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Forging

Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer (often a power hammer) or a die. Forging is often classified according to the temperature at which it is performed: cold forging (a type of cold working), warm forging, or hot forging (a type of hot working). For the latter two, the metal is heated, usually in a forge. Forged parts can range in weight from less than a kilogram to hundreds of metric tons. Forging has been done by smiths for millennia; the traditional products were kitchenware, hardware, hand tools, edged weapons, cymbals, and jewellery.

Since the Industrial Revolution, forged parts are widely used in mechanisms and machines wherever a component requires high strength; such forgings usually require further processing (such as machining) to achieve a finished part. Today, forging is a major worldwide industry.

History
Forging is one of the oldest known metalworking processes. Traditionally, forging was performed by a smith using hammer and anvil, though introducing water power to the production and working of iron in the 12th century allowed the use of large trip hammers or power hammers that increased the amount and size of iron that could be produced and forged. The smithy or forge has evolved over centuries to become a facility with engineered processes, production equipment, tooling, raw materials and products to meet the demands of modern industry.

In modern times, industrial forging is done either with presses or with hammers powered by compressed air, electricity, hydraulics or steam. These hammers may have reciprocating weights in the thousands of pounds. Smaller power hammers, 500 lb or less reciprocating weight, and hydraulic presses are common in art smithies as well. Some steam hammers remain in use, but they became obsolete with the availability of the other, more convenient, power sources.

Processes
There are many different kinds of forging processes available; however, they can be grouped into three main classes:
 * Drawn out: length increases, cross-section decreases
 * Upset: length decreases, cross-section increases
 * Squeezed in closed compression dies: produces multidirectional flow

Common forging processes include: roll forging, swaging, cogging, open-die forging, impression-die forging (closed die forging), press forging, cold forging, automatic hot forging and upsetting.

Temperature
All of the following forging processes can be performed at various temperatures; however, they are generally classified by whether the metal temperature is above or below the recrystallization temperature. If the temperature is above the material's recrystallization temperature it is deemed hot forging; if the temperature is below the material's recrystallization temperature but above 30% of the recrystallization temperature (on an absolute scale) it is deemed warm forging; if below 30% of the recrystallization temperature (usually room temperature) then it is deemed cold forging. The main advantage of hot forging is that it can be done more quickly and precisely, and as the metal is deformed work hardening effects are negated by the recrystallization process. Cold forging typically results in work hardening of the piece.

Drop forging
Drop forging is a forging process where a hammer is raised and then "dropped" into the workpiece to deform it according to the shape of the die. There are two types of drop forging: open-die drop forging and impression-die (or closed-die) drop forging. As the names imply, the difference is in the shape of the die, with the former not fully enclosing the workpiece, while the latter does.

Open-die drop forging
Open-die forging is also known as smith forging. In open-die forging, a hammer strikes and deforms the workpiece, which is placed on a stationary anvil. Open-die forging gets its name from the fact that the dies (the surfaces that are in contact with the workpiece) do not enclose the workpiece, allowing it to flow except where contacted by the dies. The operator therefore needs to orient and position the workpiece to get the desired shape. The dies are usually flat in shape, but some have a specially shaped surface for specialized operations. For example, a die may have a round, concave, or convex surface or be a tool to form holes or be a cut-off tool. Open-die forgings can be worked into shapes which include discs, hubs, blocks, shafts (including step shafts or with flanges), sleeves, cylinders, flats, hexes, rounds, plate, and some custom shapes. Open-die forging lends itself to short runs and is appropriate for art smithing and custom work. In some cases, open-die forging may be employed to rough-shape ingots to prepare them for subsequent operations. Open-die forging may also orient the grain to increase strength in the required direction.

Advantages of open-die forging
"" is the successive deformation of a bar along its length using an open-die drop forge. It is commonly used to work a piece of raw material to the proper thickness. Once the proper thickness is achieved the proper width is achieved via "edging". "" is the process of concentrating material using a concave shaped open-die. The process is called "edging" because it is usually carried out on the ends of the workpiece. "" is a similar process that thins out sections of the forging using a convex shaped die. These processes prepare the workpieces for further forging processes.
 * Reduced chance of voids
 * Better fatigue resistance
 * Improved microstructure
 * Continuous grain flow
 * Finer grain size
 * Greater strength
 * Better response to thermal treatment
 * Improvement of internal quality
 * Greater reliability of mechanical properties, ductility and impact resistance

Impression-die forging
Impression-die forging is also called "closed-die forging". In impression-die forging, the metal is placed in a die resembling a mold, which is attached to an anvil. Usually, the hammer die is shaped as well. The hammer is then dropped on the workpiece, causing the metal to flow and fill the die cavities. The hammer is generally in contact with the workpiece on the scale of milliseconds. Depending on the size and complexity of the part, the hammer may be dropped multiple times in quick succession. Excess metal is squeezed out of the die cavities, forming what is referred to as "flash". The flash cools more rapidly than the rest of the material; this cool metal is stronger than the metal in the die, so it helps prevent more flash from forming. This also forces the metal to completely fill the die cavity. After forging, the flash is removed.

In commercial impression-die forging, the workpiece is usually moved through a series of cavities in a die to get from an ingot to the final form. The first impression is used to distribute the metal into the rough shape in accordance to the needs of later cavities; this impression is called an "edging", "fullering", or "bending" impression. The following cavities are called "blocking" cavities, in which the piece is working into a shape that more closely resembles the final product. These stages usually impart the workpiece with generous bends and large fillets. The final shape is forged in a "final" or "finisher" impression cavity. If there is only a short run of parts to be done, then it may be more economical for the die to lack a final impression cavity and instead machine the final features.

Impression-die forging has been improved in recent years through increased automation which includes induction heating, mechanical feeding, positioning and manipulation, and the direct heat treatment of parts after forging. One variation of impression-die forging is called "flashless forging", or "true closed-die forging". In this type of forging, the die cavities are completely closed, which keeps the workpiece from forming flash. The major advantage to this process is that less metal is lost to flash. Flash can account for 20 to 45% of the starting material. The disadvantages of this process include additional cost due to a more complex die design and the need for better lubrication and workpiece placement.

There are other variations of part formation that integrate impression-die forging. One method incorporates casting a forging preform from liquid metal. The casting is removed after it has solidified, but while still hot. It is then finished in a single cavity die. The flash is trimmed, then the part is quench hardened. Another variation follows the same process as outlined above, except the preform is produced by the spraying deposition of metal droplets into shaped collectors (similar to the Osprey process).

Closed-die forging has a high initial cost due to the creation of dies and required design work to make working die cavities. However, it has low recurring costs for each part, thus forgings become more economical with greater production volume. This is one of the major reasons closed-die forgings are often used in the automotive and tool industries. Another reason forgings are common in these industrial sectors is that forgings generally have about a 20 percent higher strength-to-weight ratio compared to cast or machined parts of the same material.

Design of impression-die forgings and tooling
Forging dies are usually made of high-alloy or tool steel. Dies must be impact- and wear-resistant, maintain strength at high temperatures, and have the ability to withstand cycles of rapid heating and cooling. In order to produce a better, more economical die the following standards are maintained:
 * The dies part along a single, flat plane whenever possible. If not, the parting plane follows the contour of the part.
 * The parting surface is a plane through the center of the forging and not near an upper or lower edge.
 * Adequate draft is provided; usually at least 3° for aluminium and 5° to 7° for steel.
 * Generous fillets and radii are used.
 * Ribs are low and wide.
 * The various sections are balanced to avoid extreme difference in metal flow.
 * Full advantage is taken of fiber flow lines.
 * Dimensional tolerances are not closer than necessary.

Barrelling occurs when, due to friction between the work piece and the die or punch, the work piece bulges at its centre in such a way as to resemble a barrel. This leads to the central part of the work piece to come in contact with the sides of the die sooner than if there were no friction present, creating a much greater increase in the pressure required for the punch to finish the forging.

The dimensional tolerances of a steel part produced using the impression-die forging method are outlined in the table below. The dimensions across the parting plane are affected by the closure of the dies, and are therefore dependent on die wear and the thickness of the final flash. Dimensions that are completely contained within a single die segment or half can be maintained at a significantly greater level of accuracy. A lubricant is used when forging to reduce friction and wear. It is also used as a thermal barrier to restrict heat transfer from the workpiece to the die. Finally, the lubricant acts as a parting compound to prevent the part from sticking in the dies.

Press forging
Press forging works by slowly applying a continuous pressure or force, which differs from the near-instantaneous impact of drop-hammer forging. The amount of time the dies are in contact with the workpiece is measured in seconds (as compared to the milliseconds of drop-hammer forges). The press forging operation can be done either cold or hot.

The main advantage of press forging, as compared to drop-hammer forging, is its ability to deform the complete workpiece. Drop-hammer forging usually only deforms the surfaces of the work piece in contact with the hammer and anvil; the interior of the workpiece will stay relatively undeformed. Another advantage to the process includes the knowledge of the new part's strain rate. By controlling the compression rate of the press forging operation, the internal strain can be controlled.

There are a few disadvantages to this process, most stemming from the workpiece being in contact with the dies for such an extended period of time. The operation is a time-consuming process due to the amount and length of steps. The workpiece will cool faster because the dies are in contact with workpiece; the dies facilitate drastically more heat transfer than the surrounding atmosphere. As the workpiece cools it becomes stronger and less ductile, which may induce cracking if deformation continues. Therefore, heated dies are usually used to reduce heat loss, promote surface flow, and enable the production of finer details and closer tolerances. The workpiece may also need to be reheated.

When done in high productivity, press forging is more economical than hammer forging. The operation also creates closer tolerances. In hammer forging a lot of the work is absorbed by the machinery; when in press forging, the greater percentage of work is used in the work piece. Another advantage is that the operation can be used to create any size part because there is no limit to the size of the press forging machine. New press forging techniques have been able to create a higher degree of mechanical and orientation integrity. By the constraint of oxidation to the outer layers of the part, reduced levels of microcracking occur in the finished part.

