lecture 5 casting Flashcards
(17 cards)
What is centrifugal casting?
A family of casting processes where the mold is rotated at high speed, distributing molten metal to outer regions of the die cavity.
Includes true centrifugal casting (horizontal and vertical) and semicentrifugal casting.
What are the parts produced by centrifugal casting?
- Pipes
- Tubes
- Bushings
- Rings
The outside shape can be round, octagonal, hexagonal, etc., while the inside shape is theoretically perfectly round.
What is shell molding?
A casting process where the cavity is a thin shell of sand held together by thermosetting resin binder.
Involves heating a metal pattern and covering it with a sand-resin mixture.
List the advantages of shell molding.
- Smoother cavity surface
- Good dimensional accuracy
- Mold collapsibility minimizes cracks
- Can be mechanized for mass production
However, it has higher costs and is difficult to justify for small quantities.
What are the steps in investment casting?
- Produce wax patterns
- Attach patterns to a sprue
- Coat with refractory material
- Form the full mold
- Heat to melt wax
- Pour molten metal
- Break away mold
This process allows for the casting of complex parts.
What are the advantages of investment casting?
- Can cast complex parts
- Close dimensional control
- Good surface finish
- Wax can be recovered for reuse
This is typically a net shape process, needing little additional machining.
What distinguishes die casting from other permanent mold processes?
The use of high pressure (7-35MPa) to force molten metal into the die cavity.
Molds in die casting are called dies.
Describe hot-chamber die casting.
Metal is melted in a container, and a piston injects liquid metal under high pressure into the die.
Suitable for low melting-point metals like zinc, tin, lead, and magnesium.
What is a cold-chamber die casting process?
Molten metal is poured into an unheated chamber from an external melting container and injected under high pressure.
It can cast high melting point metals like aluminum and brass.
List the advantages of die casting.
- Economical for large quantities
- Good accuracy (±0.076mm)
- Thin sections possible
- Rapid cooling provides good strength
However, it is limited to metals with low melting points.
What is continuous casting?
A process where molten metal is continuously poured into a mold to create a solid shape.
Often used for metals like steel and aluminum.
Define cope and drag in sand casting.
Cope is the upper half of the mold and drag is the bottom half.
Together they form the mold cavity.
What is the purpose of a riser in casting?
A reservoir in the mold that compensates for shrinkage of the part during solidification.
It helps prevent voids in the casting.
What is a gating system in casting?
The channel through which molten metal flows into the cavity from outside the mold.
It consists of a down-sprue and a runner.
Fill in the blank: The mold halves in sand casting are contained in a _______.
flask
What materials are used to make molds for die casting?
- Tool steel
- Mold steel
- Maraging steel
- Tungsten
- Molybdenum
These materials are chosen for their durability and heat resistance.
What is the main advantage of using cores in sand casting?
Cores provide internal features of the cast part.
They are typically made of sand.
