Structural and Plate Steel Terms and Definitions

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This page gives terms and definitionsfor a variety of engineering and manufacturing steel related phrases

GE HARDENING: Precipitation hardening; a process of aging that increases hardness and strength and ordinarily decreases ductility. Age hardening usually follows rapid cooling from solution heat treatment temperatures or cold working.

AGING: A change in properties of an aluminum alloy that generally occurs slowly at atmospheric temperatures and more rapidly at higher temperatures.

ALLOY: The mixture of any element with a pure metal. However, there are several elements regularly occurring in plain carbon steel as manufactured, such as carbon, manganese, silicon, phosphorous, sulfur, oxygen, nitrogen and hydrogen. Plain carbon steel is therefore an alloy of iron and carbon and these other elements are incidental to its manufacture. Steel does not become alloy steel until these elements are increased beyond their regular composition for a specific purpose, or until other metals are added in significant amounts for a specific purpose.

ALLOY STEEL: Steel is considered to be alloy steel when the maximum of the range given for the content of alloying elements exceeds one or more of the following limits: Manganese 1.650/0, silicon,.60%, copper,.600/0, or in which a definite range or a definite minimum quantity of any of the following elements is specified or required within the limits of the recognized field of constructional alloy. Steels: Aluminum, chromium up to 3.9~, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium, or any other alloying element added to obtain a desired alloying effect.

ANNEALING: See heat treating definitions .

BASIC OXYGEN FURNACE: The process of manufacturing steel in this type of furnace is called the basic oxygen process and is the most efficient method of producing low and medium carbon and low and medium alloy steels. In this process high purity oxygen is blown onto the surface of a bath of molten iron contained in a basic lined and ladle shaped vessel. The melting cycle duration is extremely short with quality comparable to open hearth steel.

BASIC PROCESS: A steel making process either basic oxygen, open hearth or electric in which the furnace is lined with a basic refractory. A slag, rich in lime, being formed and phosphorous removed.

BILLET: A solid semi-finished round or square product that has been hot worked by forging, rolling or extrusion. An iron or steel billet has a minimum width or thickness of 11~! inches and the cross-sectional area varies from 21/4 to 36 square inches.

BLAST FURNACE: A vertical shaft type furnace used for reducing iron ore to pig iron when cast or hot metal for further melting. This product is used in an open hearth or basic oxygen furnaces for production of steel.

BLOOM: Generally a rolled product from an ingot generally greater than 36 square inches in area. This is generally considered the first operation in the production of bars or structural's.

CARBON STEEL: Steel is classified as carbon steel when no minimum content is specified or required for aluminum, boron, chromium, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, or zirconium, or any other element added to obtain a desired alloy effect; when the specified minimum for copper does not exceed .40% or when the maximum content specified for manganese does not exceed 1.650/0; silicon .600/0; copper .60%.

CARBURIZING: See heat treating definitions 

CHARPY TEST: A pendulum-type single-blow impact test in which the specimen, usually notched, is supported at both ends as a simple beam and broken by a falling pendulum of given weight. The energy absorbed, as determined by the subsequent rise of the pendulum, is a measure of impact strength or notch toughness and is a measurement in foot-pounds. The test specimen is 2 or 2.165 long, .394 square and has a key hole type notch in the center made by centering a No. 47 drill .160 from one side and sawing through the hole.

COLD DRAWING: This is a process for finishing a hot rolled rod or bar at room temperature by pulling it through the hole of a die of the same shape but smaller in size. The bars or rods are cleaned of scale by pickling or other methods prior to cold drawing and then coated with lime which aids as a lubricant in the drawing operation.

COLD FINISHING: The cold finishing of steel, generally used for bars and shafting, may be defined as the process of reducing their cross sectional area, without heating, by one of five methods:

1. Cold rolling 3. Cold drawing and grinding 5. Turning and grinding

2. Cold drawing 4. Turning and polishing

COLD ROLLING: The cold working of hot rolled material by passing it between power driven rolls. The process is generally used for flat bars of such a size that they cannot be pulled through a die and for the production of cold rolled sheets by cold reducing hot rolled and pickled sheets. Whereas wire and sheets are cold drawn and cold rolled continuously from coil, bars are individually cold drawn.

COLD WORKING: Plastic deformation of a metal at a temperature low enough to insure strain hardening.

CORE: The center portion of a piece of steel which may be of different chemical composition than the outside, as in the case of carburized parts or which may have different mechanical properties than the outside due to the failure of penetration of heat treatment effect.

DECARBURIZATION: The loss of carbon from the surface of a ferrous alloy. Decarburization is a common surface condition of hot rolled steel and is produced during the heating and rolling operations when atmospheric oxygen reacts with the heated surface removing carbon.