Press forging can be used to perform all types of forging, including open-die and impression-die forging. Impression-die press forging usually requires less draft than drop forging and has better dimensional accuracy. Also, press forgings can often be done in one closing of the dies, allowing for easy automation.

Upset forging
Upset forging increases the diameter of the workpiece by compressing its length. Based on number of pieces produced, this is the most widely used forging process. A few examples of common parts produced using the upset forging process are engine valves, couplings, bolts, screws, and other fasteners.

Upset forging is usually done in special high-speed machines called crank presses. The machines are usually set up to work in the horizontal plane, to facilitate the quick exchange of workpieces from one station to the next, but upsetting can also be done in a vertical crank press or a hydraulic press. The initial workpiece is usually wire or rod, but some machines can accept bars up to 25 cm in diameter and a capacity of over 1000 tons. The standard upsetting machine employs split dies that contain multiple cavities. The dies open enough to allow the workpiece to move from one cavity to the next; the dies then close and the heading tool, or ram, then moves longitudinally against the bar, upsetting it into the cavity. If all of the cavities are utilized on every cycle, then a finished part will be produced with every cycle, which makes this process advantageous for mass production.

These rules must be followed when designing parts to be upset forged:
 * The length of unsupported metal that can be upset in one blow without injurious buckling should be limited to three times the diameter of the bar.
 * Lengths of stock greater than three times the diameter may be upset successfully, provided that the diameter of the upset is not more than 1.5 times the diameter of the stock.
 * In an upset requiring stock length greater than three times the diameter of the stock, and where the diameter of the cavity is not more than 1.5 times the diameter of the stock, the length of unsupported metal beyond the face of the die must not exceed the diameter of the bar.

Automatic hot forging
The automatic hot forging process involves feeding mill-length steel bars (typically 7 m long) into one end of the machine at room temperature and hot forged products emerge from the other end. This all occurs rapidly; small parts can be made at a rate of 180 parts per minute (ppm) and larger can be made at a rate of 90 ppm. The parts can be solid or hollow, round or symmetrical, up to 6 kg, and up to 18 cm in diameter. The main advantages to this process are its high output rate and ability to accept low-cost materials. Little labor is required to operate the machinery.

There is no flash produced so material savings are between 20 and 30% over conventional forging. The final product is a consistent 1050 °C so air cooling will result in a part that is still easily machinable (the advantage being the lack of annealing required after forging). Tolerances are usually ±0.3 mm, surfaces are clean, and draft angles are 0.5 to 1°. Tool life is nearly double that of conventional forging because contact times are on the order of 0.06-second. The downside is that this process is only feasible on smaller symmetric parts and cost; the initial investment can be over $10 million, so large quantities are required to justify this process.

The process starts by heating the bar to 1200 to 1300 C in less than 60 seconds using high-power induction coils. It is then descaled with rollers, sheared into blanks, and transferred through several successive forming stages, during which it is upset, preformed, final forged, and pierced (if necessary). This process can also be coupled with high-speed cold-forming operations. Generally, the cold forming operation will do the finishing stage so that the advantages of cold-working can be obtained, while maintaining the high speed of automatic hot forging.

Examples of parts made by this process are: wheel hub unit bearings, transmission gears, tapered roller bearing races, stainless steel coupling flanges, and neck rings for liquid propane (LP) gas cylinders. Manual transmission gears are an example of automatic hot forging used in conjunction with cold working.

Roll forging
Roll forging is a process where round or flat bar stock is reduced in thickness and increased in length. Roll forging is performed using two cylindrical or semi-cylindrical rolls, each containing one or more shaped grooves. A heated bar is inserted into the rolls and when it hits a spot the rolls rotate and the bar is progressively shaped as it is rolled through the machine. The piece is then transferred to the next set of grooves or turned around and reinserted into the same grooves. This continues until the desired shape and size is achieved. The advantage of this process is there is no flash and it imparts a favorable grain structure into the workpiece.

Examples of products produced using this method include axles, tapered levers and leaf springs.

Net-shape and near-net-shape forging
This process is also known as precision forging. It was developed to minimize cost and waste associated with post-forging operations. Therefore, the final product from a precision forging needs little or no final machining. Cost savings are gained from the use of less material, and thus less scrap, the overall decrease in energy used, and the reduction or elimination of machining. Precision forging also requires less of a draft, 1° to 0°. The downside of this process is its cost, therefore it is only implemented if significant cost reduction can be achieved.

Cold forging
Near net shape forging is most common when parts are forged without heating the slug, bar or billet. Aluminum is a common material that can be cold forged depending on final shape. Lubrication of the parts being formed is critical to increase the life of the mating dies.

Induction forging
Unlike the above processes, induction forging is based on the type of heating style used. Many of the above processes can be used in conjunction with this heating method.

Multidirectional forging
Multidirectional forging is forming of a work piece in a single step in several directions. The multidirectional forming takes place through constructive measures of the tool. The vertical movement of the press ram is redirected using wedges which distributes and redirects the force of the forging press in horizontal directions.

Isothermal forging
Isothermal forging is a process by which the materials and the die are heated to the same temperature (iso- meaning "equal"). Adiabatic heating is used to assist in the deformation of the material, meaning the strain rates are highly controlled. This technique is commonly used for forging aluminium, which has a lower forging temperature than steels. Forging temperatures for aluminum are around 430 C, while steels and super alloys can be 930 to 1260 C.

Benefits:
 * Near net shapes which lead to lower machining requirements and therefore lower scrap rates
 * Reproducibility of the part
 * Due to the lower heat loss smaller machines can be used to make the forging

Disadvantages:
 * Higher die material costs to handle temperatures and pressures
 * Uniform heating systems are required
 * Protective atmospheres or vacuum to reduce oxidation of the dies and material
 * Low production rates

Forging of steel
Depending on the forming temperature steel forging can be divided into:

 * Hot forging of steel
 * Forging temperatures above the recrystallization temperature between 950–1250 °C
 * Good formability
 * Low forming forces
 * Constant tensile strength of the workpieces
 * Warm forging of steel
 * Forging temperatures between 750–950 °C
 * Less or no scaling at the workpiece surface
 * Narrower tolerances achievable than in hot forging
 * Limited formability and higher forming forces than for hot forging
 * Lower forming forces than in cold forming
 * Cold forging of steel
 * Forging temperatures at room conditions, self-heating up to 150 °C due to the forming energy
 * Narrowest tolerances achievable
 * No scaling at workpiece surface
 * Increase of strength and decrease of ductility due to strain hardening
 * Low formability and high forming forces are necessary

For industrial processes steel alloys are primarily forged in hot condition. Brass, bronze, copper, precious metals and their alloys are manufactured by cold forging processes; each metal requires a different forging temperature.

Forging of aluminium

 * Aluminium forging is performed at a temperature range between 350–550 °C
 * Forging temperatures above 550 °C are too close to the solidus temperature of the alloys and lead in conjunction with varying effective strains to unfavorable workpiece surfaces and potentially to a partial melting as well as fold formation.
 * Forging temperatures below 350 °C reduce formability by increasing the yield stress, which can lead to unfilled dies, cracking at the workpiece surface and increased die forces

Due to the narrow temperature range and high thermal conductivity, aluminium forging can only be realized in a particular process window. To provide good forming conditions a homogeneous temperature distribution in the entire workpiece is necessary. Therefore, the control of the tool temperature has a major influence to the process. For example, by optimizing the preform geometries the local effective strains can be influenced to reduce local overheating for a more homogeneous temperature distribution.

Application of aluminium forged parts
High-strength aluminium alloys have the tensile strength of medium strong steel alloys while providing significant weight advantages. Therefore, aluminium forged parts are mainly used in aerospace, automotive industry and many other fields of engineering especially in those fields, where highest safety standards against failure by abuse, by shock or vibratory stresses are needed. Such parts are for example pistons, chassis parts, steering components and brake parts. Commonly used alloys are AlSi1MgMn (EN AW-6082) and AlZnMgCu1,5 (EN AW-7075). About 80% of all aluminium forged parts are made of AlSi1MgMn. The high-strength alloy AlZnMgCu1,5 is mainly used for aerospace applications.

Forging of magnesium

 * Magnesium forging occurs at a temperature range between 290–450 °C

Magnesium alloys are more difficult to forge due to their low plasticity, low sensitivity to strain rates and narrow forming temperature. Using semi-open die hot forging with a three-slide forging press (TSFP) has become a newly developed forging method for Mg-Al alloy AZ31, commonly used in forming aircraft brackets. This forging method has shown to improve tensile properties but lacks uniform grain size. Even though the application of magnesium alloys increases by 15–20% each year in the aerospace and automotive industry, forging magnesium alloys with specialized dies is expensive and an unfeasible method to produce parts for a mass market. Instead, most magnesium alloy parts for industry are produced by casting methods.

Equipment
The most common type of forging equipment is the hammer and anvil. Principles behind the hammer and anvil are still used today in drop-hammer equipment. The principle behind the machine is simple: raise the hammer and drop it or propel it into the workpiece, which rests on the anvil. The main variations between drop-hammers are in the way the hammer is powered; the most common being air and steam hammers. Drop-hammers usually operate in a vertical position. The main reason for this is excess energy (energy that is not used to deform the workpiece) that is not released as heat or sound needs to be transmitted to the foundation. Moreover, a large machine base is needed to absorb the impacts.

To overcome some shortcomings of the drop-hammer, the counterblow machine or impactor is used. In a counterblow machine both the hammer and anvil move and the workpiece is held between them. Here excess energy becomes recoil. This allows the machine to work horizontally and have a smaller base. Other advantages include less noise, heat and vibration. It also produces a distinctly different flow pattern. Both of these machines can be used for open-die or closed-die forging.

Forging presses
A forging press, often just called a press, is used for press forging. There are two main types: mechanical and hydraulic presses. Mechanical presses function by using cams, cranks and/or toggles to produce a preset (a predetermined force at a certain location in the stroke) and reproducible stroke. Due to the nature of this type of system, different forces are available at different stroke positions. Mechanical presses are faster than their hydraulic counterparts (up to 50 strokes per minute). Their capacities range from 3 to 160 MN (300 to 18,000 short tons-force). Hydraulic presses, such as the four-die device, use fluid pressure and a piston to generate force. The advantages of a hydraulic press over a mechanical press are its flexibility and greater capacity. The disadvantages include a slower, larger, and costlier machine to operate.

