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University Tenaga National
Lecturer: Habeeb Al-Ani
HABEEB HATTAB HABEEBHABEEB HATTAB HABEEB
Office: BN-Block, Level-3, Office: BN-Block, Level-3, Room-088Room-088
Email: Email: [email protected]. No.: 7292Ext. No.: 7292
H/P No.: 0126610058H/P No.: 0126610058
University Tenaga National
Lecturer: Habeeb Al-Ani
Contemporary (Modern)
Casting Processes
University Tenaga National
Lecturer: Habeeb Al-Ani
Metal Moulds:Metal Moulds:
Made of special metals that withstandhigh temperatures of the molten mate-rials.
Made of special metals that withstandhigh temperatures of the molten mate-rials.
Used to produce large numbers of castings.Used to produce large numbers of castings.
Used to produce small-and mediumsizeUsed to produce small-and mediumsize
University Tenaga National
Lecturer: Habeeb Al-Ani
Dies:Dies:- Dies for hot and cold-chamber machine are similar in construction. - Dies are made in to halves to allow Casting removal. - Metal enters the stationary half when the die is closed.- When the die opens ejector-pins for the casting to fall from the die
University Tenaga National
Lecturer: Habeeb Al-Ani
- Die life depends on the metal cast ( Range from 10,000 filling for brass to several million for zinc).
DiesCont…
- Vents should be considered to allow the gases to escape
-Dies are provided with water channels to cool the die after injection to metal (For rapid production)
University Tenaga National
Lecturer: Habeeb Al-Ani
Die casting:Die casting:
Die – Is a metal mould into which a molten material is forced to fill the cavity of the mould.
Die – Is a metal mould into which a molten material is forced to fill the cavity of the mould.
Die-casting is accomplished using either of the following methods:Die-casting is accomplished using either of the following methods:
1- Hot chamber 2- Cold chamber
University Tenaga National
Lecturer: Habeeb Al-Ani
Hot chamber method:
The molten pot is included within the machine. An injection cylinder in
Immersed in the molten material all times. The injection cylinder, which is actuated by air or hydraulic pressure,forces the molten metal into the mould Cavity.
The molten pot is included within the machine. An injection cylinder in
Immersed in the molten material all times. The injection cylinder, which is actuated by air or hydraulic pressure,forces the molten metal into the mould Cavity.
University Tenaga National
Lecturer: Habeeb Al-Ani
University Tenaga National
Lecturer: Habeeb Al-Ani
University Tenaga National
Lecturer: Habeeb Al-Ani
University Tenaga National
Lecturer: Habeeb Al-Ani
University Tenaga National
Lecturer: Habeeb Al-Ani
University Tenaga National
Lecturer: Habeeb Al-Ani
This method is used to cast low-melting point alloys (Zinc, tin, and lead). Relatively high-melting temperature metals are not cast using this method because high temperatures cause damage to hot chamber machines.
This method is used to cast low-melting point alloys (Zinc, tin, and lead). Relatively high-melting temperature metals are not cast using this method because high temperatures cause damage to hot chamber machines.
Hot chamber method (Die casting)Cont…
University Tenaga National
Lecturer: Habeeb Al-Ani
PrinciplePrinciple
Cont…
Metal is injected into the mould by an cylinder (plunger).
The plunger maintains the pressure required during solidification (this also can be performed using compressedair). At this time the mould is closedby another cylinder.
Metal is injected into the mould by an cylinder (plunger).
The plunger maintains the pressure required during solidification (this also can be performed using compressedair). At this time the mould is closedby another cylinder.
Hot chamber method (Die casting)
University Tenaga National
Lecturer: Habeeb Al-Ani
University Tenaga National
Lecturer: Habeeb Al-Ani
Cont…
After the metal solidification the pressure is relieved, the opens and the casting is ejected by knockout pins (ejector-pins).
After the metal solidification the pressure is relieved, the opens and the casting is ejected by knockout pins (ejector-pins).
Hot chamber method (Die casting)
University Tenaga National
Lecturer: Habeeb Al-Ani
Cont… Hot chamber method (Die casting)
University Tenaga National
Lecturer: Habeeb Al-Ani
Cold chamber method:
The molten material is poured into the Injection cylinder by mechanical meansor hand. The molten material is taken from a separate container (Furnace).
