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37-563: [REDACTED] Look up sinter in Wiktionary, the free dictionary. Sinter may refer to: Sinter plant , in which iron-ore dust gets mixed with other fine materials at high temperature, to create a product – sinter – for use in a blast furnace Sintering , a high temperature process for fusing powder together Calcareous sinter , calcium carbonate deposited by springs Siliceous sinter , silica deposited by hot springs and geysers Sinter,

74-457: A blast furnace . In the early 20th century, sinter technology was developed for converting ore fines into lumpy material chargeable in blast furnaces. Sinter technology took 30 years to gain acceptance in the iron-making domain, but now plays an important role. Initially developed to generate steel, it is now a means of using metallurgical waste generated in steel plants to enhance blast furnace operation and reducing waste. The largest sinter plant

111-404: A change in ductility and hardness. As the material cools it recrystallizes. For many alloys, including carbon steel, the crystal grain size and phase composition, which ultimately determine the material properties, are dependent on the heating rate and cooling rate. Hot working or cold working after the annealing process alters the metal structure, so further heat treatments may be used to achieve

148-407: A charge, enters the ignition furnace into rows of multi-slit burners. In the case of one plant, the first (ignition) zone has eleven burners. The next (soaking/ annealing ) zone typically offers 12 burners. Air is sucked from the bottom of the bed of mixed material throughout the sintering machine. Fire penetrates the mixed material gradually, until it reaches the hearth layer. This end point of burning

185-422: A lower yield strength and a lower tensile strength . This process is also called LP annealing for lamellar pearlite in the steel industry as opposed to a process anneal , which does not specify a microstructure and only has the goal of softening the material. Often the material to be machined is annealed, and then subject to further heat treatment to achieve the final desired properties. Short cycle annealing

222-489: A racecar constructed by Fluid Motorsport Development Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Sinter . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Sinter&oldid=1130918587 " Category : Disambiguation pages Hidden categories: Short description

259-441: 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. In annealing, atoms migrate in the crystal lattice and the number of dislocations decreases, leading to

296-520: Is a binding material used to agglomerate materials, which saves the heating material, coke, and improves furnace productivity. Improvements and efficiency can be gained from higher softening temperature and narrower softening in the melting zone, which increases the volume of the granular zone and shrinks the width of the cohesive zone. A lower silica content and higher hot metal temperature contributes to more sulphur removal. Annealing (metallurgy) In metallurgy and materials science , annealing

333-400: Is a heat treatment cycle that restores some of the ductility to a product being cold-worked so it can be cold-worked further without breaking. The temperature range for process annealing ranges from 260 °C (500 °F) to 760 °C (1400 °F), depending on the alloy in question. This process is mainly suited for low-carbon steel. The material is heated up to a temperature just below

370-565: Is also done in forming gas , a mixture of hydrogen and nitrogen. The magnetic properties of mu-metal (Espey cores) are introduced by annealing the alloy in a hydrogen atmosphere. Typically, large ovens are used for the annealing process. The inside of the oven is large enough to place the workpiece in a position to receive maximum exposure to the circulating heated air. For high volume process annealing, gas fired conveyor furnaces are often used. For large workpieces or high quantity parts, car-bottom furnaces are used so workers can easily move

407-583: Is called burn through point (BTP). The hearth layer, which is nothing but sinter in smaller size, restricts sticking of hot sinter with pallets. BTP is achieved in a certain zone of sinter machine, to optimize the process, by means of several temperature measuring instrument placed throughout the sinter machine. After completion of burning, the mix converts into sinter, which then breaks into smaller size by sinter breaker. After breaking into small sizes, it cools down in cooler (linear or circular) by means of forced air. At discharge of sinter cooler, temperature of sinter

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444-721: Is different from Wikidata All article disambiguation pages All disambiguation pages Sinter plant Sinter plants, in combination with blast furnaces, are also used in non-ferrous smelting . About 70% of the world's primary lead production is still produced this way. The combination was once used in copper smelting, as at the Electrolytic Refining and Smelting smelter in Wollongong , New South Wales . Many countries, including India , France and Germany , have underground deposits of iron ore in dust form (blue dust). Such iron ore cannot be directly charged in

481-496: Is located in Chennai, India, and employs 10,000 people. Main feed into a sinter plant is base mix, which consists of iron ore fines, coke fines and flux (limestone) fines. In addition to base mix, coke fines, flux fines, sinter fines, iron dust (collected from plant de-dusting system and electrostatic precipitator ) and plant waste are mixed in proportion (by weight) in a rotary drum, often called mixing and nodulizing drum. Calcined lime