ELASTIC LIMIT: The greatest stress which a material is capable of developing without a permanent deformation remaining upon complete release of the stress.

ELECTRIC FURNACE STEEL: Steel made in any furnace where heat is generated almost always by are. Because of relatively high cost, normally only tool steels and other high value steels are made by the electric furnace process.

ELONGATION: The amount of permanent extension in the vicinity of the fracture in the tensile or tension test; usually expressed as a percentage of the original gauge length, such as 25% in 2 or 21% in 8.

ENDURANCE LIMIT: Also known as fatigue limits a limiting stress, below which metal will withstand without fracture an indefinitely large number of cycles of stress. If the term is used without qualification, the cycles of stress are usually such as to produce complete reversal of flexural stress. Above this limit failure occurs by the generation and growth of cracks until fracture results in the remaining section.

FATIGUE: The phenomenon of the progressive fracture of a metal by means of a crack which spreads under repeated cycles of stress.

FERROUS: Metals or alloys that contain appreciable amounts of iron.

FILE HARDNESS: Hardness as determined by the use of a file of standardized hardness on the assumption that a material which cannot be cut with the file is as hard as, or harder than, the file. Files covering a range of hardnesses may be employed.

FRACTU RE TESTING: Breaking a specimen and examining the fractured surface with the unaided eye or with a low-power microscope to determine such things as composition, grain size, case depth, soundness, or presence of defects.

HARDEN-ABILITY: This relates to the ability of steel to harden deeply upon quenching and takes into consideration the size of the part, the method of quenching and the analysis and grain size of the steel. Carbon steels are considered as shallow hardening and various alloy and tool steel grades are considered deep hardening or through hardening.

HARDENING: Increasing the hardness by suitable heat treatment, usually involving heating and cooling. When applicable, the following more specific terms should be

used: age hardening, case hardening, flame hardening, induction hardening, precipitation hardening, and quench hardening.

HARDNESS: The ability of a metal to resist penetration. The principal methods of hardness determination are the Brinell, Rockwell and Scleroscope tests.

HEAT TREATMENT: An operation or combination of operations involving the heating and cooling of a metal in the solid state for the purpose of obtaining certain desirable conditions or properties. Heat treating operations would be annealing, normalizing, quenching and tempering, etc.

IMPACT TEST: A test used to determine the impact energy measured in foot pounds, to fracture a material by means of an Izod or Charpy test.

INCLUSIONS: Nonmetallic materials occurring in metals. More specifically in steel; oxides, sulphides, and silicates which are mechanically held during solidification of the ingot.

INGOT: A steel casting that is cast into a mold which when solidified will be rolled in a blooming mill to plates, slabs for sheets, or blooms and billets into structurals and bars.

IZOD TEST: An impact test similar to the charpy with the difference being in the test specimen. In the Izod test the specimen is 2.953 long,.3937 square with a 45 notch located 1.1024 from the impact end. The distance from the bottom of the notch to the opposite side is .315.

JOMINY TEST: This is a test used to determine the hardenability of any grade of steel. It consists of water quenching, under closely controlled conditions, one end of a one inch diameter specimen of the steel under test and measuring the degree of hardness at regular distances from the quenched end along the side. The hardnesses obtained at regular intervals along the bar are then either tabulated or plotted on graphs.

KILLED STEEL: Steel deoxidized with a strong deoxidizing agent such as silicon or aluminum in order to reduce the oxygen content to such a level that no reaction occurs between carbon and oxygen during solidification of the molten steel in the ingot. Killed steel products will produce a more chemically uniform analysis from the bottom to the top of the ingot. Killed steel is considered having less chemical segregation than semi-killed or rimmed steel.

MACHINABILITY: The relative ease of machining a metal. Machinability index for various steels and machinability tables are available for comparing machining rates with 1212 steel as the standard for carbon and alloy steels and W-l as a standard for tool steels.

MARTENSITE: A microconstituent or structure in quenched steel which has the maximum hardness of any of the structures resulting from the decomposition or transformation of austenite. Steel which is to be quenched and tempered properly must first be fully hardened in the martinsitic state and then drawn or tempered back.

MECHANICAL PROPERTIES: The properties of a material that reveal its elastic and inelastic behavior where force is applied, thereby indicating its suitability for mechanical applications; for example, modulus of elasticity, tensile strength, elongation, hardness and fatigue limit.

MILL EDGE: The edge of strip, sheet or plate in the as rolled state. Unsheared.

MODULUS OF ELASTICITY: The ratio within the limit of elasticity of the stress to corresponding strain. The stress in pounds per square inch is divided by the elongation in fractions of an inch for each inch of the original gauge length of the specimen. The modulus of elasticity for cold rolled steel is 29,500,000 psi and for other steels varies between 28,600,000 and 30,300,000 psi.

