Mangalloy, also called manganese steel or Hadfield steel, is an

alloy steel Alloy steel is steel that is alloyed with a variety of elements in total amounts between 1.0% and 50% by weight to improve its mechanical properties. Alloy steels are broken down into two groups: low alloy steels and high alloy steels. The differe ...

containing an average of around 13%

manganese Manganese is a chemical element with the Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of ...

. Mangalloy is known for its high impact strength and resistance to abrasion once in its work-hardened state.

Material properties

Mangalloy is made by

alloying An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...

steel, containing 0.8 to 1.25% carbon, with 11 to 15%

. Mangalloy is a unique non-magnetic

steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistan ...

with extreme anti-wear properties. The material is very resistant to abrasion and will achieve up to three times its surface

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...

during conditions of

impact Impact may refer to: * Impact (mechanics), a high force or shock (mechanics) over a short time period * Impact, Texas, a town in Taylor County, Texas, US Science and technology * Impact crater, a meteor crater caused by an impact event * Imp ...

, without any increase in

brittleness A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. B ...

which is usually associated with hardness. This allows mangalloy to retain its

toughness In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing. At about 1.5% manganese content, the steel becomes brittle, and this trait increases until about 4 to 5% manganese content is reached. At this point, the steel will pulverize at the strike of a hammer. Further increase in the manganese content will increase both hardness and

ductility Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile str ...

. At around 10% manganese content the steel will remain in its

austenite Austenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotrope of iron or a solid solution of iron with an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of 100 ...

form at room temperature if cooled correctly. Both hardness and ductility reach their highest points around 12%, depending on other alloying agents. The primary of these alloying agents is carbon, because the addition of manganese to low-carbon steel has little effect, but increases dramatically with increasing carbon content. The original Hadfield steel contained about 1.0% carbon. Other alloying agents may include metals like

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow t ...

and

chromium Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hard ...

; added most often to austenitic steels as an austenite stabilizer;

molybdenum Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lead ...

and

vanadium Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pass ...

; used in non-austenitic steels as a ferrite stabilizer; or even non-metallic elements such as

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...

. Mangalloy has fair

yield strength In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and wi ...

but very high

tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials ...

, typically anywhere between 350 and 900 megapascals (MPa), which rises rapidly as it work hardens. Unlike other forms of steel, when stretched to the breaking point, the material does not "neck down" (get smaller at the weakest point) and then tear apart. Instead, the metal necks and work hardens, increasing the tensile strength to very high levels, sometimes as high as 2000 MPa. This causes the adjacent material to neck down, harden, and this continues until the entire piece is much longer and thinner. The typical elongation can be anywhere from 18 to 65%, depending on both the exact composition of the alloy and prior heat-treatments. Alloys with manganese contents ranging from 12 to 30% are able to resist the brittle effects of cold, sometimes to temperatures in the range of . Mangalloy is heat treatable, but the manganese lowers the temperature at which austenite transforms into ferrite. Unlike

carbon steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, coba ...

, mangalloy softens rather than hardens when rapidly cooled, restoring the ductility from a work-hardened state. Most grades are ready for use after annealing and then

quenching In materials science, quenching is the rapid cooling of a workpiece in water, oil, polymer, air, or other fluids to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, such as ...

from a yellow heat, with no further need of tempering, and usually have a normal Brinell hardness of around 200 HB, (roughly the same as 304 stainless steel), but, due to its unique properties, the indentation hardness has very little effect on determining the scratch hardness (the abrasion and impact resistance of the metal). Another source says that the basic Brinell hardness of manganese steel according to the original Hadfield specification is 220 but that with impact wear the surface hardness will increase to over 550.Titus Manganese Steel (Manganal)
Titussteel Many of mangalloy's uses are often limited by its difficulty in

machining Machining is a process in which a material (often metal) is cut to a desired final shape and size by a controlled material-removal process. The processes that have this common theme are collectively called subtractive manufacturing, which utilizes ...

; sometimes described as having "zero machinability." The metal cannot be softened by annealing and hardens rapidly under cutting and grinding tools, usually requiring special tooling to machine. The material can be drilled with extreme difficulty using diamond or carbide. Although it can be forged from a yellow heat, it may crumble if hammered when white-hot, and is much tougher than carbon steel when heated. It can be cut with an oxy-acetylene torch, but plasma or

laser cutting Laser cutting is a technology that uses a laser to vaporize materials, resulting in a cut edge. While typically used for industrial manufacturing applications, it is now used by schools, small businesses, architecture, and hobbyists. Laser cut ...

is the preferred method. Despite its extreme hardness and tensile strength, the material may not always be rigid. It can be formed by cold rolling or cold bending.

History

Mangalloy was created by Robert Hadfield in 1882, becoming the first

to both become a commercial success and to exhibit behavior radically differing from

. Thus, it is generally considered to mark the birth of alloy steels. Benjamin Huntsman was one of the first to begin adding other metals to steel. His process of making crucible steel, invented in 1740, was the first time steel was able to be fully melted in a crucible. Huntsman had already been using various fluxes to help remove impurities from steel, and soon began adding a manganese-rich pig-iron called ''

Spiegeleisen Spiegeleisen (literally "mirror-iron", — mirror or specular; — iron) is a ferromanganese alloy containing approximately 15% manganese and small quantities of carbon and silicon. Spiegeleisen is sometimes also referred to as ''specular pig ...

