Introduction
Steel is an alloy made by combining iron and other elements, the most
common of these being carbon. When carbon is used, its content
in the steel is between 0.2% and 2.1% by weight, depending on the grade.
Other elements used are manganese, chromium vanadium, tungsten.
Carbon and other elements act as a hardening agent, preventing dislocation in
the iron atom crystal lattice from
sliding past one another. Varying the amount of alloying elements and the form
of their presence in the steel (solute elements, precipitated phase) controls
qualities such as the hardness,ductility and tensile strength of the resulting steel. Steel
with increased carbon content can be made harder and stronger than iron, but
such steel is also less ductile than iron.
When
iron is smelted from its ore by commercial processes, it contains more carbon
than is desirable. To become steel, it must be melted and reprocessed to reduce
the carbon to the correct amount, at which point other elements can be added.
This liquid is then continuously cast into long slabs or cast into ingots. Approximately 96% of steel is
continuously cast, while only 4% is produced as cast steel ingots. The
ingots are then heated in a soaking pit and hot rolled into
slabs, blooms, or billets. Slabs are hot or cold rolled into sheet metal or
plates. Billets are hot or cold rolled into bars, rods, and wire. Blooms are
hot or cold rolled into structure steel,
such as I-beam and rails.
In modern foundries these processes often occur
in one assembly line, with ore coming in and finished
steel coming out.
Design
of Bloom
Different
design principles are used for casting strands of different cross sections.
Bloom casters solidify sections of 300 by 400 millimeters.
Steel
Bloom dependable Semi-finished product for steel plant. The Steel Bloom is
widely demanded in different size and dimension with different quality.
Sizes:
Different Sizes of Steel bloom like 200x200 Mm, 260x260 Mm, 260x340 Mm, 265x335 Mm.
Length:
Specifiable Up to 12 M
Different Sizes of Steel bloom like 200x200 Mm, 260x260 Mm, 260x340 Mm, 265x335 Mm.
Length:
Specifiable Up to 12 M
Chemical
Composition of Bloom
Grade
|
C
|
Mn
|
Si
|
S(Max)
|
P(Max)
|
Al(Max)
|
Mo(Max)
|
Cr
|
V(Max)
|
880
|
0.60-0.80
|
0.80-1.30
|
0.10-0.50
|
0.030*
|
0.030*
|
0.015
|
-
|
-
|
-
|
1080 Cr
|
0.60-0.80
|
0.80-1.20
|
0.50-1.10
|
0.025
|
0.025
|
0.004
|
0.20
|
0.80-1.20
|
0.20
|
VANADIUM (VN)
|
0.60-0.80
|
0.80-1.30
|
0.10-0.50
|
0.025*
|
0.030*
|
0.015
|
-
|
-
|
0.20
|
Copper-Molybdenum (CM) 0.35
|
0.60-0.80
|
0.80-1.30
|
0.10-0.50
|
0.030*
|
0.030*
|
0.015
|
0.2-0.3
|
-
|
0.25
|
Mechanical
properties of Bloom Steel
UTS(MPa)(min)
|
Yield Strength***(MPa)(min)
|
Elongation% om Gauge Length-5.65 So(min)
|
880
|
460
|
10.0
|
1080
|
560
|
9.0
|
880
|
540
|
10.0
|
880
|
460
|
10.0
|
Uses
of Steel Bloom
Wire
rod
Railways Rail
TMT
rod etc
Process
of Steel Making
1.
Molten pig iron
(sometimes referred to as "hot metal") from a blast furnace is poured
into a large refractory-lined container called a ladle;
2.
The metal in the
ladle is sent directly for basic oxygen steel making or to a pretreatment stage.
Pretreatment of the blast furnace metal is used to reduce the refining load
of sulfure, Silicon and phosphorus. In desulfurising pretreatment,
a lance is lowered into the molten iron in the ladle. The decision to pretreat depends
on the quality of the blast furnace metal and the required final quality of the
BOS steel
3.
