Standard high tensile strength fasteners
The standard grade high strength fasteners have, from a materials perspective, not changed very much during the last decades. They are regulated via standard ISO898-1 and ISO898-2. The majority of all European automotive manufacturers use these standards as their material and property specification (alternatively slightly modified versions of the same data in the format of company specific standards).
Grade 8.8-12.9 all have in common that they consist of martensitic steel which is quenched and temper heat treated after the cold forming of the fastener geometry itself. These martensitic steels achieve hardness and strength from the martensitic microstructure; carbon atoms in solid solution, the fine grain structure created by the martensite transformation and a high dislocation density. High toughness and ductility is achieved via the tempering operation.
The regulations on steel composition given in the ISO 898 has led to the usage of boron alloyed carbon steel for grade 8.8 and 10.9 whereas chromium alloyed carbon steel is applied for grade 12.9. The majority of new developments within the field of high tensile strength fasteners are done on fastener geometry, coating systems and application engineering as the material selection already is optimized.
Nedschroef continuously is improving the efficiency and quality of all processes, which are applied when producing high strength products. This makes it possible for us to offer best price and best quality.