Bronze is a versatile and popular metal to work with for different projects, ranging from automobile and marine parts to musical instruments and tools. It can support applications within various industries thanks to some of its properties, including corrosion resistance and low friction levels.
Let’s take a look at bronze’s properties, characteristics and uses that can support your business.
Bronze is an alloy made of two elements — copper and tin. However, other metals can also make up bronze, such as aluminum, nickel, zinc, phosphorus and manganese. Depending on which elements make up bronze, the alloy’s hardness, ductility, flexibility and other properties can vary.
The difference between bronze and brass is important to note. Historically, bronze was made of copper and tin, and brass was made of copper and zinc. Today, the lines are more blurred between the two, with bronze often being referred to as a type of brass. Many times, copper alloy is an inclusive term that means both brass and bronze.
Overall, bronze is a cost-effective material to work with in various industries, sold in the form of rods, tubes, sheets and ingots, which is a block of pure metal in an oblong shape used for further processing.
Bronze is made of copper and tin, giving it a metallic brown color. Some common properties and characteristics of bronze include:
Bronze has non-sparking and non-magnetic properties compared to other common metals like steel. When you strike a piece of bronze, it won’t spark. This is extremely beneficial in applications that require working with hazardous or explosive materials on site.
While bronze is corrosion resistant, it can still oxidize. The oxidation of bronze produces a lime green patina, though you can treat the alloy to preserve its metallic brown properties. When bronze oxidizes, it forms a single layer of copper oxide, which eventually turns into copper carbonate.
Through this process, only an external layer of oxidation is present, protecting the interior metal from additional oxidation. However, if chloride is present like in seawater, something called the “bronze disease” can affect your material. This is when oxidation penetrates the entire metal, destroying it to the core.
As mentioned before, the compositions of bronze can vary, with many other elements making up its composition. While copper is the primary element and small amounts of tin are present, metals that can make up bronze include:
Bronze is a hard, brittle metal in which its properties and processing method relate to its specific elemental composition. Its appearance, conductivity, corrosion resistance and other properties can change depending on these other elements:
Adding aluminum to the copper-tin mixture creates a stronger type of alloy that’s even more corrosion resistant. Some other beneficial properties of aluminum include heat and electrical conductivity, low secondary heat emissions, toxicity range and high diffuse reflectivity.
Nickel silver is a type of bronze despite its name. It includes copper, tin and nickel, and the term “silver” describes the material’s shiny color. Its uses range from silverware, zippers and keys to musical instruments and heating coils.
Silicon bronze has an easy pouring ability and can be formed into different shapes. It’s extremely corrosion resistant, even when submerged in saltwater and most acids. Silicon, copper and tin create a great surface finish and a material that has self-lubricating properties. This is ideal for bushings and bearings, especially in the automotive industry.
Adding small amounts of phosphor to bronze can make it even stronger. Phosphor increases the material’s tensile strength and yield, along with its fatigue resistance, friction coefficient and durability. Phosphor bronze is excellent for applications where metal surfaces constantly slide over each other.
The addition of manganese to bronze is beneficial because it creates a material that can withstand high-load applications that operate at low speed, which is actually one of bronze’s weaknesses. On the other hand, manganese turns the alloy into a metal that you can’t treat with heat, making it necessary to use special lubrication.
With a new element like aluminum, nickel, silicon, phosphor or manganese added to bronze, unique properties arise that are perfect for specific projects. Each type also upholds a few general bronze properties, such as hardness, a high melting point and corrosion resistance.
Metal fabrication is most often associated with steel and aluminum, but there are several projects where bronze is the perfect material. Bronze is good for manufacturing small parts, bronze casting, architecture, instruments, bronze wool, sculptures, tools and many other applications. Projects using this alloy can range from automobile parts to machine designs and much more.
Because bronze is corrosion resistant, has high strength and has a unique color, it can be used for manufacturing a variety of small parts:
Bronze is especially corrosion resistant to salt and fresh water, making it a helpful choice for applications like engine parts, propellers, pumps and bells.
