Glossary R – Z


A photographic shadow image resulting from uneven absorption of penetrating radiation in a test object.


A method of nondestructive inspection in which a test object is exposed to a beam of x-rays or gamma rays and the resulting shadow image of the object is recorded on photographic film placed behind the object. Internal discontinuities are detected by observing and interpreting variations in the image caused by differences in thickness, density, or absorption within the test object. Variations of radiography include electron radiography, fluoroscopy, and neutron radiography. Commonly referred to as RT.

Residual elements

Elements present in an Alloy in small quantities, but not added intentionally.


The Engineering design, layout, and fabrication of pattern equipment for producing castings; including a study of the casting solidification program, feeding (risering) and gating, and fitting flasks.


Reservoir of molten metal from which casting feeds as it shrinks during solidification.

Riser, Blind

A riser that does not break through the top of the cope and is entirely surrounded by sand.

Riser, Open

A riser that breaks through the top of the cope; hot topping compound is applied to the exposed metal surface immediately after pouring.

Root of joint

The portion of a weld joint where the members are closest to each other before welding. In cross section, this may be a point, a line or an area.

Root pass

The first bead of a multiple-pass weld, laid in the root of joint.


Society of Automotive Engineers.

Salt fog test

An accelerated corrosion test in which specimens are exposed to a fine mist of a solution usually containing sodium chloride but sometimes modified with other chemicals; sometimes called a salt spray test.


An element added to Stainless steel to improve machinability. Element 34; Symbol: Se.


In austenitic Stainless steels, the precipitation of chromium carbides, usually at grain boundaries, on exposure to temperatures of about 550 to 850 degrees C (about 1000 to 1550 degrees F), leaving the grain boundaries depleted of chromium and therefore susceptible to preferential attack by a corroding (oxidizing) medium.


Steel Founders’ Society of America.

Shear strength

Maximum shear stress a material is capable of withstanding without failure.

Shielded metal arc welding

Arc welding in which the arc and the weld metal are protected by a gaseous atmosphere, the products of decomposition of the covering on a consumable metal electrode.

Shot blasting

Blasting with metal shot; usually used to remove deposits or scale more rapidly or more effectively than can be done by sand blasting.

Shot peening

Cold working the surface of a metal by metal-shot impingement.

Shrinkage rule

A measuring ruler with graduations expanded to compensate for the change in the dimensions of the solidified casting as it cools in the mold.

Sigma phase

A hard, brittle, nonmagnetic intermetallic phase. Found in some Stainless steels after heating to temperatures between 1300 and 1800 F (700 and 1000 C).


An important element, chemically classified as a nonmetal, metallurgically, as a metal. Added to steels as a deoxidizer, to Stainless steels to improve fluidity for casting and to control oxide film formation, to heat resisting Alloys for carburization resistance, and to some Ni-based Alloys for increased hardness. Element 14; Symbol: Si.


Shielded Metal Arc Welding.


Prolonged heating of a metal at a selected temperature.


That material which has a tendency to resist any attempt to change its size or shape.


The change in state from liquid to solid on cooling through the melting temperature or melting range.


In a constitution or equilibrium diagram, the line representing the temperatures at which various compositions finish freezing on cooling or begin to melt on heating.

Specific gravity

A numerical value representing the weight of a given substance as compared with the weight of an equal volume of water at 39 degrees F (3.9 degrees C), for which the specific gravity is taken as 1.000.

Specific heat

The ratio of the thermal capacity (the quantity of heat required to produce a unit change in the temperature of a unit mass) of a substance to that of water at 15 C.

Specific volume

Volume of one gram of a substance at a specific temperature, usually 20 degrees C (68 degrees F).

Stainless steel

A wide range of steels containing chromium or chromium and other elements such as nickel, molybdenum, copper, manganese, and nitrogen, exhibiting high resistance to corrosion.


An iron-base Alloy containing carbon, usually manganese, and often other Alloying elements.


A measure of the relative change in the size or shape of a body.

Strain rate

The time rate of straining for the usual tensile test.


Force per unit area, often thought of as force acting through a small area within a plane.

