Showing 61 terms
Accelerated Cooling
Cooling a plate with water immediately following the final rolling operation. Generally, the plate is water cooled from about 1400°F to approximately 1100°F.
Age Hardening
The hardening of steel induced by ageing.
Ageing
A change in properties that may occur gradually at atmospheric temperatures (natural ageing) and more rapidly at higher temperatures (artificial ageing).
Alloy Steel
Steel is considered to be an alloy steel when either (1) the maximum of the range given for the content of alloying elements exceeds one or more of the following percentages: manganese 1.65, silicon 0.60, copper 0.60; or (2) a definite range or definite minimum quantity of those elements considered alloys is specified. For example, chromium, molybdenum, and nickel.
Annealing
Heating to and holding at a suitable temperature, followed by cooling at a suitable rate, for such purposes as: 1. inducing softness, 2. improving machinability, 3. improving cold working properties, 4. obtaining a desired structure, 5. removing stresses. When applicable, the more specific terms, full annealing, isothermal annealing, or sub-critical annealing could be used.
Austenitizing
The process of forming the austenite phase by heating a ferrous alloy into the transformation range (partial austenitizing above the lower critical temperature) or above this range (complete austenitizing above the upper critical temperature).
Bainite
A decomposition product of austenite consisting of an aggregate of ferrite and carbide. In general, it forms at temperatures lower than those where very fine pearlite forms and higher than those where martensite begins to form on cooling.
Blue Annealing
Sub-critical annealing of bright steel during which the surface becomes oxidized to a blue temper color by the controlled admission of air and/or steam.
Blued Edges
Edges of sheet or strip which have become colored due to slight oxidation during the heat treatment.
Carbon Steel
A steel whose properties are determined mainly by the percentage of carbon present.
Cementite
A hard, brittle compound of iron and carbon (Fe3C) found in steel, contributing to its hardness and strength.
Chamfering
The removal of sharp edges. The term is practically synonymous with bevelling but has a less restricted application.
Cold Reduction
Reducing the thickness of steel sheet or strip to the finished gauge by heavy cold working between rolls.
Cold Rolling
Passing sheet or strip at room temperature between a pair of rotating rolls. The reduction in thickness may be very slight, as in the finishing process applied to hot-rolled sheets, or heavy, as in the cold rolling of narrow strip.
Cold Working
The operation of permanently altering the shape or dimensions of the steel, carried out at atmospheric temperature by, for example, cold rolling or cold reduction. Other methods of applying cold work are by drawing, pressing, forming, bending, swaging, etc.
Corrosion Fatigue
Fatigue accelerated by simultaneous corrosion.
Creep
Plastic deformation which proceeds slowly and continuously when stress is applied at elevated temperatures. In steel, creep is negligible below about 300°C.
Critical Grain Growth
A drastic enlargement of the grains when certain steels, particularly low-carbon steels, are subjected to a certain small amount of cold work and then annealed at a temperature below the upper critical point.
Decarburization
The loss of carbon from the surface of steel as a result of heating in a medium that reacts with the carbon.
Deoxidation
A process used during melting and refining of steel to remove and/or chemically combine oxygen from the molten steel to prevent porosity in the steel when it is solidified.
Ductility
Ability to undergo cold plastic deformation, usually as a result of tension.
Elastic Limit
The highest stress that can be applied without producing permanent deformation.
Elasticity
The property of the material by which it returns to its original dimensions after the removal of a stress.
Elongation
The increase in length of a tensile test piece when stressed. The elongation at fracture is usually expressed as a percentage of the original gauge length.
Etching
Treatment of prepared metal surfaces with acid or other reagents which, by differential attack, reveal the structure.
Fatigue
The tendency to fracture by means of a progressive crack under repeated alternating or cyclic stresses considerably below the tensile strength.
Ferrite
The room temperature form of alpha iron, one of the two major constituents of steel (cementite) in which it acts as the solvent to form solid solutions with such elements as manganese, nickel, silicon, and, to a small degree, carbon.
Galvanizing
The process of applying a protective zinc coating to steel or iron to prevent rusting and improve corrosion resistance.
Grain Growth
A coarsening of the crystal structure under certain conditions of heating. This should not be confused with critical grain growth.
Hardness
Resistance to deformation, indentation, abrasion, cutting, etc.
Hardness Test
A test of hardness, usually by determining the resistance of the material to indentation under standard conditions. The following are established methods of hardness testing: Brinell hardness test, Rockwell hardness test, and Vickers pyramid hardness test.
