S

Safidruy

Islamic term for high tin bronzes, often white in color.

Sand Casting

A method of casting in which the mould is made of sand and a binder rather than clay, metal or stone. Simple shapes may be cast directly into impressions made in the sand using a pattern. But for more complex objects, sand castings are two part mouldings, with pattern first being impressed into the lower part of the mould. A parting agent is applied to both the surface of the sand and the pattern. Then a box to contain the upper part of the mould is put down around the pattern, and sand is rammed into the box around the pattern to fill the box. The upper part of the resulting mould is lifted off the lower, and the pattern removed. The upper part of the mould is then lowered back on to the lower ready to received the molten metal.

Green sand

Silica(te)? sand

Scoria

Scoria is an old name for slag, probably of late Middle English origin, but not often used now. Care needs to be taken with old documents refering to scoria as from the late 18th century, the term scoria was also applied to the rough, broken, cinder-like surface of some types of lava flows, and occasionally the term 'slag' was used to describe lava.

Segregation

The non-uniform distribution of alloying elements, impurities or phases. Normally, used to describe compositional inhomogeneity developing during the solidification of a metal from a melt. Normally, when a metal or other multicomponent systems solidify the composition of the solid that first freezes will be different from that of the liquid; it will have a lower concentgration of the lower melting point component. This result in the liquid composition becoming slightly enriched in the lower melting point component. Because solid-state diffusion is much slower that liquid-state diffusion it is rare for the whole system (solid and liquid) to come to equlibrium before more metal freezes over the first metal at normal cooling rates. This can lead to a number of different types of chemical segregation in cast alloy

1. Normal segregation. The term applies to the overall distribution of elements in the casting. In a 'normal' casting the metal freezes from the outside to the centre. Thus, the local composition metal on the outside of the casting will have a higher melting point than the centre. The centre of the casting will collect all the low melting point components.
2. Inverse segregation.. Again, term applies to the overall distribution of elements in the casting. However, in this case, the lower melting point constituents, such as the phases rich in tin or arsenic in bronzes are concentrated toward the surface of the cast due to contraction of the casting forcing the remaining low melting point liquid from the centre to the edge of the casting.
3. Dendritic segregation.
Dendritic segregation, describes local differences in composition in which fern-like dendritc growth occurs from local compositional gradients. In this case, the core of the dendrite will have a local high melting point composition, compared with the inter-dendritic material. Castings showing either normal or inverse segregation are likely to have dendritic segregation on the small-scale.

Related terms - Dendrite

Set

Smithing tool, a chisel with handle mainly for cutting hot metal.

Shaft furnace

1. In the classification of archaeological furnaces, a furnace in which the main reaction chamber is taller than it is wide and the width of the chamber does not vary significantly with height, is thought to be a shaft furnace.
   There does not seem to be a generally accepted definition for the height to width ratio to determines the limits of a shaft furnace - but anything with a height to width ratio greater than 1.5 seems to be thought to be a shaft furnace.
2. The term shaft furnace can be more generally used to describe all furnaces in which the reactants (ore and fuel) move down through the furnace chamber while the combustion products flow up through the furnace. Thus they differ in the manner in which they work to hearths and reverberatory furnaces

Related terms - Furnace, Furnace Types, Hearth, Reverberatory furnace

Shear steel

Shear Steel was formed by taking several pieces of blister steel and welding them together. This has the effect of reducing the inherent inhomogenity across each individual bar of blister steel. The process is well described by Percy (1864 Vol II.3, 859) -

Bars of blister-steel are broken into pieces about 16in. long (400 mm), and drawn out at a red heat under the hammer to the width of about 1 1/2 in. (38mm) and the thickness of about 1/2in (13mm). Several bars are thus obtained are piled on one another, and the end of the pile is firmly wedged into an iron hoop with an handle attached to it. The free end of the pile is raised to welding heat in a hoolow coke fire, during the process being dusted over with finely-pounded clay, welded under the hammer and reduced to about 2 in. (50mm) square. The hoop is now detached from the other end of the bar, and this end is treated in exactly the same manner as the first end.

Double shear-steel is formed by taking a bar of shear steel, breaking it in half (or bending it back on itself) and welding the two pieces together.