NITRIDING: Adding nitrogen to iron-base alloys by heating the metal in contact with ammonia gas, or other suitable nitrogenous material. Nitriding is conducted at a temperature usually in the range of 935-1000 F. and produces surface hardening of the metal without quenching.

NON-FERROUS: Metals or alloys that contain no appreciable quantity of iron. This term is applied to such metals as aluminum, copper, magnesium, etc.

NORMALIZING: See heat treating definitions page 146 through 148.

OLSEN DUCTILITY TEST: A cupping test in which a piece of sheet metal, restrained except for the center, is deformed by a standard steel ball until fracture occurs. The height of the cup in thousandths of an inch at time of failure is a measure of the ductility.

OPEN HEARTH PROCESS:. One of the main methods used in the production of steel from hot metal (iron) produced in the blast furnace. The furnace can be charged with hot metal, and cold steel scrap for further refining into a carbon or alloy steel. Generally open hearth furnaces range from 75 to 450 tons of melting capacity in one heat.

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 to the point where heavy scale is formed and the steel product has a decarburized surface.

PHYSICAL PROPERTIES: Those properties familiarly discussed in physics, exclusive of those described under mechanical properties; for example: density, electrical conductivity and coefficient of thermal expansion.

PICKLING: The process of removing hot rolled mill scale from billets, bars or hot rolled sheets with sulphuric or hydrochloric acid. The scale is removed for hot rolled pickled and oiled sheets or for further processing of the hot rolled steel product into cold drawn bars and wire and cold rolled sheets and strip.

PLASTIC DEFORMATION: Deformation of a material that will remain permanent after removal of the load which caused it.

PRECIPITATION HARDENING: A process of hardening an alloy in which a constituent precipitates from a supersaturated solid solution. This process is used for non-ferrous alloys to change the mechanical properties of the metal and is also called aging or age hardening.

PROPORTIONAL LIMIT: Same as elastic limit.

QUENCHING: In the heat treating of steel, the step of cooling metals rapidly in order to obtain martensite by immersing or quickly cooling the steel in a quenching medium. The quenching media may be water, brine, oil, special solutions, salts or metals; and the intensity of the quench is determined by the temperature, volume and velocity of the media. In the case of air hardening tool steels the quenching medium is air at room temperatures.

REDUCTION OF AREA: The percentage difference between the original cross sectional area and that of the smallest area at the point of rupture. The percentage figure can be considered a measurement of ductility.

RESIDUAL STRESS: Macroscopic stresses that are set up within a metal as the result of nonuniform plastic deformation or thermal gradients. Stresses of this nature are caused by cold working or by drastic gradients of temperature from quenching or welding.

RESIDUALS: Elements present in an alloy in small quantities, but not added intentionally.

RESILIENCE: The tendency of a material to return to its original shape after the removal of a stress that has produced elastic strain.

RIMMED STEEL: Low-carbon steel in which incomplete deoxidation permits the metal to remain liquid at the top of the ingot, resulting in the formation of a bottom and side rim of relatively pure iron of considerable thickness. Steel products such as sheets produced from this type of ingot will have a very good surface quality free of surface defects.

ROCKWELL HARDNESS (TEST) -- See hardness tests.

ROLLED EDGES: Finished edges, the final contours of which are produced by side or edging rolls. The edge contours meet commonly used are square corners, rounded corners and a rounded edge.

ROLLING: A term applied to the operation of shaping and reducing metal in thickness by pressing it between rolls which compress, shape and lengthen it following the roll pattern. Steel is either hot rolled or cold rolled depending upon the product being manufactured,

ROLLING DIRECTION: The direction in which the steel product is rolled perpendicular to the axes of the rolls during rolling.

ROLLING MILLS: Equipment used for rolling down metal to a smaller size or to a given shape employing sets of rolls the contours of which determine or fashion the product into numerous intermediate and final shapes, e.g., blooms, slabs, rails, bars, rods, sections, plates, sheets and strip.

RUST: A corrosion product consisting of hydrated oxides of iron. This term is only applied to ferrous alloys.

SCALE: A complex iron oxide formed on the steel surface during the hot rolling operation or formed on steel parts which are heat treated in the presence of oxygen. SCLEROSCOPE See hardness tests.

SCRAP: Material unsuitable for direct use but usable for reprocessing by remelting.

SEGREGATION: Pertaining to chemical segregation which occurs during the solidification of the molten steel in the ingot mold. Rimmed and capped steels are considered to have high levels of segregation; semi-killed steels intermediate segregation; and, killed steels the minimum amount.

