Misplaced Pages

#795204

84-540: Rolex introduced the original Datejust (reference 4467) in 1945 to celebrate the company's 40th anniversary. It was available only in 18 karat yellow gold and had a small bubble back winder with a domed back. It also featured the company's waterproof Oyster case (first introduced in 1926), a fluted bezel, and the new Jubilee bracelet (so named for the occasion). Over the years, the Datejust saw an expansion of its design options as well as improvements to its movement, from

168-518: A 70-hour power reserve while maintaining the same dimensions as its predecessor. At Baselworld 2015, Rolex announced that the Lady-Datejust 26mm would be replaced by a newer 28mm variant, with a new Caliber 2236 movement, refined lugs and middle case, a broad and clear dial, as well as a President or Jubilee bracelet integrated into the Oyster case. As of 2019, the Datejust lineup consists of

252-580: A Datejust with a black dial in Lost in Translation . Matthew McConaughey's character in The Wolf of Wall Street wears a 90's Rolesor (two-toned stainless steel and gold) Datejust. Edie Falco consistently wears a 90s-era women's Datejust in her role as Carmela throughout the run of The Sopranos . Fineness The fineness of a precious metal object (coin, bar, jewelry, etc.) represents

336-587: A Rolex Datejust, as Rolex did not want to be associated with the character. In The Informers some of the cast wear Datejust watches. Paul Newman wears a full stainless steel 36mm Datejust in The Color of Money . Alin Busi owns this watch model. Harrison Ford sports a Datejust 36mm in the 1980s movie Frantic , which featured a white Roman numeral dial, white gold bezel and stainless steel jubilee bracelet and case. Bill Murray 's character wears

420-461: A compressive force on neighboring atoms, and smaller atoms exert a tensile force on their neighbors, helping the alloy resist deformation. Sometimes alloys may exhibit marked differences in behavior even when small amounts of one element are present. For example, impurities in semiconducting ferromagnetic alloys lead to different properties, as first predicted by White, Hogan, Suhl, Tian Abrie and Nakamura. Unlike pure metals, most alloys do not have

504-520: A concern because it would be possible for an unscrupulous refiner to produce precious metals bars that are slightly less pure than marked on the bar. A refiner doing $ 1 billion of business each year that marked .980 pure bars as .999 fine would make about an extra $ 20 million in profit. In the United States, the actual purity of gold articles must be no more than .003 less than the marked purity (e.g. .996 fine for gold marked .999 fine), and

588-614: A fineness of 11 ounces, 2 pennyweights, or exactly ( 11 + 2 20 ) 12 = 92.5 % {\displaystyle {\frac {(11+{\frac {2}{20}})}{12}}=92.5\%} silver. Alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Most alloys are metallic and show good electrical conductivity , ductility , opacity , and luster , and may have properties that differ from those of

672-466: A gaseous state, such as found in a blast furnace to make pig iron (liquid-gas), nitriding , carbonitriding or other forms of case hardening (solid-gas), or the cementation process used to make blister steel (solid-gas). It may also be done with one, more, or all of the constituents in the solid state, such as found in ancient methods of pattern welding (solid-solid), shear steel (solid-solid), or crucible steel production (solid-liquid), mixing

756-537: A gradual date change shortly before midnight in the earliest versions to an instantaneous change beginning in 1955. The Datejust is offered with two Rolex bracelets: the Jubilee and the Oyster. The original Datejust was launched with a case size of 36mm. Subsequently, various sizes including ladies' and mid-sized versions were made available. The Turn-O-Graph model was introduced in 1955 as an award given to US Air Force pilots returning from combat missions. It featured

840-592: A hard bronze-head, but a softer bronze-tang, combining the alloys to prevent both dulling and breaking during use. Mercury has been smelted from cinnabar for thousands of years. Mercury dissolves many metals, such as gold, silver, and tin, to form amalgams (an alloy in a soft paste or liquid form at ambient temperature). Amalgams have been used since 200 BC in China for gilding objects such as armor and mirrors with precious metals. The ancient Romans often used mercury-tin amalgams for gilding their armor. The amalgam