The roll forging, upsetting, and automatic hot forging processes all use specialized machinery.

title: Forging


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Heat treating

Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve the desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, carburizing, normalizing and quenching. Although the term heat treatment applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.

Physical processes

Metallic materials consist of a microstructure of small crystals called "grains" or crystallites. The nature of the grains (i.e. grain size and composition) is one of the most effective factors that can determine the overall mechanical behavior of the metal. Heat treatment provides an efficient way to manipulate the properties of the metal by controlling the rate of diffusion and the rate of cooling within the microstructure. Heat treating is often used to alter the mechanical properties of a metallic alloy, manipulating properties such as the hardness, strength, toughness, ductility, and elasticity.

There are two mechanisms that may change an alloy's properties during heat treatment: the formation of martensite causes the crystals to deform intrinsically, and the diffusion mechanism causes changes in the homogeneity of the alloy.

The crystal structure consists of atoms that are grouped in a very specific arrangement, called a lattice. In most elements, this order will rearrange itself, depending on conditions like temperature and pressure. This rearrangement called allotropy or polymorphism, may occur several times, at many different temperatures for a particular metal. In alloys, this rearrangement may cause an element that will not normally dissolve into the base metal to suddenly become soluble, while a reversal of the allotropy will make the elements either partially or completely insoluble.

When in the soluble state, the process of diffusion causes the atoms of the dissolved element to spread out, attempting to form a homogenous distribution within the crystals of the base metal. If the alloy is cooled to an insoluble state, the atoms of the dissolved constituents (solutes) may migrate out of the solution. This type of diffusion, called precipitation, leads to nucleation, where the migrating atoms group together at the grain-boundaries. This forms a microstructure generally consisting of two or more distinct phases. For instance, steel that has been heated above the austenizing temperature (red to orange-hot, or around 1500 F to 1600 F depending on carbon content), and then cooled slowly, forms a laminated structure composed of alternating layers of ferrite and cementite, becoming soft pearlite. After heating the steel to the austenite phase and then quenching it in water, the microstructure will be in the martensitic phase. This is due to the fact that the steel will change from the austenite phase to the martensite phase after quenching. Some pearlite or ferrite may be present if the quench did not rapidly cool off all the steel.

Unlike iron-based alloys, most heat-treatable alloys do not experience a ferrite transformation. In these alloys, the nucleation at the grain-boundaries often reinforces the structure of the crystal matrix. These metals harden by precipitation. Typically a slow process, depending on temperature, this is often referred to as "age hardening".

Many metals and non-metals exhibit a martensite transformation when cooled quickly (with external media like oil, polymer, water, etc.). When a metal is cooled very quickly, the insoluble atoms may not be able to migrate out of the solution in time. This is called a "diffusionless transformation." When the crystal matrix changes to its low-temperature arrangement, the atoms of the solute become trapped within the lattice. The trapped atoms prevent the crystal matrix from completely changing into its low-temperature allotrope, creating shearing stresses within the lattice. When some alloys are cooled quickly, such as steel, the martensite transformation hardens the metal, while in others, like aluminum, the alloy becomes softer.

Effects of composition
The specific composition of an alloy system will usually have a great effect on the results of heat treating. If the percentage of each constituent is just right, the alloy will form a single, continuous microstructure upon cooling. Such a mixture is said to be eutectoid. However, If the percentage of the solutes varies from the eutectoid mixture, two or more different microstructures will usually form simultaneously. A hypo eutectoid solution contains less of the solute than the eutectoid mix, while a hypereutectoid solution contains more.

Eutectoid alloys
A eutectoid (eutectic-like) alloy is similar in behavior to a eutectic alloy. A eutectic alloy is characterized by having a single melting point. This melting point is lower than that of any of the constituents, and no change in the mixture will lower the melting point any further. When a molten eutectic alloy is cooled, all of the constituents will crystallize into their respective phases at the same temperature.

A eutectoid alloy is similar, but the phase change occurs, not from a liquid, but from a solid solution. Upon cooling a eutectoid alloy from the solution temperature, the constituents will separate into different crystal phases, forming a single microstructure. A eutectoid steel, for example, contains 0.77% carbon. Upon cooling slowly, the solution of iron and carbon (a single phase called austenite) will separate into platelets of the phases ferrite and cementite. This forms a layered microstructure called pearlite.

Since pearlite is harder than iron, the degree of softness achievable is typically limited to that produced by the pearlite. Similarly, the hardenability is limited by the continuous martensitic microstructure formed when cooled very fast.

Hypoeutectoid alloys
A hypoeutectic alloy has two separate melting points. Both are above the eutectic melting point for the system but are below the melting points of any constituent forming the system. Between these two melting points, the alloy will exist as part solid and part liquid. The constituent with the higher melting point will solidify first. When completely solidified, a hypoeutectic alloy will often be in a solid solution.

Similarly, a hypoeutectoid alloy has two critical temperatures, called "arrests". Between these two temperatures, the alloy will exist partly as the solution and partly as a separate crystallizing phase, called the "pro eutectoid phase". These two temperatures are called the upper (A3) and lower (A1) transformation temperatures. As the solution cools from the upper transformation temperature toward an insoluble state, the excess base metal will often be forced to "crystallize-out", becoming the pro eutectoid. This will occur until the remaining concentration of solutes reaches the eutectoid level, which will then crystallize as a separate microstructure.

For example, a hypoeutectoid steel contains less than 0.77% carbon. Upon cooling a hypoeutectoid steel from the austenite transformation temperature, small islands of proeutectoid-ferrite will form. These will continue to grow and the carbon will recede until the eutectoid concentration in the rest of the steel is reached. This eutectoid mixture will then crystallize as a microstructure of pearlite. Since ferrite is softer than pearlite, the two microstructures combine to increase the ductility of the alloy. Consequently, the hardenability of the alloy is lowered.

Hypereutectoid alloys
A hypereutectic alloy also has different melting points. However, between these points, it is the constituent with the higher melting point that will be solid. Similarly, a hypereutectoid alloy has two critical temperatures. When cooling a hypereutectoid alloy from the upper transformation temperature, it will usually be the excess solutes that crystallize-out first, forming the pro-eutectoid. This continues until the concentration in the remaining alloy becomes eutectoid, which then crystallizes into a separate microstructure.

A hypereutectoid steel contains more than 0.77% carbon. When slowly cooling hypereutectoid steel, the cementite will begin to crystallize first. When the remaining steel becomes eutectoid in composition, it will crystallize into pearlite. Since cementite is much harder than pearlite, the alloy has greater hardenability at a cost in ductility.

Effects of time and temperature

Proper heat treating requires precise control over temperature, time held at a certain temperature and cooling rate. With the exception of stress-relieving, tempering, and aging, most heat treatments begin by heating an alloy beyond a certain transformation, or arrest (A), temperature. This temperature is referred to as an "arrest" because at the A temperature the metal experiences a period of hysteresis. At this point, all of the heat energy is used to cause the crystal change, so the temperature stops rising for a short time (arrests) and then continues climbing once the change is complete. Therefore, the alloy must be heated above the critical temperature for a transformation to occur. The alloy will usually be held at this temperature long enough for the heat to completely penetrate the alloy, thereby bringing it into a complete solid solution. Iron, for example, has four critical-temperatures, depending on carbon content. Pure iron in its alpha (room temperature) state changes to nonmagnetic gamma-iron at its A2 temperature, and weldable delta-iron at its A4 temperature. However, as carbon is added, becoming steel, the A2 temperature splits into the A3 temperature, also called the austenizing temperature (all phases become austenite, a solution of gamma iron and carbon) and its A1 temperature (austenite changes into pearlite upon cooling). Between these upper and lower temperatures the pro eutectoid phase forms upon cooling.

Because a smaller grain size usually enhances mechanical properties, such as toughness, shear strength and tensile strength, these metals are often heated to a temperature that is just above the upper critical temperature, in order to prevent the grains of solution from growing too large. For instance, when steel is heated above the upper critical-temperature, small grains of austenite form. These grow larger as the temperature is increased. When cooled very quickly, during a martensite transformation, the austenite grain-size directly affects the martensitic grain-size. Larger grains have large grain-boundaries, which serve as weak spots in the structure. The grain size is usually controlled to reduce the probability of breakage.

The diffusion transformation is very time-dependent. Cooling a metal will usually suppress the precipitation to a much lower temperature. Austenite, for example, usually only exists above the upper critical temperature. However, if the austenite is cooled quickly enough, the transformation may be suppressed for hundreds of degrees below the lower critical temperature. Such austenite is highly unstable and, if given enough time, will precipitate into various microstructures of ferrite and cementite. The cooling rate can be used to control the rate of grain growth or can even be used to produce partially martensitic microstructures. However, the martensite transformation is time-independent. If the alloy is cooled to the martensite transformation (Ms) temperature before other microstructures can fully form, the transformation will usually occur at just under the speed of sound.

When austenite is cooled but kept above the martensite start temperature Ms so that a martensite transformation does not occur, the austenite grain size will have an effect on the rate of nucleation, but it is generally temperature and the rate of cooling that controls the grain size and microstructure. When austenite is cooled extremely slowly, it will form large ferrite crystals filled with spherical inclusions of cementite. This microstructure is referred to as "sphereoidite". If cooled a little faster, then coarse pearlite will form. Even faster, and fine pearlite will form. If cooled even faster, bainite will form, with more complete bainite transformation occurring depending on the time held above martensite start Ms. Similarly, these microstructures will also form, if cooled to a specific temperature and then held there for a certain time.

