Term	Definition
Acid Steel	Steel produced in a furnace with an acid lining, i.e.
	consisting of a siliceous refractory and under a siliceous
	slag. With an acid slag, carbon, silicon and manganese
	only are removed so that the pig iron must not contain
	sulphur and phosphorus in percentages exceeding those
	permissible for the specification being made. Most steel
	manufactured today is in furnaces with basic linings.
Air-Hardening Steel	Sometimes referred to as self-hardening steel. A steel
	that becomes fully hardened when cooled in air from
	above its critical point and does not require rapid
	quenching by oil or water. The risk of distortion is
	greatly reduced by air hardening. High Speed Steel was
	one of the earliest examples of this type of steel.
Allotropy	The property possessed by certain elements to exist in
	two or more distinct forms that are chemically identical
	but have different physical properties. In the case of iron
	the crystal structure has one form at room temperature
	and another at high temperature. When heated above
	910 deg C the atomic structure changes from body centered
	cubic to face centered cubic but reverts again when
	cooled. The allotropy of iron modifies the solubility of
	carbon, and it is because of this that steel can be
	hardened.
Alloy Steel	A steel to which one or more alloying elements other
	than carbon have been deliberately added (e.g.
	chromium, nickel, molybdenum) to achieve a particular
	physical property.
Alpha Iron	The body centered cubic form of iron which, in pure iron,
	exists up to 910 deg C.
Annealing	Heating steel to, and holding at a suitable temperature,
	followed by relatively slow cooling. The purpose of
	annealing may be to remove stresses, to soften the
	steel, to improve machinability, to improve cold working
	properties, to obtain a desired structure. The annealing
	process usually involves allowing the steel to cool slowly
	in the furnace.
Arc Furnace	A steel melting furnace in which heat is generated by an
	arc between graphite electrodes and the metal. Both
	carbon and alloy steels are produced in electric arc
	furnaces and scrap rather than molten metal is used as
	the base material. Furnaces with capacities up to 200
	tons are now in use.
Austempering	Quenching from a temperature above the transformation
	range to a temperature above the upper limit of
	martensite formation, and holding at this temperature
	until the austenite is completely transformed to the
	desired intermediate structure, for the purpose of
	conferring certain mechanical properties.
Austenite	The solid solution of carbon in gamma (face centered
	cubic) iron.
Austenitic Steels	Steels containing high percentages of certain alloying
	elements such as manganese and nickel which are
	austenitic at room temperature and cannot be hardened
	by normal heat-treatment but do work harden. They are
	also non-magnetic. Typical examples of austenitic steels
	include the 18/8 stainless steels and 14% manganese
	steel.
B	Chemical symbol for Boron.
Bainite	An acicular aggregate of ferrite and carbide particles
	formed when austenite is transformed on cooling at
	temperatures in the intermediate (200-450 deg C) range,
	i.e. above the martensite and below the pearlite
	range.
Balanced Steel	Steels in which the deoxidisation is controlled to
	produce an intermediate structure between a rimmed
	and killed steel. Sometimes referred to as semi-killed
	steels, they possess uniform properties throughout the
	ingot and amongst their applications are boiler plate
	and structural sections.
Base Metal	A metal which oxidises when heated in air, e.g. lead,
	copper, tin, zinc, as opposed to noble metals such as
	gold and platinum.
Basic Steel	Steel produced in a furnace in which the hearth
	consists of a basic refractory such as dolomite or
	magnesite, as opposed to steel melted in a furnace
	with an acid lining. The basic process permits the
	removal of sulphur and phosphorous and in this
	respect is superior. Present day BOS and electric arc
	furnaces use basic linings.
Be	Chemical symbol for Beryllium.
Bend Test	Bending tests are carried out to ensure that a metal
	has sufficient ductility to stand bending without
	fracturing. A standard specimen is bent through a
	specified arc and in the case of strip, the direction of
	grain flow is noted and whether the bend is with or
	across the grain.
Bessemer Process	A method of producing steel, first introduced in the
	last century, where air is blown under pressure
	through molten iron to remove the impurities by
	oxidation. The development of the process has led to
	the present day Basic Oxygen Steel making plants
	that account for bulk production of commercial quality
	steels in the UK.
Bi	Chemical symbol for Bismuth.
Billet	A section of steel used for rolling into bars, rods and
	sections. It can be a product of the ingot route, or
	increasingly today produced directly by continuous
	casting.
Blast Furnace	A tall, cylindrical, refractory lined furnace for the
	production of pig iron or hot metal for direct
	conversion into steel.
Bloom	A large square section of steel intermediate in the
	rolling process between an ingot and a billet. Blooms
	are now also being produced by the continuous
	casting process eliminating the necessity of first
	producing an ingot.
Boron Steels	The addition of boron in the range 0.0005-0.005% to
	certain steels increases the hardenability. A range of
	boron steels is now listed in the current BS 970 and
	are widely used for the production of cold headed
	fastenings.
Brazing	Brazing is a method of joining metal parts together by
	fusing a layer of brass between the adjoining surfaces.
	A red heat is necessary and a flux is used to protect
	the metal from oxidation.
Bright Annealing	An annealing process that is carried out in a controlled
	atmosphere furnace or vacuum in order that oxidation
	is reduced to a minimum and the surface remains
	relatively bright.
Bright Drawing	The process of drawing hot rolled steel through a die
	to impart close dimensional tolerances, a bright, scale
	free surface, and improved mechanical properties. The
	product is termed bright steel.
Brinell Hardness Test	The Brinell hardness test for steel, involves impressing
	a ball 10 mm diameter, of hard steel or tungsten
	carbide, with a loading of 3000 kilograms into the
	steel surface. The hardness of the steel is then
	determined by measurement of the indentation. For
	steels with a hardness over 500 BHN the Vickers test
	is more reliable.
C	Chemical symbol for Carbon.
Ca	Chemical symbol for Calcium.
Calcium	In the form of calcium silicide acts as a deoxidizer
	and degasifier when added to steel. Recent
	developments have found that carbon and alloy
	steels modified with small amounts of calcium show
	improved machinability and longer tool life.
	Transverse ductility and toughness are also
	enhanced.
Carbon	Carbon is an essential element in steel, it is added
	in specific amounts to control the hardness and
	strength of the material. In general, increased
	carbon content reduces ductility but increases
	tensile strength and the ability of the steel to
	harden when cooled rapidly from elevated
	temperatures.
Carbon Steel	A steel whose properties are determined primarily
	by the amount of carbon present. Apart from iron
	and carbon, manganese up to 1.5% may be
	present as well as residual amounts of alloying
	elements such as nickel, chromium, molybdenum,
	etc. It is when one or more alloying elements are
	added in sufficient amount that it is classed as an
	alloy steel.
Carbo-Nitriding	A case-hardening process in which steel
	components are heated in an atmosphere
	containing both carbon and nitrogen.
Carburising	The introduction of carbon into the surface layer of
	a steel that has a low carbon content. The process
	is carried out by heating the components in a solid
	liquid, or gaseous carbon containing medium. The
	depth of penetration of carbon into the surface is
	controlled by the time and temperature of the
	treatment. After carburising it is necessary to
	harden the components by heating to a suitable
	temperature and quenching.
Case-Hardening	The process of hardening the surface of steel
	while leaving the interior unchanged. Both carbon
	and alloy steels are suitable for case-hardening
	providing their carbon content is low, usually up to
	a maximum of 0.2%. Components subject to this
	process, particularly in the case of alloy steels,
	have a hard, wear-resistant surface with a tough
	core.
Cast Iron	A definition can be applied that Cast Iron is an
	alloy of iron and carbon in which the carbon is in
	excess of the amount that can be retained in solid
	solution in austenite at the eutectic temperature.
	Carbon is usually present in the range of 1.8% to
	4.5%, in addition, silicon, manganese, sulphur and
	phosphorus are contained in varying amounts.
	Various types of cast iron are covered by a British
	Standard classification and includes grey, malleable
	and white irons. Elements such as nickel,
	chromium, molybdenum, vanadium can be added to
	produce alloy cast irons.
Cast Steel	A term originally applied to crucible steel and
	sometimes today used to describe tool steels. The
	term is misleading and is falling into misuse. It can
	also be applied to steel castings made by pouring
	molten steel into a mold but which are not subject
	to further forging or rolling.
Cb	Chemical symbol for Columbium.
Ce	Chemical symbol for Cerium.
Cementite	An iron carbide (Fe3C) constituent of steel. It is
	hard, brittle and crystalline. Steel which has cooled
	slowly from a high temperature contains ferrite and
	pearlite in relative proportions varying with the
	chemical composition of the steel. Pearlite is a
	lamellar structure of ferrite and cementite.
Charpy Test	A test to measure the impact properties of steel. A
	prepared test piece, usually notched, is broken by a
	swinging pendulum. The energy consumed in
	breaking the test piece is measured in Joules. The
	more brittle the steel the lower the impact strength.
	Izod is a similar and more widely used impact test
	in this country. Both are quoted in the current
	edition of BS 970.
