common metallurgical terms can be found in this section. Where appropriate
we have added external links to technical information located elsewhere on
melting furnace in to 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
||The cold rolling of steel strip hardens the
material. Although it can be used in this condition (Known as hard
bright), most strip requires annealing in order to soften it for further processes
such as forming. The softening process or annealing, takes place in a
furnace where the temperatures and the rates of heating and cooling
are carefully controlled. To avoid scaling it is necessary to
exclude oxygen from the furnace which is replaced with an atmosphere
containing nitrogen or hydrogen as the predominant gas.
||A trade name for a patented heat
treating process that consists of quenching a ferrous alloy from
temperature above the transformation ranges, in a medium having a rate of
heat abstraction sufficiently high to prevent the formation of
high-temperature transformation products and in maintaining the alloy,
until transformation is complete, at a temperature below that of pearlite
formations and above that of martensite formation.
||Steels containing high
percentages of certain alloying elements such as manganese and nickel.
These cannot be hardened by normal heat treatment, but do respond to work
Automatic Gauge control
||Using hydraulic roll force
systems, steelmakers have the ability to control precisely their steel
sheet's gauge (thickness) while it is travelling at more than 50 miles per
hour through the cold mill. Using feedback or feed-forward systems, a
computer's gap sensor adjusts the distance between the reduction rolls of
the mill 50-60 times per second. These adjustments prevent the processing of
any off-gauge steel sheet.
inside radius of a formed feature. The bend radius should be equal to, or
greater than, the material thickness. A small bend radius can create
fracturing at the bend due to the natural thinning that does occur at the
bend radius. Also called inside radius.
||These are carried out to ensure ductility is
sufficient to withstand the deformation during pressing and forming. A standard
size test piece is bent through a specific arc without fracturing.
cylindrical refractory lined furnace for the production of pig iron or hot
metal for direct conversion into steel.
Sheets - A method of coating sheets with a thin, even film of bluish-black
oxide, obtained by exposure to an atmosphere of dry steam or air, at a
temperature of about 1000 0øF., generally this is done during
box-annealing. (2) Bluing of tempered spring steel strip; an oxide film
blue in color produced by low temperature heating.
Symbol B)- Element No. 5 of the periodic system. Atomic weight 10.82. It
is gray in color, ignites at about 1112°F. and burns with a brilliant
green flame, but its melting point in a non-oxidizing atmosphere is about
4000°F. Boron is used in steel in minute quantities for one purpose only
- to increase the hardenability as in case hardening and to increase
strength and hardness penetration.
||Medium carbon steels (0.20-0.30% Carbon) to
which the element Boron has been added in the range 0.0005% to 0.005% to
||This involves impressing a hard metal
ball (often tungsten carbide) of a given diameter with a given load
into the steel surface. The hardness of the steel is calculated from the
depth of the indentation.
||An essential element of steel. Low carbon
enhances ductility, whilst higher carbon lowers ductility, increases
tensile strength, and the ability to further increase hardness as a result
of heat treatment.
||A case hardening process in which
steel components are heated in an atmosphere containing hydrogen and
||The process of hardening the
surface of steel to improve wear resistance whilst leaving the core
relatively soft. More information at the excellent
||A rolling mill where each of the
two working rolls of small diameter is supported by two or more back-up
||Creases or Ridges appearing in
sheets as parallel lines transverse to the direction of rolling and
generally extending across the width of the sheet.
||A process of impressing images or
characters of the die and punch onto a plane metal surface.
method of producing blooms, billets and slabs in long lengths using water
cooled moulds. The castings are continuously withdrawn through the bottom
of the caster whilst the teeming of the metal is proceeding. The need for
primary and intermediate mills and the storage and use of large
numbers of ingot moulds is eliminated.
|Removal of carbon from the outer
surface of iron or steel, usually by heating in an oxidizing or reducing
atmosphere. Water vapor, oxygen and carbon dioxide are strong
decarburizers. Reheating with adhering scale is also strongly
decarburizing in action.
||The process of cold working or
drawing sheet or strip metal blanks by means of dies on a press into
shames which are usually more or less cup-like in character involving
considerable plastic deformation of the metal. Deep-drawing quality sheet
or strip steel, ordered or sold on the basis of suitability for
||The removing of the scale which is a inherent
feature of hot rolled strip. Most commonly done by Pickling (removal with
acid) or occasionally by blasting.
|The property of metals that
enables them to be mechanically deformed when cold, without fracture. In
steel, ductility is usually measured by elongation and reduction of area
as determined in a tensile test.
||Wavy projections formed at the
opera end of a cup or shell in the course of deep drawing because of
differences in directional properties
property which enables material to return to its original shape and
||Also known as silicon
steels, this is a very low carbon steel (0.005% or lower), with silicon
between 0.05 and 3.5%. Addition of silicon increases the alloy's electrical
resistance, which inhibits the eddy currents and narrows the hysteresis loop
of the material, thus lowers the core losses. Silicon steel can be
manufactured either as grain oriented (GO), or grain non-oriented (GNO).
