ISO 945-1:2019

Overview

ISO 945-1:2019 - Microstructure of cast irons - Part 1: Graphite classification by visual analysis specifies a comparative visual method to classify the graphite microstructure in cast irons. The standard provides a designation system based on graphite form, distribution and size, supported by reference images (magnification ×100). It is intended as an information and classification method for foundry and metallographic practice, not as a stand-alone acceptance criterion for material suitability or mechanical performance.

Key topics and technical requirements

• Designation system
  • Form: Graphite is classified into Roman numerals I to VI (reference images provided).
  • Distribution: Capital letters A to E indicate distribution - specified for grey cast irons (form I).
  • Size: Numeric scale 1 to 8 denotes particle size classes (reference images and limits given).
• Graphite size ranges (form I examples at ×100 magnification):
  • Size 1: ≥ 1.0 mm
  • Size 2: 0.5 mm to < 1.0 mm
  • Size 3: 0.25 mm to < 0.5 mm
  • Size 4: 0.12 mm to < 0.25 mm
  • Size 5: 0.06 mm to < 0.12 mm
  • Size 6: 0.03 mm to < 0.06 mm
  • Size 7: 0.015 mm to < 0.03 mm
  • Size 8: < 0.015 mm
• Reference images & magnification: Classification uses schematic microstructures and photomicrographs at ×100 magnification (Figures 1–5 and Annexes).
• Sampling & sample preparation
  • Record sample location, wall thickness, distance from surface and presence of chills.
  • Prepare sufficiently large polished areas; careful grinding/polishing is required so graphite retains original form and size. Examination is usually on unetched polished sections.
• Procedure & limits
  • Polished samples are scanned to select representative areas; classification is by visual comparison to the reference images. Results depend on the metallographer’s judgment and do not constitute statistically valid evidence of compliance with material standards.
• Reporting
  • The standard includes designation rules, how to report mixed forms/sizes, and guidance on nodule counts and documentation.

Practical applications and users

Who uses ISO 945-1:2019:

• Foundry quality control and metallography labs
• Materials and metallurgical engineers
• Inspection and incoming-material teams
• Failure analysis and R&D groups

Typical uses:

• Rapid, standardized assessment of graphite microstructure in cast irons
• Process control, microstructure documentation and comparative studies
• Supporting metallographic reports in production and inspection workflows

Note: For contractual acceptance or mechanical-property requirements, refer to the relevant material standards; ISO 945-1:2019 is descriptive and not a substitute for material-grade specifications.

Related standards

• ISO 945 is a multi-part series addressing cast-iron microstructures - consult the ISO catalogue or national standards body for other parts in the ISO 945 series and complementary metallographic standards.