| Definitions of Terms Used in The Steel Industry |
ACID LINING - The inner bottom and lining of a metling furnace composed of materials having an acid reaction if in contact with a molten slag (sand, silicous rock, or silica bricks). ACID STEEL - Steel melted in a furnace having an acid bottom and lining and under a slag with acid reaction. The term has no reference to the acidity of the steel. AGING - The spontaneous change in the properties of a metal usually associated with the recovery of the metal from an unstable condition produced by quenching (quenchaging) or by cold working (strainaging). AIR HARDENING ( Air Quenching) - A hardening process wherein the steel is heated to the hardening temperature and cooled in the air. Unless steel is high in carbon or alloy, or both, it will not show much increase in hardness when air hardened. ALLOY - A material with metallic properties composed of two or more elements of which as least one is a metal. AMORPHOUS - Non-Crystalline. ANNEALING - Annealing generally regers to the heating and controlled cooling of solid material for the purpose of removing stresses. making it softer, refining its structure of changing its ductility, toughness or other properties. Specific heat treatments covered by the term annealing include black annealing, blue annealing, box annealing, bright annealing, full annealing, graphitizing, malleablizing and process annealing. AS ROLLED - When bars are hot rolled and allowed to cool in the air, they are to be in the "as rolled" or natural condition. AUSTEMPERING - A patented heat treatment process that consists of quenching an iron-base alloy from a temperature above the transformation range in a medium having a high rate of heat abstraction, and then maintaining the metal, until rate of heat abstraction, and then maintaining the metal, until transformation is complete, at a substantially uniformed temperature which is below that of peralite formation and above that of martensite formation. AUSTENITIC STEEL - Steel which has a stable austentic structure
at normal (room) temperatures. BARK - Decaburized skin found just beneath the scale. BASIC STEEL - Steel melted in a furnace with a basic bottom and lining and under a slag having a basic reaction. Most steel made in America is basic. BEND TEST - A test commonly made by bending a cold sample of specified size and through a specific circular angle. Bend tests provide an indication of the ductility of the sample. BESSEMER PROCESS - A steel-making process in which air is blown through the molten pig iron in removing impurities by oxidation. BILLET - A semi-finish rolled ingot of rectangular cross section or nearly so, In general the term "billet" is used when the cross section ranges from 4 up to 36 sq. in., the width always being less than twice the thickness. Small sizes are usually classed as bars or "small billets." The term "boolm" is property used when the cross section about 36 sq. in., though this distinction is observed. BILLET MILL - See "Blooming Mill" BLACK ANNEALING - A process of box annealing of sheets prior to tinning whereby a black oxide color is imparted to the surface of the product. BLAST FURNACE - A shaft supplied with air blast, usually hot, for producing pig iron by smelting iron ore. The furnace is continuous in operation, the raw materials (iron ore, coke, and limestone) are charged at the top, and the molten pig iron and slag are collected at the bottom and are tapped out at intervals. BUSTER - A defect in metal produced by gas bubbles either on the surface or formed beneath the surface while the metal is hot or plastic. Very fine blisters are called pinhead or pepper blisters. BLOOM - See "billet" BLOOMING MILL - A mill used to reduce ingots to blooms, slabs, etc. BLOWHOLE - A hole produced during the solidification of metal by evolved gas which, in failing to escape, is held in the metal. BLUE ANNEALING - A process of annealing sheets after rolling. The sheets, if fairly heavy, are allowed to cool slowly after the hot rolling; if of lighter gauge, as is usually the case, they are passed singly through an open furnace for heating to the proper annealing temperature. As the name indicates, the sheets have a bluish-black appearance. BLUEING - A method of coating sheets with a thin, even film bluish black oxide. The blued surface is obtained by exposure to an atmosphere of dry steam or air at a temperature of about 100° F. Generally this is done during box annealing. BOX ANNEALING - Softening steel by heating, usually at a subcritical temperature, in a suitable closed metal box or pot to protect it from oxidation, employing a slow heating and cooling cycle; also called close to annealing or pot annealing. BRIGHT ANNEALING - An annealing process usually carried out in controlled furnace atmosphere so that surface oxidation is reduced to a minimum and the surface remains relatively bright. BRINELL HARDNESS TEST - The test consists of forcing a ball of standard diameter into a specimen being tested under standard pressure, and judging the hardness of the material by the amount of metal displaced. BURNING - Heating steel to a temperature sufficiently close to the
melting point to cause permanent injury. Such injury may be caused
by the melting of the more fusible constituents, by the penetration
of gases such as oxygen into the metal with consequent reactions,
or perhaps by the segregation of elements already present in the