518-620: Is maintained as low, so that the hot sinter can be transported by a conveyor belt made of rubber. Necessary precautions are taken to trace any existence of fire in the belt and necessary extinguishing is done by spraying water. Then this product is being passed through a jaw-crusher, where the size of sinter is further reduced (~ 50 mm) into smaller size. Then the complete mixture is being passed through two screens. Smallest sinter fines (< 5 mm) are stored in proportioning bins and reused for preparing sinter again through mixing and nodulizing drum and fed to sinter machine for burning. A part of

555-436: Is termed stress relief . The relief of internal stresses is a thermodynamically spontaneous process ; however, at room temperatures, it is a very slow process. The high temperatures at which annealing occurs serve to accelerate this process. The reaction that facilitates returning the cold-worked metal to its stress-free state has many reaction pathways, mostly involving the elimination of lattice vacancy gradients within

592-419: Is to originate a uniform and stable microstructure that most closely resembles the metal's phase diagram equilibrium microstructure, thus letting the metal attain relatively low levels of hardness, yield strength and ultimate strength with high plasticity and toughness. To perform a full anneal on a steel for example, steel is heated to slightly above the austenitic temperature and held for sufficient time to allow

629-408: Is used as a medium for quenching usually in the form of brine (salt water). Brine provides faster cooling rates than water. This is because when an object is quenched in water steam bubbles form on the surface of the object reducing the surface area the water is in contact with. The salt in the brine reduces the formation of steam bubbles on the object's surface, meaning there is a larger surface area of

666-431: Is used as binder of the mixed material along with water (all in particular proportion by weight) to form feed-sinter of about 5 to 7 mm in size. This sinter globules are fed to sintering machine and burnt therein to produce blast furnace feed sinter. Material is put on a sinter machine in two layers. The bottom layer may vary in thickness from 30 to 75 millimetres (1.2 to 3.0 in). A 12 to 20 mm sinter fraction

703-468: Is used for turning normal ferrite into malleable ferrite. It consists of heating, cooling and then heating again from 4 to 8 hours. Resistive heating can be used to efficiently anneal copper wire ; the heating system employs a controlled electrical short circuit . It can be advantageous because it does not require a temperature -regulated furnace like other methods of annealing. The process consists of two conductive pulleys ( step pulleys ), which

740-400: Is used, also referred to as the hearth layer. The second, covering layer consists of mixed materials, making for a total bed height of 350 to 660 millimetres (14 to 26 in). The mixed materials are applied with drum feeders and roll feeders, which distributes the nodules in certain depth throughout the sintering machine. The upper layer is smoothed using a leveler. The material, also known as

777-425: The austenite transform into bainite or martensite , but rather have it completely transform to pearlite and ferrite or cementite . This means that steels that are very hardenable (i.e. tend to form martensite under moderately low cooling rates) have to be furnace cooled. The details of the process depend on the type of metal and the precise alloy involved. In any case the result is a more ductile material but

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814-409: The appearance of new strain-free grains. The grain size and shape do not change. The second stage is recrystallization , where new strain-free grains nucleate and grow to replace those deformed by internal stresses. If annealing is allowed to continue once recrystallization has completed, then grain growth (the third stage) occurs. In grain growth, the microstructure starts to coarsen and may cause

851-456: The body of the metal. The creation of lattice vacancies is governed by the Arrhenius equation , and the migration/diffusion of lattice vacancies are governed by Fick's laws of diffusion. In steel, there is a decarburization mechanism that can be described as three distinct events: the reaction at the steel surface, the interstitial diffusion of carbon atoms and the dissolution of carbides within

888-519: The conveyor carrying the sinter for the blast furnace and, along with blast furnace grade sinter, either goes to sinter storage bunkers or to blast furnace bunkers. Blast furnace-grade sinter consists of particles sized 5 to 12 mm as well as 20 mm and above. There are certain advantages of using sinters as opposed to using other materials which include recycling the fines and other waste products, to include flue dust, mill scale, lime dust and sludge. Processing sinter helps eliminate raw flux, which

925-452: The crystal lattice, which allows these dopant atoms to function properly as dopants in the semiconducting material. Normalization is an annealing process applied to ferrous alloys to give the material a uniform fine-grained structure and to avoid excess softening in steel. It involves heating the steel to 20–50 °C above its upper critical point, soaking it for a short period at that temperature and then allowing it to cool in air. Heating

