Term
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Definition
| the modifications that are incorporated into a pattern |
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Term
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Definition
| )- if the riseris contained entirely within the mold it is known as a blind riser |
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Term
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Definition
| )- solid material is first melted, heated to proper temperature, and sometimes treated to modify its chemical composition. The molten material is then poured into a cavity or mold that contains it in the desired shape during subsequent cool-down and solidification. |
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Definition
| techniques generally work by either speeding solidification of the casting (chills) or retarding the solidification of the riser. Can effectively promote directional solidification or increase the effective feeding distance of a riser |
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Term
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Definition
| )- a narrow band of randomly oriented crystals that forms on the surface of a casting |
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Term
| • Chvorinov’s rule (p282)- |
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Definition
| amount of heat that must be removed form a casting to cause it to solidify is dependent upon both the amount of superheating and the volume of metal in the casting. Ability to remove heat from a casting is directly related to the amount of exposed surface area through which the heat can be extracted and the environment surrounding it. Chvorinovs rule states that tS , the total solidification time can be computed by t=B(V/A)N |
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Definition
| those crystals whose rapid-growth direction is perpendicular to the casting grow fast and shut off adjacent grains whose rapid growth direction is at some intersecting angle. The favorably oriented crystals continue to grow, producing long, thin columnar grains of a columnar zone. |
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Definition
| can provide one of the most useful tools for studying the solidification process. By inserting thermocouples into casting and monitoring the temperature vs time, one can obtain valuable insight into what is happening in the various regions |
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Term
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Definition
| name given to the top half of the pattern, flask, mold, or core |
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Term
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Definition
| sand (or metal) shape that is inserted Into a mold to produce the internal features of a casting, such as holes of passages for mater cooling |
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Term
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Definition
| the mold or die used to produce casting cores |
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Term
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Definition
| a region that is added to the pattern, core, or mold and is used to locate and support the core within the mold. |
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Term
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Definition
| (cold riser) fill with metal that has already flowed trhough a mold cavity |
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Term
| • Directional solidification (p280)- |
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Definition
| in which the solidification interface sweeps continuously through the material, can be used to assure the production of a sound casting. |
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Term
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Definition
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Term
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Definition
| the bottom half of any of a pattern, flask, mold, or core. (p.278) |
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Definition
| AKA slag- a material that can become trapped in the casting and impair surface finish, machinability, and mechanical properties. (p. 283) |
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Term
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Definition
| In many materials, new materials can nucleate in the interior of the casting and then grow to produce another region of spherical, random oriented crystals, known as the equiaxed zone. (p. 282) |
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Term
| • Expendable-Mold Process |
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Definition
| Those processes for which a new mold must be created for each casting (p. 288) |
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Term
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Definition
| Masses of high-heat-capacity, high-thermal-conductivity material that are placed in the mold, adjacent to the casting, to accelerate the cooling of various regions. (p. 288) |
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Term
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Definition
| rigid metal or wood frame that holds the molting aggregate (p. 278) |
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Term
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Definition
| - the ability of a metal to flow and fill a mold (p.284 |
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Term
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Definition
| - if an alloy is used that does not have a distinct melting point, the difference between the liquidus and solidus temperatures is known as the freezing range. (p. 281) |
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Term
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Definition
| - Passing small bubbles of inert or reactive gas through the melt. (p.284) |
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Term
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Definition
| - When liquid metals containing significant amounts of dissolved gas solidify, the solid structure cannot accommodate the gas, and the rejected atoms tend to form bubbles or gas porosity within the casting. (p.283) |
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Term
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Definition
| - Controlled entrances that metals travel through on way to mold cavity. (p. 279) |
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Term
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Definition
| • If the choke is moved to the gates, the metal might enter the mold cavity with a fountain effect, an extremely turbulent mode or flow, but small connecting area would make separation of the casting and gating system easier. (p. 285) |
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Term
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Definition
| the network of connected channels used to deliver the molten metal to the mold cavity (p. 279) |
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Term