924-409: A less-than-24-karat gold alloy differs according to the alloys used. For example, knowing that standard 18-karat yellow gold consists of 75% gold, 12.5% silver and the remaining 12.5% of copper (all by mass), the volume of pure gold in this alloy will be 60% since gold is much denser than the other metals used: 19.32 g/cm for gold, 10.49 g/cm for silver and 8.96 g/cm for copper. Karat

SECTION 10

#1732780914796

1008-473: A minimum of 99.95% purity), 18-karat gold is 18 parts gold, 6 parts another metal (forming an alloy with 75% gold), 12-karat gold is 12 parts gold (12 parts another metal), and so forth. In England, the carat was divisible into four grains, and the grain was divisible into four quarts. For example, a gold alloy of 127 ⁄ 128 fineness (that is, 99.2% purity) could have been described as being 23-karat, 3-grain, 1-quart gold . The karat fractional system

1092-446: A molten metal is mixed with another substance, there are two mechanisms that can cause an alloy to form, called atom exchange and the interstitial mechanism . The relative size of each element in the mix plays a primary role in determining which mechanism will occur. When the atoms are relatively similar in size, the atom exchange method usually happens, where some of the atoms composing the metallic crystals are substituted with atoms of

1176-433: A molten metal may not always mix with another element. For example, pure iron is almost completely insoluble with copper. Even when the constituents are soluble, each will usually have a saturation point , beyond which no more of the constituent can be added. Iron, for example, can hold a maximum of 6.67% carbon. Although the elements of an alloy usually must be soluble in the liquid state, they may not always be soluble in

1260-455: A more concentrated form of iron carbide (Fe 3 C) in the spaces between the pure iron crystals. The steel then becomes heterogeneous, as it is formed of two phases, the iron-carbon phase called cementite (or carbide ), and pure iron ferrite . Such a heat treatment produces a steel that is rather soft. If the steel is cooled quickly, however, the carbon atoms will not have time to diffuse and precipitate out as carbide, but will be trapped within

1344-405: A pioneer in steel metallurgy, took an interest and produced a steel alloy containing around 12% manganese. Called mangalloy , it exhibited extreme hardness and toughness, becoming the first commercially viable alloy-steel. Afterward, he created silicon steel, launching the search for other possible alloys of steel. Robert Forester Mushet found that by adding tungsten to steel it could produce

1428-707: A rotating bezel marked to 60 minutes, which can be used to measure time intervals. Datejust watches of this type have been nicknamed "Thunderbirds". This watch would form the basis for the Rolex Explorer (designed for Sir Edmund Hillary 's Mount Everest expedition), the Rolex Submariner , and the Rolex Sea-Dweller . In 2009, the Rolex Oyster Perpetual Datejust II was released. At 41mm in diameter (excluding

1512-429: A single melting point , but a melting range during which the material is a mixture of solid and liquid phases (a slush). The temperature at which melting begins is called the solidus , and the temperature when melting is just complete is called the liquidus . For many alloys there is a particular alloy proportion (in some cases more than one), called either a eutectic mixture or a peritectic composition, which gives

1596-420: A very hard edge that would resist losing its hardness at high temperatures. "R. Mushet's special steel" (RMS) became the first high-speed steel . Mushet's steel was quickly replaced by tungsten carbide steel, developed by Taylor and White in 1900, in which they doubled the tungsten content and added small amounts of chromium and vanadium, producing a superior steel for use in lathes and machining tools. In 1903,

1680-480: A way to harden aluminium alloys for use in machine-gun cartridge cases. Knowing that aluminium-copper alloys were heat-treatable to some degree, Wilm tried quenching a ternary alloy of aluminium, copper, and the addition of magnesium, but was initially disappointed with the results. However, when Wilm retested it the next day he discovered that the alloy increased in hardness when left to age at room temperature, and far exceeded his expectations. Although an explanation for

1764-576: Is a metal. This is usually called the primary metal or the base metal, and the name of this metal may also be the name of the alloy. The other constituents may or may not be metals but, when mixed with the molten base, they will be soluble and dissolve into the mixture. The mechanical properties of alloys will often be quite different from those of its individual constituents. A metal that is normally very soft ( malleable ), such as aluminium , can be altered by alloying it with another soft metal, such as copper . Although both metals are very soft and ductile ,

