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...

Combined blowing process in converter steel making Apr30

Combined blowing process in converter steel making...

  Combined blowing process in converter steel making Inhomogeneities in chemical composition and temperature are created in the melt during the oxygen blow in the top blown converters due to the lack of the mixing in the metal bath. There is a relatively dead zone directly under the jet cavity in the converter. The necessity to improve the steel making process in the top blown converter has led to the development of the combined blowing process. The first combined blowing practice to be commercially accepted was the LBE (Lance Bubbling Equilibrium) process developed by ARBE-IRSID. This process is much more closely related to the BOF process in that all the oxygen is supplied from the top lance. The combined blowing aspect is achieved by a set of porous elements installed in the bottom of the converter through which argon or nitrogen is blown. In LBE process the nitrogen gas is typically used almost exclusively for the majority of the blow in the range of 3 -11 N Cum/min. However in the later part of the blow when nitrogen absorption can create a problem, argon gas is used for stirring. In addition, argon is used almost exclusively as the inert gas for post blow stirring, at this time the rate is increased to 10-17 N Cum/min. The process is shown in Fig.1. Fig 1 Combined blowing processes The profile of a porous element is shown in Fig 2   Fig 2 Profile of a porous element for the LBE process The bottom buildup and the subsequent loss of the porous element is the major problem associated with this process. The difficulties in maintaining the LBE elements operational have led to pursue the application of the non cooled tuyeres. Here also the oxygen is delivered through...