||Zinc plating process whereby the molecules on
the positively charged zinc anode attach to the negatively charged sheet
steel. The thickness of the zinc coating is readily controlled. By
increasing the electric charge or slowing the speed of the steel through the
plating area, the coating will thicken.
||A measure of ductility related to the
measurement of tensile strength and the percentage of elongation that
strip will withstand before fracturing.
|| Produced to enhance machinability by
the addition of elements such as sulphur or lead. Galvanneal is a
hot-dip zinc coating applied to steel. It is similar to hot-dip galvanizing
but is specifically designed for steel that will subsequently be painted,
such as the rocker panels and other corrosion sensitive areas on cars.
|Coating steel with zinc and tin
(principally zinc) for rustproofing purposes. Formerly for the purpose of
galvanizing, cut length steel sheets were passed singly through a bath of
the molten metal. Today’s galvanizing processing method consists of
uncoiling and passing the continuous length of successive coils either
through a molten bath of the metal termed Hot Dipped Galvanizing or by
continuously zinc coating the uncoiled sheet electrolytically - termed
||Average diameter of grains in the
metal under consideration, or alternatively, the number of grains per unit
area. Since increase in grain size is paralleled by lower ductility and
impact resistance, the question of general grain size is of great
significance. The addition of certain metals affects grain size, for
example vanadium and aluminum tend to give steel a fine grain. The ASTM
has set up a grain size standard for steels, and the McQuaid-Ehn Test has
been developed as a method of 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.
||Annealed and preground (to close
tolerances) tool steel flats in standard sizes ready for tool room use.
These are three common grades; water hardening, oil hardening and air
||Abbreviation for high strength low alloy.
These types of steel give improved tensile and yield strengths over
traditional grades whilst restricting the carbon content to enhance
formability and weldability. The production relies on close control of
structure by tightly controlled coiling temperatures and grain refining
elements (commonly, Niobium and Titanium) added during steelmaking.
||The property that determines the depth and
distribution of hardness after heating and quenching.
Hot dip galvanizing
The process of applying
a zinc coating to fabricated iron or steel material by immersing the
material in a bath consisting primarily of molten zinc. The simplicity of
the galvanizing process is a distinct advantage over other methods of
providing corrosion protection. The automotive industry depends heavily on
this process for the production of many components used in car manufacturing
designed to determine, the resistance of metal to breakage by impact,
usually by concentrating the applied stress to a notched specimen.
With modern steelmaking and continuous
annealing it is now possible to produce interstitial-free (IF) cold rolled
steels. These have a low strength and excellent ductility and formability.
If titanium is used alone as the stabilizing agent then the aim Ti content
is calculated from the formula: Ti = 4×%C + 3.42×%N + 1.5×%S + 0.02. If
niobium is also used then the aim Ti = 3.42×%N + 1.5×%S and Nb = 7.75×%C
A typical IF steel composition is 0.002%C,
0.01%Si, 0.15%Mn, 0.01%P, 0.01%S, 0.0025%N, 0.04%Al, 0.016%Nb, 0.025%Ti.
of impurities (usually oxides, sulfides, silicates, etc.) that are held
mechanically or are formed during the solidification or by subsequent
reaction within the solid metal.
process of hardening a ferrous alloy by heating it above the
transformation range by means of electrical induction, and then cooling as
term "killed" indicates that the steel has been sufficiently
deoxidized to quiet the molten metal when poured into the ingot mold. The
general practice is to use aluminum ferrosilicon or manganese as
deoxidizing agents. A properly killed steel is more uniform as to analysis
and is comparatively free from aging. However, for the same carbon and
manganese content Killed Steel is harder than Rimmed Steel. In general all
steels above 0.25% carbon are killed, also all forging grades, structural
steels from 0.15% to 0.25% carbon and some special steels
defect appearing in sheets or strips as a segregation or in layers. To
become divided, caused by gas pockets in the ingot.
||An important element within steel which
increases tensile strength and hardenability.
Modulus of Elasticity
Young's modulus (also known as the modulus of elasticity or elastic
modulus) is a measure of the
stiffness of a given material,
which is particularly suited for the nitriding process, that is, it will
form a very hard and adherent surface upon proper nitriding (heating in a
partially dissociated atmosphere of ammonia gas). Composition usually
.20-.40% carbon, .90-1.50% chromium, .15-1.00% molybdenum, and .85-1.20%
treatment applied to steel. Involves heating above the critical range
followed by cooling in still air. Is performed to refine the crystal
structure and eliminate internal stress.
process of hardening a ferrous alloy of suitable composition by heating
within or above the transformation range and quenching in oil.
- A surface roughening (defect) encountered in forming products from metal
stock that has a coarse grain size. It is due to uneven flow or to the
appearance of the overly large grains usually the result of annealing at
too high a temperature.
||The commonest method of descaling hot rolled
steel strip. It is a chemical process involving the passing of strip
through dilute acid. The acid is subsequently washed from the surface to
neutralise further reaction. Often the strip is then coated with oil to
protect the surface from oxidation.
||A light rolling operation to eliminate the
condition known as coil break which can be apparent in annealed strip, or
to produce the desired temper or surface finish. Usually the reduction is
between 1½ to 3%. More recently pinch passing is used to achieve tighter
gauge tolerances on hot rolled strip, in this instance the percentage
reduction may be greater.
symbol P) - Element No. 15 of the periodic system; atomic weight 30.98.
