History of Basic Oxygen Steelmaking Dec16

History of Basic Oxygen Steelmaking...

History of Basic Oxygen Steelmaking  Basic oxygen steelmaking (BOS) is the process of making steel by blowing pure oxygen (O2) in a liquid metal bath contained in a vessel which is known as basic oxygen furnace (BOF), LD converter, or simply converter. The history of steelmaking began in the 19th century, when Reaumur of France in 1772, Kelly of the United States in 1850 and Bessemer of Britain in 1856 discovered how to improve on pig iron by controlling the carbon content of iron alloys, which thus truly become steels. While Reaumur, a chemist, was driven by scientific curiosity, but Kerry and Bessemer being engineers, were responding to the need for larger quantities and better qualities of steel which the industrial revolution, with its looms, steam engines, machines and railroads, had created. This had started a dialectical relationship between science and technology and the basic concepts of refining hot metal (pig iron) by oxidizing carbon (C) in a liquid bath were invented at that time. This was a radical change from the gas-solid reaction in the shaft furnaces, the predecessors of blast furnaces which reduce iron ore with charcoal, or from the puddling of iron which was a forging and refining technology carried out in the solid state and which has no equivalent in the present time. The intensity of innovations which at the second half of the 19th century was impressive and it brought a paradigm shift. Steel making by Bessemer converter came into existence in 1856, the open hearth furnace, which can melt scrap in addition to refining hot metal, was discovered nine years only after the Bessemer converter in 1865, and the basic Thomas converter twelve years later in 1877.  The Thomas converter was using air for the refining of the...

Understanding Steel Making Operations  in Basic Oxygen Furnace Mar02

Understanding Steel Making Operations in Basic Oxygen Furnace...

Understanding Steel Making Operations  in Basic Oxygen Furnace  Steel making operation in the basic oxygen furnace (BOF) is also sometimes called basic oxygen steel making (BOS). This is the most powerful and effective steel making technology in the world. Around 71 % of the crude steel is made by this process. BOF process was developed in Austria in the early 1950s at the two Austrian steelworks at Linz and Donawitz and hence the BOF process is also called LD (first letters of the two cities) steel making. There exist several variations on the BOF process. The main are top blowing, bottom blowing, and a combination of the two which is known as combined blowing. The BOF process is autogenous, or self sufficient in energy, converts liquid iron (hot metal) into steel using gaseous oxygen (O2) to oxidize the unwanted impurities in hot metal (HM). The O2 used must be of high purity, usually 99.5% minimum, otherwise the steel may absorb harmful nitrogen (N2). The primary raw materials for the BOF are generally HM (around 80 % or more) from the blast furnace and the remaining steel scrap. These are charged into the BOF vessel. O2 is blown into the BOF at supersonic velocities. It oxidizes the carbon (C) and silicon (Si) contained in the HM liberating great quantities of heat which melts the scrap. There are lesser energy contributions from the oxidation of iron(Fe), manganese (Mn), and phosphorus (P). The flux used in this process is primarily calcined lime ( with CaO content of more than 92 %). This lime is produced by the calcining of limestone with low silica (SiO2) content. The post combustion of carbon monoxide (CO) as it exits the converter also transmits heat back to the bath. The product of...

Design Features of an AC Electric Arc Furnace Feb24

Design Features of an AC Electric Arc Furnace...

Design Features of an AC Electric Arc Furnace  Electric arc furnace (EAF) used for steel making apply high current and low voltage electric energy to the charge materials , and thereby melt and refine them. EAF is a batch furnace which consists of a refractory lined vessel covered with a retractable roof through which electrodes enter the furnace. General features of a typical AC electric arc furnace is shown in Fig 1. Fig 1 General features of an AC electric arc furnace  EAF has a large bowl shaped body with a dish shaped hearth. The shell has a refractory lining inside. The reaction chamber of the furnace is covered from above by a removable roof made of refractory bricks held by a roof ring. It is fed with a three phase alternating current (AC) and has three graphite electrodes which are connected by flexible cables and water cooled copper tubes. The design of electric arc furnaces has changed considerably in recent years. Emphasis has been placed on making furnaces larger, increasing power input rates to the furnace and increasing the speed of furnace movements in order to minimize power off time in furnace operations. Modern steel melting shops with EAFs usually employ a mezzanine furnace installation. In this type of installation, the furnace sits on an upper level above the shop floor. The furnace is supported on a platform which can take on several different configurations. In the half platform configuration, the electrode column support and roof lifting gantry is hinged to the tiltable platform during operation and tapping. When charging the furnace, the complete assembly is lifted and swiveled. This design allows for the shortest electrode arm configuration. In the full platform design, the electrode column support and roof lifting assembly is completely...