Iron is a chemical element with symbol Fe 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, forming much of Earth’s outer and inner core. It is the fourth most common element in the Earth’s crust. Pure iron is very rare on the Earth’s crust, basically being limited to meteorites. Iron ores are quite abundant, but extracting usable metal from them requires kilns or furnaces capable of reaching 1500 °C or higher, about 500 °C higher than what is enough to smelt copper. Iron alloys, such as steel, inox, and special steels are now by far the most common industrial metals, because of their mechanical properties and their low cost. Steel is an alloy of iron and carbon, and sometimes other elements. Because of its high tensile strength and low cost, it is a major component used in buildings, infrastructure, tools, ships, automobiles, machines, appliances. Iron is the base metal of steel. Iron is able to take on two crystalline forms (allotropic forms), body centered cubic and face centered cubic, depending on its temperature. In the body-centered cubic arrangement, there is an iron atom in the center and eight atoms at the vertices of each cubic unit cell; in the face-centered cubic, there is one atom at the center of each of the six faces of the cubic unit cell and eight atoms at its vertices. It is the interaction of the allotropes of iron with the alloying elements, primarily carbon, that gives steel and cast iron their range of unique properties. In pure iron, the crystal structure has relatively little resistance to the iron atoms slipping past one another, and so pure iron is quite ductile, or soft and easily formed. In steel, small amounts of carbon, other elements, and inclusions within the iron act as hardening agents that prevent the movement of dislocations that are common in the crystal lattices of iron atoms. The carbon in typical steel alloys may contribute up to 2.14% of its weight. Varying the amount of carbon and many other alloying elements, as well as controlling their chemical and physical makeup in the final steel (either as solute elements, or as precipitated phases), slows the movement of those dislocations that make pure iron ductile, and thus controls and enhances its qualities. These qualities include such things as the hardness, quenching behavior, need for annealing, tempering behavior, yield strength, and tensile strength of the resulting steel. The increase in steel’s strength compared to pure iron is possible only by reducing iron’s ductility. Today, steel is one of the most common manmade materials in the world, with more than 1.6 billion tons produced annually. Modern steel is generally identified by various grades defined by assorted standards organizations. |
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DIFFERENT TYPES OF STEEL – steel is used very extensively in almost every industry and its products reach every household in one form or another. Steel is manufactured in various compositions and these alloys have different properties. The property of the steel is derived from the characteristics of the element alloyed with the steel. The cost of the steel depends upon its composition and use.Steel is an alloy made from iron and carbon. There are several distinct grades of steel that have unique chemical compositions based on the different amounts of carbon and added alloys. Although steel consists mostly of iron and carbon, the World Steel Association reports that more than 3,500 grades of steel are in existence, each featuring unique chemical, physical and environmental properties. The amount of carbon, additional alloying elements, and level of impurities contained determine the properties of each grade. Even though the most commonly used grades of steel contain between 0.1 and 0.25 percent carbon, some can have a carbon content of up to 1.5 percent. All grades of steel contain elements like manganese, phosphorus, and sulfur. While the last two are known to have deleterious effects on the strength and durability of steel, manganese has significant benefits. Steel is produced in various forms, each featuring unique properties that may have been manipulated to fit specific applications. These properties are the basis of every grading system used to distinguish one form of steel from the other. According to AISI, steels can be grouped into the following categories depending on their chemical compositions or metal alloy contents:
Pros Depending on the variant, carbon steels are:
Cons
Alloy Steels – The name comes from the fact that steels in this group contain a small percentage of other metals besides iron. Alloy steels contain common alloy metals in varying proportions, which makes this type of steel suitable for specific applications. These alloy metals include aluminum, manganese, nickel, titanium, silicon, copper, and chromium, the addition of which produces properties that are different from those found in regular carbon steels. When added, alloying elements can change properties like strength, ductility, formability, hardenability, and ability to resist corrosion. For instance, stainless steel is produced by adding chromium and nickel whereas the addition of aluminum results in a more uniform appearance. On the other hand, the addition of manganese is known to make steel extremely hard and strong. Alloy steels can have diverse mechanical properties due to the broad range of compositions possible. Pros Depending on the variant, alloy steels are:
Cons
Because of the properties mentioned above, alloys steels serve a broad range of applications including the manufacture of pipelines, transformers, auto parts, electric motors and power generators. Tool Steels – This type of steel is alloyed at very high temperatures and often contains hard metals like tungsten, cobalt, molybdenum and vanadium. Since they are not only heat resistant but also durable, tool steels are often used for cutting and drilling equipment. Even so, there are various types of tools steels, each containing varying quantities of different alloy metals. As a result, each type of tool steel offers a different level of heat resistance and durability. Pros
Cons
Stainless Steels – Although stainless steels comprise of several metal alloys, they usually contain 10-20 percent chromium, making it the primary alloying element. Compared to the other forms of steel, stainless steels are approximately 200 times more resistant to rusting, especially the types that contain at least 11 percent chromium. As a result, stainless steel is highly valued for its ability to resist corrosion. Based on their crystalline structure, stainless steels fall into one of the following categories:
Pros Stainless steels are generally:
Cons
As evidenced by the properties offered by each of the forms, steel has qualities that can meet a broad range of applications. In fact, steel serves an array of construction, appliance, energy transport, and packaging purposes in today’s world. |
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Properties of Steel Types