Related terms - Blister steel, Piled Steel, Steel

Sheffield Plate

A plating technique to plate copper with silver developed by Boulsover during the 1740s in Sheffield. Silver was diffusion bonded over thick copper sheet by heating a sandwich of carefully prepared sheets of silver, copper, and silver protected by iron sheets to red heat. The silver and copper was relative thick, but could be rolled or forged down as the copper and silver retained their relative thickness. With the introduction of electroplating to Britain in 1843 by Karl Wilhelm Siemens and its development by James Elkington, the use of Sheffield plate to dwindled and stopped in the second half of the 19th century. (Day & Tylecote, 1991, 29 & 177)

Short

A metal is descibed as short when it tends to crack after a relatively small amount of mechanical deformation. The term tends to be applied to steels with reduced workability. Steels may be described as cold short or hot short.

Cold Short

Metals that have limited ductility at low temperatures. Steels containing phosphorus are particularly prone to cold shortness - hence the British steel makers preference for Swedish low phosphorus iron rather than British iron many of which contained significant quantities of phosphorus. Although, phosphoritic iron with low carbon contents can be drawn to form wires. Goodway

Hot Short

A hot short metal will have a tendency to crack during hot-working. This is usually due to the presence of a low melting point phase at the grain boundaries. In the case of steel, sulphur is particularly detrimental as iron sulphide will wet the grain boundaries with the rest the steel will fall apart if forged at high temperature. The addition of manganese to form manganese sulphide rather than iron sulphide prevents this.

Silica

The oxide of the element silicon, with the chemical formula SiO₂. Pure (or nearly pure silica) can occur in several mineral forms: quartz, tridymite, and cristobalite, depending on temperature and pressure. Silica combined with other metal oxide comprise a large part of many rock-forming minerals, and hence silica is a major gangue component or many ores. Hence, silica is a major component of many smelting slags, although occasionally some copper smelting slags can have very low silica content as there is a low melting point region in calcium-ferrite system.

Silver

A white-coloured metallic element that is very ductile and malleable. Silver is one of the noble elements as it does not oxidize when heated in air. Silver was usually obtained by cupellation of lead ores, although it may also be extracted directly from silver sulfide deposits. Pure silver is often stated to be 1000 fine and alloys are based on this nomenclature. For example, sterling silver is 925 fine (contains more than 92.5 % by weight silver). The atomic number of silver is 47, and its atomic weight 107.87, with a melting point of 960 ºC, and specific gravity 10.50.

Sinking

A forming technique in which a vessel is formed from a sheet by hammering from the inside (the concave side). The sheet metal is hammered into a shallow concave depression in the anvil. Also called blocking, dishing or hollowing.

Related term - Blocking, Caulking, Dishing, Raising

Sinter

To render a pressed powder solid by heating without melting.
Originally this term was applied to describe hard mineral encrustrations found on rock, especially those around mineral springs (18th century). From the late 19th century used in a material science context to describe the process and products of high temperature solid state consolidation of powders and granular material. Shorter Oxford Dictionary

Slack quenching

The term 'slack' indicates something done without due dilligence, hence the term slack-quenching implies a structure that has not been fully quenched. That is,the structure is not fully martenistic and that this was due to the quench having been done into a less severely quenching medium such as oil, or molten lead, or the quench was deliberately interrupted or delayed.
However, the fact that an early piece of quenched steel does not show a fully tempered structure does not necessarily mean that it was deliberately 'slack' quenched, as the composition of many of these steels were such that it would be nearly impossible to quench the metal fast enough to avoid getting some nodular pearlite (troostite) or bainite. Modern steels contain significant quantities of manganese which moves the Continuous Cooling Curve to the right (to slower quench rates) compared with most ancient and historic steels. Without this manganese, or a very high carbon content, the steel would have to be cooled to from above the eutectoid temperature to room temperature in a fraction of a second to achieve a fully martensitic structure, which would have been very difficult if not impossible for many artefacts.

  In some cases structures have been described as having been 'slack quenched', it is clear that the steel had not been fully transformed to austentite but had been cooled from a temperature in which both ferrite and austentite were still present.

Without knowing the full composition of a steel it is probably best not to use the term 'slack' quench with its implications of deliberate action.

Related terms - Manganese, Spiegeleisen, Troostite .

