cap 6 Materiales

Question 1

1. With the exception of a very small volume of a few metals produced by electrolytic or pure chemical methods, all material used in metal manufacturing starts out as a(n):

a. billet.
b. slab.
c. ingot.
d. casting.

Answer 1

d. casting.

Question 2

2. The noise created by grain structure and the rough surface conditions on many castings make inspection by which of the following NDT methods difficult?

a. Acoustic emission testing.
b. Ultrasonic testing.
c. Radiographic testing.
d. Electromagnetic testing.

Answer 2

b. Ultrasonic testing.

Question 3

3. Patterns can be a number of different styles but are always the shape of the finished part and roughly the same size as the finished part with slightly oversized dimensions. What is the reason for leaving a finished part with slightly oversized dimensions?

a. To allow for expansion.
b. To allow for shrinkage.
c. To allow for weight variations.
d. To allow for density variations.

Answer 3

b. To allow for shrinkage.

Question 4

4. The freezing or solidification of a liquid from the outside of a casting toward the center is referred to as:

a. progressive solidification.
b. directional solidification.
c. normal solidification.
d. forced solidification.

Answer 4

a. progressive solidification.

Question 5

5. The freezing or solidification of a liquid from one part of a casting to another, such as from one end to the other, is referred to as:

a. normal solidification.
b. forced solidification.
c. progressive solidification.
d. directional solidification.

Answer 5

d. directional solidification.

Question 6

6. Hot spots are areas of a casting that have the highest temperature immediately after pouring. These areas will normally take longer to solidify and need to be located as near as possible to:

a. gates and runners.
b. the down sprue.
c. sources of feed metal.
d. designated scrap locations.

Answer 6

c. sources of feed metal.

Question 7

7. Drops of splashed metal that lose heat, freeze, and then become entrapped in globules that do not completely join with the molten metal create a discontinuity called:
   a. cold shut.
   b. cold lap.
   c. cold shot
   d. cold spot.

Answer 7

c. cold shot

Question 8

8. As metal is poured into a mold it may freeze off in a thin section and then be met by molten metal from another direction. The discontinuity that is formed at this location is referred to as a:

a. cold shut.
b. cold lap.
c. cold shot
d. cold spot.

Answer 8

a. cold shut.

Question 9

9. As a casting freezes or solidifies, thicker sections may require additional metal to draw from during the cooling process. These attachments are called:

a. shrink protectors.
b. risers.
c. reservoirs.
d. vertical pools.

Answer 9

b. risers.

Question 10

10. Devices made of steel, cast iron, or copper that are inserted strategically into a mold cavity to promote directional solidification are called:

a. blocks.
b. rods.
c. chills.
d. chaplets.

Answer 10

c. chills.

Question 11

11. The three stages of shrinkage or contraction are liquid contraction, solidification contraction, and:

a. final contraction.
b. cold contraction.
c. shrinkage contraction.
d. solid contraction.

Answer 11

d. solid contraction.

Question 12

12. This type of shrinkage is compensated for by the pattern makers’ knowledge of each specific material’s dimensional loss from cooling to room temperature from a liquid state:
    a. liquid contraction.
    b. solidification contraction.
    c. solid-state contraction.
    d. volumetric contraction.

Answer 12

c. solid-state contraction

Question 13

13. Cast iron is often melted in a furnace that is similar to a blast furnace, which produces a continuous supply required by large production foundries. This type of melting equipment is referred to as a(n):

a. crucible furnace.
b. cupola furnace.
c. induction furnace.
d. electric arc furnace.

Answer 13

b. cupola furnace.

Question 14

14. Crucible furnaces (often with lift-out crucibles) are used primarily for nonferrous materials for small-volume work. Crucible furnaces are generally limited to what capacity?

a. Less than 4.5 kg (10 lb) of material.
b. Less than 22.7 kg (50 lb) of material.
c. Less than 45.4 kg (100 lb) of material.
d. Less than 226.8kg (500 lb) of material.

Answer 14

c. Less than 45.4 kg (100 lb) of material.

Question 15

15. A furnace with electrical coils built into the walls to create high-frequency alternating magnetic fields, which causes internal eddy currents and then uses the heat dissipated from the eddy currents to melt the material, is called a(n):

a. crucible furnace.
b. cupola furnace.
c. induction furnace.
d. electric arc furnace.

Answer 15

c. induction furnace.

Question 16

16. The most commonly used mold material for the casting process is:

a. ceramic.
b. sand.
c. wood,
d. polystyrene foam.

Answer 16

b. sand.

Question 17

17. When making a basic sand mold there is often a need for internal cavities (holes) or surface configurations that cannot be a part of the main pattern. These details are often inserted into the mold using:
    a. hand tools.
    b. post-casting machining.
    c. cores.
    d. chills.

Answer 17

c. cores.

Question 18

18. A green sand mold contains which of the
    following ingredients?

a. Sand, water, and green coloring.
b. Sand, clay and a green binding agent.
c. Sand, clay, and copper oxide.
d. Sand, clay, and moisture.

