Types of Metal
Aluminium is a widely used light weight metal. Raw aluminium is not very strong and it is therefore often alloyed with silicon. Normally about 1% silicon is used, but for casting alloys the silicon content can be up to 12%.
Raw aluminium has poor corrosive resistance, but thanks to a protective self generating oxide layer, the material can be used in corrosive environments.
The quality of the oxide layer can be controled through an anodizing process, and in this way achieve decorative effects and improve corrosion protection.
Very light aluminium structures can be formed using foamed aluminium. By mixing the aluminium with titanium hydride before casting, hydrogen gas foams the aluminium.
The surface is porous, but can be covered with an extra layer of solid aluminium. Unlike honeycombe aluminium structures, the material can be used within the same temperature range as solid aluminium, i.e. also at higher temperatures.
Bismuth is a chemical element that has the symbol Bi and atomic number 83. This heavy, brittle, white crystalline trivalent poor metal has a pink tinge and chemically resembles arsenic and antimony. Of all the metals, it is the most naturally dia-magnetic, only mercury has a lower thermal conductivity.
Bismuth compounds are used in cosmetics and in medical procedures. As the toxicity of lead has become more apparent in recent years, alloy uses for bismuth metal as a replacement for lead have become an increasing part of bismuth's commercial importance.
Brass is a yellow alloy used in musical instruments, rifle cartridges and cutlery (under silver plating).Brass is an alloy of copper and zinc. Brass with a lower zinc content (30%) has an excellent formability and is often referred to as cartridge brass. Higher zinc contents gives good casting and machining properties.
Bronze is a reddish alloy used in church bells, casted sculptures, canons and in bearings. It has a reasonable hardness, good weather resistance and is easy to cast.
The major alloying element in bronze is always copper. Normally the other major alloying element is tin but it can also be other metals like nickel.
Cadmium is a chemical element in the periodic table that has the symbol Cd and atomic number 48. A relatively rare, soft, bluish-white, transition metal, cadmium is known to cause cancer and occurs with zinc ores. Cadmium is used largely in batteries and pigments, e.g.,in plastic products.
Chromium is used in chromium plating for decoration and corrosion as well as wear protection. It is also used as an alloying element in stainless steel.
The most common form of chromium is very hard and brittle up to 700 C, and only over this temperature becomes ductile. Pure chromium is ductile, but is only produced in laboratory scale.
Chromium is resistant to corrosion and oxidation up to 1100 C, due to an resistant film that develops on the surface of the metal. These properties are transferred to alloys which contains chromium in sufficient amounts.
Cobalt is a hard, lustrous, silver-grey metal, a chemical element with symbol Co. It is found in various ores, and is used in the preparation of magnetic, wear-resistant, and high-strength alloys. Its compounds are used in the production of inks, paints, and varnishes.
A red, moderately expensive and fairly soft material. Excelent electric conductivity and therefore used in electric wires. Easy to shape and used for water pipes, roof plates and in older cooking equipment.Copper is the dominant alloying element in brass (together with zinc) and bronze (normally together with tin).
Gold is a chemical element with the symbol Au (from the Latin aurum) and atomic number 79. It is a highly sought-after precious metal which, for many centuries, has been used as money, a store of value and in jewellery. The metal occurs as nuggets or grains in rocks, underground "veins" and in alluvial deposits. It is one of the coinage metals. Gold is dense, soft, shiny and the most malleable and ductile of the known metals. Pure gold has an attractive bright yellow color.
Gold forms the basis for a monetary standard used by the International Monetary Fund (IMF) and the Bank for International Settlements (BIS). The ISO currency code of gold bullion is XAU. Modern industrial uses include dentistry and electronics, where gold has traditionally found use because of its good resistance to oxidative corrosion.
Chemically, gold is a trivalent and univalent transition metal. Gold does not react with most chemicals, but is attacked by chlorine, fluorine, aqua regia and cyanide. Gold dissolves in mercury, forming amalgam alloys, but does not react with it. Gold is insoluble in nitric acid, which will dissolve silver and base metals, and this is the basis of the gold refining technique known as "inquartation and parting". Nitric acid has long been used to confirm the presence of gold in items, and this is the origin of the colloquial term "acid test," referring to a gold standard test for genuine value.
Cast iron refers to a family of ferrous alloys composed of iron, carbon (2-4.5 %), and silicon (up to about 3.5 %). There are different common types of cast iron.
