ROLLS: Pearlite, Bainite and Martensite Structures
By SARJIT ROLLS
Keywords: Adamite, SG
Iron, Alloy steel, DPIC Solid, Enhanced carbide ICDP, SG Acicular, hot or cold
rolling
At the very first
instance these words could sound very tedious and overwhelming but the actual
scientific mechanism is very simple.
Pearlite structure is
one which is mainly achieved in static castings as the rate of cooling of the
metal is slow i.e. a temperature below 600 degC is achieved only after 3 – 4
hours or more after pouring of molten material for rolls. The main
characteristic of this structure is that it imparts strength with its equiaxed
matrix to the rolls and is used to manufacture rouging mill rolls as in Alloy
steel, Adamite, SG Iron grade. The hardness that can be achieved is in the
range of 40 – 70 sH.
Bainite Structure can
be achieved by both in static casting, using thicker molds, and in centrifugal
casting as the rate of cooling of metal is relatively faster i.e. a temperature
below 600 degC is achieved within 15 – 20 minutes after pouring of molten
material for rolls. The main characteristic of this structure is that it
imparts polish on the rolled product due its fine matrix. Mainly used for
finishing mill rolls as in Duplex DPIC rolls, Enhanced carbide ICDP rolls,
alloyed barrels and SG acicular rolls. The hardness that can be achieved is in
the range of 65 – 80 sH
Martensite Structures
can only be casted using centrifugal mechanism as the rate of cooling of metal
is very fast i.e. a temperature below 600 degC is achieved within 3-4 minutes
after pouring of molten material for rolls. The structure of the material
formed is very fine in nature but overall it does not have any useful
industrial application as faster the cooling more the risk of chipping of
material.
NOTE: There is no fine line between the above
structures. Due to variation in cooling at any point either 2 or even three of
the above could exist in the same casting. But the major portion could be one
of them
For
any queries please respond to www.sarjitrolls.com
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