SECTION 20

#1732780914796

1848-597: Is a variant of carat . First attested in English in the mid-15th century, the word carat came from Middle French carat , in turn derived either from Italian carato or Medieval Latin carratus . These were borrowed into Medieval Europe from the Arabic qīrāṭ meaning "fruit of the carob tree", also "weight of 5 grains", ( قيراط ) and was a unit of mass though it was probably not used to measure gold in classical times. The Arabic term ultimately originates from

1932-438: Is an extension of the older karat system of denoting the purity of gold by fractions of 24, such as "18 karat" for an alloy with 75% (18 parts per 24) pure gold by mass. The millesimal fineness is usually rounded to a three figure number, particularly where used as a hallmark , and the fineness may vary slightly from the traditional versions of purity. Here are the most common millesimal finenesses used for precious metals and

2016-457: Is believed to be the origin of the value of the karat. While there are many methods of detecting fake precious metals, there are realistically only two options available for verifying the marked fineness of metal as being reasonably accurate: assaying the metal (which requires destroying it), or using X-ray fluorescence (XRF). XRF will measure only the outermost portion of the piece of metal and so may get misled by thick plating. That becomes

2100-486: Is considered 100% gold. Millesimal fineness is a system of denoting the purity of platinum , gold and silver alloys by parts per thousand of pure metal by mass in the alloy. For example, an alloy containing 75% gold is denoted as "750". Many European countries use decimal hallmark stamps (i.e., "585", "750", etc.) rather than "14 k", "18 k", etc., which is used in the United Kingdom and United States. It

2184-772: Is extremely slow thus the penetration was not very deep, so the alloy was not homogeneous. In 1740, Benjamin Huntsman began melting blister steel in a crucible to even out the carbon content, creating the first process for the mass production of tool steel . Huntsman's process was used for manufacturing tool steel until the early 1900s. The introduction of the blast furnace to Europe in the Middle Ages meant that people could produce pig iron in much higher volumes than wrought iron. Because pig iron could be melted, people began to develop processes to reduce carbon in liquid pig iron to create steel. Puddling had been used in China since

2268-456: Is increasingly being complemented or superseded by the millesimal system, described above for bullion, though jewelry generally tends to still use the karat system. Conversion between percentage of pure gold and karats: However, this system of calculation gives only the mass of pure gold contained in an alloy. The term 18-karat gold means that the alloy's mass consists of 75% of gold and 25% of other metals. The quantity of gold by volume in

2352-400: Is performed by heating the base metal beyond its melting point and then dissolving the solutes into the molten liquid, which may be possible even if the melting point of the solute is far greater than that of the base. For example, in its liquid state, titanium is a very strong solvent capable of dissolving most metals and elements. In addition, it readily absorbs gases like oxygen and burns in

2436-471: Is prevented (forming martensite), most heat-treatable alloys are precipitation hardening alloys, that depend on the diffusion of alloying elements to achieve their strength. When heated to form a solution and then cooled quickly, these alloys become much softer than normal, during the diffusionless transformation, but then harden as they age. The solutes in these alloys will precipitate over time, forming intermetallic phases, which are difficult to discern from

2520-457: The Greek kerátion ( κεράτιον ) meaning carob seed (literally "small horn") (diminutive of κέρας – kéras , "horn" ). In 309 AD, Roman Emperor Constantine I began to mint a new gold coin solidus that was 1 ⁄ 72 of a libra (Roman pound) of gold equal to a mass of 24 siliquae , where each siliqua (or carat ) was 1 ⁄ 1728 of a libra. This

2604-576: The Wright brothers used a chromium-nickel steel to make the crankshaft for their airplane engine, while in 1908 Henry Ford began using vanadium steels for parts like crankshafts and valves in his Model T Ford , due to their higher strength and resistance to high temperatures. In 1912, the Krupp Ironworks in Germany developed a rust-resistant steel by adding 21% chromium and 7% nickel, producing

