-N-

National Bureau of Standards Gaithesburg, MD 20760.

National Foundry Association P. 0. Box 76, Westchester, IL 60153, Charles T. Sheehan, Executive Secretary.

National Industrial Sand Association . . . 900 Spring St., Silver Spring, Md. 20910. Kenneth E. Tobin, Jr., Managing Director.

National Machine Tool Builders Association . . . 2139 Wisconsin Ave., Washington, D.C., 20007, James J. Houston, Assistant Treasurer.

National Safety Council . . . 425 N. Michigan Ave., Chicago, IL 60611, Paul E. Sheppard, Director, Associations Divisions.

Natural Aging ... See Aging.

Natural Sand S... and derived from a rock in which the grains separate along their natural boundaries. This includes unconsolidated sand, or a soft sandstone where little pressure is required to separate the individual grains.

Naturally Bonded Molding Sand . . . A sand containing sufficient bonding material as mined to be suitable for molding purposes.

Navy (USA) Tear Test . . . A method of evaluating the susceptibility of ship plate to brittle or cleavage type fracture.

NBS ... See National Bureau of Standards.

Neat Brick . . . Brick with faces arranged so one of the flat faces is inclined toward the other, almost eliminating one end face.

Neat Cement ... Portland cement mixed with water only.

Neck Down (Knock-Off, Wafer Core, Washburn, Cameron Core) . . . A thin core or tile used to restrict the riser neck, making it easier to break or cut off the riser from the casting. See Core.

Necking . . . Reducing the cross sectional area of metal in an area by stretching.

Necking Down ... Reduction in area concentrated at the subsequent location of fracture when a ductile metal is stressed beyond its yield point in tension.

Needles . . . Elongated acicular crystals, tapering at each end to a fine point, as martensite.

Needling Agents ... Special agents such as boron which markedly increase the hardenability of steel.

Negative Quenching (Negative Hardening) . . . Accelerated cooling in water or oil, from a temperature below the critical range.

Negative Thermodie Heat Exchange . . . In shell molding, improving the mass-surface ratio by simulating profile geometry of pattern or core cavity on the underside; will boost running temperature of high projections by 25 percent.

Nesh (Hot Short) A British term applied to metal that is weak and ruptures easily under hot working conditions.

Network Structure ... A structure in which the grains or crystals of one constituent are partly or entirely enveloped in another constituent; an etched section through the crystals resembles a network.

Neumann Band . . . A mechanical twin in ferrite.

Neutral Refractories . . . A loose term designating refractories which presumably will not react with so-called acid or basic refractories and slags.

Neutron . . . Elementary nuclear particle with a mass (1.00893 mass units) approximately the same as that of a hydrogen atom. It is electrically neutral.

New Jersey Sand . . . A large number of grades of foundry sands mined in southern New Jersey.

NFFS . . . See Non-Ferrous Founders' Society.

Nichrome . . . Oxidation-resistant alloy 65% Ni, 20% Fe and 15% Cr.

Nickel . . . Element used for alloying iron and steel as well as nonferrous metals; melting point 1455 C (2651 F). Nickel is also a base metal for many casting alloys resistant to corrosion and high temperature oxidation. See Monel, Nimonic, Inconel, Ni-Hard.

Ni-Hard...... Hard white cast iron containing 4% Ni and 2% Cr.

Nimonic...... Class of nickel-base cast alloys resistant to stress and to oxidation at high temperatures. See Inconel.

Nine-inch Equivalent . . . Standard unit of volume in refractories industries; 9 x 41/2 x 21/2-in. brick.

Nipple . . . A pipe coupling consisting of a short piece of threaded tubing.

Nital ... A solution of nitric acid in alcohol used as a etching agent in ferrous metallography.

Nitrogen Flush ... Bubbling nitrogen gas through a met al melt under vacuum (as with valve bronze) to improve tensile properties and pressure tightness.

Nobake Binder ... A synthetic liquid resin sand binder that hardens completely at room temperature, generally not requiring baking, used in Cold-Setting process.

Noble Metals . . . Metallic elements with surfaces that do not readily oxidize in air; e.g., gold, silver, platinum

Nodular Fireclay (Burley, Burley Flint) . . . Rock containing aluminous or ferrogenous nodules, or both, bonded by fireclay.

Nodular Graphite ... Graphite or carbon in nodular form, characteristically in malleable and nodular iron.

Nodular Iron . . . Iron of a normally gray cast iron type that has been suitably treated with a nodularizing agent so that all or the major portion of its graphitic carbon has a nodular or sc)herulitic form as cast. Often referred to as ductile iron.

Noise Radiator A device creating noise.

Noise Sprectrum The various frequencies making a noise.

Nonogram (Graph) A graph that enables one by the aid of a straight-edge to read off the value of a dependent variable when the value of two or more independent variables are given.

Nondestructive Testing (inspection) . . . Testing or inspection that does not destroy the object being tested or inspected.

Nonferrous , . . A negative term, refers to alloy in which the predominant metal or solvent is not iron.

Non-Ferrous Founders' Society . . . 21010 Center Ridge Road, Cleveland, Ohio 44116, Benjamin J. Imburgia, Executive Secretary.

Normal Segregation . . . Concentration of alloying constituents that have low melting points in those portions of a casting that solidify last. Compare with Inverse Segregation.

Normal Steel Steel in which the pearlite is completely laminated.

Normalizing See Air Quenching.

Notch Bar Small size ingot with notches to facilitate breakage for remelting.

Notched Bar . . . A test specimen which is notched. Used in impact or fatigue tests.

Novalak . . . A two-step basic flake resin with no thermosetting properties, applied to sand in shelf molding process as a solid or solution.

Nowel . . . A colloquial term for the drag portion of mold; the term drag is preferred. See Drag.

Nozzle . . . Pouring spout of the bottom-pour ladle.

Nozzle Brick ... A thick-walled tubular refractory shape set in bottom of a ladle through which steel is teemed.

Nozzle Pocket Brick ... A refractory shaped set in bottom of a ladle containing a recess in which nozzle is set

NTP . . . Normal temperature and pressure reference point; zero centigrade 760 mm mercury pressure.

Nucleation . . . 1) (Self-Nucleation, Homogeneous) the initiation of solid crystals from the liquid stage, or new phase within a solid without outside interference 2) (heterogeneous) foreign particles altering the liquid solid interface energy during phase changes.

Nucleus ... The first structurally determinate particle o a new phase or structure that may be about to form. Applicable in particular to solidification, recrystallization and transformations in the solid state.