ISO 3506-7:2024, Fasteners – Mechanical properties of corrosion-resistant stainless steel fasteners – Part 7: Flat washers with specified grades and property classes

This document specifies the mechanical and physical properties of flat washers made of corrosion resistant austenitic, ferritic and duplex stainless steels, designed to be used in bolted joints in combination with bolts, screws, studs and nuts with specified grades and property classes in accordance with ISO 3506-1 and ISO 3506-2.
These types of washers are also used with other stainless steel fasteners such as screws forming their own mating thread (see e.g. ISO 3506-4).
ISO 3506-6 provides general rules and additional technical information on suitable stainless steels and their properties (detailed properties of stainless steel grades, corrosion behaviour with regards to pitting, crevice and intergranular corrosion, magnetic properties, etc.)

This document applies to the following flat non-captive and captive washers with thickness 0,2 mm to 6 mm (see 5.1):
— plain washers and flat washers (with or without knurls, ribs or chamfers),
— square washers,
— square hole washers,
— shaped plates.

The term “washer” is used in the following for all types of washers and plates within the scope of this document.
This document does not specify requirements for functional properties such as weldability.

This document is issued as an addition to the ISO 3506 series to provide a single point of reference for flat stainless steel washers, in order to standardize market expectations for users, distributors and manufacturers.
For mechanical properties of flat washers made of carbon steel and alloy steel, see ISO 898.