Boron Steel – Boron steel has high hardenability (the capability of a metal alloy to be hardened by heat treatment) and strength. Boron, when added to fully oxidized steel, especially low carbon steel, gives the steel these properties without the loss of ductility (ability of a material to be elongated in tension), formability (capability of a material to be shaped) and machinability (the ease with which a metal can be machined to an acceptable surface finish). Boron is usually added in range of 0.003-0.005 percent in this steel. Chromium Stainless Steel – Chromium steel has high hardenability and high resistance to corrosion and oxidation. This steel can withstand high temperature and has high abrasion resistance. Chromium steel can be brittle and contains chromium in the range of 0.15 percent and above. Chromium-Molybdenum Steels – Chromium and molybdenum both individually add to the hardenability of alloy steel. This steel is highly resistant to corrosion and oxidation. It can withstand high temperature and is abrasion resistant. Molybdenum in the steel maintains hardenability in the required range and increases high temperature working strength. The amount of chromium in this steel is kept between 0.40 and 1.10 percent and molybdenum is in between 0.08 and 0.25 percent. Nickel-Chromium Steel – Nickel-chromium steel has high hardenability. This steel is resistant to corrosion because of chromium and has high abrasion resistance to oxidation and abrasion. It has high temperature strength and offers much greater toughness at a specified carbon level. The amount of nickel in nickel-chromium steel is in between 3.25 and 3.75 percent and that of chromium is 1.25 to 1.75 percent. Chromium-Vanadium Steel – Chromium-vanadium steel has high toughness. It is resistant to corrosion and oxidation, has high temperature strength and abrasive resistance. Both chromium and vanadium increase the hardenability and vanadium inhibits grain growth during heat treating. The alloying range of chromium in chromium-vanadium steel is 0.80 to 1.10 percent and the amount of vanadium is 0.15 percent and above. High Strength Steel – High strength steel is specifically manufactured steel that has high strength and can be worked upon at very high temperatures. This steel is suited for specific applications where strength is the primary requirement. The general composition of high temperature strength is usually; carbon (0.27 to 0.38 percent), manganese (0.60 to 0.90 percent), silicon (0.40 to 0.60 percent), chromium (1.0 to 0.90 percent), nickel (1.85 to 2.0 percent), molybdenum (0.35 to 0.40 percent) and vanadium (0.05 to 0.23 percen)t. High Temperature Steels – High temperature steel is designed for applications in boiler tubes, pressure vessels and steam turbines where high temperature operation is required. These steels are highly resistant to mechanical and chemical degradation at elevated temperatures. The usual composition of high temperature steel includes carbon (0.28 to 0.50 percent), manganese (0.45 to .90 percent), silicon (0.15 to 0.75 percent), chromium (0.80 to 1.50 percent), nickel (0.25 to 0.50 percent), molybdenum (0.40 to 0.65 percent) and vanadium (0.20 to 0.95 percent) |
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Construction and building – H-shapes continue to advance as a steel material for large scale construction. Structural steel products must continue to progress with seismic resistance capabilities and design qualities to satisfy higher and larger scale construction needs. a pioneer in H-shapes, contributes to optimize design and fabrication works, shorten work periods and enhance cost savings with rich size variations, improved strength and weldability and high dimensional accuracy.
Ports and rivers – Steel sheet piles in an extensive range of sizes and qualities contribute to safe, secure, and comfortable living. In the ports field, steel materials such as steel pipe piles and sheet piles have been widely used up to the present time. Steel is outstanding as a structural material due to its high strength and uniform quality, and a steel product suiting the design conditions can be selected from an extensive variety of shapes and dimensions. Also, by using steel it is possible to shorten work periods, and thus it has contributed to the development of port facilities, e.g., through frequent use in quay walls, piled piers, and other piers. Furthermore, methods to prevent corrosion have recently been developed and applied using titanium and stainless steel. Going forward, we will respond to needs such as earthquake resistance, measures to boost tsunami resistance, and measures to counter deterioration. In the rivers field, steel products such as sheet piles are widely used to build shore protection with outstanding resistance to scouring and earthquakes. During the dry season, it is possible to work at high speed in limited space, and these products can also support work with low noise and low vibration in consideration of the surrounding environment. Therefore, these products have contributed to the development and preservation of river environments, primarily urban rivers. They also meet a wide range of other needs, such as measures to prevent river embankment seepage, earthquake resistance reinforcement in preparation for a major earthquake, and emergency recovery work in case of damage. Roads and tunnels – Segment products with high work efficiency, outstanding for earthquake resistance and water stopping performance. For infrastructure such as roads and railways, the walls of shielded tunnels passing through the ground are composed of products called segments. Our segments have high water stopping performance, high load bearing performance, and deformation performance during earthquakes thanks to our unique main body structure and connection method. These products allow workers to work more efficiently and safely, and have been proven, and earned a high reputation, in many large-scale projects. Bridges – Products for bridges with outstanding cost performance and weather resistance In our group, we handle a wide range of products, such as high-performance steel material with high yield point, high toughness, and outstanding weldability and cold workability, high-speed assembly on-site using prefabricated steel members, and bridge products with outstanding cost performance. Furthermore, we help to reduce maintenance costs and lengthen bridge service life through weather resistant steel which exhibits a corrosion prevention function without paint, and corrosion resistant steel which can lengthen painting cycles. Also, various methods employing steel pipe piles and steel pipe sheet piles with high strength and deformation performance are used for bridge foundations, and we thereby meet a variety of needs such as high depth, soft ground, shorter work periods, hight bearing capacity, space saving, and protection of the environment. |
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