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.