Slag

A general term for a variety of non metallic, usually oxide waste products formed during smelting, refining, and the hot-working of metals. Although slags are often considered as a mere nuisance waste product, they are a vital component of the production and working of many metals. The formation of a molten slag at a suitable temperature makes possible the separation of the metal from it ore, and protects the metal being re-oxided. Thus, the use of the term slag implies that the material has been molten or very nearly molten as result of metal production or refining, but the term is more widely used to cover any non-metallic semi-vitreous material produced during any pyrotechnic process.

Many early smelting slag were composed mainly of iron oxide and silica, so that the majority of the nmicrostructure is in the form of the silicate mineral fayalite (2FeO.SiO₂), with the excess iron in the form of its oxides. The other minor elements present forming a glassy or psuedo-glassy component of the microstructure. This was true of both iron and copper smelting slags. However, in some regions and periods low melting point slags of non-fayalite-iron-oxide compositions are know to produced during both copper and iron smelting, probably due to the fortuitous local ore composition giving a low melting point.
Later in the history of smelting, when higher furnace temperatures were possible in the blast furnace, lime was added to the charge during iron smelting to replace the iron in the slag, increasing the efficiency of the furnace.

Slag can be classified on the basis of its physical morphology and chemical composition. A morphological study of the complete suite of debris from a site will often be sufficient to identify the type of metal-working being carried out on that site. However, care needs to be taken with such identification when there is only a very limited amount of slag recovered. Some very different metallurgical processes can produce slags of very similar appearance, for instance, some copper smelting tap slags can easily be mistaken for those from iron smelting. Sometimes the forging of iron will produce a number of different slag types, some of which could be easily mistaken for small flows of tap slag, produced during smelting.

Types of bulk slag

Slag - Blast furnace

These are glassy or partially glassy massive tap slags. In the case of iron blast furnace slag they have much lower iron contents than bloomery slag. This was because the higher furnace temperatures possible in the blast furnace allowed the replacement of most of the iron in the slag by calcium from a lime flux.
Charcoal blast furnace slag tend to be of a dark olive-green colour, whereas, early coke-fired blast furnaces, in Britian, produced slag that was of an opaque blue-green, often showing banded and mottled colours. The slag from the later hot-fired blast furnaces tends to be a more uniform black glass although some areas of mottled opacity may occur.

Slag - Cinder

A term used to describe the type of slag that is angular and without obvious flow forms, but often takes the the impression of the burnt-fuel around which it had formed.

Slag - Fuel Ash

A low density slag-like material - often of a light colour externally with a high silica content. Complete pieces may have rounded exteriors with no obvious points of contact with a surface on which it cooled. Although, the exact origin of much Fuel Ash slag is uncertain, they often contain, partialy fused or sintered quartz grains and other rock or soil debris. It is likely that this material is the result of a high temperature process which results in the sintering and partial melting of the non-combustible fragments in the fuel, together with material from the surrounds of the fire. There are a number of processes that could generate this type of material:- metal-working (all forms), pottery making, burning of daub during a building fire, glass-working, salt-making, cremation, or simply the burning of a fuel with a very high silica content such as bracken. References

Related terms Cinder, Clinker

Slag - Furnace bottom

A furnace bottom is the large block of slag left at the bottom of a furnaces at the end of a smelting run. Both slag-tapping and non-slag tapping furnaces can produce this type of slag. In the case of non-slag tapping furnaces, most of the slag produced during the smelting will be in this form. The block of slag would either have to be removed from the furnace before the furnace could be reused, as was probably the case for the smaller shaft furnaces see Peter Crew's experimental rconstructions of the prehistoric iron furnaces of North Wales, or the furnace was effectively used only once, as was probably the case with slag-pit furnaces. In the case of slag-tapping furnaces, the furnace bottom represents a much smaller proportion of the slag produced by the furnace with a high proportion being tapped out of the furnace. In this case, the furnace bottom only represents the last of the slag that had drained to the bottom of the furnace and solidifed there because the build up of the bloom caused the temperature of the bottom of the furnace to fall below that where it was possible to tap the last of slag.

There is a great variation in the size of furnace bottoms from as low as a kilogram, or so, to hundreds of kilograms, depending on furnace design and operation. At the smaller end of the scale it can be difficult, if not impossible, to distinguish large smithing hearth bottoms from small furnace bottoms. It such cases, the relative proportions of other slag types is the best indicator of the type of activity taking place.