metal. CARBON FREE - Metals and alloys which are practically free from carbon. CARBO-NITRIDING - A process of case hardening an iron-base alloy by the simultaneous absorption of carbon and nitrogen through heating in a gaseous atmosphere of suitable composition, followed by cooling at a rate that will produce desired properties. CARBON RANGE - In steel specifications, the carbon range is the difference between the minimum and maximum amount of carbon acceptable. CARBON STEEL - Steel whose major properties depend on its carbon content and in which other alloying elements are negligible. CARBURIZING - Adding carbon to iron-base alloys by absorption through heating the metal at a temperature below its melting point in contact with carbonaceous materials. Such treatment followed by appropriate quenching hardens the surface of the metal. The oldest method of case hardening. CARBURIZIND COMPOUND - Mixtures containing carbonaceous solids which will give up carbon to steel in the presence of heat. Gas rich in carbon is sometimes used in the carburizing process. CASE - The surface layer of an iron-base alloy which has been made substantially harder than the interior by the process of case hardening. CASE HARDENING - Carburizing, nitriding. or cyaniding and subsequent hardening, by heat treatment, all or part of the surface portions of a piece of iron base alloy. CASE STEEL - Any object made by pouring molten steel into molds. CHARPY TEST - A test made to determine the notched toughness, or impact strength, of a material. The test gives the energy required to break a standard notched specimen supported at the two ends. CHEMICAL ANALYSIS - Qualitative analysis consists of separating a substance into its component elements and identifying them. In quantitative analysis the proportion of all component elements are determined. CHILL CAST PIG - Pig iron case into metal molds of chills. If a machine is used the product is known as machine cast pig. CHIPPING - One method of removing surface defects such as small fissures or seams from partially worked metal, If not eliminated, the defects might carry through to the finished material. If the defects are removed by means of a gas-torch the term "deseaming" or "scarfing" is used. CHROMIUM - A hard, grayish white and corrosions resistant metal widely used as an alloying element is steel and for plating steel products. COLD DRAWING - See " Cold Finishing" COLD FINISHING - Changing the shape of, or reducing the cross section of steel while cold-usually accomplished by rolling, drawing through a die or turning. COLD ROLLING - See "Cold Finishing." COLD SHUT - An area in metal where two portions of the metal in either a motlen or plastic condition have come together but have failed to unite into a integral mass. COLD WORKING - Permanent deformation of a metal below its recrystallization temperature, which hardens the metal. COMBINED CARBON - All of the carbon in iron or steel which is combined with iron or other elements to form carbide. CORE - The center portion of a piece of steel which may be of different chemical composition that the outside, as in the case of carburized parts, or which may have different physical properties than the outside due to the failure of penetration of heat treatment effect. CREEP STRENGTH - The maximum stress which can be applied to steel at a specific temperature without causing more than a specified percentage increase in length in a specified time. CRITICAL POINTS - The various temperatures at which transformations occur in steel as it passes through its critical range - on either a rising or falling temperature . (See Transformation Page) CRITICAL RANGE - A temperature range in passing through which steel undergoes transformation. The preferred term is transformation range (q.v.). CRITICAL TEMPERATURES - See "Critical Points." CROP - The imperfect ends of a rolled or forged Product which are removed and discarded. CUP FRACTURE - A type of fracture - which looks like a cup having the exterior portion extended with the interior slightly depressed - produced in a tensile test specimen. Usually an indication of ductility. CYANIDING - Surface hardening of an iron-base alloy article or portion of it by heating at suitable temperatures in contact with molten cyanide salt and then quenching. DECARBURIZATION - The loss of carbon from the surface of solid steel
during heating, forging, hot rolling, etc. DENDRITE - A crystal formed during solidification having many branches and a tree-like pattern; also termed "pine tree" and "fir tree" crystals. DEOXIDISED SHEETS - Hot rolled sheets that have been bright annealed. DEOXIDIZER - A substance added to molten steel for the purpose of removing oxygen. DEPTH OF PENETRATION - The depth to which appreciable hardening occurs when steel is quenched from its hardening temperature. DIFFERENTIAL HEATING - Heating so that various portions of an article reach different temperatures to produce different properties upon cooling. DISCARD - See "Crop." DISTORTION - A change in shape (usually refers to changes of shape caused by internal stress.) DRAWING - Drawing may refer to the pulling of the steel through a die, as in drawing wire, or deforming steel in dies on a press (deep drawing). DRAWING BACK - Reheating after hardening to a temperature below the critical for the purpose of improving the ductility and/or lowering the hardness or the steel. DUCTILITY - The ability to permit change of shape without fracture.