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Definition
| the practice of intentionally introducing impurities is known as inoculation or grain refinement. (p. 280) |
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Term
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Definition
| - Excessive fillets can augment the second problem that arises when sections of castings intersect. (p. 292) |
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Term
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Definition
| Excessive fillets can augment the second problem that arises when sections of castings intersect. caused by intersecting sections When the differences in the sections cooling rates are large, the hot-spot areas are likely to obtain objectionable defects, such as porosity or shrinkage cavities. (292) |
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Term
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Definition
| the practice of intentionally introducing impurities is known as inoculation or grain refinement. (p. 280) |
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Term
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Definition
| Pieces of metal that are placed within the mold cavity to absorb heat and promote more rapid solidification. (p.288) |
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Term
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Definition
| the lowest temperature at which a material is all liquid. (281) |
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Term
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Definition
| - (a.k.a hot risers)- receive the last hot metal that enters the mold and generally do so at a time when the metal in the mold cavity has already begun to cool and solidify. (p.287) |
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Term
| (p 281) local solidification time |
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Definition
| the time from the start of solidification to the end of solidification |
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Term
| p290) machining allowance |
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Definition
- when machine surfaces must be provided on
castings it is often necessary to add a machining allowance or finish
allowance, to the pattern. The allowance depends to a great extent on
the casting process and the mold material |
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Term
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Definition
a defect that occurs is the metal begins to freeze
before it has completely filled the mold |
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Term
| p 278, 279, 285, 290) mold cavity |
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Definition
. is the shaped hole into which the
molten metal is poured and solidified to produce the desired casting,
made up of the combination of the mold material and the core. Having the
desired shape and size, must be produced with allowance for shrinkage of
the solidifying material. Any geometrical feature in the finished
casting must exist in the cavity. (can read more p278). |
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Term
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Definition
represented as B in the total solidification time
equation. It incorporates the characteristics of the metal being cast
(its density, heat capacity, and heat fusion), the mold material (its
density, thermal conductivity, and heat capacity), the mold thickness,
and the amount of superheat. *more the read if you want! |
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Term
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Definition
- whether sand, metal, or other
material--distinguishes various casing processes |
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Term
| (p278) multiple-use mold- |
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Definition
are generally made of metal or graphite. Since
they ten to be quite costly, their use is generally restricted to
products where large quantities are desired. |
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Term
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Definition
one of the stages of solidification. occurs when a
stable particle of solid forms from within the molten liquid. As the
material changes state, its internal energy is reduced since at lower
temperatures the solid phase is more stable than the liquid. Occurs on
some form of existing surface since solidification no longer requires
the creation of a full, surrounding interface. *It will produce a
crystal or grain in the final casting. |
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Term
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Definition
| - a riser that is open to the atmosphere |
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Term
| (p289) parting line or parting surface |
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Definition
the surface where one section of
the mold mates with the other section or sections. (p 279) the interface
that separates the cope and the drag halves of a mold, flask, or pattern
and also the halves of a core in some core-making processes |
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Term
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Definition
the casting process starts with the construction of a
pattern, and approximate duplicate of the final casting |
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Term
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Definition
the fluidity may be so great as to permit
penetration, a defect where the metal not only fills the mold cavity but
also fills the small voids between the particles of a sand mold. The
surface of the resultant casting would then contain small particles of
embedded sand. |
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Term
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Definition
- also called pouring basin, is the portion of the
gating system that initially receives the molten metal from the pouring
vessel and controls its delivery to the rest of the mold |
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Term
| (p280) pouring temperature- |
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Definition
the temperature of the liquid metal when it
first enters the mold cavity |
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Term
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Definition
- if undercooling was required to induce the initial
nucleation, the subsequent solidification may release enough heat to
cause an increase in temperature back to the melting point. This
increase in temperature is known as recalescence. |
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Term
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Definition
an extra void created in then mold that will also fill
with molten metal. It provides a reservoir of liquid that can flow into
the mold cavity to compensate for any shrinkage that occurs during
solidification. If the riser contains the last material to solidify,
shrinkage voids should be located in the riser and no the final casting.