Bronze casting is a process where liquid alloy is poured into a mold and solidifies. The casting is the hardened bronze component. Bronze is easy to machine and pour when you’re working with castings to create components like pumps, valve stems, bearings and bushings for different engines. Because bronze has low-friction characteristics and is thermal resistant, it’s a dependable material in applications where the parts slide against each other.
Architects can use bronze to build different structures where they want to preserve the natural or original look of the alloy. For example, bronze is a prevalent material in making various bridge components. To prevent bronze from oxidizing, you can maintain the material’s raw finish by oiling, polishing or using a special lacquer.
Because of bronze’s durability and timbre properties, manufacturers prefer to use it when making bells, cymbals and other musical instruments like saxophones. Bronze can also be used for the windings of nylon and the steel strings used in guitars and pianos to produce a warmer sound compared to other metals.
Used as an alternative to steel wool, bronze wool doesn’t shed or leave stains on wood. You can polish and sand metal surfaces and wood, and it’s ideal for construction, industrial and marine applications.
Artists use bronze to form sculptures. It’s a preferred metal for sculpting because it expands before setting, which allows the more intricate details to come to life in a sculpture. As it’s cooling, bronze also constricts, making the mold easy to remove.
Tools like axes, hammers, wrenches and mallets can create sparks when struck on flammable materials, causing safety hazards within your work zone. However, because bronze is a non-sparking and non-magnetic alloy, it’s an increasingly common material used to manufacture various tools to ensure a safe environment when working with other flammable or explosive objects.
Bronze casting is one of the most popular uses of this alloy, but it can also be used for any type of fabrication process. Consider your application and the properties you desire most, like corrosion resistance, thermal conductivity and ductility.
Warner Brothers Foundry Company is a full-service bronze casting foundry that also works with materials like aluminum and brass. We deliver top-quality, non-ferrous castings that exceed expectations and are your one-stop shop for casting, testing and prototypes.
Through superior craftsmanship, quality and on-time delivery, Warner Brothers has a reputation for doing things right. We use customized, top-of-the-line materials and provide testing to ensure we exceed your standards. By using a unique air-set sand technique that results in better stability and mechanical properties, we help you save money from wasted time and returns on a bad casting.
Check out our bronze spec sheets to learn more about different bronze alloys or contact a Warner Brothers representative for any of your bronze casting needs.
This article is about the metal alloy. For other uses, see Bronze (disambiguation)
Various examples of bronze artworks throughout history
Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such as arsenic or silicon. These additions produce a range of alloys that may be harder than copper alone, or have other useful properties, such as strength, ductility, or machinability.
The archaeological period in which bronze was the hardest metal in widespread use is known as the Bronze Age. The beginning of the Bronze Age in western Eurasia and India is conventionally dated to the mid-4th millennium BC (~3500 BC), and to the early 2nd millennium BC in China;[1] elsewhere it gradually spread across regions. The Bronze Age was followed by the Iron Age starting about 1300 BC and reaching most of Eurasia by about 500 BC, although bronze continued to be much more widely used than it is in modern times.
