Age Hardening — Hardening by aging, usually after rapid cooling or cold working. Hardening is a result of a precipitation process, often submicroscopic, which occurs when a super-saturated solid solution is naturally aged at atmospheric temperatures or artificially aged in some specific range of elevated temperature. Aging occurs more rapidly at higher temperatures. (Synonymous with precipitation hardening.)
Air Frame Tubing — This tubing is produced for aircraft structural parts. This tubing is made to special surface quality, mechanical properties, and other characteristics required by Military Specifications (MIL-T- . . . .) and SAE Aeronautical Materials Specifications (AMS . . .).
Air Hardening — Heating a suitable grade of steel with high hardenability above the critical temperature range and then cooling in air for the purpose of hardening.
Aircraft Quality — Is a steel which has a special cleanliness rating determined by magnetic particle testing. The terms “Aircraft Quality” and “Magnaflux Quality” are considered synonymous.
Alloy Steel — All steels contain carbon and small amounts of silicon, sulfur, manganese, and phosphorus. Steels which contain intentional additions of elements other than these, or in which silicon and manganese are present in large amounts for the express purpose of improving or altering any of the physical or mechanical properties of the steel, are termed alloy steels.
Annealing — Annealing is a heat treatment process which usually involves a relatively slow cooling after holding the material for some time at the annealing temperature. The purpose of the annealing treatment may include the following: (a) to induce softness; (b) to remove internal stresses; (c) to refine the grain size; (d) to modify physical and/or mechanical properties; (e) to produce a definite microstructure; (f) to improve machinability. It is generally desirable to use more specific terms in describing the heat treatment to be used, e.g., finish anneal, or full anneal.
Austenitic Stainless Steel — Low carbon, iron-chromium-nickel stainless alloys containing more than 16 percent chromium, with sufficient nickel to provide an austenitic structure at normal temperatures. These alloys cannot be hardened by heat treatment, but can be hardened by cold working. They are normally non-magnetic, but can be slightly magnetic depending upon composition and amount of cold working.
Average Wall — A tube whose wall thickness is permitted to range over or under the specified nominal wall measurement within certain defined tolerances.
Bearing Quality Steels — Steels suitable for use in balls, rollers, and races of high quality anti-friction bearings.
Bevel — An angular cut on the I.D. or O.D. of a tube end.
Billet — As used in the manufacture of seamless tubes, a round bar with dimensions and other characteristics suitable for piercing into tubing.
Bloom — A semi-finished piece of steel, resulting from the rolling or forging of an ingot. A bloom is square or not more than twice as wide as thick, and usually not less than 36 square inch in cross-sectional area.
Borescope — An optical device used for inspecting under low magnification the inside surface of tubes.
Bright Anneal — Carried out in a controlled furnace atmosphere, so that surface oxidation is reduced to a minimum and the tube surface remains relatively bright.
Brinell Hardness — A measure of the degree of a material’s resistance to indentation. It is usually determined by measuring resistance to penetration.
Camber — The amount of curvature or deviation from exact straightness over any specified length of tubing.