Chromium	When used as an alloying element, chromium
	increases the hardenability of steel and in
	association with high carbon gives resistance to
	wear and abrasion. Chromium has an important
	effect on corrosion resistance and is present in
	stainless steels in amounts of 12% to 20%. It is
	also used in heat-resisting steels and high duty
	cast irons.
Co	Chemical symbol for Cobalt.
Cobalt	An alloying element used in tool, magnet and heat
	resisting steels. Together with tungsten and
	molybdenum, cobalt is used to form the super high
	speed steels. It improves the red hardness value of
	the steel, that is, it enables the steel to resist
	softening at a high temperature or in the case of a
	cutting tool to hold its edge under severe
	conditions.
Coefficient of Expansion	The ratio of change in length, area, or volume per
	degree to the corresponding value at a standard
	temperature.
Cogging	An intermediate rolling process when a hot ingot is
	reduced to a bloom or slab in a cogging mill.
Cold Drawing	The process of reducing the cross sectional area of
	wire, bar or tube by drawing the material through a
	die without any pre-heating. Cold drawing is used
	for the production of bright steel bar in round
	square, hexagonal and flat section. The process
	changes the mechanical properties of the steel and
	the finished product is accurate to size, free from
	scale with a bright surface finish.
Cold Working	Altering the shape or size of a metal by plastic
	deformation. Processes include rolling, drawing,
	pressing, spinning, extruding and heading, it is
	carried out below the recrystallisation point usually
	at room temperature. Hardness and tensile strength
	are increased with the degree of cold work while
	ductility and impact values are lowered. The cold
	rolling and cold drawing of steel significantly
	improves surface finish.
Contact Corrosion	When two dissimiliar metals are in contact without
	a protective barrier between them and they are in
	the presence of liquid, an electrolytic cell is
	created. The degree of corrosion is dependent on
	the area in contact and the electro-potential
	voltage of the metals concerned. The less noble of
	the metals is liable to be attacked, i.e. zinc will act
	as a protector of steel in sea water whereas copper
	or brass will attack the steel in the same
	environment.
Continuous Casting	A method of producing blooms, billets and slabs in
	long lengths using water cooled molds. The
	castings are continuously withdrawn through the
	bottom of the caster while the teeming of the
	metal is proceeding. The need for primary and
	intermediate mills and the storage and use of large
	numbers of ingot molds is eliminated. The
	continuous casting process is also used in the
	production of cast iron, aluminium and copper
	alloys.
Controlled Atmosphere	A gas or mixture of gases in which steel is heated
	to produce or maintain a specific surface condition.
	Controlled atmosphere furnaces are widely used in
	the heat treatment of steel as scaling and
	decarburisation of components is minimised by this
	process.
Core	In the case of steel this refers to a component that
	has been case-hardened where the centre is softer
	than the hard surface layer or case. It can also be
	applied to the central part of a rolled rimming steel.
Corrosion Fatigue	Fatigue that arises when alternating or repeated
	stress combines with corrosion. The severity of the
	action depends on the range and frequency of the
	stress, the nature of the corroding condition and
	the time under stress.
Cr	Chemical symbol for Chromium.
Creep	The form of plastic deformation that takes place in
	steel held for long periods at high temperature.
	Methods of creep testing involve the determination
	of strain/time curves under constant tensile load
	and at constant temperature.
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Critical Cooling R	The slowest rate of cooling from the hardening
	temperature which will produce the fully hardened
	martensitic condition.
Critical Point	This generally refers to a temperature at which
	some chemical or physical change takes place.
	These transformations cause evolution of heat on
	cooling or absorption of heat on heating and
	appear as discontinuities or arrest points in the
	heating and cooling curves. The temperatures vary
	with the carbon content of the steel and the rate of
	cooling.
Critical Temperature	The temperature at which some phase change
	occurs in a metal during heating or cooling, i.e. the
	temperature at which an arrest or critical point is
	shown on heating or cooling curves.
Crystalline Fracture	A type of fracture that appears bright and glittering,
	it having formed along the cleavage planes of the
	individual crystals. Normally an indication that
	brittle fracture has occurred.
Cu	Chemical symbol for Copper.
Cyanide Hardening	A process of introducing carbon and nitrogen into
	the surface of steel by heating it to a suitable
	temperature in a molten bath of sodium cyanide, or
	a mixture of sodium and potassium cyanide, diluted
	with sodium carbonate and quenching in oil or
	water. This process is used where a thin case and
	high hardness are required.
Decalescence	A term used in reference to the absorption of
	heat without a corresponding increase in
	temperature, when steel is heated through the
	critical points (phase changes).
Decarburisation	The loss of carbon from the surface of steel as
	a result of heating in a carbon weak
	atmosphere. During the rolling of steel hot
	surfaces are exposed to the decarburising
	effects of oxygen in the atmosphere and as a
	result the surface is depleted of carbon. In
	steels where the components are to be
	subsequently heat treated it is necessary to
	remove the decarburised surface by machining.
Delta Iron	When pure or practically carbon-free iron is
	cooled from above its melting point it solidifies
	at about 1535 deg C as delta iron having a
	body-centred cubic lattice structure, which
	persists down to about 1400 deg C. On further
	cooling it undergoes an allotropic change to
	gamma iron which has a face-centred cubic
	lattice and is non-magnetic.
Deoxidation	Elements such as silicon and aluminium when
	added to molten steel react to form stable
	oxides and reduce the amount of dissolved
	oxygen. The solubility of oxygen in steel is
	reduced as temperature is lowered during
	solidification and the excess oxygen combines
	to form carbon monoxide. If the molten metal
	is not deoxidised the effervescence produced
	by the evolution of carbon monoxide during
	solidification would result in blow holes and
	porosity. Steel treated in this way is termed,
	"Killed Steel".
Descaling	It is necessary to remove the scale from hot
	rolled bars or coil before bright drawing. This is
	normally carried out by shot blasting or pickling
	in acid. Other methods of descaling steel
	products include sand blasting, flame
	descaling and tumbling.
Deseaming	A process of burning out defective areas on
	the surface of ingots, blooms or billets. The
	condition of the surface is such that it can then
	be rolled or forged into a satisfactory product.
Diamond Pyramid Hardness	This test, more commonly known as the
Test	Vickers test, finds greater use in the laboratory
	than the workshop. It employs a pyramid
	shaped diamond with an included angle of
	136o which is impressed into the specimen
	using loads of 5 to 120 kg making a small
	square impression. This test is used for
	finished or polished components because the
	impression can be very small. The diamond
	pyramid hardness number is obtained from a
	calculation based on measuring the diagonals
	of the impressions in the steel.
Die	The term die is most commonly used in
	tooling, i.e. press tools "punch and die" but
	there are many other types of die, e.g. thread
	cutting dies, forming dies, forging dies,
	die-casting dies, etc. The term when applied to
	steel often refers to drawing dies through
	which hot rolled wire and bar are drawn to
	produce the finish and dimensional accuracy
	that is required for bright steel.
Dislocation	A discontinuity in the crystal lattice of a metal.
	The movement of dislocations under stress
	may be used to explain slip, creep, plastic
	yielding, etc.
Dolomite	A natural carbonate of calcium and magnesium
	generally used as a flux in blast furnaces.
Drawing	The process of pulling metal wire, rods, or bars
	through a die with the effect of altering the
	size, finish and mechanical properties. In the
	USA, it is a term used for tempering.
Drop Forging	An operation in which a metal shape is formed
	by forcing hot metal into impressions formed in
	solid blocks of hardened alloy steel, the
	forging dies. The dies are made in halves, one
	attached to the rising and falling block of the
	drop forge and the other to the stationary
	anvil. Drop forgings are widely used in the
	automotive industry for crankshafts, stub-axles,
	gears, etc.
Ductility	The property of metal which permits it to be
	reduced in cross sectional area without
	fracture. In a tensile test, ductile metals show
	considerable elongation eventually failing by
	necking, with consequent rapid increase in
	local stresses.
Dye Penetrant Inspection	A method for detecting surface porosity or
	cracks in metal. The part to be inspected is
	cleaned and coated with a dye which
	penetrates any flaws that may be present. The
	surface is wiped clean and coated with a white
	powder. The powder absorbs the dye held in
	the defects indicating their location.
Elastic Limit	The maximum stress that can be applied to a
	metal without producing permanent deformation.
	When external forces act upon a material they
	tend to form internal stresses within it which
	cause deformation. If the stresses are not too
	great the material will return to its original shape
	and dimension when the external stress is
	removed.
Elasticity	The property which enables a material to return
	to its original shape and dimension.
Electrical Steels	Steels which are characterised by their magnetic
	properties and are intended for the manufacture
	of electrical circuits. They are supplied in the
	form of cold rolled sheet or strip, generally less
	than 2mm thick and up to 1500mm wide. Grain
	orientated steels have preferential magnetic
	properties in the direction of rolling and non-
	grain orientated steels have similar magnetic
	properties both transversely and in the direction
	of rolling.
Electroslag Refining	A specialised steel making process in which a
	rolled or a cast ingot in the form of an electrode
	is remelted in a water cooled copper mold. The
	melting is activated by resistive heat generated
	in a conductive slag. The resulting product has a
	similar basic chemical composition to the original
	ingot, but is characterised by high purity and low
	inclusion content. Typical applications include
	high integrity components for the aerospace
	industry.
