Developments of Steelmaking Processes Feb22

Developments of Steelmaking Processes...

Developments of Steelmaking Processes The earliest known production of steel are pieces of ironware excavated from an archaeological site in Anatolia and are nearly 4,000 years old, dating from 1800 BCE (before common era). Horace identified steel weapons like the falcata in the Iberian Peninsula, while Noric steel was used by the Roman army. The reputation of ‘Seric iron’ of South India (wootz steel) amongst the Greeks, Romans, Egyptians, East Africans, Chinese and the Middle East grew considerably. South Indian and Mediterranean sources including Alexander the Great (3rd century BCE) recount the presentation and export to the Greeks of such steel. Metal production sites in Sri Lanka employed wind furnaces driven by the monsoon winds, capable of producing high-carbon (C) steel. Large-scale wootz steel production in Tamilakam using crucibles and C sources such as the plant Avaram occurred by the sixth century BCE, the pioneering precursor to modern steel production and metallurgy. Steel was produced in large quantities in Sparta around 650 BCE. The Chinese of the Warring states period (403 BCE to 221 BCE) had quenched hardened steel, while Chinese of the Han dynasty (202 BCE to 220 CE) created steel by melting together wrought iron with cast iron, gaining an ultimate product of a carbon-intermediate steel by the 1st century CE (common era). The Haya people of East Africa invented a type of furnace they used to make C steel at 1,800 deg C nearly 2,000 years ago. East African steel has been suggested by Richard Hooker to date back to 1400 BCE. Evidence of the earliest production of high C steel in the Indian subcontinent is found in Kodumanal in Tamilnadu, Golkonda in Telengana, and Karnataka and in Samanalawewa areas of Sri Lanka. This steel known as wootz steel, produced by about sixth century BCE was exported globally. The steel technology existed prior to 326 BCE in the region as they are mentioned in...

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...

Blowing of Oxygen in Converter Steelmaking Sep14

Blowing of Oxygen in Converter Steelmaking...

 Blowing of Oxygen in Converter Steelmaking Oxygen (O2) is blown on the hot metal in the converter during steel making for removal of impurities such as carbon (C), silicon (Si), manganese (Mn), and phosphorus (P) etc.  A water cooled lance is used to inject oxygen at very high velocities onto a liquid bath to produce steel. In the 1950s when the top blown converter process was commercialized and the size of the converter was limited to 50 tons maximum then a lance with a single hole lance tip was being used for the blowing of O2 in the converter. With the passage of time the converter size went on increasing. This has necessitated increase of number of holes in the lance tip for better distribution of O2 over a larger surface of the bath in the converter. With the increasing demands to produce higher quality steels with lower impurity levels, O2 of very high purity is required for steelmaking in the converter. The O2 needed for steelmaking is to be at least 99.5 % pure, and ideally 99.7 % to 99.8 % pure. The remaining parts are 0.005 % to 0.01 % nitrogen (N2) and the rest is argon (Ar). In top-blown converters, the O2 is jetted at supersonic velocities with convergent divergent nozzles at the tip of the water cooled lance. A forceful gas jet penetrates the slag and impinges onto the surface of the liquid bath to refine the steel. Today most of the converters operate with lance tips containing 3 to 6 nozzles. Even 8 nozzles lance tips are under use. The axes of each of the nozzles in a lance with a multi hole lance tip are inclined with respect to the lance axes and equally spaced around the tip....

Quality of Lime for Steelmaking in Converter Sep08

Quality of Lime for Steelmaking in Converter...

Quality of Lime for Steelmaking in Converter Lime is a white crystalline solid with a melting point of 2572 deg C. It is a basic oxide and is used to react with the acidic oxides (e.g. silica). It is calcium oxide (CaO) produced on heating (calcination) of limestone (CaCO3) to a temperature of 900 deg C and above (usually 1100 deg C). CaCO3(s) + heat = CaO(s) + CO2 (g) This reaction is reversible. Calcium oxide reacts with carbon dioxide to form calcium carbonate. The reaction is driven to the right by flushing of carbon dioxide from the mixture as it is released. Hydrated lime Ca(OH)2 is formed by reaction of lime with water (slaking). Hydrated lime is also known as slaked lime. CaO + H2O = Ca(OH)2 + heat Lime as a basic flux in steel production and it plays an important role in the sequence of metallurgical reactions taking place in a converter. Steel is produced from hot metal by oxidizing sulphur (S), phosphorus (P), carbon (C), silicon (Si), manganese (Mn), and other impurities so that they can enter the slag or gas phases, thus separating from the metal phase. Lime in steelmaking is mainly used to produce slag for the removal of these harmful elements in liquid bath and optimize the quality of liquid steel. The basic oxygen process oxidizes impurities in an oxygen converter also known as basic oxygen furnace (BOF) where the hot metal comes in contact with oxygen. Oxidized impurities of the hot metal are absorbed in a slag, which is formed with the help of calcined lime. Metallurgical lime in the fifties consisted of a mixture of particles of all sizes from very coarse to very fine, with additional components such as silicon dioxide and sulphur concentrated...