Rolex Datejust - Misplaced Pages Continue

2688-623: The bloomery process , it produced very soft but ductile wrought iron . By 800 BC, iron-making technology had spread to Europe, arriving in Japan around 700 AD. Pig iron , a very hard but brittle alloy of iron and carbon, was being produced in China as early as 1200 BC, but did not arrive in Europe until the Middle Ages. Pig iron has a lower melting point than iron, and was used for making cast-iron . However, these metals found little practical use until

2772-408: The solid state. If the metals remain soluble when solid, the alloy forms a solid solution , becoming a homogeneous structure consisting of identical crystals, called a phase . If as the mixture cools the constituents become insoluble, they may separate to form two or more different types of crystals, creating a heterogeneous microstructure of different phases, some with more of one constituent than

2856-713: The American Gold Eagle is embossed One Oz. Fine Gold and weighs 1.091 troy oz. Fineness of silver in Britain was traditionally expressed as the mass of silver expressed in troy ounces and pennyweights ( 1 ⁄ 20 troy ounce) in one troy pound (12 troy ounces) of the resulting alloy. Britannia silver has a fineness of 11 ounces, 10 pennyweights, or about ( 11 + 10 20 ) 12 = 95.833 % {\displaystyle {\frac {(11+{\frac {10}{20}})}{12}}=95.833\%} silver, whereas sterling silver has

2940-571: The Datejust 41 has smaller indexes and a thinner bezel compared to the Datejust II. In this year, Rolex also introduced the new Caliber 3235 movement, which replaces more than 90% of the parts of its predecessor, the Caliber 3135 - Rolex's longest running and most successful movement. Caliber 3235 includes a new escapement, the Chronergy, along with other significant improvements, and provides

3024-677: The Mediterranean, so it was often valued higher than gold. To make jewellery, cutlery, or other objects from tin, workers usually alloyed it with other metals to increase strength and hardness. These metals were typically lead , antimony , bismuth or copper. These solutes were sometimes added individually in varying amounts, or added together, making a wide variety of objects, ranging from practical items such as dishes, surgical tools, candlesticks or funnels, to decorative items like ear rings and hair clips. The earliest examples of pewter come from ancient Egypt, around 1450 BC. The use of pewter

3108-577: The Middle East, people began alloying copper with zinc to form brass. Ancient civilizations took into account the mixture and the various properties it produced, such as hardness , toughness and melting point, under various conditions of temperature and work hardening , developing much of the information contained in modern alloy phase diagrams . For example, arrowheads from the Chinese Qin dynasty (around 200 BC) were often constructed with

3192-438: The actual purity of silver articles must be no more than .004 less than the marked purity. A piece of alloy metal containing a precious metal may also have the weight of its precious component referred to as its "fine weight". For example, 1 troy ounce of 18 karat gold (which is 75% gold) may be said to have a fine weight of 0.75 troy ounces. Most modern government-issued bullion coins specify their fine weight. For example,

3276-516: The aerospace industry, to beryllium-copper alloys for non-sparking tools. An alloy is a mixture of chemical elements , which forms an impure substance (admixture) that retains the characteristics of a metal. An alloy is distinct from an impure metal in that, with an alloy, the added elements are well controlled to produce desirable properties, while impure metals such as wrought iron are less controlled, but are often considered useful. Alloys are made by mixing two or more elements, at least one of which

3360-414: The air, readily combines with most metals to form metal oxides ; especially at higher temperatures encountered during alloying. Great care is often taken during the alloying process to remove excess impurities, using fluxes , chemical additives, or other methods of extractive metallurgy . Alloying a metal is done by combining it with one or more other elements. The most common and oldest alloying process

3444-420: The alloy a unique and low melting point, and no liquid/solid slush transition. Alloying elements are added to a base metal, to induce hardness , toughness , ductility, or other desired properties. Most metals and alloys can be work hardened by creating defects in their crystal structure. These defects are created during plastic deformation by hammering, bending, extruding, et cetera, and are permanent unless