The molten material is poured into the Injection cylinder by mechanical meansor hand. The molten material is taken from a separate container (Furnace).
This method is used to cast alloys with relatively high-melting temperatures and pressures.
This method is used to cast alloys with relatively high-melting temperatures and pressures.
University Tenaga National
Lecturer: Habeeb Al-Ani
PrinciplePrincipleCont…
The metals are not molten in a self-contained pot ladle the molten metalis poured in a cavity before the plunger.Cold chamber machines are designed to withstand high temperatures of thePoured metals and to provide pressureDuring the solidification process.
The metals are not molten in a self-contained pot ladle the molten metalis poured in a cavity before the plunger.Cold chamber machines are designed to withstand high temperatures of thePoured metals and to provide pressureDuring the solidification process.
Cold chamber method (Die casting)
University Tenaga National
Lecturer: Habeeb Al-Ani
Cont… Cold chamber method (Die casting)
University Tenaga National
Lecturer: Habeeb Al-Ani
Cont… Cold chamber method (Die casting)
A- The mould is closed with cores and the metal is ready to be poured by a ladle. B- The plunger forces the metal into the cavity.c- After the metal solidifies, the cores are withdrawn.D- Die opens and the casting is ejected
University Tenaga National
Lecturer: Habeeb Al-Ani
Cont… Cold chamber method (Die casting)
University Tenaga National
Lecturer: Habeeb Al-Ani
Cont… Cold chamber method (Die casting)
University Tenaga National
Lecturer: Habeeb Al-Ani
Cont… Cold chamber method (Die casting)
University Tenaga National
Lecturer: Habeeb Al-Ani
Cont… Cold chamber method (Die casting)
University Tenaga National
Lecturer: Habeeb Al-Ani
Advantage of Die casting:Advantage of Die casting:
1- Rapid Process
2- The core and die are permanent
3- Smooth surfaces of casting
4- Minimizes machining and cutting processes (less waste material than in sand castings)
University Tenaga National
Lecturer: Habeeb Al-Ani
Advantage of Die casting
5- The wall thickness is more uniform than in sand castings.
6- Waste material is low because thesprue, runners and gates are re-melted.
Cont…
7- Tolerances are less than in sand Castings.
University Tenaga National
Lecturer: Habeeb Al-Ani
1- High cost of equipment and dies (sodie casting is used in mass production)
2- Undesirable chilling of the casting (The solution: High temperature must be sustained before removing the casting)
Disadvantage of Die casting:Disadvantage of Die casting:
University Tenaga National
Lecturer: Habeeb Al-Ani
Disadvantage of Die casting
3- Metal with high coefficient of contraction should be removed from the mould immediately because of the inability of the mould to contract with the casting.
Cont…
4- Used mainly for low melting point materials.
University Tenaga National
Lecturer: Habeeb Al-Ani
Features of die casting of Brass and high melting
point metals:
Features of die casting of Brass and high melting
point metals:
The difficulty faced in die casting ofbrass is the damage and rapid oxida-tion of steel dies because of the high melting temperature. This problem has been overcome by performingthe die casting at low a temperatureas possible.
University Tenaga National
Lecturer: Habeeb Al-Ani
Features of D. cas. of Brass and high melt. point metalsCont…
So metal is can be injected in a semi-liquid or plastic state to perform casting operations at lower tempe-rature.
There are two variations of die castingProcess for BRASS:
NEXT SLIDE
University Tenaga National
Lecturer: Habeeb Al-Ani
Features of D. cas. of Brass and high melt. point metalsCont…
University Tenaga National
Lecturer: Habeeb Al-Ani
Features of D. cas. of Brass and high melt. point metalsCont…
a- Compression chamber is built in theDie .
b- Compression chamber is separatefrom the die .
University Tenaga National
Lecturer: Habeeb Al-Ani
Lower pressure permanentmoulds:
Lower pressure permanentmoulds:
- A mould is mounted over a furnace.
- The furnace is sealed through a stalk into the cavity.
Advantage: Dense, clean and AccurateCasting, less secondary machining andCutting operations.
