Stainless Steel Compositions And Types
                     Stainless Steel Compositions And Types
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Stainless steel is one of the most widely used alloys of iron that is 
known for its extensive range of benefits such as enhanced robustness 
and resistance to corrosion and rust.
The alloy consists of a combination of iron and chromium. It is the 
presence of chromium that prevents the iron components to remain 
protected from rust and corrosion. The resistance to corrosion 
increases with enhanced amounts of chromium. Stainless steel also 
includes varying amounts of Silicon, Carbon, and Manganese. 
Certain other elements like Molybdenum and Nickel can also be 
added for imparting various useful characteristics and properties like 
enhanced corrosion resistance and increased formability.
Here is a look at the various types of stainless steel compositions and 
types that are mostly used across the world.
Ferritic Stainless Steel
Ferritic stainless steel is made by combining iron with chromium 
anywhere between 11.2% and 19% without any or very small traces 
of nickel. Since nickel is definitely a very expensive alloying element 
that is also known to go through a lot of price volatility, keeping the 
amount of nickel low makes it possible to maintain a stable price 
compared to the steel components having high amounts of nickel. 
Sometimes molybdenum is combined with certain grades of ferritic 
stainless steel so that their corrosion resistance can be improved. 
The welding feature of this type of stainless steel can be enhanced by 
adding titanium and/or niobium. Ferritic stainless steel is known for 
its superior toughness, durability, corrosion resistance and strong 
magnetic properties. The magnetism is caused by the ferritic 
microstructure of this type of stainless steel. They are typically 
resistant to very high temperatures of around 800°C to 1150°C. 
Compared to the standard versions of ferritic grades, they are 
commonly alloyed with a greater amount of carbon for enhancing 
their creep strength. Additionally more amounts of aluminum and 
silicon can be added for improving oxidation resistance.
Austenitic Stainless Steel
The austenitic stainless steel grades are notable for their enhanced 
corrosion resistance, better weldability and heightened formability. 
They are known to deliver high impact strength even at low 
temperatures and this feature makes them useful in various cryogenic 
applications. These stainless steel components are non-magnetic 
when in solution-annealed condition. Their strength can be increased 
by cold working. Sometimes the presence of small amounts of 
martensite gives rise to magnetic properties. They also have good 
creep resistance. They are mainly divided into five different 
subgroups, namely Cr-Mn grades, Cr-Ni grades, Cr-Ni-Mo grades, 
High-performance grades, and high-temperature grades. 
Duplex Stainless Steel
Duplex stainless steel is known for its ferritic-austenitic 
microstructure which effectively combines numerous benefits of 
austenitic and ferritic stainless steel. This type of steel offers 
enhanced resistance and strength to withstand stress corrosion 
cracking. This form of steel has a rather high chromium content, i.e. 
almost 20.1% to 25.4% along with a low nickel content ranging 
between 1.4% to 7%. This means that like ferritic stainless steel, the 
duplex variant also has a stable price range. They are valued greatly 
for their high good corrosion resistance, great weldability, superior 
toughness, magnetic property and lightweight structure. 
Martensitic Stainless Steel
The martensitic grades of stainless steel are by far the smallest 
category of stainless steel. They have got improved robustness and 
strength due to their higher carbon content. Sometimes nitrogen is 
added for further improving their strength. They have poor 
weldability which can be improved by adding nickel and lowering 
the amounts of carbon. Although they have high wear resistance and 
high strength, they offer very limited corrosion resistance.
Precipitation Hardening Stainless Steel
Precipitation hardening stainless steel is a type of stainless steel that 
is hardened with a special mechanism that makes use precipitates 
formed within the microstructure. This stainless steel also has 
magnetic properties.
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