Slag - Refining

Slag produced as a result of a refining process. This term usually is applied to slag produced as the result of refining non-ferrous metals. Some copper refining slags have a very high iron oxide (magnetite) content, and thus can easily be mistaken for iron-working slags.

Slag - Smithing

Slag - Smithing Hearth bottom

Slag - Tap

Tap slag is slag that is tapped out of the furnace and allowed to cool and solidify as flows, or as more massive pooled lumps. The upper surface of tap slag usually has distinctive ropy flow patterns. Often large pieces of tap slag will consist of layers of smaller flows on top of each other.
On sites from before the Industrial Revolution the presence of large amounts of tap slag is indicative of smelting activity.

Care needs to be taken when identifying tap slag when only a small amount of slag is present or has been sampled, as small flows and drips produced by smithing activity can look similar to small broken up tap slag flows.

Related term - Tap Slag

Slag - Undiagnostic

Small-scale slag

Hammer-scale

Hammer-scale are usually small thin scales of metal oxide. These are formed by the shedding of the oxide layer formed at high temperatures on the surface of metals when they are heated. Iron hammer-scale is highly diagnostic of forging activity, as the surface scale may be shed several times during one cycle of hot forging. Hammer-scale made be formed during the working of copper or even base-silver alloys during annealing or homogenization treatments - most falls from the metal during quenching or pickling prior to the next cycle of forging.

Slag - Spheres

Spherical Hammer Scale

These are drops of molten slag that have cooled and solidified whilst in the air. When hot enough the hammer scale layer will melt, and when struck by a hammer the molten liquid is ejected as a spray (the sparks flying away from the blacksmith's hammer during welding are these droplets).
They varying is size from a few tens of microns to several millimeteres, they are often hollow. They may or may not be magnetic, depending on their iron content. The non-magnetic spheres are the result of the silica from the slag already present in the metal or any flux added during welding, reducing the iron content to below that required to allow magnetite to form.
Spherical Hammer Scale is indicative of high temperature forging as the temperature required to produce molten iron-oxide (or possibly molten iron-oxide-silicate) is much higher than that required to produce a solid layer of iron oxide. Thus a blacksmithing site, on which a high proportion of spherical hammer-scale to normal flat hammer scale is found, would suggest that the blacksmithing involved a lot of welding activity.

Slag spheres

Slag spheres are of normal slag (smelting or smithing) and are larger than most spherical hammer-scale, typically, 5mm to 15mm.

Related terms - Hammer scale, Scoria

Slag Hearth

Slag Hearth - Spanish

Slag inclusion

Slag Smelting - Lead smelting process

Slag stringer

Small pieces of slag (inclusions) that have become incorporated into the metal and are then strung out as small elongated ribbons as a result of working the metal to shape it.

Slip planes

Face centred cubic metals may show slip planes, a fine series of lines in two intersecting directions upon heavy deformation of the metal.

Slitting

Slush casting

A method of casting in which metal is often spun or agitated in the mold so that a thin shell is formed. The the excess liquid is poured out before it freezes. More common in ancient and historic metalwork is slush wax work in which wax is slush cast over a piece mold interior before investment.

Smelting

Smelting is the process of extracting the metal from its ore. This involves a chemical reaction between the ore and the fuel, or between the heated ore and a reducing atmosphere. Most smelting processes are carried out above the melting point of the metal concerned. So that both the metal and waste products (slag) are liquid and can be separated using gravity. The main exception being iron smelting, before the introduction of the blast furnace process, where the iron remained solid or at least in a pasty state, but the waste products formed a molten slag.

Smith - black

Smith - white

Smithing

Soak

A prolonged heat treatment.

Solder

Is a term to describe alloys that can be used to join two pieces of metal. These alloys have lower melting points than the metal, or metals, they are joining, and wet them. Typical solders are classified as soft or hard solders depending on their melting points.

Soft solders

A term applied to lead-tin alloys used in soldering. The upper limit of the melting range is about 300 ºC, and many alloys melt at about 130-180 ºC. Lead-tin solders are now being replaced by other low melting point alloys due to the toxicity of lead.

Hard solders

**

Solid Solution

A single solid crystalline phase containing two or more chemical species in concentrations that may vary between limits imposed by phase equilibrium.