Rolex Datejust - Misplaced Pages Continue

3528-429: The alloy. However, most alloys were not created until the 1900s, such as various aluminium, titanium , nickel , and magnesium alloys . Some modern superalloys , such as incoloy , inconel, and hastelloy , may consist of a multitude of different elements. An alloy is technically an impure metal, but when referring to alloys, the term impurities usually denotes undesirable elements. Such impurities are introduced from

3612-444: The atomic arrangement that forms the alloy. They can be further classified as homogeneous (consisting of a single phase), or heterogeneous (consisting of two or more phases) or intermetallic . An alloy may be a solid solution of metal elements (a single phase, where all metallic grains (crystals) are of the same composition) or a mixture of metallic phases (two or more solutions, forming a microstructure of different crystals within

3696-635: The base metal. Unlike steel, in which the solid solution separates into different crystal phases (carbide and ferrite), precipitation hardening alloys form different phases within the same crystal. These intermetallic alloys appear homogeneous in crystal structure, but tend to behave heterogeneously, becoming hard and somewhat brittle. In 1906, precipitation hardening alloys were discovered by Alfred Wilm . Precipitation hardening alloys, such as certain alloys of aluminium, titanium, and copper, are heat-treatable alloys that soften when quenched (cooled quickly), and then harden over time. Wilm had been searching for

3780-554: The base metals and alloying elements, but are removed during processing. For instance, sulfur is a common impurity in steel. Sulfur combines readily with iron to form iron sulfide , which is very brittle, creating weak spots in the steel. Lithium , sodium and calcium are common impurities in aluminium alloys, which can have adverse effects on the structural integrity of castings. Conversely, otherwise pure-metals that contain unwanted impurities are often called "impure metals" and are not usually referred to as alloys. Oxygen, present in

3864-426: The carbon atoms are said to be in solution in the iron, forming a particular single, homogeneous, crystalline phase called austenite . If the steel is cooled slowly, the carbon can diffuse out of the iron and it will gradually revert to its low temperature allotrope. During slow cooling, the carbon atoms will no longer be as soluble with the iron, and will be forced to precipitate out of solution, nucleating into

3948-491: The crown) its case is bigger than the original Datejust. In 2016, the Rolex Oyster Perpetual Datejust 41 was released. The watch comes in stainless steel, and two-tone stainless steel and 18k yellow or 18k everose gold (Rolex's version of rose gold) bracelets. The 2016 41mm Datejust is on an Oyster or Jubilee bracelet. While the Datejust 41 has a similar-sized 41mm diameter case as the Datejust II,

4032-506: The crystals internally. Some alloys, such as electrum —an alloy of silver and gold —occur naturally. Meteorites are sometimes made of naturally occurring alloys of iron and nickel , but are not native to the Earth. One of the first alloys made by humans was bronze, which is a mixture of the metals tin and copper. Bronze was an extremely useful alloy to the ancients, because it is much stronger and harder than either of its components. Steel

4116-427: The elements via solid-state diffusion . By adding another element to a metal, differences in the size of the atoms create internal stresses in the lattice of the metallic crystals; stresses that often enhance its properties. For example, the combination of carbon with iron produces steel, which is stronger than iron, its primary element. The electrical and thermal conductivity of alloys is usually lower than that of

4200-466: The first airplane engine in 1903. During the time between 1865 and 1910, processes for extracting many other metals were discovered, such as chromium, vanadium, tungsten, iridium , cobalt , and molybdenum, and various alloys were developed. Prior to 1910, research mainly consisted of private individuals tinkering in their own laboratories. However, as the aircraft and automotive industries began growing, research into alloys became an industrial effort in

4284-416: The first century, and was introduced in Europe during the 1700s, where molten pig iron was stirred while exposed to the air, to remove the carbon by oxidation . In 1858, Henry Bessemer developed a process of steel-making by blowing hot air through liquid pig iron to reduce the carbon content. The Bessemer process led to the first large scale manufacture of steel. Steel is an alloy of iron and carbon, but

SECTION 50

#1732780914796

4368-499: The first stainless steel. Due to their high reactivity, most metals were not discovered until the 19th century. A method for extracting aluminium from bauxite was proposed by Humphry Davy in 1807, using an electric arc . Although his attempts were unsuccessful, by 1855 the first sales of pure aluminium reached the market. However, as extractive metallurgy was still in its infancy, most aluminium extraction-processes produced unintended alloys contaminated with other elements found in

