MODULE  12
                       MATERIAL AND MATERIAL PROCESS 
              LO : Explain and understand the difference between ferrous and non-
              ferrous metals, iron and alloy and discuss the general behaviour of 
              specific materials during specific workshop process.
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                                                  METALS 
            •   The property that separates the metals is whether they contain iron or not.
            •   We have two groups, ferrous and non-ferrous metals.
    FERROUS METALS                                              NON FERROUS METALS
    Contain iron, and the common used are cast iron and         Contains no iron as a basic metal, and most common 
    plain carbon steel.                                         used are copper, aluminum, lead, tin and zinc.
    Iron is alloyed with carbon or other elements like          They are non magnetic and corrosion resistance.
    tungsten, nickel, silicon, sulphur and manganese.
    These elements in various portions give metal               Have electrical conductivity and they mechanical 
    specific properties like heat resistance, elasticity        strength is low.
    plasticity and toughness.
    Iron is called ferrite, a soft grey metal and obtained      We can improve their mechanical properties by 
    from a mined ore.                                           alloying them together.
    Steel is an alloy of iron and carbon which gives steel 
    certain properties that makes it useful for certain 
    applications.
    Alloy can be defined as a combination of iron and 
    carbon.
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                              PROPERTIES OF METALS 
    Toughness
    •  It is the ability of a metal to withstand resistance force impact or hammering load.
    •  It has the ability to resist fracture when subjected to continuous bending forces in opposite directions.
    Tensile strength
    •  Is a measure of the ability of a metal to resist force acting to pull it apart and withstand stretching load without 
       breaking.
    Elasticity
    •  Is a measure of the ability a metal to be deformed under load and yet return to its original shape when load is 
       removed. 
    Plasticity
    •  Is a measure of a metal to be deformed under load and then retain the new shape when load is removed.
    Ductility
    •  Is the property that permits a metal to withstand considerable elongation under tension before breaking apart.
    Malleability
    •   Metals having the ability of being permanently extended in all directions by hammering , bending , twisting  or 
       rolling without cracking  or breaking.
    Hardness
    •  Is a measure of the ability of a metal to withstand starching, cutting or rubbing by other body or hard material.
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                                     HEAT  TREATMENT PROCESSES 
  HARDENING                                         TEMPERING                                  ANNEALLING
     •   Heat treatment is the process whereby the physical properties of a metal usually steel are changed by heating 
         it up to a certain temperature and then cooling it down. Toughness , hardness and wear are some of the 
  Steel is heated at a predetermined                Steel is heated in its harden state to     Is done by slowly heating steel to a 
         properties that can be improved by various heat treatment processes.
  temperature and then quenched rapidly in a        a tempering temperature and then           certain temperature and then 
     •   Below is processes and purposes of each.
  quenching medium such water.                      quench it in water or oil.                 allowing it to cool down very slowly.
                                                    The purpose of tempering is                Its purpose is soften steel so that it 
                                                    removes the stresses and strains           can be machined easily and to 
  The purpose of hardening is to harden steel.      induced by hardening.                      reduce grain structure.
                                                                                               To release internal stresses that 
  The other purpose is to enable steel to resist  The other purpose is to reduce               have been set up during previous 
  wear and to cut other metals.                     brittleness and increase toughness.        working of metals.
                        NORMALISING                                                       CASE HARDENING
                                                                   Low carbon steel is heated in a furnace to weaken steel and 
  Steel is heated slowly to a normalizing temperature and          refine grain. This produces hard surface skin with a thickness 
  then allow it to cool in air.                                    of 1 to 2 mm.
  The purpose for normalizing is to refine steel structure         Results of case hardening are the hard out layer that present 
  and obtain uniform structure.                                    a good wearing surface.
  To remove strains and stresses caused by cold working            The strong and tough inner core which is hardened but can 
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  and to improve steel strength.                                   resist all the shock loads to be carried by the work-piece. 
                           COLOUR CODING OF METALS
                      METAL                                         COLOUR
  Low carbon steel                               Orange
  High carbon steel                              Brown
  Case hardened steel                            Orange
  Low alloy steel                                Light purple
  Structural steel                               Red
  Steel for pressure containers                  White
  Stainless steel                                Black 
  Carbon and alloy spring steel                  Black
  Silicon chrome steel                           Black
  Cast steel                                     Blue
  Pipeline steel                                 Grey
  Steel for lifting machines                     Green
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