Elevated Temperature	A process of drawing steel bars at elevated
Drawing	temperatures (normally 250-300 deg C) which under
	optimum conditions produce steels that have
	higher tensile and yield strengths than those cold
	drawn with the same degree of reduction. The
	process is little used in the United Kingdom.
Elongation	A test to measure the ductility of steel. When a
	material is tested for tensile strength it elongates
	a certain amount before fracture takes place.
	The two pieces are placed together and the
	amount of extension is measured against marks
	made before starting the test and is expressed
	as a percentage of the original gauge length.
End Quench Test	More commonly referred to as Jominy Test it is
	used to determine the hardening ability of steel.
Equiaxed Crystals	Crystals, each of which has axes approximately
	equal in length. These are normally present in
	the centre of a steel ingot.
Equilibrium	A diagram constructed from thermal and other
	data showing the limits of composition and
	temperature within which the various
	constituents or phases of alloys are stable.
Etching	Treatment of a prepared metal surface with acid
	or other chemical reagent which, by differential
	attack, reveals the structure.
Eutectic	A mixture of two or more constituents which
	solidify simultaneously out of the liquid at a
	minimum freezing point.
Eutectoid	A mixture of two or more constituents which
	forms on cooling from a solid solution and
	transforms on heating at a constant minimum
	temperature. A eutectoid steel contains
	approximately 0.83% carbon.
Extrusion	The production of a section by forcing a billet to
	flow through a die. Often used for producing
	complex sections, the process is used with both
	hot and cold metal. Seamless tubes are
	produced by forcing a hot billet to flow through a
	die over a mandrel positioned centrally in the
	die.
F	Chemical symbol for Fluorine.
Face Centred Cubic	An arrangement of atoms in crystals in which the
Lattice	atomic centres are disposed in space in such a way
	that one atom is located at each of the corners of
	the cube and one at the centre of each face. Steel
	in the face-centred cubic arrangement is termed
	austenite.
Fatigue	The effect on metal of repeated cycles of stress.
	The insidious feature of fatigue failure is that there
	is no obvious warning, a crack forms without
	appreciable deformation of structure making it
	difficult to detect the presence of growing cracks.
	Fractures usually start from small nicks or scratches
	or fillets which cause a localised concentration of
	stress. Failure can be influenced by a number of
	factors including size, shape and design of the
	component, condition of the surface or operating
	environment.
Fatigue Limit	The maximum value of the applied alternating
	stress which a test piece can stand indefinitely.
Fatigue Testing	Fatigue tests are made with the object of
	determining the relationship between the stress
	range and the number of times it can be applied
	before causing failure. Testing machines are used
	for applying cyclically varying stresses and cover
	tension, compression, torsion and bending or a
	combination of these stresses.
Fe	Chemical symbol for Iron.
Ferrite	The solid solution of carbon in body-centered cubic
	iron, a constituent of carbon steels.
Ferritic Steel	A term usually applied to a group of stainless steels
	with a chromium content in the range of 12-18o
	and whose structure consists largely of ferrite. Such
	steels possess good ductility and are easily worked
	but do not respond to any hardening or tempering
	processes. Types of applications include
	automotive trim and architectural cladding.
Ferro Alloys	Alloys of iron with chromium, manganese, silicon,
	tungsten, molybdenum or vanadium. Used in
	steelmaking as a means of introducing these
	alloying elements into the cast or as deoxidisers.
Fettling	The removal of sand adhering to castings by
	hammering, tumbling or shot blasting.
Fin	In rolling mill practice a fin is a projection extending
	from the side of rolled sections. It causes
	considerable trouble and is the result of overfill.
	The fin, formed when the bar or shape is fed
	through one pass, is likely to be rolled back into the
	bar at the next pass. It is rarely encountered in
	modern rolling mills.
Flame Hardening	A surface hardening process in which heat is
	applied by a high temperature flame followed by
	quenching jets of water. It is usually applied to
	medium to large size components such as large
	gears, sprockets, slide ways of machine tools,
	bearing surfaces of shafts and axles, etc. Steels
	most suited have a carbon content within the range
	0.40-0.55%.
Flash	A fin that arises from metal in excess of that
	required to fill the final impression in a forging die
	and is exuded from the parting line between the
	dies; similarly it can arise at the mold joint in a
	casting.
Forging	A process of working metal to a finished shape by
	hammering or pressing and is primarily a "hot"
	operation. It is applied to the production of shapes
	either impossible or too costly to make by other
	methods or needing properties not obtainable by
	casting. Categories of forgings include Hammer,
	Press, Drop or Stamping.
Fracture	Fractures are often described by the appearance of
	the surface of the break in a piece of steel.
	Crystalline is bright and glittering, failure having
	developed along the cleavage planes of individual
	crystals and can be typical of brittle material. A
	silky fracture has a smooth dull grain indicative of
	ductile material such as a mild steel. In tensile
	testing fractures are described by shape, e.g. cup
	and cone.
Freecutting Steels	Steels which have had additions made to improve
	machinability. The most common additives are
	sulphur and lead, other elements used include
	tellurium, selenium and bismuth.
Ga	Chemical symbol for Gallium.
Galvanic Action	When iron and steel are subject to conditions of
	aqueous corrosion the incidence and rate at which
	the corrosion takes place will alter if the steel is
	coupled with other metals or alloys that are also
	exposed to the electrolyte. Copper, brass, bronze,
	lead and nickel are more "noble" and act as
	auxiliary cathodes to the steel and accelerate its
	anodic dissolution, that is, its corrosion.
	Magnesium, zinc and zinc-base alloy are nearly
	always less noble and tend to divert the attack
	from the steel to themselves. The galvanic
	relationship of various metals is an important factor
	affecting corrosion.
Gamma Iron	The allotropic form of iron existing between the
	temperature 910 deg C and 1400 deg C is known as
	Gamma Iron. It has a face centred cubic lattice and
	is non-magnetic. Gamma iron containing carbon or
	other elements in solution is known as austenite.
Gas Carburising	A heat treatment method used in the case-
	hardening of steel. Carbon is absorbed into the
	outer layers of the components by heating in a
	current of gas, rich in carbon compounds. The
	process is more versatile than some other methods
	as the depth of the case and the limiting carbon
	content of the case can be controlled by the
	composition of the atmosphere, the dew point and
	the temperature.
Gauge Length	Used in the mechanical testing of steel, it is the
	length marked on the parallel portion of a tensile
	test piece from which the elongation is measured.
Gauge Plate	An alloy tool steel supplied in flat and square
	section with the surfaces ground to close limits. It
	is also known as Ground Flat Stock and is used for
	the manufacturing of gauges, punches, dies, jigs,
	templates etc.
Ge	Chemical symbol for Germanium.
Grain Size Control	When a steel is austenitised by heating to above
	the critical range, time is required for the
	production of a homogeneous structure during
	which there is a tendency towards grain growth.
	Although subsequent hot and cold working affect
	the grain size, it is originally controlled at the steel
	making stage by the addition ofaluminium.
Grain Size Measurement	Grain size is normally quantified by a numbering
	system. Coarse 1-5 and fine 5-8. The number is
	derived from the formula N=2n-1 where n is the
	number of grains per square inch at a magnification
	of 100 diameters. Grain size has an important
	effect on physical properties. For service at
	ordinary temperatures it is generally considered
	that fine grained steels give a bettercombination of
	strength and toughness, whereas coarse grained
	steels have better machinability.
Graphitising	An annealing process applied to cast iron and
	steels with a high carbon and high silicon content
	by which the combined carbon is wholly or in part
	transformed to graphitic or free carbon.
Grey Iron	Also known as flake iron on account of all or part of
	the carbon content being in the form of graphite
	distributed through the metal as flakes.
Grinding	A machining process:- (a) to shape components
	that are too hard to be machined by conventional
	methods such as hardened tool steels and case or
	induction hardened components. (b) to obtain a
	high degree of dimensional accuracy and surface
	finish on a component.
Grinding Cracks	Cracks can arise from incorrect grinding and appear
	in the form of a network. They are caused by the
	generation of high heat and rapid cooling in the
	area of contact and they mostly occur when
	grinding fully hardened material such as tool steel.
H	Chemical symbol for Hydrogen.
Hard Metal Facing	A method of increasing the wear resistance of a metal
	by the deposition of a hard protective coating. Alloys
	such as Stellite or a metallic carbide are most often
	used for the coating.
Hard Metals	A group of materials more commonly known as
	cemented carbides. They consist of mixtures of one or
	more of the finely divided carbides of tungsten,
	titanium, tantalum and vanadium embedded in a
	matrix of cobalt or nickel by sintering. Widely used for
	cutting tools where for many applications they have
	replaced conventional high speed steels.
Hardenability	The property that determines the depth and
	distribution of hardness when steel is heated to a
	given temperature and then quenched (more precisely
	it may be defined as an inverse measure of the
	severity of cooling conditions necessary to produce on
	continuous cooling a martensitic structure in a
	previously austenitized steel i.e. to avoid
	transformations in the pearlitic and bainitic ranges).