4452-407: The following sizes: 28mm, 31mm, 34mm, 36mm, 41mm - which come in either full stainless steel, two-tone gold (yellow, Everose or white) and stainless steel, or solid gold (yellow, Everose and white) case and bracelet. In the book version of American Psycho , Patrick Bateman owns an unspecified Rolex. In the movie version , Bateman (played by Christian Bale ) wears a two-tone Seiko 5 that resembles

4536-400: The form of a high-manganese pig-iron called spiegeleisen ), which helped remove impurities such as phosphorus and oxygen; a process adopted by Bessemer and still used in modern steels (albeit in concentrations low enough to still be considered carbon steel). Afterward, many people began experimenting with various alloys of steel without much success. However, in 1882, Robert Hadfield , being

4620-474: The interstices, but some of the iron atoms are substituted by nickel and chromium atoms. The use of alloys by humans started with the use of meteoric iron , a naturally occurring alloy of nickel and iron. It is the main constituent of iron meteorites . As no metallurgic processes were used to separate iron from nickel, the alloy was used as it was. Meteoric iron could be forged from a red heat to make objects such as tools, weapons, and nails. In many cultures it

4704-556: The introduction of crucible steel around 300 BC. These steels were of poor quality, and the introduction of pattern welding , around the 1st century AD, sought to balance the extreme properties of the alloys by laminating them, to create a tougher metal. Around 700 AD, the Japanese began folding bloomery-steel and cast-iron in alternating layers to increase the strength of their swords, using clay fluxes to remove slag and impurities. This method of Japanese swordsmithing produced one of

4788-405: The iron crystals. When rapidly cooled, a diffusionless (martensite) transformation occurs, in which the carbon atoms become trapped in solution. This causes the iron crystals to deform as the crystal structure tries to change to its low temperature state, leaving those crystals very hard but much less ductile (more brittle). While the high strength of steel results when diffusion and precipitation

4872-450: The metal is recrystallized . Otherwise, some alloys can also have their properties altered by heat treatment . Nearly all metals can be softened by annealing , which recrystallizes the alloy and repairs the defects, but not as many can be hardened by controlled heating and cooling. Many alloys of aluminium, copper, magnesium , titanium, and nickel can be strengthened to some degree by some method of heat treatment, but few respond to this to

4956-485: The metal). Examples of alloys include red gold ( gold and copper ), white gold (gold and silver ), sterling silver (silver and copper), steel or silicon steel ( iron with non-metallic carbon or silicon respectively), solder , brass , pewter , duralumin , bronze , and amalgams . Alloys are used in a wide variety of applications, from the steel alloys, used in everything from buildings to automobiles to surgical tools, to exotic titanium alloys used in

5040-421: The most common terms associated with them. The karat (US spelling, symbol k or Kt ) or carat (UK spelling, symbol c or Ct ) is a fractional measure of purity for gold alloys , in parts fine per 24 parts whole. The karat system is a standard adopted by US federal law. where 24-karat gold is pure (while 100% purity is very difficult to attain, 24-karat as a designation is permitted in commerce for

5124-455: The ore; the most abundant of which was copper. These aluminium-copper alloys (at the time termed "aluminum bronze") preceded pure aluminium, offering greater strength and hardness over the soft, pure metal, and to a slight degree were found to be heat treatable. However, due to their softness and limited hardenability these alloys found little practical use, and were more of a novelty, until the Wright brothers used an aluminium alloy to construct

SECTION 60

#1732780914796

5208-418: The other constituent. This is called a substitutional alloy . Examples of substitutional alloys include bronze and brass, in which some of the copper atoms are substituted with either tin or zinc atoms respectively. In the case of the interstitial mechanism, one atom is usually much smaller than the other and can not successfully substitute for the other type of atom in the crystals of the base metal. Instead,

5292-416: The other. However, in other alloys, the insoluble elements may not separate until after crystallization occurs. If cooled very quickly, they first crystallize as a homogeneous phase, but they are supersaturated with the secondary constituents. As time passes, the atoms of these supersaturated alloys can separate from the crystal lattice, becoming more stable, and forming a second phase that serves to reinforce