Stress-corrosion cracking (SCC)

A cracking process that requires the simultaneous action of a corrosive and sustained tensile stress. This excludes corrosion-reduced sections that fail by fast fracture. It also excludes intercrystalline or transcrystalline corrosion, which can disintegrate an Alloy without applied or residual stress. Stress-corrosive cracking may occur in combination with hydrogen embrittlement.

Stress relieving

Heating to a suitable temperature, holding long enough to reduce residual stresses and then cooling slowly enough to minimize the development of new residual stresses.

Stringer bead

A type of weld bead made without appreciable weaving motion.

Structure (Cast structure)

The size and disposition of the constituents of a metal as cast.


A nonmetallic element, occurring as an undesirable tramp (trace) element in most ferrous Alloys, but added to some grades to improve machinability. Element 16; Symbol: S.


An Alloy developed for very high temperature use where relatively high stresses are encountered and where oxidation resistance is needed.


In heat treatment, to reheat hardened steel or hardened cast iron to some temperature below the transformation temperature for the purpose of decreasing hardness and increasing toughness. The process may also be applied to normalized steel.


Degree of warmth or coldness in relation to an arbitrary zero measured on one or more of accepted scales, as Centigrade, Fahrenheit, etc.

Tensile strength

The maximum stress in uniaxial tension testing which a material will withstand prior to fracture. The ultimate tensile strength is calculated from the maximum load applied during the test divided by the original cross sectional area.


A device for measuring temperatures, consisting of lengths of two dissimilar metals or Alloys that are electrically joined at one end and connected to a voltage-measuring instrument at the other end.

TIG Welding

Tungsten inert-gas welding.

Tool steel

Any of a class of carbon and Alloy steels commonly used to make tools.

Transformation ranges

Those ranges of temperature within which a phase (such as austenite) forms during heating and transforms during cooling. The limiting temperatures of the ranges depend on the composition of the Alloy and on the rate of change of temperature, particularly during cooling.

Transformation temperature

The temperature at which a change in phase occurs. This term is sometimes used to denote the limiting temperature of a transformation range.

Transition temperature

An arbitrarily defined temperature that lies within the temperature range in which metal fracture characteristics (as usually determined by tests of notched specimens) change rapidly, such as from primarily fibrous (shear) to primarily crystalline (cleavage) fracture.


Literally, “across”, usually signifying a direction or plane perpendicular to the direction of rolling.

TTT curve

Abbreviation for Time-Temperature-Transformation curve.


Tungsten is added to certain Stainless steels to improve resistance to pitting and crevice corrosion. It is a very pronounced carbide former and promotes ferrite. In steels, it improves toughness and prevents grain growth. Element 74; Symbol W.

Tungsten inert-gas welding

Inert-gas shielded welding using a tungsten electrode.

Ultimate tensile strength

The maximum tensile stress a metal can stand.

Ultrasonic testing

A nondestructive method of testing metal for flaws based on the fact that ultrasonic waves are reflected and refracted at the boundaries of a solid medium. Commonly referred to as UT.


A groove melted into the base metal adjacent to the toe of a weld and left unfilled.

Vacuum induction melting

A process for remelting and refining metals in which the metal is melted inside a vacuum chamber by induction heating. The metal may be melted in a crucible, then poured into a mold.


In steels, refines the primary grain and thus the casting structure. Pronounced carbide former, thus providing increased wear resistance, edge holding quality, and high temperature strength. Element 23; Symbol: V.

Weave bead

A type of weld bead made with transverse oscillation.


A specific or relative measure of the ability of a material to be welded under a given set of conditions.


Joining two or more pieces of material by applying heat or pressure, or both, with or without filler material, to produce a localized union through fusion or recrystallization across the interface.

Welding procedure

The detailed materials, methods, and practices involved in the production of a weld.

Welding technique

The details of a welding operation that, within the limitations of a welding procedure, are performed by the welder.

White cast iron

Cast iron that shows a white fracture because the carbon is in combined form.


Welding Procedure Qualification Record.


Welding Procedure Specification.

Yield ratio

The ratio of yield strength to ultimate tensile strength.