Casting Flashcards
Casting
Pouring molten metal into a mold cavity to form into desired shape
Pouring basin
The hole the molten metal gets poured into
Sprue funnel
Tapered channel that brings metal into well
Gating system
Traps contaminants, reduces turbulence, prevents premature cooling, and helps avoid gas entrapment
Dross/slag
Oxidized metal that has reacted with air and other gases
Which part of a mold cools first?
The walls, it’ll cool from the outside inwards
When does most shrinkage occur?
During phase changes
Continuous casting
Molten metal is extruded into a continuous bar
Disposable mold types
Sand casting
Shell mold casting
Polystyrene casting
Investment casting
Plaster/ceramic mold casting
Types of cast patterns
One piece
Split (cavity formed by 2 sides)
Match plate (contains multiple splits)
Die casting
Molten metal is injected into mold cavity at high pressure
Low-pressure casting
Molten metal is forced into mold cavity at low pressure that is maintained until it solidifies
Centrifugal casting
Molten metal is distributed into cavities by centrifugal forces, primarily used for long, cylindrical parts
Slush casting
Hollow cast created by pouring liquid metal out after outside has partially solidified
Squeeze casting
Combines casting and forging, molten metal is poured into preheated dies that are then clamped shut
Hot chamber casting
Molten metal is forced into cavity with piston, allows fast cycle times (esp with low melting point metals)
Cold chamber casting
Done at higher pressures than hot chamber casting, used for higher melting point metals
Slow cooling rates result in…
coarse dendritic structures
High cooling rates result in…
finer structures with less spaces between dendrite arms
When grain size decreases…
Strength, ductility, and chances of cracks increase
Microporosity decreases
Anisotropic properties
Properties that aren’t uniform across a material
Casting defects
Flash
Cavities
Cracks & hot tears
Cold shut
Defective surface
Misrun
Inclusions
Flash
Extra material that swells out
Hot tears
Caused by metal being constrained from shrinking freely
Cold shut
Part doesn’t fully fuse because of premature solidification
Misrun
Not enough metal results in an incomplete cast
Mold design considerations
Avoid sharp corners and large radii
Uniform thickness required
Use ribs to reduce warping
Disposable casting costs ___ and is better for a ___ number of parts.
Permanent casting costs ___ and is better for a ___ number of parts.
less; lower
more; higher
