Overview
ISO 19960:2023 defines graded cast steels and alloys selected for special physical properties - specifically materials used when low linear thermal expansion, low ferromagnetic response, or low galling behaviour is required. The third edition (2023) updates grade listings, chemical composition limits, mechanical property requirements, heat treatments and guidance for verification of physical properties. Annex A provides information on ISO grade designation and similar UNS cast grade numbers.
Key topics and requirements
- Scope and grades: The standard lists specific cast steel and alloy grade designations intended for low-expansion, low-ferromagnetic and low-galling applications (examples include GX3NiCo32, GX1NiCo29–17, GX3Ni36, GX5NiS36 and G‑NiCr13SnBiMo).
- Chemical composition: Maximum and minimum mass-fraction limits for key elements (C, Si, Mn, Cr, Ni, Co, Mo, N, etc.) are specified for each grade to ensure intended physical behaviour.
- Mechanical properties: Tensile strength, yield (Rp0.2) and impact energy requirements are defined up to maximum ruling thickness; some low‑expansion grades list typical physical values instead of standard mechanical properties.
- Heat treatment: Prescribed solution anneal or tempering cycles are given per grade (e.g., solution anneal ranges and quench; some Ni‑Co and Ni grades receive quench + temper).
- Welding and fabrication: Welding procedures are to follow ISO 11970; fabrication and delivery follow ISO 4990 general requirements.
- Verification of physical properties: Measurement methods and acceptance criteria for properties such as coefficient of thermal expansion or magnetic permeability are to be agreed between manufacturer and purchaser. Typical coefficient‑of‑expansion values are provided for some grades.
- Supplementary requirements: Additional purchaser options are available via ISO 4990 subclauses and other agreed requirements.
Applications and users
ISO 19960 is practical for:
- Foundries and casting manufacturers specifying and producing castings with controlled expansion, magnetic and tribological behaviour.
- Design and materials engineers in aerospace, precision instruments, optics, metrology, power generation, medical devices (MRI-compatible components), sensors and electrical equipment where dimensional stability or low magnetic response is crucial.
- Procurement and quality teams needing standardized grade designations, composition limits and testing rules for acceptance criteria.
- Welding and fabrication engineers who must apply approved procedures for these special alloys.
Typical applications include precision housings, reference standards, magnetic‑sensitive enclosures, wear‑resistant sliding parts and anti‑galling fasteners.
Related standards
- ISO 4990 - Steel castings: general technical delivery requirements
- ISO 11970 - Specification and qualification of welding procedures for production welding of steel castings
- EN 10027 series - Steel designation systems (referenced for grade naming and numbering)