Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization — Part 1: Rules for the structure and drafting of standardizing documents.
This standard replaces GB/T 9441-2009 Metallographic test for spheroidal graphite cast iron. In addition to structural adjustments and editorial changes, the following main technical changes have been made with respect to GB/T 9441-2009:
——The terms of maximum Féret diameter (see 3.1) and particle roundness (see 3.2) have been added;
——The Formula for calculating the graphite particle roundness has been added (see 3.2);
——The terms of spheroidal graphite (see 3.3) and graphite particle count (see 3.6) have been added;
——Requirements for sampling of casting body have been added (see 5.2);
——The definition and calculation Formula of nodularity of spheroidal graphite cast iron have been changed (see 4.1; 4.1.1 in 2009 edition);
——The grading and evaluation methods for nodularity have been changed (see 7.1; 4.1 in 2009 edition), and the reference image for nodularity has been changed (see Annex E; Figures 1-6 of 4.1.1 in 2009 edition);
——The method for evaluating nodularity by image analysis has been changed (see 7.1.4; 4.1.4 in 2009 edition);
——The distributed ferrite quantity classification has been deleted (see 4.4 of 2009 edition);
——The reference images for nodularity in spheroidal graphite cast irons have been added (see Annex E);
——The reference images for graphite particle count have been added (see Annex F);
——The reference images for graphite particle size have been changed (see Figure G.1; Figures 1-12 of 4.2.3 in 2009 edition);
——The reference images for pearlite content have been added (see Annex H);
——The reference images for iron phosphide eutectic content have been added (see Annex I);
——The reference images for carbide content have been added (see Annex J);
This document has been redrafted and modified in relation to ISO 945-4: 2019 Microstructure of cast irons — Part 4: Test method for evaluating nodularity in spheroidal graphite cast irons. This document is changed largely from ISO 945-4: 2019 in structure; the comparison between this document and ISO 945-4: 2019 in clause number is listed in Annex A. See Annex B for other technical changes and reasons with respect to ISO 945-4: 2019.
The following editorial changes have been made with respect to ISO 945-4: 2019:
——The name of the document has been changed from ISO 945-4: 2019, Microstructure of cast irons — Part 4: Test method for evaluating nodularity in spheroidal graphite cast irons to Metallographic test method for spheroidal graphite cast iron.
——Annexes A, B and C have been added.
This document was proposed by and is under the jurisdiction of the National Technical Committee on Foundry of Standardization Administration of China (SAC/TC 54).
The previous editions of this document are as follows:
——It was first issued as GB/T 9441-1988 in 1988, first revised in 2009;
——This edition is the second revision.
Metallographic test method for spheroidal graphite cast iron
1 Scope
This document specifies the calculation of nodularity, metallographic sample preparation, inspection rules, test items and reference images, result representation and test report of spheroidal graphite cast iron.
This document specifies the visual inspection for evaluating the microstructure of spheroidal graphite cast irons and the method of evaluating nodularity in spheroidal graphite cast irons by computer image analysis software.
This document is applicable to evaluating the metallographic structure of as-cast, normalized and annealed spheroidal graphite cast iron.
2 Normative references
The following referenced documents are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB 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, as well as the following definitions, apply.
3.1
maximum Féret diameter
maximum length lm of an object whatever its orientation
Note to entry: The maximum Féret diameter (lm) is used to indicate the size of graphite particles, as shown in Figure 1.
Figure 1 Illustration of maximum Féret diameter of graphite particle
3.2
particle roundness
area of a graphite particle divided by the area of the circle where the diameter is the maximum Féret diameter of the same graphite particle
The roundness of graphite particle is calculated by using Formula (1).
ρ=A/A_m =4A/(π〖l_m〗^2 ) (1)
where:
ρ——the roundness of graphite particle;
A——the area of graphite particle, in mm2;
Am——the circular area of graphite particles with maximum Féret diameter, in mm2;
lm——the maximum Féret diameter, in mm.
3.3
spheroidal graphite
graphite particles with roundness ρ ≥ 0. 60
3.4
spheroidal graphite cast iron
cast material, iron, silicon and carbon-based, the carbon being present mainly in the form of spheroidal graphite particles
3.5
nodularity
Pnod
assessment of the proportion of spheroidal graphite particles in a graphite particle
3.6
graphite particle count
number of graphite particles per unit area
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, as shown in Formula (2).
P_nod=(A_VI+A_V)/A_all (2)
where:
Pnod——the nodularity,%;
AVI+AV——the area of graphite particles with roundness ρ ≥ 0.6, or the area of graphite particle of forms VI or V shown in Annex C, in mm2;
AAll——the total area of graphite particles (excluding the graphite particles less than critical size and graphite particles that intersect the border of the field of view, in mm2.