University Tenaga National
Lecturer: Habeeb Al-Ani
Lower pressure permanent mouldsCont…
University Tenaga National
Lecturer: Habeeb Al-Ani
Gravity or permanent-MouldCasting :Gravity or permanent-MouldCasting :
No pressure is used (only gravity). It Is used for ferrous and non-ferrous metals.
University Tenaga National
Lecturer: Habeeb Al-Ani
PrinciplePrinciple
The die is closed using a cylinder and the molten metal is simply poured intothe mould cavity by hand or mechani-cal means. The metal fills the cavitybecause of the pressure created by the head of the metal poured (no plu-nger) is used to keep the casting underpressure).
The die is closed using a cylinder and the molten metal is simply poured intothe mould cavity by hand or mechani-cal means. The metal fills the cavitybecause of the pressure created by the head of the metal poured (no plu-nger) is used to keep the casting underpressure).
Gravity or permanent-mould casting Cont…
University Tenaga National
Lecturer: Habeeb Al-Ani
Casting cycle:
Pouring, cooling, ejecting, and setting the coresPouring, cooling, ejecting, and setting the cores
Gravity or permanent-mould casting Cont…
Advantage: Good finish and surface ofthe castings, capability of maintainingsmall tolerances. Disadvantage: Good High cost of equ-ipment and dies.
University Tenaga National
Lecturer: Habeeb Al-Ani
Centrifugal Casting:Centrifugal Casting:
1- The mould rotates while the metal solidifies.
PrinciplePrinciple
University Tenaga National
Lecturer: Habeeb Al-Ani
Centrifugal Casting:
1- High cost of equipment and dies (sodie casting is used in mass production)
2- Undesirable chilling of the casting (The solution: High temperature must be sustained before removing the casting)
University Tenaga National
Lecturer: Habeeb Al-Ani
Advantage:
1- No need of cores for cylindrical castings.
2- Good dense of the metal.
3- Thin walled castings can be produ- ced.
centrifugal casting Cont…
University Tenaga National
Lecturer: Habeeb Al-Ani
Methods of centrifugal casting
This method is used to produce pipes,bars, cylinders and other symmetricobjects. The mould rotates about itshorizontal or vertical axis. THREE orTWO types:
centrifugal casting Cont…
1- True Centrifugal Casting
University Tenaga National
Lecturer: Habeeb Al-Ani
centrifugal casting Cont…
b- Using a thick, highly insulated sand interface between the mould wall andthe casting. In this case, the solidifica-tion will start from the casting centerand from the wall at the same time.
a- Using a massive thick metal mould with a thick refractory coating. As a result of this design, the solidification will proceed from the mould wall toward the casting centre.
University Tenaga National
Lecturer: Habeeb Al-Ani
Finding the centrifugal force CF:
The centrifugal force is created by themould rotation about its axis. If too lowA centrifugal force is applied, the metal will slide, slip or rain.
centrifugal casting Cont…
mvr
2
CF =
University Tenaga National
Lecturer: Habeeb Al-Ani
centrifugal casting Cont…
Horizontal
University Tenaga National
Lecturer: Habeeb Al-Ani
centrifugal casting Cont…
Vertical
University Tenaga National
Lecturer: Habeeb Al-Ani
/ Methods of centrifugal casting
The mould is completely full of metal.The centre of the casting is solid but with less density then it is in the surf-ace of the casting. Usually, the centreof the casting will be removed using machining processes.
centrifugal casting Cont…
2- Simicentrifugal Casting
Advantage: Good dense surface of the metal, especially near the surface.
University Tenaga National
Lecturer: Habeeb Al-Ani
centrifugal casting Cont… / Methods of centrifugal casting
University Tenaga National
Lecturer: Habeeb Al-Ani
/ Methods of centrifugal casting
Several cavities are located around the mould axis. As the mould is rotated,the CF encourages the metal to fill the cavities through radial gates.
centrifugal casting Cont…
3- Centrifuging
Advantage: Not limited to symmetricalobjects.
University Tenaga National
Lecturer: Habeeb Al-Ani
centrifuging casting Cont… / Methods of centrifugal casting
University Tenaga National
Lecturer: Habeeb Al-Ani
Precision or investment Casting:Precision or investment Casting:
This process is used to cast unmachi-nable alloys and radioactive metals (Poor machinability).
Advantage:
1-Intricate and smooth casting.