	The lower the cooling rate to avoid these
	transformations, the greater the hardenability. The
	critical cooling rate is largely a function of the
	composition of the steel. In general the higher the
	carbon content, the greater the hardenability, while
	alloying elements such as nickel, chromium,
	manganese and molybdenum increase the depth of
	hardening for a given ruling section.
Hardening	Increasing the hardness of steel by heat treatment.
	This normally implies heating the steel to a required
	temperature and quenching in a suitable medium, e.g.
	oil or water.
Hardness	The hardness of steel is generally determined by
	testing its resistance to deformation. A number of
	methods are employed including Brinell, Vickers and
	Rockwell. The steel to be tested is indented by a
	hardened steel ball or diamond under a given load
	and the size of the impression is then measured. For
	steel there is an empirical relationship between
	hardness and tensile strength and the hardness
	number is often used as a guide to the tensile
	strength, e.g. 229 Brinell = 772N/mm2 (50 tons/sq.in).
Heat	In steel making terms this is often used to define the
	batch or cast produced from a single melting
	operation.
Heat Treatment	A process where solid steel or components
	manufactured from steel are subject to treatment by
	heating to obtain required properties, e.g. softening,
	normalising, stress relieving, hardening. Heating for
	the purpose of hot-working as in the case of rolling or
	forging is excluded from this definition.
High Speed Steel	The term `high speed steel' was derived from the fact
	that it is capable of cutting metal at a much higher
	rate than carbon tool steel and continues to cut and
	retain its hardness even when the point of the tool is
	heated to a low red temperature. Tungsten is the
	major alloying element but it is also combined with
	molybdenum, vanadium and cobalt in varying
	amounts. Although replaced by cemented carbides for
	many applications it is still widely used for the
	manufacture of taps, dies, twist drills, reamers, saw
	blades and other cutting tools.
Hooke's Law	This states that "within the limits of elasticity the
	strain produced by a stress of any one kind is
	proportional to the stress". The stress at which a
	material ceases to obey Hooke's Law is known as the
	limit of proportionality.
Hot Quenching	Cooling in a medium, the temperature of which is
	substantially higher than room temperature.
Hot Work	The rolling, forging or extruding of a metal at a
	temperature above its recrystallisation point.
Hydrogen	An undesirable impurity if present in steel and a cause
	of fine hairline cracks especially in alloy steels.
	Modern vacuum treatment eliminates this problem.
	Steel
Hyper-Eutectoid	A steel that contains more than 0.83% carbon which
	with appropriate heat treatment consists of pearlite
	and cementite.
Hypo-Eutectoid Steel	A steel that contains less than 0.83% carbon and
	which in annealed condition has a structure of ferrite
	and pearlite.
I	Chemical symbol for Iodine.
Impact Test	A test designed to give information on how a
	specimen of a known material will respond to a
	suddenly applied stress, e.g. shock. The test
	ascertains whether the material is tough or
	brittle. A notched test piece is normally
	employed and the two methods in general use
	are either the Izod or Charpy test. The result is
	usually reported as the energy in ft.lbs. or KJ.
	required to fracture the test piece.
In	Chemical symbol for Indium.
Inclusion Count	A method of assessing the number and size of
	non-metallic inclusions present in metal.
Inclusions	Usually non-metallic particles contained in
	metal. In steel they may consist of simple or
	complex oxides, sulphides, silicates and
	sometimes nitrides of iron, manganese, silicon,
	aluminium and other elements. In general they
	are detrimental to mechanical properties but
	much depends on the number, their size,
	shape and distribution.
Induction Hardening	A widely used process for the surface
	hardening of steel. The components are
	heated by means of an alternating magnetic
	field to a temperature within or above the
	transformation range followed by immediate
	quenching. The core of the component remains
	unaffected by the treatment and its physical
	properties are those of the bar from which it
	was machined, while the hardness of the case
	can be within the range 37/58 Rc. Carbon and
	alloy steels with a carbon content in the range
	0.40/0.45% are most suitable for this process.
Ingot	The mass of metal that results from casting
	molten steel into a mold. An ingot is usually
	rectangular in shape and is subsequently rolled
	into blooms and billets for rods, bars and
	sections and slabs for plates, sheet and strip.
	With the increasing use of the continuous
	casting process the ingot route is less used as
	the molten steel is now directly cast into a
	bloom or billet.
Ingot Mold	The receptacle into which molten steel is
	poured to form an ingot. After solidification the
	steel is suitable for subsequent working, i.e.
	rolling or forging.
Intercrystalline Corrosion	Chromium-nickel austenitic stainless steels are
	prone to this form of corrosion when they are
	welded and subsequently in contact with
	certain types of corrosive media. When heated
	within a temperature range of 450-800 deg C
	precipitation of the chromium carbides takes
	place at the grain boundaries in the area of the
	weld and these areas no longer have the
	protection of the chromium on the peripheries
	of the grains. This type of corrosion is also
	known as Weld Decay and Intergranular
	Corrosion. The most common way to avoid the
	problem is to select a grade of steel that is
	very low in carbon i.e. 0.03% or less, or one
	that is stabilised with niobium or titanium.
Interrupted Quenching	Rapid cooling to a selected temperature by
	quenching in a suitable medium, usually molten
	salt, holding at the temperature for an
	appropriate time and then cooling to room
	temperature. This process is used to minimise
	the risk of distortion.
Iron	The term iron, as used in the chemical or
	scientific sense of the word, refers to the
	chemical element iron or pure iron and is the
	chief constituent of all commercial iron and
	steel.
Isothermal Annealing	Heating to and holding at a temperature above
	the transformation range, then cooling to and
	holding at a suitable temperature until the
	austenite to pearlite change is complete.
Isothermal Transformation	Also known as the Time Temperature
Curve	Transformation Curve. If a small piece of steel
	is heated sufficiently slowly for it to become
	austenitic and then plunged into a salt bath
	and held at a constant temperature below the
	upper critical point for a definite time followed
	by rapid quenching, it is possible by
	examination to determine the extent to which
	the transformation of the austenite has
	occurred. By taking a number of specimens of
	the same steel and treating them in the same
	way, but varying the holding temperature and
	time the behavior of the steel with time and
	temperature can be studied. The information
	obtained can be plotted as time-temperature
	transformation curves which is useful in heat
	treatment practice, particularly for
	martempering and austempering.
Izod Impact Test	A test specimen, usually of square crossed
	section is notched and held between a pair of
	jaws, to be broken by a swinging or falling
	weight. When the pendulum of the Izod testing
	machine is released it swings with a downward
	movement and when it reaches the vertical the
	hammer makes contact with the specimen
	which is broken by the force of the blow. The
	hammer continues its upward motion but the
	energy absorbed in breaking the test piece
	reduces its momentum. A graduated scale
	enables a reading to be taken of the energy
	used to fracture the test piece. To obtain a
	representative result the average of three tests
	is used and to ensure that the results conform
	to those of the steel specification the test
	specimens should meet the standard
	dimensions laid down in BS 131.
Jominy Test	A method for determining the hardenability of steel. The Jominy
	test is covered by BS 4437:1987. A standard test piece 25mm x
	100mm is heated to a pre-determined temperature and
	quenched by a jet of water sprayed onto one end. When the
	specimen is cold, hardness measurements are made at intervals
	along the test piece from the quenched end and the results are
	plotted on a standard chart from which is derived the
	hardenability curve. BS 970 contains hardenability curves for
	many of the steels in the Standard. Properly carried out, this
	test will illustrate the effect of mass upon a chosen steel when
	heat treated and indicate if the steel is of a shallow, medium or
	deep hardening type.
Joule	A unit of energy. One joule is equal to the energy expended in
	one second by one ampere against the resistance of one ohm.
	In the mechanical testing of steel it is the unit used in the
	Charpy V notch impact test.
K	Chemical symbol for potassium.
	A method of producing steel from molten iron, using
Kaldo Process	an inclined rotating converter and a water cooled
	oxygen lance inserted through the converter mouth.
	Originating in Sweden, this process is no longer in use
	in the UK.
Killed Steel	The term indicates that the steel has been completely
	deoxidised by the addition of an agent such as silicon
	or aluminium, before casting, so that there is
	practically no evolution of gas during solidification.
	Killed steels are characterised by a high degree of
	chemical homogeneity and freedom from porosity.
Knoop Hardness Test	A micro hardness test in which an elongated
	pyramidical diamond is pressed into the surface.
La	Chemical symbol for Lanthanum.
Lap	A defect appearing as a seam on a rolled bar. Laps
	are rolled over pieces of material that arise when a
	bar is given a pass through the rolls after a sharp
	overfill or fin has been formed, causing the
	protrusion to be rolled into the surface of the
	product. The presence of oxides usually prevents
	the lap welding to the original bar surface, so that
	in subsequent cold working it is carried through as
	a longitudinal crack.
L-D Process	An oxygen steel making process named after the
	towns in Austria, Linz and Donawitz, where it was
	first developed. It is a modified Bessemer process,
	steel is produced in a solid bottom converter by
	injection of oxygen into the molten iron bath from a
	water cooled lance inserted through the converter
	mouth. Present day BOS (basic oxygen
	steelmaking) plants are developments of the L-D
	Process.