Most non-ferrous alloys are also heated in order to form a solution. Most often, these are then cooled very quickly to produce a martensite transformation, putting the solution into a supersaturated state. The alloy, being in a much softer state, may then be cold worked. This causes work hardening that increases the strength and hardness of the alloy. Moreover, the defects caused by plastic deformation tend to speed up precipitation, increasing the hardness beyond what is normal for the alloy. Even if not cold worked, the solutes in these alloys will usually precipitate, although the process may take much longer. Sometimes these metals are then heated to a temperature that is below the lower critical (A1) temperature, preventing recrystallization, in order to speed-up the precipitation.

Types of heat treatment

Complex heat treating schedules, or "cycles", are often devised by metallurgists to optimize an alloy's mechanical properties. In the aerospace industry, a superalloy may undergo five or more different heat treating operations to develop the desired properties. This can lead to quality problems depending on the accuracy of the furnace's temperature controls and timer. These operations can usually be divided into several basic techniques.

Annealing
Annealing consists of heating a metal to a specific temperature and then cooling at a rate that will produce a refined microstructure, either fully or partially separating the constituents. The rate of cooling is generally slow. Annealing is most often used to soften a metal for cold working, to improve machinability, or to enhance properties like electrical conductivity.

In ferrous alloys, annealing is usually accomplished by heating the metal beyond the upper critical temperature and then cooling very slowly, resulting in the formation of pearlite. In both pure metals and many alloys that cannot be heat treated, annealing is used to remove the hardness caused by cold working. The metal is heated to a temperature where recrystallization can occur, thereby repairing the defects caused by plastic deformation. In these metals, the rate of cooling will usually have little effect. Most non-ferrous alloys that are heat-treatable are also annealed to relieve the hardness of cold working. These may be slowly cooled to allow full precipitation of the constituents and produce a refined microstructure.

Ferrous alloys are usually either "full annealed" or "process annealed". Full annealing requires very slow cooling rates, in order to form coarse pearlite. In process annealing, the cooling rate may be faster; up to, and including normalizing. The main goal of process annealing is to produce a uniform microstructure. Non-ferrous alloys are often subjected to a variety of annealing techniques, including "recrystallization annealing", "partial annealing", "full annealing", and "final annealing". Not all annealing techniques involve recrystallization, such as stress relieving.

Normalizing
Normalizing is a technique used to provide uniformity in grain size and composition (equiaxed crystals) throughout an alloy. The term is often used for ferrous alloys that have been austenitized and then cooled in the open air. Normalizing not only produces pearlite but also martensite and sometimes bainite, which gives harder and stronger steel but with less ductility for the same composition than full annealing.

In the normalizing process the steel is heated to about 40 degrees Celsius above its upper critical temperature limit, held at this temperature for some time, and then cooled in air.

Stress relieving
Stress-relieving is a technique to remove or reduce the internal stresses created in metal. These stresses may be caused in a number of ways, ranging from cold working to non-uniform cooling. Stress-relieving is usually accomplished by heating a metal below the lower critical temperature and then cooling uniformly. Stress relieving is commonly used on items like air tanks, boilers and other pressure vessels, to remove a portion of the stresses created during the welding process.

Aging
Some metals are classified as precipitation hardening metals. When a precipitation hardening alloy is quenched, its alloying elements will be trapped in solution, resulting in a soft metal. Aging a "solutionized" metal will allow the alloying elements to diffuse through the microstructure and form intermetallic particles. These intermetallic particles will nucleate and fall out of the solution and act as a reinforcing phase, thereby increasing the strength of the alloy. Alloys may age " naturally" meaning that the precipitates form at room temperature, or they may age "artificially" when precipitates only form at elevated temperatures. In some applications, naturally aging alloys may be stored in a freezer to prevent hardening until after further operations - assembly of rivets, for example, maybe easier with a softer part.

Examples of precipitation hardening alloys include 2000 series, 6000 series, and 7000 series aluminium alloy, as well as some superalloys and some stainless steels. Steels that harden by aging are typically referred to as maraging steels, from a combination of the term "martensite aging".

Quenching
Quenching is a process of cooling a metal at a rapid rate. This is most often done to produce a martensite transformation. In ferrous alloys, this will often produce a harder metal, while non-ferrous alloys will usually become softer than normal.

To harden by quenching, a metal (usually steel or cast iron) must be heated above the upper critical temperature (Steel: above 815~900 Degress Celsius ) and then quickly cooled. Depending on the alloy and other considerations (such as concern for maximum hardness vs. cracking and distortion), cooling may be done with forced air or other gases, (such as nitrogen). Liquids may be used, due to their better thermal conductivity, such as oil, water, a polymer dissolved in water, or a brine. Upon being rapidly cooled, a portion of austenite (dependent on alloy composition) will transform to martensite, a hard, brittle crystalline structure. The quenched hardness of a metal depends on its chemical composition and quenching method. Cooling speeds, from fastest to slowest, go from brine, polymer (i.e. mixtures of water + glycol polymers), freshwater, oil, and forced air. However, quenching certain steel too fast can result in cracking, which is why high-tensile steels such as AISI 4140 should be quenched in oil, tool steels such as ISO 1.2767 or H13 hot work tool steel should be quenched in forced air, and low alloy or medium-tensile steels such as XK1320 or AISI 1040 should be quenched in brine.

Some Beta titanium based alloys have also shown similar trends of increased strength through rapid cooling. However, most non-ferrous metals, like alloys of copper, aluminum, or nickel, and some high alloy steels such as austenitic stainless steel (304, 316), produce an opposite effect when these are quenched: they soften. Austenitic stainless steels must be quenched to become fully corrosion resistant, as they work-harden significantly.

Tempering
Untempered martensitic steel, while very hard, is too brittle to be useful for most applications. A method for alleviating this problem is called tempering. Most applications require that quenched parts be tempered. Tempering consists of heating steel below the lower critical temperature, (often from 400˚F to 1105˚F or 205˚C to 595˚C, depending on the desired results), to impart some toughness. Higher tempering temperatures (maybe up to 1,300˚F or 700˚C, depending on the alloy and application) are sometimes used to impart further ductility, although some yield strength is lost.

Tempering may also be performed on normalized steels. Other methods of tempering consist of quenching to a specific temperature, which is above the martensite start temperature, and then holding it there until pure bainite can form or internal stresses can be relieved. These include austempering and martempering.

Tempering colors
Steel that has been freshly ground or polished will form oxide layers when heated. At a very specific temperature, the iron oxide will form a layer with a very specific thickness, causing thin-film interference. This causes colors to appear on the surface of the steel. As the temperature is increased, the iron oxide layer grows in thickness, changing the color. These colors, called tempering colors, have been used for centuries to gauge the temperature of the metal.

 * 350˚F (176˚C), light yellowish
 * 400˚F (204˚C), light-straw
 * 440˚F (226˚C), dark-straw
 * 500˚F (260˚C), brown
 * 540˚F (282˚C), purple
 * 590˚F (310˚C), deep blue
 * 640˚F (337˚C), light blue

The tempering colors can be used to judge the final properties of the tempered steel. Very hard tools are often tempered in the light to the dark straw range, whereas springs are often tempered to the blue. However, the final hardness of the tempered steel will vary, depending on the composition of the steel. Higher-carbon tool steel will remain much harder after tempering than spring steel (of slightly less carbon) when tempered at the same temperature. The oxide film will also increase in thickness over time. Therefore, steel that has been held at 400˚F for a very long time may turn brown or purple, even though the temperature never exceeded that needed to produce a light straw color. Other factors affecting the final outcome are oil films on the surface and the type of heat source used.

Selective heat treating
Many heat treating methods have been developed to alter the properties of only a portion of an object. These tend to consist of either cooling different areas of an alloy at different rates, by quickly heating in a localized area and then quenching, by thermochemical diffusion, or by tempering different areas of an object at different temperatures, such as in differential tempering.

Differential hardening
Some techniques allow different areas of a single object to receive different heat treatments. This is called differential hardening. It is common in high quality knives and swords. The Chinese jian is one of the earliest known examples of this, and the Japanese katana may be the most widely known. The Nepalese Khukuri is another example. This technique uses an insulating layer, like layers of clay, to cover the areas that are to remain soft. The areas to be hardened are left exposed, allowing only certain parts of the steel to fully harden when quenched.

Flame hardening
Flame hardening is used to harden only a portion of the metal. Unlike differential hardening, where the entire piece is heated and then cooled at different rates, in flame hardening, only a portion of the metal is heated before quenching. This is usually easier than differential hardening, but often produces an extremely brittle zone between the heated metal and the unheated metal, as cooling at the edge of this heat-affected zone is extremely rapid.

Induction hardening
Induction hardening is a surface hardening technique in which the surface of the metal is heated very quickly, using a no-contact method of induction heating. The alloy is then quenched, producing a martensite transformation at the surface while leaving the underlying metal unchanged. This creates a very hard, wear-resistant surface while maintaining the proper toughness in the majority of the object. Crankshaft journals are a good example of an induction hardened surface.

Case hardening
Case hardening is a thermochemical diffusion process in which an alloying element, most commonly carbon or nitrogen, diffuses into the surface of a monolithic metal. The resulting interstitial solid solution is harder than the base material, which improves wear resistance without sacrificing toughness.

Laser surface engineering is a surface treatment with high versatility, selectivity and novel properties. Since the cooling rate is very high in laser treatment, metastable even metallic glass can be obtained by this method.

Cold and cryogenic treating
Although quenching steel causes the austenite to transform into martensite, all of the austenite usually does not transform. Some austenite crystals will remain unchanged even after quenching below the martensite finish (Mf) temperature. Further transformation of the austenite into martensite can be induced by slowly cooling the metal to extremely low temperatures. Cold treating generally consists of cooling the steel to around -115˚F (-81˚C), but does not eliminate all of the austenite. Cryogenic treating usually consists of cooling to much lower temperatures, often in the range of -315˚F (-192˚C), to transform most of the austenite into martensite.

Cold and cryogenic treatments are typically done immediately after quenching, before any tempering, and will increase the hardness, wear resistance, and reduce the internal stresses in the metal but, because it is really an extension of the quenching process, it may increase the chances of cracking during the procedure. The process is often used for tools, bearings, or other items that require good wear resistance. However, it is usually only effective in high-carbon or high-alloy steels in which more than 10% austenite is retained after quenching.

