The chart pictures defined by this European Standard are based on the shape of inclusions and for each shape on length, width and area, for columns 1 to 10 and number for column 11.. By
General
4.1.1 particle single precipitate, in general non-metallic
Inclusion refers to the general classification of particles based on their size and proximity It encompasses both single, isolated particles and configurations of at least two particles, provided that the distance \( t \) is less than or equal to 10 µm and the distance \( e \) is less than or equal to 40 µm, with the main axes of the particles aligned within ± 10° In the case of two globular particles, each is treated as a distinct inclusion.
Inclusions can be created by multiple stringers when the distances \( t \) and \( e \) are less than or equal to 10 Å and 40 Å, respectively Additionally, particles with lengths less than 3 Å or widths less than 2 Å are excluded from consideration.
When elongated and spherical particles are combined, they are typically regarded as a single inclusion, as illustrated in Figure 2d In scenario 4, the width of the largest particle is used to determine the width of the inclusion.
4.1.3 stringer arrangement of at least 3 particles, normally aligned, forming an inclusion (see Figures 2b, 2f), For examples see Annex C and Figure 2f
4.1.4 test area area on the polished surface of the specimen to be evaluated
NOTE In general, the size of the test area is 200 mm 2
Proximity
4.2.1 distances between particles distance e between the particles in the direction of main deformation and distance t in the direction perpendicular to it (see Figure 2a)
4.2.2 distance between stringers similar to that for the distance between particles (see Figure 2b)
4.2.3 scattered random arrangement of particles
NOTE For example see Annex C This is defined in one field of view
Parameters
4.3.1 length dimension of an inclusion in the main direction of deformation, always assumed to be greater than the width
4.3.2 diameter maximum dimension of inclusion classified according to column 6 (globular inclusion)
Maximum width perpendicular to the direction of principal deformation This is the width of the ellipse inscribed to the confining rectangle and having the same length as the inclusion
For manual evaluation this value can only be estimated The width is the maximum width perpendicular to the direction of principal deformation for inclusions with only one particle
The width w of an inclusion with 2 particles is given by the largest particle (see Figure 2a)
Width of a stringer (see Figure 1b):
The width of a stringer is defined as the width of an ellipse inscribed to the confining rectangle and having the same length as the stringer
Case b) for e < 0 àm, t ≤ 10 àm: is the width of an inclusion out of two stringers defined as the sum of the stringers' widths and the distance t (wtotal = w1 + w2 + t) (see Figure 2b, b)
The width of an inclusion, made up of multiple stringers, is defined by the width of the widest stringer, taking into account the neighboring stringers as illustrated in cases a) and b) in Figure 2b and 2c.
4.3.4 area area of the ellipse inscribed to the confining rectangle and having the same length as the inclusion (see 4.3.3 and Figures 1a, 1b)
4.3.5 shape factor exponent f in the equation
NOTE For details see Annex D
Classes
4.4.1 elongated particles particles with elliptical shape (see Figure 1a)
4.4.2 globular particles circular or rectangular particles classified as column 6
4.4.3 type types of inclusions are separated according to their colour, shape and arrangement and not by chemical composition (see Annex A).
Others
4.5.1 lot unit of material processed at one time and subject to similar processing variables
4.5.2 restricted values values of the average field assessment restricted to inclusions greater than a defined length, shape factor or area
The article outlines various symbols and their corresponding unit designations related to inclusions in materials Key terms include the area of inclusions (a), the width of the plate (b), and the diameter of inclusions (d) It also defines factors such as the interparticle distance along the elongation axis (e) and the shape factor (f) The inclusion index (i) and field index (j) are specified, along with the number of assessed particles (n) and inclusions (n s) per specimen Different types of inclusions are categorized by color and shape, including black (b), grey (g), and colored (h) inclusions, as well as various types of aligned and scattered inclusions denoted by Greek letters The article emphasizes the importance of these parameters in understanding material properties and inclusion characteristics.
A àm 2 area of field of view on the specimen
MD main direction of deformation (e g rolling direction)
E mm length of test area
H àm length of measuring frame on the specimen
I length of an stage micrometer
K - , àm, àm 2 /mm 2 average field assessment
M -, àm, àm 2 /mm 2 worst field assessment
W mm width of test area (see Figure R.1)
Combined symbols can be written as index or on one line
EXAMPLE K L ,KL average field assessment for length; n j , nj number of inclusions in a field; n j, jn average number of inclusions per field
General
Unless otherwise specified in the technical delivery conditions, the following requirements apply.
Minimum reduction
The shape of inclusions in steel is significantly influenced by the degree of reduction The chart is applicable only when the inclusion shapes in the specimen can be matched with those illustrated in the chart's images.
It is advisable for products to achieve a minimum reduction factor of five If the deformation is below this threshold, it is crucial to distinguish between porosity and inclusions, as both may occur simultaneously.
