SIST EN 4629:2014

Overview

SIST EN 4629:2014 is a European Standard developed by CEN that specifies the requirements for Steel X4CrNiMo16-5-1 (1.4418) used in aerospace applications. This standard covers air melted, softened forging stock with a maximum diameter (De) of 300 mm. It forms part of the aerospace series standards focused on metallic materials, ensuring consistent quality and performance of steel components within the industry.

This steel grade, also known under the designation Z 8 CND 17-04, is characterized primarily by its chemical composition, mechanical properties, and manufacturing process. SIST EN 4629:2014 outlines rigorous chemical, microstructural, mechanical, and inspection criteria tailored for aerospace forging stock.

Key Topics

• Material Specification

  • Steel grade: X4CrNiMo16-5-1 (1.4418)
  • Air melted for high purity and quality
  • Softened condition to optimize forging usability
  • Dimensional limit: Diameter ≤ 300 mm

• Chemical Composition

  • Precise control of elements such as carbon (max 0.06%), chromium (15.00 - 17.00%), molybdenum (0.80 - 1.50%), and nickel (4.00 - 6.00%)
  • Additional control on manganese, silicon, phosphorus, sulfur, and nitrogen to meet aerospace performance demands

• Mechanical Properties and Heat Treatment

  • Proof stress (Rp0.2): minimum 700 MPa
  • Tensile strength (Rm): 900 to 1,050 MPa
  • Elongation: minimum 16% in elongation and impact strength ≥ 120 J at 20 °C
  • Delivery condition code U (softened), with heat treatment details aligned to aerospace quality requirements

• Quality and Inspection Requirements

  • Microstructural examination for inclusion content and grain size
  • Ultrasonic inspection for internal defects (EN 4050-4 acceptance criteria)
  • Macro and micro examination protocols consistent with EN 2950 and EN 2951
  • Maximum delta ferrite content of 5% according to AMS 2315

• Testing Standards Referenced

  • EN 4700-005 for technical specifications
  • EN 4258 for general aerospace material standardization framework
  • EN 4500-005 and EN ISO 643 for presentation of material standards and grain size measurement

Applications

SIST EN 4629:2014 steel X4CrNiMo16-5-1 is ideally suited for aerospace forging stock applications, where high strength, corrosion resistance, and toughness are vital. Typical uses include:

• Aircraft structural components requiring reliable mechanical properties and fatigue resistance
• Engine parts exposed to elevated temperatures and demanding service conditions
• Landing gear forgings and safety-critical aerospace assemblies
• Components where precise chemical composition and controlled microstructure directly influence performance and durability

The standard's rigorous specifications ensure that forged steel parts meet the critical demands of the aerospace industry, supporting safe and efficient aircraft operations.

Related Standards

SIST EN 4629:2014 is part of the broader framework of EN aerospace metallic material standards, which collectively ensure comprehensive coverage for materials used in aviation and space technologies. Important related standards include:

• EN 4258 – General organization of aerospace metallic materials standardization
• EN 4700-005 – Technical specifications for steel and heat resisting alloys forging stock
• EN 2951 – Micrographic determination of non-metallic inclusions in aerospace metals
• EN 4050-4 – Ultrasonic inspection for bars, plates, forging stock, and forgings
• EN ISO 643 – Micrographic grain size determination for steel materials

These interconnected standards ensure that aerospace materials maintain consistent quality, traceability, and performance, aligning with international aerospace industry requirements.

Keywords: SIST EN 4629:2014, aerospace steel standard, X4CrNiMo16-5-1, steel forging stock, air melted steel, aerospace forging stock standard, aerospace steel chemical composition, aerospace steel mechanical properties, steel for aerospace applications, forged steel aerospace component standards, CEN aerospace standards.