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...

Welding Processes Apr10

Welding Processes

Welding Processes Welding is a fabrication process that joins materials by causing coalescence. Welding is normally carried out by melting the work pieces and adding a filler material to form a pool of molten material that cools to become a strong joint, either with pressure sometimes used in conjunction with heat, or by itself, to produce the weld. This is in contrast with soldering and brazing, which involve melting a lower melting point material between the work pieces to form a bond between them, without melting the work pieces. Welding usually requires a heat source to produce a high temperature zone to melt the material, though it is possible to weld two metal pieces without much increase in temperature. There are some methods with solid phase joining. In these methods there is no melting of the electrodes, though heat is produced in the process. Also since the work pieces are closely pressed together, air is excluded during the joining process. In normal welding the melted and solidified material is normally weaker than the wrought material of the same composition. In the solid phase joining such melting does not occur and hence the method can produce joints of high quality. Metals which are dissimilar in nature can also be readily welded by these methods. In the normal welding process, joining of dissimilar metals presents problems since brittle intermetallic compounds are formed during melting. Modern welding technology started just before the end of the 19th century with the development of methods for generating high temperature in localized zones. There are different methods and standards adopted and there is still a continuous search for new and improved methods of welding. Though the different welding processes have their own advantages and limitations and are required for special and specific applications,...