23-Sept-2020
To transfer finished melt steel
from a ladle to mould in a continuous casting process, an intermediate vessel
is used which is called tundish. The role of tundish is to deliver the molten
metal to the moulds evenly and at a designed throughput rate and temperature
without causing contamination by inclusions. Inclusion float out, slag
vortexing, till end slab volume and residual metal in tundish are a strong
function of tundish hydrodynamics. Tundish design as well as flow control
devices / modifiers are known to have strong influence on tundish
hydrodynamics.
One of the major functions of
steel making tundish is to enhance inclusion floatability and thereby, produce
clean steel. For the removal of inclusion through floatation, wall adhesion and
agglomeration the flow patterns inside the tundish play an important role,
which in turn
Melt flow in any given tundish can be favourably altered by incorporating
suitable tundish flow modifiers (TFM) and/or changing the design of the
tundish. The flow modifiers play an important role in promoting the floatation
of nonmetallic inclusions in steel.
Now-a-days refractory makers
are offering customized refractory solution. The new age tundish refractories
facilitate temperature homogenization, removal of macro-inclusion, prevention
of nozzle clogging etc. inside tundish. To streamline the flow and compress
turbulence inside tundish various Flow Control Devices (FCD) are being used in
place of traditional FCDs or tundish furniture like Dams, Weirs, Charge Pads,
and Side Wall Pads etc.
The next generation FCDs are popularly known as Tundish
Flow Modifier (TFM), Tundish Flow Optimizer (TFO) etc. are precast
refractory shapes made of Ultra Low Cement Castables (ULCC) having 85 - 90%
alumina. The interior of tundish flow modifiers or flow optimizers as you say
it, are designed in such a way that incoming steel gets a churning effect which
results into inclusion flotation and subsequent absorption at the tundish
powder level. Tundish argon diffusers are also being used to reduce inclusion
in steel.
Eventually, it is tundish design from the viewpoint of metal flow and
appropriate selection of refractory materials with their right positioning
inside tundish that holds the key to the success of subsequent operations in
steel making.
