Constuct Material

Concret ……………………………………………..Type of concrete

1.Mix designModern concrete mix designs can be complex. The choice of a concrete mix depends on the need of the project both in terms of strength and appearance and in relation to local legislation and building codes.

The design begins by determining the requirements of the concrete. These requirements take into consideration the weather conditions that the concrete will be exposed to in service, and the required design strength. The compressive strength of a concrete is determined by taking standard molded, standard-cured cylinder samples.

Many factors need to be taken into account, from the cost of the various additives and aggregates, to the trade offs between, the "slump" for easy mixing and placement and ultimate performance.

A mix is then designed using cement (Portland or other cementitious material), coarse and fine aggregates, water and chemical admixtures. The method of mixing will also be specified, as well as conditions that it may be used in.

This allows a user of the concrete to be confident that the structure will perform properly.

Various types of concrete have been developed for specialist application and have become known by these names.

Concrete mixes can also be designed using software programs. Such software provides the user an opportunity to select their preferred method of mix design and enter the material data to arrive at proper mix designs.

Old concrete recipesConcrete has been used since ancient times. Regular Roman concrete for example was made from volcanic ash (pozzolana), and hydrated lime. Roman concrete was superior to other concrete

recipes (for example, those consisting of only sand and lime)[1] used by other nations. Besides volcanic ash for making regular Roman concrete, brick dust can also be utilized. Besides regular Roman concrete, the Romans also invented hydraulic concrete, which they made from volcanic ash and clay.

Modern concreteRegular concrete is the lay term for concrete that is produced by following the mixing instructions that are commonly published on packets of cement, typically using sand or other common material as the aggregate, and often mixed in improvised containers. The ingredients in any particular mix depends on the nature of the application. Regular concrete can typically withstand a pressure from about 10 MPa (1450psi) to 40 MPa (5800 psi), with lighter duty uses such as blinding concrete having a much lower MPa rating than structural concrete. Many types of pre-mixed concrete are available which include powdered cement mixed with an aggregate, needing only water.

Typically, a batch of concrete can be made by using 1 part Portland cement, 2 parts dry sand, 3 parts dry stone, 1/2 part water. The parts are in terms of weight – not volume. For example, 1-cubic-foot (0.028 m3) of concrete would be made using 22 lb (10.0 kg) cement, 10 lb (4.5 kg) water, 41 lb (19 kg) dry sand, 70 lb (32 kg) dry stone (1/2" to 3/4" stone). This would make 1-cubic-foot (0.028 m3) of concrete and would weigh about 143 lb (65 kg). The sand should be mortar or brick sand (washed and filtered if possible) and the stone should be washed if possible. Organic materials (leaves, twigs, etc.) should be removed from the sand and stone to ensure the highest strength.

High-strength concreteHigh-strength concrete has a compressive strength greater than 40 MPa (5800 psi). In the UK, BS EN 206-1[2] defines High strength concrete as concrete with a compressive strength class higher than C50/60. High-strength concrete is made by lowering the water-cement (W/C) ratio to 0.35 or lower. Often silica fume is added to prevent the formation of free calcium hydroxide crystals in the cement matrix, which might reduce the strength at the cement-aggregate bond.

Low W/C ratios and the use of silica fume make concrete mixes significantly less workable, which is particularly likely to be a problem in high-strength concrete applications where dense rebar cages are likely to be used. To compensate for the reduced workability, superplasticizers are commonly added to high-strength mixtures. Aggregate must be selected carefully for high-strength mixes, as weaker aggregates may not be strong enough to resist the loads imposed on the concrete and cause failure to start in the aggregate rather than in the matrix or at a void, as normally occurs in regular concrete.

In some applications of high-strength concrete the design criterion is the elastic modulus rather than the ultimate compressive strength.

Stamped concreteStamped concrete is an architectural concrete which has a superior surface finish. After a concrete floor has been laid, floor hardeners (can be pigmented) are impregnated on the surface and a mold which may be textured to replicate a stone / brick or even wood is stamped on to give an attractive textured surface finish. After sufficient hardening the surface is cleaned and generally sealed to give a protection. The wear resistance of stamped concrete is generally excellent and hence found in applications like parking lots, pavements, walkways etc.

High-performance concreteHigh-performance concrete (HPC) is a relatively new term for concrete that conforms to a set of standards above those of the most common applications, but not limited to strength. While all high-strength concrete is also high-performance, not all high-performance concrete is high-strength. Some examples of such standards currently used in relation to HPC are:

Ease of placement

Compaction without segregation

Early age strength

Long-term mechanical properties

Permeability

Density

Heat of hydration

Toughness

Volume stability

Long life in severe environments

Depending on its implementation, environmental[3]

Ultra-high-performance concreteUltra-high-performance concrete is a new type of concrete that is being developed by agencies concerned with infrastructure protection. UHPC is characterized by being a steel fibre-reinforced cement composite material with compressive strengths in excess of 150 MPa, up to and possibly exceeding 250 MPa.[4][5][6] UHPC is also characterized by its constituent material make-up: typically fine-grained sand, silica fume, small steel fibers, and special blends of high-strength Portland cement. Note that there is no large aggregate. The current types in production (Ductal, Taktl, etc.) differ from normal concrete in compression by their strain hardening, followed by sudden brittle failure. Ongoing research into UHPC failure via tensile and shear failure is being conducted by multiple government agencies and universities around the world.

Micro-reinforced ultra-high-performance concrete

Micro-reinforced ultra-high-performance concrete is the next generation of UHPC. In addition to high compressive strength, durability and abrasion resistance of UHPC, micro-reinforced UHPC is characterized by extreme ductility, energy absorption and resistance to chemicals, water and temperature.[7] The continuous, multi-layered, three dimensional micro-steel mesh exceeds UHPC in durability, ductility and strength. The performance of the discontinuous and scattered fibers in UHPC is relatively unpredictable. Micro-reinforced UHPC is used in blast, ballistic and earthquake resistant construction, structural and architectural overlays, and complex facades.

Ducon was the early developer of micro-reinforced UHPC,[8][9] which has been used in the construction of new World Trade Center in New York.[10][11][12]

Self-consolidating concreteThe defects in concrete in Japan were found to be mainly due to high water-cement ratio to increase workability. Poor compaction occurred mostly because of the need for speedy construction in the 1960s and 1970s. Hajime Okamura envisioned the need for concrete which is highly workable and does not rely on the mechanical force for compaction. During the 1980s, Okamura and his Ph.D. student Kazamasa Ozawa at the University of Tokyo developed self-compacting concrete (SCC) which was cohesive, but flowable and took the shape of the formwork without use of any mechanical compaction. SCC is known as self-consolidating concrete in the United States.