Answer 18

d. Sand, clay, and moisture.

Question 19

19. To facilitate removing the pattern from the mold, patterns must be designed with:

a. handles on both sides.
b. suitable draft angles.
c. lifting eyes.
d. numerous removable pieces.

Answer 19

b. suitable draft angles.

Question 20

20. Jolting and squeezing, manual ramming, and sand slinging are all different methods of:
    a. compacting a mold.
    b. coring a mold.
    c. pressurizing a mold.
    d. containing a mold.

Answer 20

a. compacting a mold.

Question 21

21. The ability of a finished sand core to withstand its own weight without sagging in the mold and be strong enough so that its own buoyancy, as liquid rises around it will not cause it to break or shift is called:

a. tensile strength.
b. yield strength.
c. molecular strength.
d. dry strength.

Answer 21

d. dry strength.

Question 22

22. Cores are designed to______after the molten material solidifies.
    a. remain solid
    b. resist heat
    c. collapse
    d. strengthen the mold

Answer 22

c. collapse

Question 23

23. Small metal supports with broad-surfaced ends that are designed to support or separate cores from the mold cavity are called:

a. cores.
b. nails.
c. chaplets.
d. spreaders.

Answer 23

c. chaplets.

Question 24

24. Most of the benefits of a dry sand mold can be obtained by subjecting the internal surfaces of the mold to heat from torches, radiant lamps, hot dry air, or electric heating elements in a technique called:

a. partial drying.
b. skin drying.
c. surface drying.
d. superficial drying.

Answer 24

b. skin drying.

Question 25

25. Occasionally, molds are made for castings that weigh several hundred metric tons. Because these molds cannot be moved about and contain high hydraulic head pressure, they are often constructed in: a. several pieces. b. more than one flask. c. larger facilities. d. floor or pit molds.

Answer 25

d. floor or pit molds.

Question 26

26. What type of materials are cast from plaster of parís molds with additives, such as talc, asbestos, silica flour, and other materials, to vary the mold properties? a. Nonferrous. b. Ferrous. c. Nonporous. d. Porous.

Answer 26

a. Nonferrous.

Question 27

27. Variations of this type of casting include making a new pattern for every mold using wax, frozen mercury, or low-melting point thermoplastics. a. Die casting. b. Expendable plaster mold casting. c. Investment casting. d. Lost foam casting.

Answer 27

c. Investment casting.

Question 28

28. Permanent mold casting is different from die casting because: a. die casting is done by applying pressure to the liquid metal. b. permanent mold casting Is done by applying pressure to the liquid metal. c. die casting molds are made from metal. d. permanent die molds are made from metal.

Answer 28

a. die casting is done by applying pressure to the liquid metal.

Question 29

29. Hot chamber and cold chamber are both which type of casting method? a. Permanent mold casting. b. Investment casting. c. Green sand casting. d. Die casting.

Answer 29

d. Die casting

Question 30

30. At one time, the principle product produced by this casting method was sewer pipe: a. lost foam casting. b. investment casting. c. centrifugal casting. d. die casting.

Answer 30

c. centrifugal casting.

Question 31

31. As a casting cools, the material begins to crystallize, first forming fine equiaxed crystals at the surface followed by columnar growth as solidification progresses. The third phase of growth produces: a. additional fine equiaxed crystals until complete solidification. b. coarse equiaxed crystals until complete solidification. c. columnar growth continues unchecked to solidification. d. a single crystal whose size depends on material thickness.

Answer 31

b. coarse equiaxed crystals until complete solidification.

Question 32

32. During columnar crystalline growth the temperature gradient is small and growth may occur on the sides of the columns. This produces a particular type of structure known as: a. columnar expansión. b. amorphous crystallization. c. interlocking crystallization . d. dendritic growth.

Answer 32

d. dendritic growth.

Question 33

33. Alloys that freeze or solidify at a single temperature that is lower than the individual components of the alloy are considered what type of alloy? a. Pure metal. b. Eutectic. c. Non-eutectic. d. Segregated.

Answer 33

b. Eutectic.

Question 34

34. For good castings, the metal must be at the correct ___________when it is poured into the mold. a. boiling point b. thermal coefficient c. superheat d. level

Answer 34

c. superheat

Question 35

35. The difference between porosity and gas holes in a casting is: a. location. b. size and number. c. inspector judgment. d. acceptability limits.

Answer 35

d. acceptability limits.

Question 36

36. Hot tears typically occur where in a casting? a. On thicker sections. b. On thinner sections. c. At changes in section thickness. d. At random locations on the casting.

Answer 36

c. At changes in section thickness.

Question 37

37. Discontinuities that occur where additional molten metal cannot be fed quickly enough to offset contraction during solidification are called: a. hot tears. b. air pockets. c. inclusions. d. shrinkage cavities.

Answer 37

d. shrinkage cavities.