This part of ISO3506 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 ISO1478.
It does not apply to screws with special properties, such as weldability.
NOTE The designation system of this part of ISO3506 can be used for sizes outside the limits given in this clause (e.g. d>ST8), provided that all applicable mechanical and physical requirements of the hardness classes are met.
This part of ISO3506 does not define corrosion or oxidation resistance in particular environments. However, some information on materials for particular environments is given in AnnexC. Regarding definitions of corrosion and corrosion resistance, see ISO8044.
The aim of this part of ISO3506 is the classification of corrosion-resistant stainless steel tapping screws into hardness classes.
Corrosion and oxidation performances and mechanical properties for use at elevated or sub-zero temperatures can be agreed on between the user and the manufacturer in each particular case. AnnexD shows how the risk of intergranular corrosion at elevated temperatures depends on the carbon content.
All austenitic stainless steel fasteners are normally non-magnetic in the annealed condition; after cold working, some magnetic properties can be evident (see AnnexE).