Hot Rolling
A manufacturing process where steel is rolled at high temperatures to reduce thickness, improve mechanical properties, and achieve desired shapes.
Hydrogen Embrittlement
A loss of ductility caused by the absorption of hydrogen, often occurring during electroplating or acid cleaning, leading to premature failure under stress.
Inclusions (Non-metallic inclusions)
Particles of oxides, silicates, sulfides, refractory materials, slag, etc., embedded in the metal.
Internal Stress
Stress produced within the metal by transformation, by temperature differences on heating or cooling, or by mechanical working.
Killing
Applying to finally heat-treated narrow strip a small amount of cold work to prevent kinks and stretcher strains on further manipulation. Skin passing is the usual method of killing.
Lamination
Separation into two or more layers due to some discontinuity in the steel, usually a layer of non-metallic inclusions.
Malleability
Capacity for undergoing deformation in all directions, usually cold deformation by hammering or squeezing.
Martensite
A microconstituent or structure in hardened steel, characterized by an acicular or needle-like pattern, and having the maximum hardness of any of the decomposition products of austenite.
Mild Steel
Carbon steel containing approximately 0.12 to 0.25 percent of carbon.
Mill Edge
The natural edge left when sheet or strip is rolled on the flat surfaces only.
Mill Shearing
Shearing the edges of a mill pack to approximate size.
Non-Destructive Testing (NDT)
Methods like ultrasonic testing, radiography, or magnetic particle inspection used to evaluate material properties without causing damage.
Normalizing
A heat treatment process that involves heating steel to a temperature above its critical range and then cooling it in air to refine the grain structure and improve mechanical properties.
Pearlite
A microconstituent of iron and steel consisting of a lamellar aggregate of ferrite and cementite (a compound of iron and carbon, Fe3C).
Pickling
The removal of scale by treatment with diluted acids or other chemicals.
Porosity
The presence of tiny holes or voids in a material, often caused by gas entrapment during solidification or improper processing.
Quenching & Tempering
A thermal process used to increase the hardness and strength of steel. It consists of austenitizing, then cooling at a rate sufficient to achieve partial or complete transformation to martensite. Tempering involves reheating to a temperature below the transformation range and then cooling at any rate desired. Tempering improves ductility and toughness but reduces the quenched hardness by an amount determined by the tempering temperature and time.
Roll Marks
Periodic surface marks due to some imperfection on the surface of a roll.
Seam
A longitudinal surface defect similar to a crack, except that in a cross-rolled sheet, such a defect would run transversely.
Sheared Edges
Edges resulting when a sheet or strip is either sheared or slit in rotary cutters.
Spheroidized Annealing
A prolonged heating of the steel in a controlled-atmosphere furnace at or near the lower critical point, followed by retarded cooling in the furnace, to produce a lower hardness than can be obtained by regular annealing.
Stainless Steel
A steel alloy with a minimum of 10.5% chromium content by mass, known for its corrosion resistance and ability to withstand harsh environments.
Stress Relieving
A thermal cycle involving heating to a suitable temperature, usually 1000-1200°F, holding long enough to reduce residual stresses from either cold deformation or thermal treatment, and then cooling slowly enough to minimize the development of new residual stresses.
Stretcher Strains (Luder lines)
A furrowed roughening of the surface of low-carbon sheet or strip due to uneven yielding in the first stages of cold deformation after annealing or, to a lesser degree, after normalizing or hot rolling.
Temper
The mechanical condition of strip as controlled by heat treatment and cold rolling. For example, a strip in the finally annealed condition is 'soft temper,' while strip subjected to heavy cold rolling as the final treatment is 'hard temper.' Between these are the intermediate tempers, of which the common ones are 'skin passed,' 'quarter hard,' and 'half hard.'
Tempering
The carbon trapped in the martensite transformation can be released by heating the steel below the A1 transformation temperature. This release of carbon from nucleated areas allows the structure to deform plastically and relieve some of its internal stresses. This reduces hardness and increases toughness, but it also tends to reduce tensile strength. The degree of tempering is dependent on temperature and time; temperature having the greatest influence.
Tensile Strength
The maximum load reached in a tensile test divided by the cross-sectional area of the gauge length portion of the test piece. Also termed maximum stress or ultimate tensile stress.
Tolerance
The permitted deviation from a specified dimension or weight, usually expressed as 'plus' or 'minus' on that quantity.
Toughness
The ability of a material to absorb energy and plastically deform without fracturing, often measured by impact testing.
Yield Stress
The stress (load divided by the original area of the cross-section of a test piece) at which, in a tensile test, elongation of the test piece first occurs without an increase in load.