SIST EN 2542:2009

Overview

SIST EN 2542:2009 is a European standard developed by CEN that specifies the requirements for Steel FE-PL1502 (25CrMo4) in an annealed condition. This steel grade is provided in the form of bars and wires with external diameters (De) up to 40 mm specifically for use in prevailing torque nuts in aerospace applications. The standard ensures material quality, chemical composition, mechanical properties, and heat treatment criteria tailored for critical aerospace fasteners that demand high reliability and consistent performance.

This aerospace series metal standard complements a broader range of EN standards for metallic materials and aligns with the organizational framework outlined in EN 4258 and drafting rules per EN 4500-5.

Key Topics

• Material Specification
  • Steel grade: FE-PL1502 (25CrMo4)
  • Annealed condition for optimum machinability and mechanical properties
  • Chemical composition limits for Carbon (C), Silicon (Si), Manganese (Mn), Chromium (Cr), Molybdenum (Mo), and Nickel (Ni)
• Product Forms and Dimensions
  • Bars and wires with maximum diameter (De) of 40 mm
• Mechanical and Physical Properties
  • Hardness range: HRB ≤ 82, HRC between 40 and 43, or HV5 between 390 and 430
  • Other mechanical characteristics such as strength, elongation, and proof stress specified indirectly via referenced norms
• Heat Treatment and Delivery
  • Annealing process as standard delivery condition to ensure uniform properties
  • Prohibits carburization or total decarburization; limited admissible depth of decarburization
• Testing and Qualification
  • Tests aligned with aerospace standards for material consistency
  • Qualification procedures referenced from EN 9133, involving agreements between manufacturer and purchaser for product certification
• Designation and Coding
  • Material and dimensional coding system based on EN 2600 for traceability and standardization

Applications

SIST EN 2542:2009 steel (25CrMo4) in annealed form is primarily intended for aerospace applications that require prevailing torque nuts-a type of locking nut known for its resistance to loosening under vibration and torque stresses. Such nuts are critical in aerospace assemblies, including:

• Aircraft structural components fastening
• Engine mounting hardware
• Control systems and flight-critical assemblies
• Aerospace standard parts where material integrity and dimensional accuracy are essential
• High-reliability nuts designed for vibration resistance and safe operation under dynamic loads

This standard supports manufacturers in producing fasteners that meet the stringent safety, durability, and performance requirements typical of aerospace environments.

Related Standards

SIST EN 2542:2009 integrates with and references several key European aerospace standards, including:

• EN 4258 – Organization and layout for metallic aerospace material standards
• EN 4500-5 – Rules for drafting and presenting steel material standards in aerospace
• EN 2600 – Designation rules for metallic semi-finished products
• EN 4700-2 – Technical specifications for steel wrought products in aerospace applications
• EN 9133 – Qualification procedures for aerospace standard parts, including product certification and quality management

By conforming to SIST EN 2542:2009, manufacturers ensure compatibility and compliance within the European aerospace supply chain, facilitating standardization, quality assurance, and traceability of steel materials used in critical fasteners.

Keywords: aerospace steel standard, FE-PL1502, 25CrMo4 steel, annealed steel bar, annealed steel wire, prevailing torque nuts, aerospace fasteners, aerospace material standards, EN 2542, CEN aerospace standards, steel for aerospace nuts, aerospace quality management, aerospace steel chemical composition, aerospace standard nuts