Martensitic Stainless Steels
Martensitic stainless steels are the first branch of the plain chromium stainless steels.
The common grades are 410, 416, 420/420C, 431 and 440C these are all alloys containing iron, chromium (12% to 18%) and carbon (up to 1%). These steels are able to be hardened by way of a quench and temper heat treatment process and capable of high levels of strength and hardness.
The basic characteristics of martensitic stainless steels are that they have low resistance too high and low temperature, moderate corrosion resistance. Are magnetic with low ductility along with a medium work hardening rate. Can be welded providing correct procedures are followed but commonly used in machining applications.
Typical applications for the use of Martensitic stainless steels include Knife blades, domestic cutlery, surgical instruments, special fasteners, turbines, impellers, valve bodies and chemical engineering equipment. Most commonly supplied in bar form with options of sheet, plate and coil predominantly in Grade 420/420C for blade manufacture.
Grade and Typical application:
410 – General purpose used for nuts, bolts, bushings, pump and valve parts in mildly corrosive environments.
416 – Free machining variation of 410 used in the same applications.
420 – General use, pump shafts and valve assemblies.
420C – Created to obtain high hardness after heat treatment for tooling and Blade manufacture.
431 – Hardenable steel with corrosion resistance close to 304, ideal for pump shafts, beater bars and marine hardware applications.
440C – Highest hardness and abrasion resistance of all the stainless steels used in valve seats, surgical equipment and bearings.
These steels with a minimum of 10.5% Cr have exceptional strength due to heat treatment at various temperatures that induces precipitation hardening (also known as aging). This process allows a sub microscopic precipitation of phase rich in elements coherent with the matrix (for example Cu ) that greatly increases the mechanical properties of the steel.