 Hello friends, myself, Dr. Narendra Kartikar, Assistant Professor, Department of Mechanical Engineering, Valchandra Institute of Technology, Solapur. Now, we are going to see the particularly discussion on study of gas welding. At the end of this lecture rather session, student will be able to understand the elements in gas welding setup process and also know where to apply. The content for this particular discussion introduction, introduction to joining processes, advantages and disadvantages of welding, gas welding setup and description, advantage, disadvantages and applications of gas welding. As you know, let us see in the introduction, let us see in the introduction about the basic manufacturing processes and the presence of joining processes rather welding in the basic manufacturing processes. As we know to manufacture any of the element or assembly, you need to go with the any of the selection of manufacturing processes out of casting, metal forming, joining processes, metal cutting and so on. Out of these four manufacturing processes, joining processes is nothing but the joining more than two elements together to form an assembly. An assembly which is used for useful end application as defined by the designer. The particularly joining processes includes the various parameters like heat energy, filler material, flux, pressure. All these four parameters may be used simultaneously or out of these four few of them are used as per the type of welding rather joining processes. When we talk about joining more than two elements together to form an assembly that is about the welding, here some of the advantages are there. Welding provides a permanent joint. Welded joint can be stronger than the parent material if a proper filler material is used that has strength properties better than that of the parent base material and if defect less welding is done then it is a strong joint itself. A good weld is a as strong as the base metal as we had seen just now. The general welding equipment is not so very costly, portable welding equipment can fulfill the task as per the particular requirement. Here few more particularly advantages are there. If we look to some of the disadvantage of welding, welding gives out the harmful radiations in the form of light, fumes and spatters of metal spots. A skilled welder is a must to produce a good welding job itself and few more disadvantages are mentioned here. If we see few more disadvantages you can look over here. Need high energy causing produces the danger to the human being. What convenient for this assembly defects are hard to detect and if at all the defects are there it is 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 process and list such welded parts which you can which you had seen earlier anywhere in real time. Here we go. I hope that you had enlisted the particular list of the job which can be welded together. Let us go with the gas welding. One of the particularly type of gas welding will explain in further due course. Gas welding is a fusion welding process. It joins the metal using the heat of combustion of an oxygen air and the fuel gas may be acetylene, hydrogen, propane, butane, etc. The mixture of air or oxygen and one of these gas. The intense heat that is in the form of flame thus produce the particularly flame going to be melts and fuses together the edges of the parts to be welded generally with the addition of filler metal itself. Let us see few of the principles of gas welding itself. When the fuel gas and oxygen are mixed in a suitable proportion in a welding torch and ignited the flame resulting at the tip of the torch is sufficient enough to melt the edges of the workpiece metals. A solid continuous joint is formed upon cooling the two familiar fuel gases used in the gas welding are the mixture of oxygen and acetylene gas called as oxy acetylene welding process, mixture of oxygen and hydrogen gas called as oxy hydrogen welding process. Oxy acetylene welding is the most versatile and widely used gas welding process due to its high flame temperature may be go up to 3500 degree Celsius when compared to that of oxy hydrogen process which is go up to 2500 degree Celsius. Types of gas weldings are oxy acetylene welding, oxy hydrogen welding, pressure gas welding, air acetylene welding, oxy acetylene welding. Principle of operation for this particular type when acetylene is mixed with oxygen in correct proportion in the welding torch and ignited the flame resulting at the tip of the torch is sufficiently hot to melt and join the parent metal. The oxy acetylene flame reaches a temperature of about 3200 degree Celsius and thus can melt all commercial metals which during commercial metals with during commercial metals which during welding actually flow together to form a complete bond. A filler metal rod is generally added to the molten metal pool to build up the seam slightly for the greater strength. The acetylene gas welding setup you look it to the particularly setup here the two distinct cylinders are there oxygen cylinder acetylene cylinder. These two cylinder carries respectively the oxygen and acetylene gas with a specified pressure. This particular cylinder connected to the torch through the means of hose. The cylinder regulators are attached to the particular valve. The valve is connected to the each every particularly cylinder. The torch consists further gas control valves which controls the flow rate of the gas. The mixing chamber is present to the extreme end of the torch where the particular amount of oxygen and acetylene is mixed. The torch tip is the extreme end of the particular torch assembly from where the mixture of oxy acetylene comes out. Representing the particular one of the sample job is shown over here work piece with two simple rectangular plates with a two simple rectangular plates filler material rod is also shown representatively. Let us see the detailed description and operation of the gas welding. The equipment consists of two large cylinders one containing oxygen at high pressure and the other containing acetylene gas. Two pressure regulators fitted on the respective cylinder regulates or controls the pressure of the gas flowing from the cylinder to the welding torch as per the requirement. The welding torch is used to mix both oxygen and acetylene gas in a proper proportion and burn the mixture at its tip. A matchstick or a spark lighter may be used to ignite the mixture at the torch tip. As we have seen just now the temperature of the flame 3200 degree Celsius to 3500 degree Celsius. Since a slight gap usually exists between the two work pieces a filler metal is used to supply the additional material to fill the gap. The filler metal must be the same material or nearby the same chemical composition as that of the work piece material. The molten metal of the filler metal combines with the molten metal of the work piece and upon solidification form a single piece of metal. Gas is required may be used during the process it can be directly applied to the work piece or may be dipped in the filler metal. Advantages of oxyacetylene gas welding Here some of the advantages like it is probably the most versatile process it can be applied to the wide varieties of manufacturing and maintenance situation. The rate of heating and cooling is relatively slow in some cases this is an advantage. The equipment is versatile low cost and usually a portable one. The cost of maintenance of the gas welding equipment is low when compared to the some other welding processes. Disadvantages of oxyacetylene gas welding heavy sections cannot be joined economically flame temperature is less than the temperature of the arc in the arc welding process. Gas flame takes a longer time to heat up the metal than an arc in the arc welding process acetylene and oxygen gases are rather expensive. Some of the applications of oxyacetylene gas welding heavy section cannot be joined economically flame temperature is less than the temperature of an arc. Processes R Introduction to the basic manufacturing processes and workshop technology preferences Introduction to the basic manufacturing processes and workshop technology by Rajendra Singh A textbook of workshop technology manufacturing processes R S Khurmi Gupta NPTEL website and so on. Thank you.