Solidus

The line in the phase diagram that describes the temperature at which an alloy of given composition is completely solid. This line forms a boundary on the phase diagram between those regions which are completely solid and those where there is a mixture of solid and liquid. At specific temperatures and compositions, the the liquidus and solidus lines may meet (the eutectic and peritectic points, and at the melting point of a pure phase).

Sorbite

This term refers to a spheriodized granular cementite structure produced as the result of an annealing or tempering process.

Sow

Speculum

Spiegel(eisen)

Speiss

Spelter

?Spheroidal Graphite

Spheroidal pearlite

A metallographic structure in which the action of prolonged temperature (below the critical temperature) has degraded the usual lamellar form of pearlite to the extent that cementite forms globular particles within a ferrite matrix.

Spheroidised - structure

Spheroidizing - heat treatment

Spiegeleisen

Spinning

Sprue

Stamp - Ore

Stamping

Stamping mill

Stamping & Potting

The term cover a number of methods used to refine cast iron using coal or coke as a fuel, before the development of puddling. In these methods, involved decarburising the cast iron to some extent in a coal-fired finery. The resulting metal was then broken up or granulated. The broken metal was then melted in crucibles together with a basic flux to absorb the sulphur introduced by the use of coal. Such a method was described in a patent granted to John Wood in 1761, in which the broken metal from the finery was melted in crucibles together with a flux made from kelp* and other alkali fluxes using a reverberatory furnace.

*Kelp is a brown seaweed which has high content of alkali metals.

Related Terms - Refining (cast iron)

Stannite

Steadite

Stearite

A soft silicate which carves easily; also called soapstone.

Steel

Plain steels are alloys of iron and carbon in which the carbon content does not exceed about 2.1%. The carbon is present as cementite, usually as a component of pearlite. Low-carbon steels contain from 0.09% carbon to 0.2% and are soft - the same composition range as bloomery iron. Medium carbon steels contain 0.2-0.4% carbon and high carbon steels more than 0.4%. Modern alloy steels do not necessarily contain carbon in more than trace amounts, but are alloys of iron and some other elements.

Steel - Alloy

Steel - Bloomery

Steel directly produced in the bloomery furnace. By control of the furnace conditions - rate of blowing, ore-charcoal ratio, charcoal type, size of ore and  charcoal particle size it is possible to produce a bloom with a considerable amount of steel (carbon content > 0.3 wt %).

Steel - Crucible

Steel that has been formed in a crucible. The problem with steel production is that pure metallic iron only melts at a temperaturein excess of 1500°C. Therefore, unlike copper alloys it was not possible form steel by mixing in the liquid state until the discovery of refractories capable of withstanding these sorts of temperatures were discovered. Once that happened, there were a number of different ways in which this could be done using different ingredients but they basically fall into three classes

1. Melting a mixture of cast iron and low carbon in the crucible and heating the mixture until the charge completely mixed and melted.
2. Putting a charge of low carbon iron or steel in crucible with a supply of carbon rich material which would result in the carburisation of the metal and bringing the melting point down into the operating temperature range.
3. To simply melt a steel of suitable composition in a crucible.

Related terms: Wootz, Huntsman

Steel - Damascus

Steel - High carbon

Steel - Making

Steel - Manganese

Steel - Medium carbon

Steel - Mild

Steel - Ultra-high carbon

Steel - Watered-silk

Steel - Wootz

Sterling Silver

Stiffness

Stope; stoping

Strain

Strain hardening

A synonym for work hardening.

Strain lines

Same as slip planes. Often seen in FCC metals after heavy working due to slip of planes of atoms past each other.

Streak

Stream tin

Stream tin is another term for alluvial tin ore. These occur where tin eroded from its host rock has been concentrate at the base old river beds. These are often cover by  considerable thicknesses of gravel and detritus. In order to get at this ore it was necessary to dig down through the bed with the aid of shafts not unlike well-shafts, or use hydraulic mining mining to remove the overburden. Evidence of both these types of mining are particularly well preserved on Dartmoor, Devon, UK.

Stress

A measure of the force applied to a metal. It is measured as a force (newtons) per square metre (formerly tonnes per square inch).
    Related term: strain

Strickle board

Woodenboard used to form the mould of a circular component; its edge is shaped to the profile of the object and rotated around it.

