Martensitic stainless steels

Martensitic stainless steels, the first stainless steels commercially developed (For cutlery) have a relatively high carbon content (0.1 - 1.2%) compared to other grades of tainless steels. They are plain chromium steels containing between 12 and 18% chromium. The stainless steel is of moderate corrosion resistance which can be hardened by heat treatment resulting in high strength and hardness. It has poor weldability and is magnetic. It is commonly used for knife blades, surgical instruments, shafts, spindles and pins.


Ferritic stainless steels

These are plain chromium stainless steels with varying chromium content between 11% and 18%, but with low carbon content. They have a moderate to good corrosion resistance, are not hardenable by heat treatment and always used in the unnealed conditions. They are magnetic. The formability is not as good as the austeinitics. These are commonly used in computer floopy disk hubs (430), automotive trim (430), automotive exhausts (409), material handling equipment (3CR12) and in hot water tanks (444).


Austenitic stainless steels

Most commonly used austenitic stainless steel contain 18% chromium and 8% nickel. They have an excellent corrosion resistance, weldability, formability fabricability, ductility, cleanability and hygiene characteristics. Along with good high and excellent low temperature properties, these are non magnetic (if annealed) and are hardenable by cold work only.

This is the most widely used stainless steel. The common uses are in computer floppy disk shutters (304), computer keyboard key springs (301), kitchen sinks (304D), pharmaceuticals, petrochemical industry, food processing equipment, architectural applications and chemical plants.

The highly popular low nickel jindal stainless (JS) proprietory grades J-1, J-3 and J-4 are used for kitchen products.


Duplex stainless steels

These are stainless steels contining relatively high chromium (between 18 and 28%) and moderate amounts of nickel (between 4.5 and 8%). The nickel content is insufficient to generate a fully austenitic structure and the resulting combination of ferritic and austenitic structures is called duplex. Most duplex steels contain molybdenum in a range of 2.5 - 4%. These have a high resistance to stress corrosion, cracking and chloride ion attacks. They have a higher tensile and yield strength than austenitic of ferritic steels as well as good weldability and formability. They are commonly used in marine applications, desalination plants, heat exchangers and petrochemical plants.