Steelmaking by Induction Furnace Mar26

Steelmaking by Induction Furnace...

Steel making by Induction Furnace Though induction furnaces are being used since a long time, the production of mild steel by the induction furnace (IF) is relatively a very recent phenomenon. Induction furnaces work on the principle of electromagnetic induction which was discovered by Michael Faraday. History In 1870 De Ferranti started experiments in Europe on induction furnaces. The first induction furnace for melting metals was patented by Edward Allen Colby in 1900. The first steel made in an induction furnace in United States was in 1907 in a Colby furnace near Philadelphia. First 3 phase furnace was built in Germany in 1906 by Rochling- Rodenhauser. In India the use of induction furnaces started in mid sixties. Imported medium frequency induction furnaces were used from mid seventies. Early eighties to mid nineties sudden growth has taken place. During this period indigenous manufacture of the induction furnaces also started. Initially induction furnaces were used for melting stainless steel scrap but these furnaces are used for mild steel production from mid eighties. Characteristics of Induction furnace There are mainly two types of the induction furnaces. They are given below. i) Induction channel furnace – In this furnace induction heating takes place in the channel which is a small and narrow area at the bottom of the main bath. The channel passes through a steel core and the coil assembly. Such type of furnaces are not been used for the steel making. ii) Induction crucible furnace- This type of the furnace is also called coreless induction furnace. It is a refractory lined vessel (Crucible). Its other main components are power supply unit consisting of transformer, inverter and capacitor bank, the charging arrangement, the cooling system for the power supply and furnace coil, process control system and the...

Glossary of terms used in heat treatment of steel...

          Glossary of terms used in heat treatment of steel Various terms used in the heat treatment of steels are described below: Ageing – It describes a time temperature dependent change in the properties of certain alloy steels. It is a change in properties that may occur gradually at atmospheric temperature (Natural ageing) and more rapidly at higher temperature (Artificial ageing). Quench ageing – It is a change in properties that may occur gradually at atmospheric temperature and more rapidly at higher temperature following rapid cooling (Precipitation hardening). Strain ageing – It is a change in properties that may occur gradually at atmospheric temperature and more rapidly at higher temperature following plastic straining. Annealing – It is a term denoting a treatment, consisting of heating to and holding at a suitable temperature followed by cooling at a suitable rate, used primarily to soften but also to simultaneously produce desired changes in other properties or in microstructure. The purpose of such changes may be, but is not confined to: Inducing softness Improving machinability Improving cold working properties Improving mechanical or electrical properties Increasing stability of dimensions Obtaining a desired structure Removing stresses The time temperature cycle used vary widely both in maximum temperature attained and in cooling rate employed, depending on the composition of the steel, its condition, and the result desired. Various types of annealing processes are as follows: Bright annealing– It is annealing in a protective medium to prevent discoloration of the bright surface. Cycle annealing – It is an annealing process employing a predetermined and closely controlled time temperature cycle to produce specific properties or microstructure. Flame annealing – It is an annealing process in which the heat is applied directly by a flame. Full annealing – It is heating to and...

Slag splashing technique in converter operation Mar24

Slag splashing technique in converter operation...

                     Slag splashing technique in converter operation  The erosion of refractory lining of a converter has a major contribution for the low lining life. Erosion occurs because of chemical erosion due to attack of slag and molten metal on the refractory of the converter at the high operating temperatures and because of thermal shocks as well as due to mechanical wear.  Slag splashing technique has been developed to counter this erosion and produce a freeze lining. Today slag splashing has become a powerful tool not only for increasing of the lining life of the converter but for increasing of the converter availability and maximizing of production besides reducing of the refractory and gunning costs. History Slag splashing technique was first developed in 1970 but was not put to large scale use. The Indiana Harbour plant of LTV steel was first to report success in 1992 with respect to improvement in the lining life by the use of this technique. Slowly this technique was used in the other steel melting shops of the world. Inland no. 4 BOF shop has reported a lining life of plus 60,000 heats. The process The slag splashing steps are as follows At the end of the previous heat the liquid steel is tapped in steel teeming ladle and molten slag remains in the converter. The converter operator visually inspects the slag condition to determine the quantity of slag conditioner to be added. The converter operator visually inspects the converter lining to determine if any specific area of the lining needs special attention. The molten slag is conditioned with respect to its temperature, FeO and MgO contents by the addition of a conditioner in required quantity. The converter is rocked for slag coating of the charge pad and tapping pad....

Blast Furnace gas generation and usage Mar18

Blast Furnace gas generation and usage...

Blast Furnace gas generation and usage Blast furnace (BF) gas is a gaseous by product which is generated while producing hot metal (liquid iron) in a blast furnace. The operation of the blast furnace is controlled to produce hot metal of a specified quality and during this production BF gas comes out from the furnace top. During production of hot metal in a blast furnace, hot air blast is blown in the furnace through the tuyeres. The oxygen of the blast reacts with the coke. The gas produced by this reaction moves up the furnace shaft which has been charged with ores, fluxes and coke. After a number of chemical reactions and a travel of around 25-30m the BF gas comes out of the furnace as a heated, dust laden and lean combustible gas. Around 1500-1700 Cu m/ton of hot metal of BF gas is generated during the process. Though the purpose of partial combustion of carbon in a blast furnace is to remove the oxygen from the ore but the volume of gas generated in a blast furnace makes the blast furnace as a gas producer. The percentage of CO and CO2 in BF gas is directly related to the amount of carbon in the charged coke and amount of CO2 in the charged flux (Limestone and dolomite). The coke rate (The rate of carbon consumption) in the blast furnace depends mainly upon the type of the hot metal to be made, the chemical and the physical characteristics of the charged materials, the distribution of the materials in the furnace stack, the temperature and the oxygen enrichment of the hot air blast. The total amount of CO+CO2 gases by volume in the BF gas at the furnace top is around 40% of the...

Direct Reduced Iron and its Production Processes Mar16

Direct Reduced Iron and its Production Processes...

Direct Reduced Iron and its Production Processes Direct reduced iron (DRI) is technically defined as iron ore which has been reduced to metal without melting it. Hot briquetted iron (HBI) is a densified form of DRI to facilitate its handling and transport. History The first patent was in 1792 in United Kingdom presumably utilizing a rotary kiln but the development of the modern direct reduction (DR) process began in the middle of 19th century. Since 1920 more than 100 DR have been invented and operated. Most of them have not survived. The modern era of DR production began on December 5, 1957 when the HYL process plant first started production at Hylsa. The  first plant using Midrex process came into operation in May 17, 1969 at Oregon Steel mills in Portland, Oregon. DRI Production process A DRI production process is one in which the solid metallic iron is obtained directly from solid iron ore without subjecting the ore or the metal to fusion. The process principle is shown in Fig. 1. Fig 1 DRI process principle Major DRI production processes are either gas based or coal based. Feed material in a DRI process is either iron ore sized to 10 to 30mm or iron ore pellets produced in an iron ore pellet plant. In the gas based plant the reactor, the reduction reaction takes place is a shaft furnace. The shaft furnace works on counter current principle where the iron ore feed material moves downward in the furnace by gravity and gets reduced by the up flowing reducing gases. The pressure and temperature in shaft furnace in HYL process is 5-6 bars and 800-850 deg C. The same in Midrex process is 1-1.5 bar and 800-850 deg. C. In a coal based plant the...