Decarburization
The heating of steel is sometimes used as a method to alter the carbon content. When steel is heated in an oxidizing environment, the oxygen combines with the iron to form an iron-oxide layer, which protects the steel from decarburization. When the steel turns to austenite, however, the oxygen combines with iron to form a slag, which provides no protection from decarburization. The formation of slag and scale actually increases decarburization, because the iron oxide keeps oxygen in contact with the decarburization zone even after the steel is moved into an oxygen-free environment, such as the coals of a forge. Thus, the carbon atoms begin combining with the surrounding scale and slag to form both carbon monoxide and carbon dioxide, which is released into the air.

Steel contains a relatively small percentage of carbon, which can migrate freely within the gamma iron. When austenitized steel is exposed to air for long periods of time, the carbon content in the steel can be lowered. This is the opposite from what happens when steel is heated in a reducing environment, in which carbon slowly diffuses further into the metal. In an oxidizing environment, the carbon can readily diffuse outwardly, so austenitized steel is very susceptible to decarburization. This is often used for cast steel, where a high carbon-content is needed for casting, but a lower carbon-content is desired in the finished product. It is often used on cast-irons to produce malleable cast iron, in a process called "white tempering". This tendency to decarburize is often a problem in other operations, such as blacksmithing, where it becomes more desirable to austenize the steel for the shortest amount of time possible to prevent too much decarburization.

Specification of heat treatment
Usually the end condition is specified instead of the process used in heat treatment.

Case hardening

Case hardening is specified by "hardness" and "case depth". The case depth can be specified in two ways: total case depth or effective case depth. The total case depth is the true depth of the case. For most alloys, the effective case depth is the depth of the case that has a hardness equivalent of HRC50; however, some alloys specify a different hardness (40-60 HRC) at effective case depth; this is checked on a Tukon microhardness tester. This value can be roughly approximated as 65% of the total case depth; however, the chemical composition and hardenability can affect this approximation. If neither type of case depth is specified the total case depth is assumed.

For case hardened parts the specification should have a tolerance of at least ±0.005 in. If the part is to be ground after heat treatment, the case depth is assumed to be after grinding.

The Rockwell hardness scale used for the specification depends on the depth of the total case depth, as shown in the table below. Usually, hardness is measured on the Rockwell "C" scale, but the load used on the scale will penetrate through the case if the case is less than 0.030 in. Using Rockwell "C" for a thinner case will result in a false reading.

For cases that are less than 0.015 in thick a Rockwell scale cannot reliably be used, so  is specified instead. File hard is approximately equivalent to 58 HRC.

When specifying the hardness either a range should be given or the minimum hardness specified. If a range is specified at least 5 points should be given.

Through hardening
Only hardness is listed for through hardening. It is usually in the form of HRC with at least a five-point range.

Annealing
The hardness for an annealing process is usually listed on the HRB scale as a maximum value. It is a process to refine grain size, improve strength, remove residual stress, and affect the electromagnetic properties...

Types of furnaces
Furnaces used for heat treatment can be split into two broad categories: batch furnaces and continuous furnaces. Batch furnaces are usually manually loaded and unloaded, whereas continuous furnaces have an automatic conveying system to provide a constant load into the furnace chamber.

Batch furnaces
Batch systems usually consist of an insulated chamber with a steel shell, a heating system, and an access door to the chamber.

Box-type furnace
Many basic box-type furnaces have been upgraded to a semi-continuous batch furnace with the addition of integrated quench tanks and slow-cool chambers. These upgraded furnaces are a very commonly used piece of equipment for heat-treating.

Car-type furnace
Also known as a " bogie hearth", the car furnace is an extremely large batch furnace. The floor is constructed as an insulated movable car that is moved in and out of the furnace for loading and unloading. The car is usually sealed using sand seals or solid seals when in position. Due to the difficulty in getting a sufficient seal, car furnaces are usually used for non-atmosphere processes.

Elevator-type furnace

Similar in type to the car furnace, except that the car and hearth are rolled into position beneath the furnace and raised by means of a motor-driven mechanism, elevator furnaces can handle large heavy loads and often eliminate the need for any external cranes and transfer mechanisms.

Bell-type furnace
Bell furnaces have removable covers called bells, which are lowered over the load and hearth by crane. An inner bell is placed over the hearth and sealed to supply a protective atmosphere. An outer bell is lowered to provide the heat supply.

Pit furnaces
Furnaces that are constructed in a pit and extend to floor level or slightly above are called pit furnaces. Workpieces can be suspended from fixtures, held in baskets, or placed on bases in the furnace. Pit furnaces are suited to heating long tubes, shafts, and rods by holding them in a vertical position. This manner of loading provides minimal distortion.

Salt bath furnaces
Salt baths are used in a wide variety of heat treatment processes including neutral hardening, liquid carburising, liquid nitriding, austempering, martempering and tempering.

Parts are loaded into a pot of molten salt where they are heated by conduction, giving a very readily available source of heat. The core temperature of a part rises in temperature at approximately the same rate as its surface in a salt bath.

Salt baths utilize a variety of salts for heat treatment, with cyanide salts being the most extensively used. Concerns about associated occupation health and safety, and expensive waste management and disposal due to their environmental effects have made the use of salt baths less attractive in recent years. Consequently, many salt baths are being replaced by more environmentally friendly fluidized bed furnaces.

Fluidised bed furnaces
A fluidised bed consists of a cylindrical retort made from high-temperature alloy, filled with sand-like aluminum oxide particulate. Gas (air or nitrogen) is bubbled through the oxide and the sand moves in such a way that it exhibits fluid-like behavior, hence the term fluidized. The solid-solid contact of the oxide gives very high thermal conductivity and excellent temperature uniformity throughout the furnace, comparable to those seen in a salt bath.

title: Heat treating


text:
User:Ahkitj

I am Jonathan Ah Kit, of Lower Hutt, New Zealand, a New Zealand Wikipedian. As such, I usually only speak New Zealand English. I have too many websites for me to remember; they are eventually found from http://www.electric.gen.nz/. E-mail sent to me at [mailto:jonathan@metalab.unc.edu jonathan@metalab.unc.edu] gets to me, subject to my SpamAssassin or whatever spam fighting installation I now use (though lately it seems some of the SMTP servers electric.gen.nz uses have showed up some odd errors for people writing to me at my other email address).

 * *cough* I was at Penn State in 2007.
 * My current work tends to live at http://www.ibiblio.org/ahkitj/ at ibiblio nowadays.

Identity hash information
I am currently 8ba90890762b5a8a4140dbe37ca5afbe987b25ddfc91d011cfbe10bd31f2dae70e43c97679ce877a7b96cab98207535d3f1e21a02d39484704f7e538d6c941cb in SHA-512 speak.

*yawn*

Or, in other words, this, really:

Really old stuff
Most of what is below is from years ago. I am now living in the USA.

I discovered Wikipedia on February 12, 2003, after needing an entry during the course of my studies at the Wellington College of Education. I am now a postgraduate there.

(Yes, I am the hapless author-publisher of ISBN 0-473-09997-7 (catalogue link), a spring break project of mine.)

I have no idea how to pronounce my surname, though there are several misspellings of it going around.

 * I am not a relation of the Northern Territory, Australia politician John Ah Kit, nor his son Jonathan Ah Kit.
 * To confuse things, however, I briefly lived in Darwin. Rather nice place.

My current favourite books are ISBN 0747551006 and, since I got it as a birthday present a few weeks ago, ISBN 0-553-26375-7.

I'm currently reading ISBN 0-908652-15-1. The only computer game I've ever bothered buying in the multiples of decades I've bothered with computer games is ISBN 0-7845-2066-6. What the latter was doing with an ISBN is beyond me, but then I've seen bookmarks with them (my copy of the very readable ISBN 0-415-92607-6 has ISBN 0-7284-2192-X as a fine example of this).

Contributions
By no means is this a complete list. I do bits here and there. Some others from my earlier days.
 * Archives New Zealand (I am listed as making the second edit, but I wrote the first article before I discovered the Wikipedia login box and created myself this username just now)
 * Lower Hutt/Hutt City (added and corrected spellings of some suburbs, and noted that Hutt City's name is still Lower Hutt legally (so has somebody else), though many to my chagrin call it Hutt City now)
 * God Defend New Zealand (added a note on a 1978 official alternative to the original arrangement)
 * New Zealand Wikipedian (added myself)
 * Australia (added myself)
 * complete alphabetical listing (added myself)
 * Wellington College of Education
 * Department of Internal Affairs
 * Treaty of Waitangi (minor grammatical changes)
 * State sector organisations in New Zealand (makeover of article, grabbed data off the SSC website, and merged it with data from some agencies' sites)
 * Air New Zealand and Freedom Air (grammatical corrections and cross links between the two)
 * Provinces of New Zealand – they’re still used today in a minor form, so why not list them? As a result, I added a list of provincial anniversary days. :)
 * On that same tangent, I did a list of New Zealand cities and (historical) provincial districts.
 * I've edited some of the articles pertaining to Niue to familiarise myself for a t-coll assignment.

I've contributed quite a bit of stuff, so obviously not everything is listed here. :)

In case you hadn't noticed, this is modelled on the entry on Carey Evans.

title: User:Ahkitj


text:
Swords, Dublin

Swords ( or Sord Cholmcille) in County Dublin, the county town of the local government area of Fingal, is a large suburban town on the east coast of Ireland, situated ten kilometres north of Dublin city centre. It is the eighth largest urban area in Ireland, with a population of 40,776 as of the 2022 census. The town was reputedly founded c. AD 560. Located on the Ward River, Swords features Swords Castle, a restored medieval castle, a holy well from which it takes its name, a round tower and a Norman tower. Facilities in the area include the Pavilions shopping centre, one of the largest in the Dublin region, a range of civic offices, some light industries, the main storage facility and archive of the National Museum of Ireland and several parks. Dublin Airport is located nearby.

The name "Swords" gives its name to a townland of Swords Demesne, a civil parish, and a local electoral area.

