Understanding Electric Arc Furnace Steel Making Operations Feb18

Understanding Electric Arc Furnace Steel Making Operations...

Understanding Electric Arc Furnace Steel Making Operations  Electric arc furnace (EAF) steel making technology is more than hundred years old. Though De Laval had patented an electric furnace for the melting and refining of iron in 1892 and Heroult had demonstrated electric arc melting of ferro alloys between 1888 and 1892, the first industrial EAF  for steel making only came into operation in 1900. Development was rapid and there was a tenfold increase in production from 1910 to 1920, with over 500,000 tons being produced in 1920, though this represented still only a very small percentage of the global production of steel  of that time. Initially, EAF steelmaking was developed for producing special grades of steels using solid forms of feed such as scrap and ferro alloys. Solid material were firstly melted through direct arc melting, refined through the addition of the appropriate fluxes and tapped for further processing. Fig 1 shows a typical plan and section view of an EAF Fig 1 Typical plan and section view of an EAF  Electric arc furnaces range in capacity from a few tons to as many as 400 tons, and a steel melting shop can have a single furnace or up to three or four. In brief, these furnaces melt steel by applying an AC current to a steel scrap charge by mean of graphite electrodes. It requires a tremendous quantity of electricity. The melting process involves the use of large quantities of energy in a short time and in some instances the process has caused disturbances in power grids. These disturbances have usually been characterized as ‘flicker’ (brief irregularities in voltage a fraction of the 50 -60 Hz cycle in length), and ‘harmonics’ (irregularities that tend to occur in a pattern repetitive to the 50-60 Hz...

Monolithic Refractories...

Monolithic Refractories  Monolithic refractory is the name normally given to all unshaped refractory products, the word monolithic coming from the word monolith meaning ‘big stone’. Monolithic refractories are special mixes or blends of dry granular or cohesive plastic materials used to form virtually joint free linings. They are unshaped refractory products which are installed as some form of suspension that ultimately harden to form a solid mass. Most monolithic formulations consist of large refractory particulates (an aggregate), fine filler materials (which fill the inter particle voids) and a binder phase (that gels the particulates together in the green state). Monolithic refractories represent a wide range of mineral compositions and vary greatly in their physical and chemical properties. Some are low in refractoriness while others approach high purity brick compositions in their ability to withstand severe environments. Monolithic refractories are replacing the conventional type fired refractories at a much faster rate in many applications including those of industrial furnaces. Monolithic refractories are used to advantage over brick construction in different type of furnaces. Their use promotes quick installation, avoid delays for the manufacture of special brick shapes. Use of monolithics frequently eliminates difficult brick laying tasks, which may be accompanied with weakness in construction. They are of major importance in the maintenance of furnaces because substantial repairs can be made with a minimum loss of time and, in some cases, even during operations. Under certain conditions, monolithic linings of the same composition as firebrick provide better insulation, lower permeability and improved resistance to the spalling effects of thermal shock. With little or no preparation, monolithic refractories can be applied to form monolithic or joint free furnace linings in new constructions or to repair existing refractory lining. Other major advantages of monolithic refractory linings are as follows. It...

Management of Financial Resources for Sustained Success...

Management of Financial Resources for Sustained Success  Financial resource is a very important resource which an organization needs not only for its functioning  but also for its sustained success. For this purpose the organization need to have systems in place that help it to both fund its ambitions and also to manage its financial resources in support of its daily operations, including funding for improvement activities. Normally financial controls are applied by the management which enable it to take a proactive management position in the business. The three most important financial controls are namely (i) the balance sheet, (ii) the profit and loss statement, and (iii) the cash flow statement. But the management of financial resources is much more than the exercising of the financial controls. The management of the financial resources is an important function of the management in the organization. This financial management starts with the financial planning. Financial planning is a continuous process of directing and allocating financial resources to meet strategic goals and objectives. The output from financial planning normally takes the form of budgets. Financial planning works from the strategic and business plans to identify what financial resources are needed to obtain and develop the resources to achieve the goals in the two types of plans. Typically, financial planning results in very relevant and realistic budgets. Financial planning normally starts at the top of the organization and has basically two components namely (i) planning for operations, and (ii) planning for financing. Operating people focus on production and sales while financial planners are interested in how to finance the operations. Financial planning is the process that encompasses both operations and financing. In a normal organization, typical financial functions within an organization are a host of the accounting activities such as...

Induction Furnace and Important Operational Aspects Feb14

Induction Furnace and Important Operational Aspects...

Induction Furnace and Important Operational Aspects   The development of the induction furnace for steel making has been a boon to the small steel producers. These furnaces are easy to install, operate and maintain. These furnaces are smaller in heat size with a low cost investment and preferred by lower capacity steel plants. In these furnaces, steel is produced by melting the charge material using the heat produced by electromagnetic field. The induction furnace consists basically of a crucible, inductor coil, and shell, cooling system and tilting mechanism. The crucible is formed from refractory material, which the furnace coils is lined with. This crucible holds the charge material and subsequently the melt. The choice of refractory material depends on the type of the charge and basically consist of either acidic, basic or neutral refractories. The inductor coil is a tubular copper coil with specific number of turns. An alternating current (AC) passes through it and magnetic flux is generated within the conductor. The magnetic flux generated induces eddy currents that enable the heating and subsequently the melting process in the crucible. The shell is the outer part of the furnace. This houses the crucible and the inductor coils, and has higher thermal capacity. It is made of rectangular parallelepiped with low carbon steel plate and joined at the corners by edge carriers from angular pieces and strips of non-magnetic metal. The cooling system is normally a through one way flow system with the tubular copper coils connected to water source through flexible rubber hoses. The cooling process is important because the circuit of the furnace appears resistive, and the real power is not only consumed in the charged material but also in the resistance of the coil. This coil loss as well as the loss...

Silica Refractories

Silica Refractories Silica refractories were first produced in United Kingdom in 1822 from Ganister (caboniferous sandstone) or from so called Dinas sand. Silica occurs in a variety of crystalline modifications, e.g. quartz, tridymite, and cristobalite and also as an under-cooled melt called quartz glass. The crystalline modifications each have a high and low temperature forms which can transform reversibly. The crystal structure of the individual SiO2 modifications can differ widely, so that distinct density changes occur during transformation. This is of great importance during heating and cooling because of the change in the volume. Quartz requires the smallest volume and the quartz glass the largest. During firing above approximately 900 deg C, quartz transforms into the other modifications and melt completely at 1725 deg C. During slow cooling , reversible volume decreases take place  which are a result of the spontaneous transformation of the crystal structure from the high to the low temperature modification (Fig 1). The reversible and irreversible volume effects can cause considerable stress within the refractory brick structure. Fig 1 Calculated volume and density changes Production of silica refractories The silica refractories are manufactured as multiple asymmetric shapes, which are normally keyed or interlocked with each other by means of tongues and grooves. It is the objective of the manufacturer of silica refractory bricks to select the raw materials and the firing process in such a manner that the degree of quartz transformation is suitable for the intended application of the brick. The raw material for silica brick is naturally occurring quartzite which must meet certain requirements in order to achieve optimum brick properties. If refractoriness or thermal expansion under load (creep) are the main requirements, a quartzite of high chemical purity must be selected. Raw materials for volume stable products...