 Hello friends, myself Dr. Narendra Kartikar, Assistant Professor, Department of Mechanical Engineering, Valachandra Institute of Technology, Solapur. Now, we are going to discuss about the study of arc welding. At the end of this lecture, rather session, student will be able to understand the elements in arc welding setup, process and also know where to apply it. The content for this particular discussion as follow, introduction, introduction to joining processes, advantages and disadvantages of welding, arc welding, MMW, manual metal arc welding setup and description, advantages and disadvantages of arc welding, application of arc welding. Then as we know to produce any single element in a individual form or to make an assembly we require to choose one of the basic manufacturing process like casting, metal forming, joining processes or metal cutting processes. As far as possible, suppose we want to make an assembly we require to go with the joining processes rather welding processes itself. Joining or welding process is nothing but to make the permanent kind of bond between more than two elements together by the means of following parameters, heat energy, filler material, flux material and pressure. Out of these four parameters may all four parameters or few of them are used as per the particular type of welding process to fulfill the joint requirement. When we talking about joining methods, welding process, why to go with the welding here some of the advantages are, welding provides a permanent joint, welding joint can be stronger than the parent material if a proper filler metal is used, a good weld is as strong as the base metal itself. Portable welding equipment is not very costly, portable welding equipments are available and fulfill the particular requirement itself. If we go further advantages of welding processes, welding can be mechanized most efficient way to joining the metal is nothing but the welding process. Lowest cost joining method of permanent type is a welding process, it provides the design flexibility also. As we had discussed or seen some of the advantages, similarly some of the disadvantages of welding processes are here. Welding gives out harmful radiations in the form of light fumes or it may spatters the hot molten metal spots. A skilled welder is a must to produce a good welding job. Welding heat produces the metallurgical changes in the base metal, welded joint for many reasons needs the stress relief heat treatment post kind of operations. If we go to further extension discussion on the disadvantages of welding, it is need high energy causing dangers to the base metal as well as to the human being. Not convenient for disassembly, defects may be produced over there which are very difficult to remove the same. At this stage of this session, are you able to recall or share some of the parts where different geometries are welded with any type of welding processes. Enlist such welded parts which you had seen earlier anywhere in real time. I hope you had enlisted the parts or the assembly which you had seen the form with the means of welding joints. Let us go with the introduction of arc welding. Arc welding process is a fusion method of welding that utilizes the high intensity of arc generated by the flow of current to melt the work pieces. A solid continuous joint is formed upon cooling. This is the conceptual figure which is self-explanatory about an arc welding. You can see the base metal is going to be there where the gaseous shield is made because of the particular burning of flux which is coated normally on the electrode. The creator is formed over there because of the an arc produced in between the torque tip and the base metal. After solidification, you can see over here the slag layer as well as the solidified molten mixture layer going to the principle of arc welding. The source of heat for arc welding process is an electric arc generated between two electrically conducting material. One of the work piece material called electrode is connected to one pole of the particularly electric circuit while the other work piece which forms the second conducting material is connected to the other pole of the circuit. When the tip of electrode material is brought into the contact with the work piece material and nominally, momentarily separated by small distance of 2 to 4 millimeter and arc can be generated, the electrical energy is thus converted to the heat energy. The high heat of an arc melts the edges of the work pieces. Coalescence takes place where the molten metal of one work piece combines with the molten metal of the other work piece. The electrode material can be either non-consumable material or consumable material whereas the consumable electrode which is made up of same material as that of the work piece metal helps to strike the arc and at the same time melts get consumed and combines with the molten metal of the work piece to form an weld. Types of arc welding, this is the exhaustive list of arc welding. We have to discuss one of the type of arc welding flux shielded metal arc welding also called as manual metal arc welding short forms MMAW, SMAW. It is an arc welding process wherein coalescence is produced by heating the work piece with an electric arc setup between a flux coated electrode and the work piece. The flux covering decomposes due to the arc heated and performs many functions like arc stability, weld metal protection and so on. The electrode itself melts and supplies the necessarily the filler material to the weld pool. This is the flux shielded metal arc welding setup where you can see that electric circuit rather it is also called as the welding circuit which consists the few of the elements like electrode holder, electrode the base metal AC or DC power supply. You can see here the electrode, air column, gaseous shield, solidified flux material in the form of slag, weld deposited metal called as the weld bead, the work piece the arc crater is also seen over here. It required for welding is obtained from an arc struck between the coated electrode and the work piece arc temperature thus arc heat can be increased or decreased by employing higher or lower arc current. Material droplets are transferred from the electrode to the job through an arc they are deposited along the joint to be welded. The flux coating metals produces a gaseous shield and slag to prevent the atmospheric contamination of the molten metal to the particularly atmosphere. Striking the arc in manual metal arc welding arc between the electrode and the work piece is generally struck either by momentarily touching the electrode with the work piece and taking it a predetermined distance away from the work piece by wrist movement or by scratching electrode on the job in the arc of the circle. For holder it can hold the electrode at various angle and energizes it at the same time. Welding the joint once arc has been established and arc length is adjusted the electrode is inclined to an angle approximately 20 degrees with the vertical to achieve comparatively deeper penetration electrode angle with the vertical is further reduced. The electrode is progressed along the joint at a constant speed it is lowered at the same time at a high at a rate at which it is melting. Welding equipment is your DC welding supply electrode holder and welding cables. Welding electrodes AC transformer DC generator or rectifier can be employed for welding with a covered electrode. A transformer may be operated from mains or a single phase two phase or three phase A typical specification of the transformer may be as follows current range from particularly up to 600 amperes open circuit voltage 70 to 100 volt itself. Some of the advantages of manual metal arc welding or shielded metal arc welding is the simple most among all the arc welding process equipment can be portable and the cost is fairly low. A big range of metal and their alloy can be welded welding can be carried out in any position with highest weld quality. Some of the disadvantages because of limited length of each electrode and brittle flux coating on it mechanization is bit difficult. The process uses stick electrode and the city slower as compared to the MIG welding because of flux coating electrode the chances of slag entrapment and the other related defects are more as compared to the TIG or MIG welding. Some of the applications of MMAW or SMAW today almost all commonly employed metal and their alloys can be welded by this process air receiver tank boiler pressure vessels ship building pipes and penstock joints building and bridges construction atomative and aircraft industries etcetera. Some of the references for this particular discussion and presentation introduction to basic manufacturing process and workshop technology Rajendra Singh a textbook of workshop technology manufacturing processes Khurmigopta NPTEL study material and so on.