Lecture 13 - Casting Processes Flashcards
Which casting process is also known as Lost Foam Casting?
Expendable Pattern Casting
What type of pattern is used for expendable pattern casting? Briefly explain the process
- A polystyrene pattern which evaporates upon contact with the molten metal
- The molten metal is poured, pattern evaporates, and vents into permeable sand mold
In expendable casting, what is expendable?
When molten metal is poured on the pattern, the pattern evaporates, therefore the pattern is expendable
What are 3 advantages of expendable pattern casting?
- Simple process
- Does not require parting lines, cores, risers, and minimal finishing
- Patterns are inexpensive
- Good for long production runs
How are patterns created in expendable pattern casting? What about complex patterns?
- Metal dies
- Complex patterns can be obtained by bonding multiple parts together
In expendable pattern casting, what is the pattern coated with?
The Pattern is coated in a refractory metal slury, dried, and placed in a container of compacted sand
Investment Casting is also known as…?
Lost wax casting
With regards to the pattern, what is the difference between investment casting and expendable casting? (Not talking about the material)
- The wax pattern is removed prior to casting
- Wax pattern is melted out as the mold cures allowing for a stronger mold
Comparing investment casting to expendable casting, which one costs more? Which one is more automatable?
Investment casting costs more and and expendable casting is more automatable
Both investment casting and expendable casting can be classified as “___“-Mold, “___“-Pattern Casting
Expendable, Expendable
Advantages of investment casting
- Large range of part sizes may be cast
- Little to no finishing is necessary
- Creates stronger molds than lost foam/expendable casting
Disadvantages of investment casting
- High labour
- High material cost
Slush Casting utilizes what property? What is the result of applying this concept?
- According to Chvorinovs rule, a piece begins to solidfy at the edges and becomes thicker with time.
- Using this concept, the remaining slush that still has yet to cool can be poured out which allows for thin walled, hollow castings to be made
What is slush casting suitable for? What kind of metals?
- Low production runs of non-structural components in materials
- Zinc, tin, and lead alloys (ie low melting point alloys)
In die casting, molten metal is “____” into a “__ ____”. What is the pressure range during this process?
Molten metal is “forced” into a “die cavity” at pressures of 0.7-700MPa
What are the two types of chambers used in Die Casting?
Hot and Cold chambers
Briefly describe the process of a hot chamber in Die casting?
Metal is kept in a furnace pot, and forced into the mold by a plunger and held under pressure until solidifed
In die casting, hot chambers are suitable for…? And has a “___” production rate
- Suitable for low melting alloys
- High production rate
What is a Cold Chamber with respect to Die Casting?
Metal is put into a shot chamber that is NOT heated
What type of metals would you use for cold chamber, in die casting? Name examples
Useful for high temp alloys such as Cu, Al, and ferrous metals
What type of forces are used in centrifugal casting?
Utilizes inertial force caused by rotation to force metal into a mold cavity
What role does density play in centrifugal casting?
Heavier particles will go to the outer radius of the mold.
In centrifugal casting, what causes impurites to be collected? What are some impurities likely to be present and how are they removed?
- Due to density differences, impurities collect at a certain radius
- Can be useful for collecting impurities like dross (whic is oxides solidfied) and fluxes which is removed by finish machining
What two processes does Squeeze Casting incorporate?
Casting and Forging
