ISO/TC 25/WG 3 - Microstructure of graphite

This document specifies a test method for evaluating nodularity in spheroidal graphite cast irons by comparative visual analysis and image analysis techniques. This document provides figures for different levels of nodularity and graphite particle count of spheroidal graphite cast irons for visual analysis.

ISO/TR 945-3:2016 gives the designations, descriptions and reference micrographs of the matrix structures of cast irons. It applies to the following types of cast irons: - grey cast irons (Table 4.1); - spheroidal graphite cast irons (Table 4.2); - austenitic cast irons (Table 4.3); - malleable cast irons (Table 4.4); - compacted (vermicular) graphite cast irons (Table 4.5); - ausferritic spheroidal graphite cast irons (Table 4.6); - abrasion-resistant cast irons (Table 4.7). Each matrix structure is defined with explanations and micrographs. Unless otherwise stated in Clause 4, the micrographs shown correspond to samples etched with a solution of 2 % nitric acid in ethanol (Nital).

ISO/TR 945-2:2011 deals with the two-dimensional characterisation of graphite form and size in cast irons. A standard method for determining graphite form by image analysis had not been developed at the time of this report, but several methods are in use in the industry. The purpose of ISO/TR 945-2 is to give an illustration of what is possible and to suggest ways in which the technique might develop in the future. ISO/TR 945-2:2011 does not apply to the graphite distribution of grey (lamellar graphite) cast iron as defined in ISO 945-1. ISO/TR 945-2:2011 describes procedures used to carry out image analysis of graphite form and size and provides a method of comparison to the results obtained using visual analysis techniques. It does not specify any particular mathematical description of the graphite forms but provides a means for comparison.

ISO 945-1:2017 specifies a method of classifying the microstructure of graphite in cast irons by comparative visual analysis. The purpose of this document is to provide information about the method of graphite classification. It is not intended to give information on the suitability of cast-iron types and grades for any particular application. The particular material grades are specified mainly by mechanical properties and, in the case of austenitic and abrasion resistant cast irons, by their chemical composition. The interpretation of graphite form and size does not allow a statistically valid statement on the fulfilment of the requirements specified in the relevant material standard.

ISO 945-1:2008 specifies a method of classifying the microstructure of graphite in cast irons by comparative visual analysis. The purpose of this part of ISO 945 is to provide information about the method of graphite classification. It is not intended to give information on the suitability of cast-iron types and grades for any particular application. The particular material grade is specified by results from tensile tests or hardness testing and, in the case of austenitic cast irons, by their chemical composition. The interpretation of graphite form and size does not allow a statistically valid statement on the fulfilment of the requirements specified in the relevant material standard. The structure of the metallic matrix (e.g. ferrite, pearlite) has a significant effect on the material properties. Such an interpretation is not the purpose of this part of ISO 945.