Transcript TOPIC 3 : STEEL WORK

TOPIC 3 : STEEL WORK
TOPIC 3 : STEEL WORK
3.1 Steel Iron
a. Pig Iron
b. Cast Iron
c. Wrought Iron
d. Mild Steel
FERROUS METAL
o Iron
o Steel
o Stainless steel
What is iron???
Pure iron is a metal but is rarely found
in this form on the surface of the earth
because it oxidizes readily in the
presence of oxygen and moisture.
IRON
• One of the most abundant metallic
material in the earth’s crust (about 4-5%)
• Found in the form of ores as oxides,
carbonates, silicates, and sulfides
• The most important iron-bearing minerals
or iron ores are hematite and magnetite
IRON (cont.)
• The most commonly used ore is
Hematite (Fe2O3)
• Contains about 70% of pure iron
• Specific gravity in the range of 4.5
to 5.3
LISTEN CAREFULLY !!!
Steel & Iron
Production
Broken into two categories:
Primary and Secondary
steelmaking.
•Primary steelmaking uses mostly new
iron as the feedstock, usually from a
blast furnace.
•Secondary steelmaking uses scrap
steel as the primary raw material.
Primary steelmaking
• method of primary steelmaking in which
carbon-rich molten pig iron is made into
steel.
• To the process segment!!!!
Process
• Molten iron from a blast furnace is poured into a large refractorylined container called a ladle;
• The metal in the ladle is sent directly for basic oxygen steelmaking
or to a pretreatment stage.
Pretreatment of the blast furnace metal is used to reduce the
refining load of sulfur, silicon, and phosphorus. In desulfurising pre
treatment, a lance is lowered into the molten iron in the ladle and
several hundred kilograms of powdered magnesium are added.
Sulfur impurities are reduced to magnesium sulfide in a violent
exothermic reaction. The sulfide is then raked off. Similar
pretreatment is possible for desiliconisation and dephosphorisation
using mill scale (iron oxide) and lime as reagents. The decision to
pretreat depends on the quality of the blast furnace metal and the
required final quality of the BOS steel.
3. Charging process!!
• Filling the furnace with the ingredients.
• The BOS process is autogenous: the required
thermal energy is produced during the process.
Maintaining the proper charge balance, the ratio
of hotmetal to scrap, is therefore very important.
The BOS vessel is one-fifth filled with steel
scrap. Molten iron from the ladle is added as
required by the charge balance. A typical
chemistry of hotmetal charged into the BOS
vessel is: 4% C, 0.2-0.8% Si, 0.08%-0.18% P,
and 0.01-0.04% S.
• 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. This melts the scrap, lowers the
carbon content of the molten iron and helps remove
unwanted chemical elements. It is this use of oxygen
instead of air that improves upon the Bessemer process,
for the nitrogen (and other gases) in air do not react with
the charge as oxygen does. High purity oxygen is blown
into the furnace or BOS vessel through a vertically
oriented water-cooled lance with velocities faster than
Mach 1.
• 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. Near the
end of the blowing cycle, which takes about 20
minutes, the temperature is measured and
samples are taken. The samples are tested and
a computer analysis of the steel given within six
minutes. A typical chemistry of the blown metal
is 0.3-0.6% C, 0.05-0.1% Mn, 0.01-0.03% Si,
0.01-0.03% S and P.
Tapping process
• 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 required by the customer. Sometimes argon
or nitrogen gas is bubbled into the ladle to make sure the
alloys mix correctly. The steel now contains 0.1-1%
carbon. The more carbon in the steel, the harder it is, but
it is also more brittle and less flexible.
• After the steel is removed from the BOS vessel, the slag,
filled with impurities, is poured off and cooled.
PRODUCTION OF IRON
• Iron is produced in a blast furnace
• The main function of the blast furnace is to
reduce the ore to metal, followed by
separation of the metal from the impurities
• The iron ore in the form of pellets is
charged into the furnace with coke and
limestone
BLAST FURNACE
HISTORY!!!
OKAY.. SANGAT
MEMBOSANKAN.. TP KENA
TAHU…JUGAK!
WHAT IS BLAST FURNACE???
• A blast furnace is a type
of metallurgical furnace
used for smelting to
produce industrial metals,
generally iron.
• fuel and ore are continuously supplied
through the top of the furnace, while air
(sometimes with oxygen enrichment) is
blown into the bottom of the chamber, so
that the chemical reactions take place
throughout the furnace as the material
moves downward. The end products are
usually molten metal and slag phases
tapped from the bottom, and flue gases
exiting from the top of the furnace.
History
• An illustration of furnace
bellows operated by
waterwheels, from the
Nong Shu, by Wang
Zhen, 1313 AD, during
the Yuan Dynasty of
China.
• The left picture illustrates the
fining process to make wrought
iron from pig iron, with the right
illustration displaying men
working a blast furnace, of
smelting iron ore producing pig
iron, from the Tiangong Kaiwu
encyclopedia, 1637.
• The first blast furnace in
Russia opened in 1637 near
Tula and was called the
Gorodishche Works. The blast
furnace spread from here to
the central Russia and then
finally to the Urals
• Representation of blast
furnaces and other iron
making processes from
the 19th century
WE HAVE A MODERN
MACHINE NOW!!!
SILA BERASA SANGAT
GEMBIRA SEKARANG!!!
Modern furnaces
• The blast furnace remains an important part of
modern iron production. Modern furnaces are
highly efficient, including Cowper stoves to preheat the blast air and employ recovery systems
to extract the heat from the hot gases exiting the
furnace. Competition in industry drives higher
production rates. The largest blast furnaces
have a volume around 5580 m3 (190,000 cu ft)
and can produce around 80,000 tonnes
(88,000 short tons) of iron per week.
Blast furnace diagram
1.
2.
3.
Hot blast from Cowper stoves
Melting zone (bosh)
Reduction zone of ferrous oxide
(barrel)
4. Reduction zone of ferric oxide
(stack)
5. Pre-heating zone (throat)
6. Feed of ore, limestone, and coke
7. Exhaust gases
8. Column of ore, coke and
limestone
9. Removal of slag
10. Tapping of molten pig iron
11. Collection of waste gases
Secondary steelmaking
• An electric arc furnace (EAF) is a furnace
that heats charged material by means of an
electric arc.
• The furnace
is primarily
split into
three
sections ..
To be
continued…
Sambung semula…
• The furnace
is primarily
split into
three
sections ..
To be
continued…
• the shell, which consists of the sidewalls and
lower steel 'bowl';
• the hearth, which consists of the refractory that
lines the lower bowl;
• the roof, which may be refractory-lined or watercooled, and can be shaped as a section of a
sphere, or as a frustum (conical section). The
roof also supports the refractory delta in its
centre, through which one or more graphite
electrodes enter.