ISO 3506-2:2020

Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 2: Nuts with specified grades and property classes

Scope

This document specifies the mechanical and physical properties of nuts, with coarse pitch thread and fine pitch thread, made of corrosion-resistant stainless steels, when tested at the ambient temperature range of 10 °C to 35 °C. It specifies property classes in relation to austenitic, martensitic, ferritic and duplex (austenitic-ferritic) steel grades for nuts.
ISO 3506‑6 provides general rules and additional technical information on suitable stainless steels and their properties.
Nuts conforming to the requirements of this document are evaluated at the ambient temperature specified in paragraph 1. It is possible that they do not retain the specified mechanical and physical properties at elevated and/or lower temperatures.
NOTE 1 Fasteners conforming to the requirements of this document are used without restriction in applications ranging from ?20 °C to +150 °C; however, fasteners conforming to this document are also used for applications outside this range down to ?196 °C and up to +300 °C. For more details, see ISO 3506-6.
Outside the temperature range of ?20 °C to +150 °C, it is the responsibility of the user to determine the appropriate choice for a given application, in consultation with an experienced fastener metallurgist and by taking into account e.g. stainless steel composition, duration of exposure at elevated or low temperature, the effect of the temperature on the fastener mechanical properties and clamped parts, and the corrosive service environment of the bolted joint.
NOTE 2 ISO 3506‑5[1] is developed in order to assist in the selection of appropriate stainless steel grades and property classes intended for use at temperatures up to +800 °C.
This document applies to nuts:
— with ISO metric thread in accordance with ISO 68‑1,
— with diameter/pitch combinations in accordance with ISO 261 and ISO 262,
— with coarse pitch thread M5 to M39, and fine pitch thread M8×1 to M39×3,
— with thread tolerances in accordance with ISO 965‑1 and ISO 965‑2,
— with specified property classes, including proof load,
— with different nut styles: thin nuts, regular nuts and high nuts,
— with a minimum nut height m ≥ 0,45D,
— with a minimum outside diameter or width across flats s ≥ 1,45D (see Annex A),
— of any shape, and
— able to mate with bolts, screws and studs with property classes in accordance with ISO 3506‑1.
Stainless steel grades and property classes can be used for sizes outside the diameter limits of this document (i.e. for D < 5 mm or D > 39 mm), provided that all applicable chemical, mechanical and physical requirements are met.
This document does not specify requirements for functional properties such as:
— torque/clamp force properties,
— prevailing torque properties, or
— weldability.

[1] Under preparation.