die casting gravity semi permanent mould or permanent mould cold chamber hot chamber (heating...
TRANSCRIPT
DIE CASTING
GRAVITY SEMI PERMANENT MOULDOR PERMANENT MOULD
COLD CHAMBER HOT CHAMBER
(HEATING CHAMBER) OUTSIDE THE MACHINE
INTEGRAL WITH THE MACHINE
PERMANENT MOULD OR GRAVITY DIE CASTING
*METALLIC MOULDS USED *TWO HALVES OF DIES- ONE FIXED, ONE MOVABLE
•VERY CLOSE TOLERANCE CASTINGS, MORE STRENGTH, LESS POROUS
•-BETTER SURFACE FINISH COMPARED TO SAND CASTING
•-SURFACE FREE FROM SAND & DENSITY HEAVY
ONLY FOR SMALL AND MEDIUM SIZE CASTINGS
FOR NON FERROUS, MAINLY
LARGE QUANTITY, BUT IDENTICAL PIECES ONLY
SEMIPERMANENT DIECASTING• DIE PRESSURE AT 20 TO 20,000 ATM
• PRESSURE FILL SOLIDIFICATION
• FOR NONFERROUS METALS
• FOR INTRICATE SHAPES
• CLOSE TOLERANCES POSSIBLE
• FOR MASS PRODUCTION, >10,000
1. A GOOD DIE SET MECHANISM2. MEANS FOR FORCING METAL3. DEVICE TO KEEP DIE HALFS PRESSED4. ARRANGEMENT FOR AUTOMATIC REMOVAL OF CORES- IF ANY5. EJECTOR PINS
TWO TYPES OF PRESSURE DIE CASTING COLD CHAMBER-
HEATING CHAMBER OUTSIDE THE MACHINE
- FOR Al, Mg, Cu, AND HIGH MELTING ALLOYS
HOT CHAMBER-
HEATING INTEGRAL WITH THE HANDLING
GOOSE NECK MECHANISMS WIDELY USED
FOR LOW MELTING ALLOYS- Zn, Pb, Etc.
ALSO VACUUM DIE CASTING MACHINES- SPACE BETWEEN THE DIES AND PASSAGE VACUUMISED BEFOR POURING-
SUBMERGED PLUNGE TYPE, DIRECT AIR DIE CASTING MACHINES
2
3
1
12
3
D.A.D.C. MACHINE – showing two positions of pot
ANOTHER TYPE OF D.A.D.C. MACHINE
A TYPICAL DIE
ECCENTRIC CLAMPING
MOULD / DIE HALFVENT HOLE POURING
BASIN
MOULD CAVITY
CENTRIFUGAL CASTINGTRUE- C.I. PIPES, LINERS, BUSHES, CYLINDER BARRELS ETC.SEMI- CENTRE CORE FOR INNER SURFACE- SHAPE BY MOULD AND CORE, MAINLY NOT BY CENRTRIFUGAL ACTION- Eg:FLYWHEELSPRESSURE OR CENTRIFUGAL CASTING- ALSO TERMED AS CENTRIFUGINGFOR NON SYMMETRICAL SHAPES MOULD WITH ANY SHAPE PLACED AT CERTAIN DISTANCE FROM AXIS
CENTRIFUGING PROPERTIES OF CASTING DEPEND ON
DISTANCE FROM AXIS
SQUEEZE CASTINGDIE, PUNCH, EJECTOR PIN
PARTS OF NEAR-NET SHAPE MADE, COMPLEX AND FINE
SURFACE DETAILS OBTAINED
FOR FERROUS & NON FERROUS
CENTRIFUGING PROPERTIES OF CASTING DEPEND ON
DISTANCE FROM AXIS
SQUEEZE CASTINGDIE, PUNCH, EJECTOR PIN
PARTS OF NEAR-NET SHAPE MADE, COMPLEX AND FINE
SURFACE DETAILS OBTAINED
FOR FERROUS & NON FERROUS
SQUEEZE CASTING• DEVELOPED IN 1960’S (also called liquid forging)• SOLIDIFICATION OF MOLTEN METAL UNDER HIGH
PRESSURE (pressure application when liquid partially solidifies 70 to 140 MPa)
• A COMBINATION OF CASTING & FORGING• DIE, PUNCH, EJECTOR PIN • PUNCH KEEPS ENTRAPPED GASES IN SOLUTION,
RAPID COOLING DUE TO HIGH PRESSURE DIE- METAL INTERFACE
• PARTS OF NEAR-NET SHAPE MADE, COMPLEX AND FINE SURFACE DETAILS OBTAINED. No riser needed
• FOR FERROUS & NON FERROUS• AUTOMOTIVE WHEELS, SHORT BARRELED CANNONS
ETC.
