Metal Terminology N

NATURAL AGING
Spontaneous aging of a supersaturated solid solution at room temperature.

NEEDLE CUTTER STEEL
Usually supplied quarter hard rolled, extra precision rolled with sheared edges. Carbon content 1.25% - Chromium .15%. Usually supplied in a 2” width from .002 to .035”. Used for cutting the eye of needle and milling the latch in a latch needle.

NETWORK STRUCTURE
A structure in which the crystals of one constituent are surrounded by envelopes of another constituent which gives a network.

NICKEL
(Chemical symbol Ni) - Element No. 28 of the periodic system; atomic weight 58.69. Silvery white, slightly magnetic metal, of medium hardness and high degree of ductility and malleability and resistance to chemical and atmospheric corrosion; melting point 265l癋.; boiling point about 5250癋., specific gravity 8.90. Used for electroplating. Used as an alloying agent, it is of great importance in iron-base alloys in stainless steels and in copper-base alloys such as Cupro-nickel, as well as in nickel-base alloys such as Monel Metal. Its principal functions as an alloy in steel making: (1) Strengthens unquenched or annealed steels. (2) Toughens pearlitic-ferritic steels (especially at low temperature). (3) Renders high-chromium iron alloys austenitic.

NICKEL SILVER
Copper base alloys that contain 10-45% Zn. and 5-30% Ni.

NICKEL STEEL
Steel containing nickel as an alloying element. Varying amounts are added to increase the strength in the normalized condition to enable hardening to be performed in oil or air instead of water.

NITRIDING
Process of surface hardening certain types of steel by heating in ammonia gas at about 935-1000癋. The increase in hardness being the result of surface nitride formation. Certain alloying constituents, principal among them being aluminum, greatly facilitate the hardening reaction. In general, the depth of the case is less than with carburizing.

NITRIDING STEEL
Steel which is particularly suited for the nitriding process, that is, it will form a very hard and adherent surface upon proper nitriding (heating in a partially dissociated atmosphere of ammonia gas). Composition usually .20-.40% carbon, .90-1.50% chromium, .15-1.00% molybdenum, and .85-1.20% aluminum.

NON-FERROUS METALS
Metals or alloys that are free of iron or comparatively so.

NON-METALLIC INCLUSIONS
Impurities (commonly oxides), sulphides, silicates or similar substances held in metals mechanically during solidification or formed by reactions in the solid state.

NON-REFRACTORY ALLOY
A term opposed to refractory alloy. A non-refractory alloy has malleability, that is, ease of flattening when subjected to rolling or hammering.

NON-SCALLOPING QUALITY STRIP STEEL
Strip steel ordered or sold on the basis of absence of unevenness, or ears, on the edges of the steel, when subjected to deep drawing.

NORMALIZING
A heat treatment applied to steel. Involves heating above the critical range followed by cooling in still air. Is performed to refine the crystal structure and eliminate internal stress.

NUMBER AS PERTAINING TO EDGE
(See Edge)

NUMBER AS PERTAINING TO HARDNESS
In copper base alloys industry; temper is referred to as so many numbers hard, i.e.; Yellow Brass Half Hard is termed 2 numbers hard. This term is derived from terminology used on the mill floor whereby temper or hardness is imparted by cold working and classified as to hardness by the number of Brown & Sharpe gages away from the soft or as-annealed state.

NUMBER AS PERTAINING TO TEMPER
(See Temper)

Metal Terminology O

OIL HARDENING
A process of hardening a ferrous alloy of suitable composition by heating within or above the transformation range and quenching in oil.

OIL-HARDENING STEEL
Steel adaptable to hardening by heat treatment and quenching in oil.

OIL STAIN ALUMINUM
Stain produced by the incomplete burning of the lubricants on the surface of the sheet. Rolling subsequent to staining will change color from darker browns to lighter browns down to white.

OLSEN (DUCTILITY) TEST
A method of measuring the ductility and drawing properties of strip or sheet metal which involves determination of the width and depth of impression. The test simulating a deep drawing operation is made by a standard steel ball under pressure, continuing until the cup formed from the metal sample fractures. Readings are in thousandths of an inch. This test is sometimes used to detect stretcher straining and indicates the surface finish after drawing, similar to the Erichsen ductility test.

OPEN-HEARTH PROCESS
Process of making steel by heating the metal in the hearth of a regenerative furnace. In the basic open-hearth steel process, the lining of the hearth is basic, usually magnesite; whereas in the acid open-hearth steel process, an acid material, silica, is used as the furnace lining and pig iron, extremely low in phosphorous (less than 0.04%), is the raw material charged in.

OPEN SURFACE
Rough surface on black plate, sheet or strip, resulting from imperfections in the original steel bars from which the plate was rolled.

ORANGE PEEL
(Effect) - A surface roughening (defect) encountered in forming products from metal stock that has a coarse grain size. It is due to uneven flow or to the appearance of the overly large grains usually the result of annealing at too high a temperature. Also referred to as “pebbles” and “alligator skin.”

ORE
A mineral from which metal is (or may be) extracted.

ORIENTATION
(Crystal) - Arrangement of certain crystal axes or crystal planes in a polycrystalline aggregate with respect to a given direction or plane. If there is any tendency for one arrangement to predominate, it is known as the preferred orientation. In the absence of any such preference, random orientation exists.

OSCILLATED WOUND OR SCROLL WOUND
A method of even winding metal strip or wire on to a reel or mandrel wherein the strands are uniformly overlapped. Sometimes termed “stagger wound” or “vibrated wound.” The opposite of ribbon wound.

OVERAGING
Aging under conditions of time and temperature greater than those required to obtain maximum strength.

OXIDATION
The addition of oxygen to a compound. Exposure to atmosphere sometimes results in oxidation of the exposed surface, hence a staining or discoloration. This effect is increased with temperature increase.

OXIDE
Compound of oxygen with another element.

OXYGEN LANCE
A length of pipe used to convey oxygen onto a bath of molten metal.