SCC is characterized by the following:

extreme fluidity as measured by flow, typically between 650–750 mm on a flow table, rather than slump (height)

no need for vibrators to compact the concrete

easier placement

no bleeding, or aggregate segregation

increased liquid head pressure, which can be detrimental to safety and workmanship

SCC can save up to 50% in labor costs due to 80% faster pouring and reduced wear and tear on formwork.

In 2005, self-consolidating concretes accounted for 10–15% of concrete sales in some European countries. In the precast concrete industry in the U.S., SCC represents over 75% of concrete production. 38 departments of transportation in the US accept the use of SCC for road and bridge projects.

This emerging technology is made possible by the use of polycarboxylates plasticizer instead of older naphthalene-based polymers, and viscosity modifiers to address aggregate segregation.

Vacuum concrete

Vacuum concrete, made by using steam to produce a vacuum inside a concrete mixing truck to release air bubbles inside the concrete, is being researched. The idea is that the steam displaces the air normally over the concrete. When the steam condenses into water it will create a low pressure over the concrete that will pull air from the concrete. This will make the concrete stronger due to there being less air in the mixture. A drawback is that the mixing has to be done in a mostly airtight container.

The final strength of concrete is increased by about 25%. Sufficient decrease in The permeability of concrete is sufficient decreased. Vacuum concrete stiffens very rapidly so that the formworks can be removed within 30 minutes of casting even on columns of 20 ft. high. This is of considerable economic value, particularly in a precast factory as the forms can be reused at frequent intervals. The bond strength of vacuum concrete is about 20% higher. The density of vacuum concrete is higher. The surface of vacuum concrete is entirely free from pitting and the uppermost 1/16 inch is highly resistant to abrasion. These characteristics are of special importance in the construction of concrete structures which are to be in contact with flowing water at a high velocity. It bonds well to old concrete and can, therefore, be used for resurfacing road slabs and other repair work - See more at: http://civiltoday.com/civil-engineering-materials/concrete/27-vacuum-concrete-definition-advantages#sthash.c17jlbZ8.dpuf

ShotcreteShotcrete (also known by the trade name Gunite) uses compressed air to shoot concrete onto (or into) a frame or structure. The greatest advantage of the process is that shotcrete can be applied overhead or on vertical surfaces without formwork. It is often used for concrete repairs or placement on bridges, dams, pools, and on other applications where forming is costly or material handling and installation is difficult. Shotcrete is frequently used against vertical soil or rock surfaces, as it eliminates the need for formwork. It is sometimes used for rock support, especially in tunneling. Shotcrete is also used for applications where seepage is an issue to limit the amount of water entering a construction site due to a high water table or other subterranean sources. This type of concrete is often used as a quick fix for weathering for loose soil types in construction zones.

There are two application methods for shotcrete.

dry-mix – the dry mixture of cement and aggregates is filled into the machine and conveyed with compressed air through the hoses. The water needed for the hydration is added at the nozzle.

wet-mix – the mixes are prepared with all necessary water for hydration. The mixes are pumped through the hoses. At the nozzle compressed air is added for spraying.

For both methods additives such as accelerators and fiber reinforcement may be used.[13]

LimecreteLimecrete or lime concrete is concrete where cement is replaced by lime.[14] One successful formula was developed in the mid-1800s by Dr. John E. Park.[15] We know that lime has been used since Roman Times either as mass foundation concretes or as lightweight concretes using a variety of aggregates combined with a wide range of pozzolans (fired materials) that help to achieve increased strength and speed of set. This meant that lime could be used in a much wider variety of applications than previously such as floors, vaults or domes. Over the last decade, there has been a renewed interest in using lime for these applications again. This is because of environmental benefits and potential health benefits, when used with other lime products.

Environmental Benefits

Lime is burnt at a lower temperature than cement and so has an immediate energy saving of 20% (although kilns etc. are improving so figures do change). A standard lime mortar has about 60-70% of the embodied energy of a cement mortar. It is also considered to be more environmentally friendly because of its ability, through carbonation, to re-absorb its own weight in Carbon Dioxide (compensating for that given off during burning).

Lime mortars allow other building components such as stone, wood and bricks to be reused and recycled because they can be easily cleaned of mortar/limewash.

Lime enables other natural and sustainable products such as wood (including woodfibre, wood wool boards), hemp, straw etc. to be used because of its ability to control moisture (if cement were used, these buildings would compost!).

Health Benefits

Lime plaster is hygroscopic (literally means 'water seeking') which draws the moisture from the internal to the external environment, this helps to regulate humidity creating a more comfortable living environment as well as helping to control condensation and mould growth which have been shown to have links to allergies and asthmas.

Lime plasters and limewash are non-toxic, therefore they do not contribute to indoor air pollution unlike some modern paints.

Pervious concretePervious concrete, used in permeable paving, contains a network of holes or voids, to allow air or water to move through the concrete

This allows water to drain naturally through it, and can both remove the normal surface-water drainage infrastructure, and allow replenishment of groundwater when conventional concrete does not.

It is formed by leaving out some or all of the fine aggregate (fines). The remaining large aggregate then is bound by a relatively small amount of Portland cement. When set, typically between 15% and 25% of the concrete volume is voids, allowing water to drain at around 5 gal/ft²/ min (70 L/m²/min) through the concrete.

InstallationPervious concrete is installed by being poured into forms, then screeded off, to level (not smooth) the surface, then packed or tamped into place. Due to the low water content and air permeability, within 5–15 minutes of tamping, the concrete must be covered with a 6-mil poly plastic, or it will dry out prematurely and not properly hydrate and cure.

CharacteristicPervious concrete can significantly reduce noise, by allowing air to be squeezed between vehicle tires and the roadway to escape. This product cannot be used on major U.S. state highways currently due to the high psi ratings required by most states. Pervious concrete has been tested up to 4500 psi so far.

Cellular concreteAerated concrete produced by the addition of an air-entraining agent to the concrete (or a lightweight aggregate such as expanded clay aggregate or cork granules and vermiculite) is sometimes called cellular concrete, lightweight aerated concrete, variable density concrete, Foam Concrete and lightweight or ultra-lightweight concrete,[16][17] not to be confused with aerated autoclaved concrete, which is manufactured off-site using an entirely different method.

In the 1977 work on A Pattern Language: Towns, Buildings and Construction, architect Christopher Alexander wrote in pattern 209 on Good Materials:

Regular concrete is too dense. It is heavy and hard to work. After it sets one cannot cut into it, or nail into it. And it's [sic] surface is ugly, cold, and hard in feeling unless covered by expensive finishes not integral to the structure.