Gray cast iron is negligible ductile, brittle, and dampens vibrations. In gray cast iron the carbon has the form of graphite flakes.White cast iron is hard, wear resistant, and brittle. Here the carbon is bound in small very hard ceramic particles called cementite.
Ductile iron is ductile and shock resistant and is made by a heat treatment of gray cast iron where the graphite flakes change shape into small spheres. Malleable iron is strong, ductile and shock resistant.
A heavy and soft metal. Used in ship keels and fishing nets sinkers to give weight.Also used to insulate against radioactivity.Earlier used around roof windows, since its softness makes it easy to shape it around the roof tiles. Previously also widely used for shot in shotguns. Now abandoned due to the poisonous effect from lead..
Magnesium is a very light weight metal, increasingly substituting aluminium in order to save weight. It is a reactive metal, e.g., can burn, but with proper surface treatment it is used in products like car wheels and power saws.
Mercury also called quicksilver, is a chemical element in the periodic table that has the symbol Hg (Latinized Greek: hydrargyrum, meaning watery or liquid silver) and atomic number 80. A heavy, silvery transition metal, mercury is one of five elements that are liquid at or near room temperature and pressure. The others are the metals caesium, francium, and gallium, and the non-metal bromine.
Mercury is used in thermometers, barometers and other scientific apparatus, though concerns about the element's toxicity have led to mercury thermometers being largely phased out in clinical environments in favour of alcohol-filled, digital, or thermistor-based instruments. It remains in use in a number of other ways in scientific and scientific research applications, and in dental amalgam. Mercury is mostly obtained by reduction from the mineral cinnabar.
Mercury occurs in deposits throughout the world and it is harmless in an insoluble form, such as mercuric sulfide, but it is poisonous in soluble forms such as mercuric chloride or methylmercury.
Molybdenum is a chemical element with the symbol Mo and atomic number 42. It has the sixth highest melting point of any element, and for this reason it is often used in high-strength steel alloys. Molybdenum is found in trace amounts in plants and animals, although excess molybdenum can be toxic in some animals. Molybdenum was discovered in 1778 by Carl Wilhelm Scheele and first isolated in 1781 by Peter Jacob Hjelm.
Molybdenum is a transition metal with an electronegativity of 1.8 on the Pauling scale and an atomic mass of 95.9 g/mole.It does not react with oxygen or water at room temperature. At elevated temperatures, molybdenum trioxide is formed in the reaction 2Mo + 3O2 ? 2MoO3.
In its pure metal form, molybdenum is silvery white and very hard, though it is somewhat more ductile than tungsten. It has a melting point of 2623°C, and only tantalum, osmium, rhenium and tungsten have higher melting points.Molybdenum burns only at temperatures above 600°C.It also has the lowest heating expansion of any commercially used metal.
Molybdenum has a value of approximately $65,000 per tonne as of 4 May 2007. It maintained a price at or near $10,000 per tonne from 1997 through 2002, and reached a high of $103,000 per tonne in June 2005.
Nickel is a silver-white metal. The picture illustrates the colour difference between a chromium-plated tube and a nickel-plated runner. Nickel coating can be applied to many other materials achiving decoration and improved corrosion and wear resistance.
Nickel alloys have high strength and corrosion resistance at elevated temperatures. Alloying elements in nickel are chromium, cobalt and molybdenum.
Nickel is a major alloying element that imparts strength, toughness, and corrosion resistance. It is used extensively in stainless steels and nickel-base alloys (superalloys), used for high temperature applications (e.g. engine components, rockets).
Platinum is a chemical element in the periodic table that has the atomic symbol Pt and an atomic number of 78. A heavy, malleable, ductile, precious, grey-white transition metal, platinum is resistant to corrosion and occurs in some nickel and copper ores along with some native deposits. Platinum is used in jewellery, laboratory equipment, electrical contacts, dentistry, and automobile emissions control devices. Platinum bullion has the ISO currency code of XPT.
Palladium is a chemical element with symbol Pd and atomic number 46. It is a rare silver white transition metal of the platinum group, resembling platinum chemically. It was discovered in platinum ores in 1803, and named after the asteroid Pallas by William Hyde Wollaston.
