ISO 898-3:2018

Overview

ISO 898-3:2018 defines the mechanical and physical properties of flat washers made of carbon steel and alloy steel, intended for use in bolted joints with fasteners specified in ISO 898-1 and ISO 898-2. It standardizes property classes (expressed as a minimum Vickers hardness value, e.g. 200HV, 300HV, 380HV) and sets test, material and marking requirements for plain, square, square-hole and shaped flat washers with thicknesses from 0.2 mm to 12 mm.

Key topics and requirements

• Property classes and designation: Washer classes are denoted by their minimum Vickers hardness followed by “HV” (e.g., 200HV). Guidance is provided for combining washer classes with bolt/nut property classes.
• Materials and chemistry: Applies to carbon and alloy steels (including spring steels). Material selection, heat treatment and chemical limits are specified; manufacturing lots must be from a single cast of raw material.
• Mechanical tests: Hardness testing (Vickers and Rockwell references ISO 6507‑1 and ISO 6508‑1), decarburization and carburization checks, retempering and - for high‑hardness washers - ductility testing (Annex A).
• Temperature guidance: Requirements are evaluated at ambient 10 °C to 35 °C. Washers are typically used in service from −50 °C to +150 °C; consult a fastener expert for applications outside this range up to +300 °C.
• Geometry and scope: Covers captive and non‑captive flat washers (plain with/without knurls, square, square‑hole, shaped plates) within the defined thickness range.
• Exclusions: Corrosion resistance and weldability are not specified by ISO 898‑3; these should be addressed by complementary standards or procurement agreements.
• Marking and traceability: Requirements for product and package marking, including property class identification, are included.

Practical applications

• Ensures consistent washer performance in bolted joints across engineering, automotive, machinery, construction and heavy‑equipment applications.
• Useful when specifying washers to match bolt/nut property classes to avoid joint failure (e.g., preventing washer yielding or excessive hardness mismatch).
• Essential for manufacturers and quality inspectors to verify hardness, decarburization limits and material conformity.
• Helps procurement and design engineers create reliable fastener assemblies where mechanical compatibility and traceability are required.

Who uses this standard

• Fastener manufacturers and heat‑treatment shops
• Design, structural and mechanical engineers
• Quality assurance and inspection teams
• Procurement specialists specifying bolted‑joint components

Related standards

• ISO 898‑1 / ISO 898‑2 (bolts, screws, studs and nuts property classes)
• ISO 6507‑1 (Vickers hardness test) and ISO 6508‑1 (Rockwell hardness test)
• ISO 10644, ISO 10673, ISO 10669 (product standards and tapping screw washer assemblies)

Keywords: ISO 898-3, flat washers, property classes, Vickers hardness, carbon steel washers, alloy steel washers, mechanical properties, fastener standards, bolted joints.