: If elongated and globular particles are combined (see Figure 6), in general the result is treated
as one inclusion.
Note 4 to entry: For further examples see Figure 7.
3.1.4
test area
area on the polished surface of the specimen to be evaluated
3.2 Proximity:
3.2.1
distances between particles
distance e between the particles in the direction of main deformation and distance t in the direction
perpendicular to it
Note 1 to entry: See Figure 3 for illustration.
3.2.2
distance between stringers
similar to that for the distance between particles
Note 1 to entry: See Figure 4 for illustration.
3.2.3
scattered
random arrangement of particles
Note 1 to entry: For example see Annex C. This is defined in one field of view.
3.3 Parameters:
3.3.1
length
dimension of an inclusion in the main deformation direction, usually larger than the width
3.3.2
diameter
maximum dimension of inclusion classified according to column 6 (globular inclusion)
3.3.3
width
dimension of inclusion perpendicular to the direction of principal deformation
Note 1 to entry: In particular for inclusions consisting of more than one particle, a subscript of “total” can be
used to distinguish its width from the individual widths of the particles.
Note 2 to entry: For inclusions consisting of a single particle, the width is the maximum dimension
perpendicular to the main deformation direction (see Figure 1).
For inclusions consisting of a single stringer, the width is the width of the confining rectangle (see Figure 2).
For inclusions consisting of an agglomeration of stringers, three cases apply:
— Case a) two stringers for which 0 ≤ e ≤ 40 µm, t ≤ 10 µm: the width of this inclusion is the width of the widest
stringer (w = w ; w > w ; see Figure 4 a)).
total 1 1 2
— Case b) two stringers for which e < 0 µm, t ≤ 10 µm: the width of this inclusion is the sum of the stringers’
widths and the distance t (wtotal = w1 + w2 + t; see Figure 4 b)).
— Case c) an agglomeration of more than two stringers: the width of this inclusion is the widest width obtained
by applying the rules in case a) and b) (see Figure 4 c))
3.3.4
area
area of the equivalent ellipse, calculated as
π
a= × Lw× , (1)
total
or, in the case of globular particles,
π
ad× (2)
Note 1 to entry: For details see 3.3.2 and Figures 1, 2, and 4.
3.3.5
shape factor
exponent f in the formula:
π f
× L
 L 
= (3)
 
a 1µm
 
Note 1 to entry: For details see Annex D.
3.4 Classes:
3.4.1
elongated particles
particles with a ratio L/w ≥ 3
Note 1 to entry: See Figure 1 for illustration.
=
3.4.2
globular particles
particles with a ratio L/w < 3
Note 1 to entry: See Figure 1 for illustration.
3.4.3
type
distinction of inclusions according to their shape, arrangement, and colour, and, if desired, by their
apparent chemical composition
Note 1 to entry: See Annex A for illustration.
3.5 Others:
3.5.1
lot
unit of material processed at one time and subject to similar processing variables
3.5.2
restricted values
values of the average field assessment restricted to inclusions of a specified size range, or restricted to
inclusions of specified types
Note 1 to entry: See Annex M.4 and Tables M.6 and M.7 for further detail.
4 Symbols and abbreviations
For the purposes of this document, the following symbols and abbreviations apply.
Symbol Unit Designation
A area of field of view on the specimen
µm
B polished surface
mm
D  diameter of product
G  magnification
H µm length of measuring frame on the specimen
-, µm,
K average field assessment
2 2
µm /mm
L µm length of inclusions
-, µm,
M worst field assessment
2 2
µm /mm
MD  main deformation direction (e.g. rolling direction)
N
number of fields
j
N
number of specimens
s
P  worst inclusion assessment
Q  factor for K-assessment
R  restricted values
a area of inclusions
µm
−
average (mean) value of n, L, w, a .
av or
b mm width of the plate
b  black
c  coloured (pink or yellow) (typically nitrides)
d µm diameter of inclusions
distance between the particles in the main deformation
e µm
direction
f  shape factor
g  grey (typically sulphides)
i  inclusion index
j  field index
k  column number
m  type of inclusion index
max  index of maximum value of n, L, w, d, a (in j or s)
n  number of assessed particles, inclusions
n
number of assessed inclusions per specimen
s
p  particle index
q  row number
s  specimen index
distance between the particles perpendicular to the
t µm
main deformation direction
u µm scale unit in microscope eyepiece
v mm width of polished surface
w µm width of inclusions
x  variable
α  scattered, elongated inclusion type
α  scattered, elongated, black inclusion type
b
αc  scattered, elongated, coloured inclusion type
αg  scattered, elongated, grey inclusion type
β  aligned, globular inclusion type
βb  aligned, globular, black inclusion type,
β  aligned, globular, coloured inclusion type
c
βg  aligned, globular, grey inclusion type
γ  aligned, elongated inclusion type
γb  aligned, elongated, black inclusion type
γc  aligned, elongated, coloured inclusion type
γg  aligned, elongated, grey inclusion type
δ  scattered, globular inclusion type
δb  scattered, globular, black inclusion type
δc  scattered, globular, coloured inclusion type
δ  scattered, globular grey inclusion type
g
Combined symbols shall be written with indices.
