TOPIC 3 : STEEL WORK

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TOPIC 3 STEEL WORK
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TOPIC 3 STEEL WORK

• 3.1 Steel Iron

• a. Pig Iron b. Cast Iron
  c. Wrought Iron
  d. Mild Steel

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FERROUS METAL

• Iron
• Steel
• Stainless steel

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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.

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IRON

• One of the most abundant metallic material in the
  earths 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

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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

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LISTEN CAREFULLY !!!
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Steel Iron Production
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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.

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Primary steelmaking

• method of primary steelmaking in which
  carbon-rich molten pig iron is made into steel.
• To the process segment!!!!

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Process

• Molten iron from a blast furnace is poured into a
  large refractory-lined 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.

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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.

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• 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 1700C.
  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.

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• 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.

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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.

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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

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BLAST FURNACE
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HISTORY!!!

• OKAY.. SANGAT MEMBOSANKAN.. TP KENA TAHUJUGAK!

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WHAT IS BLAST FURNACE???

• A blast furnace is a type of metallurgical
  furnace used for smelting to produce industrial
  metals, generally iron.

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• 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.

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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.

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• 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

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WE HAVE A MODERN MACHINE NOW!!!

• SILA BERASA SANGAT GEMBIRA SEKARANG!!!

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Modern furnaces

• The blast furnace remains an important part of
  modern iron production. Modern furnaces are
  highly efficient, including Cowper stoves to
  pre-heat 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.

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Blast furnace diagram

1. Hot blast from Cowper stoves
2. Melting zone (bosh)
3. 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

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Secondary steelmaking

• An electric arc furnace (EAF) is a furnace that
  heats charged material by means of an electric
  arc.

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• The furnace is primarily split into three
  sections ..
• To be continued

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Sambung semula
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• The furnace is primarily split into three
  sections ..
• To be continued

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• 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
  water-cooled, 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.