Because historical artworks were often made of brasses (copper and zinc) and bronzes of different metallic compositions, modern museum and scholarly descriptions of older artworks increasingly use the generalized term "copper alloy" instead of the names of individual alloys. This is done (at least in part) to prevent database searches from failing merely because of errors or disagreements in the naming of historic copper alloys.[2]
Etymology
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The word bronze (1730–1740) is borrowed from Middle French bronze (1511), itself borrowed from Italian bronzo 'bell metal, brass' (13th century, transcribed in Medieval Latin as bronzium) from either:
bróntion
, back-formation from Byzantine Greekbrontēsíon
(βροντησίον
, 11th century), perhaps fromBrentḗsion
(Βρεντήσιον
,'
Brindisi'
, reputed for its bronze;[3][4] or originally:birinj
, (برنج
,'
brass
'
, modernberenj
) andpiring
(پرنگ
)'
copper
'
,[5] from which also came Georgianbrinǯi
(ბრინჯი
), Turkishpirinç
, and Armenianbrinj
(բրինձ
), also meaning'
bronze
'
.History
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Hoard of bronze socketed axes from the Bronze Age found in modern Germany. This was the top tool of the period, and also seems to have been used as a store of value. Roman bronze nails with magical signs and inscriptions, 3rd-4th century AD.The discovery of bronze enabled people to create metal objects that were harder and more durable than previously possible. Bronze tools, weapons, armor, and building materials such as decorative tiles were harder and more durable than their stone and copper ("Chalcolithic") predecessors. Initially, bronze was made out of copper and arsenic or from naturally or artificially mixed ores of those metals, forming arsenic bronze.[6]
The earliest bronze artifacts so far known come from the Iranian plateau in the 5th millennium BC, and are smelted from native arsenical copper and copper-arsenides, such as algodonite and domeykite.[7] The earliest tin-copper-alloy artifact has been dated to c. 4650 BC, in a Vinča culture site in Pločnik (Serbia), and believed to have been smelted from a natural tin-copper ore, stannite.[8] Other early examples date to the late 4th millennium BC in Egypt, Susa (Iran) and some ancient sites in China, Luristan (Iran),[7] Tepe Sialk (Iran),[7] Mundigak (Afghanistan),[7] and Mesopotamia (Iraq).[citation needed]
Tin bronze was superior to arsenic bronze in that the alloying process could be more easily controlled, and the resulting alloy was stronger and easier to cast. Also, unlike those of arsenic, metallic tin and the fumes from tin refining are not toxic.
Tin became the major non-copper ingredient of bronze in the late 3rd millennium BC.[9] Ores of copper and the far rarer tin are not often found together (exceptions include Cornwall in the United Kingdom, one ancient site in Thailand and one in Iran), so serious bronze work has always involved trade with other regions. Tin sources and trade in ancient times had a major influence on the development of cultures. In Europe, a major source of tin was the British deposits of ore in Cornwall, which were traded as far as Phoenicia in the eastern Mediterranean. In many parts of the world, large hoards of bronze artifacts are found, suggesting that bronze also represented a store of value and an indicator of social status. In Europe, large hoards of bronze tools, typically socketed axes (illustrated above), are found, which mostly show no signs of wear. With Chinese ritual bronzes, which are documented in the inscriptions they carry and from other sources, the case is clear. These were made in enormous quantities for elite burials, and also used by the living for ritual offerings.
Transition to iron
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Though bronze is generally harder than wrought iron, with Vickers hardness of 60–258 vs. 30–80,[10] the Bronze Age gave way to the Iron Age after a serious disruption of the tin trade: the population migrations of around 1200–1100 BC reduced the shipping of tin around the Mediterranean and from Britain, limiting supplies and raising prices.[11] As the art of working in iron improved, iron became cheaper and improved in quality. As cultures advanced from hand-wrought iron to machine-forged iron (typically made with trip hammers powered by water), blacksmiths also learned how to make steel. Steel is stronger and harder than bronze and holds a sharper edge longer.[12] Bronze was still used during the Iron Age, and has continued in use for many purposes to the modern day.
Composition
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Bronze bell with a visible crystallite structure.There are many different bronze alloys, but typically modern bronze is 88% copper and 12% tin.[13] Alpha bronze consists of the alpha solid solution of tin in copper. Alpha bronze alloys of 4–5% tin are used to make coins, springs, turbines and blades. Historical "bronzes" are highly variable in composition, as most metalworkers probably used whatever scrap was on hand; the metal of the 12th-century English Gloucester Candlestick is bronze containing a mixture of copper, zinc, tin, lead, nickel, iron, antimony, arsenic and an unusually large amount of silver – between 22.5% in the base and 5.76% in the pan below the candle. The proportions of this mixture suggest that the candlestick was made from a hoard of old coins. The 13th-century Benin Bronzes are in fact brass, and the 12th-century Romanesque Baptismal font at St Bartholomew's Church, Liège is sometimes described as bronze and sometimes as brass.
