Mr.Teks® is a marking for self-drilling screws, which are made of the special Cr-Mo-Ni stainless steel of martensitic type, partially corresponding with X30CrMo13–2 steel. The given alloying system containing 13 – 14,5% of Cr provides not only strong resistance against corrosion comparable with A2 steels, but also an excellent combination of mechanical characteristics (48 – 51 HRC and Rm = 640 – 670 N/mm2). The screws Mr.Teks® are suitable for joining steel, aluminium and thin stainless sheets.
Contrary to austenitic stainless steels (e.g. A2 or A4) which basic microstructural element is an austenite (paramagnetic γ-phase with a cubical, face-centered elementary grid) the final microstructure of martensitic steels is created by a martensite (a ferromagnetic α-phase with a cubical spatially-centered elementary grid) which is a product of hardening. It is impossible to harden the austenitic steels therefore the characteristics at the level of harden-able steels cannot be reached. This is a general distinction between both types. They are equal only from the aspect of resistance against corrosion.
amin = 3d, bmin = 1.5d, d is a screw diameter and F is a tensile power