PROCESSING MATERIALS

1. PROCESSING MATERIALS

2. 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

3. 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

4. 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

5. 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

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

8. 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

10. 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

11. 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