U – Z
Ultimate Strength
The maximum conventional stress, tensile, compressive, or shear, that a material can withstand.
Ultimate Tensile Strength
The maximum stress in pounds per square inch (psi) that causes the material to fracture.
Ultrasonic Frequency
A frequency, associated with elastic waves, that is greater than the highest audible frequency, generally regarded as being higher than 15 kc per sec.
Ultrasonic Testing
A nondestructive test applied to sound-conductive materials having elastic properties for the purpose of locating inhomogeneities or structural discontinuities within a material by means of an ultrasonic beam.
Ultrasonic Waves
Waves of ultrasonic frequency. They include longitudinal, transverse, surface, and standing waves.
Universal Mill
A rolling mill in which rolls with a vertical axis roll the edges of the metal stock between some of the passes through the horizontal rolls.
Upset
(1) The localized increase in cross-sectional area resulting from the application of pressure during mechanical fabrication or welding. (2) That portion of welding cycle during which the cross-sectional area is increased by the application of pressure.
Upsetting
(1) A metal working operation similar to forging. (2) The process of axial flow under axial compression of metal, as in forming heads on rivets by flattening the end of wire.
Utility Sheet Aluminum
Mill finish coiled or flat sheet of unspecified composition and properties produced in specific standard sizes and suitable for general building trade usage.
Vacancy
A type of structural imperfection in which an individual atom site is temporarily unoccupied.
Vacuum Degassing
A process wherein impurities are removed from molten metal by means of a vacuum.
Vacuum Melting
Melting in a vacuum to prevent contamination from air, as well as to remove gases already dissolved in the metal; the solidification may also be carried out in a vacuum or at low pressure.
Valve
A mechanical device by which the flow of liquid, gas or other objects may be regulated by moveable parts that open, close or obstruct one or more openings or passageways.
Vanadium
Chemical symbol V. Element No. 23 of the periodic system; atomic weight 50.95. Gray-white, hard metal, unaffected by atmospheric influences or alkalis but soluble in most strong acids; melting point 3119 (degrees) F.; boiling point about 6150 (degrees) F.; specific gravity 5.87. It cannot be electrodeposited. Its principal functions as an alloy in the making of tool steels. (1) Elevates coarsening temperature of austenite (promotes fine grain). (2) Increases hardenability (when dissolved) (3) Resists tempering and causes marked secondary hardening.
VAR (Vacuum Arc Remelt)
These ultra clean steels are first melted in an electric furnace, then the electric furnace ingot is remelted in a vacuum. This draws off substantial amounts of gases and non-metallic inclusions, producing a clean steel.
Veining
A type of sub-boundary structure that can be delineated because of the presence of a greater-than-average concentration of precipitate or solute atoms.
Vibrator Reed Steel
Hardened, tempered and white polished wxtra precision rolled. Carbon content about 1.00. Steel must withstand great fatigue stresses.
Vickers Hardness (Test)
Standard method for measuring the hardness of metals, particularly those with extremely hard surfaces; the surface is subjected to a standard pressure for a standard length of time by means of a pyramid shaped diamond. The diagonal of the resulting indention is measured under a microscope and the Vickers Hardness value read from a conversion table.
VIM (Vacuum Induction Melted)
Initial heat is melted in a vacuum, drawing off gasses and other impurities. This provides cleaner and therefore stronger metal.
Virgin Metal
Metal obtained directly from ore and not used before.
Water Stain Also called White Rust
If oxygen is excluded from the wraps of coiled product, from the inner surfaces of stacked flat products or from the faying surfaces of extruded products, and should moisture be permitted to enter those areas through condensation or water exposure, the moisture will have the tendency to steal the oxygen from the skin of aluminum. When this happens, the surface of the metal will become roughened and eventually pitted unless the water is removed and those surfaces are kept exposed to the air or kept free from further moisture. Although water stain is usually only an aesthetic complaint, it can become severe enough to become a structural problem by reducing metal thickness.
Wear Resistance
The resistance to sliding abrasion.
Weld Bead
The built-up portion of a weld, formed either from the filler metal or from the parent metal.
Welding
This is a process used to join metals by the application of heat.
Wrought Iron
Iron containing only a very small amount of other elements, but containing 1-3% by weight of slag in the form of particles elongated in one direction, giving the iron a characteristic grain. Is more rust-resistant than steel and welds more easily.
Wrought Products
Products which began as raw material castings and are mechanically worked by processes such as rolling, extruding, forging, etc.
Wustite
The oxide of iron of lowest valence which exist over a wide range of compositions the do not quite include the stoichiometric composition FeO.
X-Rays
Light rays, excited usually by the impact of cathode rays on matter, which have wave lengths between about 10-6 cm, and 10-9 cm; also written X-rays, same as Roentgen rays.
Yellow Brass
65% copper and 35% zinc. Also known as High Brass. A copper-zinc alloy, named for its yellow hue. Formerly a very popular alloy, but now largely replaced by Cartridge Brass.
Yield Point
The load per unit of original cross section at which, in soft steel, a marked increase in deformation occurs without increase in load.
Yield Strength
The stress at which a material exhibits a specified deviation from propertionality of stress and strain. An offset of 0.2% is used for many metals.
Young’s Modulus
The coefficient of elasticity of stretching. For a stretched wire, Young’s Modulus is the ratio of the stretching force per unit cross-sectional area to the elongation per unit length. The values of Young’s Modulus for metals are of the order 10(12) dynes per square cm.
Zinc
Chemical Symbol Zn. Element No. 30 of the periodic system; atomic weight 65.38. Blue-white metal; when pure, malleable and ductile even at ordinary temperatures; melting point 787 (degrees) F.; boiling point 1665 (degrees) F., specific gravity 7.14. Can be electrodeposited; it is extensively used as a coating for steel and sheet zinc finds many outlets, such as dry batteries, etc. Zinc-base alloys are of great importance in die casting. Its most important alloy is brass.