Striking

A method of making coins and medals. The impression is cut in negative in a very hard material and this die is then placed over the coin blank and given a single heavy blow thus compressing the metal of the blank into the recesses of the die. Before the introduction of steel, bronze coins could only have been struck using stone or bronze dies. Striking may cause stress-related features in the struck metal such as surface cracking or internal defects.

Stückofen

Swaging

T

TTT diagram

See Time Temperature Tranformation diagram.

Tang

Tap slag

Slag that has been tapped out from the furnace. Usually has ropey flow form in the more viscous slags or forming close to the tapping hole, whereas slags of lower viscosity or solidifying in the collecting area may have a plately form. The ropey flows may have internal voids in which the slag flowed to feed flows further from the furnace and then drained - small-scale version of the lava tubes seen on Hawaii and Iceland.
    Tap slags tend to have characteristic cooling internal morphology with chilled zone of very fine crystals on the lower surface, a zone of columnar dendritic growth, then a void or zone of equi-axed growth, then moving outwards the top surface columnar dentritic growth, and a thinner less severe chilled zone on the upper surface. The upper surface is also often marked with a layer of iron oxide similar to hammer scale as well as iron-oxide crystal growth.
    A single piece of tap slag may be composed of several flows on top of each other, in which case these solification patterns may be repeated.

Note: a single single flow of slag with flattened or rounded section should not be classified as tap slag, as slag forming within the furnace can have this same morphology, and can be the result of smithing or non-slag tapping smelting. When it important to determine whether the slag is a slag on the basis of a few pieces it is necessary to make a polished section to detemine the cooling history.

Related terms: - Slag, furnace slag.

Telluric Iron - native

Temper

Modern

?In heat treatment, reheating hardened steel to some temperature below the A1 temperature for the purpose of decreasing hardness and/or increasing toughness.

Temper as quench

Temper as carbon content

Tennantite

Ternary

Pertaining to three. Usually refers to an alloy system with three elements or components.

Ternary Phase Diagram

Terrestial Iron

Tetrahedrite

Time Temperture Transformation diagrams

Tin

Element with atomic number 50, symbol Sn, atomic weight 118.71, mp 231.8 ºC, specific gravity (grey) 5.75, (white) 7.31. A soft white lustrous metal obtained mainly from the mineral cassiterite, SnO2, but stannite (Cu₂SnFeS₄) occasionally occurs in ore grade concentrations. Tin is not affected on exposure to air at ordinary temperatures. At temperatures above 13.2 ºC the white tetragonal allotropic form is stable and below this the grey cubic form may exist. Above 170 ºC, tin is rhombic in crystal structure. The metal has low tensile strength and hardness but good ductility. Mechanical deformation of white tin makes a distinct sound - tin cry - due to the formation of defomation twins.

Tin stamping

Tinning

The application of a thin surface layer of tin for decoration (copper alloys), or corrosion protection ( iron alloys)

Tin Plating

Toughness

The ability to withstand sudden impacts (One the crucial measurements of a materials mechanical properties.

Related terms: Ductility, **

Trade bar

Tracer / Tracing

Troilite

Trompe

Troostite

In steels this nodular rapidly etching component was originally thought to be a separate phase. However, the introduction of the electron microscope proved that the material was finely divided radiating pearlite, which not resolvable in the optical microscope.
It is often found as characteristic nodules at the grain boundaries in slack quenched steels.

Troy weight

Trunnions

Tundish

Tumbaga

Tutenag

Tutty

Tuyère

Tuyère - Blocks

Tuyère - Eisenstein

Twins

Twins - annealing

Twins - deformation

Tymp

UTS

Ultimate tensile strength

VPN

See Vickers Pyramid Number

Valency

**

Vickers Pyramid Number

**

Related terms - Brinnell, Hardness, Rockwell

Vacancy

**

Vickers Hardness Number

See Vickers Pyramid Number

Void

**

W

Walloon Process

**

Washing

**

Watered Steel

**

Watered Silk Steel

**

Weld

Joining two or more pieces of material by applying heat or pressure, or both, with or without filler metal, to provide a localized union through fusion or recrystallization across the interface. If a filler is used it is of similar metal type as the pieces to be joined with a similar melting point, unlike a solder joint.

