n metals as it cools prior to its solidification. (b) Contraction of the metal during phase change from liquid to solid. (c) Contraction of the solidified metals as its temperature drops to ambient temperature. (d) All of above.
Describe the stages involved in the contraction of metals during casting.
(a) Contraction of the molten metals as it cools prior to its solidification.
(b) Contraction of the metal during phase change from liquid to solid.
(c) Contraction of the solidified metals as its temperature drops to ambient temperature.
(d) All of above.
(e) None of above.
2. What kinds of defects in castings?
(a) Hot tear.
(b) Surface scar.
(c) Plastic deformation.
(d) Ductile flow.
3. How does porosity have detrimental effects on the
castings?
(a) Pores in castings are resulted from internal discontinuities when that are prone to
propagate under external stresses.
(b) The toughness of a material will decrease as a result of porosity.
(c) Physical properties, such as thermal and electrical conductivity, also be adversely
affected by porosity.
(d) Pores increase the strength and elastic modulus.
(e) Porosity increases both the thermal and electrical conductivity
4. Thermosetting plastics can be used in injection molding as long as:
(a) The molds must be heated to allow polymerization and cross linking to occur in the
mold cavity.
(b) The molds need to be cooled to allow polymerization and cross linking to occur in the
mold cavity.
(c) The longer cycle times to enable the process a high a production rate.
(d) Keeping the process the same as molding of thermoplastics.
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