Metallurgical Terms


Any metallic material containing two or more chemical elements.

Impact Test

A test for evaluating the resistance of a material to shock stresses.

Alloy Steel

A steel containing, in addition to carbon and normal impurities, some alloying element or elements intentionally added or permitted to remain for the purpose of modifying or enhancing its chemical, physical or mechanical properties.


In non-destructive inspection a response or evidence of a response that requires interpretation to determine its significance.

Alloying Element

Any element intentionally added to or allowed to remain in a metal, for the purpose of modifying chemical, physical or mechanical properties.

Magnetic Particle Inspection

A method of examination in which an object is magnetized and a magnetic powder is applied to the surface. Faults which cause disconuities are revealed by the concentration of powder


A process involving heating and cooling, applied usually to induce softening.

Mechanical Properties

Properties relating to the behaviour of materials under load in conventional mechanical tests, such as elastic moduli, tensile strength, elongation, hardness.


A semi-finished rolled or forged steel product, usually square or round in section, intended for re-rolling or forging.


Heating steel to, and if necessary holding at, a suitable temperature above the transformation range,followed by cooling in a still atmosphere at ambient temperature, in order to produce a medium-to-fine pearlitic microstructure.


A process for covering one metal with another. Processes include hot rolling, explosive bonding, welding, casting, chemical deposition and heavy electro plating.


A homogeneous, physically distinct part of a system and which is confined to a definite region of space being separated from the other parts of the system by bounding interfaces.


The time-dependant part of plastic deformation in a material under stress.


Removal of oxide films from metal by immersion in an acid.

Drop Forging

A forging produced by hot working metal with a drop hammer.

Plastic Deformation

Deformation that does or will remain permanent after removal of the load that caused it.


That property of a material that permits plastic deformation before fracture.

Proof Stress

That stress at which a material exhibits a specified limiting permanent set. Synonymous with yield strength.

Duplex Structure

A microstructure containing two phases. Example of this is Austenite and Ferrite in Duplex Stainless Steels.

Reduction of Area

The fraction by which the original cross-sectional area of a tensile test specimen is reduced at the place of fracture.

Dye Penetrant Testing

Penetrant with dye added to make it more readily visible under ordinary or ultra violet light. Commonly used for detecting surface cracks.


The replacement of the crystal grains of a metal or alloy by a new generation of grains.

Eddy Current

Non-destructive testing method in which eddy current flow is induced in the test component. Changes in the flow caused by structural variation in the component are detected by a nearby coil or coils and subsequently analysed by suitable instrumentation and other techniques.

Salt Bath

The term used in reference to the bath of molten salt that is used for the heating, hardening or tempering of various alloys.


In tensile testing, the increase in the gauge length, measured after fracture of the test specimen within the gauge length, usually expressed as a percentage of the original gauge length.

Solution Heat Treatment

A treatment in which an alloy is heated to a suitable temperature and held at this temperature for a sufficient length of time to allow an element or elements to enter into solid solution.


The forcing of compressed material through an orifice or into a cavity.


A heat treatment process having as its object the production of a microstructure in which the dispersed phase occurs in a roughly spheroidal or globular form.


A condition in metals resulting from fluctuating stresses, leading to failure at a stress substantially below the normal tensile strength of the material.

Stainless Steel

Traditionally a stainless steel is considered to be an iron based alloy containing more than 12% chromium.

Flare Test

A test applied to tubing, involving a tapered expansion over a cone.


The intensity of force acting on any plane within a body.

Flattening Test

A quality test for tubing in which a specimen is flattened between parallel plates that are closed to a specified gap.

Stress Relieving

Heating a metal to, and if necessary holding at, some temperature generally below the recrystallization range, followed by uniform cooling for the sole purpose of removing internal stresses.


The shaping of metal using a hammer or a press.

Tensile Strength

The maximum nominal stress reached during a tensile test on a material, ie the maximum load divided by the original crosssectional area.


The resistance offered by a metallic material to plastic deformation by indentation or penetration.

Ultrasonic Test

A test to determine the presence of internal flaws involving the transmission of high frequency sound waves that are reflected by the defects.

Heat Affected Zone

That portion of the base metal that is not melted during brazing, cutting or welding but whose microstructure and properties are altered by the heat generated by the process.

Work Hardening

An increase in the hardness and / or mechanical strength of a metal resulting from plastic deformation.

High Frequency Furnace

A furnace in which currents at a frequency above 500 Hertz are used to induce eddy currents in a charge which in turn generate heat in a conducting material.

Yield Point

In mechanical testing of certain metals, notably annealed or normalized low-carbon steels, this is the point on the load-deformation curve at which macroscopic plastic deformation commences under a constant or reduced load.

Young’s Modulus

The ratio of axial stress to axial strain in the elastic region of a tensile test.