And yet concrete, in some form, is a fascinating material. It is fluid, strong, and relatively cheap. It is available in almost every part of the world. A University of California professor of engineering sciences, P. Kumar Mehta, has even just recently found a way of converting abandoned rice husks into Portland cement.

Is there any way of combining all these good qualities of concrete and also having a material which is light in weight, easy to work, with a pleasant finish? There is. It is possible to use a whole range of ultra-lightweight concretes which have a density and compressive strength very similar to that of wood. They are easy to work with, can be nailed with ordinary nails, cut with a saw, drilled with wood-working tools, easily repaired.

We believe that ultra-lightweight concrete is one of the most fundamental bulk materials of the future.

The variable density is normally described in kg per m³, where regular concrete is 2400 kg/m³. Variable density can be as low as 300 kg/m³,[16] although at this density it would have no structural integrity at all and would function as a filler or insulation use only. The variable density reduces strength[16] to increase thermal[16] and acoustical insulation by replacing the dense heavy concrete with air or a light material such as clay, cork granules and vermiculite. There are many competing products that use a foaming agent that resembles shaving cream to mix air bubbles in with the concrete. All accomplish the same outcome: to displace concrete with air.

Properties of Foamed Concrete[18]

Dry Density (kg/m3)

7-day Compressive

Strength (N/mm2)

Thermal Conductivity*

(W/mK)

Modulus of Elasticity (kN/mm2)

Drying Shrinkage

(%)

400 0.5 – 1.0 0.10 0.8 – 1.0 0.30 – 0.35

600 1.0 – 1.5 0.11 1.0 – 1.5 0.22 – 0.25

800 1.5 – 2.0 0.17 – 0.23 2.0 – 2.5 0.20 – 0.22

1000 2.5 – 3.0 0.23 – 0.30 2.5 – 3.0 0.18 – 0.15

1200 4.5 – 5.5 0.38 – 0.42 3.5 – 4.0 0.11 – 0.19

1400 6.0 – 8.0 0.50 – 0.55 5.0 – 6.0 0.09 – 0.07

1600 7.5 – 10.0 0.62 – 0.66 10.0 – 12.0 0.07 – 0.06

Applications of foamed concrete include:

Roof Insulation

Blocks and Panels for Walls

Levelling Floors

Void Filling

Road Sub-Bases and maintenance

Bridge Abutments and repairs

Ground Stabilisation

Cork-cement compositesWaste Cork granules are obtained during production of bottle stoppers from the treated bark of Cork oak.[19] These granules have a density of about 300 kg/m³, lower than most lightweight aggregates used for making lightweight concrete. Cork granules do not significantly influence cement hydration, but cork dust may. [20] Cork cement composites have several advantages over standard concrete, such as lower thermal conductivities, lower densities and good energy absorption characteristics. These composites can be made of density from 400 to 1500 kg/m³, compressive strength from 1 to 26 MPa, and flexural strength from 0.5 to 4.0 MPa.

Roller-compacted concreteMain article: Roller-compacted concrete

Roller-compacted concrete, sometimes called rollcrete, is a low-cement-content stiff concrete placed using techniques borrowed from earthmoving and paving work. The concrete is placed on the surface to be covered, and is compacted in place using large heavy rollers typically used in earthwork. The concrete mix achieves a high density and cures over time into a strong monolithic block.[21] Roller-compacted concrete is typically used for concrete pavement, but has also been used to build concrete dams, as the low cement content causes less heat to be generated while curing than typical for conventionally placed massive concrete pours.

Glass concreteThe use of recycled glass as aggregate in concrete has become popular in modern times, with large scale research being carried out at Columbia University in New York. This greatly enhances the aesthetic appeal of the concrete. Recent research findings have shown that concrete made with recycled glass aggregates have

shown better long-term strength and better thermal insulation due to its better thermal properties of the glass aggregates.[22]

Asphalt concreteStrictly speaking, asphalt is a form of concrete as well, with bituminous materials replacing cement as the binder.

Rapid strength concreteThis type of concrete is able to develop high resistance within few hours after being manufactured. This feature has advantages such as removing the formwork early and to move forward in the building process at record time, repair road surfaces that become fully operational in just a few hours.

Rubberized concreteWhile "rubberized asphalt concrete" is common, rubberized Portland cement concrete ("rubberized PCC") is still undergoing experimental tests, as of 2009.[23] [24] [25][26]

Polymer concretePolymer concrete is concrete which uses polymers to bind the aggregate. Polymer concrete can gain a lot of strength in a short amount of time. For example, a polymer mix may reach 5000 psi in only four hours. Polymer concrete is generally more expensive than conventional concretes.

Geopolymer concreteGeopolymer cement is an alternative to ordinary Portland cement and is used to produce Geopolymer concrete by adding regular aggregates to a geopolymer cement slurry. It is made from inorganic aluminosilicate (Al-Si) polymer compounds that can utilise 100% recycled industrial waste (e.g. fly ash, copper slag) as the manufacturing inputs resulting in up to 80% lower carbon dioxide emissions. Greater chemical and thermal resistance, and better mechanical properties, are said to be achieved for geopolymer concrete at both atmospheric and extreme conditions.

Similar concretes have not only been used in Ancient Rome (see Roman cement), but also in the former Soviet Union in the 1950s and 1960s. Buildings in Ukraine are still standing after 45 years, so this kind of formulation has a sound track record.

Refractory cementHigh-temperature applications, such as masonry ovens and the like, generally require the use of a refractory cement; concretes based on Portland cement can be damaged or destroyed by elevated temperatures, but refractory concretes are better able to withstand such conditions. Materials may include calcium aluminate cements, fire clay, ganister and minerals high in aluminum.

Innovative mixturesOn-going research into alternative mixtures and constituents has identified potential mixtures that promise radically different properties and characteristics.

One university has identified a mixture with much smaller crack propagation that does not suffer the usual cracking and subsequent loss of strength at high levels of tensile stress. Researchers have been able to take mixtures beyond 3 percent strain, past the more typical 0.1% point at which failure occurs.[27]

Other institutions have identified magnesium silicate (talc) as an alternative ingredient to replace Portland cement in the mix. This avoids the usual high-temperature production process that is very energy andgreenhouse gas intensive and actually absorbs carbon dioxide while it cures.[28][29]

Gypsum concreteMain article: Gypsum concrete

Gypsum concrete is a building material used as a floor underlayment [30]  used in wood-frame and concrete construction for fire ratings,[30] sound reduction,[30] radiant heating,[31] and floor leveling. It is a mixture ofgypsum, Portland cement, and sand.[30]

References1. Jump up^ "Historic concrete recipes in ancient times, demonstrated by Colin

Richards, experimental archaeologist". Channel.nationalgeographic.com. 2012-06-11. Retrieved 2012-09-11.