In the Bronze Age, two forms of bronze were commonly used: "classic bronze", about 10% tin, was used in casting; and "mild bronze", about 6% tin, was hammered from ingots to make sheets. Bladed weapons were mostly cast from classic bronze, while helmets and armor were hammered from mild bronze.
Modern commercial bronze (90% copper and 10% zinc) and architectural bronze (57% copper, 3% lead, 40% zinc) are more properly regarded as brass alloys because they contain zinc as the main alloying ingredient. They are commonly used in architectural applications.[14][15] Plastic bronze contains a significant quantity of lead, which makes for improved plasticity,[16] and was possibly used by the ancient Greeks in ship construction.[17] Silicon bronze has a composition of Si: 2.80–3.80%, Mn: 0.50–1.30%, Fe: 0.80% max., Zn: 1.50% max., Pb: 0.05% max., Cu: balance.[18] Other bronze alloys include aluminium bronze, phosphor bronze, manganese bronze, bell metal, arsenical bronze, speculum metal, bismuth bronze, and cymbal alloys.
Properties
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Copper-based alloys have lower melting points than steel or iron and are more readily produced from their constituent metals. They are generally about 10 percent denser than steel, although alloys using aluminum or silicon may be slightly less dense. Bronze is a better conductor of heat and electricity than most steels. The cost of copper-base alloys is generally higher than that of steels but lower than that of nickel-base alloys.
Bronzes are typically ductile alloys, considerably less brittle than cast iron. Copper and its alloys have a huge variety of uses that reflect their versatile physical, mechanical, and chemical properties. Some common examples are the high electrical conductivity of pure copper, low-friction properties of bearing bronze (bronze that has a high lead content— 6–8%), resonant qualities of bell bronze (20% tin, 80% copper), and resistance to corrosion by seawater of several bronze alloys.
The melting point of bronze varies depending on the ratio of the alloy components and is about 950 °C (1,742 °F). Bronze is usually nonmagnetic, but certain alloys containing iron or nickel may have magnetic properties. Typically bronze oxidizes only superficially; once a copper oxide (eventually becoming copper carbonate) layer is formed, the underlying metal is protected from further corrosion. This can be seen on statues from the Hellenistic period. If copper chlorides are formed, a corrosion-mode called "bronze disease" will eventually completely destroy it.[19]
Uses
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Bronze weight with an inscribed imperial order, Qin dynasty Industrial products of the Bunting Brass and Bronze Company, 1912Bronze, or bronze-like alloys and mixtures, were used for coins over a longer period. Bronze was especially suitable for use in boat and ship fittings prior to the wide employment of stainless steel owing to its combination of toughness and resistance to salt water corrosion. Bronze is still commonly used in ship propellers and submerged bearings. In the 20th century, silicon was introduced as the primary alloying element, creating an alloy with wide application in industry and the major form used in contemporary statuary. Sculptors may prefer silicon bronze because of the ready availability of silicon bronze brazing rod, which allows color-matched repair of defects in castings. Aluminum is also used for the structural metal aluminum bronze. Bronze parts are tough and typically used for bearings, clips, electrical connectors and springs.