EXAMPLE K average field assessment for length;
L
n number of inclusions in a field;
j
average number of inclusions per field.
n
j
5 Principles
This standard consists of a comparison between inclusions observed in a field of view and chart
pictures. The chart classifies inclusions into four different types according to their shape (8.4 /
Annex H). The minimum requirements for applying this method are a square measuring frame of
0,71 mm x 0,71 mm overlaid on the viewfield at a magnification of 100:1 (see Figure 9), along with the
chart – or alternatively a measuring scale and Table 2 of this draft standard.
An inclusion according to this standard can consist of a single particle, a stringer of particles, or an
agglomeration of stringers. All inclusions are treated as ellipses (see Figure 1), with special rules for
agglomerations of stringers (3.1.3 / Figure 4). Inclusions are classified according to shape, arrangement,
and size (Annex A). A classification by colour is also permissible in order to differentiate apparent
chemical composition (Annex A), although this classification provides no information on crystal
structure or actual chemical composition.
The length and width of an inclusion are estimated by the class values of its corresponding row and
column in the picture chart. The chart pictures depict the upper class boundaries. Upon classification,
all further calculations refer to the class values in Table 2.
This standard yields different results depending on the chosen method: the largest inclusions (worst
inclusion method), the largest inclusion parameters per field of view (worst field method), and an
averaged inclusion content (average field method). If not determined by product standards, the
involved parties shall agree on the preferred method for their steel grade. The default rating methods
are the worst inclusion method (P ) and the average field method (K , K ). All results have physical
L/d n L/d
dimensions, regardless of the method.
Annexes M, N, and P include examples for recording and for calculating results. The following section
contains a brief practical guide to the evaluation specified in this standard.
6 Brief practical guide
6.1 Basic rules for evaluation
a) Preparing the measurement:
1) Take and prepare specimens according to Clause 7, Sampling.
2) Define the test area and a starting point for the measurement.
b) Examining the test area:
1) Scan the entire test area at the selected magnification (usually 100:1).
2) Evaluate all inclusions using the measurement frame or a measuring scale, or image analysis.
c) Exclusion of particles outside of the scope:
1) Exclude from evaluation all particles with a length or diameter < 3 µm or a width < 2 µm.
d) Rules for ascertaining inclusions:
1) Distinguish globular from elongated particles using the length-to-width ratio. According to 3.4
Classes, particles with L/w < 3 are globular and particles with L/w ≥ 3 are elongated.
2) Inclusions can consist of a single particle, a stringer of particles, or an agglomeration of
stringers.
3) The proximity conditions for joining together particles or stringers are e ≤ 40 µm and t ≤ 10 µm
(see 3.1.2, stringer, and Note 2 to 3.1.3, inclusion).
4) Particles that do not meet the proximity conditions are rated as individual inclusions.
5) A stringer is formed and rated as an inclusion when at least two particles meet the proximity
conditions.
6) Stringers that meet the proximity conditions are joined to form an agglomeration of stringers.
The agglomeration (and not the individual stringers) is rated as an inclusion.
7) Inclusions consisting of different types of particles are classified according to the areally
predominant shape and subsequently, if necessary, according to the areally predominant
colour.
8) Inclusions longer than the field of view are rated according to their total dimensions and only
rated once.
9) Inclusions longer or wider than the classes in the scope of this standard (oversized) are rated
as belonging to the largest possible class and reported separately with their actual dimensions.
e) Rating the inclusions:
1) Using a measuring scale and the chart (or Table 2), the observed inclusions are classified
according to shape, arrangement, and size, and rated according to the parameters of the chosen
method (see Clause 9, Types of assessment).
2) The inclusions are assigned to the types α, β, γ and δ according to their shape and arrangement.
Where a differentiation by colour is required, inclusions are assigned to the types EA, EC, EAB,
EB, EAD, and ED (see Annex A).
