INCLUSION RATING IN STEELS AS PER ASTM STANDARDS

MUHAMMED LABEEB

13MY06

INCLUSIONS

▪ Inclusions are non metallic particles embedded in the steel matrix.

▪ Chemical compounds of metals like (Fe, Mn, Al, Si, Ca etc) with non metals (O,

S, N, C, H)

▪ Examples: SiO2,MnO,MgS,Ce2S3,AlN etc…

▪ Properties: An inclusion is a mismatch with the steel matrix. Both may have

different properties resulting in undesired effect.

INCLUSION RATING

▪ Standard reference charts depicting a series of typical inclusion configurations

(size, type, and number) were created for direct comparison with the microscopic

field of view

▪ Rating is done in comparison with the ASTM standard chart. [Designation: E 45]

▪ Inclusions are assigned to a category based on similarities in morphology, that is,

by size, shape, concentration, and distribution, and not necessarily on their

chemical identity

CLASSIFICATION OF INCLUSIONS

▪ Inclusions are classified into four categories (called Type) based on their

morphology

▪ Each of them are classified into two subcategories based on their width or

diameter

CLASSIFICATION OF INCLUSIONS

categories

A-Sulfide Type

heavy

thin

B-Alumina Type

heavy

thin

C-Silicate Type

heavy

thin

D-Globular Oxide Type

heavy

thin

• Although the categories contain chemical names that imply knowledge of their chemical content, the ratings are based strictly on morphology

• The four categories, or Types, are partitioned into Severity Levels based on the number or length of the particles present in a 0.50 mm2 field of view

CLASSIFICATION OF INCLUSIONS

▪ Type A and C inclusions are very similar in size and shape

▪ They are distinguished based on their colour when viewed under brightfield illumination

▪ Type A-Sulfide are light gray

▪ Type C-Silicate are black

▪ The B-type stringers consist of a number (at least three) of round or angular oxide particles

with aspect ratios less than 2 that are aligned nearly parallel to the deformation axis

▪ The D-type are globular in shape

PROCEDURE

▪ The minimum polished surface area of a specimen for the microscopic

determination of inclusion content is 160 mm2 (0.25 in.2)

▪ Field of view is 0.50 mm2 or square of side 0.71 mm

▪ Either of two techniques may be employed to achieve a

0.50 mm2 field of view

▪ One method is to project the microscope image onto a viewing screen that has a

square mask with 71.0 mm sides drawn on it

▪ Another option is to use a reticle made for the microscope, which will superimpose the

required square mask directly onto the field of view

PROCEDURE

▪ Inclusions are classified into the before mentioned four types

▪ After the inclusions are categorized by Type, they must be categorized by thickness

or diameter- thin and heavy series

▪ After classification by type and thickness, the severity levels are determined for the

inclusions comparing with the chart

▪ These values can be numerically calculated as length or number based on the

limits given in standard Table (given below)

COMPARISON CHART- A (Sulfide type)

COMPARISON CHART- B (Aluminate type)

COMPARISON CHART- C (Silicate type)

COMPARISON CHART- D (Globular type oxides)

PROCEDURE

REFERENCES

▪ R E SMALLMAN – Modern Physical Metallurgy and Materials Engineering

▪ P C ANGELO – Materials Characterization

▪ ASTM E 45 – 05 - Standard Test Methods for Determining the Inclusion Content

of Steel

▪ ASTM E 1245 - Practice for Determining Inclusion or Second-Phase Constituent

Content of Metals by Automatic Image Analysis