2. Jump up^ BS EN 206-13. Jump up^ Cementing the future. Time (2008-12-04). Retrieved on 2012-04-20.4. Jump up^ Redaelli, Dario; Muttoni, Aurelio (May 2007). "Tensile Behaviour of

Reinforced Ultra-High Performance Fiber Reinforced Concrete Elements"  (PDF). Proceedings of CEB-FIP Symposium Dubrovnik(Ecole Polytechnique Fédérale de Lausanne). Concrete Structures. Retrieved 23 November 2015.

5. Jump up^ "Ultra High Performance Fibre-Reinforced Concretes." Association Francaise de Genie Civil, 2002.

6. Jump up^ "Ultra-High Performance Concrete: A State-of-the-Art Report for the Bridge Community"  (PDF). FHWA-HRt-13-060: Federal Highway Administration. June 2013. Retrieved 23 November 2015.

7. Jump up^ Hauser, Stephan (2005-02-01).  "Micro-reinforced high performance concrete opens up new horizons"  (PDF). Concrete Plant International. pp. 66–67. Retrieved 23 November 2015. Press release from Ducon GMBH, Mörfelden-Walldorf, Germany

8. Jump up^ D'mello, Sandhya (2005-03-25).  "Explosion resistant cement in UAE". Khaleej Times. Retrieved 23 November 2015.

9. Jump up^ Miller, Steven H. (2007-10-01).  "The “Explosion” in Blast Resistant Construction". Masonry Construction. Retrieved 23 November 2015.

10. Jump up^ Stolz, Alexander (2014-07-01).  "Formula calculates thickness of bombproof concrete". Efringen-Kirchen, Germany: Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut EMI. Retrieved23 November 2015. Press release.

11. Jump up^ Rabicoff, Richard (2012-08-21).  "Technology Makes Engineering Firm a Concrete Success". bmore Media. Retrieved 23 November 2015.

12. Jump up^ "1 World Trade Center, NYC, protective measures + architectural concrete". Ducon GMBH. Retrieved 23 November 2015.

13. Jump up^ American Shotcrete Association Homepage. Shotcrete.org. Retrieved on 2012-04-20.

14. Jump up^ An Investigation Into The Feasibility Of Timber And Limecrete Composite Flooring. Istructe.org. Retrieved on 2012-04-20.

15. Jump up^ John Park limecrete. tpwd.state.tx.us16. ^ Jump up to:a b c d "Aerated Concrete, Lightweight Concrete, Cellular Concrete and

Foamed Concrete". Retrieved 2012-04-20.17. Jump up^ Light Weight Concrete. Ecosmarte.com.au. Retrieved on 2012-04-20.18. Jump up^ Foamed Concrete Composition and Properties, British Cement

Association, 1994.19. Jump up^ Gibson, L.J. & Ashby, M.F. 1999. Cellular Solids: Structure and

Properties; 2nd Edition (Paperback), Cambridge Uni. Press. pp.453–467.20. Jump up^ Karade S.R., Irle M.A., Maher K. 2006. Influence of granule properties

and concentration on cork-cement compatibility. Holz als Roh- und Werkstoff. 64: 281–286 (DOI 10.1007/s00107-006-0103-2).

21. Jump up^ Roller-Compacted Concrete (RCC) Pavements | Portland Cement Association (PCA). Cement.org. Retrieved on 2012-04-20.

22. Jump up^ K.H. Poutos, A.M. Alani, P.J. Walden, C.M. Sangha. (2008). Relative temperature changes within concrete made with recycled glass aggregate. Construction and Building Materials, Volume 22, Issue 4, Pages 557–565.

23. Jump up^ Refer this Link to Know Some Useful Facts About Concrete

24. Jump up^ Emerging Construction Technologies. Ecn.purdue.edu. Retrieved on 2012-04-20.

25. Jump up^ ASU researcher puts recalled Firestone tires to good use. Innovations-report.de (2002-07-26). Retrieved on 2012-04-20.

26. Jump up^ Experimental Study on Strength, Modulus of Elasticity, and Damping Ratio of Rubberized Concrete. Pubsindex.trb.org. Retrieved on 2012-04-20.

27. Jump up^ Self-healing concrete for safer, more durable infrastructurePhysorg.com April 22nd, 2009

28. Jump up^ Revealed: The cement that eats carbon dioxide Alok Jha, The Guardian, 31 December 2008

29. Jump up^ Eco-Cement TecEco Pty30. ^ Jump up to:a b c d Grady, Joe (2004-06-01). "The finer points of bonding to gypsum

concrete underlayment.". National Floor Trends. Retrieved2009-09-21.31. Jump up^ Grady, Joe (2005-07-01).  "Questionable substrates for ceramic tile and

dimensional stone.". Floor Covering Installer. Retrieved2009-09-21.

Steel type

Steel is an alloy of iron and other elements, primarily carbon, widely used in construction and other applications because of its high tensile strength and low cost. Carbon, other elements, and inclusions within iron act as hardening agents that prevent the movement of dislocations that otherwise occur in the crystal lattices of iron atoms.

The carbon in typical steel alloys may contribute up to 2.1% of its weight. Varying the amount of alloying elements, their formation in the steel either as solute elements, or as precipitated phases, retards the movement of those dislocations that make iron comparatively ductile and weak, and thus controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel's strength compared to pure iron is only possible at the expense of ductility, of which iron has an excess.

Although steel had been produced in bloomery furnaces for thousands of years, steel's use expanded extensively after more efficient production methods were devised in the 17th century for blister steel and thencrucible steel. With the invention of the Bessemer process in the mid-19th century, a new era of mass-produced steel began. This was followed by Siemens-Martin process and then Gilchrist-Thomas process that refined the quality of steel. With their introductions, mild steel replaced wrought iron.

Further refinements in the process, such as basic oxygen steelmaking (BOS), largely replaced earlier methods by further lowering the cost of production and increasing the quality of the metal. Today, steel is one of the most common materials in the world, with more than 1.3 billion tons produced annually. It is a major component in buildings, infrastructure, tools, ships,automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades defined by assortedstandards organizations.

