Stainless steel is the name of high alloy steel used mainly for its anti-corrosion properties. The main characteristic of the stainless steel family is that they all contain a minimum of 10.5 percent of chromium. This enables the steel to withstand corrosive atmospheres or erosive chemical environments. There are over 60 different grades of stainless steel that is divided into 5 different categories. Stainless steel is more expensive than carbon and alloy steel and only accounts for a small number of steel used in the global market, but it is non the less a very valuable international market.

Stainless steel categories:

Stainless steel is divided into 5 main categories. These are Austenitic, martensitic, ferritic, duplex and precipitation hardening.

200 Series Austenitic – Alloys: 201, 202, 203, 204 & 205 is a chromium-nickel-manganese alloy with high strength in the annealed. This series is non-magnetic, not heat treatable and has excellent formability for sever forming applications. It is used in structural applications and for the manufacture of washing machine tubs.

300 Series Austenitic – Alloys: 301, 302, 303, 304, 305, 308, 309, 310, 314, 316, 317, 321, 330, 347, 384 is chromium-nickel alloy and its strength is developed by cold working. The series is non-magnetic, not heat treatable and has good formability. By adding molybdenum, the corrosion resistance is increased. It is used in food equipment, chemical equipment and architectural applications.

400 Series Ferritic – Alloys: 405, 409, 429, 430, 434, 436, 442, 446 is straight chromium alloy, magnetic but it is not heat treatable. This series is mainly used for automotive trim and cooking utensils.

400 Series Martensitic – Alloys: 403, 410, 414, 416, 420, 422, 431, 440 is straight chromium alloy, magnetic and can be hardened by heat treatment. It is used for fasteners, pump shafts and turbine blades.

Precipitation Hardening – Alloys: 13-8, 15-5, 15-7, 17-4, 17-7 is chromium-nickel, martensitic or austenitic. Develop strength by precipitation hardening reaction due to heat treatment. It is mainly used for valves, gears and petro-chemical equipment.

Duplex – Alloys: 329, 2205, 2304, 2507, 3RE60 is chromium-nickel-molybdenum. This series is more resistant to stress corrosion cracking than austenitic and it is also tougher than fully ferritic alloys. It is mainly used in pipelines or pressure shafting.

 Application:

Stainless steel is a very versatile and useful material used in a wide variety of applications. It is used in the following fields:

Cutlery and kitchenware
Home appliance
Chemical processing and oil & gas industries
Power generation
Food production
Architecture, building and construction
Medical applications
Automotive parts