Mangalloy, also called manganese steel or Hadfield steel, is an alloy steel containing an average of around 13% manganese. Mangalloy is known for its high impact strength and resistance to abrasion once in its work-hardened state.
Mangalloy, also called manganese steel or Hadfield steel, is an alloy steel containing an average of around 13% manganese. Mangalloy is known for its high impact strength and resistance to abrasion once in its work-hardened state.
Mangalloy is made by alloying steel, containing 0.8 to 1.25% carbon, with 11 to 15% manganese. [1] Mangalloy is a unique non-magnetic steel with extreme anti-wear properties. The material is very resistant to abrasion and will achieve up to three times its surface hardness during conditions of impact, without any increase in brittleness which is usually associated with hardness. [2] This allows mangalloy to retain its toughness.
Most steels contain 0.15 to 0.8% manganese. High strength alloys often contain 1 to 1.8% manganese. [3] [4] [5] 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. At around 10% manganese content the steel will remain in its austenite form at room temperature if cooled correctly. [6] Both hardness and ductility reach their highest points around 12%, depending on other alloying agents. [1] 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 and chromium; added most often to austenitic steels as an austenite stabilizer; molybdenum and vanadium; used in non-austenitic steels as a ferrite stabilizer; or even non-metallic elements such as silicon. [4]
Mangalloy has fair yield strength but very high tensile strength, 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 −196 °F (−127 °C). [4] [7]
Mangalloy is heat treatable, but the manganese lowers the temperature at which austenite transforms into ferrite. Unlike carbon steel, 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 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). [8] 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. [9]
Many of mangalloy's uses are often limited by its difficulty in machining; sometimes described as having "zero machinability." [7] 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. [10] It can be cut with an oxy-acetylene torch, but plasma or laser cutting is the preferred method. [11] Despite its extreme hardness and tensile strength, the material may not always be rigid. [10] It can be formed by cold rolling or cold bending. [11]
Mangalloy was created by Robert Hadfield in 1882, becoming the first alloy steel to both become a commercial success and to exhibit behavior radically differing from carbon steel. Thus, it is generally considered to mark the birth of alloy steels. [12]
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 , which greatly reduced the presence of impurities in his steel. [12] In 1816, a German researcher Carl J. B. Karsten [13] noted that adding fairly large amounts of manganese to iron would increase its hardness without affecting its malleability and toughness, [14] but the mix was not homogeneous and the results of the experiment were not considered to be reliable. [15] "and no one understood that the real reason why the iron mined in Noricum 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." [16] In 1860, Sir Henry Bessemer, trying to perfect his Bessemer process of steel making, found that adding spiegeleisen to the steel after it was blown helped to remove excess sulfur and oxygen. [3] Sulfur combines with iron to form a sulfide that has a lower melting point than steel, causing weak spots, which prevented hot rolling. Manganese is usually added to most modern steels in small amounts because of its powerful ability to remove impurities. [17]
Hadfield was in search of a steel that could be used for the casting of tram 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. [18] [12]
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, 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 on a lathe. It was non-magnetic despite containing over 80% iron, and had very high electrical resistance. Attempts to grind it simply glazed and polished the surface. Most striking, when heated and quenched, it behaved almost opposite to plain carbon-steel. [12] 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...". [19]
Hadfield's invention was the first alloy of steel to demonstrate considerable differences in properties compared to carbon steel. [12] In the modern age, it is known that manganese inhibits the transformation of the malleable austenite phase into hard brittle martensite 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 alloy steel 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. [12]
Mangalloy has been used in the mining industry, cement mixers, 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 steels, due to their high strength at very low temperatures.
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, opacity, and luster, but may have properties that differ from those of the pure metals, such as increased strength or hardness. In some cases, an alloy may reduce the overall cost of the material while preserving important properties. In other cases, the mixture imparts synergistic properties to the constituent metal elements such as corrosion resistance or mechanical strength.
Steel is an alloy of iron and carbon with improved strength and fracture resistance compared to other forms of iron. Because of its high tensile strength and low cost, steel is one of the most commonly manufactured materials in the world. Steel is used in buildings, as concrete reinforcing rods, in bridges, infrastructure, tools, ships, trains, cars, bicycles, machines, electrical appliances, furniture, and weapons.
Cast iron is a class of iron–carbon alloys with a carbon content of more than 2% and silicon content around 1–3%. Its usefulness derives from its relatively low melting temperature. The alloying elements determine the form in which its carbon appears: white cast iron has its carbon combined into an iron carbide named cementite, which is very hard, but brittle, as it allows cracks to pass straight through; grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks, and ductile cast iron has spherical graphite "nodules" which stop the crack from further progressing.
Heat treating is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve the desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, carburizing, normalizing and quenching. Although the term heat treatment applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.
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 1000 K (727 °C); other alloys of steel have different eutectoid temperatures. The austenite allotrope is named after Sir William Chandler Roberts-Austen (1843–1902). It exists at room temperature in some stainless steels due to the presence of nickel stabilizing the austenite at lower temperatures.
