PROCESSING MATERIALS

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PROCESSING MATERIALS
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Processing Materials

• Materials are processed to make them more useful
  --- changing from one form to another
• Value is added by each process
• Primary Industry
• Produces basic industrial materials used to make
  basic industrial materials
• Iron ore steel structures, Crude oil
  chemicals plastics
• Rubber (latex) is heated with sulfur ---
  Vulcanization

Cotton thread
Wood paper
Steel structures
Animal Hides shoes
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Industrial Materials

• Wood
• Hard wood --- broad leaves --- deciduous, e.g.
  maple, oak
• Soft wood --- thin leaves --- coniferous, e.g.
  pine
• Plywood (a manufactured board) is made from wood
  chips and saw dust.
• Metals
• Metals, e.g. iron are used to make heavy
  structures, automobiles, planes and tools etc.
• Alloys are the combination of two or more metals
• Brass Copper Zinc, Bronze Copper
  Tin, Pewter Tin, Antimony and Copper
• Ferrous metals --- more than 50 iron
• Stainless steel containing chromium resists
  rusting

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Industrial Materials

• Ceramics
• Objects obtained from clay like materials such as
  plaster, cement, limestone and glass --- pottery,
  fiber glass, sockets, switches
• They are heated (fired) to around 2000 F in an
  oven called kiln
• Glazing is coating them with glass-like materials
• High strength ceramics are used in planes,
  automobiles
• Soda lime glass sand, lime and sodium oxide
  at around 2500 F
• Plastics
• Long chain molecules --- polymers
• Thermoplastics --- soften when heated and harden
  when cooled again, e.g. polythene bags, PVC bags
• Thermoset --- do not soften when heated. They
  rather char and burn instead, e.g. bakelite,
  Formica and plastic cups

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Industrial Materials

• How Steel is Made
• Iron ore (iron oxide) is melted with limestone
  and coke in a blast furnace
• Molten iron cools and hardens into pig iron
• Impurities are removed as slag
• Hot metal is turned into steel in basic oxygen
  furnaces (BOFs)
• Steel is also made in open-hearth furnaces and
  electric furnaces
• Huge blocks of molten steel are called ingots ---
  bars, rods and sheets
• Changing molten steel directly into basic shapes
  --- continuous casting

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Processing Materials

• Forming --- changing shape
• Separating --- removing a part
• Combining --- joining materials together
• Conditioning --- changing internal properties

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Forming Processes

• Casting
• Castings are made from molds --- ice cubes, walk
  on a beach, cake pan
• One-piece and two-piece molds
• Slip is the liquid clay poured into a two-piece
  mold
• Pressing
• Pressing is like casting with a plunger
• Meat can be pressed into shape with hands
• Powdered metal pressed and heated --- sintering
• Forging
• Heating a metal and hammering into a shape ---
  blacksmith, coins
• Hydraulic and mechanical presses use powerful
  rams --- thousand tons of force

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Forming Processes

• Extruding
• Soft metal pressed/squeezed through an opening,
  e.g toothpaste
• End products do not require much more shaping and
  machining
• Blow Molding
• Air blows the plastic into a mold, e.g plastic
  bottles
• Vacuum Forming
• A vacuum pulls the warm, soft plastic down
• The plastic clings to whatever it is drawn
  against, e.g. blister packaging

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Separating Processes

• Shearing
• Using knife-like blade for separating
• When the force gets high enough, the material
  breaks along the line of the cut
• Sawing
• Separating with a blade that has teeth
• Cutting wood along the direction of the grain ---
  Ripping
• Cutting wood across the direction of the grain
  --- Crosscutting
• Handsaws used for wood have 6-10 tpi
• Metal is cut by hand using a hacksaw --- usually
  18 tpi
• Machine saws and table saws