Overview
EN ISO 3506-7:2025 specifies the mechanical and physical properties of flat washers made from corrosion-resistant stainless steel, including austenitic, ferritic, and duplex grades. Developed by CEN and aligned with ISO 3506-7:2024, this international standard is part of the widely recognized ISO 3506 series addressing fasteners’ durability, strength, and resistance to corrosion.
This standard applies to flat washers designed for use in bolted joints, typically in combination with bolts, screws, studs, and nuts of corresponding property classes as defined in ISO 3506-1 and ISO 3506-2. Washers outlined in this document include plain, square, square-hole washers, and shaped plates, whether captive or non-captive. The focus is on washers with thicknesses ranging from 0.2 mm to 6 mm, intended for applications where corrosion resistance and specified mechanical properties are crucial.
Key Topics
- Material Grades: Covers austenitic, ferritic, and duplex stainless steel washers, each offering distinct mechanical and corrosion-resistant properties.
- Property Classes: Establishes property classes (e.g., 100HV, 200HV, 300HV) based on minimum Vickers hardness values, allowing for selection according to mechanical requirements.
- Designation System: Introduces a unified designation combining steel grade and property class for clear specification and traceability (e.g., A2-100HV).
- Compatibility: Recommends washer and fastener combinations to ensure optimal corrosion resistance and mechanical performance in bolted joints.
- Inspection and Testing: Defines requirements for hardness testing, inspection processes by manufacturers, suppliers, and purchasers, as well as marking and labelling.
- Corrosion Resistance: Offers guidelines for selecting stainless steel grades based on the operating environment, supporting performance in corrosive conditions.
- Surface Condition: Addresses finish, passivation, and lubrication recommendations to maximize resistance to wear and galling.
Applications
EN ISO 3506-7:2025 is essential for industries and applications where structural integrity and corrosion resistance of bolted joints are critical. Common uses include:
- Construction and Infrastructure: Ensures safe, reliable bolted connections in buildings, bridges, and public works, especially in outdoor or marine environments.
- Mechanical Engineering: Provides durable fastening solutions for machinery, equipment, and automotive assemblies exposed to moisture or aggressive atmospheres.
- Energy and Utilities: Applies to fastener assemblies in power plants and renewable energy installations, where environmental exposure demands robust corrosion-resistant hardware.
- Chemical and Food Processing: Supports safe assemblies in systems requiring high hygiene and corrosion resistance, such as pipelines, tanks, and process machinery.
- General Manufacturing: Offers standardized solutions for various sectors where stainless steel washers enhance joint longevity and reduce maintenance.
Related Standards
EN ISO 3506-7:2025 is part of a comprehensive series addressing fastener materials and properties:
- ISO 3506-1: Mechanical properties for bolts, screws, and studs made from corrosion-resistant stainless steel.
- ISO 3506-2: Mechanical properties for nuts with specified grades and property classes.
- ISO 3506-6: General rules for selecting stainless steels and nickel alloys for fasteners, including detailed information on corrosion behavior and magnetic properties.
- ISO 6507-1: Vickers hardness test method, referenced for washer hardness verification.
- ISO 16228: Documentation and inspection requirements for fasteners.
Meeting the requirements of EN ISO 3506-7:2025 ensures that washers contribute to the overall mechanical reliability and corrosion resistance of fastened assemblies, supporting industries in achieving high safety, durability, and compliance with European and international best practices.
