Production of Steel in Induction Furnace May08

Production of Steel in Induction Furnace...

Production of Steel in Induction Furnace Medium frequency coreless induction furnace is generally used for the production of steel in the steel melting shops of low capacity. The induction furnace is equipped with a converter for producing the necessary medium frequency from the 50 Hz frequency of the power supply. For this, a direct voltage is produced in a rectifier, and is fed to the inverter via a smoothing choke, and a medium frequency voltage is produced in the inverter with the aid of compensating capacitors and the inductivity of the furnace coil. The regulation of the converter is carried out by the built-in control electronics. The control of the furnace is carried out using the devices in the operating cabinet and if necessary with the aid of a processor. A transformer is used for the energy supply. The furnace transformer is connected to the power supply network. The transformer converts the supply voltage to the voltage required for the operation of the furnace which is generally 770 V for medium frequency induction furnace. The transformer is usually equipped with the built-in monitoring devices such as thermometers, oil filling level monitoring, Buchholz relays and air de-humidifiers. The smelting is carried out in the refractory crucible made normally with either acidic (silica based) or neutral (alumina based) monolithic refractories. The crucible is heated by an induction furnace coil surrounding the crucible. Making of a heat in an induction furnace consists of certain cyclic activities. These activities are known as ‘heat cycle’ or ‘production cycle’. A heat cycle has two components namely (i) melt cycle, and (ii) non-production cycle. The melt cycle is the period when maximum power is continuously applied to the furnace and the charge is added. The non-production cycle is when no or...

Refractory Lining of Coreless Induction Furnace...

Refractory Lining of Coreless Induction Furnace In steel melting shops of low capacities, induction furnace is preferred as a convenient melting unit because of its high efficiency, low energy consumption, easy operational control, and good performance with various kinds of steel scrap. The induction furnace is an electrical furnace in which the heat is applied by induction heating of a conductive medium (usually steel scrap) in a crucible placed in a water-cooled alternating current solenoid coil. Induction coil is required to be protected from the liquid steel  by isolation material called refractory. A coreless induction furnace has a non-conductive refractory crucible, surrounded by a coil of copper tube.  Cross-section of induction furnace showing refractory lining is at Fig 1. Fig 1 Cross-section of induction furnace showing refractory lining The refractory lining practice for a particular induction furnace depends upon the capacity and design of the furnace, operation practice adopted during making of a heat, and furnace output. For successful and consistent performance of the lining, the important aspects are (i) use of proper grade and quality of the lining material, (ii) careful and systematic lining practice, and (iii) consistency in working conditions.  Refractory lining is consumable material which gets damaged during the operation of the induction furnace. The number of heats the lining last is known as lining life. When a certain amount of damage occurs, induction furnace operation is to be interrupted for repair or replacement of the refractory lining. Both of these activities increase the furnace downtime. Refractory lining is the important part of induction furnace since the furnace performance is directly related to the performance of the refractory lining. Well stabilized refractory lining results in smooth working of furnace, optimum output and better metallurgical control. The lining practice best suited to...

Impact of Workplace Environment on Employee Performance...

Impact of Workplace Environment on Employee Performance Employees are very important assets in an organization. A good organization is one which takes care of its employees. This is often done by paying attention to their workplace environment. This is because the employees spend substantial part of the time of their lives at the workplace while carrying out their work. Hence, workplace environment influences their cognitive and emotional states, concentration, behaviour, actions, and abilities. It plays an important role in the employees’ engagement as well as in their performance. In fact, workplace environment has a big contribution for the organization in maintaining a high level of employees’ productivity and hence the organizational productivity. Workplace environment can be anything which exists around the employees where they work and which affect how they carry out their work. It consists of both external and internal conditions which can influence the working spirit and hence, reflect in their performance at work. There exists a strong interaction between employees’ performance and physical workplace environment. The physical environment at work is critical to employees’ performance, satisfaction, social relations and health. The environmental conditions at the workplace are important factors which has an influence on the employees’ morale and job satisfaction and hence their performance. Workplace environment and productivity are often perceived as two opposites by the managements in some of the organizations. This is because, the managements of such organizations consider workplace environment as an extra, resource-consuming, nonproductive activity, which they dislike because of the lack of production stemming from it. They believe that the productivity enhancement of the employees can be achieved by enhancing the employees’ skills. Such managements are ignorant of the fact that majority of the productivity problems reside in the workplace environment in which the employees operate....

Rolling of steel and major equipment in a Cross-country Rolling Mill Apr25

Rolling of steel and major equipment in a Cross-country Rolling Mill...

Rolling of steel and major equipment in a Cross-country Rolling Mill Most of the steel products are rolled from the cast products from continuous casting machine through a series of rolling and finishing operations. The process is called simple rolling, when two rolls of equal diameter and with axis lying in same plane rotate in opposite direction with same rotational speed, and the material being rolled is homogeneous in its mechanical properties and is acted upon only by the forces from the rolls. Rolling is the most important metal forming process. More than 95 % of ferrous and non-ferrous metals and alloys are processed to their usable shapes by rolling. Usable shapes of rolled metals are plate, sheet, strip, foil, and different sections like rail, beam, channel, angle, bar, rod, and seamless pipe etc. Two common rolling processes are hot rolling and cold rolling. The primary function of the hot rolling mill is to reheat ingot/ billet/bloom/slab (steel rolling stock) close to soaking temperature point, and then roll it to thinner and longer through successive rolling mill stands driven by electric motors. The steel rolling stock heated up to around 1,250 deg C in reheating furnace, using a solid/liquid/gaseous fuel as the primary energy source. The heated steel rolling stock is rolled in a roughing mill in number of passes where its size is reduced and its length is increased while its shape is modified. This process continues in intermediate and finishing mills also in a number of passes in each of the mill. As rolling proceeds, the length of the product increases, the size of the material reduces and the speed increases after every stand and is the speed is the highest at the end. In hot rolling, the material is rolled at...

Solid Pollutants and Solid Pollution...

Solid Pollutants and Solid Pollution Solid Pollutants are more popularly known as solid wastes. The types and quantity of solid pollutants generated in iron and steel industry differ from plant to plant. Thus, a steel plant based on direct reduced iron – electric furnace (electric arc furnace or induction furnace) route generates different types and quantities of solid wastes than the integrated steel plant based on the blast furnace – basic oxygen furnace route. The solid wastes generated in iron and steel industry can be broadly categorized as (i) process solid wastes, and (ii) non-process solid wastes. Examples of process solid wastes are slag, dust, sludge, scrap, refractories, scale, muck, and debris etc. Examples of non-process waste materials are rubber, packing materials, electric wires, plastics and glass, and office and canteen wastes, etc.  Solid waste materials are usually generated in mixed condition which means that during generation, one solid waste material gets contaminated with other waste material. These waste materials are to be segregated for their recycling and reuse.  There are two types of waste streams which generates solid wastes. One stream is related to the production process, which also includes the waste from laboratories and sludge from effluent treatment plants. The second solid waste stream is due to the maintenance of offices and canteens.   The type and quantity of solid wastes’ generation depends on production process and the production technology employed. The quantity of solid waste generation is mainly dependent on two factors namely (i) the size of production unit, and (ii) efficiency of the technology. The solid wastes generated of iron and steel industry are of two types, i.e., ferruginous wastes and non-ferruginous wastes (Fig 1). The major ferruginous wastes are iron bearing wastes and consist of iron bearing dust and fines,...