ISO/TR 945-3:2016

Overview

ISO/TR 945-3:2016 - Microstructure of cast irons - Part 3: Matrix structures is a Technical Report that provides standardized designations, descriptive definitions and reference micrographs for the matrix (metallic) structures found in a wide range of cast irons. The report covers grey, spheroidal (ductile), austenitic, malleable, compacted (vermicular), ausferritic spheroidal and abrasion‑resistant cast irons. Reference micrographs are, unless otherwise noted, produced after etching with 2 % nitric acid in ethanol (Nital).

Keywords: ISO/TR 945-3:2016, microstructure of cast irons, matrix structures, Nital, pearlite, ferrite, austenite, spheroidal graphite.

Key topics

• Standardized matrix designations: Consistent names and short descriptions for common matrix constituents such as ferrite, pearlite, austenite, acicular ferrite, ausferrite, bainite, cementite, ledebureite and martensite.
• Reference micrographs: Photomicrographs at representative magnifications illustrating each matrix type to help visual identification and communication between purchaser and manufacturer.
• Scope by cast‑iron type: Tables mapping matrix structures to material designations for:
  • Grey cast irons (ISO 185)
  • Spheroidal graphite (ductile) cast irons (ISO 1083)
  • Austenitic cast irons (ISO 2892)
  • Malleable cast irons (ISO 5922)
  • Compacted (vermicular) graphite cast irons
  • Ausferritic spheroidal graphite cast irons
  • Abrasion‑resistant cast irons
• Sampling and sample preparation: Practical guidance on sampling location, sample size and metallographic preparation steps (sectioning, grinding, polishing, etching) - with the requirement that matrix examination be carried out in the etched condition to avoid misinterpretation.
• Informative annexes: Assessment aids such as evaluation of pearlite content in spheroidal graphite cast irons (Annex A) and mapping of ISO to European/national material designations (Annex B).

Applications

• Quality control and acceptance of castings - specifying and verifying matrix structure in procurement and inspection reports.
• Metallography and failure analysis - identifying microstructural causes of service failures, wear or brittleness (pearlite vs. martensite vs. bainite, etc.).
• Process development and heat treatment - guiding austempering and other treatments to achieve desired ausferritic or pearlitic matrices.
• Design and material selection - helping engineers choose cast‑iron grades with matrix structures suited to strength, toughness or abrasion resistance.
• Contract and communication - providing unambiguous, visual reference language between foundries and customers.

Who uses this standard

• Foundry metallurgists and quality inspectors
• Materials engineers and design engineers
• Failure analysis laboratories and research teams
• Purchasers specifying cast‑iron components

Related standards

• ISO 945 series (Parts 1 & 2: graphite classification)
• ISO 185, ISO 1083, ISO 2892, ISO 5922 (material designation standards referenced in the report)

This Technical Report is a practical reference for consistent identification and communication of cast‑iron matrix structures in manufacturing, inspection and materials engineering.