Stainless Steel is an ideal material for many applications because of its unique properties. The primary benefit of Stainless Steel is that it does not corrode or rust as easily as ordinary steel. Because of this unique property, it is widely used across many industries, including architecture, automotive and others.

What is Stainless Steel?

Stainless steel is an iron alloy that has a minimum Chromium content of 10.5 percent. The Chromium content produces a thin chromium oxide film on the steel’s surface called a passivation layer. This layer prevents corrosion from occurring on the steel surface; the greater the amount of Chromium in the steel, the greater the corrosion resistance. Stainless steel also contains varying amounts of other elements such as Carbon, Silicon, and Manganese. Other elements can be added to increase corrosion resistance (Nickel) and formability (Molybdenum). Formability is the ability to change the form/shape of a metal product without causing permanent damage to it.

The main alloying element in Stainless steel is chromium (typically between 10-20%). Stainless Steel is valued due to its high corrosion resistance. Stainless steel is about 200 times more resistant to corrosion than mild steel.

Stainless steel can be divided into five groups:

#1 Austenitic:

Austenitic steels form the largest portion of the global stainless steel market and few of its versatile usages would be food processing equipment, kitchen utensils, and medical equipment. Austenitic stainless steels are the most weld-able of the stainless grades and can be divided rather loosely into three groups: common chromium-nickel (300 series), manganese-chromium-nickel-nitrogen (200 series) and specialty alloys. These metals are non-magnetic and not heat-treatable.

#2 Ferritic:

Ferritic steels contain trace amounts of nickel, 12-17% chromium, less than 0.1% carbon, along with other alloying elements, such as molybdenum, aluminum or titanium. They can have good ductility and formability, but high-temperature strengths are relatively poor when compared to austenitic grades. Some ferritic stainless grades (such as types 409 and 405) cost less than other stainless steels. These metals are magnetic but are not heat treatable, they can be strengthened by cold working.

#3 Martensitic:

Martensitic steels contain 11-17% chromium, less than 0.4% nickel, and up to 1.2% carbon. The carbon content of this harden-able steel affects forming and welding. To obtain useful properties and prevent cracking, preheating and post-weld heat treatment are required. Martensitic stainless steels, such as types 403, 410, 410NiMo and 420 are magnetic and heat-treatable. These Stainless steel are used in knives, cutting tools, as well as dental and surgical equipment.

Duplex: Primarily used in chemical plants and piping applications. Duplex stainless steels typically contain approximately 22-25% chromium and 5% nickel with molybdenum and nitrogen. Duplexes have higher yield strength and greater stress corrosion cracking resistance to chloride than austenitic stainless steels.

#4 Precipitation Hardening:

This is a chromium-nickel stainless that also contains alloying additions such as aluminum, copper or titanium. These alloys allow the stainless to be hardened by a solution and aging heat treatment. They can be either austenitic or martensitic in the aged condition. Choosing a particular type of stainless steel can depend on the application and your requirements.