ISO/TC 2/WG 17 - Stainless steel fasteners

This document specifies general rules and provides technical information on stainless steels and their properties, which are relevant when using other parts of the ISO 3506 series. It includes specifications for corrosion-resistant stainless steels and nickel alloys, which are suitable for the manufacture of fasteners. It applies to austenitic, martensitic, ferritic and duplex (austenitic-ferritic) stainless steel grades and nickel alloys for fasteners, and is intended to be used together with the relevant parts of the ISO 3506 series. Common designations of stainless steels and nickel alloys used for fasteners are given in Annex A.

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 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.

This document specifies the mechanical and physical properties of bolts, screws and studs, 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 fasteners. The term "fasteners" is used in this document when bolts, screws and studs are considered all together. ISO 3506‑6 provides general rules and additional technical information on suitable stainless steels and their properties. Fasteners 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 Annex A and 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 fasteners mechanical properties and clamped parts, and the corrosive service environment of the bolted joint. NOTE 2 ISO 3506‑5 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 bolts, screws and studs: — 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 M1,6 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, and — of any shape. Stainless steel grades and property classes can be used for sizes outside the diameter limits of this document (i.e. for d d > 39 mm), provided that all applicable chemical, mechanical and physical requirements are met. Certain bolts, screws and studs might not fulfil the tensile or torsional requirements of this document because of the geometry of their head or unthreaded shank, thus resulting in reduced loadability (e.g. when shear area in the head is less than the stress area in the thread; see 8.2.2). This document does not apply to set screws and similar threaded fasteners not under tensile stress (see ISO 3506‑3). It does not specify requirements for functional properties such as: — torque/clamp force properties, — shear strength, — fatigue resistance, or — weldability.

ISO 3506-4:2009 specifies the mechanical properties of tapping screws made of austenitic, martensitic and ferritic steel grades of corrosion-resistant stainless steels, when tested over an ambient temperature range of 10 °C to 35 °C. Properties vary at higher or lower temperatures. It applies to tapping screws with threads from ST2,2 up to and including ST8, in accordance with ISO 1478. It does not apply to screws with special properties such as weldability.

ISO 3506-3:2009 specifies the mechanical properties of set screws and similar fasteners not under tensile stress made of austenitic stainless steel, when tested over an ambient temperature range of 10 °C to 35 °C. Properties vary at higher or lower temperatures. ISO 3506-3:2009 applies to set screws and similar fasteners: - with nominal thread diameter 1,6 mm ≤ d ≤ 24 mm; - of triangular ISO metric threads with diameters and pitches in accordance with ISO 68-1, ISO 261 and ISO 262; - of any shape. It does not apply to screws with special properties, such as weldability.

ISO 16048 specifies the methods most often used for passivation of corrosion-resistant stainless steel fasteners. Typical anodic dissolution behaviour of an active-passive-transpassive metal is given in an annex.

ISO 3506-2:2009 specifies the mechanical properties of nuts made of austenitic, martensitic and ferritic steel grades of corrosion-resistant stainless steels, when tested over an ambient temperature range of 10 °C to 35 °C. Properties vary at higher or lower temperatures. ISO 3506-2:2009 applies to nuts: - with nominal thread diameter d ≤ 39 mm; - of triangular ISO metric threads with diameters and pitches in accordance with ISO 68-1, ISO 261 and ISO 262; - of any shape; - with width across flats as specified in ISO 272; - with nominal heights m ≥ 0,5 d. It does not apply to nuts requiring properties, such as locking abilities and weldability.

ISO 3506-1:2009 specifies the mechanical properties of bolts, screws and studs made of austenitic, martensitic and ferritic steel grades of corrosion-resistant stainless steels, when tested over an ambient temperature range of 10 °C to 35 °C. Properties vary at higher or lower temperatures. ISO 3506-1:2009 applies to bolts, screws and studs - with nominal thread diameter d ≤ 39 mm, - of triangular ISO metric threads with diameters and pitches in accordance with ISO 68-1, ISO 261 and ISO 262, and - of any shape. It does not apply to screws with special properties, such as weldability.