Definitions and related materialsThe noun steel originates from the Proto-Germanic adjective stakhlijan (made of steel), which is related tostakhla (standing firm). Steel is used as an adjective from c. 1200. Steel wool is known since 1896, and steel drum from 1952.[1]

The carbon content of steel is between 0.002% and 2.1% by weight for plain iron-carbon alloys. These values vary depending on alloying elements such as manganese, chromium, nickel, iron, tungsten, carbon and so on. Basically, steel is an iron-carbon alloy that does not

undergo eutectic reaction. In contrast, cast iron does undergo eutectic reaction, suddenly solidifying into solid phases at exactly the same temperature. Too little carbon content leaves (pure) iron quite soft, ductile, and weak. Carbon contents higher than those of steel make an alloy, commonly called pig iron, that is brittle (not malleable). While iron alloyed with carbon is called carbon steel, alloy steel is steel to which other alloying elements have been intentionally added to modify the characteristics of steel. Common alloying elements include: manganese, nickel, chromium, molybdenum, boron,titanium, vanadium, tungsten, cobalt, and niobium.[2] Additional elements are also important in steel:phosphorus, sulfur, silicon, and traces of oxygen, nitrogen, and copper.

Alloys with a higher than 2.1% carbon content, depending on other element content and possibly on processing, are known as cast iron. Cast iron is not malleable even when hot, but it can be formed by casting as it has a lower melting point than steel and good castability properties.[2] Certain compositions of cast iron, while retaining the economies of melting and casting, can be heat treated after casting to make malleable iron or ductile ironobjects. Steel is also distinguishable from wrought iron (now largely obsolete), which may contain a small amount of carbon but large amounts of slag.

Material properties[edit]

Iron-carbon phase diagram, showing the conditions necessary to form different phases

Iron is commonly found in the Earth'scrust in the form of an ore, usually an iron oxide, such as magnetite, hematiteetc. Iron is extracted from iron ore by removing the oxygen through combination with a preferred chemical partner such as carbon that is lost to the atmosphere as carbon dioxide. This process, known as smelting, was first applied to metals with lower meltingpoints, such as tin, which melts at approximately 250 °C (482 °F) andcopper, which melts at approximately 1,100 °C (2,010 °F). In comparison, cast iron melts at approximately 1,375 °C (2,507 °F).[3] Small quantities of iron were smelted in ancient times, in the solid state, by heating the ore buried in acharcoal fire and welding the metal together with a hammer, squeezing out the impurities. With care, the carbon content could be controlled by moving it around in the fire.

All of these temperatures could be reached with ancient methods that have been used since the Bronze Age. Since the oxidation rate of iron increases rapidly beyond 800 °C (1,470 °F), it is important that smelting take place in a low-oxygen environment. Unlike copper and tin, liquid or solid iron dissolves carbon quite readily. Smelting, using carbon to reduce iron oxides, results in an alloy (pig iron) that retains too much carbon to be called steel.[3] The excess carbon and other impurities are removed in a subsequent step.

Other materials are often added to the iron/carbon mixture to produce steel with desired properties. Nickel andmanganese in steel add to its tensile strength and make the austenite form of the iron-carbon solution more stable, chromium increases hardness and melting temperature, and vanadium also increases hardness while making it less prone to metal fatigue.[4]

To inhibit corrosion, at least 11% chromium is added to steel so that a hard oxide forms on the metal surface; this is known as stainless steel. Tungsten interferes with the formation of cementite, allowing martensite to preferentially form at slower quench rates, resulting in high speed steel. On the other hand, sulfur, nitrogen, andphosphorus make steel more brittle, so these commonly found elements must be removed from the steel melt during processing.[4]

The density of steel varies based on the alloying constituents but usually ranges between 7,750 and 8,050 kg/m3(484 and 503 lb/cu ft), or 7.75 and 8.05 g/cm3 (4.48 and 4.65 oz/cu in).[5]

Even in a narrow range of concentrations of mixtures of carbon and iron that make a steel, a number of different metallurgical structures, with very different properties can form. Understanding such properties is essential to making quality steel. At room temperature, the most stable form of pure iron is the body-centered cubic (BCC) structure called ferrite or α-iron. It is a fairly soft metal that can dissolve only a small concentration of carbon, no more than 0.005% at 0 °C (32 °F) and 0.021 wt% at 723 °C (1,333 °F). At 910 °C pure iron transforms into aface-centered cubic (FCC) structure, called austenite or γ-iron. The FCC structure of austenite can dissolve considerably more carbon, as much as 2.1%[6] (38 times that of ferrite) carbon at 1,148 °C (2,098 °F), which reflects the upper carbon content of steel, beyond which is cast iron.[7]

When steels with less than 0.8% carbon (known as a hypoeutectoid steel), are cooled, the austenitic phase (FCC) of the mixture attempts to revert to the ferrite phase (BCC). The carbon no longer fits within the FCC structure, resulting in an excess of carbon. One way for carbon to leave the austenite is for it to precipitate out of solution as cementite, leaving behind a surrounding phase of BCC iron that is low enough in carbon to take the form of ferrite, resulting in a ferrite matrix with cementite inclusions. Cementite is a hard and brittle intermetallic compound with the chemical formula of Fe3C. At the eutectoid, 0.8% carbon, the cooled structure takes the form of pearlite, named for its resemblance to mother of pearl. On a larger scale, it appears as a lamellar structure of ferrite and cementite. For steels that have more than 0.8% carbon, the cooled structure takes the form of pearlite and cementite.[8]

Perhaps the most important polymorphic form of steel is martensite, a metastable phase that is significantly stronger than other steel phases. When the steel is in an austenitic phase and then quenched rapidly, it forms into martensite, as the atoms "freeze" in place when the cell structure changes from FCC to a distorted form of BCC as the atoms do not have time enough to migrate and form the cementite compound. Depending on the carbon content, the martensitic phase takes different forms. Below approximately 0.2% carbon, it takes on a ferrite BCC crystal form, but at higher carbon content it takes a body-centered tetragonal (BCT) structure. There is no thermal activation energy for the transformation from austenite to martensite. Moreover, there is no compositional change so the atoms generally retain their same neighbors. [9]

Martensite has a lower density than does austenite, so that the transformation between them results in a change of volume. In this case, expansion occurs. Internal stresses from this expansion generally take the form ofcompression on the crystals of martensite and tension on the remaining ferrite, with a fair amount of shear on both constituents. If quenching is done improperly, the internal stresses can cause a part to shatter as it cools. At the very least, they cause internal work hardening and other microscopic imperfections. It is common for quench cracks to form when steel is water quenched, although they may not always be visible.[10]

Heat treatment[edit]

There are many types of heat treating processes available to steel. The most common are annealing, quenching, and tempering. Heat treatment is effective on hypereutectoid steel. Hypoeutectoid steel does not harden from heat treatment. Annealing is the process of heating the steel to a sufficiently high temperature to soften it. This process goes through three phases: recovery, recrystallization, and grain growth. The temperature required to anneal steel depends on the type of annealing to be achieved and the constituents of the alloy.[11]

