Martensitic Stainless Steel is a low cost form of Stainless Steel, available in both strip and wire forms. These generally magnetic alloys are formed in the annealed condition, then heat treated. Martensitic grades typically contain 12-15% Chromium, with Carbon as the key alloying element. Carbon content can range from as low as 0.1% to over 1%. The variation in the Carbon content, in addition to the other possible alloying elements, provides this group with a wide range of desirable mechanical properties. Whilst not as popular as other Stainless Steel grades, Martensitics offer high strength, good toughness, good creep resistance, and good heat resistance. These grades also possess a moderate to good corrosion resistance, depending on the their Chromium content. Moreover, the higher Chromium content in some Martensitic grades, such as 431, offer a similar level of corrosion resistance to the Austenitic grade 304.  These alloys also offer improved conductivity compared to Austenitic grades.

Martensitic grades equally share similarities with some Carbon Steels. To improve toughness and ductility, they undergo a hardening process of quenching and tempering. Ultimately, it is the Carbon content of the alloy increases the strength properties. However, increasing Carbon to increase strength, consequently comes at the expense of toughness and ductility.

As a result of its low cost and moderate corrosion resistance, this group is ideal for many applications. In fact it was the first to be commercially developed as cutlery steel. However, it is its high strength and toughness properties that result in Martensitic grades being found across multiple industry sectors. Uses include surgical instruments within hospitals, valves, pumps and other components for the Oil and Gas industry, through to turbines and gears in Aerospace manufacturing. Furthermore, these grades are highly useful for manufacturing complex spring shapes, requiring a soft steel for forming.