 Hello friends, myself Dr. Narendra Kartikar, Assistant Professor, Department of Mechanical Engineering, Valachandra Institute of Technology, Solarpur. Now we are going to discuss about the study of furnaces part 2. At the end of this lecture or the session, students will be able to understand the construction and working of arc furnace and induction furnace. The contained flow for this discussion, introduction, electric arc furnace, induction furnace, coreless induction furnace and channel induction furnace. Let us have a look on the particular image shown on the screen, the furnace. It is a nothing but it will convert the solid metal into the molten state itself by the addition of heat energy over there. Electric arc furnace. The electric arc furnace normally uses three vertical carbon rods as electrodes for producing arcs, striking onto the charge and heating it to the required temperature. The diagram shown on the screen is more self-explanatory, where the three electrodes are present and typically an arc is shown in between the electrode tip and the slag. The charging door, spout and cover is typically also shown over there. More elaboratively, let us discuss with the help of this particular diagram. The electrodes are supported or inserted through the roof, which is removable. You can see the molten slag is present below which the molten steel is there. Repractory lining is enclosed to that particular electric arc furnace itself. Tapping spout is used to take out the molten metal directly into the ladle. To take out easily or pouring the molten metal into the ladle, tilting mechanism is shown over there. An electric arc furnace used for steel making consists of a refractory lining vessel usually water cooled in large sizes covered with a retractable roof and through which one or more graphite electrodes enter the furnace. The furnace primarily split into the three sections, the shell, which consists of sidewalls and lower steel bowl, the hearth, which consists of refractory that lines the lower bowl, the roof, which may be refractory lining for water cooled and can be shaped as a section of sphere. The roof also supports the refractory delta in its center through which one or more graphite electrode enters. Heat energy source for this furnace can be described as a furnace heating charge material by the way of an electric arc. It can have temperature rising up to 1800 degrees Celsius. The arc forms between the charge material and the electrodes. The charge is heated both by current passing through the charge and by the radiant energy evolved by the electric arc. Furnace may be categorized as direct or indirect type as shown in the figure. Both types of units are suited for melting of high melting point alloys such as steels. The electrodes of direct arc furnace are automatically raised and lowered by positioning system. Carbon electrodes are present over there in the left side type that is a direct arc type and arc is developed between the tip of electrode and the metal. Whereas, in the right side diagram indirect type that means an arc is generated developed in between the two distinct electrode tip itself. Advantage is the use of electric arc furnace allows steel to be made from 100% cap metal feedstock commonly known as cold ferrous feed to emphasize the fact that for an electric arc furnace scrap is regulated feed material. The primary benefit of this is large reduction in specific energy. Another benefit is flexibility while blast furnace cannot have vary their production by much and are very stopped can be rapidly started and stopped allowing the steel mill to vary production according to the demand. Some of the disadvantage electric furnace have more cost to run than a gas furnace. It may have be more expensive to repair than oil and gas furnace. Induction furnace uses alternating current passing through a coil to develop magnetic field in a metal induced current causes rapid heating and melting. Electric force field also causes mixing action in liquid metal. Since metal does not contact heating element environment can be closely controlled to produce a molten metal of high quality and purity. Melting steel cast iron aluminium alloys are common application in foundry work. You can see the figure shown on the screen which is self-explanatory for induction furnace. Molten metal is shown arrows indicates mixing action. The cover is present as well as the refractory material is shown which enclose the molten metal. The copper induction coils are in a wound condition to that refractory material. It is a type of melting furnace that uses electric current to melt the metal. These are the ideal for melting and allowing a wide variety of metal with minimum melt losses however little refining of the metal is possible. Principle of induction furnace principle is the induction heating. Induction heating is the form of non-contact heating for conductive material. The principle of induction heating is mainly based on two well-known physical phenomena electromagnetic induction the Joule effect. At this stage of this session are you able to recall share some of about electromagnetic induction and Joule effect which you might have learned earlier just enlist few of the points. Let us move for the induction furnace. Electromagnetic induction the energy transferred to the object to be heated occurs by means of electromagnetic induction. Any electrically conductive material placed in a variable magnetic field is the site of induced electric current called eddy currents which will eventually lead to Joule heating. You can see some of the particular images as well as conceptual diagrams shown on the screen. Joule heating also known as a ohmic heating and resistive heating is the process by which the passage of an electric current through a conductor releases heat. The heat produces is proportional to the square of the current multiplied by the electric resistance of the wire. You can see the three stage image is shown over there because of heat evolution how particularly the raw material or the base metal changes its color. Induction heating relies on the unique characteristics of radio frequency energy that pro that portion of the electromagnetic spectrum below infrared and microwave energy. Since heat is transferred to the product via electromagnetic waves the part never comes into the direct contact with any flame. The inductor itself does not get hot and there is no product contamination at all. Induction heating is a rapidly non-polluting heating. The induction coil is cooled to the touch. The heat that builds up in the coil is constantly cooled with a circulating water. Some of the images of actual induction furnaces are shown over here. Construction there are many different designs for electric induction furnaces but they all center around a basic idea. Coraless induction furnace type of induction furnace two main type corals and channel. The heart of corals induction furnace is the coil which consists of hollow section of heavy duty high conductivity copper tubing which is bound into a helical coil. Coil shape is contained within a steel shell to protect it from overheating coil is a water cooled. The crucible is formed by ramming a granular refractory between the coil and the hollow internal. It is commonly used to melt all grades of steel and ions as well as many nonferrous alloys. Coraless induction furnace is looking like this. The particular parts are shown individually. Channel induction furnace it consists of refractory lining steel shell which contains the molten metal attached to the steel shell and connected by a throat is an induction unit which forms the melting component of the furnace. The induction unit consists of an ion core in the form of ring around which a primary induction coil is wound. This assembly forms a simple transformer in which the molten metal loops compresses the secondary component. The heat generated within the loop causes the metal to circulate into the main well of the furnace. The circulation of molten metal effect useful stirring action in the melt. The channel induction furnace looking like this. Overall advantages and limitations of induction furnaces are higher yield, faster start-up, flexibility, neutral stirring, cleaner melting, compact installation, reduced refractory and so on. Whereas some of the disadvantages are refining in induction furnaces is not an intensive or effective as in electric arc furnace. The life of refractory lining is low as compared to electric arc furnace. Removal of S&P is limited so selection of chargers with less impurity is to be there. Some of the references for these discussions are as follows. Thank you.