Ch. 6 Sand Flashcards
What is permeability
the ability of how well gases can vent and pass through sand
What is purpose of Methylene Blue test
To test the amount of active clay in green sand
What is the problem with silica sand
it tends to contract heavily when exposed to high-temperature alloys
What is AFS GFN
Grain Fineness Number. Measure of grain size and sand distribution
What properties do sands with more round and spherical grains have
has harder time allowing air to escape
what is a fractured sand grain called?
fine
what are the advantages of chromite and zircon sand
very heavy sand, and good hardness
how is GFN related to grain size
indirectly proportional to grain size
what is a misrun
when the molten metal freezes before it reaches all parts of the mold cavity.
what is Clay used in green sand
a binder
2 main types of clay in green sand
Southern bentondite popular wiht aluminum. Western bentonite is popular with ferrous-based alloys.
what is a calcinator
soemthing that melts a compound
what is sand reclamation
when foundries remove part of their used sand and treats it to resotre the sand’s properties
what is water used in green sand
an activator
what are carbonaceous materials used for in green sand
to provide a good surface finish
what are 4 heat-activated procces
- shell 2. oil sand 3. cold box 4. silicon-based
what is compactibility
the ability of sand to be rammed under an applied load. measured in density.
what does active clay do
sand which retains it’s binding force absorbs the moisture of sand
what are additives in green sand
a 4th material used to enhance the specific properties of green sand
what are common additives in green sand
carbonaceous materials, cereal, iron oxide
what does carbonaceous materials due to the green sand
allows for a good surface finish
what is the difference between batch muller and continuous muller
batch muller: mixes a given amount of molding materials at a time and discharges it before a fresh one is fed. continuous muller mixes a continuous stream of sand as it passes through the mixing unit.
how is grain size related to permeability
directly proportional. this is because as the gaps between particles increase the ability of fluids and air to travel through it becomes easier.
permeability of sand formula
( volume of air x height of specimen) / ( area of specimen times pressure of air x time in minutes it takes for a sand specimen to cross the specimen)
round grains have blank permeability
low permeability
angular grains have blank permeability
high