Origins and etymology
The town's origins date back to 560 AD when it was reputedly founded by Saint Colmcille (521–567). Legend has it that the saint blessed a local well, giving the settlement its name, Sord, meaning "clear" or "pure". However, An Sord also means "the water source" and could indicate a large communal drinking well that existed in antiquity. St. Colmcille's Well is located on Well Road off Main Street. Sord may also refer to a "sward", an "expanse of grass". The most common landscape indicators of early Christian settlement are the ecclesiastical enclosures, and in the case of Swords, the street pattern has been influenced by the circular alignment of the settlement.

Development
The medieval town developed in a linear pattern along Main Street, in a roughly north–south direction. The round tower, 26m in height, is also an indicator of early Christian settlement. The Irish high king Brian Boru is said to have had his funeral at the church on Spittal Hill after he was killed at the Battle of Clontarf; this was of course before the hospital and even the Church of Ireland when there would have been a small chapel there along with the round tower.

In medieval times, the manor of Swords was English Crown property, and by tradition was granted to each Archbishop of Dublin for his lifetime.

The parliamentary borough of Swords elected two MPs to the Irish House of Commons. It was disenfranchised in 1801 by the Acts of Union 1800.

At the northern end of the street stands Swords Castle, 200m northeast of the ecclesiastical site, which was built in the early 13th century. A short distance north of the castle is the elevation known as Spittal Hill, where a hospital once stood.

In 1994, Swords became the county town of the new county of Fingal after the abolition of County Dublin as an administrative county. In 2001, upon the completion of the County Hall, senior executive offices moved there from Parnell Square in Dublin city centre.

In June 2006, the RNLI Ireland officially opened a new all-Ireland headquarters at Airside Business Park, within greater Swords. The National Museum of Ireland operates its Collections Resource Centre (CRC) at a former Motorola factory site on the northern edge of the town. The size of two football fields, the CRC includes storage, archive, library and research facilities serving all branches of the museum.

Strategic vision
Fingal County Council's "Strategic Vision" for Swords declared an aim of forming a sustainable "new city"; the council has referred to Swords as an "emerging city" and has projected that the population of Swords would rise towards 100,000 by the year 2035. As of 2023, the town is the eighth-largest urban area in the country.

The Swords Cultural Quarter Masterplan by the county council proposed to redevelop the area surrounding the castle into the Swords Cultural Quarter, and to build a new Cultural Centre within this area. Work on the Cultural Centre began in April 2023, with a view to begin building mid-2024. During the enabling works of the project, two medieval wells were discovered under the existing car park. The wells were removed by archaeologists and preserved for potential display at a later date. The Cultural Centre is proposed to include a new library, art gallery, theatre and café. If implemented as planned, the masterplan would also change the layout of the roads surrounding the castle.

Quality of life
In 2012, Swords was named the third-best town in Ireland to live in. The survey conducted by Retail Excellence Ireland took into account safety, retail, dining, entertainment, events, car parking and the overall attractiveness of the town. Swords has seen steady regeneration of shop fronts, public buildings, and footpaths and the restoration of Swords Castle since the mid-1990s. Households in Swords have the seventh-highest median incomes in the state, among distinct towns (a comparison excluding most other suburbs of the city).

A 2011 Irish Business Against Litter (IBAL) survey declared Swords to be the second cleanest town in Ireland. This came just eight years after an IBAL survey had scored the town as the worst "litter blackspot" in the country. In the 2019 survey, An Taisce, who carry out the surveys on behalf of IBAL, stated: "A stellar showing for this large urban area. Swords is a model for others to follow."

Landscape
Swords is situated roughly in the centre of the modern county of Fingal and the ancient barony of Nethercross. The Ward River, coming from County Meath, runs west to east to near the centre of the town, and then turns to run north, before flowing into the Broad Meadow Water or Broadmeadow River to the east of the town, across the former northern road. A small stream joins the Ward near the town centre and the holy well. The Broadmeadow, also flowing from Meath, borders the north of the town. It runs from Dunshaughlin in the west and across the north of Swords, before receiving the Ward and flowing into the wide Broadmeadow Estuary, then into the Irish Sea past Malahide. The estuary is crossed by a railway embankment and bridge from Malahide. Swords is surrounded by a protected green belt. Dublin Airport has prevented the town from expanding further south and the large Broadmeadow Estuary and Malahide beyond limit expansion further east. To the north and west of Swords, there is sparsely-populated, relatively flat, farmland.

Townlands and baronies
The civil parish of Swords mainly lies in the ancient barony of Nethercross. Swords Demesne is the name of the townland in the heart of the urban town of Swords. It is one of 58 such geographic units in the civil parish. However, a single parcel of land, 5 acres in extent, is situated in the barony of Coolock as an exclave of the civil parish proper.

There are 10 townlands in the electoral division of Swords, which is not coterminous with the civil parish.

Urban layout
The main retail area is located in the centre of the town and includes the town's wide, tree-lined Main Street, and the Pavilions and Swords Central combined shopping centres. There are also two smaller retail developments, Swords Plaza and Swords Town Mall. Most civic facilities are also in this central area, with some subsidiary shopping and civic centres in surrounding housing areas.

The west of the urban area is mainly residential, with the neighbourhoods of Applewood, Rathbeale and Brackenstown to the north of the Ward River and Knocksedan, River Valley, Rathingle, Highfields, and Boroimhe to the south side of the river.

The main business and industrial areas are located to the east of the town centre, along the R132 dual carriageway. These include Balheary Industrial Park, Swords Business Campus, Swords Business Park, and the Airside campus (Business Park, Retail Park and Motor Park). These campuses separate the town centre from the residential neighbourhoods further east — Seatown, Lissenhall, Holywell and Drynam (or Drinan) — for which reason the Central Statistics Office treats the latter areas as forming a separate census town, which since 1991 it has dubbed "Kinsealy–Drinan" and had a population of 7,526 at the 2022 census. The development plan for Fingal County Council treats Kinsealy–Drinan as part of Swords.

Climate
The climate of Swords is, like the rest of Ireland, classified as a maritime temperate climate (Cfb) according to the Köppen climate classification system. It is mild and changeable with abundant rainfall and a lack of temperature extremes. The hottest months of the year are June, July and August with temperatures of around 17 – 20 degrees. Swords gets rainfall all year round and the wettest months are October to January.

Demographics
Swords has developed into the eighth largest urban area in Ireland, with a population of 40,776 at the 2022 census. The town's period of rapid population growth began in the 1970s with the construction of the extensive Rivervalley Estate, then Ireland's largest private housing development, ahead of the Kilnamanagh Estate in Tallaght North. It continued during the 1990s and 2000s, with many new residents moving to the area due to its proximity to work at Dublin Airport and various industrial estates / business parks.

Fingal County Council has referred to Swords as an "Emerging City", and has suggested that the overall area's population may reach 100,000 by 2035.

Roads
Swords has good road links due to its proximity to Dublin city, which is the main focus of the Irish road network. The M1 Dublin–Belfast motorway passes along the eastern edge of the town and is the main route to/from Dublin City, Drogheda, Dundalk, Newry and Belfast. The M50 Dublin semi-orbital motorway passes to the south of the town and provides connections with all of the other main roads out of Dublin (N2, N3, N4, N7, N81 and M11). The R132 dual-carriageway bypasses the centre of Swords, and runs south to Dublin Airport and north to Balbriggan. The proposed Swords Western Ring Road dual carriageway is due to run from the M1 at Lissenhall, north of Swords, along the western edge of Swords to the M2 motorway at Cherryhound. Other main roads from Swords include the R106 to Malahide and Portmarnock, R108 to Ballyboughal and Naul, R125 to Ashbourne and the M2 motorway, R126 to Donabate and Portrane and R127 to Lusk and Skerries.

Bus
The town's Main Street is served by Dublin Bus (and Go-Ahead Ireland) routes 33, 33A, 33B, 33N, 41, 41B, 41C, 41X, 43, 102 and 142 as well as Bus Éireann routes 101 and 101n, and Swords Express routes 500, 500x, 501, 501x and 502. Buses operate between Swords and Dublin city centre approximately every 5 minutes throughout the day, through a combination of Dublin Bus routes 33, 41, 41B, 41C, 41X & 43, with a journey time of about an hour. Swords Express operate express services through the Dublin Port Tunnel which take about 35 minutes. Other bus routes serving Swords include the 102 to Malahide, Portmarnock and Sutton, route 33b to Donabate and Portrane, routes 33 and 33a to Lusk, Rush, Skerries, and Balbriggan and Bus Éireann route 101 to Balbriggan, Julianstown and Drogheda. Connect Bus and Coach operate route H1 every 20 minutes between Dublin Airport and the Travelodge Hotel in Swords.

There are a number of long-distance bus services from the Atrium Road and coach park in Dublin Airport to various locations throughout the country operated by Bus Éireann and other private companies, including 50 daily services to Belfast (route 1/X2 & Aircoach ), 12 to Derry (route 33 & John Mc Ginley ), 11 to Letterkenny (route 32 & John Mc Ginley), 9 to Donegal (route 30), 3 to Sligo (route 23), 1 to Ballina (route 22), 52 to Galway (route 20, Citylink & gobus ), 14 to Limerick (route 12 & JJ Kavanagh ), 24 to Cork (GoBé & Aircoach), 6 to Clonmel (JJ Kavanagh), 21 to Waterford (route 4/X4 & JJ Kavanagh) and 31 to Wexford (route 2, Ardcavan & Wexford Bus ).

Rail
Swords has no railway services. The nearest railway stations are at Malahide and Donabate. Malahide is served by the frequent DART service to Bray, through the city centre. Both Malahide and Donabate are served by Dublin – Drogheda commuter services.

Swords is the only Dublin county town not served by rail, as Tallaght in South Dublin is served by the Luas light rail system, and Dún Laoghaire is served by the DART and Irish Rail services.

Metro
There are proposals for a light rapid transit line, MetroLink, to run from Charlemont to Swords via the Mater Hospital, Glasnevin railway station, Dublin City University, Ballymun and Dublin Airport. As of July 2022, the MetroLink project was proposed to begin construction in and that, "all going well" it could be in operation by 2035.

