A method of producing a design on metal
surface by hammering the metal using a punches or chasing tool designed
for the purpose. The metal is supported by a stake Unlike engraving, metal is
distorted to produce the design, not removed.
Related terms - engraving, repoussé
Cinder
Cire perdue
Term meaning lost wax casting.
Clinker
Term used to describe low density slag-like materials. Usually they are semi-vitrified
and vesicular materials with unfused, or partially fused fragments of the charge, hearth
lining, or refractory material in corporated with the fuel. They may
not necessarily be associated with metal working. When the fuel is coal
or coke it usually contains enough rock fragments to produce a clinker
if burnt at a sufficiently high temperature. In old reports the term may
also have been used interchangeably for slag,
and Fuel Ash Slag.
The term was commonly used in the 20th century to describe the larger semi-fused and sintered masses
of ashes found in the morning when a household coal fire had burnt out. The term 'Cinders' tended to be used
for the smaller pieces of similar nature. (There may have been regional variations on this usage.)
The term is best kept for non-metallurgical pyrotechnical ceramic debris - such as was
generated in the fireboxes of furnaces for 19th and early 20th century boilers and the like,
e.g. boiler clinker
Close
Packed Hexagonal
Close-packed hexagonal. A hexagonal
net in which the atoms are arranged in a repeating sequence ABABABA......
One unit lattice has a hexagonal prism with one atom at each corner, one
in the centre of the bottom and top faces, and three in the centre of the
prism. CPH metals tend to be brittle, e.g., cadmium, cobalt, titanium,
and zinc.
Coal
Now refers to
deposits of fossilized plant remains that have been subjected to moderate
heat and pressure to partially converted to carbon and other hydrocarbons.
As the original deposits formed in anaerobic swamp conditions coal often
is contaminated with iron sulphide. The sulphur from these sulphides make
coal unsuitable for many metallurgical processes without conversion to
coke.
Coal was used
extensively for smithing in the Romano-British period, even in regions
well outside the coalfields.
The term coal
(in various spellings) was applied to what is now know as charcoal, with
coal being refered to as mineral coal, or sea coal.
Cobalt
A metallic element with atomic number 27, atomic weight 58.93, density 8.9 g/cm3.
The element was produced unknowingly by Georg Brandt in 1742, but was not identified until 1780 when
Bergman recognized it as new element. However, cobalt compounds had
been used to colour glass from at least 1500 BC.dd>
Cobbing
- ore preparation /cobb?
Cohenite
Coherent
precipitation
Coining
Coke
Coke is formed
by heating suitable coal under partially reducing conditions to drive off
the volatile components and reduce the sulphur content. Initially, coke
was produced in clamps in manner a very similar to that of charcoal, but
later retorts were used so that the gas evolved could be used to heat other
parts of the processes involved.
The change from the use of charcoal to coke in iron smelting, pioneered
by Abraham Darby at Coalbrookdale after possible experimental work in the
Bristol brass industry, was important one of the essential steps of the
industrial revolution.
Cold working.
Cold working is the mechanical deformation of metal at, or near, room temperature. This
deformation produces a high density of dislocations,
and grain deformation in the metal.
This results in an increase in hardness
at the price of reduced ductility.
Colluvial
Sediments formed
by hill-wash, soil creep and landslip. This class of sediment includes
scree-slope deposits, and cliff falls.
Columnar
Long column-like grains that can form
when a pure metal is cast into a mould. Columnar structures develop under
conditions of moderate unidirectional thermal gradients. Columnar structures
are also seen in bloomery tap, and smithing hearth bottom slags where the
main heat loss is by conduction through the refractory lining.
Continuous Cooling Curve - CCC
Related terms - Quenching, TTT
Continuous precipitation
The formation of a precipitate or inclusion
distribution uniformly through the grains themselves.
Constituent
Correct term to be used for multi-phase component of a metallographic structure - eg pearlite
is a constituent of the microstructure of a hypoeutectiod steel, not a phase.
