There are four types of stainless steel: austenitics, ferritics, duplex and martensitics – all with varying characteristics in terms of strength, corrosion resistance, hardness and weldability.
Austenitic
The austenitic grades offer good to excellent corrosion resistance, as well as good formability and weldability. Their high impact strength at low temperatures is often exploited in cryogenic applications. Austenitic grades are non-magnetic.
Ferritic
The standard ferritic grades are alloyed with chromium (11.2–19%), but with no or negligible addition of nickel. Ranking among the most expensive alloying elements, nickel is subject to high price volatility. The low nickel content of ferritic grades makes them more price stable than grades with high nickel content.
Duplex
Duplex grades have a ferritic-austenitic microstructure that combines many of the beneficial properties of ferritic and austenitic stainless steels. The duplex microstructure also contributes to high strength and high resistance to stress corrosion cracking.
Martensitic
The martensitic grades are the smallest group of stainless steels. For improved strength and hardenability, they have higher carbon content than other grades, and nitrogen is sometimes added to further improve strength.
|
FOUR TYPES OF STAINLESS |
|||
|---|---|---|---|
|
DUPLEX |
AUSTENITIC |
FERRITIC |
MARTENSITIC |
|
High strength and toughness |
Good to excellent corrosion resistance |
Low carbon and nickel content |
High strength |
|
Very good corrosion resistance |
Good weldability and formability |
Good corrosion resistance |
High wear resistance |
|
Good weldability |
Good creep resistance |
Good weldability and toughness |
Limited corrosion resistance |
|
Lightweight |
Non-magnetic |
Magnetic |
Magnetic |
|
Magnetic |
|
|
|