Quenching and tempering first involves heating the steel to the austenite phase then quenching it in water or oil. This rapid cooling results in a hard but brittle martensitic structure.[9] The steel is then tempered, which is just a specialized type of annealing, to reduce brittleness. In this application the annealing (tempering) process transforms some of the martensite into cementite, or spheroidite and hence reduces the internal stresses and defects. The result is a more ductile and fracture-resistant steel.[12]

Steel productionWhen iron is smelted from its ore, it contains more carbon than is desirable. To become steel, it must be reprocessed to reduce the carbon to the correct amount, at which point other elements can be added. In the past, steel facilities would cast the raw cast iron product into ingots which would be stored until use in further refinement processes that resulted in the finished product. In modern facilities, the initial product is close to the final composition and is continuously cast into long slabs, cut and shaped into bars and extrusions and heat treated to produce a final product. Today only a small fraction is cast into ingots. Approximately 96% of steel is continuously cast, while only 4% is produced as ingots.[13]

The ingots are then heated in a soaking pit and hot rolled into slabs,billets, or blooms. Slabs are hot or cold rolled into sheet metal or plates. Billets are hot or cold rolled into bars, rods, and wire. Blooms are hot or cold rolled into structural steel, such as I-beams and rails. In modern steel mills these processes often occur in one assembly line, with ore coming in and finished steel products coming out.[14] Sometimes after a steel's final rolling it is heat treated for strength, however this is relatively rare.[15]

Steel industryIt is common today to talk about "the iron and steel industry" as if it were a single entity, but historically they were separate products. The steel industry is often considered an indicator of economic progress, because of the critical role played by steel in infrastructural and overall economic development.[54]

In 1980, there were more than 500,000 U.S. steelworkers. By 2000, the number of steelworkers fell to 224,000.[55]

The economic boom in China and India has caused a massive increase in the demand for steel in recent years. Between 2000 and 2005, world steel demand increased by 6%. Since 2000, several Indian[56] and Chinese steel firms have risen to prominence like Tata Steel (which bought Corus

Group in 2007), Shanghai Baosteel Group Corporationand Shagang Group. ArcelorMittal is however the world's largest steel producer.

In 2005, the British Geological Survey stated China was the top steel producer with about one-third of the world share; Japan, Russia, and the US followed respectively. [57]

In 2008, steel began trading as a commodity on the London Metal Exchange. At the end of 2008, the steel industry faced a sharp downturn that led to many cut-backs.[58]

The world steel industry peaked in 2007. That year, ThyssenKrupp spent $12 billion to build the two most modern mills in the world, in Calvert, Alabama and Sepetiba, Rio de Janeiro, Brazil. The worldwide Great Recession starting in 2008, however, sharply lowered demand and new construction, and so prices fell. ThyssenKrupp lost $11 billion on its two new plants, which sold steel below the cost of production.

Recycling[edit]Steel is one of the world's most-recycled materials, with a recycling rate of over 60% globally; [59] in the United States alone, over 82,000,000 metric tons (81,000,000 long tons) was recycled in the year 2008, for an overall recycling rate of 83%

Contemporary steel

Carbon steels[edit]

Modern steels are made with varying combinations of alloy metals to fulfill many purposes.[4] Carbon steel, composed simply of iron and carbon, accounts for 90% of steel production. [2] Low alloy steel is alloyed with other elements, usually molybdenum, manganese, chromium, or nickel, in amounts of up to 10% by weight to improve the hardenability of thick sections.[2] High strength low alloy steel has small additions (usually < 2% by weight) of other elements, typically 1.5% manganese, to provide additional strength for a modest price increase.[61]

Recent Corporate Average Fuel Economy (CAFE) regulations have given rise to a new variety of steel known as Advanced High Strength Steel (AHSS). This material is both strong and ductile so that vehicle structures can maintain their current safety levels while using less material. There are several commercially available grades of AHSS, such as dual-phase steel, which is heat treated to contain both a ferritic and martensitic microstructure to produce a formable, high strength steel.[62] Transformation Induced Plasticity (TRIP) steel involves special alloying and heat treatments to stabilize amounts of austenite at room temperature in normally austenite-free low-alloy ferritic steels. By applying strain, the austenite undergoes aphase transition to martensite without the addition of

heat.[63] Twinning Induced Plasticity (TWIP) steel uses a specific type of strain to increase the effectiveness of work hardening on the alloy.[64]

Carbon Steels are often galvanized, through hot-dip or electroplating in zinc for protection against rust.[65]

Alloy steels[edit]

Stainless steels contain a minimum of 11% chromium, often combined with nickel, to resist corrosion. Some stainless steels, such as the ferritic stainless steels are magnetic, while others, such as the austenitic, are nonmagnetic.[66] Corrosion-resistant steels are abbreviated as CRES.

Some more modern steels include tool steels, which are alloyed with large amounts of tungsten and cobalt or other elements to maximize solution hardening. This also allows the use of precipitation hardening and improves the alloy's temperature resistance.[2] Tool steel is generally used in axes, drills, and other devices that need a sharp, long-lasting cutting edge. Other special-purpose alloys include weathering steels such as Cor-ten, which weather by acquiring a stable, rusted surface, and so can be used un-painted.[67] Maraging steel is alloyed with nickel and other elements, but unlike most steel contains little carbon (0.01%). This creates a very strong but stillmalleable steel.[68]

Eglin steel uses a combination of over a dozen different elements in varying amounts to create a relatively low-cost steel for use in bunker buster weapons. Hadfield steel (after Sir Robert Hadfield) or manganese steel contains 12–14% manganese which when abraded strain hardens to form an incredibly hard skin which resists wearing. Examples include tank tracks, bulldozer blade edges and cutting blades on the jaws of life.[69]

In 2016 a breakthrough in creating a strong light aluminium steel alloy which might be suitable in applications such as aircraft was announced by researchers at Pohang University of Science and Technology. Adding small amounts of nickel was found to result in precipitation as nano particles of brittle B2 intermetallic compounds which had previously resulted in weakness. The result was a cheap strong light steel alloy—nearly as strong astitanium at ten percent the cost[70]— which is slated for trial production[when?] at industrial scale by POSCO, a Korean steelmaker.[71][72]

Standards[edit]

Most of the more commonly used steel alloys are categorized into various grades by standards organizations. For example, the Society of Automotive Engineers has a series of grades defining many types of steel.[73] TheAmerican Society for Testing and Materials has a separate set of standards, which define alloys such as A36 steel, the most commonly used structural steel in the United States.[74]

Uses[edit]

A roll of steel wool

Iron and steel are used widely in the construction of roads, railways, other infrastructure, appliances, and buildings. Most large modern structures, such as stadiums and skyscrapers, bridges, and airports, are supported by a steel skeleton. Even those with a concrete structure employ steel for reinforcing. In addition, it sees widespread use in major appliances and cars. Despite growth in usage of aluminium, it is still the main material for car bodies. Steel is used in a variety of otherconstruction materials, such as bolts, nails, and screws and other household products and cooking utensils.[75]

Other common applications include shipbuilding, pipelines, mining,offshore construction, aerospace, white goods (e.g. washing machines),heavy equipment such as bulldozers, office furniture, steel wool, tools, and armour in the form of personal vests or vehicle armour (better known as rolled homogeneous armour in this role).