Dublin Airport
Dublin Airport, the busiest airport in Ireland, is located at Collinstown, several kilometres to the south of Swords. The airport has direct flights to Britain, Europe, North America, North Africa and the Middle East. In 2019, 32.9 million passenger journeys were recorded, and it is by far the busiest of the airports by total passenger traffic in Ireland.

Knocksedan Heliport
Knocksedan Heliport is a private heliport on the western side of Swords, run by Celtic Helicopters. It has four hangars and the operators provide a helicopter wash facility and Jet A1 Fuel. Irish Helicopters also use the heliport. They provide aerial crane, filming and survey services, helicopter charter and maintenance, spraying and special project services.

Features and historical attractions
Some historical attractions are listed below. Many of these are promoted by Swords Historical Society.

Swords Castle
Swords Castle was built as the manorial residence of the 1st Archbishop of Dublin, John Comyn, around 1200 or a little later in Swords, just north of Dublin. It was never strong in the military sense, but covers a large pentagonal walled area of nearly 1.5 acre with a tower on the north and a gateway complex on the south. The adjoining chapel, built in the late thirteenth century, was probably used as the Archbishop's private oratory.

Other buildings, recorded in an inquisition in 1326, have now vanished, including the great hall on the east side of the enclosure. The Archbishop abandoned Swords once a new palace was built at Tallaght in 1324. The stepped battlements suggest some form of occupancy during the fifteenth century, but by 1583, when briefly occupied by Dutch Protestants, it was described as "the quite spoiled old castle". It was used as a garden in the nineteenth century and sold after the Church of Ireland was disestablished.

Swords Castle has undergone restoration and is open as a tourist attraction. The castle was used as a film location for the production of TV series The Tudors in the spring of 2010.

St. Colmcille's Well
On Well Road, also known as St. Columb's Well. In a locked chamber. Reputed to be where Swords got its name when St. Colmcille blessed the well of clear water, 'Sord' being the Irish for 'clear or pure'.

St. Columba's Church, Belfry & Round Tower
The round tower is the surviving remnant of St. Colmcille's monastic settlement. The only remaining relic of the medieval church is its belfry, from c. 1300, which is open to the public in the summertime. The original church is said to have fallen into ruin sometime in the seventeenth century. The new church of early Gothic style was built in 1811 on the foundations of the old. The Sexton's Lodge was built in 1870. The body of Brian Boru was said to have been brought there in 1014 to be waked after the Battle of Clontarf, while on the way to be buried in Armagh. As well as St. Columba's, Swords was served by Cloghran-Swords church, south of the town, up until it was merged with Santry in 1872.

Old Borough School
Located on Main Street, the building was designed by the architect Francis Johnston. In 2015, Wetherspoon bought the premises, and now operates The Old Borough as a public house.

St. Colmcille's Catholic Church
On Chapel Lane, a pre-Catholic Emancipation church was built in 1827 on a site donated by James Taylor of Swords House. The graveyard contains the headstones of nationalist politician Andrew Kettle, who was known as "Parnell's Righthand Man".

Courthouse
Designed by Alexander Tate, Swords Courthouse is located on North Street and was built in 1845 in Classical style.

Lord Mayors
Founded in 1668, the 350-year-old Lord Mayors is a Swords landmark. The thatched-roof pub is the oldest structure in the village.

The Lord mayors closed for business in April 2019 leaving the premises vacant, with some locals questioning the plan to build 172 apartments on the site of the historic structure.

Fingal County Hall
The modern Fingal County Hall, by Bucholz McEvoy Architects, is located at the northern end of Main Street. It is built on the site of Swords House, the home of the Norman family, the Taylors of Swords. Records show the family arrived there in the 13th century and built a 'Mansion House' in 1403.

Swords library
Swords library, located on Rathbeale Road, offers library services and runs cultural activities for children and adults.

Historical society
Swords Historical Society, founded in 1982, is supported by volunteers who have worked to record, promote and preserve the heritage of the greater Swords area. The society's Museum and Heritage Centre at the Carnegie Library on North Street is run by volunteers and is open on weekday afternoons. The society's oral history project has produced an annual 'Swords Voices' publication, which chronicles the memories of local people.

Ward River Valley Park
The Ward River Valley Park is a linear park on the banks of the Ward River approaching town. It covers an area of 89 ha. (220 acres) between Swords town centre and Knocksedan Bridge. Features include some 12th-century fortifications, woodland habitats, wetlands and rolling grassland. There are viewing points, picnic sites, sports pitches and tennis courts. The park is known locally as "The Jacko", which is a nickname that is thought to have originated in the 1960s.

Swords Town Park (with Swords Castle)
Swords Town Park is a small park situated in the centre of the town of Swords, along the Ward River. It has tennis courts and a playground. Swords Castle lies within the park. It is the former residence of the Archbishop of Dublin and it is the only fortified residence of the Archbishop to survive in a reasonable state today (see above).

Balheary Park
Balheary Park is north of the town centre near the confluence of the Broadmeadow River and the Ward River, which flow to the northern and southern edges of the park. It meets Swords Business Campus / Balheary Business Park on three sides and has some playing pitches which are used by the Fingallians GAA club. In mid-2006, Fingal County Council built a skatepark and adjoining basketball courts/football court in Balheary Park. The park contains a bowl, a vert wall, a spine, some quarterpipes, and a section of boxes in the middle of the park.

Broadmeadow River Linear Park
The Broadmeadow Linear Park is a small park north of Applewood along the Broadmeadow River. Fingal County Council plan to extend the park eastwards to Balheary Park and westwards into the proposed Swords Regional Park.

National Show Centre
A little south of Swords, near Dublin Airport, the National Show Centre is an exhibition and conference venue owned by the Irish Kennel Club. The venue is used as a counting centre during elections for the Dublin Fingal constituency.

Boxing
Swords Boxing Club is based at Sluagh Hall, a former military facility which is shared with Fingallians GAA club. Fingal Boxing Academy, which is affiliated with the Irish Amateur Boxing Association and located in Rivervalley, Swords, was the first boxing club in Ireland to train female boxers and has trained several national champions.

GAA
There are three Gaelic Athletic Association clubs local to Swords, and one more with pitches. These include Fingallians (based at Lawless Memorial Park), St. Finian's (Rivervalley), and St Colmcille's (Holybanks, Glen Ellan Road in the Applewood neighbourhood).

Golf
There are several golf courses close to the town, namely Swords Open Golf Course, Forrest Little Golf Club, Roganstown Golf and Country Club and Balheary "Par 3" Golf Course. There are also several driving ranges in the area with the Drynam Golf Centre being the first driving range in Ireland with automated tees.

Rugby
Swords RFC are a rugby union team playing in Division 3 of the Leinster League. The club is based out of ALSAA Sports Complex beside the airport and has 2 Men's teams and 1 Women's team.

Soccer
Swords Celtic, established in 1962, fields DDSL, NDSL, LSL, and MGL schoolboy and schoolgirl teams. The main pitch and clubhouse are located at Balheary, Swords and include dressing rooms an eleven-a-side and two seven-a-side pitches with floodlights.

Swords Manor FC, established in 1995, fields NDSL, DDSL, MGL, and UCFL schoolboy and schoolgirl teams. The main pitch and clubhouse are located on Brackenstown Road.

River Valley Rangers AFC was established in 1981. It fields NDSL schoolboy/girl teams and its pitch and clubhouse are located in Ridgewood Park.

Columbas Rovers FC was established in 2002. It uses the ALSAA sports centre near the airport.

A former club, Swords Rovers FC (founded in 1993), was disbanded in 2015.

Dublin Airport Football Club, formerly known as Aer Rianta Soccer Club, was formed in 1972. The club is based in the ALSAA Sports Complex, Dublin Airport and comepetes in the Leinster Senior League.

Other sports
Fingal Orienteers have created orienteering maps of the Ward River Valley park, and the surrounding estates of Swords Manor, Brackenstown, River Valley and Knocksedan, and regularly hold events in the area.

Racquet sports clubs include Forest Badminton Club, River Valley Badminton Club, and Swords Tennis Club (based at Swords Town Park). Swords Hockey Club is a ladies club based in ALSAA Sports Grounds.

Horticultural and agricultural shows
The Fingal Horticultural Society holds their annual flower show in Swords every August. It includes competition classes in cut flowers, flower arranging, cookery, wine making, photography, painting and handcrafts.

The Flavours of Fingal agricultural show first took place in July 2012 in Newbridge House near Donabate. The farm section of the two-day show featured a program of livestock and sheep competitions, equestrian contests and other agricultural displays. Separately, the walled garden of Newbridge House hosted the food producers section of the show.

Dog shows
In 2012 over 80 dog shows were held in the National Show Centre, including the Celtic Winners Dog Show, held on St. Patrick's Day.

Fingal 10k Road Race
The first Fingal 10k Road Race took place on 22 July 2012 on the roads around Swords. It was part of the Dublin Race Series, a series which culminates in the Dublin Marathon. Over 4200 people entered the first race, and the event has since been run annually.

Commercial and retail
Swords is the home to a large retail and business park called Airside Retail and Business Park, on the southern fringe of the town, hosting a number of employers. It is home to several corporates, including Ryanair, AIB, eShopWorld, Sandisk, Fujitsu, Ricoh and the European headquarters of Kellogg's. Ingersoll Rand also has its corporate headquarters in the Airside Business Park.

East of the town, running parallel to Swords bypass, lies the large Swords Business Park, where the Hertz Corporation have a Shared Services Centre.

Swords also has a large shopping centre, the Pavilions Swords, off the R132, which has a multi-screen cinema and branches of SuperValu and Dunnes Stores.

Aviation
Swords is the closest town to Dublin Airport and the two share the same Eircode routing area key of K67. The airport has long provided employment to the area. In 2011, Dublin Airport handled over 18.7 million passengers and served over 171 routes with 62 airlines. The airport serves as an operating base for Aer Lingus, Aer Lingus Regional, Air Contractors, CityJet, Ryanair and Thomson Airways, and as a maintenance base for Aer Lingus, CityJet, Dublin Aerospace, Eirtech Aviation, Etihad Airways and Ryanair.

