VDA 235-205 (08/2020)

In addition to fasteners of property classes 8.8 to 12.9 in accordande with DIN EN ISO 898-1 or recommendation VDA 235-204 with martensitic microstructure, in this recommendation requirements for ultra-high strength fasteners with bainitic microstructure of property classes 12.8U to 16.8U are specified.
Providing comparable or even improved functional properties, the development of such fasteners is a contribution to the increasing requirements for weight reduction of components and systems in cars and thus also of the total weight of vehicles as well as especially to an increased efficiency of engines.
The main characteristic of ultra-high strength fasteners in accordance with this recommendation is the lower bainitic instead of the martensitic, heat treatment to achieve ultra-high tensile strength values in combination with excellent ductility and fatigue properties.