High-strength low-alloy steel (HSLA) is a type of alloy steel that provides better mechanical properties or greater resistance to corrosion than carbon steel. HSLA steels vary from other steels in that they are not made to meet a specific chemical composition but rather specific mechanical properties. They have a carbon content between 0.05 and 0.25% to retain formability and weldability. Other alloying elements include up to 2.0% manganese and small quantities of copper, nickel, niobium, nitrogen, vanadium, chromium, molybdenum, titanium, calcium, rare-earth elements, or zirconium. Copper, titanium, vanadium, and niobium are added for strengthening purposes. These elements are intended to alter the microstructure of carbon steels, which is usually a ferrite-pearlite aggregate, to produce a very fine dispersion of alloy carbides in an almost pure ferrite matrix. This eliminates the toughness-reducing effect of a pearlitic volume fraction yet maintains and increases the material's strength by refining the grain size, which in the case of ferrite increases yield strength by 50% for every halving of the mean grain diameter. Precipitation strengthening plays a minor role, too. Their yield strengths can be anywhere between 250–590 megapascals (36,000–86,000 psi). Because of their higher strength and toughness HSLA steels usually require 25 to 30% more power to form, as compared to carbon steels.
Martensitic stainless steel is a type of stainless steel alloy that has a martensite crystal structure. It can be hardened and tempered through aging and heat treatment. The other main types of stainless steel are austenitic, ferritic, duplex, and precipitation hardened.
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:
Tool steel is any of various carbon steels and alloy steels that are particularly well-suited to be made into tools and tooling, including cutting tools, dies, hand tools, knives, and others. Their suitability comes from their distinctive hardness, resistance to abrasion and deformation, and their ability to hold a cutting edge at elevated temperatures. As a result, tool steels are suited for use in the shaping of other materials, as for example in cutting, machining, stamping, or forging.
Maraging steels are steels that are known for possessing superior strength and toughness without losing ductility. Aging refers to the extended heat-treatment process. These steels are a special class of very-low-carbon ultra-high-strength steels that derive their strength not from carbon, but from precipitation of intermetallic compounds. The principal alloying element is 15 to 25 wt% nickel. Secondary alloying elements, which include cobalt, molybdenum and titanium, are added to produce intermetallic precipitates. Original development was carried out on 20 and 25 wt% Ni steels to which small additions of aluminium, titanium, and niobium were made; a rise in the price of cobalt in the late 1970s led to the development of cobalt-free maraging steels.
Case-hardening or Carburization is the process of introducing carbon to the surface of a low carbon iron or much more commonly low carbon steel object in order to enable the surface to be hardened.
Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys. Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air. The exact temperature determines the amount of hardness removed, and depends on both the specific composition of the alloy and on the desired properties in the finished product. For instance, very hard tools are often tempered at low temperatures, while springs are tempered at much higher temperatures.
Cryogenic hardening is a cryogenic treatment process where the material is cooled to approximately −185 °C (−301 °F), usually using liquid nitrogen. It can have a profound effect on the mechanical properties of certain steels, provided their composition and prior heat treatment are such that they retain some austenite at room temperature. It is designed to increase the amount of martensite in the steel's crystal structure, increasing its strength and hardness, sometimes at the cost of toughness. Presently this treatment is being used on tool steels, high-carbon, high-chromium steels and in some cases to cemented carbide to obtain excellent wear resistance. Recent research shows that there is precipitation of fine carbides in the matrix during this treatment which imparts very high wear resistance to the steels.
In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature, maintaining a suitable temperature for an appropriate amount of time and then cooling.
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.
Austempering is heat treatment that is applied to ferrous metals, most notably steel and ductile iron. In steel it produces a bainite microstructure whereas in cast irons it produces a structure of acicular ferrite and high carbon, stabilized austenite known as ausferrite. It is primarily used to improve mechanical properties or reduce / eliminate distortion. Austempering is defined by both the process and the resultant microstructure. Typical austempering process parameters applied to an unsuitable material will not result in the formation of bainite or ausferrite and thus the final product will not be called austempered. Both microstructures may also be produced via other methods. For example, they may be produced as-cast or air cooled with the proper alloy content. These materials are also not referred to as austempered.
TRIP steel are a class of high-strength steel alloys typically used in naval and marine applications and in the automotive industry. TRIP stands for "Transformation induced plasticity," which implies a phase transformation in the material, typically when a stress is applied. These alloys are known to possess an outstanding combination of strength and ductility.
Twinning-Induced Plasticity steel which is also known as TWIP steel is a class of austenitic steels which can deform by both glide of individual dislocations and mechanical twinning on the {1 1 1}γ<1 1 >γ system. They have outstanding mechanical properties at room temperature combining high strength and ductility based on a high work-hardening capacity. TWIP steels have mostly high content in Mn and small additions of elements such C, Si, or Al. The steels have low stacking fault energy at room temperature. Although the details of the mechanisms controlling strain-hardening in TWIP steels are still unclear, the high strain-hardening is commonly attributed to the reduction of the dislocation mean free path with the increasing fraction of deformation twins as these are considered to be strong obstacles to dislocation glide. Therefore, a quantitative study of deformation twinning in TWIP steels is critical to understand their strain-hardening mechanisms and mechanical properties. Deformation twinning can be considered as a nucleation and growth process. Twin growth is assumed to proceed by co-operative movement of Shockley partials on subsequent {111} planes.
USAF-96 is a high-strength, high-performance, low-alloy, low-cost steel, developed for new generation of bunker buster type bombs, e.g. the Massive Ordnance Penetrator and the improved version of the GBU-28 bomb known as EGBU-28. It was developed by the US Air Force at the Eglin Air Force Munitions Directorate. It uses only materials domestic to the USA. In particular it requires no tungsten.