Refractories for a Reheating Furnace...

Refractories for a Reheating Furnace Refractories are inorganic, nonmetallic, porous and heterogeneous materials composed of thermally stable mineral aggregates, a binder phase and additives. They are the materials which are resistant to heat and exposure to different degrees of mechanical stress and strain, thermal stress and strain, corrosion/erosion from solids, liquids and gases, gas diffusion, and mechanical abrasion at various temperatures. In simplified language, refractories are considered to be materials of construction which are able to withstand high temperatures. The general requirements from the refractories for are (i) ability to withstand high temperatures and trap heat within a limited area such as a reheating furnace, (ii) ability to withstand sudden changes of temperature, (iii) ability to withstand load at service conditions, (iv) ability to withstand chemical and abrasive action of the materials such as liquid metal, liquid slag, and hot gases etc. coming in contact with the refractories, (v) ability to resist contamination of the material such as scale etc. with which it comes into contact, (vi) ability to maintain sufficient dimensional stability at high temperatures and after/during repeated thermal cycling, (vii) ability to conserve heat, (viii) ability to withstand load and abrasive forces, and (ix) to have low coefficient of thermal expansion. Properties of the refractories can be classified to resist four types of service stresses namely (i) chemical, (ii) mechanical, (iii) thermal, and (iv) thermo-technical. A suitable selection of the refractories for the lining of the reheating furnace can only be made with an accurate knowledge of the refractory properties and the stresses on the refractories during service. The relationship between service stresses and important properties of the refractories are at Tab 1.  Tab 1 Relationship between type of stress and refractory property Sl.No. Type of stress Important refractory property 1 Chemical...

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...