In steel, ductility is usually measured by elongation and reduction
of area as determined in the tensile test. ELONGATION - The increase in length of a test specimen after rupture in a tensile test, expressed as a percentage or the original length. ENDURANCE LIMIT - Maximum dynamic stress to which material may be submitted for an infinite number of times without causing fatigue failure. ERICHEN VALUES - These are widely used in conjunction with other measures as an indication of the deep drawing properties of steel sheets and strip. They are determined in a cupping test in which a conical punch with a round end is advanced into a test specimen help by a blank-holder on a die until the test specimen fractures. The depth of the cup is measured in millimeters on a scale and becomes the Erichsen value. EUTECTOID STEEL - Carbon steel with a 100 per cent pearlitic structure,
which is the structure developed under normal conditions of hot
working and cooling when the proportion of carbon is about .80
per cent. Hypereutectoid steel has a greater percentage of carbon,
and hypo-eutectoid steel has less carbon. FATIGUE LIMIT - See "Endurance Limit." FERRO ALLOYS - Iron alloyed with some element such as manganese, chrome, or silicon, etc., used in adding the element to molten sheet. FIBER STRESS - Unit stress at a certain point when overall section stress is not uniform. FIN - Protuberance resulting from the improper squeezing of steel during rolling. Also see "Flash." FINISHED STEEL - Steel which is ready for the market without any further work or treatment such as wire, bars, sheets, rails, plates, etc. Blooms, billets, slabs, and wire rods are termed semi-finish. FINISHING TEMPERATURE - Temperature at which hot mechanical working of metal is completed. FLAKES - An internal steel fracture with a bright, scaly appearance. FLAME ANNEALING - The direct application of a high temperature flame to a steel surface for the purpose of removing stresses and softening the metal. Commonly used to remove stresses from welds. FLAME HARDENING - In this method of hardening, the surface layer of a medium or high carbon steel is heated by a high temperature torch and then quenched. FLASH - A thin fin of meal formed at the sides of a die forging or sometimes a rolled bar where a small portion of the metal is forced out between the edges of the forging dies or rolls. FORGING - A piece of metal which has been saped or formed. while hot, by forging with a hammer (hand or power), in a press; or by a drop hammer. FORGING STRESSES - Stresses resulting from forging or from cooling from the forging temperature. FRACTURE - The surface of a break in metal. FREE MACHINE - A term used to describe a metal which may be machined at relatively high speed without the development of excessive heat and from which the chips will break off easily leaving a smooth surface. FULL ANNEALING - Heating to above the critical temperature range followed by slow cooling through the range, producing maximum softness. FULL HARDNESS - Usually the hardness of heat treated steel after
quenching and before tempering. GRAIN REFINEMENT - Reducing the crystalline of grain structure by heat treating, or by a combination of heat treating and mechanical working. GRAIN STRUCTURE - The type of crystalline structure as observed by eye or under the microscope. GRAPHITIZING - Annealing gray cast iron so that most of the carbon
is transformed to the graphitic condition. Controlled by increasing
silicon and by thermal treatment. HARDENABILITY - (Of Steel) The ability of a steel to harden with cooled form its hardening temperature as measured by its surface hardness and by the depth of hardening below the surface. HARDENING - (As applied to heat treatment of steel). Heating and quenching to produce increased hardness. HEAT OF STEEL - The steel produced from one charge in the furnace, and consequently practically identical in its characteristics. HEAT RESISTING STEELS - Those steels which are used for service at relatively high temperatures because they retain much of their strength and resist oxidation under such conditions. HEAT TREATMENT - An operation or combination of operations involving the heating and cooling of steels in the solid state for the purpose of obtaining certain desirable mechanical, micro structural or corrosion-resisting properties. HIGH DRAW - A drawing temperature not very much below the Ac1 point of the steel-used to develop high ductility when tempering steel after the quench. HOT SHORTNESS - Brittleness in metal - at an elevated temperature. HOT TOP - See "Sinkhead." HOT WORKING - The mechanical working of metal above the recrystalization
temperature. INCLUSIONS - Particles of non-metallic material usually oxides, suphides, silicates and such which are entrapped mechanically or are formed during solidification or by subsequent reaction within the solid metal. INGOT - A casting intended for subsequent rolling or forging. Usually cast in metallic molds. INGOT IRON - Open hearth iron low in carbon, manganese and other impurities. IZOD TEST - A test made to determine the notched toughness of a
material. The test gives the energy required to break a standard
notched specimen supported as a cantilever beam. MACHINE STRAIGHTENING - Straightening metal bars by rolling in a straightening machine. MALLEABILIZING - An annealing operation performed on white cast iron for the purpose of partially or wholly transforming the combined carbon to temper carbon, and in some cases to remove completely the carbon from the iron by decarburization. MATRIX - The ground mass or principal substance in which a constituent is embedded. MECHANICAL WORKING - Working metal through rolls, presses, hammers, etc., to change its shape, properties or structures. MICROSCOPE - Extremely small - not large enough to be seen with the naked eye. MICROSTRUCTURE - The structure of metals as revealed by examination of polished and etched samples with the microscope. MODULUS OF ELASTICITY - The ratio within the limit of elasticity,
