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GB/T 9441-2021 PDF in English

GB/T 9441-2021 (GB/T9441-2021, GBT 9441-2021, GBT9441-2021)
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GB/T 9441-2021: PDF in English (GBT 9441-2021)

GB/T 9441-2021
ICS 77.080.10
CCS J 31
Replacing GB/T 9441-2009
Metallographic Test Method for Spheroidal Graphite Cast
(ISO 945-4:2019, Microstructure of Cast Irons – Part 4: Test Method for Evaluating
Nodularity in Spheroidal Graphite Cast Irons, MOD)
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative References ... 5
3 Terms and Definitions ... 5
4 Calculation of Nodularity ... 7
5 Metallographic Specimen Preparation ... 7
6 Inspection Rules ... 7
7 Inspection Item ... 8
8 Result Representation ... 12
9 Test Report ... 13
Appendix A (Informative) Compared with ISO 945-4:2019, the Structural Changes of
this Document ... 14
Appendix B (Informative) Technical Differences and Causes between this Document
and ISO 945-4:2019 ... 15
Appendix C (Informative) Classification of Graphite Particle Morphology ... 18
Appendix D (Informative) Reference Form of Typical Graphite Particle Roundness 20
Appendix E (Normative) Rating Chart of Nodularity of Spheroidal Graphite Cast Iron
... 21
Appendix F (Normative) Comparison Chart for Evaluation of Graphite Particle Count
... 26
Appendix G (Normative) Rating Chart of Graphite Particle Size ... 31
Appendix H (Normative) Rating Chart of Pearlite Content ... 33
Appendix I (Normative) Rating Chart of Steadite Content ... 36
Appendix J (Normative) Rating Chart of Carbide Content ... 38
Metallographic Test Method
for Spheroidal Graphite Cast Iron
1 Scope
This Document specifies the nodularity calculation, metallographic sample preparation,
inspection rules, inspection items and rating charts, result representation and inspection report
of spheroidal graphite cast iron.
This Document specifies the methods for evaluating the microstructure of spheroidal graphite
cast iron by visual method and evaluating the nodularity of spheroidal graphite cast ion by
computer image analysis software.
This Document is suitable for evaluating the metallographic structure of spheroidal graphite
cast iron in casting, normalizing and annealing states.
2 Normative References
The provisions in following documents become the provisions of this Document through
reference in this Document. For the dated documents, only the versions with the dates indicated
are applicable to this Document; for the undated documents, only the latest version (including
all the amendments) is applicable to this Document.
GB/T 5611 Foundry Terminology
GB/T 13298 Inspection Methods of Microstructure for Metals
3 Terms and Definitions
For the purposes of this Document, the terms and definitions given in GB/T 5611 and the
following apply.
3.1 Maximum Feret diameter
The maximum straight-line distance lm between any two points on the outline of the outer edge
of the graphite particle.
NOTE: The maximum Feret diameter (lm) is used to represent the graphite particle size, see Figure 1.
4 Calculation of Nodularity
4.1 The nodularity is equal to the area of spheroidal graphite particles (particle roundness ρ ≥
0.60) divided by the total area of all graphite particles, see Formula (2).
Pnod – nodularity, in %;
AVI + AV - the area of graphite particles with a particle roundness ρ≥0.6, or the area of the VI-
shape and V-shape graphite particles shown in Appendix C, in mm2;
Aall - the total area of graphite particles (graphite particles smaller than the critical size and those
cut by the boundary of the field of view are not considered), in mm2;
4.2 See Appendix D for typical graphite particle roundness.
5 Metallographic Specimen Preparation
5.1 The metallographic specimen shall be taken from the test block or casting which is cast at
the same time as the casting and conducted heat treatment in the same furnace (such as during
heat treatment).
5.2 When sampling on castings, the sampling site shall avoid the casting surface and areas
affected by cooling.
5.3 The preparation of metallographic specimens shall be carried out in accordance with the
provisions of GB/T 13298. During the process of intercepting and preparing metallographic
specimens, structure changes, graphite spalling and graphite tailing shall be prevented. The
surface of the specimens shall be smooth and without obvious scratches.
6 Inspection Rules
6.1 Select the field of view randomly; the diameter of the field of view or the equivalent
diameter is 1.20mm. When magnified by 100 times, the graphite particles with the maximum
Feret diameter lm less than 1.0mm are not counted. If a large number of graphite particles are
smaller than 1.0mm or larger than 12.0mm, the magnification can be appropriately enlarged or
reduced to make the size of graphite particles in the field of view as close as possible to the
corresponding rating chart in this Document. The graphite particle count in the field of view is
generally no less than 50 pieces/mm2.
6.2 When inspecting the nodularity, graphite particle size rating and graphite particle count, at
least 5 fields of view shall be selected; and the total number of inspected graphite particles shall
be no less than 500.
6.3 When there are adjacent graphite particles in the inspection field of view that are too close
and the computer-generated images are mixed together, artificial separation measures shall be
taken for the graphite particles.
6.4 When inspecting the steadite and carbide content, first observe the entire inspected surface;
and take the field of view with the most steadite or carbide content as the inspected field of
6.5 When inspecting the content of pearlite, ferrite, steadite and carbide, the area occupied by
graphite particles is not considered.
6.6 When the evaluation results of the image analysis method and the visual method are
different and there is a dispute over the evaluation results, the evaluation results of the visual
method shall prevail.
7 Inspection Item
7.1 Nodularity level
7.1.1 The nodularity level is divided into six levels, see Table 1.
7.1.2 Check the nodularity level of graphite in the polished state; and the magnification is 100
times or adjust the magnification so that the graphite particle size is similar to the rating chart
in Appendix E.
7.1.3 Randomly select the field of view; and compare and evaluate the nodularity level
according to Figure E.1.
7.1.4 When using the image analysis system for evaluation, calculate the nodularity according
to Formulas (1) and (2) in the polished state. The test result is the average value of the
measurement results of all fields of view, rounded-off to an integer.
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.