Materials & Components by YEhmBCM

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									Materials & Components

      Metals & Alloys
          Basic Classification

                          METALS




   FERROUS:
                          ALLOYS:          NON-FERROUS:
Contain iron. Almost
                       Mixture of two or   Pure metals, don’t
all are magnetic and
                         more metals          contain iron
  corrode quickly if
      untreated.
      Ferrous: Production of Steel
•   Ore is mined
     – Magnetic ores (upto 65% iron – Sweden, USA, USSR)
     – Haematite ores (40-60% iron – Spain & USA, Some
       GB deposites)
•   Initial treatment
     – Washed
     – Graded (roasted to remove some of carbon, water &
       sulphur)
     – Crushed (to usable lumps – 100mm cubes)
•   Refined
     – Iron ore, coke & limestone placed in blast furnace
     – Heated air blasted into furnace causes coke to burn
     – Limestone decomposes and separates impurities
       (reduction)
     – Impure ‘slag’ forms at top and tapped off – ballast and
       road building
     – Heavier pig-iron forms at bottom
   Basic Oxygen Furnace for the
        Production of Steel
• Because pig iron is hard but quite brittle,
  it is not very useful in this state.
• To produce steel, most of the impurities
  are removed by blowing hot oxygen
  through the molten pig iron for a short
  time in a basic oxygen furnace. This
  process oxidizes the impurities which
  escape as gases or form slag.
• A typical basic oxygen furnace is
  charged with about 200 tons of molten
  pig iron,100 tons of scrap iron, and 20
  tons of limestone.
• The product of the basic oxygen furnace
  is carbon steel, which is strong and
  malleable and therefore much more
  useful than pig iron.
                       Iron & Steel
Steel is a combination of iron and carbon    Hard &
                                             Brittle
• Cast Iron (3% – 4%)


• High Carbon Steel (0.7% - 1.4%)


• Medium Carbon steel (0.3% - 0.7%)


• Mild Steel (0.15% - 0.3%)


• Low Carbon Steel (less than 0.15%)
                                             Soft &
                                            Malleable
         Non-Ferrous Metals
• Aluminium


• Copper


• Zinc
            Production of Aluminium
Mined as Bauxite
(USA, France, Guayana, Australia, Africa)

1.     Treated with caustic soda
       and heated under pressure
2.     Filtered and washed
3.     Heated to 1100 C in rotary
       kiln to form Alumina
       (Aluminium Oxide)
4.     Reduced by electrolysis to
       separate oxygen and
       aluminium
5.     Heavier aluminium sinks and
       is siphoned off and cast into
       ingots
            Production of Copper
• Relatively scarce (USA, Chile, Canada,
  Zambia USSR – historically: Wales)
• Ore contains less than 4% copper
• Ore crushed
• Separated from rock by floatation
  (grains of copper float, rock sinks)
• Smelted in a reverbatory furnace, lime
  added as flux. Impurities tapped off.
• Either:
   – Remelted, impurities oxidised and
     removed as slag, followed by ‘poling’ –
     oxygen removed by combustion
   – Electrolytic refining in sulphuric acid,
     copper deposited on cathode
         Production of Zinc
• Ore Zinc Blonde
• Crushed and concentrated by floatation
• Smelted in blast furnace
• Zinc removed as vapour and condensed in
  contact with molten lead
• Electrolysis produces very pure form.
            Common Alloys
• Stainless steel
 (Medium carbon steel + 12% chromium + 8% nickel)


• Aluminium Alloys
 Duralumin (Aluminium + 4% copper + 1% magnesium)


• Brass
 (65% copper, 35% zinc)
                  Micro-structure




 Close Packed         Face Centred            Body Centred
Hexagonal (CPH)        Cube (FCC)              Cube (BCC)
Weak, poor strength    Very ductile,           Hard, tough
  to weight ratio     good electrical
                        conductor


  Iron (below 910C    Iron (910-1400C),    Chromium, tungsten
  and above 1400C),   aluminium, copper,
  zinc, magnesium     gold, silver, lead
              Crystallisation
• Pure metals solidify at a
  fixed temp
• Crystals form in either
  cube or fixed structure
• Further cooling causes
  crystals to grow
  (dendrites) until one
  touches its neighbour
• Where dendrites meet,
  boundaries are formed to
  produce grains
          Steels worksheet
• Using the table 3.1.1

								
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