3) The inclusions are rated according to Table 2 or the picture chart. The chart pictures and
values in Table 2 represent the upper class boundaries.
4) An inclusion is classified in row q if for its length L
x:
L < L ≤ L [µm]
q-1 x q
5) An inclusion is classified in column k if for its width w :
x
w < w ≤ w [µm]
q,k-1 x q,k
Upon classification by length and width, all further calculations (e.g. for inclusion area) refer to the class
values in Table 2.
6.2 Evaluation according to the default rating methods
— Method P , P – Ascertaining the largest inclusions by length and diameter
L d
(see Subclause 9.1, method P):
For every inclusion type (α, β, γ, δ or EA, EAD, EB, EAB, EC, ED), rate and record the inclusion with
the largest value for the chosen parameter (L or d). The recording sheet K.1 can be used for
documentation (see Annex K).
The result is the average of the individual values for each specimen.
— Method K , K and K , K – Ascertaining the mean inclusion content by number, as well as by
n L n d
length and diameter (see Subclause 9.3 and Annex M):
Rate and record every inclusion of the chosen types (e.g.: α, β, γ, δ or EA, EAD, EB, EAB, EC, ED)
according to the chosen parameter (L or d). Take care that each inclusion is recorded once and only
once. Record the examined area. The recording sheet M.2 can be used for documentation
(see Annex M).
The result is an averaged inclusion content. The computation sheet M.3 can be used to obtain this
result (see Annex M).
7 Sampling
7.1 General
Unless otherwise specified in the technical delivery conditions, the following requirements apply.
7.2 Degree of reduction
The shape of the inclusions depends, to a large extent, on the degree of reduction of the steel. The chart
can only be used if the shape of inclusions in the specimen can be compared with that given in the
pictures of the chart.
NOTE The lower the degree of reduction, the likelier it is that porosities remain in the steel. Failing to
properly differentiate them from inclusions will affect the final result. Too high a degree of reduction will lead to
inappropriate statistical representation of the longest inclusions.
7.3 Size and location of test area
The polished surface of the specimen used to determine the content of inclusions should cover a
minimum of 200 mm (e.g. 20 mm x 10 mm) and shall be parallel to the direction of the main
deformation direction (e.g. rolling direction).
The sampling and the number of specimens shall be specified in the product standard or shall be
subject to agreement between parties.
In the absence of an agreement, the sampling procedure shall be as follows, see Figure 8:
a) bar or billets with a diameter above 50 mm: the test area shall be located halfway between the
outer surface and the centre. The longer side shall be perpendicular and the shorter side parallel to
the main deformation direction (see Figure 8 a));
b) bar with a diameter greater than 25 mm and less than or equal to 50 mm: the surface to be
examined consists of half the diametric section (from the centre to the edge of the specimen)
(see Figure 8 b));
c) bar with a diameter less than or equal to 25 mm: the surface to be examined consists of the full
diametric section (see Figure 8 c));
d) plates with a thickness less than 25 mm: the specimen contains the whole thickness
(see Figure 8 d));
e) plates with a thickness between 25 mm and 50 mm: the specimen contains half the thickness,
position between surface and centre;
f) plates with a thickness greater than 50 mm: the specimen contains one quarter of the thickness.
The position is not defined.
The positions of the measuring planes for tubes are given in Figure 8 e).
For thin products one sample could comprise several specimens. In this case the test area is smaller
than 200 mm per specimen.
For any other product, the sampling procedures shall be subject to agreement between parties.
7.4 Number of specimens
Single specimens do not provide a representative index of the content of inclusions of a cast or a batch
and therefore the test shall be carried out on a number of specimens. If the number of specimens taken
is not defined in the product standard or by special agreement, the content of inclusions shall be
determined on not less than six specimens.
7.5 Preparation of specimens
The specimen shall be cut so as to obtain a surface for examination. In order to achieve a flat surface
and to avoid rounding the edges of the specimen when polishing, the specimen may be held
mechanically or may be mounted.
When polishing specimens, it is important to avoid any tearing out or deformation of the inclusions or
contamination of the polished surface, so that the surface is as clean as possible and the appearance of
the inclusions is not affected. These precautions are of particular importance when the inclusions are
small. It is advisable to use diamond paste for polishing. The kind of lubricant can depend on the
inclusion type (water may not be an acceptable lubricant for certain types of inclusions, e.g. sulfides).
No particles of a grinding or polishing agent shall be pressed into the polished surface. In certain cases
it may be necessary for the specimen to be hardened before polishing in order to retain inclusions.
