Overview
ISO 11973:2023 specifies the chemical composition and mechanical properties of heat-resistant cast steels and alloys intended for general applications. This third edition updates clause structure and supplementary requirements and provides standardized grade designations, delivery conditions and guidance to support material selection for heat-resistant service.
Key Topics
- Scope: Defines requirements for cast steels and alloys used in heat-resistant service, focusing on composition and mechanical performance at room temperature and guidance on maximum use temperature.
- General conditions of delivery: Materials shall conform to ISO 4990 (General technical delivery requirements) and any purchaser-specified supplementary requirements.
- Heat treatment: A limited set of grades (for example GX40CrSi13, GX40CrSi17, GX30CrSi7, GX40CrSi24, GX40CrSi28, GX130CrSi29) may be annealed at 800 °C to 850 °C; some grades can be supplied as-cast. Any additional heat treatment must be agreed between manufacturer and purchaser.
- Chemical composition: Table 1 in the standard lists mass fraction limits for C, Si, Mn, P, S, Cr, Mo, Ni and other elements for each grade. These compositional limits are mandatory for conformity.
- Mechanical properties and testing: Table 2 provides required mechanical properties (yield/offset, tensile, elongation, hardness limits where applicable) and indicates tests to be performed at room temperature if agreed between manufacturer and purchaser.
- Maximum use temperature: The standard includes indicative maximum use temperatures for oxidising environments to aid grade comparison; actual selection must consider service environment and mechanical loading.
- Supplementary requirements: A standardized list is referenced from ISO 4990 for optional purchaser requirements.
- UNS equivalents: Annex A provides comparable UNS cast-grade numbers for many ISO grades to help cross-reference specifications.
Applications
ISO 11973:2023 is intended to guide engineers, material specifiers, foundry producers and procurement professionals when selecting heat-resistant cast steels and alloys for general high-temperature service. Typical, illustrative applications include:
- High-temperature components in furnaces and boilers
- Heat-resistant cast parts in metallurgical and chemical process equipment
- Components exposed to oxidising high-temperature environments where predictable mechanical performance is required
Use the standard to compare grades, confirm composition and hardness limits, and define contractual requirements for delivery and testing.
Related Standards
- ISO 4990 - Steel castings: General technical delivery requirements (normative reference in ISO 11973)
- EN 10027-1 / EN 10027-2 - Designation systems referenced for grade naming and numbering
For procurement and conformity, follow the clauses in ISO 11973:2023 and coordinate supplementary requirements and any special heat treatments with manufacturers.