MME 231 Exam 1 Practice Questions – Study Guide, Revision Material, and Exam
Preparation
What are the effects of mold materials on fluid flow and heat transfer? - ✔✔-Rigid mold
materials may cause turbulence in flow which may slow the molten metal too much to the point
of solidification
-Mold materials must have a low coefficient of heat transfer
How can you tell whether cavities in a casting are due to porosity or to shrinkage? -
✔✔Shrinking is when the casting solidifies and the part shrinks or cracks. Porosity occurs when
the gas collects in the metal causing air bubbles.
Explain the difference between short and long freezing ranges. How are they determined? Why
are they important? - ✔✔Short range = 50 degrees or less
Long range= 50 degrees or more
It is known that pouring molten metal at a high rate into a mold has certain disadvantages. Are
there any disadvantages to pouring it very slowly? Explain. - ✔✔The part may solidify too
quickly
Why does porosity have detrimental effects on the mechanical properties of castings? Which
physical properties are also affected adversely by porosity? - ✔✔The microstructure is not as
uniform with pores, causing the tensile strength, ductility, and toughness to decrease.
A spoked hand wheel is to be cast in gray iron. In order to prevent hot tearing of the spokes,
would you insulate the spokes or chill them? Explain. - ✔✔Since hot tearing tendency is
reduced as the strength increases, it is advisable to chill the spokes as this increases the
strength
Preparation
What are the effects of mold materials on fluid flow and heat transfer? - ✔✔-Rigid mold
materials may cause turbulence in flow which may slow the molten metal too much to the point
of solidification
-Mold materials must have a low coefficient of heat transfer
How can you tell whether cavities in a casting are due to porosity or to shrinkage? -
✔✔Shrinking is when the casting solidifies and the part shrinks or cracks. Porosity occurs when
the gas collects in the metal causing air bubbles.
Explain the difference between short and long freezing ranges. How are they determined? Why
are they important? - ✔✔Short range = 50 degrees or less
Long range= 50 degrees or more
It is known that pouring molten metal at a high rate into a mold has certain disadvantages. Are
there any disadvantages to pouring it very slowly? Explain. - ✔✔The part may solidify too
quickly
Why does porosity have detrimental effects on the mechanical properties of castings? Which
physical properties are also affected adversely by porosity? - ✔✔The microstructure is not as
uniform with pores, causing the tensile strength, ductility, and toughness to decrease.
A spoked hand wheel is to be cast in gray iron. In order to prevent hot tearing of the spokes,
would you insulate the spokes or chill them? Explain. - ✔✔Since hot tearing tendency is
reduced as the strength increases, it is advisable to chill the spokes as this increases the
strength
