Materials

Materials

1. Casting

   • Need post-cast forging, rolling etc
     • ingot casting
       • up-hill teeming
         • teeming ladel down pipe fill ingot mould from bottom
       • down-hill teeming
         • fill mould from top down
     • continuous casting
       • molten steel enters cooled copper mould from tundish
         • surface steel=rapidily cools
           • thin solid shell
       • improved quality, less segregation, fewer inclusions
       • less waste than ingot casting
       • higher productivity/efficiency=straight into rolling mill
   • casting direct to final shape
     • sand casting
       • green sand
       • shell moulding
       • chemically bonded sand
       • make mould = pattern is pressed into sand.
         • bottom of mould = drag, top = cope
         • pattern removed=two halves put together
           • molten metal poured into cavity
     • investment casting
       • lost wax
         • precision casting process
           • make pattern from casting wax-injection moulding
             • tool made out of steel, cost around £1,000,000 - 6 month lead time
             • dip tree in slurry-refractory sand-repeat- 5/10 mm shell
               • melt/vaporise wax=hollow mould
                 • pre heat shell, pour in alloy, solidify, remove shell then machine part
           • complex shapes, small features with good surface finish, cast up to 100kg, economic small + large batch sizes
             • most metals with Tmelt less than 2500 degrees c.
               • Al alloys, Ti alloys, precious metals
       • lost foam
       • plaster moulding
     • die casting
       • Low P
       • Gravity
       • high pressure
       • repeated use of permanent (steel) die
         • rapid cooling = high thermal conduction of steel die
           • causes small equi-axed grains
         • the die
           • have high temp stability + good thermal conductivty
             • steel/graphite
           • low adhesion between casting and die
             • coat with graphite/silicone
           • component+die =designed to release quickly
           • complex design=long lead time + high cost
       • high production rate
     • vacuum casting stops oxidation
     • preferred when: large complicate shape, quality/strength = not important, ductility of alloy is too low

2. powder manufacturing

3. forming

4. Earing

5. Heat Trasnfer