EN 4347:2007

Overview

EN 4347:2007 is a European standard developed by CEN that specifies the technical requirements for aerospace-grade Steel FE-PM1506 (X3CrNiMoAl13-8-2). This steel is vacuum induction melted (VIM) and consumable electrode remelted (CEM), delivered in a softened condition as forging stock with dimensions a or D ≤ 300 mm. It is intended for critical aerospace applications where high-performance steel with superior metallurgical cleanliness, mechanical properties, and dimensional accuracy is essential.

This standard forms part of the broader EN series for aerospace metallic materials, ensuring consistency and traceability across the aerospace supply chain. The careful control of chemical composition, heat treatment, microstructure, and testing protocols makes FE-PM1506 steel ideal for demanding aerospace structural components and forgings.

Key Topics

• Material Designation & Composition
  Steel FE-PM1506 corresponds to the alloy X3CrNiMoAl13-8-2. The standard defines maximum concentrations for elements such as carbon, silicon, manganese, phosphorus, sulfur, chromium, molybdenum, nickel, aluminum, nitrogen, and titanium. Chemically controlled to ensure optimal corrosion resistance and mechanical strength for aerospace use.

• Manufacturing Process
  The steel is produced via vacuum induction melting combined with consumable electrode remelting. This process achieves exceptional cleanliness, removing impurities and gas inclusions, critical for aerospace-grade materials to improve fatigue resistance and structural integrity.

• Mechanical Properties
  EN 4347 mandates minimum mechanical properties, including:

  • Proof stress (Rp0.2) ≥ 1300 MPa
  • Tensile strength (Rm) ≥ 1400 MPa
  • Elongation ≥ 8-9%
  • Reduction of area ≥ 40-50%
  • Hardness limits to ensure suitable ductility (≤ 363 HB for softer stock, ≥ 400 HB after heat treatment)
  • Impact toughness requirements to ensure reliability in service

• Heat Treatment & Microstructure
  The steel stock is delivered softened and can be solution treated and precipitation hardened as per aerospace specifications (830 °C to 930 °C solution treatment followed by aging). The δ-ferrite content is strictly controlled to not exceed 2%, preventing adverse effects on toughness and corrosion resistance.

• Testing and Inspection
  EN 4347 references companion standards for macrographic inspection, ultrasonic testing for internal defects, determination of δ-ferrite content, dimensional tolerances, and marking requirements. This rigorous testing ensures only defect-free forging stock is supplied.

• Dimensional Scope
  The standard applies to forging stock with dimensions limited to a or D ≤ 300 mm, suitable for components where precise size and metallurgy control are mandatory.

Applications

Steel FE-PM1506 as defined by EN 4347:2007 is widely used in aerospace structural forgings and components requiring:

• High strength-to-weight ratio for airframe and engine parts
• Excellent corrosion resistance and fatigue performance in critical environments
• Components subjected to mechanical stresses and varying temperature conditions
• Safety-critical applications including landing gear parts, turbine disks, and fastening elements

Its vacuum induction melted and consumable electrode remelted processing routes ensure microcleanliness essential for aerospace performance and lifecycle reliability.

Related Standards

EN 4347:2007 integrates with and references several other aerospace material standards, including:

• EN 2157-2 - Forging stock and forgings technical specifications for aerospace steels
• EN 2003-7 - Macrographic testing methods for aerospace steels
• EN 4050-1 - Ultrasonic inspection methods for bars, plates, forging stock, and forgings
• EN 4436 - Methods for δ-ferrite content determination in aerospace steels
• EN 2043 - General requirements for semi-finished aerospace metallic products
• EN 4258 - General organization of standardization for aerospace metallic materials
• EN 4500-5 - Rules for drafting and presentation of steel material standards

These standards collectively ensure comprehensive quality assurance, traceability, and interoperability across the aerospace manufacturing and supply chain.

Keywords: EN 4347:2007, aerospace steel, FE-PM1506, X3CrNiMoAl13-8-2, vacuum induction melted steel, consumable electrode remelted, aerospace forging stock, mechanical properties steel aerospace, aerospace material standard, metallurgical cleanliness, steel forging stock, aerospace components