Chapter 11- Metal Casting Process

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

The operations include (1) trimming, in which the sprues, runners, risers, and flash are removed, (2) core removal, (3) surface cleaning, (4) inspection, (5) repair if needed, (6) heat treatment, and (7) machining.

9. (A) What is flash in die casting?

Flash is a thin portion of the metal at the exterior of a casting that results from the molten metal being squeezed into the spaces between the die halves of the mold at the parting line, or into the clearances around the cores and ejector pins.

3. (A) What is investment casting?

In investment casting, a pattern made of wax is coated with a refractory material to make the mold, after which the wax is melted away prior to pouring the molten metal. The term investment comes from one of the less familiar definitions of the word invest, which means "to cover completely," this refers to the coating of the refractory material around the wax patter

4. What is the other name for investment casting?

Investment casting is also known as the lost-wax process because the wax pattern is lost from the mold prior to casting.

10. 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?

LOST Wax pocess

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) the mold is cured, or (d) the mold is dry?

MOISTURE IS CONTAINED IN MOLD

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?

Sand CastinG

7. What does the term semipermanent mold casting refer to?

Semipermanent mold casting refers to a permanent-mold casting operation in which a sand core is used.

1. What is shell molding?

Shell molding is a casting process in which the mold is a thin shell, typically 9 mm (3/8 in) made of sand held together by a thermosetting resin binder. The surface of the shell-mold cavity is smoother than a conventional green-sand mold, and this smoothness permits easier flow of molten metal during pouring and better surface finish on the final casting.

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

SiO2

7. The expanded-polystyrene casting process uses a mold of sand packed around a polystyrene foam pattern that vaporizes when the molten metal is poured into the mold: (a) True or (b) false?

TRUE

9. In the expanded-polystyrene casting process, a new pattern and a new mold are required for every casting produced: (a) True or (b) false?

TRUE

6. What is the Antioch process?

The Antioch process refers to the making of a mold that is 50% sand and 50% plaster, heated in an autoclave, and then dried. This mold has greater permeability than a plaster mold.

2. What are some of the other names for the expanded-polystyrene casting process?

The other names for the expanded-polystyrene casting process listed in the text are the lost-foam process, the lost-pattern process, the evaporative-foam process, and the full-mold process

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

The usual properties are (1) strength ability to maintain shape in the face of the flowing metal, (2) permeability ability to allow hot air and gases to escape from the cavity, (3) thermal stability ability to resist cracking and buckling when in contact with the molten metal, (4) collapsibility ability to give way during shrinkage of the solidified casting, and (5) reusability can the sand be reused to make other molds?

8. What is vacuum permanent mold casting?

Vacuum permanent mold casting is a form of low pressure casting in which a vacuum is used to draw molten metal into the cavity.

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

aluminum, tin and zinc

Thixomolding is a semi-solid metal casting process used for which one of the following metals: (a) aluminum, (b) magnesium, (c) manganese, or (d) titanium?

b) magnesium

Relative to the size of the cast part in sand casting, the volumetric size of the pattern is which one of the following: (a) bigger, (b) same size or (c) smaller?

bigger

8. Which three of the following are other names for the expanded-polystyrene casting process: (a) aerated-plastic casting, (b) disappearing-pattern process, (c) evaporative-foam process, (d) lost-foam process, (e) lost-pattern process, (f) polystyrene-foam molding, and (g) vaporizing-foam casting?

c) evaporative-foam process, (d) lost-foam process, (e) lost-pattern process

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

cast iron

5. 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 on the surface of the mold, (b) casting process in which the mold is a thin shell of sand bonded by a thermosetting resin, (c) crushed sea shells are used to make the mold, or (d) sand-casting operation in which the pattern is a shell rather than a solid form?

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

31. An indirect fuel-fired furnace is an alternative name for which one of the following furnace types: (a) crucible furnace, (b) cupola, (c) electric-arc furnace, or (d) induction furnace?

crucible furnace

12. To make molds containing multiple cavities, the individual patterns are attached to a structure called which one of the following: (a) mold branch, (b) mold channel, (c) multi-mold, (d) pattern tree, or (e) runner pattern?

pattern tree

11. The mold in investment casting is made of which two of the following materials: (a) clay, (b) plaster, (c) sand, (d) silica, (e) thermosetting resin, or (f) wax?

plaster and silica

32. Surface cleaning of the solidified casting is most important in which one of the following casting processes: (a) die casting, (b) liquid-metal casting, (c) sand casting, (d) shell casting, or (e) true centrifugal casting?