Leaded Steels	When added to steel, lead does not go into
	solution but exists in a very finely divided state
	along the grain boundaries. It greatly assists
	machinability as it acts as a lubricant between the
	steel and the tool face. Lead is normally added in
	amounts between 0.15-0.35% and when combined
	with similar amounts of sulphur, optimum
	machinability is attained as in such steel as BS 970
	230M07 Pb.
Li	Chemical symbol for Lithium.
Limiting Range of	The greatest range of stress that a metal can
Stress	withstand for an indefinite number of cycles without
	failure. If exceeded, the metal fractures after a
	certain number of cycles, which decrease as the
	range of stress increases.
Limiting Ruling Section	The maximum diameter of cross section of a bar or
	component in which certain specified mechanical
	properties are achieved after heat treatment.
Limits	A term used to determine a minimum and
	maximum. In a mechanism, it should denote the
	minimum and maximum sizes for each part,
	between which the parts will function properly in
	conjunction with each other and outside of which
	they will not. The words "limits" and "tolerances"
	are often interchanged, "tolerance" represents the
	difference between the minimum and maximum
	limits.
Limits of Proportionality	The stress (load divided by original area of cross
	section of the test piece) at which the strain
	(elongation per unit of gauge length) ceases to be
	proportional to the corresponding stress. It is
	usually determined from a load-elongation diagram,
	obtained by plotting extensometer readings and is
	the stress at which the load-elongation line ceases
	to be straight.
Liquid Carburising	A widely used method of case-hardening steel that
	eliminates scaling and the tendency to
	decarburisation and results in clean components.
	Sodium cyanide is the common media for this
	process, usually heated within the range of
	900-930 deg C. It is advisable to pre-heat the
	components in neutral salts to avoid a temperature
	drop resulting from immersing cold components into
	the cyanide. After carburising, either single quench
	hardening or refining and hardening and tempering
	is carried out.
Machinability	Simply defined as a measure of the ease with
	which a metal can be machined satisfactorily.
Macrostructure	The general crystalline structure of a metal and
	the distribution of impurities seen on a polished
	or etched surface by either the naked eye or
	under low magnification of less than x10.
Magnetic Crack Detection	The bar or component to be tested is
	magnetised by passing a heavy current through
	it or by making it the core of a coil through
	which a heavy current is passed. Cracks or
	inclusions cause the magnetic flux to break the
	surface forming free magnetic poles. When the
	component is sprayed with a suspension of
	finely divided magnetic particles they collect at
	the free poles to visibly show the presence of
	defects.
Malleability	It can be defined as the property of a metal to
	be deformed by compression without cracking or
	rupturing. The load may be applied slowly or
	suddenly and will determine whether the
	material will be suitable for forging or rolling into
	thin sheet.
Manganese	One of the most important constituents of steel
	in which it fulfils a number of functions. It acts
	as a mild de-oxidising agent. It combines with
	the sulphur present to form globular inclusions
	of Manganese Sulphide which are beneficial to
	machining. It increases tensile strength and the
	hardenability of steel.
Martempering	A heat treatment involving austenitisation
	followed by step quenching, at a rate fast
	enough to avoid the formation of ferrite, pearlite
	or bainite to a temperature slightly above the Ms
	point. Soaking must be long enough to avoid
	the formation of bainite. The advantage of
	martempering is the reduction of thermal
	stresses compared to normal quenching. This
	prevents cracking and minimises distortion.
Martensite	The hard constituent produced when steel is
	cooled from the hardening temperature at a
	speed greater than its critical cooling rate.
	Martensite is an acicular phase when seen in
	the microstructure of steel.
Mass Effect	A term used to signify the effect of size and
	shape during heat treatment, since it is the rate
	of cooling of a piece of steel which determines
	the properties resulting from the hardening and
	quenching process.
Matrix	The mass or principal constituent (e.g. iron in
	the case of steel) in which other constituents
	are embedded.
Maximum Stress	In the testing of the strength of steel a sample
	is machined into a standard test piece and is
	stretched in a tensile testing machine until it
	breaks. The results are expressed in N/mm2 and
	is the value of the maximum load reached in the
	test divided by the original cross sectional area
	of the specimen.
McQuaid EHN Grain Size	A method of assessing grain size. It consists of
Test	a test piece at 927 deg C for 8 hours by slow
	cooling and subsequent microscopical
	examination. The grain size is measured at x100
	magnification and compared to standard charts,
	the figures range from No. 1 -very coarse, to
	No. 8 - very fine.
Meehanite	A trade name applied to a certain type of cast
	iron.
Melting Point	The temperature at which a solid begins to
	liquefy.
Mg	Chemical symbol for Magnesium.
Micron	A unit of length equal to one millionth of a
	metre (0.001mm).
Microstructure	The structure that is observed when a polished
	and etched specimen of metal is viewed in an
	optical microscope at magnifications in range of
	approximately x25 to x1500.
Mn	Chemical symbol for Manganese.
Mo	Chemical symbol for Molybdenum.
Modulus of Elasticity	When a material is subjected to an external load
	it becomes distorted or strained. With metals,
	provided the loading is not too great, they return
	to their original dimensions when the load is
	removed, i.e. they are elastic. Within the limits
	of elasticity, the ratio of the linear stress to the
	linear strain is termed the modulus of elasticity
	or more commonly known as Young's Modulus.
Molybdenum	Its use as an alloying element in steel increases
	hardenability and in low alloy steels reduces the
	risk of temper brittleness. When added to
	stainless steels it increases their resistance to
	corrosion. It is also used in high speed steels.
N	Chemical symbol for Nitrogen.
Na	Chemical symbol for Sodium.
Nb	Chemical symbol for Niobium.
Ni	Chemical symbol for Nickel.
Nickel	One of the most widely used alloying elements in
	steel. In amounts 0.50% to 5.00% its use in alloy
	steels increases the toughness and tensile strength
	without detrimental effect on the ductility. Nickel
	also increases the hardenability, thus permitting the
	steel to be oil-hardened instead of water quenched.
	In larger quantities, 8.00% and upwards, nickel is
	the constituent, together with chromium, of many
	corrosion resistant and stainless austenitic steels.
Niobium	Also known as columbium. Niobium is a strong
	carbide forming element which is added to certain
	18/8% chromium-nickel stainless steels as a
	stabiliser to prevent inter-granular corrosion arising
	from welding.
Nitriding	A case hardening process that depends on the
	absorption of nitrogen into the steel. All machining,
	stress relieving, as well as hardening and tempering
	are normally carried out before nitriding. The parts
	are heated in a special container through which
	ammonia gas is allowed to pass. The ammonia splits
	into hydrogen and nitrogen and the nitrogen reacts
	with the steel penetrating the surface to form
	nitrides. Nitriding steels offer many advantages: a
	much higher surface hardness is obtainable when
	compared with case-hardening steels; they are
	extremely resistant to abrasion and have a high
	fatigue strength.
Nitrogen	Nitrogen is a gas that forms approximately 79% by
	volume or 77% by weight of the atmosphere. It can
	combine with many metals to form nitrides and is
	thus applied to the case-hardening of steel, the
	usual source for this purpose being ammonia.
Noble Metals	Metals such as gold, silver and platinum which are
	resistant to corrosion by all but the most powerful
	acids.
Non Destructive	Those forms of testing that do not result in
Testing	permanent damage or deformation to the part being
	tested. Typical examples are magnetic crack
	detection, ultrasonic inspection, X-Ray inspection
	and gamma radiography.
Non Magnetic Steels	Austenitic steels such as the 14% manganese steels
	and the 303 type 18/8% chromium-nickel stainless
	steels.
Normalising	A heat treatment process that has the object of
	relieving internal stresses, refining the grain size and
	improving the mechanical properties. The steel is
	heated to 800-900 deg C according to analysis, held at
	temperature to allow a full soak and cooled in still
	air.
Notched Bar Test	A test to determine the resistance of a material to a
	suddenly applied stress, i.e. shock. A notched test
	piece is employed in an Izod or Charpy machine and
	the results are recorded in ft.lbs. or Joules.
O	Chemical symbol for Oxygen.
Occlusion	A term applied, in the case of metals, to the
	absorption or entrapment of gases.
Oil Hardening Steel	Used to describe tool or alloy steels where oil is
	used as the quenching medium in the hardening
	process.
Open Hearth Furnace	Developed in the middle of the last century, the
	open hearth or Siemens-Martins process, as it is
	known, accounted for a major proportion of UK steel
	production until the early 1970's. For economic and
	quality reasons it has been replaced by the Electric
	Arc Furnace and the Basic Oxygen Steelmaking
	process. There are no open hearth furnaces in use
	in Britain today but they are still in use in Russia and
	Eastern Europe.
Orange Peel Effect	An effect that arises on the surface of steel sheets
	when they are stretched beyond their elastic limit.
Ore	An ore is a material that contains a metal in such
	quantities that it can be mined and worked
	commercially to extract that metal. The metal is
	usually contained in chemical combination with some
	other element in addition to various impurities.
Os	Chemical symbol for Osmium.
Overheating	Failure of tools and components in heat treatment
	can arise through overheating. This may be caused
	due to quenching from a temperature too high for
	the type of steel involved. Overheating is evidenced
	by cracking, grain-coarseness, erratic surface
	hardness and pitting.