962-404: The effect of redistributing and eradicating the dislocations in metals and (to a lesser extent) in ceramics. This alteration to existing dislocations allows a metal object to deform more easily, increasing its ductility. The amount of process-initiating Gibbs free energy in a deformed metal is also reduced by the annealing process. In practice and industry, this reduction of Gibbs free energy

999-446: The lower critical temperature of steel. Cold-worked steel normally tends to possess increased hardness and decreased ductility, making it difficult to work. Process annealing tends to improve these characteristics. This is mainly carried out on cold-rolled steel like wire-drawn steel, centrifugally cast ductile iron pipe etc. A full annealing typically results in the second most ductile state a metal can assume for metal alloy. Its purpose

1036-424: The material to fully form austenite or austenite-cementite grain structure. The material is then allowed to cool very slowly so that the equilibrium microstructure is obtained. In most cases this means the material is allowed to furnace cool (the furnace is turned off and the steel is let cool down inside) but in some cases it is air cooled. The cooling rate of the steel has to be sufficiently slow so as to not let

1073-450: The metal is softened and prepared for further work such as shaping, stamping, or forming. Many other materials, including glass and plastic films , use annealing to improve the finished properties. Annealing occurs by the diffusion of atoms within a solid material, so that the material progresses towards its equilibrium state. Heat increases the rate of diffusion by providing the energy needed to break bonds. The movement of atoms has

1110-405: The metal to lose a substantial part of its original strength. This can however be regained with hardening . The high temperature of annealing may result in oxidation of the metal's surface, resulting in scale. If scale must be avoided, annealing is carried out in a special atmosphere , such as with endothermic gas (a mixture of carbon monoxide , hydrogen gas , and nitrogen gas ). Annealing

1147-464: The object in contact with the water, thus facilitating better conduction of heat from the object to the surrounding water. Quench hardening is generally applicable to some ferrous alloys, but not copper alloys. In the semiconductor industry, silicon wafers are annealed to repair atomic level disorder from steps like ion implantation . In the process step, dopant atoms, usually boron , phosphorus or arsenic , move into substitutional positions in

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1184-503: The parts in and out. Once the annealing process is successfully completed, workpieces are sometimes left in the oven so the parts cool in a controllable way. While some workpieces are left in the oven to cool in a controlled fashion, other materials and alloys are removed from the oven. Once removed from the oven, the workpieces are often quickly cooled off in a process known as quench hardening. Typical methods of quench hardening materials involve media such as air, water, oil, or salt. Salt

1221-499: The properties required. With knowledge of the composition and phase diagram , heat treatment can be used to adjust from harder and more brittle to softer and more ductile. In the case of ferrous metals , such as steel , annealing is performed by heating the material (generally until glowing) for a while and then slowly letting it cool to room temperature in still air. Copper , silver and brass can be either cooled slowly in air, or quickly by quenching in water. In this fashion,

1258-421: The smaller one ( 5 – 20 mm) is used for hearth layer in sinter machine and the rest is taken to the blast furnace along with the biggest sized sinters. The temperature is typically maintained between 1,150 and 1,250 °C (2,100 and 2,280 °F) in the ignition zone and between 900 and 1000 °C in the soaking zone to prevent sudden quenching of the sintered layer. The top 5 mm from screens goes to

1295-601: The steel just above its upper critical point creates austenitic grains (much smaller than the previous ferritic grains), which during cooling, form new ferritic grains with a further refined grain size. The process produces a tougher, more ductile material, and eliminates columnar grains and dendritic segregation that sometimes occurs during casting. Normalizing improves machinability of a component and provides dimensional stability if subjected to further heat treatment processes. Process annealing, also called intermediate annealing , subcritical annealing , or in-process annealing ,

1332-437: The steel. The three stages of the annealing process that proceed as the temperature of the material is increased are: recovery , recrystallization , and grain growth . The first stage is recovery , and it results in softening of the metal through removal of primarily linear defects called dislocations and the internal stresses they cause. Recovery occurs at the lower temperature stage of all annealing processes and before

1369-408: The wire passes across after it is drawn. The two pulleys have an electrical potential across them, which causes the wire to form a short circuit. The Joule effect causes the temperature of the wire to rise to approximately 400 °C. This temperature is affected by the rotational speed of the pulleys, the ambient temperature, and the voltage applied. Where t is the temperature of the wire, K

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