sand casting

15. Ceramic-mold casting is similar to plaster-mold casting, except that the mold is made of refractory ceramic materials that can withstand higher temperatures than plaster: (a) True or (b) false?

true

17. Steel can be cast in permanent-mold processes, but because of its high melting temperatures, the mold must be made of a refractory material: (a) True or (b) false?

true

18. Unlike expendable molds, permanent molds do not collapse, so the mold must be opened before appreciable cooling contraction occurs in order to prevent cracks from developing in the casting: (a) True or (b) false?

true

19. Slush casting is a permanent-mold process in which a hollow casting is formed by inverting the mold after partial freezing at the mold surface to drain the liquid metal in the center: (a) True or (b) false?

true

Which one of the following is the name of the casting process in which molten metal is poured into a rotating mold to produce a tubular part: (a) centrifuge casting, (b) semicentrifugal casting, or (c) true centrifugal casting?

true centrifugal casting

20. Low-pressure casting and vacuum permanent mold casting are similar. Which one uses lower-than-atmospheric air pressure in the mold to draw the molten metal into the cavity: (a) low-pressure casting or (b) vacuum permanent mold casting?

vacuum permanent mold casting

16. Which three of the following are metals commonly cast in permanent mold casting: (a) aluminum, (b) brass, (c) gold, (d) magnesium, (e) nickel, (f) steel, and (g) tungsten?

(a) aluminum, (b) brass, (d) magnesium

24. Which four of the following are advantages of die casting over sand casting: (a) better surface finish, (b) closer tolerances, (c) higher melting-temperature metals can be cast, (d) higher production rates, (e) larger parts can be cast, (f) mold can be reused, and (g) no flash is formed between the die halves?

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

25. , Which two of the following names are applied to processes in which molten metal is poured into a heated lower die, and the upper die is closed to create the mold cavity only after solidification begins: (a) liquid-metal casting, (b) liquid-metal forging, (c) rheocasting, (d) squeeze casting, or (e) thixocasting?

(b) liquid-metal forging, (d) squeeze casting

6. Compared to sand casting, shell molding has which four of the following features: (a) better dimensional accuracy, (b) better surface finish on casting, (c) easier flow of molten metal during pouring, (d) less expensive pattern, (e) more expensive metal pattern is required, (f) worse dimensional accuracy, and (g) worse surface finish on casting?

.(a) better dimensional accuracy, (b) better surface finish on casting, (c) easier flow of molten metal during pouring (e) more expensive metal pattern is required

A) What is a cupola?

A cupola is a vertical cylindrical furnace equipped with a tapping spout near its base. Cupolas are used for melting cast irons.

3. What is the difference between a match plate pattern and a cope-and-drag pattern?

A match plate pattern consists of the two split patterns attached to opposite sides of a plate. A cope-and-drag pattern consists of the two split patterns attached to two separate plates, one for the cope and the other for the drag.

1. What is a pattern in sand casting?

A pattern is a full-sized model of the part, enlarged to account for shrinkage and machining allowances in the final casting.

13. 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?

CaSO4

21. In hot-chamber die-casting machines, molten metal is poured into an unheated chamber from an external melting container, and a piston is used to inject the metal under high pressure into the die cavity: (a) True or (b) false?

(b). The description is for a cold-chamber die-casting machine.

14. An advantage of a plaster mold is that it is permeable, thus allowing escape of gasses from the mold cavity: (a) True or (b) false?

(b). The plaster mold is not permeable, thus limiting escape of gases. This is a disadvantage.

4. (A) What is the difference between a pattern and a core?

A pattern is a full-scale model of the part to be cast; it is used to form the cavity in the mold. A core is a full-scale model of the interior surfaces of the part, inserted into the mold cavity prior to pouring so that the molten metal will flow and solidify between the mold cavity and the core to form the casting's external and internal surfaces.

2. What is the difference between a split pattern and a match plate pattern?

A split pattern is a pattern that consists of two pieces. A match plate pattern consists of the two split patterns attached to opposite sides of a plate.

5. Why are wood patterns generally unsatisfactory for making the molds in plaster-mold casting?

Because the plaster of Paris mixture packed around the pattern contains water which degrades the wood pattern.

5. What is a chaplet?

Chaplets are metal supports of various designs used to hold the core in place in the sand mold.

10. What is the difference between true centrifugal casting and semi centrifugal casting?

In true centrifugal casting, a tubular mold is used and a tubular part is produced. In semi centrifugal casting, the shape is solid; an example is a railway wheel. The mold is rotated so that centrifugal force is used to distribute the molten metal to the exterior of the mold so that the density of the final metal is greater at the outer sections