2-Good for unmachinable metals and itCan replace die-casting.
University Tenaga National
Lecturer: Habeeb Al-Ani
Precision or investment Casting:
Disadvantage:
1- Very expensive.
Cont…
2- Limited to small parts.
3- some difficulties when cores are used .
University Tenaga National
Lecturer: Habeeb Al-Ani
Type of Precision or investment Casting
1-“Lost Wax” precision casting process.
A wax pattern is used to form a cavityIn the mould. The Wax pattern is cove-red with plaster investment. When thisplaster becomes hard the plaster mould will be heated. As a result, theWax pattern will melt away from the mould leaving a cavity having all the details of the Wax pattern.
University Tenaga National
Lecturer: Habeeb Al-Ani
Schematic illustration of investment castingSchematic illustration of investment casting
1. WAX INJECTION : Wax replicas of the desired castings are produced by injection molding. These replicas are called patterns.
University Tenaga National
Lecturer: Habeeb Al-Ani
Schematic illustration of investment castingSchematic illustration of investment casting
2. ASSEMBLY : The patterns are attached to a central wax stick, called a sprue, to form a casting cluster or assembly.
University Tenaga National
Lecturer: Habeeb Al-Ani
Schematic illustration of investment castingSchematic illustration of investment casting
3. SHELL BUILDING : The shell is built by immersing the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand. Up to eight layers may be applied in this manner.
University Tenaga National
Lecturer: Habeeb Al-Ani
Schematic illustration of investment castingSchematic illustration of investment casting
4. DEWAX : Once the ceramic is dry, the wax is melted out, creating a negative impression of the assembly within the shell.
University Tenaga National
Lecturer: Habeeb Al-Ani
5. CONVENTIONAL CASTING: In the conventional process, the shell is filled with molten metal by gravity pouring. As the metal cools, the parts and gates, sprue and pouring cup become one solid casting.
University Tenaga National
Lecturer: Habeeb Al-Ani
6. KNOCKOUT: When the metal has cooled and solidified, the ceramic shell is broken off by vibration or water blasting.
University Tenaga National
Lecturer: Habeeb Al-Ani
7. CUT OFF: The parts are cut away from the central sprue using a high speed friction saw.
University Tenaga National
Lecturer: Habeeb Al-Ani
8. FINISHED CASTINGS: After minor finishing operations, the metal castings--identical to the original wax patterns--are ready for shipment to the customer.
University Tenaga National
Lecturer: Habeeb Al-Ani
Type of Precision or investment CastingCont…
2-Plaster Mould Casting.
1- Mold is made of plaster 2- Mixed with water and additives and poured over a pattern 3- After plaster sets, pattern is removed and the mold is dried at 120 C 4- Have low Permeability – gases can not escape 5- Patterns are made of:
University Tenaga National
Lecturer: Habeeb Al-Ani
-Al alloys, -Thermosetting plastics-Brass or Zinc alloys
Type of Precision or investment CastingCont…
6-Have fine details and good surface finish 7-Form of precision casting
Plaster moulds are also not permanentbecause they are destroyed when the casting is removed.
University Tenaga National
Lecturer: Habeeb Al-Ani
Type of Precision or investment CastingCont…
University Tenaga National
Lecturer: Habeeb Al-Ani
Continuous Castings
Continuous casting process consists of continuously poring the molten metal into a mould that has the capability forrapidly chilling the metal to the pointof solidification and then withdrawingIt from mould.
University Tenaga National
Lecturer: Habeeb Al-Ani
Continuous casting
University Tenaga National
Lecturer: Habeeb Al-Ani
Continuous casting and hot rolling plant
University Tenaga National
Lecturer: Habeeb Al-Ani
Asarco process
The mould is built in the furnace. The molten metal is fed by gravity into the mould from furnace. At the mould exit,the metal solidifies and it is withdrawnby rolls. The exit consists of a graphitedie that forms the final shape of the withdrawn product. The graphite die isbuild in a cooling jacket, which uses water to cool the product at the mouldexit. The products: Bars, Rods.
University Tenaga National
Lecturer: Habeeb Al-Ani
Next Lecture:Metal Cutting
University Tenaga National
Lecturer: Habeeb Al-Ani
THANK YOU