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Stainless Steel and Round Bar
Grades
Martensitic
stainless steels
Martensitic stainless steels, the first
stainless steels commercially developed (For cutlery) have a
relatively high carbon content (0.1 - 1.2%) compared to
other grades of tainless steels. They are plain chromium
steels containing between 12 and 18% chromium. The stainless
steel is of moderate corrosion resistance which can be
hardened by heat treatment resulting in high strength and
hardness. It has poor weldability and is magnetic. It is
commonly used for knife blades, surgical instruments,
shafts, spindles and pins.
Ferritic
stainless steels
These are plain chromium stainless steels
with varying chromium content between 11% and 18%, but with
low carbon content. They have a moderate to good corrosion
resistance, are not hardenable by heat treatment and always
used in the unnealed conditions. They are magnetic. The
formability is not as good as the austeinitics. These are
commonly used in computer floopy disk hubs (430), automotive
trim (430), automotive exhausts (409), material handling
equipment (3CR12) and in hot water tanks (444).
Austenitic
stainless steels
Most commonly used austenitic stainless steel
contain 18% chromium and 8% nickel. They have an excellent
corrosion resistance, weldability, formability fabricability,
ductility, cleanability and hygiene characteristics. Along
with good high and excellent low temperature properties,
these are non magnetic (if annealed) and are hardenable by
cold work only.
This is the most widely used stainless steel. The common
uses are in computer floppy disk shutters (304), computer
keyboard key springs (301), kitchen sinks (304D),
pharmaceuticals, petrochemical industry, food processing
equipment, architectural applications and chemical plants.
The highly popular low nickel jindal stainless (JS)
proprietory grades J-1, J-3 and J-4 are used for kitchen
products.
Duplex
stainless steels
These are stainless steels contining
relatively high chromium (between 18 and 28%) and moderate
amounts of nickel (between 4.5 and 8%). The nickel content
is insufficient to generate a fully austenitic structure and
the resulting combination of ferritic and austenitic
structures is called duplex. Most duplex steels contain
molybdenum in a range of 2.5 - 4%. These have a high
resistance to stress corrosion, cracking and chloride ion
attacks. They have a higher tensile and yield strength than
austenitic of ferritic steels as well as good weldability
and formability. They are commonly used in marine
applications, desalination plants, heat exchangers and
petrochemical plants.
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