Size and location of test area
The specimen's polished surface for inclusion content determination must cover at least 200 mm², with dimensions exceeding 20 mm in length and 10 mm in width (e.g., 25 mm × 20 mm) Within this area, a rectangular test zone of 200 mm² should be defined, maintaining a length-to-width ratio of 2 (e.g., 20 mm × 10 mm) Additionally, the longer side of the test area must align parallel to the main deformation direction, such as the 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 is defined as follows: for bars or billets with a diameter exceeding 50 mm, the test area is positioned halfway between the outer surface and the center; for bars with a diameter greater than 25 mm but less than or equal to 50 mm, the examination surface includes half of the diametral section from the center to the edge; for bars with a diameter of 25 mm or less, the entire diametral section must be examined, ensuring a total surface area of 200 mm²; and for plates with a thickness of less than 25 mm, the specimen must encompass the full thickness.
For thin products one sample could comprise several specimens In this case the test area is smaller than 200 mm 2 per specimen
For any other product, the sampling procedures shall be subject to agreement between parties.
Number of specimens
To accurately assess the inclusion content in a cast or batch, it is essential to test multiple specimens rather than relying on a single sample In the absence of specific guidelines in the product standard or a special agreement, a minimum of six specimens should be analyzed to determine the inclusion content effectively.
Preparation of specimens
To prepare a specimen for examination, it must be cut to create a flat surface To prevent rounding of the edges during polishing, the specimen can be held mechanically or mounted securely.
When polishing specimens, it is crucial to prevent tearing or deformation of inclusions and to maintain a clean polished surface to preserve the appearance of small inclusions Using diamond paste is recommended for polishing, while the choice of lubricant should be based on the type of inclusion, as water may not be suitable for certain inclusions like sulfides Additionally, care must be taken to avoid pressing any grinding or polishing particles into the surface In some instances, hardening the specimen before polishing may be necessary to retain the inclusions effectively.
Magnification
The magnification G is determined solely by the dimensions of the measuring square frame on the specimen To utilize the chart with varying magnifications, the length H of the measuring frame's side must be one of the following values: H = 350 àm, H = 710 àm, or H = 1,410 àm.
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
The standard length of 710 àm should be utilized unless otherwise specified If this value cannot be applied, alternative magnifications may be used, but they must be documented It is important to maintain a consistent magnification throughout a single measurement.
In order to differentiate particles after their grey tone/color, scanning is permissible The smallest particles to be determined should be mapped at at least 10 pixels.
Field of view
At a magnification of H = 710 àm, the square frame is represented by an etched glass in the eyepiece graticule, as shown in Figure 4a For broad field microscopes, an alternative etched glass, illustrated in Figure 4b, can be utilized.
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 àm for H = 710 àm The correct value must be checked by calibration
In image analysis, the field of view may encompass the entire camera image area when utilizing the analyzing method K (refer to section 8.3) In such instances, it is essential to implement a suitable margin correction.
Definition of the pictures of the chart
Size and Shape
The inclusions are modeled as ellipses, as illustrated in Figure 1 Actual images are then created to closely resemble these ideal shapes, incorporating variations in size and form (refer to Figure 5) The guidelines for creating these images are detailed in Annex H.
NOTE Small inclusions are only visible in pictures of original size in the official chart, but not in Figure 5.
Parameters
For manual evaluation, the parameters including the number of inclusions (n), length (L), width (w), and area (a) are considered These parameters can be calculated or estimated from the images provided in Table 2 (refer to clause 8).
Arrangement of the pictures
The chart images are organized into horizontal rows (q) and vertical columns (k) Columns 1 to 5 feature ellipses of varying widths to represent elongated inclusions, while Column 6 uses circles to depict globular inclusions Columns 7 to 10 display globular particles arranged in stringers, with dimensions corresponding to those in columns 1 to 5 Finally, Column 11 illustrates different counts of inclusions per field, serving as an estimation method instead of direct counting.
The unnumbered squares on the left represent inclusions with a width of 2 µm, while the inclusions at the top have a length of 3 µm, both serving as the lower limits for evaluation Below the images, the types of inclusions are categorized according to Annex A.
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 this comparison, an original-sized chart will be utilized instead of the images from Figure 5, which represent the upper limits of the classes (refer to clause 3 and Annex K) To facilitate easier comparisons, eyepiece graticules can be employed (see Figure 4) It is important to note that the scale dimensions are accurate only for the specific magnification for which the eyepiece was designed.
In addition to their size, inclusions may be classified by the colour, shape and arrangement (see Annex A)
7.4.2 Several inclusions of mixed sizes in one field
To simplify the manual evaluation where many inclusions occur in one field of view, the following approximations can be employed
In evaluating inclusions, a maximum of three stretched inclusions are assessed individually, while additional inclusions are analyzed in three steps First, inclusions longer than a quarter of the longest inclusion are evaluated separately Second, the average length and width of the remaining inclusions are calculated Finally, the classification of inclusions is determined based on these parameters, and the total number of inclusions is recorded for the defined class.