'', which greatly reduced the presence of impurities in his steel. In 1816, a German researcher Carl J. B. Karsten noted that adding fairly large amounts of manganese to

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...

would increase its hardness without affecting its

malleability Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...

and toughness, but the mix was not homogeneous and the results of the experiment were not considered to be reliable. "and no one understood that the real reason why the iron mined in

Noricum Noricum () is the Latin name for the Celtic kingdom or federation of tribes that included most of modern Austria and part of Slovenia. In the first century AD, it became a province of the Roman Empire. Its borders were the Danube to the nor ...

produced such superb steel lay in the fact that it contained a small amount of manganese uncontaminated by phosphorus, arsenic, or sulphur, and so was the raw material of manganese steel." In 1860, Sir Henry Bessemer, trying to perfect his

Bessemer process The Bessemer process was the first inexpensive industrial process for the mass production of steel from molten pig iron before the development of the open hearth furnace. The key principle is removal of impurities from the iron by oxidation ...

of steel making, found that adding ''spiegeleisen'' to the steel after it was blown helped to remove excess

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...

and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

. Sulfur combines with iron to form a

sulfide Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds la ...

that has a lower

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depen ...

than steel, causing weak spots, which prevented

hot rolling In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simi ...

. Manganese is usually added to most modern steels in small amounts because of its powerful ability to remove impurities. Hadfield was in search of a steel that could be used for the

casting Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a ''casting'', which is ejecte ...

tram A tram (called a streetcar or trolley in North America) is a rail vehicle that travels on tramway tracks on public urban streets; some include segments on segregated right-of-way. The tramlines or networks operated as public transport ...

wheels which would exhibit both hardness and toughness, since ordinary carbon steels do not combine those properties. Steel can be hardened by rapid cooling, but loses its toughness, becoming brittle. Steel castings can not usually be cooled rapidly, for irregular shapes can warp or crack. Mangalloy proved to be extremely suitable for casting, as it did not form gas pockets called "blow-holes", and did not display the extreme brittleness of other castings. Hadfield had been studying the results of others who experimented with mixing various elements with steel, such as Benjamin Huntsman and A.H. Allen. At the time the manufacture of steel was an art rather than a science, produced by skilled craftsmen who were often very secretive. Thus, no metallurgical data about steel existed before 1860, so information about the various alloys was sporadic and often unreliable. Hadfield became interested in the addition of manganese and silicon. The Terre Noire Company had created an alloy called "ferro-manganese", containing up to 80% manganese. Hadfield began by mixing ferro-manganese with crucible steel and silicon, producing an alloy of 7.45% manganese, but the material was unsatisfactory for his purposes. In his next attempt, he left out the silicon and added more ferro-manganese to the mix, achieving an alloy with 1.35% carbon and 13.76% manganese. Upon creating mangalloy, Hadfield tested the material, thinking that the results must have been erroneous. It looked dull and soft, with a submetallic luster similar in appearance to

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...

, yet sheared the teeth off his file. It would not hold an edge as a cutting tool, yet could not be cut with saws nor

machined Machining is a process in which a material (often metal) is cut to a desired final shape and size by a controlled material-removal process. The processes that have this common theme are collectively called subtractive manufacturing, which utilizes ...

on a

lathe A lathe () is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, and turning, with tools that are applied to the workpiece ...

. It was non-magnetic despite containing over 80% iron, and had very high

electrical resistance The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallel ...

. Attempts to grind it simply glazed and polished the surface. Most striking, when heated and quenched, it behaved almost opposite to plain carbon-steel. After performing several hundred tests, he realized that they must be accurate, although the reason for the combination of hardness and toughness defied any explanation at the time. Hadfield wrote, "Is there any case similar to this among other alloys of iron, if the term alloy may be used? No metallurgical treatise refers to them... Possibly when the nature of the laws governing alloys is better understood, this will be found to be only one of other cases...". Hadfield's invention was the first alloy of steel to demonstrate considerable differences in properties compared to carbon steel. In the modern age, it is known that manganese inhibits the transformation of the malleable austenite phase into hard brittle

martensite Martensite is a very hard form of steel crystalline structure. It is named after German metallurgist Adolf Martens. By analogy the term can also refer to any crystal structure that is formed by diffusionless transformation. Properties M ...

that takes place for normal steels when they are quenched in the hardening procedure. The austenite of Hadfield steels is thermodynamically unstable and will transform into martensite when subject to mechanical impact thus forming the hard surface layer. Hadfield patented his steel in 1883, but spent the next five years perfecting the mixture, so did not present it to the public until 1887. He finally settled on an alloy containing 12 to 14% manganese and 1.0% carbon, which was ductile enough to be indented but so hard it could not be cut. It became the first

to become commercially viable. Hadfield originally marketed his steel for use in railways and trams, but quickly began producing it for everything from saw plates to safes.

Use

Mangalloy has been used in the

mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the econom ...

industry,

cement mixer A concrete mixer (often colloquially called a cement mixer) is a device that homogeneously combines cement, aggregate such as sand or gravel, and water to form concrete. A typical concrete mixer uses a revolving drum to mix the components. For ...

s, rock crushers, railway switches and crossings, crawler treads for tractors and other high impact and abrasive environments. It is also used in high impact environments like inside a shot peening machine. These alloys are finding new uses as

cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...

steels, due to their high strength at very low temperatures.

References

{{Reflist, refs= {{Cite book , title=Manganese-steel , first1=Robert Abbott , last1=Hadfield , authorlink=Sir Robert Hadfield , first2=James , last2=Forrest , publisher=Institution , year=1888 , page=5 Steel alloys Manganese compounds

Material properties

History

Use

See also

References