Historical[edit]

A carbon steel knife

Before the introduction of the Bessemer process and other modern production techniques, steel was expensive and was only used where no cheaper alternative existed, particularly for the cutting edge of knives, razors, swords, and other items where a hard, sharp edge was needed. It was also used for springs, including those used in clocks and watches.[48]

With the advent of speedier and thriftier production methods, steel has become easier to obtain and much cheaper. It has replaced wrought iron for a multitude of purposes. However, the availability

of plastics in the latter part of the 20th century allowed these materials to replace steel in some applications due to their lower fabrication cost and weight.[76] Carbon fiber is replacing steel in some cost insensitive applications such as aircraft, sports equipment and high end automobiles.

Long steel[edit]

A steel bridge

A steel pylon suspending overhead power lines

As reinforcing bars and mesh in reinforced concrete

Railroad tracks

Structural steel  in modern buildings and bridges

Wires

Input to reforging applications

Flat carbon steel[edit]

Major appliances

Magnetic cores

The inside and outside body of automobiles, trains, and ships.

Weathering steel (COR-TEN)[edit]Main article: Weathering steel

Intermodal containers

Outdoor sculptures

Architecture

Highliner  train cars

Stainless steel[edit]

A stainless steel gravy boat

Main article: Stainless steel

Cutlery

Rulers

Surgical instruments

Watches

Guns

Rail passenger vehicles

Tablets

Trash Cans

Low-background steel[edit]Main article: Low-background steel

Steel manufactured after World War II became contaminated with radionuclides due to nuclear weapons testing. Low-background steel, steel manufactured prior to 1945, is used for certain radiation-sensitive applications such as Geiger counters and radiation shielding.

References1. ^ Jump up to:a b c d e Ashby, Michael F. and Jones, David R. H. (1992) [1986]. Engineering Materials

2 (with corrections ed.). Oxford: Pergamon Press.  ISBN 0-08-032532-7.2. ^ Jump up to:a b Smelting. Encyclopædia Britannica. 2007.3. ^ Jump up to:a b c "Alloying of Steels". Metallurgical Consultants. 2006-06-28. Retrieved 2007-02-28.4. Jump up^ Elert, Glenn. "Density of Steel". Retrieved 2009-04-23.5. Jump up^ Sources differ on this value so it has been rounded to 2.1%, however the exact value is

rather academic because plain-carbon steel is very rarely made with this level of carbon. See: Smith & Hashemi 2006 , p. 363—2.08%. Degarmo, Black & Kohser 2003 , p. 75—2.11%. Ashby & Jones 1992 —2.14%.

6. Jump up^ Smith & Hashemi 2006, p. 363.7. Jump up^ Smith & Hashemi 2006, pp. 365–372.8. ^ Jump up to:a b Smith & Hashemi 2006, pp. 373–378.9. Jump up^ "Quench hardening of steel". Retrieved 2009-07-19.10. Jump up^ Smith & Hashemi 2006, p. 249.11. Jump up^ Smith & Hashemi 2006, p. 388.12. Jump up^ Smith & Hashemi 2006, p. 36113. Jump up^ Smith & Hashemi 2006, pp. 361–362.14. Jump up^ Bugayev et al. Savin, p. 22515. ^ Jump up to:a b Hilda Ellis Davidson. The Sword in Anglo-Saxon England: Its Archaeology and

Literature. pp.2016. ^ Jump up to:a b c S. Srinivasan; S. Ranganathan. "Wootz Steel: an advanced material of the ancient

world". Bangalore: Department of Metallurgy, Indian Institute of Science.17. Jump up^ Akanuma, H. (2005). "The significance of the composition of excavated iron fragments

taken from Stratum III at the site of Kaman-Kalehöyük, Turkey". Anatolian Archaeological Studies 14: 147–158.

18. Jump up^ "Ironware piece unearthed from Turkey found to be oldest steel". The Hindu (Chennai, India). 2009-03-26. Retrieved 2009-03-27.

19. Jump up^ "Noricus ensis," Horace, Odes, i. 16.920. Jump up^ "Steel Secret of Spartans Well Kept".21. Jump up^ "Lyle Borst, 89, Nuclear Physicist Who Worked on A-Bomb Project".22. Jump up^ Wagner, Donald B. (1993).  Iron and Steel in Ancient China: Second Impression, With

Corrections. Leiden: E.J. Brill. p. 243. ISBN 90-04-09632-9.23. Jump up^ Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part 3, Civil

Engineering and Nautics. Taipei: Caves Books, Ltd. p. 563.24. Jump up^ Gernet, 69.25. Jump up^ "Civilizations in Africa: The Iron Age South of the Sahara". Washington State University.

Archived from the original on 2007-06-19. Retrieved 2007-08-14.26. Jump up^ Africa's Ancient Steelmakers. Time Magazine, Sept. 25, 1978.27. Jump up^ Wilford, John Noble (1996-02-06).  "Ancient Smelter Used Wind To Make High-Grade

Steel". The New York Times.28. ^ Jump up to:a b Sharada Srinivasan; Srinivasa Ranganathan (2004).  India's Legendary Wootz Steel:

An Advanced Material of the Ancient World. National Institute of Advanced Studies. OCLC 82439861.29. ^ Jump up to:a b Ann Feuerbach, 'An investigation of the varied technology found in swords, sabres

and blades from the Russian Northern Caucasus' IAMS 25 for 2005, pp. 27–43 (p. 29)30. Jump up^ Sharada Srinivasan (1994). "Wootz crucible steel: a newly discovered production site in

South India". Papers from the Institute of Archaeology 5: 49–59. doi:10.5334/pia.60.31. Jump up^ Hobbies – Volume 68, Issue 5 – Page 45. Lghtner Publishing Company (1963)32. Jump up^ Mahathevan, Iravatham (24 June 2010). "An epigraphic perspective on the antiquity of

Tamil". The Hindu (The Hindu Group). Retrieved 31 October 2010.33. Jump up^ Ragupathy, P (28 June 2010). "Tissamaharama potsherd evidences ordinary early Tamils

among population".Tamilnet (Tamilnet). Retrieved 31 October 2010.

