Molten iron

Reduction by aluminium has been used to produce molten iron in situ for welding steel and as a method of extracting metals. 

Reaction (13.4) is exothermic and reversible, and begins at about 700 K by Le Chatelier s Principle, more iron is produced higher up the furnace (cooler) than below (hotter). In the hotter region (around 900 K), reaction (13.5) occurs irreversibly, and the iron(II) oxide formed is reduced by the coke [reaction (13.6)] further down. The limestone forms calcium oxide which fuses with earthy material in the ore to give a slag of calcium silicate this floats on the molten iron (which falls to the bottom of the furnace) and can bo run off at intervals. The iron is run off and solidified as pigs —boat-shaped pieces about 40 cm long. 

Inductor. The channel inductor assembly consists of a steel box or case that contains the inductor refractory and the inductor core and coil assembly. The channel is formed within the refractory. Inductor power ratings range from 25 kilowatts for low temperature metals to 5000 kilowatts for molten iron. Forced air is used to cool the lower power inductors, and water is generally used to cool inductors rated 500 kilowatts or more. 

Processes operating ia the range of 1300—1530°C produce molten iron, called hot metal or pig iron. These processes are classified as direct smelting processes. Processes operating above 1530°C produce molten steel (qv) and are called direct steehnakiag processes. 

The dissolution of carbon in molten iron in the lower part of the furnace, leads to the reduction of manganese oxide (eq. 15) and some sihea (eq. 14), both in the slag, whereby the subsequent dissolution of these metals occurs in the molten iron. 

Magnesium ferrosihcon alloys react vigorously when added to molten iron. As the magnesium vaporizes and cools, it reacts with residual surface tension modifiers such as sulfur and oxygen and greatly increases the surface tension of the molten iron. The dissolved graphite in the molten iron nucleates and grows into a spheroidal shape because of the increased surface tension of the molten iron. 

A number of high temperature processes for the production of titanium carbide from ores have been reported (28,29). The aim is to manufacture a titanium carbide that can subsequently be chlorinated to yield titanium tetrachloride. In one process, a titanium-bearing ore is mixed with an alkah-metal chloride and carbonaceous material and heated to 2000°C to yield, ultimately, a highly pure TiC (28). Production of titanium carbide from ores, eg, ilmenite [12168-52-4], EeTiO, and perovskite [12194-71 -7], CaTiO, has been described (30). A mixture of perovskite and carbon was heated in an arc furnace at ca 2100°C, ground, and then leached with water to decompose the calcium carbide to acetjdene. The TiC was then separated from the aqueous slurry by elutriation. Approximately 72% of the titanium was recovered as the purified product. In the case of ilmenite, it was necessary to reduce the ilmenite carbothermaHy in the presence of lime at ca 1260°C. Molten iron was separated and the remaining CaTiO was then processed as perovskite. 

In North America the individual blocks of carbon used in the hearth bottom have exceeded 6 m in length. In Europe and Asia these blocks are much shorter because of manufacturing capabiHties. The longer bottom blocks permit the spanning of the hearth diameter with only two pieces, which prevents flotation of the carbon by the denser molten iron. This is because the bearing provided by the dead load of the hearth walls, which rest on the ends of the carbon block "beams," anchors the bottom blocks and prevents flotation. If smaller blocks are utilized with two or more joints across the bottom, special reverse taper mating surfaces or interlocking techniques are required to prevent block flotation. 

Carbon brick and block ate used to line the cupola well (73) or cmcible. When properly installed and cooled carbon linings last for many months or even years of intermittent operation. Their resistance to molten iron and both acid and basic slags provides not only insurance against breakouts but also operational flexibility to produce different iron grades without the necessity of changing refractories. Carbon is also widely used for the tap hole blocks, breast blocks, slagging troughs, and dams. 

White cast iron is brittle and difficult to machine. It is made by controlling the composition and rate of solidification of the molten iron so that all the carbon is present in the combined form. Very abrasive- and wear-resistant, white cast iron is used as liners and for grinding balls, dies, and pump impellers. 

There are two process routes for making steel in the UK today the electric arc furnace and the basic oxygen converter. The latter requires a charge of molten iron, which is produced in blast furnaces. The raw materials for producing molten iron are iron ore, coking coal, and fluxes (materials that help the chemical process) - mainly limestone. 

The Japanese Direct Iron Ore Smelting (DIOS) process. This process produces molten iron directly with coal and sinter feed ore. A 500 ton per day pilot plant was started up in October, 1993 and the designed production rates were attained as a short term average. Data generated is being used to determine economic feasibility on a commercial scale. 

The first stage in the conversion of iron ore to steel is the blastfurnace (see Panel), which accounts for the largest tonnage of any metal produced by man. In it the iron ore is reduced by coke, while limestone removes any sand or clay as a slag. The molten iron is run off to be cast into moulds of the required shape or into ingots ( pigs ) for further processing — hence the names cast-iron or pig-iron . This is an... 

Kassner used a rotating disc, for which the hydrodynamic conditions are well defined, to study the dissolution kinetics of Type 304 stainless steel in liquid Bi-Sn eutectic. He established a temperature and velocity dependence of the dissolution rate that was consistent with liquid diffusion control with a transition to reaction control at 860 C when the speed of the disc was increased. The rotating disc technique has also been used to investigate the corrosion stability of both alloy and stainless steels in molten iron sulphide and a copper/65% calcium melt at 1220 C . The dissolution rate of the steels tested was two orders of magnitude higher in the molten sulphide than in the metal melt. 

Enough heat Is generated to produce molten Iron, which can be seen flowing out of the broken pot onto the protective mat at the bottom of the stand. 

Molten iron, formed at a temperature of 1600°C, collects at the bottom of the furnace. Four or five times a day, it is drawn off. The daily production of iron from a single blast furnace is about 1500 metric tons. 

The slag, which is less dense than molten iron, forms a layer on the surface of the metaL This makes it possible to draw off the slag through an opening in the furnace above that is used to remove the iron. The slag is used to make cement and as a base in road construction. 

The thermite reaction is spectacular and highly exothermic. It involves the reaction between Fe203, ferric oxide, and metallic aluminum. The reaction produces white-hot, molten iron in a few seconds. Given ... 

Molten CaSi03 is less dense than molten iron and floats on top of it. An average furnace that produces about 750 tons of iron per day, will also yield 410 tons of slag. The slag is sometimes useful in the manufacture of cement and, when it contains sufficient phosphorus, in the manufacture of fertilizer. 

The temperature of molten iron can be estimated by using Wien s law. If the melting point of iron is 1540°C, what will be the wavelength (in nanometers) corresponding to maximum intensity when a piece of iron melts ... 

FIGURE 6.8 The thermite reaction is so exothermic that it melts the metal that it produces and is used to weld railroad tracks together. Here, aluminum metal is reacting with iron(lll) oxide. Fe20 causing a shower of molten iron sparks. 

The mixture of products, which is known as slag, is molten ar the temperatures in the furnace and floats on the denser molten iron. It is drawn off and used to make rocklike material for the construction industry. 

Molten iron is produced through a series of reactions in the four main temperature zones of the furnace. At the bottom, in Zone A, preheated air is blown into the furnace under pressure, and the coke is oxidized to heat the furnace to 1900°C and provide carbon in the form of carbon dioxide. Higher up, the iron is reduced in... 

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