Oxidation	A common form of chemical reaction which is the
	combining of oxygen with various elements and
	compounds. The corrosion of metals is a form of
	oxidation, rust on iron for example is iron oxide.
Oxy-Acetylene Welding	A process for joining two pieces of metal in which
	the required high temperature is obtained by the
	combustion of acetylene gas and oxygen. The gases
	are thoroughly mixed in the nozzle or tip of the
	welding torch to ensure perfect combustion. The
	weld may be formed directly between two adjoining
	surfaces, but usually metal from a welding rod is
	fused in between the surfaces of the joint.
Oxygen	Oxygen is one of the chief constituents of the
	atmosphere of which it forms approximately one
	fifth. It is odorless and invisible. Although oxygen
	itself does not burn it is extremely efficient in
	supporting combustion, nearly all other chemical
	elements combine with it under evolution of heat. It
	has many uses in industry and is essential to the
	BOS (Basic Oxygen Steelmaking Process).
P	Chemical symbol for Phosphorus.
Parkerising	A chemical treatment applied to ferrous metals to
	improve their corrosion resistance. The process is based
	on a manganese phosphate solution which produces a
	fairly thick coating. This can subsequently be painted or
	impregnated with oil. Patenting A heat treatment process
	often applied to high carbon wire. The steel is heated to
	a suitable temperature well above the transformation
	range, followed by cooling in air or a bath of molten lead
	or salt. A structure is produced suitable for subsequent
	cold drawing and which will give the desired mechanical
	properties in the finished state.
Pd	Chemical symbol for Palladium.
Pearlite	A lamellar constituent of steel consisting of alternate
	layers of ferrite (alpha-iron) and cementite (iron Carbide
	Fe3C) and is formed on cooling austenite at 723 deg C. This
	produces a tough structure and is responsible for the
	mechanical properties of unhardened steel.
Ph	Chemical symbol for Lead.
pH Value	A method of expressing differences in the acidity or
	alkalinity of a solution. A figure of 7 is regarded as
	neutral, figures below this indicate the decree of acidity
	and above alkalinity.
Phosphorus	An element that forms 0.12% of the earth's crust, chiefly
	in the form of phosphates. Its presence in steel is usually
	regarded as an undesirable impurity due to its embrittling
	effect, for this reason its content in most steels is limited
	to a maximum of 0.050%.
Pickling	A process to chemically remove scale or oxide from steel
	to obtain a clean surface. When applied to bars or coils
	prior to bright drawing, the steel is immersed in a bath of
	dilute sulphuric acid heated to a temperature of around
	80 deg C. An inhibitor is added to prevent attack and pitting
	of the cleaned metal. After pickling, a washing process
	takes place followed by immersion in a lime-water bath to
	neutralise any remaining acid. For environmental reasons
	shot blasting has largely replaced pickling.
Pig Iron	The product of the blast furnace. The term was derived
	from the method of casting the bars of the pig iron in
	depressions or molds formed in the sand floor adjacent
	to the furnace. These were connected to a runner
	(known as a sow) and when filled with metal the runner
	and the numerous smaller molds were supposed to
	resemble a litter of suckling pigs, hence the term pig
	iron.
Pinch Pass	A term applied when, after annealing, sheet or strip is
	lightly rolled with the object of preventing stretcher lines
	or kinks on subsequent cold working.
Pipe	A defect that arises during the solidification of steel in
	the ingot mold. As steel contracts on solidification a
	central cavity forms in the upper portion of the ingot, if
	this is not completely removed before rolling into bars a
	central defect known as "pipe" results. The risk of piping
	is considerably reduced on continuously cast steel due to
	molten steel being available to fill any shrinkage cavity.
Poisson's Ratio	If a square bar is stressed in a testing machine in the
	direction of its length so that the length increases, there
	is a contraction in each opposite direction, which
	produces a decrease in the thickness of the bar. The
	ratio between the contraction at right angles to a stress
	and the direct extension is called the Poisson's ratio. Its
	value in steel is in the order of 0.28.
Pot Quenching	Quenching carburised parts directly from the carburising
	pot or box.
Powder Metallurgy	A method of producing components by pressing or
	molding metal powders which may be simultaneously or
	subsequently heated to produce a coherent mass.
Pre-Heating	Used in the hardening process. Tools are pre-heated
	before heating to the final temperature, this is
	particularly important in tools of complex shape to
	prevent distortion or cracking. Pre-heating reduces the
	time of exposure to the hardening temperature and helps
	to minimise scaling and decarburisation.
Projection Welding	A welding process that uses small projections on one or
	both components of the weld to localise the heat and
	pressure, the projections collapse when the weld is
	made.
Proof Stress	The stress that will cause a specified small, permanent
	extension of a tensile test piece. Commonly the stress to
	produce 0.2% extension is quoted in N/mm2 for steel.
	This value approximates to the yield stress in materials
	not exhibiting a definite yield point.
Quenching	Rapid cooling from a high temperature by immersion in a
	liquid bath of oil or water. Molten salts may also be used.
Quenching Crack	A fracture, often termed a hardening crack, which arises
	from thermal stresses induced during rapid cooling.
Ra	Chemical symbol for Radium.
Radiography	A method of non-destructive testing. Internal
	examination of a metallic structure or component
	is carried out by exposing it to a beam of X-Ray
	or gamma radiation. Internal defects can be
	seen on a screen or recorded on film.
Rb	Chemical symbol for Rubidium.
Re	Chemical symbol for Rhenium.
Re-crystallisation	The re-arrangement of crystals in cold worked
	metal brought about by heating so that the
	deformed crystals are absorbed by newly-formed
	crystals and the effects of work hardening are
	removed. Also occurs when steel is heated
	through the transformation range and when steel
	is hot worked.
Red Hardness	A term sometimes associated with high speed
	steel because it has the property of retaining
	sufficient hardness for cutting metals even when
	heated to a temperature high enough to cause a
	dull redness. The tungsten content has a
	significant influence on this property.
Reduction of area	The percentage decrease in the cross-sectional
	area of a tensile test piece caused by wasting or
	necking of the specimen. It is expressed as a
	percentage of the original area of the test piece
	and is a measure of ductility.
Refining	(a) The removal of impurities and metallic oxides
	from the molten bath by the reaction of the slag
	and other additions. (b) A heat treatment
	process with the object of refining or making the
	grain size of the steel uniform.
Residual Stress	The stress which exists in an elastic solid body
	in the absence of, or in addition to, the stresses
	caused by an external load. Such stresses can
	arise from deformation during cold working such
	as cold drawing or stamping, in welding from
	weld metal shrinkage, and in changes in volume
	due to thermal expansion.
Rh	Chemical symbol for Rhodium.
Rockwell Hardness Testing	A method for testing the hardness of metals by
	determining the depth of penetration of a steel
	ball or a diamond sphero-conical indentor. The
	value is read from a dial and is an arbitrary
	number related to the depth of penetration. For
	testing hard steels, a sphero-conical diamond is
	used with a 150 kg load, the result is read from
	the black scale on the dial and is prefixed with
	the letter C. A hardened tool steel would
	typically give a reading of 62Rc. For softer
	metals Scale B is used with a 1/16" diameter
	steel ball and a standard load of 100 kgs.
Rolling	The process of shaping metal by passing it
	between rolls revolving at the same peripheral
	speed and in opposite directions. In steel there
	are a number of different types of rolling mill for
	processing the ingot to its finished shape. These
	are variously known as Cogging mills, Slabbing
	mills, Billet mills, Bar mills and Strip mills, which
	produce plate, sections, bars, sheet and strip.
	Cold rolling of previously hot rolled strip is
	carried out to produce strip that is accurate to
	size and with a smooth bright polished surface.
Rolling Lap	A fault arising from the overfilling or mis-
	alignment of rolls, the result is a bulge on the
	bar which is rolled into the metal and is lapped
	over. It remains throughout subsequent working
	and appears as a longitudinal crack.
Ru	Chemical symbol for Ruthenium.
Ruling Section	More accurately termed limiting ruling section.
	One of the most important factors associated
	with the choice of steel for a given purpose is to
	ensure that the desired mechanical properties
	are obtained throughout the section when the
	material has been heat treated. The limiting
	ruling section determines the maximum diameter
	or cross-section of a bar or component in which
	the specified properties can be achieved by a
	given heat treatment. The analysis of the steel
	also has an important bearing on this.
S	Chemical symbol for Sulphur.
Salt Bath	A method of heating steel using a bath of molten salts.
	Salt baths give uniform heating and prevent oxidation,
	they are used for hardening, tempering or quenching. The
	type of salt used depends on the temperature range
	required. For hardening, sodium cyanide, sodium
	carbonate and sodium chloride are in common use.
Sb	Chemical symbol for Antimony.
Scale	The oxidised surface of steel produced during hot working,
	as in rolling, and by exposure to air or steam at elevated
	temperature.
Scarfing	Also termed deseaming. It is a process for burning out
	defective areas on the surface of ingots or semi-finished
	products such as billets so that the product is suitable for
	subsequent rolling or forging.