4.2 See Annex D for the roundness of typical graphite particles.
5 Metallographic sample preparation
5.1 Metallographic samples shall be intercepted on test blocks or cast irons that are poured at the same time as castings and heat treated in the same furnace (such as during heat treatment).
5.2 When sampling on cast irons, the sampling position shall avoid the cast iron surface and the area affected by chilling.
5.3 The preparation of metallographic samples shall be carried out according to GB/T 13298. During the interception and preparation of metallographic samples, the microstructure changes, graphite peeling and graphite tail dragging shall be prevented, and the surface of the samples shall be smooth without obvious scratches.
6 Inspection rules
6.1 The fields of view shall be chosen randomly, and the diameter or equivalent diameter of the field of view is 1.20 mm. When magnified by 100 times, the graphite particles having a maximum Féret diameter lm less than 1.0 mm shall not be taken into account. If most of the graphite particles are less than 1.0 mm or larger than 12.0 mm, the magnification can be appropriately enlarged or reduced, so that the size of graphite particles in the fields of view is as close as possible to the corresponding reference images in this document. The number of graphite particles in a field of view should be at least 50 particles/mm2.
6.2 The nodularity, size of graphite particles and graphite particle count should be evaluated on the basis of at least five fields of view and at least 500 graphite particles.
6.3 When joined/contiguous graphite particles are too close in the inspection field of view and the computer-generated images are mixed into one, artificial separation measures shall be taken for graphite particles.
6.4 When inspecting the content of phosphorus eutectic and carbide, first observe the whole tested surface, and take the field of view with the maximum content of phosphorus eutectic or carbide as the inspected field of view.
Foreword i
1 Scope
2 Normative references
3 Terms and Definitions
4 Calculation of nodularity
5 Metallographic sample preparation
6 Inspection rules
7 Inspection items
8 Expression of results
9 Test report
Annex A (Informative) Structural changes of this document with respect to ISO 945-4:
Annex B (Informative) Technical differences between this document and ISO 945-4: 2019 and their causes
Annex C (Information) Classification of graphite particle forms
Annex D (Information) Reference table of roundness of typical graphite particles
Annex E (Normative) Reference images for nodularity of spheroidal graphite cast iron
Annex F (Normative) Reference images for graphite particle count
Annex G (Normative) Reference images of graphite particle sizes
Annex H (Normative) Reference images of pearlite content
Annex I (Normative) Reference images of iron phosphide eutectic content
Annex J (Normative) Reference images of carbide content
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization — Part 1: Rules for the structure and drafting of standardizing documents.
This standard replaces GB/T 9441-2009 Metallographic test for spheroidal graphite cast iron. In addition to structural adjustments and editorial changes, the following main technical changes have been made with respect to GB/T 9441-2009:
——The terms of maximum Féret diameter (see 3.1) and particle roundness (see 3.2) have been added;
——The Formula for calculating the graphite particle roundness has been added (see 3.2);
——The terms of spheroidal graphite (see 3.3) and graphite particle count (see 3.6) have been added;
——Requirements for sampling of casting body have been added (see 5.2);
——The definition and calculation Formula of nodularity of spheroidal graphite cast iron have been changed (see 4.1; 4.1.1 in 2009 edition);
——The grading and evaluation methods for nodularity have been changed (see 7.1; 4.1 in 2009 edition), and the reference image for nodularity has been changed (see Annex E; Figures 1-6 of 4.1.1 in 2009 edition);
——The method for evaluating nodularity by image analysis has been changed (see 7.1.4; 4.1.4 in 2009 edition);
——The distributed ferrite quantity classification has been deleted (see 4.4 of 2009 edition);
——The reference images for nodularity in spheroidal graphite cast irons have been added (see Annex E);
——The reference images for graphite particle count have been added (see Annex F);
——The reference images for graphite particle size have been changed (see Figure G.1; Figures 1-12 of 4.2.3 in 2009 edition);
——The reference images for pearlite content have been added (see Annex H);
——The reference images for iron phosphide eutectic content have been added (see Annex I);
——The reference images for carbide content have been added (see Annex J);
This document has been redrafted and modified in relation to ISO 945-4: 2019 Microstructure of cast irons — Part 4: Test method for evaluating nodularity in spheroidal graphite cast irons. This document is changed largely from ISO 945-4: 2019 in structure; the comparison between this document and ISO 945-4: 2019 in clause number is listed in Annex A. See Annex B for other technical changes and reasons with respect to ISO 945-4: 2019.
The following editorial changes have been made with respect to ISO 945-4: 2019:
——The name of the document has been changed from ISO 945-4: 2019, Microstructure of cast irons — Part 4: Test method for evaluating nodularity in spheroidal graphite cast irons to Metallographic test method for spheroidal graphite cast iron.
——Annexes A, B and C have been added.
This document was proposed by and is under the jurisdiction of the National Technical Committee on Foundry of Standardization Administration of China (SAC/TC 54).
