Determination of content of nonmetallic inclusions in steel - Micrographic method using standard diagrams
1 Scope
This document provides information on the principle, sampling, preparation of specimens, determination, expression of results and test reports for the assessment of nonmetallic inclusions in steels using standard diagrams, as well as the image analysis method for the determination of nonmetallic inclusions (see Annex B).
This document is applicable to determining the nonmetallic inclusions in rolled or forged steel products having a reduction ratio of at least 3.
Note: For certain types of steel (e.g. free cutting steels), the standardized diagrams described in this document may not be applicable.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 13298 Inspection methods of microstructure for metals
GB/T 30067 Standard terminology relating to metallography
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 30067 and the following apply.
3.1
nonmetallic inclusions
a class of components in steel
Note: They are formed during smelting, solidification and cooling, and change in morphology during subsequent cold and hot working. They usually have nonmetallic properties, such as oxides, sulfides and silicates.
3.2
morphological ratio
ratio of length to width of a single particle
3.3
diameter
maximum size of globular particle
Note: Generally, it is the maximum Feret's diameter (see Figure 1).
Key:
f——maximum Ferret circle;
g——globular particle;
Im——maximum Feret's diameter.
Figure 1 Schematic diagram for diameter
4 Principle
4.1 According to the shape and distribution of the nonmetallic inclusions (inclusions), the five groups representing the most commonly observed inclusions are as follows:
——Group A (sulfide type): highly malleable, individual grey particles with a wide range of morphological ratio and generally rounded ends;
——Group B (aluminum oxide type): numerous non deformable, angular, low morphological ratio (generally < 3), black or bluish particles (at least three) aligned in the rolling direction;
——Group C (silicate type): highly malleable, individual black or dark grey particles with a wide range of morphological ratio (generally ≥ 3) and generally sharp ends;
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Sampling
6 Preparation of specimens
7 Methods for determination
8 Expression of results
9 Test report
Annex A (Informative) Technical differences between this document and ISO 4967:2013 and their justifications
Annex B (Informative) Relationship between chart diagram indexes and inclusion measurements
Annex C (Normative) Chart diagrams for inclusion groups A, B, C, D and DS
Annex D (Informative) Example of inclusion assessment
Annex E (Informative) Expression of assessment results by Method B
