 Hello everyone, I am Chandrakant Rathod, working as Assistant Professor in Mechanical Engineering Department, Waltham District of Technology, Solapur. Today, we are going to start a new topic that is Introduction to Welding and its process. At the end of today's lecture, you are able to understand what is welding process and its different types of joining process. Coming to the content, the following topic will be discussed in the video lecture. Definition of welding, classification of welding, welding terminologies, working principles, application of welding, advantages and limitations of welding process. Now we are going to start the definition of welding process. Before we define the welding in simple term, we can state that the following point about the welding process is, welding is a metal joining process. It joins to metal piece to produce a single metal piece. It creates permanent joints. Welding metal joining is basically a thermal process, hence it is essential. Welding process is possible both in ferrous and non-ferrous metals. The welding is a permanent joining process in which two metal pieces are joined together to form a single piece. It is also defined as a process in which two metal pieces similar or dissimilar join together by heating them to a temperature higher enough to fuse the metal with or without the application of pressure and with or without the use of filler metals. Coming to the classification of welding process, there are more than 30 types of welding methods are used in the engineering industry. Hence, the welding methods can be classified based on various factors or bases. The two important bases of classification of welding process are as follows. First one is source of heat, second one is interaction of weld mates. In general, the different types of welding process can be classified as follows. First one is gas welding. In that one, oxyhydrogen welding, air acylene welding, then coming to the second type that is arc welding. In that one, metal arc welding, flux shield metal arc welding, inert gas welding, submerged arc welding, plasma arc welding. So coming to the third type, electrical resistance welding. In that one, spot welding, projection welding, seam welding, butt welding. So coming to the solid states welding, friction welding, ultrasonic welding, diffusion welding, cold welding, and force welding. Then coming to the next type that is thermal chemical welding. In that one, thermist welding, automatic hydrogen welding. Then next, radiant energy welding, electrical beam welding, laser beam welding, etc. Then last type is soldering and browsing. Now pause the video. Spot welding is subtype of which welding process? I think you have written the answer. Spot welding which comes under the electrical resistance welding process. So coming to the weld terminology. So before we study the various welding process, it is essential to understand the term involved in the welding process. The important terminology used in welding process are as follows. First one is weld bead, weld metal, base metal, filler metal, heat affected dune, butt welding, weld profile and tack welding. So coming to the weld bead, it is the solidified pole of metal that includes a part of the base metal and majority of the filler metal. In fact, it is alloy of the base metals and filler metals which is stronger than the base metals. So coming to the weld metal, the alloy compressing the filler and base metal and forms the weld bead is called the weld metal. There are two base metal piece that are to be joined by the welding. So coming to the filler metal, it is the metal used to melt and forms the joint with the base metals. They are mostly in the form of electrode or filler rods. So coming to the flux, it is a chemical mixture in the form of coating on the electrode or powder form that melts and forms the layer on the molten weld metal pole. So coming to the heat affected dune, it is also known as HZA. It is the dune in the base metal adjacent to the weld area that has undergone microstructural changes due to the welding temperature. Coming to the butt weld, it is the weld produced by keeping two base metals side by side. Well, coming to the weld profile, it is the shape of the weld bead produced. It is used to specify the quality of the weld bead and depth of weld. Coming to the tack welding, it is the temporary weld joint made on the weld line to keep the base metals intact. Generally tack weldings are made at two or more point depending upon the weld joint length. So coming to the working principle of the welding process. So you can see the three diagrams. First one is the weld formation, second one is the cross section of welding and third one is the arrangement of welding process. So in the first figure, you will going to see two base metals are there and we have to prepare the edge preparation and electrode is placed on that one and high temperature heat is produced in between the two base metals and hence the weld bead is produced. In the second diagram, you will going to see that the cross sections of the two metal there the weld profile is formed and in the third diagram you will going to see the arrangement of the welding process. So you can see the welding weld table on that one, we have placed the two base metals and electrode is connected there and main supply is given to the transformer and we will going to convert that into AC into DC and required amount of power is taken to the electrode that is 100 ampere to 1000 ampere. So now we will going to see the step by step procedure for the working principle. The basic principle of welding process involves joining two base metals by allowing fusion or diffusion solid state. In fusion welding, when the two base metals heated to their fusion temperature both of them join at the fused area and forms the strong bead bond after the solidification. This fusion and solidification can be with the base metals alone or with the addition of the filler metal. The principles of typical arc welding process is as follows. It compresses two base metals that is weld made. The edge of the base metal to be welded are prepared to make the good weld joint. The base metals are kept on a weld table, the electrode is held in a holder, the transformer is set to proper current and voltage. So coming to the next point, the electrode is selected to match the base metal composition. The electrode is brought nearer to the metal. Once the stable arc is produced, the electrode holder is gradually moved forward with the formation of weld bead. Then electrode is withdrawn and finally the slug layer is removed from the weld work piece. So coming to the application of the welding process. In engineering works, there are many fabrication operations that involves welding operations are joining and fabrication of new metal part, repair of previously fabricated parts that are damaged during the service and it is also used in aerospace industries. It is used in the automotive industry. It is also used in railway industry and also it is used in the bridges and civil construction industries and it is also used in boiler industries to produce the vessels and boilers. It is used in the transportation industries. It is also used in ship construction. So coming to the advantages and limitations of welding. First we will going to discuss the advantages. A good welding will be stronger than the parent's metal. The convenient design change can be made with the welding. It is a faster fabrication and manufacturing process. Welding is generally applicable to all the metals and alloys. Many difficult shape can be produced by welding process. Most suitable process to carry out anywhere and in any position. Coming to the limitations of the welding process. Welding gives out harmful radiation, fumes and spatter results in distortion and induced internal stresses. Edge preparation is most must be before welding. So we have to create the edge preparation in between the two base metals and then we will going to start the joining the two base metal by giving the flux and skill labor is required for proper welding. So these are the some references which I have used for the this topic that is manufacturing technology by P N Rao that is Tata Megrahill and manufacturing process by one AC Niranjan Pooja publication. Thank you.