Bronze also has low friction against dissimilar metals, making it important for cannons prior to modern tolerancing, where iron cannonballs would otherwise stick in the barrel.[20] It is still widely used today for springs, bearings, bushings, automobile transmission pilot bearings, and similar fittings, and is particularly common in the bearings of small electric motors. Phosphor bronze is particularly suited to precision-grade bearings and springs. It is also used in guitar and piano strings. Unlike steel, bronze struck against a hard surface will not generate sparks, so it (along with beryllium copper) is used to make hammers, mallets, wrenches and other durable tools to be used in explosive atmospheres or in the presence of flammable vapors. Bronze is used to make bronze wool for woodworking applications where steel wool would discolor oak. Phosphor bronze is used for ships' propellers, musical instruments, and electrical contacts.[21] Bearings are often made of bronze for its friction properties. It can be impregnated with oil to make the proprietary Oilite and similar material for bearings. Aluminum bronze is hard and wear-resistant, and is used for bearings and machine tool ways.[22]
Architectural bronze
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The Seagram Building viewed from across Park Avenue at 52nd StreetThe Seagram Building on New York City's Park Avenue is the "iconic glass box sheathed in bronze, designed by Mies van der Rohe."[23] The Seagram Building was the first time that an entire building was sheathed in bronze.[24] The General Bronze Corporation fabricated 3,200,000 pounds (1,600 tons) of bronze at its plant in Garden City, New York.[24] The Seagram Building is a 38-story, 516-foot bronze-and-topaz-tinted glass building.[23] The building looks like a "squarish 38-story tower clad in a restrained curtain wall of metal and glass."[25] "Bronze was selected because of its color, both before and after aging, its corrosion resistance, and its extrusion properties.[24][23] It was not only the most expensive building of its time — $36 million — but it was the first building in the world with floor-to-ceiling glass walls.[23] Mies van der Rohe achieved the crisp edges that were custom-made with specific detailing by General Bronze[24] and "even the screws that hold in the fixed glass-plate windows were made of brass."[23]
Sculptures
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Bronze is widely used for casting bronze sculptures. Common bronze alloys have the unusual and desirable property of expanding slightly just before they set, thus filling the finest details of a mould. Then, as the bronze cools, it shrinks a little, making it easier to separate from the mould.[26] The Assyrian king Sennacherib (704–681 BC) claims to have been the first to cast monumental bronze statues (of up to 30 tonnes) using two-part moulds instead of the lost-wax method.[27]
Bronze statues were regarded as the highest form of sculpture in Ancient Greek art, though survivals are few, as bronze was a valuable material in short supply in the Late Antique and medieval periods. Many of the most famous Greek bronze sculptures are known through Roman copies in marble, which were more likely to survive. In India, bronze sculptures from the Kushana (Chausa hoard) and Gupta periods (Brahma from Mirpur-Khas, Akota Hoard, Sultanganj Buddha) and later periods (Hansi Hoard) have been found.[28] Indian Hindu artisans from the period of the Chola empire in Tamil Nadu used bronze to create intricate statues via the lost-wax casting method with ornate detailing depicting the deities of Hinduism. The art form survives to this day, with many silpis, craftsmen, working in the areas of Swamimalai and Chennai.
In antiquity other cultures also produced works of high art using bronze. For example: in Africa, the bronze heads of the Kingdom of Benin; in Europe, Grecian bronzes typically of figures from Greek mythology; in east Asia, Chinese ritual bronzes of the Shang and Zhou dynasty—more often ceremonial vessels but including some figurine examples. Bronze continues into modern times as one of the materials of choice for monumental statuary.
Lamps
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Tiffany Glass Studios, made famous by Louis C. Tiffany commonly referred to his product as favrile glass or "Tiffany glass," and used bronze in their artisan work for his Tiffany lamps.[29][30][31][32]
Tiffany table lamp with bronzeFountains and doors
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The largest and most ornate bronze fountain known to be cast in the world was by the Roman Bronze Works and General Bronze Corporation in 1952. The material used for the fountain, known as statuary bronze, is a quaternary alloy made of copper, zinc, tin, and lead, and traditionally golden brown in color. This was made for the Andrew W. Mellon Memorial in Federal Triangle in Washington, DC.[33] Another example of the massive, ornate design projects of bronze, and attributed to General Bronze/Roman Bronze Works were the massive bronze doors to the United States Supreme Court Building in Washington, DC.[34]
Mirrors
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Decorated back of a Celtic bronze mirror, 120-80 BC, St Keverne, EnglandBefore it became possible to produce glass with acceptably flat surfaces, bronze was a standard material for mirrors. Bronze was used for this purpose in many parts of the world, probably based on independent discoveries. Bronze mirrors survive from the Egyptian Middle Kingdom (2040–1750 BC), and China from at least c. 550 BC. In Europe, the Etruscans were making bronze mirrors in the sixth century BC, and Greek and Roman mirrors followed the same pattern. Although other materials such as speculum metal had come into use, and Western glass mirrors had largely taken over, bronze mirrors were still being made in Japan and elsewhere in the eighteenth century, and are still made on a small scale in Kerala, India.
