for melting (with suitable additions of scrap, etc.) for the
production of ferrous castings. Pilot or sample casting A casting made from a pattern pro- duced in a production die to check the accuracy of dimen-
sions and quality of castings that will be made. Pinhole porosity Very small holes scattered throughout a casting, possibly caused by microshrinkage or gas evolution during solidification.
Plaster molding Molding method where gypsum or plaster is mixed with talc and water to form a slurry that is poured around a pattern. After the slurry hardens, the pattern is removed and the mold is baked at an elevated temperature to remove all moisture prior to use.
Pouring basin Te enlarged mouth of the sprue into which molten metal is poured.
Precision casting A casting of high dimensional accuracy produced via investment casting, plaster mold casting, di- ecasting, permanent mold casting or shell mold casting.
Semi-permanent mold A permanent mold in which sand, plastic or graphite cores are used.
Shakeout Te process of separating the solidified casting
from the mold material (Fig. 7). Short run a) Insufficient metal in a ladle to fill the mold. b) When metal freezes at the gates before filling the mold.
Porosity Holes in the casting due to gases trapped in the mold, the reaction of molten metal with moisture in the molding sand or the imperfect fusion of chaplets with molten metal.
Shrinkage Contraction of metal in the mold during solidifi- cation. Te term also is used to describe the casting defect, such as shrinkage cavity, which results from poor design, insufficient metal feed or inadequate feeding.
as a result of the primary crystallization of one phase with the subsequent concentration of other elements in the remaining liquid.
Slag A fused nonmetallic material that protects molten metal
Pressure casting Making castings with pressure applied to the molten charge material, as in diecasting, centrifugal casting
and injection molding, as opposed to gravity pouring. Quenching Rapid cooling from an elevated temperature for hardening, normally achieved by immersion of the object in water, oil, or salt or organic compound solutions.
Recovery rate Ratio of the number of saleable parts to the to- tal number of parts manufactured, expressed as a percentage.
Refractory Heat-resistant ceramic material.
Reject rate Ratio of the number of parts scrapped to the total number of parts manufactured, expressed as a percentage.
Rheocasting Metalcasting process where liquid metal is agitated dur- ing initial stages of solidification to produce a semi-solid structure that remains highly fluid after 60% solidification.
from the air and extracts certain impurities from the melt. Slag inclusions Casting surface imperfections similar to sand inclusions but containing impurities from the charge materials, silica and clay eroded from the refractory lining, and ash from the fuel during the melting process. May also originate from metal-refractory reactions occurring in the ladle during the pouring of the casting.
a liquid (Fig. 8). Sodium silicate/CO2
Slurry A flowable mixture of refractory particles suspended in process Molding sand is mixed with
Sprue (downsprue-downgate) Te channel, usually verti- cal, through which molten metal enters the mold.
sodium silicate and the mold is gassed with CO2 to produce a hard mold or core.
Riser See feeder. Runner system or gating The set
of channels in a mold through which molten metal is poured to fill the mold cavity. The system normally consists of a vertical section (downgate or sprue) to the point where it joins the mold cav- ity (gate) and leads from the mold cavity through vertical channels
(risers or feeders). Sand inclusions Cavities or surface imperfections on a casting caused by sand washing into the mold.
Scrap a) Any scrap metal melted (usually with suitable additions of pig iron or ingots) to produce castings. b) Reject castings.
Segregation A casting defect in which alloying elements are con- centrated in specific regions, usually
2012 Casting sourCe DireCtory Metal Casting Design & PurChasing 49
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