Component
Cope
The upper part of a two-part mould; the main bottom section of the mould is the drag.
Related terms -
Core,
Feeder, Riser
-
Simply melting
a steel of suitable compostion.
-
Melting a mixture
of low carbon iron and cast iron in a crucible together with a flux to
seal the melt to prevent decarburisation.
-
To seal a mixture
of phosphorus free low carbon iron and a supply of material with a high
carbon content in a crucible, and some fluxing material to form a seal
once the mixture had started to melt. Then to heat the cricible so that
the iron was carburised to the point that the melting point was reduced
to the operating temperature of the furnace.
In the
west the first method was developed by Huntsmann (
date* 1740s?*) who melted blister steel in
crucibles. Earlier, the second method was used in Italy in the 16thcentury
as described by Biringuccio.
This
has been decribed as the Brescian or co-fusion process.
In
Sri Lanka, India, Persia and central Asia there was a long history of producing
crucible steel by a variety of processes (variations on 2 and 3 above).
Evidence of extensive crucible steel production has been found at Merv
(Feuerbach 2002) These steels have
been known as Wootz or bulat. Some of these steels are capable of thermo-mechnical
processing to produce patterned steel without welding. Such products are
often misleading described as being of Damascus steel, however, there is
no evidence of self-patterning crucible steels having been produced at
Damascus (See Allan and Gilmour
76-79, for discussion of Damascus problem). Such patterned forged crucible
steels were not produced by the process of damascening
(pattern welding) as was once throught.
Related
Wootz, Huntsmann, Watered-silk steel
Crushing -
in ore processing
Crystal
Each individual
particle of metals and most minerals have their atoms arranged in regular
three dimensional arrays. The regions over which the atoms are aligned
on a particular set of direction is a crystal or grain. In metals, the
boundaries between each aligned region are the grain boundaries.
Crystal Structure
The atoms in most
metals and minerals are arranged in a three dimensional repeating units
. In most pure metals these repeat units consist of cubic face centred,
cubic body centred or a hexagonal repeat units. However, intermetallic
and minerals can much more complex atomic arrangements that define the
crystal structure. Those materials which do not have a regular repeating
arrangment of atoms are described as a amorphorus or glassy.
Cucurbit
A retort with a narrow neck which fits
into the alembic.
Cupel
A porous ceramic, often made from bone
ash or other refractory components. The cupel is used to extract or assay
precious metals that have been dissolved in metallic lead by the process
of cupellation.
See parting, cupellation
Cupellation
A process used for extracting silver
and gold from lead. The principle involves first the disolution of the
material to be tested in molten lead, then the oxidation of this lead to
litharge (PbO) in a shallow, dish-shaped crucible usually made of bone
ash (cupel ), leaving the precious metals behind as a molten globule.
A temperature of about 1000 ºC is needed. The litharge volatilizes or is
skimmed off, or is combined with the bone ash in the cupel.
Related:-
Bullion, parting,
Cupola Furnace
Cuprite
The mineral name
for the copper oxide Cu2O. May be a constituent of copper ores
in oxided part of copper veins, and is often seen producing the red glaze
colour on copper working crucibles. Also see
Tenorite
Cupro-nickel
Alloys containing copper and nickel,
usually from 15% to 70% nickel, but in ancient alloys often with less nickel
than this. Alloys with about 25% nickel are now used for coinage metals.
Early examples of copper-nickel alloys are also known, the most famous
being the Bactrian coinage.
Related terms Pak
Tong
Currency bar
A name applied to some forms Iron Age
iron trade bars, of which over 1500 have been found in Britain. The typical
'currency' bar is flat sword shaped bar with a tubular socket at one end.
There are a large number of British regional forms, some of which include
plough-share, and spit shaped, but also those with welded tips, others
without sockets, and other forms of tapered thick bar.