Scrap	It forms the basic raw material for making steel by the
	electric arc process. Steel offers ecological advantages as
	it can be recycled enabling the discarded car of today to
	appear as part of a new model tomorrow. Scrap is sorted
	and graded before use and the necessary elements are
	added during the steel making process to achieve the
	desired specifications.
Se	Chemical symbol for Selenium. Seams A surface defect
	caused during the steel making process. Seams are
	generally formed from blow holes in the ingot, non metallic
	inclusions, or stresses arising during the solidification
	stage. They appear as longitudinal discontinuities in the
	bar.
Secondary
Hardness	An increase in hardness which sometimes occurs when
	hardened steel is re-heated. It can be caused by the
	transformation of retained austenite to martensite or by
	the precipitation of alloy carbides.
Segregation	A term applied to the concentration and partial separation
	of one or more elements from solution during solidification
	of liquid steel in an ingot mold. Sulphur and phosphorus
	tend to segregate to a greater extent than other elements
	which can have a particular adverse effect on machinability
	in high sulphur free-cutting steels. Modern steel making
	and continuous casting have largely overcome this
	problem.
Selenium	An element that closely resembles sulphur in its properties.
	The main use in steel is as a freecutting additive but due
	to high cost its use is limited to stainless steel. One of the
	benefits being the ability to obtain a very good surface
	finish on machined components.
SG Iron	An abbreviation for Spheroidal Graphite Cast Iron. As the
	name implies, graphite is present in spheroidal form
	instead of flakes and compared with Grey Cast Iron it has
	higher mechanical strength, ductility and increased shock
	resistance.
Shearing Test	The test applied to metal to determine the stress required
	to fracture it across its section.
Sherardizing	A process developed in Britain in 1904 by Sherard
	Cowper-Coles. It is a method of producing a protective
	zinc coating on iron and steel products.
Shore	An instrument that measures the hardness of a sample in
Scleroscope	arbitrary terms of elasticity. A diamond tipped hammer is
	allowed to fall freely down a graduated glass tube on to
	the sample under test. The hardness is measured by the
	height of the rebound. In another form the rebounding
	hammer actuates the pointer of a scale so that the height
	of the rebound is recorded.
Spinning	The formation of sheet metal blanks into hollow circular
	shapes. This is carried out on a lathe with forming tools
	which service to press and shape the metal. Annealing
	may be needed during and/or after the operation to
	remove the effects of work hardening.
Spot Welding	A process for joining steel sheets. The two parts are held
	between electrodes and the heat generated at the
	interface between the sheets causes local welding when
	pressure is applied.
Spring Steel	The steels used for spring making depend on the
	application and type of spring. They range from plain
	carbon grades in the range 0.5% to 1.00% C. to
	Chromium, Chromium-Vanadium,
	Nickel-Chromium-Molybdenum, Silico-Manganese and
	Silicon-Manganese-Chromium-Molybdenum types. Full
	details can be found in BS5770.
Stabilisation	A term applied to a number of processes: a) A type of heat
	treatment to relieve internal stresses: b) The retarding or
	prevention of a particular reaction by the addition of a
	stabilising element; c) A thermal and/or mechanical
	treatment given to magnetic material in order to increase
	the permanency of its magnetic properties or condition.
Stainless Steel	Can be defined as a group of corrosion resisting steels
	containing a minimum 10% chromium and in which varying
	amounts of nickel, molybdenum, titanium, niobium as well
	as other elements may be present. An Englishman, Harry
	Brearley, is generally acknowledged to be the pioneer who
	developed stainless steels for commercial use.
Steel	Generally defined as a metallic product whose principal
	element is iron and where the carbon content is not more
	than 2%. (The presence of large quantities of carbide
	forming elements may modify the upper limit of the carbon
	content.)
Strain Ageing	The gradual changes in physical and mechanical
	properties, in particular hardness and tensile strength,
	which takes place following cold rolling or deformation. At
	atmospheric temperatures, this may take place over a
	number of weeks but can be accelerated by heating.
Strain Hardening	The loss of ductility and gain in hardness resulting from
	strain ageing.
Stress Relieving	A heat treatment including heating and soaking at a
	suitable temperature (e.g. 600-650 deg C) followed by cooling
	at an appropriate rate in order to reduce internal stresses
	without substantially modifying the steel's structure. This
	treatment may be used to relieve stresses induced by
	machining, quenching, welding or cold working.
Stress Strain	A graph in which stress (load divided by the original cross
Curve	sectional area of the test piece) is plotted against strain
	(the extension divided by the length over which it is
	measured).
Sub-Critical	Heating to, and holding at, some point below the critical
Annealing	temperature. Subsequent cooling may be in air. This form
	of heat treatment has a variety of uses depending on the
	temperature and specification of the steel, its purpose is
	often to soften the material.
Sub-zero	A low temperature treatment carried out after quenching
Treatment	on hardened steel to transform the retained austenite into
	martensite. It involves immersing the component in a bath
	of solid carbon dioxide at a temperature of minus 70-80 deg C.
Sulphur	Generally regarded as an impurity in steel as it can have
	detrimental effects on strength, ductility and weldability as
	well as producing hot and cold shortness. Its content in
	most steels is limited to a maximum of 0.050%. Sulphur is
	beneficial to machining and is added to freecutting steels
	in amounts up to 0.35% with the manganese content
	increased to overcome any detrimental effects.
Surface	A method of hardening the surface of steel to increase its
Hardening	wear resistance. Depending on the analysis of the steel,
	the following treatments can be employed:
	Case-hardening, Nitriding, induction hardening, Flame
	hardening.
Swaging	A method of forming or reducing steel or other metals to a
	desired shape by a series of blows rapidly applied by dies
	or hammers. The process is applied to wires, rods and
	tubes and can be used for a variety of pointing, tapering,
	sizing and reducing operations.
Swarf	The particles of metal arising from machining or grinding
	operations, much of it finds its way to the steel maker for
	remelting.
Ta	Chemical symbol for Tantalum.
Tantalum	A rare metal of silver white color having
	excellent corrosion resistance and a high
	melting point. It is widely used for chemical
	process equipment and specialised
	aero-space and nuclear applications.
Te	Chemical symbol for Tellurium.
Tellurium	Its main use in the steel industry is as an
	additive in leadbearing freecutting steels to
	further improve their machinability. Its
	presence in the steel is either within the
	manganese sulphide particles, where it is
	partially soluble, or as particles combined
	with lead or manganese. For certain
	applications it offers significant improvements
	in machinability but the added cost is a factor
	that should be taken into account.
Temper	A term to which a number of definitions can
	be applied. These include: a) The operation
	of tempering; b) The degree of hardness left
	in a steel bar after quenching and tempering;
	c) The grading of the hardness of low carbon
	cold rolled strip, e.g. Hard, Half Hard,
	Quarter Hard, Skin Passed, Soft; d) An
	indication of the amount of carbon present in
	a tool steel, e.g. razor temper, file temper,
	die temper, etc.
Temper Brittleness	The loss in impact resistance that is present
	in some low and medium carbon alloy steels
	when tempered in the range of 350 deg C -
	600 deg C. It is revealed by the notched bar
	impact test but not the tensile test.
Temper Colors	Before the use of instruments such as
	pyrometers, colors were used to judge
	temperatures when hardening and tempering.
	For example, on carbon tool steel where the
	tempering range may typically be from 200 deg C
	to 350 deg C, the colors change with the rise in
	temperature giving Light Straw at around
	210 deg C, Purple at 275 deg C, and Grey at 330 deg C.
	The practice still continues in workshops
	where controlled heat treatment facilities are
	not available.
Temper Rolling	A light pass given to annealed cold rolled
	strip to prevent the formation of kinks and
	stretcher strain markings on subsequent cold
	working. Also termed Pinch pass and Skin
	pass.
Tempering	A heat treatment applied to ferrous products
	after hardening. It consists of heating the
	steel to some temperature below the
	transformation range and holding for a
	suitable time at the temperature, followed by
	cooling at a suitable rate. The object of
	tempering is to decrease hardness and
	increase toughness to produce the desired
	combination of mechanical properties.
Tensile Strength	The maximum load applied in breaking a
	tensile test piece divided by the original
	cross-sectional area of the test piece.
	Originally quoted as tons/sq.in. it is now
	measured as Newtons/sq.mm. Also termed
	Maximum Stress and Ultimate Tensile Stress.
Tensile Test	A standard test piece is gripped at either end
	by suitable apparatus in a testing machine
	which slowly exerts an axial pull so that the
	steel is stretched until it breaks. The test
	provides information on proof stress, yield
	point, tensile strength, elongation and
	reduction of area.
Thomas Process	The Continental name for the basic Bessemer
	steel making process, now superseded by
	modern day BOS plants.
Ti	Chemical symbol for Titanium.
Time Temperature	An isothermal transformation diagram
Transformation Curve	showing the relationship between
	temperature and the time taken for the
	decomposition of austenite when the
	transformation occurs at constant
	temperature.
Tin	When present in steel it is an undesirable
	impurity which gives rise to temper
	brittleness. When used as a coating on steel,
	it has a good resistance to corrosion for many
	applications.
