Specifications for cast irons in practice: When specifying cast irons for design and procurement, which property is commonly used as the basis of designation in standards and catalogs?

Introduction / Context:
Cast irons encompass a family of high-carbon iron–carbon–silicon alloys (e.g., gray, ductile, malleable irons) used for excellent castability, damping, and compressive strength. Standard designations help engineers select grades with predictable properties.

Given Data / Assumptions:

• Commercial standards (e.g., FG 200, EN-GJL-200) label grades by minimum tensile strength.
• Other data like hardness, microstructure, and composition are also important but not the primary naming convention.

Concept / Approach:
In many standards, gray irons are designated by their minimum tensile strength in MPa (e.g., 200 MPa). Ductile irons similarly are labeled by tensile strength and sometimes elongation requirements. While composition affects properties, end users rely on guaranteed mechanical property minima, especially tensile strength, for selection and design.

Step-by-Step Solution:
Identify industry practice of labeling: “FG 200” implies gray iron with 200 MPa minimum tensile strength.Recognize that mechanical property-based designation is more practical than exact carbon content for performance.Select tensile strength as the correct basis of specification.

Verification / Alternative check:
Standards (e.g., ISO/EN, ASTM) specify minimum tensile strength and other mechanical requirements for cast irons; compositions are typically ranges rather than precise values.

Why Other Options Are Wrong:

• Carbon content alone does not uniquely define microstructure or properties.
• Hardness can correlate but is not the sole naming basis.
• Manufacturing process is important but not the designation key in catalogs.

Common Pitfalls:
Over-reliance on composition without considering microstructure; cooling rate and inoculation strongly influence final properties.

Final Answer:
Tensile strength (minimum)