34. Jump up^ Needham, Volume 4, Part 1, p. 282.35. Jump up^ Manning, Charlotte Speir. "Ancient and Mediæval India. Volume

2".  ISBN 9780543929433.36. ^ Jump up to:a b c Juleff, G. (1996). "An ancient wind powered iron smelting technology in Sri

Lanka". Nature 379 (3): 60–63.Bibcode:1996Natur.379...60J. doi:10.1038/379060a0.37. ^ Jump up to:a b Herbert Henery Coghlan. (1977). Notes on prehistoric and early iron in the Old World.

pp 99–10038. Jump up^ Sanderson, Katharine (2006-11-15). "Sharpest cut from nanotube sword". Nature

News. doi:10.1038/news061113-11.39. Jump up^ Wayman, M L and Juleff, G (1999). "Crucible Steelmaking in Sri Lanka". Historical

Metallurgy 33 (1): 26.40. Jump up^ Hartwell, Robert (966). "Markets, Technology and the Structure of Enterprise in the

Development of the Eleventh Century Chinese Iron and Steel Industry". Journal of Economic History 26: 53–54.

41. ^ Jump up to:a b Tylecote, R. F. A history of metallurgy 2 edn, Institute of Materials, London 1992, pp. 95–99 and 102–105.

42. Jump up^ Raistrick, A. A Dynasty of Ironfounders (1953; York 1989)43. Jump up^ Hyde, C. K. Technological Change and the British iron industry (Princeton 1977)44. Jump up^ Trinder, B. The Industrial Revolution in Shropshire (Chichester 2000)45. Jump up^ Barraclough, K. C. Steel before Bessemer: I Blister Steel: the birth of an industry (The

Metals Society, London, 1984), pp. 48–52.46. Jump up^ King, P. W. (2003). "The Cartel in Oregrounds Iron: trading in the raw material for steel

during the eighteenth century". Journal of Industrial History 6  (1): 25–49.47. ^ Jump up to:a b c d "Iron and steel industry". Britannica. Encyclopædia Britannica. 2007.48. Jump up^ K. C. Barraclough, Steel before Bessemer: II Crucible Steel: the growth of technology (The

Metals Society, London, 1984).49. Jump up^ Swank, James Moore (1892). History of the Manufacture of Iron in All Ages. ISBN 0-8337-

3463-6.50. Jump up^ Bessemer process 2. Encyclopædia Britannica. 2005. p. 168.51. Jump up^ Basic oxygen process. Encyclopædia Britannica. 2007.52. Jump up^ Jones, J.A.T. ; Bowman, B. and Lefrank, P.A. Electric Furnace Steelmaking, in The

Making, Shaping and Treating of Steel, pp. 525–660. R.J. Fruehan, Editor. 1998, The AISE Steel Foundation: Pittsburgh.

53. Jump up^ "Steel Industry". Retrieved 2009-07-12.54. Jump up^ "Congressional Record V. 148, Pt. 4, April 11, 2002 to April 24, 2002". United States

Government Printing Office.55. Jump up^ "India's steel industry steps onto world stage". Retrieved 2009-07-12.56. Jump up^ "Long-term planning needed to meet steel demand". The News. 2008-03-01. Archived

from the original on 2010-11-02. Retrieved 2010-11-02.57. Jump up^ Uchitelle, Louis (2009-01-01). "Steel Industry, in Slump, Looks to Federal Stimulus". The

New York Times. Retrieved 2009-07-19.58. Jump up^ Hartman, Roy A. (2009). Recycling. Encarta. Archived from the original on 2008-04-14.59. Jump up^ Fenton, Michael D (2008). "Iron and Steel Scrap". In United States Geological

Survey. Minerals Yearbook 2008, Volume 1: Metals and Minerals. Government Printing Office.  ISBN 1411330153.

60. Jump up^ "High strength low alloy steels". Schoolscience.co.uk. Retrieved 2007-08-14.61. Jump up^ "Dual-phase steel". Intota Expert Knowledge Services. Retrieved 2007-03-01.62. Jump up^ Werner, Ewald. "Transformation Induced Plasticity in low alloyed TRIP-steels and

microstructure response to a complex stress history". Archived from the original on December 23, 2007. Retrieved 2007-03-01.

63. Jump up^ Mirko, Centi; Saliceti Stefano. "Transformation Induced Plasticity (TRIP), Twinning Induced Plasticity (TWIP) and Dual-Phase (DP) Steels". Tampere University of Technology. Archived from the original on 2008-03-07. Retrieved2007-03-01.

64. Jump up^ Galvanic protection. Encyclopædia Britannica. 2007.65. Jump up^ "Steel Glossary". American Iron and Steel Institute (AISI). Retrieved 2006-07-30.

66. Jump up^ "Steel Interchange". American Institute of Steel Construction Inc. (AISC). Archived from the original on 2007-12-22. Retrieved 2007-02-28.

67. Jump up^ "Properties of Maraging Steels". Retrieved 2009-07-19.68. Jump up^ Hadfield manganese steel. Answers.com. McGraw-Hill Dictionary of Scientific and

Technical Terms, McGraw-Hill Companies, Inc., 2003. Retrieved on 2007-02-28.69. Jump up^ Herkewitz, William (2015-02-04).  "Scientists Invent a New Steel as Strong as Titanium   ;

South Korean researchers have solved a longstanding problem that stopped them from creating ultra-strong, lightweight aluminum-steel alloys".Popular Mechanics.

70. Jump up^ "Wings of steel: An alloy of iron and aluminium is as good as titanium, at a tenth of the cost". The Economist. February 7, 2015. Retrieved February 5, 2015. E02715

71. Jump up^ Sang-Heon Kim, Hansoo Kim & Nack J. Kim (February 5, 2015). "Brittle intermetallic compound makes ultrastrong low-density steel with large ductility". Nature (Nature Publishing Group) 518: 77–79. doi:10.1038/nature14144. Retrieved February 5, 2015. we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion.

72. Jump up^ Bringas, John E. (2004). Handbook of Comparative World Steel Standards: Third Edition  (PDF) (3rd. ed.). ASTM International. p. 14.  ISBN 0-8031-3362-6. Archived from the original  (PDF) on 2007-01-27.

73. Jump up^ Steel Construction Manual, 8th Edition, second revised edition, American Institute of Steel Construction, 1986, ch. 1 page 1-5

74. Jump up^ Ochshorn, Jonathan (2002-06-11).  "Steel in 20th Century Architecture". Encyclopedia of Twentieth Century Architecture. Retrieved 2010-04-26.

75. Jump up^ Materials science. Encyclopædia Britannica. 2007.