Metal Casting Processes - Assignment 2

For which one of the following reasons is a green mold named: (a) green is the color of the mold, (b) moisture is contained in the mold, (c) mold is cured, or (d) mold is dry?

(b) moisture is contained in the mold

Which one of the following casting metals is most important commercially: (a) aluminum and its alloys, (b) bronze, (c) cast iron, (d) cast steel, or (e) zinc alloys?

(c) cast iron

Which one of the following casting processes is the most widely used: (a) centrifugal casting, (b) die casting, (c) investment casting, (d) sand casting, or (e) shell casting?

(d) sand casting

Given that Wm = weight of the molten metal displaced by a core and Wc = weight of the core, the buoyancy force is which one of the following: (a) downward force = Wm + Wc, (b) downward force = Wm - Wc, (c) upward force = Wm + Wc, or (d) upward force = Wm - Wc?

(d) upward force = Wm - Wc

Investment casting is also known by which one of the following names: (a) fast-payback molding, (b) full-mold process, (c) lost-foam process, (d) lost-pattern process, or (e) lost-wax process?

(e) lost-wax process

Which of the following metals would typically be used in die casting (three best answers): (a) aluminum, (b) cast iron, (c) steel, (d) tin, (e) tungsten, and (f) zinc?

(a) aluminum (d) tin (f) zinc

Which of the following are advantages of die casting over sand casting (four best answers): (a) better surface finish, (b) closer tolerances, (c) higher melting temperature metals, (d) higher production rates, (e) larger parts can be cast, and (f) mold can be reused?

(a) better surface finish (b) closer tolerances (d) higher production rates (f) mold can be reused

In sand casting, the volumetric size of the pattern is (a) bigger than, (b) same size as, or (c) smaller than the cast part?

(a) bigger than

Which of the following casting processes are permanent mold operations (two correct answers): (a) centrifugal casting, (b) die casting, (c) expanded polystyrene process, (d) sand casting, (e) shell molding, (f) slush casting, and (g) vacuum molding.

(a) centrifugal casting (e) slush

In plaster mold casting, the mold is made of which one of the following materials: (a) Al2O3, (b) CaSO4-H2O, (c) SiC, or (d) SiO2?

(b) CaSO4-H2O

Cupolas are furnaces used to melt which of the following metals (one best answer): (a) aluminum, (b) cast iron, (c) steel, or (d) zinc?

(b) cast iron

Shell molding is best described by which one of the following: (a) casting operation in which the molten metal has been poured out after a thin shell has been solidified in the mold, (b) casting process in which the mold is a thin shell of sand bonded by a thermosetting resin, (c) sand-casting operation in which the pattern is a shell rather than a solid form, or (d) casting operation used to make artificial sea shells?

(b) casting process in which the mold is a thin shell of sand bonded by a thermosetting resin

Which of the following qualifies as a precision-casting process (two correct answers): (a) ingot casting, (b) investment casting, (c) plastermold casting, (d) sand casting, and (e) shell molding?

(b) investment casting

Silica sand has which one of the following compositions: (a) Al2O3, (b) SiO, (c) SiO2, or (d) SiSO4?

(c) SiO2

Which of the following casting processes are expendable mold operations (four correct answers): (a) centrifugal casting, (b) die casting, (c) investment casting, (d) low pressure casting, (e) sand casting, (f) shell molding, (g) slush casting, and (h) vacuum molding?

(c) investment casting (e) sand casting (f) shell molding (h) vacuum molding

A misrun is which one of the following defects in casting: (a) globules of metal becoming entrapped in the casting, (b) metal is not properly poured into the downsprue, (c) metal solidifies before filling the cavity, (d) microporosity, and (e) "pipe" formation?

(c) metal solidifies before filling the cavity

What is a cupola?

A vertical cylindrical furnace equipped with a tapping spout near its base

What are the most common metals used in die casting?

Aluminum, brass, and magnesium alloys

Name the two basic categories of casting processes.

Expendable mold and permanent mold

Which die-casting machines usually have a higher production rate, coldchamber or hot-chamber, and why?

Hot-chamber, because the cold chamber needs to ladle in the liquid metal from an external source

What are some of the general defects encountered in casting processes? Name and briefly describe three.

Misruns, cold shuts- two portions of metal flow together but don't fuse due to premature freezing, cold shots- from splattering while pouring- solid globules of metal entrapped, shrinkage cavity- depression in the surface or an internal void- solved by proper riser design, microporosity, hot tearing

There are various types of patterns used in sand casting. What is the difference between a split pattern and a match-plate pattern?

Split- consist of two pieces, match- plate is two pieces of the split pattern are attached to opposite sides of a wood or metal plate

What properties determine the quality of a sand mold for sand casting?

Strength, permeabilitiy, thermal stability, collapsibility, reusability

What is a chaplet?

Support made of metal with a higher melting temp than the casting metal

What is flash in die casting?

The liquid metal under high pressure squeezes into the small space between the die halves at the parting line or into clearances around the cores and ejector pins

What are some of the operations required in sand casting after the casting is removed from the mold?

Trimming, removing the core, surface cleaning, inspection, repair, heat treat

What is the difference between vacuum permanent-mold casting and vacuum molding?

Vacuum molding- uses sand mold held by vacuum pressure refers to the mold. Vacuum permanent- vacuum is used to draw the metal into the mold cavity