Nobake process Molds/cores produced with a resin-bonded, air-setting sand. Also known as the airset process because
molds are left to harden under atmospheric conditions. Nodular iron See ductile iron. Normalizing A heat treatment in which ferrous alloys are heated
Offal Material that is trimmed off of a die-casting to separate it from the shot and/or clean the parting line.
to a suitable temperature above the transformation range and then cooled in still air to room temperature.
Orientation Te position of a part or tool in a production operation.
Overaging The process of aging a nonferrous, precipita- tion-hardening alloy under conditions of time and tem- perature greater than those required to obtain maximum strength and hardness.
Oxidation a) A reaction of an element with oxygen. b) Any process which increases the proportion of oxygen or acid- forming element or radical in a compound.
Parting line Te line showing the separation of the two halves of the mold.
Pattern Te wood, metal, foam or plastic shape used to form the cavity in the sand. A pattern may consist of one or many impressions and would normally be mounted on a board or plate complete with a runner system.
Pattern draft See draft. Pattern injection In investment casting, the process of
Pattern layout Full-sized drawing of a pattern showing its arrangement and structural features.
filling the pattern die with expendable material, usually in the liquid or plastic state.
Patternmaker’s shrinkage Te shrinkage allowance made on all patterns to compensate for the change in dimen- sions as the solidified casting cools in the mold from freezing temperature of the metal to room temperature. Te pattern is made larger by the amount of shrinkage characteristic of the particular metal in the casting and the amount of resulting contraction to be encountered.
Physical properties Properties of matter such as density, electrical and thermal conductivity, expansion and specific heat. Tis term should not be used interchangeably with “mechanical properties.”
Permeability Te property of a mold material to allow pas- sage of mold/core gases during the pouring of molten metal.
Fig. 8. In investment casting, wax patterns are dipped into a mix- ture of refractory materials, called a slurry, which is then fired and dried before molten metal is poured into 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.
Pouring basin Te enlarged mouth of the sprue into which molten metal is poured.
Pearlitic Pearlitic ductile iron is higher in alloy content than ferritic ductile iron. A pearlitic matrix lends higher strength.
Pig iron Blocks of iron to a known metal-chemical analysis that are used 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.
2013 Casting sourCe DireCtory Metal Casting Design & PurChasing 49
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