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.