Steelmaking in Induction Furnace May24

Steelmaking in Induction Furnace...

Steelmaking in Induction Furnace Coreless induction furnaces have been used in the ferrous industry for over 50 years and are now one of the most popular means of melting and holding ferrous materials. Induction melting had dramatic growth during the 1960s based on line frequency technology, and later with the large-scale introduction of medium frequency power supply during the 1980s. Making of mild steel in the induction furnace was first experimented during early 1980s and it gained popularity when the production of sponge iron utilizing coal based process of rotary kilns became popular. Induction furnace is a type of electric melting furnace which uses electric current to melt metal. The principle of induction melting is that a high voltage electrical source from a primary coil induces a low voltage, high current in the metal (secondary coil). Induction heating is simply a method of transfer of the heat energy. Two laws which govern induction heating are (i) electromagnetic induction, and (ii) the joule effect. Coreless induction furnace comprises a relatively thin refractory crucible encircled by a water cooled copper coil excited from a single AC supply. When the coil is energized, the fluctuating axial magnetic field causes a current to flow in electrically conducting pieces of charge material within the crucible. The power induced in the charge depends on the physical properties of the material, the flux linking it and its geometric shape. Dependent on the resistivity of the material being melted, the coreless induction furnace converts electrical energy to heat the charge at an efficiency of between 50 % and 85 %, although furnace efficiency is further reduced by thermal losses from radiation from the melt surface and conduction through the furnace lining. Medium frequency induction furnaces which are commonly used for steelmaking use...

Alumina and its Role in Iron and Steelmaking...

Alumina and its Role in Iron and Steelmaking Alumina is a chemical compound of aluminum (Al) and oxygen (O2) with the chemical formula aluminum oxide (Al2O3). It is the most commonly occurring of several aluminum oxides. It is significant in its use to produce aluminum metal. It is being used as an abrasive material because of its hardness. It is also being used as a refractory material owing to its high melting point. Aluminum oxide is an amphoteric substance. It can react with both acids and bases, acting as an acid with a base and a base with an acid, neutralizing the other and producing a salt.  It is insoluble in water. Aluminum oxide has a white solid appearance and is odorless. The molar mass of aluminum oxide is 101.96 grams per mole. Specific gravity of alumina is 3.986. It is insoluble in water. Melting point of aluminum oxide is 2072 deg C while the boiling point is 2977 deg C. Alumina affects the processes of producing iron and steel during the production of iron and steel. Besides alumina is a very important refractory material for the lining of furnaces and vessels in iron and steel plants. Role of alumina in ironmaking Alumina during ironmaking enters the process through impurities in the input materials mainly iron ore. Alumina affects the sintering of iron ore. The most harmful effect of alumina is to worsen the RDI (reduction degradation index) value of sinter. RDI value increases as the alumina content rises. It is seen that within a 10 % to 10.5 % CaO content range, an increase of 0.1 % in the alumina content raises the RDI by 2 points. The strength and quality of sinter deteriorate as the alumina content rises. Alumina promotes the formation of SFCA (silico ferrite of calcium and aluminum), which is beneficial for sinter strength, but the strength of the ore components is lower, since a...

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....