The previous editions of this document are as follows:
——It was first issued as GB/T 9441-1988 in 1988, first revised in 2009;
——This edition is the second revision.
Metallographic test method for spheroidal graphite cast iron
1 Scope
This document specifies the calculation of nodularity, metallographic sample preparation, inspection rules, test items and reference images, result representation and test report of spheroidal graphite cast iron.
This document specifies the visual inspection for evaluating the microstructure of spheroidal graphite cast irons and the method of evaluating nodularity in spheroidal graphite cast irons by computer image analysis software.
This document is applicable to evaluating the metallographic structure of as-cast, normalized and annealed spheroidal graphite cast iron.
2 Normative references
The following referenced documents are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB 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, as well as the following definitions, apply.
3.1
maximum Féret diameter
maximum length lm of an object whatever its orientation
Note to entry: The maximum Féret diameter (lm) is used to indicate the size of graphite particles, as shown in Figure 1.
Figure 1 Illustration of maximum Féret diameter of graphite particle
3.2
particle roundness
area of a graphite particle divided by the area of the circle where the diameter is the maximum Féret diameter of the same graphite particle
The roundness of graphite particle is calculated by using Formula (1).
ρ=A/A_m =4A/(π〖l_m〗^2 ) (1)
where:
ρ——the roundness of graphite particle;
A——the area of graphite particle, in mm2;
Am——the circular area of graphite particles with maximum Féret diameter, in mm2;
lm——the maximum Féret diameter, in mm.
3.3
spheroidal graphite
graphite particles with roundness ρ ≥ 0. 60
3.4
spheroidal graphite cast iron
cast material, iron, silicon and carbon-based, the carbon being present mainly in the form of spheroidal graphite particles
3.5
nodularity
Pnod
assessment of the proportion of spheroidal graphite particles in a graphite particle
3.6
graphite particle count
number of graphite particles per unit area
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, as shown in Formula (2).
P_nod=(A_VI+A_V)/A_all (2)
where:
Pnod——the nodularity,%;
AVI+AV——the area of graphite particles with roundness ρ ≥ 0.6, or the area of graphite particle of forms VI or V shown in Annex C, in mm2;
AAll——the total area of graphite particles (excluding the graphite particles less than critical size and graphite particles that intersect the border of the field of view, in mm2.
4.2 See Annex D for the roundness of typical graphite particles.
5 Metallographic sample preparation
5.1 Metallographic samples shall be intercepted on test blocks or cast irons that are poured at the same time as castings and heat treated in the same furnace (such as during heat treatment).
5.2 When sampling on cast irons, the sampling position shall avoid the cast iron surface and the area affected by chilling.
5.3 The preparation of metallographic samples shall be carried out according to GB/T 13298. During the interception and preparation of metallographic samples, the microstructure changes, graphite peeling and graphite tail dragging shall be prevented, and the surface of the samples shall be smooth without obvious scratches.
6 Inspection rules
6.1 The fields of view shall be chosen randomly, and the diameter or equivalent diameter of the field of view is 1.20 mm. When magnified by 100 times, the graphite particles having a maximum Féret diameter lm less than 1.0 mm shall not be taken into account. If most of the graphite particles are less than 1.0 mm or larger than 12.0 mm, the magnification can be appropriately enlarged or reduced, so that the size of graphite particles in the fields of view is as close as possible to the corresponding reference images in this document. The number of graphite particles in a field of view should be at least 50 particles/mm2.
6.2 The nodularity, size of graphite particles and graphite particle count should be evaluated on the basis of at least five fields of view and at least 500 graphite particles.
6.3 When joined/contiguous graphite particles are too close in the inspection field of view and the computer-generated images are mixed into one, artificial separation measures shall be taken for graphite particles.
6.4 When inspecting the content of phosphorus eutectic and carbide, first observe the whole tested surface, and take the field of view with the maximum content of phosphorus eutectic or carbide as the inspected field of view.
Contents of GB/T 9441-2021
Foreword i
1 Scope
2 Normative references
3 Terms and Definitions
4 Calculation of nodularity
5 Metallographic sample preparation
6 Inspection rules
7 Inspection items
8 Expression of results
9 Test report
Annex A (Informative) Structural changes of this document with respect to ISO 945-4:
Annex B (Informative) Technical differences between this document and ISO 945-4: 2019 and their causes
Annex C (Information) Classification of graphite particle forms
Annex D (Information) Reference table of roundness of typical graphite particles
Annex E (Normative) Reference images for nodularity of spheroidal graphite cast iron
Annex F (Normative) Reference images for graphite particle count
Annex G (Normative) Reference images of graphite particle sizes
Annex H (Normative) Reference images of pearlite content
Annex I (Normative) Reference images of iron phosphide eutectic content
Annex J (Normative) Reference images of carbide content