Musical instruments
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Singing bowls from the 16th to 18th centuries. Annealed bronze continues to be made in the HimalayasBronze is the preferred metal for bells in the form of a high tin bronze alloy known as bell metal, which is typically about 23% tin.
Nearly all professional cymbals are made from bronze, which gives a desirable balance of durability and timbre. Several types of bronze are used, commonly B20 bronze, which is roughly 20% tin, 80% copper, with traces of silver, or the tougher B8 bronze made from 8% tin and 92% copper. As the tin content in a bell or cymbal rises, the timbre drops.[35]
Bronze is also used for the windings of steel and nylon strings of various stringed instruments such as the double bass, piano, harpsichord, and guitar. Bronze strings are commonly reserved on pianoforte for the lower pitch tones, as they possess a superior sustain quality to that of high-tensile steel.[36]
Bronzes of various metallurgical properties are widely used in struck idiophones around the world, notably bells, singing bowls, gongs, cymbals, and other idiophones from Asia. Examples include Tibetan singing bowls, temple bells of many sizes and shapes, Javanese gamelan, and other bronze musical instruments. The earliest bronze archeological finds in Indonesia date from 1–2 BC, including flat plates probably suspended and struck by a wooden or bone mallet.[36][37] Ancient bronze drums from Thailand and Vietnam date back 2,000 years. Bronze bells from Thailand and Cambodia date back to 3600 BC.
Some companies are now making saxophones from phosphor bronze (3.5 to 10% tin and up to 1% phosphorus content).[38] Bell bronze/B20 is used to make the tone rings of many professional model banjos.[39] The tone ring is a heavy (usually 3 lb; 1.4 kg) folded or arched metal ring attached to a thick wood rim, over which a skin, or most often, a plastic membrane (or head) is stretched – it is the bell bronze that gives the banjo a crisp powerful lower register and clear bell-like treble register.[citation needed]
Coins and medals
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Bronze has also been used in coins; most "copper" coins are actually bronze, with about 4 percent tin and 1 percent zinc.[40]
As with coins, bronze has been used in the manufacture of various types of medals for centuries, and "bronze medals" are known in contemporary times for being awarded for third place in sporting competitions and other events. The term is now often used for third place even when no actual bronze medal is awarded. The usage in part arose from the trio of gold, silver and bronze to represent the first three Ages of Man in Greek mythology: the Golden Age, when men lived among the gods; the Silver age, where youth lasted a hundred years; and the Bronze Age, the era of heroes. It was first adopted for a sports event at the 1904 Summer Olympics. At the 1896 event, silver was awarded to winners and bronze to runners-up, while at 1900 other prizes were given rather than medals.
Bronze is the normal material for the related form of the plaquette, normally a rectangular work of art with a scene in relief, for a collectors' market.
Biblical references
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There are over 125 references to bronze ('nehoshet'), which appears to be the Hebrew word used for copper and any of its alloys. However, the Old Testament era Hebrews are not thought to have had the capability to manufacture zinc (needed to make brass) and so it is likely that 'nehoshet' refers to copper and its alloys with tin, now called bronze.[41] In the King James Version, there is no use of the word 'bronze' and 'nehoshet' was translated as 'brass'. Modern translations use 'bronze'. Bronze (nehoshet) was used widely in the Tabernacle for items such as the bronze altar (Exodus Ch.27), bronze laver (Exodus Ch.30), utensils, and mirror (Exodus Ch.38). It was mentioned in the account of Moses holding up a bronze snake on a pole in Numbers Ch.21. In First Kings, it is mentioned that Hiram was very skilled in working with bronze, and he made many furnishings for Solomon's Temple including pillars, capitals, stands, wheels, bowls, and plates, some of which were highly decorative (see I Kings 7:13-47). Bronze was also widely used as battle armor and helmet, as in the battle of David and Goliath in I Samuel 17:5-6;38 (also see II Chron. 12:10).
See also
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References
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