SEMIKILLED STEEL: A commonly used grade of steel manufactured for low carbon bars and structurals. A steel is considered semi killed when it is produced so that it is incompletely deoxidized and it contains sufficient dissolved oxygen to react with the carbon to form carbon monoxide to offset solidification shrinkage in the ingot.

SHEET STEEL: Either hot or cold rolled sheets produced on continuous sheet mill where the minimum width produced is 24. Sheet coils when slit to narrower widths is called slit sheet.

SHOT BLASTING: Cleaning surface of metal by air blast, using metal shot as an abrasive.

SLAB: A semi finished steel product intermediate between ingot and plate, with the width at least twice the thickness for rolling down into plates or sheets.

SOLID SOLUTION: Many metals possess the ability to dissolve certain other elements in the solid state forming solid solutions which in many ways are analogous to ordinary liquid solutions. In the case of steel the solid solution is called austinite. SOLUTION HEAT TREATMENT: Heating an alloy to a suitable temperature, holding at the temperature long enough to allow one or more constituents to enter into solid solution and then cooling rapidly enough to hold the constituents in solution. The alloy is left in a supersaturated, unstable state and may subsequently exhibit quench aging.

SPARK TESTING: This is an inspection method for quickly determining the approximate analyst of steel. It is intended primarily for the separation of mixed steel and when properly conducted, is a fast, accurate and economical method of separation. It consists in holding the sample against a high speed grinding wheel and noting the character and color of the spark which is compared with samples of known analysis.

STAINLESS STEEL: Corrosion resistant steel of a wide variety, but always containing a high percentage of chromium. The minimum chromium content is considered at 11% for stainless steel, although lesser amounts of chromium are found in stainless products such as those used for automobile mufflers. Stainless steels have the properties of being highly resistant to corrosion attack by organic acids, weak mineral acids, atmospheric corrosion, etc. Some standard grades of stainless steel also have 3.5 to 22% of nickel which further increases resistance to chemical and atmospheric corrosion.

STEEL: An iron-base alloy, malleable in same temperature range as initially cast, and containing carbon in amounts greater than .05% and less than about 2.00%. Other alloying elements may be present in significant quantities, but all steels contain at least small amounts of manganese and silicon.

STRAIN: Deformation produced on a body by an outside force.

STRIP STEEL -- (Cold Rolled) A flat cold rolled steel product rolled to widths 2316/16 and narrower, under .250 in thickness, which has been cold reduced to desired decimal thickness and temper on single stand, single stand reversing, or tandem cold mills in coil form from coiled hot rolled pickled strip steel.

TANDEM MILL: Arrangement of rolling mills, in direct line, allowing the metal to pass from one set of rolls to the next for the reduction of steel.

TEMPER: The state of or condition of a metal as to its hardness or toughness produced by either thermal or heat treatment and quench or cold working or a combination of same in order to bring the metal to its specified consistency.

TENSILE STRENGTH: The maximum load in pounds per square inch that the sample will carry before breaking under a slowly applied gradually increasing load during a tensile test.

TOLERANCE: The specified permissible deviation from a specified nominal dimension, the permissible variation in the size of the part or the allowable variation in chemistry.

TOOL STEEL: Actually, any grade of steel that can be used for a tool. Generally the term tool steel as applied in the steel industry is a grade of steel characterized by high hardness and resistance to abrasion coupled in many instances with resistance to softening at elevated temperatures. These properties are attained with high carbon and high alloy contents and the steel is usually melted in electric furnaces to assure cleanliness and homogeneity of the product.

TOUGHNES: SThe ability of a metal to absorb energy and deform plastically before fracturing. It is usually measured by the energy absorbed in a notch impact test such as the Charpy or Izod Impact Test. The area under the stress-strain curve in tensile testing is also a measure of toughness.

TUMBLING: Cleaning articles by rotating them in a cylinder with cleaning materials.

ULTIMATE STRENGTH: See tensile strength.

ULTRASONIC TESTING: A method of nondestructive testing of steel bars, plates or parts with high frequency sound waves produced with electronic equipment. The test is used for locating internal or surface discontinuities or inhomogeneities in materials.

WATER HARDENING: High carbon grades of tool steel, straight carbon steels and low alloy steels that are hardened by quenching in water during the heat treating operation.

WORK HARDENING: An increase in hardness and strength caused by plastic deformation at temperatures lower than the recrystallization range.

YIELD POINT: The yield point is the load per unit area at which a marked increase in deformation of the specimen occurs without increase of load during a tensile test.

YIELD STRENGTH: Stress corresponding to some fixed permanent deformation such as .1 or.2% offset from the modulus or elastic slope.

YOUNG'S MODULUS: Same as modulus of elasticity.

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