The term was originally applied early
in the 20th century when it was thought that they came in various 'denominations'.
The great variety of form and weight of these bars shows that, in spite
of the writings of Julius Caesar, these bars were not used as currency.
It was also thought that they may have been half finished swords (moods),
but metallographic analysis of Iron Age swords and the currency bars shows
that the swords could not have been formed directly from a currency bar
with a great deal of forging and welding.**
D
- D.P.N. - Diamond pyramid number
- A method of hardness testing in which a pyramid shaped diamond is pressed
into the surface of the metal under a fixed load. The size of the impression
made is related to the hardness of the material. Also known as Vicker Pyramid
Hardness test and results quoted as VPN (Vicker's Pyramid Number). This measure
of hardness is more linear over a greater range of hardnesses than the other
hardness tests.
- Related terms - Brinell hardness, Rockwell
hardness.
- Dam - in blast
furnace
- Damascening
- An ancient process of ornamenting a
metal surface by the use of pattern-welding. The process was used in immitation
of early Middle Ages patterned swords said to be from Damascus
. In the damascening process, a bar of steel and iron welded together is repeatedly
drawing out, doubled back on itself, and welded together. The surface was
later treated with acid to darken the steel areas. Ferrite remains bright.
In the East the process of inlaying metal on metal is common, particularly
in parts of Iraq and India, where it is known as Kuft
work. The technique is still used for high quality
shot-gun barrels. Unfortunately, the term is often mis-used to describe forged
cast hypereutectoid steels (Wootz, Watered Steel)
as the patterns can be similar although the mode of formation of the pattern
is very different.
- Damascus Steel
- A misnomer for forged crucible steel with an internal pattern of carbides
produced by the result of thermo-mechanical treatment. Although this decorative
steel was sold thorough Damascus, and the value of the artefacts made of crucible
steel was enhance there by the addition of gilt decoration, there is no evidence
for it production at Damascus. The term has been use for both self-patterning
crucible steels (watered-silk) and pattern-welded steels and has lead to considerable
confusion in the older literature on the subject. In the opinion of the author
(CJS) this name should no longer be used due to the past confusion.
- Dating -
- Other than normal
archaeological stratigraphic methods there are a number of dating techniques
that are of particular interest to the archaeo-metallurgist.
-
- Archaeo-Magnetic
- - Radio-carbon
(C14)
- -AMS
- - Thermoluminesence
TL
- Dead Roast
- Usually applied to the preparation of sulphide ores for smelting. the term
is applied to a roasting process which is carried out for sufficient time
and under strongly oxidizing conditions to remove all the sulphur.
- Detection limit
- The lowest concentration of an element or substance that can be detected
reliably. Usually set so that the measurement of the signal from the element
is either twice or three times the standard deviation of the signal from the
background.
- Delafossite
- Dendrite
- Depletion gilding
- Depletion silvering
- Diamond Pyramid Number
- also denoted
as DPN, VPN
- Die
-
- Die-casting
- Diffusion
- The movement of one type of element through another without reaction. Many
of the important processes in metallurgy are controlled by diffusion. During
solidification, the rate of diffusion of the elements in liquid ahead of a
freezing front control whether the solid grows in plannar,
cellular or dendritic manner. In the solid state,
many phase formation, and growth processes are controlled by diffusion. These
diffusion controled processes can be surpressed by rapid-cooling (quenching).
- Diffusion bonding
- A method of joining
to pieces of metal without melting. When two chemically clean metal surfaces,
are placed together and heated under pressure but to temperatures under that
of the melting point of either of the alloys involved, the atoms in the surface
diffuse so that the bond and voids are eleminated.
- Direct
Process (iron smelting)
- Another name for
the bloomery process, so named as malleable iron (bloomery iron) is
produced directly from the ore. Unlike the indirect, or blast furnace process
in which cast iron has to be refined to a malleable form (wrought iron, puddled
iron, mild steel)
- Direct Process
(brass making)
- Discontinuous
precipitation
- Dishing
-
- Dislocation
- **
- Dislocation
entanglement
- Distillation
- Drag
-
The lower part of a two or more part mould.