Non-metallic element occurring in at least three allotropic forms; melting
point 111°F.; boiling point 536°F.; specific gravity 1.82. In steels it
is usually undesirable with limits set in most specifications. However, it
is specified as an alloy in steel to prevent the sticking of light-gage
sheets; to a degree it strengthens low carbon steel; increases resistance
to corrosion, and improves machinability in free-cutting steels. In the
manufacture of Phosphor Bronze it is used as a deoxidizing agent.
stresses that are set up within a metal as the result of nonuniform
plastic deformation. This deformation may be caused by cold working or by
drastic gradients of temperature from quenching or welding.
steel in which incomplete deoxidation permits the metal to remain liquid
at the top of the ingot, resulting in the formation of a bottom and side
rim of considerable thickness. The rim is of somewhat purer composition
than the original metal poured. If the rimming action is stopped shortly
after pouring of the ingot is completed, the metal is known as capped
steel. Most steels below 0.15% carbon are rimmed steels. For the same
carbon and manganese content rimmed steel is softer than killed steel.
standard method for measuring the hardness of metals. The hardness is
expressed as a number related to the depth of residual penetration of a
steel ball or diamond cone ("brale") after a minor load of 10
kilograms has been applied to hold the penetrator in position. This
residual penetration is automatically registered on a dial when the major
load is removed from the penetrator. Various dial readings combined with
different major loads, give "scales" designated by letters
varying from "A" to "H"; the "B" and
"C" scales are most commonly in use.
edges, the final contours of which are produced by side or edging rolls.
The edge contours most commonly used are square corners, rounded corners
and rounded edge. Alternatively from hot rolled narrow strip, with natural
surface defect consisting of scale partially rolled into the surface of
sheet or strip metal through a series of staggered small rolls so as to
flatten the metal. This method is relatively ineffective in removing
defects such as buckles, wavy edges, corrugations, twists, etc., or from
steel in the higher hardness ranges.
Machine) - A cutting machine with sharpened circular blades or disc-like
cutters used for trimming edges and slitting sheet and foil. NOTE: Cutter
discs are also employed in producing circles from flat sheets but with
differently designed machines.
alloy, concentration of carbon or alloying elements at specific regions,
usually as a result of the primary crystallization of one phase with the
subsequent concentration of other elements in the remaining liquid.
||The oxidised surface of strip produced during
the hot rolling
Symbol Si) - Element No. 14 of the periodic system; atomic weight 28.06.
Extremely common element, the major component of all rocks and sands; its
chemical reactions, however, are those of a metalloid. Used in metallurgy
as a deoxidizing scavenger. Silicon is present, to some extent, is all
steels, and is deliberately added to the extent of approximately 4% for
electric sheets, extensively used in alternating current magnetic
circuits. Silicon cannot be electrodeposited.
known as Electrical Steel. See above.
||See Pinch passing
of steel, resulting from the tempering of martensite. In a truly sorbitic
structure, the cementite is completely dispersed in the matrix. The trend
is to call this structure tempered martensite.
||An annealing process that generally involves
the heating and more prolonged soaking of strip at a temperature around or
just below the transformation point to globularise the carbides. This
increases ductility in high carbon steels.
||The generic term for steels used for spring
making. Typically they range from 0.50% carbon through to 1.00% and
include alloy grades containing chromium, Nickle and Molybdenum.
process of prolonged heating and slow cooling of steel which will convert
the carbide content into rounded or spheroid form.
||An annealing process where the temperature,
soak time and cooling are designed to reduce the internal stresses without
substantially modifying the structure of the steel
||Generally considered an impurity in steel due
to its detrimental effects upon ductility and weldability. It has beneficial
effects upon machinability however.
||A light rolling operation to give a
restricted hardness in finished cold rolled strip
||A process applied to steel after hardening.
It involves heating to a temperature below the transformation range for a
given time to decrease hardness and increase toughness to the desired
||The maximum load applied to break a tensile
test piece divided by the original cross section of the test piece. It is
normally today measured as N/mm². Also referred to as Ultimate Tensile
|Ultimate Tensile Strength
Symbol V) - Element No. 23 of the periodic system; atomic weight 50.95.
Gray-white, hard metal, unaffected by atmospheric influences or alkalies
but soluble in most strong acids; melting point 31190°F.; boiling point
about 61500°F.; specific gravity 5.87. It cannot be electrodeposited. Its
principal functions as an alloy in the making of tool steels. (1) Elevates
coarsening temperature of austenite ( promotes fine grain). (2) Increases
hardenability (when dissolved). (3) Resists tempering and causes marked
of hardening high carbon steels by quenching in water or brine after
in resistant to deformation (i.e. in hardness) produced by cold working.
load per unit of original cross section at which, in soft steel, a marked
increase in deformation occurs without increase in load.
||The stress at which general plastic
elongation of the test piece takes place.