5376-400: The phenomenon was not provided until 1919, duralumin was one of the first "age hardening" alloys used, becoming the primary building material for the first Zeppelins , and was soon followed by many others. Because they often exhibit a combination of high strength and low weight, these alloys became widely used in many forms of industry, including the construction of modern aircraft . When

5460-441: The presence of nitrogen. This increases the chance of contamination from any contacting surface, and so must be melted in vacuum induction-heating and special, water-cooled, copper crucibles . However, some metals and solutes, such as iron and carbon, have very high melting-points and were impossible for ancient people to melt. Thus, alloying (in particular, interstitial alloying) may also be performed with one or more constituents in

5544-636: The pure elements such as increased strength or hardness. In some cases, an alloy may reduce the overall cost of the material while preserving important properties. In other cases, the mixture imparts synergistic properties such as corrosion resistance or mechanical strength. In an alloy, the atoms are joined by metallic bonding rather than by covalent bonds typically found in chemical compounds. The alloy constituents are usually measured by mass percentage for practical applications, and in atomic fraction for basic science studies. Alloys are usually classified as substitutional or interstitial alloys , depending on

5628-415: The pure metals. The physical properties, such as density , reactivity , Young's modulus of an alloy may not differ greatly from those of its base element, but engineering properties such as tensile strength , ductility, and shear strength may be substantially different from those of the constituent materials. This is sometimes a result of the sizes of the atoms in the alloy, because larger atoms exert

5712-443: The purest steel-alloys of the ancient world. While the use of iron started to become more widespread around 1200 BC, mainly because of interruptions in the trade routes for tin, the metal was much softer than bronze. However, very small amounts of steel, (an alloy of iron and around 1% carbon), was always a byproduct of the bloomery process. The ability to modify the hardness of steel by heat treatment had been known since 1100 BC, and

5796-415: The rare material was valued for the manufacture of tools and weapons. Because the ancients could not produce temperatures high enough to melt iron fully, the production of steel in decent quantities did not occur until the introduction of blister steel during the Middle Ages. This method introduced carbon by heating wrought iron in charcoal for long periods of time, but the absorption of carbon in this manner

5880-612: The resulting aluminium alloy will have much greater strength . Adding a small amount of non-metallic carbon to iron trades its great ductility for the greater strength of an alloy called steel. Due to its very-high strength, but still substantial toughness , and its ability to be greatly altered by heat treatment , steel is one of the most useful and common alloys in modern use. By adding chromium to steel, its resistance to corrosion can be enhanced, creating stainless steel , while adding silicon will alter its electrical characteristics, producing silicon steel . Like oil and water,

5964-428: The same degree as does steel. The base metal iron of the iron-carbon alloy known as steel, undergoes a change in the arrangement ( allotropy ) of the atoms of its crystal matrix at a certain temperature (usually between 820 °C (1,500 °F) and 870 °C (1,600 °F), depending on carbon content). This allows the smaller carbon atoms to enter the interstices of the iron crystal. When this diffusion happens,

6048-400: The smaller atoms become trapped in the interstitial sites between the atoms of the crystal matrix. This is referred to as an interstitial alloy . Steel is an example of an interstitial alloy, because the very small carbon atoms fit into interstices of the iron matrix. Stainless steel is an example of a combination of interstitial and substitutional alloys, because the carbon atoms fit into

6132-459: The term alloy steel usually only refers to steels that contain other elements— like vanadium , molybdenum , or cobalt —in amounts sufficient to alter the properties of the base steel. Since ancient times, when steel was used primarily for tools and weapons, the methods of producing and working the metal were often closely guarded secrets. Even long after the Age of Enlightenment , the steel industry

6216-459: The weight of fine metal therein, in proportion to the total weight which includes alloying base metals and any impurities . Alloy metals are added to increase hardness and durability of coins and jewelry , alter colors, decrease the cost per weight, or avoid the cost of high-purity refinement. For example, copper is added to the precious metal silver to make a more durable alloy for use in coins, housewares and jewelry. Coin silver, which

