SIST EN 3973:2009

Overview

EN 3973:2006 is a CEN aerospace material standard that specifies requirements for steel FE-CM3801 (X5CrNiCuNb16-4) produced by investment casting (lost‑wax process) for aerospace applications. The standard covers castings with a maximum effective diameter De ≤ 50 mm supplied in a homogenized, solution treated and precipitation hardened delivery condition and requiring a minimum tensile strength Rm ≥ 1 030 MPa.

Key topics and requirements

• Material designation & chemistry: Steel FE-CM3801 (X5CrNiCuNb16-4) with specified limits for C, Si, Mn, P, S, Cr, Ni, Cu, N, Nb+Ta (see standard for full table).
• Melting & production: Air-melted, cast from remelting stock; form specified as investment casting (lost-wax).
• Size limit: Effective diameter De ≤ 50 mm (properties for De > 25 mm may require agreement between purchaser and manufacturer).
• Delivery condition: Homogenized, solution treated and precipitation hardened; heat-treatment sequence is defined (e.g., homogenize at 1 150 °C / solution treat ~1 040 °C / precipitation at 540 °C – see standard for exact cycles).
• Mechanical properties: Minimum proof stress Rp0.2 ≥ 900 MPa, tensile strength Rm ≥ 1 030 MPa, elongation A and reduction of area Z minimums, and hardness ≥ 34 HRC.
• Microstructure & defects: δ‑ferrite content ≤ 15 %; requirements for internal/external defects and weld repair follow EN 2103-3.
• Testing & inspection: Specified test specimens, batch testing, dimensional and marking inspection per EN 2103-3 and related documents.
• Product qualification: Qualification program to be agreed between manufacturer and purchaser.

Practical applications

• Intended for aerospace components where very high strength, good toughness and stability after precipitation hardening are required - examples include small high‑stress cast parts in airframes, actuators, hydraulic components and engine accessories (typical applications depend on design and qualification).
• Applicable where investment casting geometry and fine detail are needed together with high mechanical performance.
• Useful for procurement specifications, engineering design data sheets, quality assurance and certification of cast aerospace steels.

Who uses this standard

• Aerospace materials engineers and metallurgists
• Foundries and investment casting manufacturers supplying aerospace parts
• Procurement and quality assurance teams writing purchase specifications
• Certification and testing laboratories performing mechanical and microstructural verification

Related standards

• EN 2103-3 (pre‑production and production castings technical specification)
• EN 3484 (remelting stock and reference heat treatment)
• EN 4258 (organization of aerospace metallic material standards)
• EN 4436 (δ‑ferrite test method)
• EN 4500‑5 (rules for drafting/presentation of steel standards)

Keywords: EN 3973, FE-CM3801, X5CrNiCuNb16-4, aerospace steel, investment casting, precipitation hardened, homogenized, solution treated, Rm ≥ 1030 MPa, De ≤ 50 mm.