Abrasion: A roughening or scratching of a surface due to abrasive wear. On aluminum parts, also known as a rub mark or traffic mark.
Abrasion-Resistant Steels (AR): A family of steel products developed for those applications involved in sliding and/or impact abrasion.
Abrasive Wear: The removal of material from a surface when hard particles slide or roll across the surface under pressure. The particles may be loose or may be part of another surface in contact with the surface being worn. Contrast with adhesive wear.
Accelerated Corrosion Test: A test conducted under controlled conditions that are considerably more severe than those natural conditions whose effects are presumably being investigated. The advantages of such a test is the relatively short time required. Results are useful for qualitative comparisons, but are not reliable for predicting anticipated life in actual service.
Accordion Reed Steel: Hardened, tempered, polished and blued or yellow flat steel with dressed edges. Carbon content about 1.00%. Material has to possess good flatness, uniform hardness and high elasticity.
Acid Steel: Steel melted in a furnace with an acid bottom and lining and under a slag containing an excess of an acid substance such as silica.
Acid-Brittleness: Brittleness resulting from pickling steel in acid; hydrogen, formed by the interaction between iron and acid, is partially absorbed by the metal, causing acid brittleness.
Age-Hardening: A process of aging that increases hardness and strength and usually decreases ductility. (see Precipitation Heat Treatment)
Air-Hardening Steel: A steel containing sufficient carbon and other alloying elements to harden fully during cooling in air or other gaseous mediums from a temperature above its transformation range. Such steels attain their martensitic structure without going through the quenching process. Additions of chromium, nickel, molybdenum and manganese are effective toward this end. The term should be restricted to steels that are capable of being hardened by cooling in air in fairly large sections, about 2 in. or more in diameter.
Aircraft Quality: Denotes material for important or highly stressed parts of aircraft for other similar purposes; such materials are extremely high quality requiring closely controlled, restrictive and special practices in their manufacture.
Aging: A process generally accelerated by temperature, wherein changes in mechanical properties occur in certain metals. These changes generally raise room temperature hardness, tensile and yield strength, while lowering ductility.
AISI: American Iron and Steel Institute. Published Steel Products Manual to Stainless and Heat Resisting Steels which provides information concerning tolerances, chemical analysis, definitions of technical terms and other related subjects which have been developed in the manufacture and use of stainless steels.
Alclad: Composite sheet produced by bonding either corrosion-resistant aluminum alloy or aluminum of high purity to base metal of structurally stronger aluminum alloy. The coatings are anodic to the core so they protect exposed areas of the core electrolytically during exposure to corrosive environment.
Alloy: A material that has metallic properties and is composed of two or more chemical elements of which at least one is a metal (i.e. steel is an alloy of carbon in iron; stainless steel is an alloy of carbon, chromium and sometimes nickel in iron.)
Alloying Elements: Those elements in alloys which are deliberately added during melting and refining to enhance the properties of that alloy.
Alloy Steel: An iron-based mixture is considered to be an alloy steel when manganese is greater than 1.65%, silicon over 0.5%, copper above 0.6%, or other minimum quantities of alloying elements such as chromium, nickel, molybdenum, or tungsten are present. An enormous variety of distinct properties can be created for the steel by substituting these elements in the recipe.
Alpha Brass: A copper-zinc alloy containing up to 38% of zinc. Used mainly for cold working.
Alpha Bronze: A copper-tin alloy consisting of the alpha solid solution of tin in copper. Commercial forms contain 4 or 5% of tin. This alloy is used in coinage, springs, turbine, blades, etc.
Alpha Iron: The polymorphic form of iron, stable below 1670°F, has a body centered cubic lattice, and is magnetic up to 1410°°F.
Aluminizing: Forming an aluminum or aluminum alloy coating on a metal by hot dipping, hot spraying, or diffusion.
Annealing: A process involving heating to a temperature at or above critical and cooling at a controlled rate, usually applied to induce softening. The process could alter mechanical properties, physical properties or micro structure.
Anodizing: (Aluminum Adic Oxide Coating) A process of coating aluminum by anodic treatment resulting in a thin film of aluminum oxide of extreme hardness. A wide variety of dye-colored coatings are possible by impregnation in process.
AOD (Argon Oxygen Decarburization): This term refers to both the process and the vessel that is used for the process in which hot metal from an electric furnace is refined to a chemical specification by blowing a mixture of gases (a combination of inert gas and oxygen) under the hot metal surface. The result removes carbon from ferroalloys to achieve a certain chemical specification. The economics of this process have indicated that this method is ideally suited for producing stainless, plus high and low-alloy steels.
ARC Furnace: An arc furnace is a melting device that gets its heat-generating capacity from the introduction of an electric arc to a charge of scrap materials and ferroalloys. This caused the melt-down to a liquid state known as “hot metal”.
Arc Welding: A group of welding processes wherein the metal or metals being joined are coalesced by heating with an arc, with or without the application of pressure and with or without the use of filler metal.
ASTM: American Society for Testing Materials is a voluntary standards development system. It is a non-profit organization which provides a forum for producers, users, consumers, and those having a general interest to meet on common ground and write standards for materials, products, systems and services.
Austempering: Quenching a ferrous alloy from a temperature above the transformation range, in a medium having a rate of heat abstraction high enough to prevent the formation of high-temperature transformation products, and then holding the alloy, until transformation is complete, at a temperature below that of pearlite formation and above that of martensite formation.
Automatic Gauge Control: Using hydraulic roll force systems, steelmakers have the ability to control precisely their steel sheet’s gauge (thickness)while it is traveling at more than 50 miles per hour through the cold mill. Using feedback or feed-forward systems, a computer’s gap sensor adjusts the distance between the reduction rolls of the mill 50-60 times per second. These adjustments prevent the processing of any off-gauge steel sheet.