6300-824: Was another common alloy. However, in ancient times, it could only be created as an accidental byproduct from the heating of iron ore in fires ( smelting ) during the manufacture of iron. Other ancient alloys include pewter , brass and pig iron . In the modern age, steel can be created in many forms. Carbon steel can be made by varying only the carbon content, producing soft alloys like mild steel or hard alloys like spring steel . Alloy steels can be made by adding other elements, such as chromium , molybdenum , vanadium or nickel , resulting in alloys such as high-speed steel or tool steel . Small amounts of manganese are usually alloyed with most modern steels because of its ability to remove unwanted impurities, like phosphorus , sulfur and oxygen , which can have detrimental effects on

6384-422: Was applied as a paste and then heated until the mercury vaporized, leaving the gold, silver, or tin behind. Mercury was often used in mining, to extract precious metals like gold and silver from their ores. Many ancient civilizations alloyed metals for purely aesthetic purposes. In ancient Egypt and Mycenae , gold was often alloyed with copper to produce red-gold, or iron to produce a bright burgundy-gold. Gold

6468-545: Was commissioned by the King of Syracuse to find a way to check the purity of the gold in a crown, leading to the famous bath-house shouting of "Eureka!" upon the discovery of Archimedes' principle . The term pewter covers a variety of alloys consisting primarily of tin. As a pure metal, tin is much too soft to use for most practical purposes. However, during the Bronze Age , tin was a rare metal in many parts of Europe and

6552-416: Was not generally considered an alloy until the decades between 1930 and 1970 (primarily due to the work of scientists like William Chandler Roberts-Austen , Adolf Martens , and Edgar Bain ), so "alloy steel" became the popular term for ternary and quaternary steel-alloys. After Benjamin Huntsman developed his crucible steel in 1740, he began experimenting with the addition of elements like manganese (in

6636-450: Was often found alloyed with silver or other metals to produce various types of colored gold . These metals were also used to strengthen each other, for more practical purposes. Copper was often added to silver to make sterling silver , increasing its strength for use in dishes, silverware, and other practical items. Quite often, precious metals were alloyed with less valuable substances as a means to deceive buyers. Around 250 BC, Archimedes

6720-597: Was shaped by cold hammering into knives and arrowheads. They were often used as anvils. Meteoric iron was very rare and valuable, and difficult for ancient people to work . Iron is usually found as iron ore on Earth, except for one deposit of native iron in Greenland , which was used by the Inuit . Native copper, however, was found worldwide, along with silver, gold, and platinum , which were also used to make tools, jewelry, and other objects since Neolithic times. Copper

6804-499: Was the hardest of these metals, and the most widely distributed. It became one of the most important metals to the ancients. Around 10,000 years ago in the highlands of Anatolia (Turkey), humans learned to smelt metals such as copper and tin from ore . Around 2500 BC, people began alloying the two metals to form bronze, which was much harder than its ingredients. Tin was rare, however, being found mostly in Great Britain. In

6888-474: Was used for making silver coins in the past, contains 90% silver and 10% copper, by mass . Sterling silver contains 92.5% silver and 7.5% of other metals, usually copper, by mass. Various ways of expressing fineness have been used and two remain in common use: millesimal fineness expressed in units of parts per 1,000 and karats or carats used only for gold . Karats measure the parts per 24, so that 18 karat = 18 ⁄ 24 = 75% and 24 karat gold

6972-562: Was very competitive and manufacturers went through great lengths to keep their processes confidential, resisting any attempts to scientifically analyze the material for fear it would reveal their methods. For example, the people of Sheffield , a center of steel production in England, were known to routinely bar visitors and tourists from entering town to deter industrial espionage . Thus, almost no metallurgical information existed about steel until 1860. Because of this lack of understanding, steel

7056-571: Was widespread across Europe, from France to Norway and Britain (where most of the ancient tin was mined) to the Near East. The alloy was also used in China and the Far East, arriving in Japan around 800 AD, where it was used for making objects like ceremonial vessels, tea canisters, or chalices used in shinto shrines. The first known smelting of iron began in Anatolia , around 1800 BC. Called

#795204