*I think the info on p279 is the same as p286 but you can look if you
want! |
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Term
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Definition
- after the pouring cup, the metal travels down a sprue and
then along runners, which are horizontal channels |
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Term
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Definition
can be used to catch and traop this first metal
and keep it from entering the mold cavity. These are particularly
effective with aluminum castings since aluminum oxide has approximately
the same density as molten aluminum. |
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Term
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Definition
- shrinkage allowances are often incorporated into
a pattern through use of special shrink rules - measuring devices that
are larger than a standard rule by the appropriate shrink allowance. It
is different for different metals. A pattern made to the shrinkage rule
dimensions would then produce a proper-size casting after cooling. |
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Term
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Definition
once they are in the mold cavity and begin to cool,
most metals and alloys undergo a noticeable volumetric contraction.
There are 3 principal stages of shrinkage: (1) shrinkage of the liquid,(2) solidification shrinkage as the liquid turns into solid, and (3)
solid metal contraction as the solidified material cools to room
temperature. The amount of liquid metal contraction depends on the
coefficient of thermal contraction and the amount of superheat. |
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Term
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Definition
| )- located adjacent to the mold cavity, displaced horizontally along the parting line. |
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Term
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Definition
| -use mold (pg. 278)- the only thing it said in the book was that it is more economically than multiple-use molds and that they’re usually preferred for the production of smaller quantities…however, I think it’s pretty self-explanatory. |
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Term
| • Slag a.k.a. dross (pg.283)- |
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Definition
| when oxygen and molten metal react to produce metal oxides, which can then be carried with the molten metal during pouring and filling of the mold. This material can then become trapped in the casting and impair surface finish, machinability, and mechanical properties. |
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Term
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Definition
| - the only thing the book says about this is on pg. 288 is about an insulating sleeve, which is one way used to slow the cooling of risers; this technique generally seeks to reduce the rider size rather than promote directional solidification. |
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Term
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Definition
| )- the temperature below which a material is completely solid. |
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Term
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Definition
| vertical portion of the gating system |
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Term
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Definition
| can be used to dissipate the kinetic energy of the falling stream of metal. |
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Term
| • Stress Concentrators (from internet)- |
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Definition
| is a location in an object where stress is concentrated. An object is strongest when force is evenly distributed over its area, so a reduction in area, e.g. caused by a crack, results in a localized increase in stress. |
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Term
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Definition
| the difference between the pouring temperature and the freezing temperature of the material. The higher the superheat, the more time is given for the material to flow into the intricate details of the mold cavity before it begins to freeze. |
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Term
| • Thermal Arrest (pg.281)- |
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Definition
| the plateau in the cooling curve that occurs during the solidification of a material with fixed melting point. At this temperature, the heat being removed from the mold comes from the latent heat of fusion that is released during the solidification process. |
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Term
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Definition
| a riser that sits on top of a casting. Because of their location, top risers have shorter feeding distances and occupy less space within the flask, thereby providing more freedom for the layout of the pattern and gating system. |
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Term
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Definition
| only thing it says about it is that it is another way to slow the cooling of risers. |
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Term
| • Total Solidification Time (pg.281)- |
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Definition
| the time from the start of pouring to the end of solidification. |
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Term
| • Turbulent Flow (pg.285)- |
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Definition
| flow that tends to promote absorption of gases, oxidation of the metal, and the erosion of the mold (gating systems should be designed to minimize this.) |
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Term
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Definition
| amount of difference between the melting point and the actual temperature of nucleation. |
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Term
| • Vacuum Degassing (pg.284)- |
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Definition
| a method that attempts to remove the gas from the molten metal before it is poured into castings, in which the molten metal is sprayed through a low-pressure environment. Under these conditions, the amount of dissolved gas is reduced as the material seeks to establish an equilibrium with its new surroundings. |
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Term
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Definition
| additional chambers that may be included in a mold or core to provide an escape for the gases that are originally present in the mold or are generated during the pour. |
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Term
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Definition
| the casting weight divided by the total weight of the metal poured. |
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Term
| • Solidification shrinkage |
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Definition
| casting defect that can be reduced or eliminated by controlling the solidification process. |
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