SINGLE CRYSTAL GROWING (S.C.G.)• FOR SEMICONDUCTOR INDUSTRY
• CRYSTAL PULLING METHOD-
CZOCHRALSKI PROCESSCZOCHRALSKI PROCESS• SEED CRYSTAL DIPPED INTO THE MOLTEN
METAL, PULLED SLOWLY, (AT 10 m/ s), WITH ROTATION
• LIQUID METAL SOLIDIFIES ON THE SEED AND CRYSTAL STRUCTURE CONTINUED THROUGHOUT
CASTING TECHNIQUES FOR SINGLE CRYSTAL GROWING (S.C.G.)
CONVENTIONAL USE OF CERAMIC MOULD
GRAINS WITH THE ABSENCE OF THERMAL GRADIENT
DIRECTIONAL SOLIDIFICATION PROCESS
CERAMIC MOULD PREHEATED.
MOULD SUPPORTED BY WATER COOLED CHILL PLATES.
AFTER POURING, ASSEMBLY LOWERED
CRYSTALS GROW AT CHILL PLATE SURFACE UPWARD. COLUMNAR GRAINS FORM
CASTING TECHNIQUES FOR SINGLE CRYSTAL GROWING (S.C.G.)
• POLYCRYSTALLINE- ANISOTROPY• SINGLE CRYSTAL- PROPERTIES SAME IN
ALL DIRECTIONS• CASTING OF GAS TURBINE BLADES BY
S.C.G.
CONVENTIONAL
• USE OF CERAMIC MOULD
GRAINS- AS WITH THE ABSENCE OF THERMAL GRADIENT
PRESENCE OF GRAIN BOUNDARIES- MAKES STRUCTURE SUSCEPTIBLE TO CREEP AND CRACKING ALONG BOUNDARIES
DIRECTIONAL SOLIDIFICATION PROCESS, (1960’s)
CERAMIC MOULD PREHEATED. MOULD SUPPORTED BY WATER COOLED CHILL
PLATES.AFTER POURING, ASSEMBLY LOWERED CRYSTALS GROW AT CHILL PLATE SURFACE
UPWARD. COLUMNAR GRAINS FORMBLADE DIRECTIONALLY SOLIDIFIED WITH
LONGITUDINAL- NOT TRANSVERSE- GRAIN BOUNDARIES. THUS STRONGER
SINGLE CRYSTAL BLADES, (1967),MOULD HAS CONSTRICTION IN THE SHAPE OF
CORK SCREWTHIS CROSS SECTION ALLOWS ONLY ONE
CRYSTAL TO FIT THROUGHWITH THE LOWERING, SINGLE CRYSTAL GROWS
UPWARD THROUGH CONSTRICTIONSTRICT CONTROL OF MOVEMENT NEEDEDTHERE IS LACK OF GRAIN BOUNDARIES, MAKES
RESISTANT TO CREEP AND THERMAL SHOCK.--EXPENSIVE
FLOATING –ZONE METHOD
• POLYCRYSTALLINE ROD (SILICON)- ALLOWED ALLOWED TO REST ON A SINGLE CRYSTALTO REST ON A SINGLE CRYSTAL
• INDUCTION COIL HEATS THE PIECES
• COIL MOVED UPWARD SLOWLY (20 m/ s)
• SINGLE CRYSTAL GROWS UPWARD WITH ORIENTATION MAINTAINED
• THIN WAFERS CUT FROM ROD, CLEANED, POLISHED
• USE IN MICROELECTRONIC DEVICES