Related terms -
Cope,
Core, Feeder,
Riser
- Drawing
- The act of pulling
a wire through a drawplate of hard material to reduce its diameter.
**
.
- Dutch Metal
- Brass leaf - or more correctly foil.
Related - Pinchbeck>
- Ductility
- The ability of
a metal to be drawn or deformed. Face Centered Cubic (FCC)metals
such as silver or gold tend to have better ductility than other metals.
- Duralumin
- A trade name for an alloy of aluminium
hardened with copper. The earliest commercial light metal alloy. OED gives
the first reference as 1910.
- Dynamic Recovery
- See Recovery - dynamic
-
E
-
Electrochemical
corrosion
-
Electrochemical replacement plating
-
Iron when dipped
in solution containing dissolved copper will become coated with metallic
copper as the more reactive iron goes into solution. The process has been
used to extract copper from ground water leaching through old copper tailings
dumps.
-
Electroless plating
-
Typically a process
to apply a nickel plating (check method used)
-
Electron
Probe MicroAnalysis - EPMA
-
EPMA is carried
out using a speciallised type of scanning electron microscope (SEM) which
is designed specifically to produce high quality chemical analysis, using
wavelength dispersive X-ray detectors. Wavelength dispersive X-ray (WDX)
detectors (spectrometers) have much higher sensitivity and resolution than
standard energy dispersive detectors (EDX), and the machine is designed
to give high and stable electron probe currents, together with a fixed
sample-detector geometry with polished samples. This means that the accuracy
and detection limits are much better in an EPMA than in a standard SEM fitted
with a EDX detector. All results of electron induced xray analysis (WDX
and EDX) should quote the energy of the incident electron beam as the controls the
efficiency of the generation of the various characteristic X-rays and the shape of the
continuous bremstrahlung background.
In addition to analysis, EPMAs are also used to produce elemental maps which
given an easily understood distribution of the element present on the centimetre
to micron scale.
-
Electroplating
-
The technique using an electrical current to deposit a thin uniform layer of metal on
a conductive object to improve either its mechanical properties, chemical
corrosion resistance, or aesthetic appearance. Initially the process,
invented by Werner Siemens in 1842, was used to deposit silver on copper
and was introduced to England in the following year by his brother Karl Wilhelm.
-
Electroplated
Nickel Silver - EPNS
-
An alloy of copper,
nickel, and zinc typically with composition of 60% copper, 22% nickel,
18% zinc, and electroplated with silver.
-
Electrum
-
A naturally occuring
alloy of gold and silver.
-
Elling Hearth
-
A hole in the
ground in which wood was burnt for the production of potash. The potash
was recovered by dissolving the soluble constituents of the ashes in water,
which could then be concentrated by evaporation. The potash may be used
as a mordant in dyeing and for the production of soap. This term has also
been used to describe ore-roasting hearths; it stems from an Anglo-Saxon
word eilding meaning firing or fuel.
-
Could
this refer to the practice of 'elyng' or calcining, by which iron ore was
roasted to 'soften' it, by removing excess moisture and breaking
it into smaller pieces prior to smelting. 'Elyingwood' was accounted for
at Tudeley ironworks in the 14th century. Schubert describes the process
on p.216 of his History of the British Iron and Steel Industry (1957).
-
Eluvial
-
A deposit in a
soil which has formed by the transport of the material in solution or
suspension. Hard pan and bog iron ores are eluvial deposits.