Titanium	Small amounts added to steel contribute to
	its soundness and give a finer grain size. In
	austenitic stainless steels it acts as a carbide
	stabiliser and is used to prevent
	intercrystalline corrosion, commonly termed
	"weld decay". Titanium carbide is also used
	with tungsten carbide in the manufacture of
	hard metal tools.
Tolerances	The amount of variation permitted on
	dimensions or surfaces. The tolerance is
	equal to the difference between the maximum
	and minimum limits of any specified
	dimension.
Tool Steel	A generic term applied to a wide range of
	steels, both plain carbon and alloy. It
	includes steels suitable for various types of
	cutting tools, press tools, hot and cold
	heading dies, molds for plastics and die-
	casting, extrusion tools, hand tools, etc.
Torsional Strength	The resistance of a bar to twisting. Closely
	related to its shear strength.
Toughness	The ability of a metal to rapidly distribute
	within itself both the stress and strain caused
	by a suddenly applied load, or more simply
	expressed, the ability of a material to
	withstand shock loading. It is the exact
	opposite of "brittleness" which carries the
	implication of sudden failure. A brittle
	material has little resistance to failure once
	the elastic limit has been reached.
Transformation Range	The temperature range within which austenite
	forms and ferrite or carbide progressively
	dissolves while ferrous alloys are being
	heated. Also the temperature range within
	which austenite decomposes to form ferrite
	and carbide on cooling.
Transformation Temperature	The temperature at which a change in phase
	occurs or the limiting temperature of a
	transformation range. These critical points
	are denoted by symbols, e.g. Ac1; the
	temperature at which austenite begins to
	form on heating. There are 12 principal
	temperatures to which symbols are applied.
Transition Temperature	The temperature at which a transition from
	ductile to brittle fracture takes place in steel.
	It is usually determined by making a series of
	Charpy impact tests at various temperatures,
	the transition temperature is usually taken as
	the point where 50% of the fracture is brittle.
Transverse Strength	A measurement of strength when the load is
	applied across the longitudinal flow of the
	grain of a metal. Certain impurities such as
	sulphur have a detrimental effect on the
	transverse strength. This can be minimised by
	the inclusion modification process.
Transverse Test	A test taken at right angles to the principal
	direction of rolling or forging.
TTT Curve	An abbreviation of Time Temperature
	Transformation Curve.
Tufftriding	A form of surface hardening, the process
	involves nitrogen but does not achieve the
	hardness of conventional nitriding.
Tungsten	When used as an alloying element it
	increases the strength of steel at normal and
	elevated temperatures. Its "red hardness"
	value makes it suitable for cutting tools as it
	enables the tool edge to be maintained at
	high temperatures. In conjunction with other
	alloying elements it finds applications in heat
	resisting and other severe service conditions.
U	Chemical symbol for Uranium.
Ultimate Analysis	In chemistry, this is a quantitative analysis in which
	percentages of all elements in the substance are
	determined.
Ultimate Tensile
Strength	The highest load applied in breaking a tensile test
	piece divided by the original cross-sectional area of
	the test piece.
Ultrasonic Inspection	A means of locating defects in steel. When acoustic
	energy in the ultrasonic range is passed through
	steel, the sound waves tend to travel in straight
	lines, rather than diffusing in all directions as they
	do in the audible range. If there is a defect in the
	path of the beam it will cause a reflection of some
	of the energy, depleting the energy transmitted.
	This casts an acoustic shadow which can be
	monitored by a detector placed opposite the
	transducer or energy source. If the acoustic energy
	is introduced as a very short burst, then the
	reflected energy coming back to the originating
	transducer can also be used to show the size and
	depth of the defect. Ultrasonic techniques can be
	used to detect deeply located defects or those
	contained in the surface layer. Skill and experience
	are required in interpreting the results portrayed on
	the cathode ray tube.
Unkilled Steel	Steel which has been insufficiently deoxidised and
	evolves gas during solidification with the formation
	of blow-holes.
Upsetting	Working a piece of steel so that its length is
	shortened and its cross-sectional area is increased.
	Its effect is to increase ductility in the radial and
	tangential directions.
Uranium	A white malleable metal which is softer than steel.
	Its specific gravity is 18.7, it melts at a temperature
	of 2400 deg C.
V	Chemical symbol for Vanadium.
Vacuum Arc
Remelting	A process used for producing advanced steels to the
	most demanding and critical specifications,
	particularly in such areas as aerospace applications.
	The steel is first produced to a very close analysis
	and the resulting ingot is slowly remelted in a
	Vacuum Arc Remelting furnace for up to 14 hours.
	Such steels are, by necessity, expensive to
	manufacture.
Vacuum Degassing	A ladle of molten metal is placed within a chamber
	which is then evacuated. This reduces the gas
	content, particularly hydrogen, as well as reducing
	non-metallic inclusions. Modern secondary steel
	making processes using Vacuum Arc Degassing units
	that include automated stirring and control of
	temperature and chemical analysis, ensure a
	consistent and high quality product.
Vanadium	Steels containing vanadium have a much finer grain
	structure than steels of similar composition without
	vanadium. It raises the temperature at which grain
	coarsening sets in and increases hardenability where
	it is in solution in the austenite prior to quenching. It
	also lessens softening on tempering and confers
	secondary hardness on high speed steels. Vanadium
	is used in nitriding, heat resisting, tool and spring
	steels in conjunction with other alloying elements.
Vickers Hardness Test	A method of determining the hardness of steel
	whereby a diamond pyramid is pressed into the
	polished surface of the specimen and the diagonals
	of the impression are measured with a microscope
	fitted with a micrometer eye piece. The rate of
	application and duration are automatically controlled
	and the load can be varied.
W	Chemical symbol for Tungsten, from wolfram.
Welding	The process of joining together two pieces of metal
	so that bonding accompanied by appreciable
	interatomic penetration takes place at their original
	boundary surfaces. The boundaries more or less
	disappear at the weld, and integrating crystals
	develop across them. Welding is carried out by the
	use of heat or pressure or both and with or without
	added metal. There are many types of welding
	including Metal Arc, Atomic Hydrogen, Submerged
	Arc, Resistance Butt, Flash, Spot, Stitch, Stud and
	Projection.
Whiskers	Thin hair-like growths on metal that are barely
	visible to the naked eye, they are stronger than the
	metals from which they are formed, probably
	because they are free from defects.
White Annealing	A heat treatment process carried out on pickled
	steel with the objective of eliminating the hydrogen
	that has entered the steel during the pickling
	operation and thus removing any tendency to
	hydrogen embrittlement.
Widmanstatten Structure	A microstructure resulting when steels are cooled
	at a critical rate from extremely high temperatures.
	It consists of ferrite and pearlite and has a
	cross-hatched appearance due to the ferrite having
	formed along certain crystallographic planes.
Wolfram	The alternative name for tungsten.
Woody Fracture	A fracture that is fibrous or woody in appearance
	due to the elongation of the individual grains. This
	may be accentuated by the presence of slag or by
	a banded structure. It is grey and dull and is
	characteristic of ductile but non-homogeneous
	material such as wrought iron.
Work Hardening	The increase in hardness and strength produced by
	cold plastic deformation or mechanical working.
Wrought Iron	A commercial iron that has little use today and has
	been replaced by mild steel. It was commonly
	produced by the puddling process. The
	temperatures employed in its production are too
	low to render it fluid, it is heated until it forms a
	pasty mass then it is squeezed or forged. The
	process does not lend itself to removal of
	impurities so it contains an appreciable quantity of
	slag. It will not respond to any heat treatment
	designed to increase the hardness or strength.
X-Ray Crystallography	X-ray photographs of metals are a means of providing
	information which in many cases cannot be obtained
	by microscopic methods. The lines produced by each
	element, or phase are characteristic, and their
	general pattern enables the crystalline structure to be
	identified. The scale of the pattern can be used to
	determine accurately the size of the unit cell and,
	therefore, the distance apart of the individual atoms.
	From the relative intensity of the lines it is possible to
	deduce the distribution throughout the unit cell, the
	various types of atoms in an alloy or the degree of
	preferred orientation in the material.
Yield Point	Can be defined as the point where a tensile test piece
	begins to extend permanently. If the load is reduced to
	zero, the test piece will not return to its original length.
Yield Strength	The stress at which general plastic elongation of the test
	piece takes place. This point is well defined in hardened
	and tempered or annealed structures but can be ill defined
	in "as drawn" structures.
Young's Modulus	Within the limits of elasticity, the ratio of the linear stress
	to the linear strain is termed the modulus of elasticity or
	Young's Modulus and may be written Young's Modulus, or
	E =(Stress/Strain) It is this property that determines how
	much a bar will sag under its own weight or under a
	loading when used as a beam within its limit of
	proportionality. For steel, Young's Modulus is of the order
	of 205000 N/mm2.
Zinc	Zinc is a metallic chemical element, it has a white color with a
	bluish tinge. It has a high resistance to atmospheric corrosion and
	a major use is as a protective coating for iron and steel sheet and
	wire. Galvanised sheets are a prime example. The melting point
	of zinc is 419 deg C.
Zirconium	Acts as a deoxidising element in steel and combines with sulphur.
Zn	Chemical symbol for Zinc.
Zr	Chemical symbol for Zirconium.