Inclusions measuring 11 àm or more are assessed individually For smaller inclusions, the evaluation follows a three-step process: first, inclusions larger than half the diameter of the largest inclusion are evaluated individually; second, the average diameter of the remaining inclusions is calculated, and classification is performed by comparing with images in column 6; finally, the number of inclusions is determined and documented for that classification, which can be estimated using column 11 (refer to Figure 5).
For the worst inclusion assessment and the worst field assessment the whole test area shall be scanned For the average field assessment there are different methods (see 8.3)
Three types of assessments are defined and used in agreement with the customer or the product standard: a) worst inclusion assessment (see 8.1); b) worst field assessment (see 8.2);
For average field assessment, evaluations may focus on inclusions exceeding specified limits based on length, diameter, or area, or be conducted separately for each column These limitations must be clearly outlined in the product standards.
7.4.5 Evaluation of different types of inclusions
This European Standard focuses on the size, shape, and arrangement of inclusions, with colors also considered as additional elements (refer to Annex A) For further details and examples, please consult Annex C Additionally, the classification of inclusion types and their arrangement can be compared with those outlined in other standards (see Annex L).
If there is no other agreement, the parameters and assessments listed in Annex B are taken as default
For recording and final calculations of results it is recommended to use the sheets of Annex M, Annex N and Annex P, or derived arrangements adapted to the needs of the laboratory
As a default, heterogeneous inclusions partly or completely encapsulated (type EAD), shall be considered as one particle
The product standard or agreement between the parties will determine whether inclusions with mixed particles, such as those shown in Figure 2d, are classified as a single particle or two distinct types In the absence of an agreement, inclusions containing both stretched and globular particles will be analyzed based on the predominant shape.
Numbers lower than 10 are exactly quoted with two digits after the comma, all other values are mathematically rounded to integers.
The whole test area must be scanned field by field The field size is H = 710 àm for any case, see clause 7.1
In each test area, only the inclusion with the highest value of the selected parameter (L, d, or a) is assessed and compared with the chart for recording purposes.
To ensure accurate measurements, any inclusion that crosses the measuring frame must be repositioned through stage movement to fit within the frame The evaluation results are determined by calculating the average of the individual values from the assessed specimens.
The equations for this method are given in Annex Q
Assessment and computation sheets with comments and examples are given in Annex M
This evaluation is valid for globular inclusions The assessment is similar to that of P L , but restricted to column 6
Evaluation is conducted by assigning ratings based on area and method P a, with only the largest area being recorded This process involves classifying the data according to length and width, and utilizing the corresponding row and column numbers to extract the area from Table 2.
The value according to Method M is determined by scanning the complete measurement area The field size is H = 710 àm (100 x), for any case (see 7.1)
On each specimen and each type of inclusions only for the field containing the greatest value of the selected parameter (n, L, w or a) the corresponding row and column are recorded
To ensure accurate measurements, any inclusion that crosses the measuring frame must be repositioned through stage movement to fit within the frame The evaluation results are determined by calculating the average of the individual values from the N assessed specimens.
Assessment and computation sheets are given with comments and examples in Annex N The equations this method is based on, are given in Annex Q
8.2.2 Evaluation of M n (rating according to number)
For each specimen only the greatest number of inclusions per field M ns is recorded per inclusion type
If there are few inclusions, they are counted If not, their number can be estimated by using Figure 5, column 11 For N s specimens, M n is the average of the individual values M ns
8.2.3 Evaluation of M L (rating according to length)
For the test areas of each specimen s, the worst field is the one with the maximum accumulated length of a particular inclusion type For one specimen this value is M Ls
The lengths of all inclusions shall be taken into account
For N s specimens, M L is the average of the individual values M Ls
8.2.4 Evaluation of M d (rating according to diameter)
For N s specimens, M d is the average of the individual values M ds evaluated like the values of M Ls
8.2.5 Evaluation of M a (rating according to area)
The worst field is the one with the maximum accumulated area of a particular inclusion type For one specimen this value is M
The K value represents the average of a parameter across a statistically significant number of fields It is determined by scanning the entire test area or until a specified level of confidence is achieved.
The K value can be determined in various ways: for elongated inclusions, it can be calculated based on number (K n), number and length (K n, K L), or number and area (K n, K a); for globular inclusions, it can be calculated using number (K n), number and diameter (K n, K d), or number and area (K n, K a) Additionally, the total number of assessed fields, N j, must include all fields, including those that are empty.
Assessment and computation is carried out for a level of confidence of 60 %, if there is no other agreement or product standard
The equations this method is based on, are given in Annex Q, Annex T and Annex U Assessment and computation sheets are given with comments and examples in Annex P
8.3.2 Scanning of a specimen for average field assessment
The test area can be scanned either randomly or systematically, with the longer side aligned within ± 10° of the vertical direction (y-axis) Random scanning, as outlined in section 8.3.2.3, should only be employed when all inclusions are considered, and not for assessing restricted values.