Welding, Fire

Welding, Hammer

Welsh Process

The 'Welsh Process' is a copper smelting porcess in which the double decomposition of the matte provided some of the energy requirements of the process, and hence reduced fuel costs. Although this process replaced the industrial dead-roasting of matte, given the high sulphide inclusion density in ancient copper ingots it is likely that the double decomposition was used in antiquity. Related terms: Matte, black metal, blister copper

Whetstone

A stone used for sharpening metal edge-tools.

White Cast iron

Cast iron in which the carbon is present as cementite rather than flakes of graphite. The high cementite content of the metal makes the metal extremely hard and brittle with a white fracture (hence the name). Rapid cooling of  molten cast tends to favour the formation of white cast iron against that of grey. {Presence of grey!)

White Heat

White Metal

Cu₂S

White Smith

Widmanstätten Structure

A structure formed by the solid state decomposition of one phase into one or more other phases with the new phase developing along specific crystallographic planes of the original phase. The structure occurs in steels which have been cooled from high temperatures (~1000 ºC) at a moderate rate. Ejection of ferrite, or cementite depending whether the steel is of hypo- or hyper-eutectic composition, takes place along certain crystallographic planes forming a mesh-like arrangement. Most commonly found as an incidental feature of low-carbon steels. The same type of structure occurs in the octahedrite meteorites which show a typical example of this structure, though on a much coarser scale than occurs with steels. Note: many archaeo-metallurgical texts incorrectly state that ferritic martensites form in rapidly cooled low carbon steels - as it is a diffusion controlled process this is incorrect. A rapid cooling would suppress the fomation of ferrite before the eutectiod temperature is achieved, hence giving rise to a uniform pearlitic steel but with non-euctectiod ferrite-cementite distribution.

Wind-blown furnace

Wipe tinning

Wootz

Hyper-eutectoid crucible steel produced in India and elsewhere in South and Central Asia and Persia. Some wootz steels, with suitable heating and forging, were capable of producing the much prized characteristic watered steel patterns. Although often called Damascus steel, there is no evidence that the metal was produced that far west, although articles made from this metal were decorated with gold designs and marketed there.

Work Hardening

Metals, when hammered at low temperatures, become hardened and stronger. If the temperature of working is increased, a point is reached at which hardening no longer occurs, i.e. the hot-working temperature is reached. The dividing line between hot and cold working for lead is about room temperature; for pure iron it is about 600 ºC.

Workability

Wrought

Simply meaning forged - shaped by hammering, or more recently, by pressing or stamping.

Wrought Iron

A problematic term. Before the introduction of cast steel and iron, all iron alloys had to be forged into shape, therefore the use of the term is tautological when applied to the products of the direct or bloomery process. The term only came into use with the development of the finery and the related succeeding methods of refining cast iron, therefore, it would be best if the use of term was confined to post-medieval refined cast iron.

Characteristics - puddled wrought iron - high slag content, low carbon content, fibrous nature due to rolling

Wüstite

Wüstite is the iron oxide with a composition close to a stoichiometric composition FeO (but is generally deficient in iron Fe_1-xO rather than FeO). The presence of wüstite is indicative of moderately reducing conditions. It is often present in iron slag in dendritic or globular forms. The dendrite arms of wüstite tend to be rounded, whereas, those of magnetite dendrites are more facetted. Intergrowths and overgrowths of magnetite on wüstite, or the other way round are indicative of a change in the furnace/hearth conditions during slag form.

X

Y

Yield Point

Yield stress

The stress at which the metal first deforms by plastic deformation rather stretching elastically. Below the the yeild stress the metal will return to its original shape once the load is removed. If a load is applied such that the metal is subjected to a stress greater than the yield stress, the dislocations in the metal move irreversibly resulting in a permament change in shape.

Young's Modulus

The measure of the extent to which a metal will elastically deform when loaded.

Z

Zinc

Element of atomic number 30, symbol Zn, atomic weight 65.37, mp 419.58 ºC, specific gravity 7.13. Zinc ores were used for making brass by cementation long before the metal was used in its pure form. The limit of zinc that can enter into solid solution in copper by this process is 28%. The Romans made extensive use of brass and, in India, zinc was being made by distillation in retorts during the 13th century A.D. The metal was not known in Europe until rediscovered in 1746. Zinc is a bluish-white, lustrous metal, brittle at ordinary temperatures but malleable at 100-150 ºC.

Zinc Smelting

Updated 30th December 2005

Modified 11th February 2006