Stainless steels are divided into five groups: martensitic stainless steels, ferritic stainless steels, austenitic stainless steels, duplex (ferritic-austenitic) stainless steels, and precipitation-hardening stainless steels.These groups divide stainless steel by differing attributes. below are a basic over view of each group. These characteristics offer unique distinctions for different industries seeking stainless steel use in many applications.
MARTENSITIC GRADES This grade contains 12%-18% Cr and zero.08%-1.00% carbon. The high carbon content permits the chrome steel to reply well to heat treatment to relinquish numerous mechanical strengths like hardness. but the carbon is damaging once attachment and care should be taken. Grades 409, 410, 420 and 431 square measure typical martensitic grades.
FERRITIC GRADES These square measure nickel free. they need varied Cr content of 12%-22% however a lower carbon content than the martensitic grades. The exaggerated Cr will increase corrosion resistance at elevated temperatures, but the dearth of mechanical properties thanks to the very fact that it can not be heat-treated limits its application.
The basic idea of duplex is to produce a chemical composition that leads to an approximately equal mixture of ferrite and austenite. This is mainly due to advances in steel-making techniques particularly due to control of nitrogen content. The range of duplex steels allows them to be matched for corrosion resistance with the austenitic and ferritic steel grades. There is no single measure of corrosion resistance.
The precipitation hardening (PH) stainless steels are a family of corrosion resistant alloys some of which can be heat treated to provide tensile strengths. They are used in the oil and gas, nuclear and aerospace industries where a combination of high strength, corrosion resistance and a generally low but acceptable degree of toughness is required.
The most common and familiar types of stainless steel. They are most easily recognized as nonmagnetic. Extremely formable and weldable, and they can be successfully used from cryogenic temperatures to the red-hot temperatures of furnaces and jet engines. They contain between about 16 and 25% chromium, and they can also contain nitrogen in solution, both of which contribute to their high corrosion resistance.