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MALLEABLE IRON. (See IRON, MALLEABLE.)
MASTER PATTERN. A pattern embodying a contraction allowance in its construction, used for making castings to be employed as patterns in production work.
METALLOID. An element intermediate between metals and nonmetals possessing both metallic and non-metallic properties, as arsenic.
METALLOSTATIC PRESSURE. The pressure developed within a molten metal while it is still liquid. The metal head can exert considerable lifting force on a cope particularly if the cope is deep and the metal is poured rapidly.
MELTING LOSS. Loss of metal in charge during the
operation of melting, usually due to oxidation or volatilization.
MELTING POINT. The temperature at which a metal begins to liquify. Pure metals, eutectics and some intermediate phases, melt at a constant temperature. Alloys generally melt over a range of temperature.
MELTING RATIO. The proportion of the weight of metal to the weight of fuel used in melting.
METAL PENETRATION. A casting surface defect which appears as if the metal had filled the voids between the sand grains without displacing them.
MICROHARDNESS. The hardness of microconstituents of a material as determined by using a diamond indenter and a special machine equipped with a microscope.
MICROSTRUCTURE. The structure of polished and etched specimens of casting sections as revealed by a microscope at more than 90 diameters.
MISRUN. Casting not fully formed resulting from metal poured so cold that it is solidified before filling the mold completely.
MODIFICATION. A process in which the eutectic temperature, structure and composition of aluminum-silicon alloys are apparently altered by the addition of small amounts of a third element, such as sodium. A similar effect can be achieved by chill casting.
MOISTURE CONTENT. Amount of water contained in a substance that can be driven off by heating at 104°-110°C (220°-230°F).
MOISTURE TELLER. A patented apparatus for the rapid determination of the moisture content of molding sands using the reaction between calcium carbide and water to produce a gas pressure which is then measured.
MOLD. The form, made of sand, metal or any other investment material, which contains the cavity into which molten metal is poured to produce a casting of definite shape and outline.
MOLD COATING. Coating on sand molds to prevent metal penetration and to improve casting finish.
MOLD CAVITY. In a mold, the hole which, when filled with metal becomes the casting. Gates and risers are not considered part of the mold cavity.
MOLDABILITY. Ability of sand to flow into a flask and around a pattern, measured by the amount of sand falling through an inclined screen or slot.
MOLDING, MACHINE. May refer to squeezer or jolt-squeezer machines on which one operator makes the entire mold, or to similar or larger machines including jolt-squeeze-strippers, and jolt and jolt-rollover pattern draw machines on which the cope and drag halves of molds are made.
MOLDING SANDS. Sands containing over 5 per cent natural clay, usually between 8 and 20 per cent.
MOTTLED CAST IRON. Cast iron which consists of a mixture of variable proportions of gray cast iron and white cast iron; such material has a mottled fracture.
MULLER. A type of foundry sand mixing machine.
MULLING. Process of mixing sand and clay particles either by compressing with a heavy roller in preparation for molding or by forcing the sand mixture to flow between wheels mounted on a vertical axis and the side walls of the container. Also, the process of mixing sands with a rubbing action as well as stirring.
MULTIPLE-CAVITY DIE. A die having more than one duplicate impression.
MULTIPLE MOLD. A composite mold made up of stacked sections, each of which produces a complete gate of castings and poured from a central down-gate.
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