Thanks to the expertise of its team of engineers and researchers, Acciai Speciali Terni has developed martensitic grades for a wide and diverse range of applications requiring enhanced hardness and optimal wear resistance: from cutlery to cutting tools, from industrial machinery blades to surgical instruments, from manual equipment to stainless tools, and from valves to disk brakes.

Our martensitic stainless steel grades – 420A (EN 1.4021), 420J2 (EN 1.4028) and 420 (EN 1.4034) – feature a high level of carbon content and are subject to heat treatments, such as tempering and quenching, that allow them to offer excellent hardness and wear resistance.

The three grades have different levels of carbon content:

*average carbon content

With appropriate heat treatments, higher carbon content allows us to achieve increased hardness levels. The ideal hardness depends on the specific application steel is intended for.

Material supplied in annealed condition is workable and will undergo final heat treatment to achieve the mechanical properties and hardness level required by the specific application it is destined to: from cutlery for home and profesionals kitchens to surgical instruments, and from mechanical components (such as camshafts, flanges and valves) to disk brakes, our martensitic range was designed to meet any client’s needs.

Versatility is one of the outstanding features of our range of martensitic steel grades: from highly aesthetic applications such as exclusive cutlery – where beauty must meet top performance in terms of hardness and wear resistance – to applications where functionality is king, such as valves, disk brakes and so on.

All of Acciai Speciali Terni’s martensitic grades also feature good resistance to corrosion and are suitable for contact with food.


ELEMENTS (%) C Cr Ni Mo Others
420A AST
typical values
0,21 13,2
420J2 AST
typical values
0,32 13,2
420 AST
typical values
0,46 13,2



Click here to view our Privacy policy

Copyright ® 2020 by Acciai Speciali Terni | Acciai Speciali Terni S.p.A.
con Unico Socio P.IVA 00715760559