Filling
the furnace with
the ingredients is called charging. The BOS process is autogenous: the
required thermal energy is produced during the process.
4.
The vessel is
then set upright and a water-cooled lance is lowered down into it. The lance
blows 99% pure oxygen onto the steel and iron, igniting the carbon dissolved in
the steel and burning it to form carbon monoxide and carbon dioxide, causing the
temperature to rise to about 1700°C.
5.
Fluxes (burnt lime or dolomite) are fed into
the vessel to form slag, which absorbs impurities
of the steelmaking process. During blowing the metal in the vessel forms an
emulsion with the slag, facilitating the refining process.
6.
The BOS vessel
is tilted again and the steel is poured into a giant ladle. This process is
called tapping the steel. The steel is further refined in the ladle
furnace, by adding alloying materials to give the steel special properties.
Flow diagram of
Steel Making
Process
of Steel Bloom
Molten steel is cast into large blocks called
"blooms". During the casting process various methods are used, such
as addition of aluminum, so that impurities in
the steel float to the surface where they can be cut off the finished bloom.
Because of the energy cost and structural
stress associated with heating and cooling a blast furnace, typically these
primary steelmaking vessels will operate on a continuous production campaign of
several years duration. Even during periods of low steel demand, it may not be
feasible to let the blast furnace grow cold, though some adjustment of the
production rate is possible.
Integrated mills are large facilities
that are typically only economical to build in 2,000,000 ton per year annual
capacity and up. Final products made by an integrated plant are usually large
structural sections, heavy plate, strip, wire rod, railways rail, and
occasionally long product such as bars and pipe.
Steel Bloom produce by Continuous Casting
In
this process, molten steel flows from a ladle, through a tundish into the mold.
The tundish holds enough metal to provide a continuous flow to the mold, even
during an exchange of ladles, which are supplied periodically from the
steelmaking process. The tundish can also serve as a refining vessel to float
out detrimental inclusions into the slag layer.
Once in the mold, the molten steel freezes
against the water-cooled walls of a bottomless copper mold to form a solid
shell. The mold is oscillated vertically in order to discourage sticking of the
shell to the mold walls. Drive rolls lower in the machine continuously withdraw
the shell from the mold at a rate or “casting speed” that matches the flow of
incoming metal, so the process ideally runs in steady state. The liquid flow
rate is controlled by restricting the opening in the nozzle according to the
signal fed back from a level sensor in the mold.
Continuous Casting of Bloom
Test
of Steel Bloom
Non-destructive
testing (NDT) is a wide group of analysis techniques used in science and
industry to evaluate the properties of a material, component or system without
causing damage. The terms Nondestructive examination (NDE) , Nondestructive
inspection (NDI), and Nondestructive evaluation (NDE) are also
commonly used to describe this technology. Because NDT does not
permanently alter the article being inspected, it is a highly-valuable
technique that can save both money and time in product evaluation, troubleshooting,
and research. Common NDT methods include Ultrasonic, magnetic particle, liquid penetrate, radiographic, remote visual inspection (RVI), Eddy current testing.
In ultrasonic testing (UT), very short ultrasonic pulse-waves
with center frequencies ranging from 0.1-15 MHz and occasionally up to
50 MHz are launched into materials to detect internal flaws or to
characterize materials. In ultrasonic testing, an ultrasound transducer connected to a diagnostic
machine is passed over the object being inspected. The transducer is typically
separated from the test object by a couplant (such as oil) or by water, as in
immersion testing.
Advantages
1. High penetrating power, which allows the detection
of flaws deep in the part.
2. High sensitivity, permitting the detection of
extremely small flaws.
3. Only one surface need be accessible.
4. Greater accuracy than other nondestructive methods
in determining the depth of internal flaws and the thickness of parts with
parallel surfaces.
5. Some capability of estimating the size, orientation,
shape and nature of defects.
6. Nonhazardous to operations or to nearby personnel
and has no effect on equipment and materials in the vicinity.
7. Capable of portable or highly automated operation