Palladium is usually found as a free metal, alloyed with others in the platinum group. It is commercially extracted from copper-nickel ores. Palladium has a great affinity for hydrogen, being able to absorb 900 times its own volume of the gas. Palladium metal and its complexes are often used in catalysis such as in catalytic converters on cars, palladium on carbon used in organic chemistry, and other coupling reactions. As a precious metal, it is sometimes used in jewellery, and has the ISO currency code of XPD. Palladium as an investment has attracted recent investment interests. In early 2007, several ETFs backed by physical palladium were launched, including London ETF Security and ZKB Palladium ETF.
Silver is a chemical element with the symbol Ag (Latin: argentum) and atomic number 47. A soft white lustrous transition metal, it has the highest electrical and thermal conductivity for a metal. It occurs as a free metal (native silver) as well as various minerals such as argentite and chlorargyrite. Most silver is produced as a by-product of copper, gold, lead, and zinc mining.
Silver has been known since antiquity. It has long been valued as a precious metal and used in currency, ornaments and jewellery, as well as utensils (hence the term silverware). Silver bullion has the ISO currency code of XAG. Today, it is also used in photographic film, electrical contacts, and mirrors. Elemental silver is also used to catalyze chemical reactions.Silver has certain antimicrobial activity. In the past, dilute solutions of silver nitrate were used as disinfectants, though this has been supplanted by other treatments.
Steel is an alloy of iron and maximum 2.1% carbon. The strength increases with the contents of carbon. Low-carbon steel (less than 0.3 % carbon) is generally used for common industrial products such as nuts, sheets and tubes.Medium carbon steel (0.3 to 0.6 % carbon) is stronger than low carbon steel and used for automotive and machinery applications.High carbon steel (more than 0.6 % carbon), is strong, hard, and wear resistant and is used for cutting tools, springs and cutlery.
High Tensile Steel
High tensile steel may have ten times the tensile strength of wood, and more than twice that of mild steel, but it would be a mistake to overestimate the importance of this single quantity, as Fuller seems to do (see Steel).
The toughness of metals is generally reduced by the process of increasing their tensile strengths, but the failure of a structure may be due largely to the stiffness, rather than the strength of the materials used.
The larger the structure of buildings and ships, and so on, the lower the acceptable stress, for safety reasons. It follows that high strength metals are more safely used in small structures. This should perhaps be borne in mind when contemplating megastructures.
Stainless steel is very corrosion resistant, strong, and ductile. Stainless steel contains a minimum of 11 % chromium (wt.), as well as nickel and other alloying elements.In presence of oxygen (air) a thin, hard adherent film of chromium oxide develops on the surface. The film protects the metal from corrosion (passivation). The film builds up again if the surface is scratched.
With increased carbon content, the strength of stainless steel increases and corrosion resistance is reduced.
Tantalum (formerly tantalium) is a chemical element in the periodic table that has the symbol Ta and atomic number 73. A rare, hard, blue-gray, lustrous, transition metal, tantalum is highly corrosion-resistant and occurs naturally in the mineral tantalite.
Tellurium is a chemical element that has the symbol Te and atomic number 52. A brittle silver-white metalloid which looks like tin, tellurium is chemically related to selenium and sulfur. Tellurium is primarily used in alloys and as a semiconductor.
Used as coating in foot tins and casseroles. Bronze is an alloy made from copper and tin.Earlier used for household plates, mugs and canclestics, mainly due to the low melting point and following castability.Pure tin is unstable below room temperature were it disintegrates into white powder (called tin pest). Therefore normally alloyed with small amounts of bismut, antimon and lead.
Pure titanium has excellent corrosion resistance and a high strength-to-weight ratio at both room and elevated temperatures.This makes titanium attractive for applications including aircraft, jet-engines, racing cars, as well as chemical and marine components.Properties like workability, strength and hardenability, can be improved by adding alloying elements. The most common are aluminium, vanadium, molybdenum and manganese.
Tungsten has the highest melting point of any metal (3410 C), and thus it is characterised by high strength at elevated temperatures. Disadvantages are high density, brittleness and poor resistance to oxidation.Tungsten and its alloys are used for applications involving temperatures above 1650 C (e.g. nozzle throat lines in missiles, hottest parts of jet and rocket engines). The filament wire in incandescent bulbs is made of pure tungsten by powder technology.
An inexpensive and weather proof material. Used for roofs on houses and roof gutters. Earlier used for kitchen zincs, but now replaced by stainless steel that is stronger, harder and more corrosion resistant.Often used as protective coating on steel (galvanized) to improve corrosion resistance. Due to the low melting point and good castability it is often used in products with low strength requirements, like beer openers and door handles.Zinc and copper are the 2 major alloying elements in brass.