8 Test method
8.1 Magnification
The measuring frame length of 710 µm shall be used if nothing else is specified. If it is not possible to
use this value, other magnifications can be used and shall be recorded. The magnification shall not be
changed during one measurement.
When analyzing images, the resolution of the picture shall be higher than the shortest length to be
determined. Magnifying hundredfold (10x lens), the calibration factor should be 1 µm / pixel or finer
and adapted to the optical resolution of the complete system, which ranges up to 0,3 µm in the ideal
case. The smallest particles to be determined should be mapped at at least 10 pixels.
The magnification G is defined only by the size of the measuring frame on the specimen. To use the
chart with different magnifications, the length H of the side of the measuring frame on the specimen will
have one of the three following values: H = 355 µm, H = 710 µm, H = 1 420 µm.
These values shall be used with an accuracy of ± 0,02 mm for manual evaluation. The area A of one
measuring frame on the specimen is given in Table 1.
Table 1 — Area A in function of the measuring frame
H A Magnification
µm 2
mm
355 0,13 (0,126) 200:1
710 0,50 (0,504) 100:1
1 420 2,0 (2,016) 50:1
EXAMPLE See Annex E.
8.2 Microscope settings for image analysis and manual analysis
For automated particle detection the full dynamic range of 8 bit gray values and/or colour values
should be used. To achieve the maximum possible image dynamics, settings of the microscope and of
the digital image source should be set according to the manufacturer's recommendations. The image
source, provided it has an adjustable Gamma (gamma correction), should be set to a gamma correction
value of 1.
The matrix should be located at the top of the gray level scale (>200) as an approximate normal
distribution. Everything outside this matrix normal distribution in the direction of gray level 0 (black)
should be considered as particles. In the case of the distinction between gray and black particles, this
area may again be divided. As a general rule, black is defined as the range from 0 - 130 and gray as the
range from 131 to about 180. These ranges are not absolute or normative. The segmentation should be
checked in the gray scale image. The flicker method is a recognized method for this purpose.
Colour image analyses should be handled similarly.
8.3 Field of view
At a magnification corresponding to H = 710 µm the square frame is given by an etched glass in the
eyepiece graticule, as defined in Figure 9. For broad field microscopes, the etched glass defined in
Figure 10 may be used.
Additional information is drawn on the etched glass (see Annex F), and information concerning the
manufacturing of the graticules is given in Annex G.
One scale unit in the eyepiece is 10 µm for H = 710 µm. The correct value shall be checked by
calibration.
When analyzing images the field of view can take up the entire image area of the camera when applying
the analyzing method K (see 9.3). If this is the case, an appropriate margin correction shall be provided.
8.4 Definition of the pictures of the chart
8.4.1 Size and Shape
The shape of the inclusions is assumed to be an ellipse, see Figures 1 and 2. From this ideal shape the
actual pictures are drawn to have an appearance as realistic as possible with a variation of size and
shape (see Figure 11).
NOTE Small inclusions are only visible in pictures of original size in the official chart, but not in Figure 11.
8.4.2 Parameters
Inclusions can be described using the parameters number n, length L, width w, and area a. The
parameters n, L, and w are measured or estimated directly, whereas a is calculated using the data in
Table 2.
8.4.3 Arrangement of the pictures
The pictures of the chart are arranged in horizontal rows q and vertical columns k (see Figure 11).
Columns 1 to 5 contain ellipses with different widths representing elongated inclusions. Column 6
utilizes circles for describing globular inclusions. Columns 7 to 11 present globular particles arranged
as stringers. The dimensions correspond to the values given for Columns 1 to 5. Column 12 shows
different numbers of inclusions per field to replace counting by estimation (see 8.5.2).
The column to the left of Column 1 shows inclusions with a width of 2 µm and a length corresponding to
the maximum length for its row. Above the pictures, the types of the inclusions according to Annex A
are indicated.
The pictures represent upper limits of classes. The class is denoted by the number of row q and the
Column k in this sequence.
EXAMPLE The designation of class 3.4 denotes the class row 3, Column 4.
For details see Annex I.
8.5 Procedure
8.5.1 General
The prepared sample is placed under the microscope, usually at a magnification of 100 : 1. For ease of
use, eyepiece graticules as described in Figures 9 and 10 may be used. In each field of view the
inclusions are classified by shape, arrangement, and size by comparison with the pictures of the chart,
determining first the row and then the column of the class corresponding to the inclusion. A chart in
original size shall be used for this comparison, not the pictures in Figure 11. Inclusions may additionally
be classified by colour.
Whether evaluating manually or with image analysis, inclusions may equally be rated by measur
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