The Irish Aviation Authority operate the Dublin Air Traffic Control Centre on the airport.

The headquarters of the Dublin Airport Authority and Ireland's four largest airlines are located in or near Swords. The Dublin Airport Authority, who manage Dublin, Cork and Shannon Airports, employ over 3,000 people and have their headquarters on the airport campus. Aer Lingus, Ireland's flag carrier, have their headquarters on the Dublin Airport campus. CityJet, part of the Air France-KLM group, has its headquarters in Swords Business Campus and Air Contractors, part of the ASL Aviation group, has its head office on the Malahide Road in Swords. In 2014, Ryanair moved into a new €20m, 100,000 sq ft Dublin Head Office in Airside Business Park. The building was officially opened in April 2014.

Logistics
In 2007 Tesco Ireland opened their new €70 million distribution centre in Lanestown, between Swords and Donabate. With a building footprint of over 68,000 m2 and a total volume of 1.55 million m2 the Tesco Ireland distribution centre is the largest building on the island of Ireland and one of the 10 largest building in the world. The building is over half a kilometre long, has 106 loading bays and supplies 106 stores up to 6 times a day.

Pharmaceutical
Swords is the home to several international chemical producers and pharmaceutical giants, including Opec. Merck Sharp & Dohme (formally Organnon) employ over 500 people in their facility in Drynam, which manufactures women's health, anaesthesiology and mental health products. Bristol Myers Squibb employ over 400 people in their Swords Laboratories bulk pharmaceutical plant on Watery Lane. The Lonza Group employ 45 people in their European manufacturing facility for personal care and industrial biocides, also on Watery Lane.

Food and horticulture
Swords is located in the centre of Fingal and is surrounded by farms growing crops like potatoes, wheat and barley. However, unlike the rest of Fingal, a lot of the food distributed from Swords has been imported from abroad. As of 2018, FoodCentral (marketed as "Ireland's national food park") was being developed south-west of Swords.

The Keeling's Group, who employ over 1700 people, have their headquarters in FoodCentral and use a lot of land around Swords. The Keeling's Farms division annually grow 2,500 tonnes of soft fruits/berries from 5 hectares of glasshouse, tunnel and field crops in Swords. They grow Bramley apples in 139 acres of orchards and lettuce in 8 acres of glasshouses. Their glasshouses also produce 1,500 tonnes of red, orange, yellow and green peppers annually. Keeling's also operate a large banana ripening facility for Chiquita which ripens over 3 million bananas each week. They also have separate ripening rooms for other fruits.

Total Produce, Ireland's largest agribusiness operates two facilities in Swords. Its facility in Swords Business Park includes a distribution and ripening centre for Fyffes Cape, Outspan, Green Ace and TOP Fruit products. Their "Uniplumo" facility on the Rathbeale Road, has 46,000 square metres of glasshouses for growing plants, flowers and tomatoes.

Primary
The town is served by more than 10 primary schools. These include several gaelscoils, a number of Educate Together schools,  and mixed and gender-specific national schools. The latter includes both Church of Ireland and Catholic schools. A number of other primary schools are in planning or under construction.

Secondary
The secondary schools serving the town include Loreto College (all-girls school, River Valley), Coláiste Choilm C.B.S. (all-boys school, Dublin Road), Fingal Community College (Seatown Road), St. Finian's Community College (Castlefarm), and Swords Community College (Rathbeale Road)

Third level and further education
Land has been reserved for a potential university campus at Lissenhall in north Swords.

The National Learning Network, Fingal Adult Education Service and Swords Youthreach each have a presence in the area.

There is also the Fingal Adult Literacy and Education Centre

Christianity
Christianity is the predominant religion in Swords and Roman Catholicism is the predominant denomination. The town has six Roman Catholic churches. St. Colmcille's, the Church of the Visitation and Our Lady Queen of Heaven are all within Swords parish. St. Cronan's and St. Finian's each belong to distinct parishes, while the Church of the Immaculate Conception lies within Donabate parish.

There are also a further eight Christian churches and a retreat centre. These include Swords Baptist Church which meets in The Riasc Centre in Feltrim. and St. Columba's Church of Ireland church on Church Road, Other Protestant and evangelical communities include the Apostolic Faith Church and Churchtown Trust. The Syriac Orthodox Church meets as the St. Ignatius Jacobite Congregation in St Columba's Church of Ireland church. Jehovah's Witnesses meet at a Kingdom Hall on Kettles Lane.

Islam
The Dublin Welfare Society manage a makeshift mosque in a Swords industrial estate

Local politicians
Swords is part of the Dáil constituency of Dublin Fingal. From the next general election, it will be part of the new constituency of Dublin Fingal East.

The local electoral area of Swords has 7 councillors on Fingal County Council.

Notable residents

 * Saint Colmcille, founder of Swords.
 * Gruffudd ap Cynan (1055–1137), Welsh King of Gwynedd, reared in Swords as a close relative of the Hiberno-Norse Kings of Dublin and grandson of King Brian Boru
 * Robert FitzRery, Attorney-General for Ireland from 1450 to 1463, came from a long-established Swords family which claimed descent from Gruffudd ap Cynan.
 * Eleanor Ambrose, Catholic heiress, is from Swords.
 * Conan Byrne, A retired League of Ireland Footballer.
 * Ed Byrne, comedian, is from Swords.
 * Jason Byrne, comedian, lives in Swords.
 * Bill Cullen, businessman, presenter of the TV show, "The Apprentice", owns and works at Europa Academy in Swords.
 * Duncan Campbell, video artist, won 2014 Turner Prize, grew up in Swords.
 * Paul Flynn, Dublin and Fingallians GAA player, lives in Swords.
 * Chris Newman, actor known for his roles in Song for a Raggy Boy and Red Rock
 * Ronan Keating, singer-songwriter, lived in the Highfields residential development on the town's southern side.
 * Richard Montgomery, hero of the American Revolution, born in Swords.
 * Blessed Francis Taylor, former Mayor of Dublin, martyr, born in Swords.
 * Kodaline, a popular band, come from Swords
 * Matt Doherty, Irish footballer for Wolverhampton Wanderers F.C.
 * Peter Kioso, footballer for Luton Town, born in Swords
 * Sean Roughan, footballer for Lincoln City, born in Swords
 * Zachary Elbouzedi, Irish footballer for AIK Fotboll
 * Jamie Finn, Irish footballer for Birmingham City W.F.C.
 * Keith Ward, footballer for Shelbourne FC

title: Swords, Dublin


text:
Sarki

Sarki may refer to:

 * Sarki, a well-dwelling snake slain by the mythological prince Bayajidda
 * Şarkı, a vocal genre in Ottoman classical music
 * Sarki (ethnic group), a sub group of Khas community
 * Sarki, Hausa title for a traditional ruler or chief

title: Sarki


text: User talk:69.3.76.228

title: User talk:69.3.76.228


text:
Tassel

A tassel is a finishing feature in fabric and clothing decoration. It is a universal ornament that is seen in varying versions in many cultures around the globe.

History and use
In the Hebrew Bible, the Lord spoke to Moses instructing him to tell the Israelites to make tassels (Hebrew tzitzit) on the corners of their garments, to help them to remember all the commandments of the Lord and to keep them (Numbers 15:37-40), and as a sign of holiness. The religious Hebrew tassel, however, bears little resemblance to the decorative one which appeared and eventually became popular in Europe, especially France and Spain.

In the West, tassels were originally a series of windings of thread or string around a suspending string until the desired curvature was attained. Later, turned wooden moulds, which were either covered in simple wrappings or much more elaborate coverings called satinings, were used. This involved an intricate binding of bands of filament silk vertically around the mould by means of an internal "lacing" in the bore of the mould. During the Middle Ages tassels were widely used in Spain as ornamentation for horses, called borla from the Latin term burrula which means "wool of little value".

These constructions were varied and augmented with extensive ornamentations that were each assigned an idiosyncratic term by their French creators. In sixteenth-century France these individuals were called passementiers, and an apprenticeship of seven years was required to become a master in one of the subdivisions of the guild. The French widely exported their very artistic work, and at such low prices that no other European nation developed a mature "trimmings" industry. Many of the passementiers, however, were among the Protestant Huguenots who fled France in the 1600s to escape persecution, taking their tools and skills with them. Tassels and their associated forms changed style throughout the years, from the small and casual of Renaissance designs (see example), through the medium sizes and more staid designs of the Empire period to the Victorian Era with the largest and most elaborate decorative flourishes. Some of these designs are returning today from the European and American artisans, who may charge a thousand dollars for a single hand-made tassel. The majority of the world's tassel production, however, takes place in China which mass-produces and exports them globally.

Tassels (also called tufts) were traditionally worn by Oxford and Cambridge University undergraduates on their caps, those wearing gold tassels were those who had paid for the status of gentleman-commoner, thus receiving increased social prestige and more luxurious accommodation than ordinary commoners who wore plain black tassels on their caps. Today, only the Chancellor of Oxford wears a gold tassel.

In the Middle East, tassels were worn as talismans, especially on headwear. In Egypt, Mesopotamia, and throughout the Arab world tassels were worn by children on hoods or caps to protect them from malevolent spirits and ward off demons.

Ceremonial wear
In the U.S., tassels, or liripipes, are also found on mortarboards during university graduation ceremonies and possibly upon the shoes of the graduates at the ceremony. Near the conclusion of the graduation ceremony, the tassel that hangs from the graduate's mortarboard is moved from the right to the left. Typically, the entire graduating class does this in unison.

Structure

A basic key tassel is made by binding or otherwise gathering threads from cord and creating a knot. Tassels are normally decorative elements, and as such one often finds them attached along the bottom hem of garments and curtains. The first Guild of Passementiers was created in France in the 1600s. The tassel was its primary expression, but it also included fringes, ornamental cords, galloons, pompons, rosettes, and gimps. Tassels, pompons and rosettes are point ornaments; the others are linear ornaments.

title: Tassel