or the stress to the corresponding strain. The stres in pounds per
square inch is divided by the elongation in inches for each inch
of the original gauge length of the specimen. NICKEL STEEL - Alloy steel containing nickel as its principal alloying element. NITRIDING - Adding nitrogen to the solid iron-base alloys by heating at a temperature below the critical in contact with ammonia or other nitrogenous material. NORMALIZING - Heating to about 100° F. above the critical
temperature and cooling to room temperature in still air. Provision
is often made in normalizing for controlled cooling at a slower
rate, but when the cooling is prolonged the term used is annealing. OLSEN TEST - This is a cupping test made on an Olsen machine as an aid in determining ductility and deep drawing properties. OVERHEATING - Heating to such a temperature that, while the properties
of the metal are impaired, it has not been burned and can therefore
be restored by heat treatment. PEARLITE - A relatively hard constituent of steel made up of alternate layers of ferrite (iron). and cementite (iron carbide that is, a compound of iron and carbon). See "Eutectoid Steel." PERMANENT MOLD - A metal mold which is used repeatedly for the production of many castings of the same form. PICKLING - Immersion of steel in a dilute solution of acid for the purpose of removing the scale. PIERCING - Process of spinning and rolling a billet over a mandrel in such a way that a hole is opened in the center. PIG IRON - So called whether cast in metal molds to form pigs or keep molten awaiting transfer to the steel making furnaces. The term "hot metal," is also applied to molten pig iron. PIPE - A cavity formed in metal (especially ingots) during the solidification of the last portion of liquid metal. Contraction of the metal causes this cavity or pipe. PIT - A depression in the surface of metal occurring during its manufacture. POT ANNEALING - See " Box Annealing." PRECIPITATION HARDENING - The process of hardening an alloy by heating if for the purpose of allowing a structural constituent to precipitate from a solid solution. PROCESS ANNEALING - Heating to a temperature below or close to the
lower limit of the critical temperature range and then cooling as
desired. QUENCHING MEDIUM - The medium used for cooling steel during heat treatment - usually oil, water, air, or salts. QUENCHING TEMPERATURE - The temperature from which steel is quenched
during a heat treating process. RED SHORTNESS - See "Hot Shortness." REDUCTION OF AREA - The difference between the original cross-section area of a tensile specimen and that of the smallest area at the point of rupture. It is usually stated as a percentage of the original area; also called "contraction of are." REFINEMENT OF STRUCTURE - See "Grain Refinement." REFINING TEMPERATURE - A temperature employed in heat treatment to refine structure, in particular, to refine the grain size. Usually just above AC3 in steel. RIMMED STEEL - A steel that is poured containing enough oxygen to evolve appreciable gas during solidification. The gas evolution results in a finished product having a very pure surface with the impurities concentrated in the interior. The pure zone which is readily shown by etching is referred to as the "rim." ROCKWELL HARDNESS TEST - Forcing a cone - shaped diamond or hardened
steel ball into the specimen being tested under standard pressure.
The depth of penetration is an indication of the Rockwell Hardness. SLEROSCOPE or SHORE HARDNESS TEST - This test consist of dropping a small diamond tipped hammer from a standard height onto the surface of the specimen being tested. The height to which the hammer rebounds is a measure of the surface hardness of the specimen. SEAM - An elongated discontinuity in metal caused by a blowhole or other defect which has been closed by rolling or forging mechanically but not welded. SECONDARY HARDENING - An increase in hardness following the normal softening during the tempering of certain alloy steels. SEMI-FINISHED - See "Finished Steel." SKELP - Steel or iron plate from which pipe or tubing is made. SLAB - Steel or Iron plate from which pipe or tubing is made. SLABBING MILL - A mill for rolling slabs from ingots. SLIP PLANE - See "Slip Bands." SOAKING - Holding steel at a a predetermined temperature for a sufficient time to assure heat penetration and/or to complete the solution of carbides. SOLIDIFICATION RANGE - The temperature range through which metal freezes or solidifies. SOLID SOLUTION - A condition wherein one element is dissolved in another element while the dissolving element is in a solid and not liquid condition. SPHEROIDIZING - Any of a number of processes of heating and cooling which cause the carbides to assume a spherical-like shape. Ordinary steel are commonly spherodized by prolonged heating at temperature just below the lower limit of the transformation range with subsequent slow cooling. STRESS - The load per unit area tending to deform a material. STRETCHER LEVELING - A method of producing unusual flatness in steel
sheets bu stretching them in a hydraulic device. TEEMING - Pouring steel from the ladle to the molds. TEMPERING - Reheating after hardening to a temperature below critical and then cooling. TENSILE STRENGTH - The maximum load per unit of original cross-sectional
area obtained before rupture of a tensile specimen. WORK HARDNESS - Hardness resulting from mechanical working. |
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Stainless I Aluminum I Pipe & Tubing I Specialties I Data