-
Energy
Dispersive X-ray Spectroscopy (EDX,EDS)
-
Usually this involves
the excitation of X-rays by an electron beam in an SEM or EPMA, the their
detection using a lithium drifted silicon detector, or more rarely a geramanium
detector. These detectors a solid state detectors which measure the number
of electron-hole pairs produced by each incoming X-ray. As the the number
of electron-hole pairs is directly proportional to the energy of the x-ray,
it is possible to assign an energy to that X-ray. Hence, it is possible
measure all X-ray energies up to the limit of the range of the detector
simultaneously (0.2 to 20 keV). The disadavantage of this method is that
the energy resolution (110-150 eV) is less that that of WDX detectors.
This, in turn, restricts the detection limit to a value of typically 0.1%
under normal analytical conditions.
-
Engraving
-
EPNS
- Electroplated Nickel Silver
-
Equiaxed
-
A termed used
in descriptive metallography indicating that the grain structure of the
metal is such that the grains are of equal dimensions or properties in
all directions.
-
Equilibrium
phase diagram
-
A equilibrium
phase diagram is a diagram in two or more dimensions giving a plot of the
phases present at a given temperature and composition. Two dimensional
phase diagrams plot the composition of two elements (horizontal) against
temperature (vertical), when three or more elemental are involved it becomes
more complex to illustrate the phase diagram on the page. What is usually
displayed is a triangular plot of composition, with the temperture of phase
boundaries marked, or with the solidus or liquidus surfaces plotted as
contour maps. [Diagrams needed].
It should be remembered that the the equilibrium phase diagram is just
that, it describes the situatation at equilibrium. However, some of the
reactions described in the phase diagram take a considerable time to complete,
and some extremely important phase transformation produce non-equilibrium
phase (metastable phases such as martensite). Therefore, although the equilibrium
phase diagram can be an extremely important tool to the understanding of
the metallurgy of the system, it may be necessary to consider other factors
or ways of displaying the way in which the system changes with time, such
as the TTT diagram.
-
Equilibrium
structure
-
The distribution
of phases and grains that would exists if the system was held at the specified
temperature for an infinite time.
-
Etching
-
A process in which
corrosive solutions are used to selectively remove or stain selected microstructal
components from a polished metal surface so that the microstructure can
be seen using a reflected light (metallurgical) microscope or the overall
structure of metal can be seen by the naked eye (macro-etch). There are
many hundred different etch solutions, each one will reveal one or more
specific micro-structural components. The etch characteristics of some
etches will be altered by traces of unusual elements, with the result that
it may take some time and effort to find the optimum etch conditions for
some archaeological alloys as they do not fall into the 'standard' compositional
ranges for the etches.
-
Euhedral
-
A microstructural
term derived from rock mineralogy, most frequently used for the description
of slag morphologies. An euhedral component of a microstructure is one
in which the phase is completely bounded by its characteristic crystallographic
faces. Synonymous terms idiomorphic and less commonly automorphic. Diagram
?
-
-
Also see subhedral
and anhedral
-
Eutectic
-
An isothermal
transformation in which a liquid transforms into two separate solid phases.
This sort of transformation can only occur at a set composition and temperature.
This will be the lowest melting point for any composition composed of those
phases where the liquidus
and solidus temperatures
are the same.
-
An alloy having
the eutectic composition.
-
A microstructure
consistent with having solidified from a melt of eutectic or near eutectic
composition. These compositions are those which have the lowest local melting
point. At moderate cooling rates the simultaneous growth of two phases
results in growth morphologies with fine regular dispersions of one phase
in the other.
-
Diagrams to be added
-
Eutectoid
-
The solid state
transformation equivalent of a eutectic, in which one solid phase transforms
into two other different phases. The most common example is the transformation
of austenitic iron, with 0.8% carbon in solid solution, decomposes into
nearly pure iron (ferrite) and iron carbide, (Fe 3C) cementite,
usually as alternating parallel plates of the two phases (pearlite). Diagrams
to be added
Update 30-Dec-05
Modified 02-01-06
by Chris Salter
Status
Terms to define - 58
Terms to be checked - 31
Terms checked - 133
References missing -
Links missing -
Total terms in section - 222