 What are Joining Processes? Joining process are the processes that are used for joining metal parts and metal fabrication work. It consists of four types A, welding, B, soldering, C, brazing and D adhesive bonding. One of the only important joining process is welding. It is classified into five important types namely gas welding, arc welding, assistance welding, solid state welding and thermochemical welding. In general, welding has a large number of advantages such as mechanizability, mere metal strength, manoeuvrability and low cost, which easily overshadows disadvantages like harmful emissions, skilled workmanship requirement etc. Welding is used in the construction of aircraft parts, automobile parts, building parts, pressure vessels, tanks, railroad equipment, ships, pipelines and pretty much everything where cheap and strong metal to metal joining is required. The first type of welding is gas welding which uses combustion heat or fuel gas mixture like oxygen and acetylene. A typical system consists of two cylinders, one with oxygen and other with acetylene. The flame of the torch is controlled by using a control valve. A filler rod is also added for increased strength. The flame reaches a temperature of 3200 degrees Celsius and thus can melt all commercial metals to form a complete bond. Gas welding has a lot of advantages like mobility, low cost, self-sufficiency and a myriad of applications but is limited by the time taken and skill required for perfect flame. Surage of gases, health problems etc. The second type of welding is arc welding. Here welding heat is obtained from an electric arc between an electrode and the workpiece. The temperature ranges from 6000 degree to 7000 degree Celsius. Arc welding contains three important welding types namely first submerged arc welding in which the arc electrode is hidden under a blanket of flux. The continuously fed bay metal melts and acts as a filler rod. Advantages include high welding speed and smooth weld finish. Disadvantages include flux contamination. Second comes tungsten in a glass welding or TIG welding. This is an arc welding process where coalescence is produced by heating the workpiece within an electric arc struck between tungsten electrode and workpiece. Advantages include better control on welding process with a drawback of high cost equipment. Third in line is metal inert gas or MIG welding. Here too coalescence is achieved with a metal electrode. Advantages include faster production speed, deep penetration with a compromise in complexity. Next in welding process is resistance welding. Here coalescence is produced by heat obtained from resistance offered by the workpiece to flow off electric current in a circuit of which the workpiece is apart. The electrodes are mostly made up of copper alloys. Advantages include high rate of production, less scale requirement but is limited by high equipment cost and special surface preparation requirement. The fourth type of welding is solid-state welding. Here coalescence is produced by the heat obtained from mechanically induced sliding motion between rubbing surfaces. Advantages include single operation, less time requirement, no smoke with a delimit on dimension of workpiece. Fifth and last is thermal chemical or thermite welding. Here coalescence is achieved by heating with superheated liquid metal and slag resulting from chemical reaction between metal oxide and aluminium, leading to an exothermic reaction. Advantages include no electricity requirement but is only applicable for ferrous metal parts of heavy cross sections. Weld joints can be mainly classified as lab of fillet joint, butt joint, head joint, a joint and corner joint. Weld abilities defines the capacity of metal to be welded under fabrication conditions, imposed into a specific and suitably designed structure and to perform satisfactorily in the structure. The last part in welding is welding defects, namely undercut, cracks, porosity, slag inculsions and the lack of fusion. Their main causes being improper welding, base metal and also wrong welding procedures. The second type of joining process is adhesive bonding, which is the process of joining materials by using adhesives. Adhesives used are mainly thermo-plastic or thermositing adhesives. Advantages include high joint strength, less localized stress concentration and low cost but is limited to the temperature below 177 degree Celsius. Due to its ease of use, it is used primarily in all industrial and domestic applications. Third type of joining process is soldering, in which coalescence is produced by heating the rod to a suitable temperature and by using a filler metal with a melting point below 427 degree Celsius. It is used widely in the semiconductor industry due to the simplicity and low cost. The fourth type of joining process is bracing. Here, metallic parts are joined using non-ferrous filler metal and is hence used in areas like pipes, heat exchangers, etc. The fifth and the final type of joining process is riveting, which is a permanent fastening method. There are five basic types of rivet heads, namely snap or cup head, pan head, countersunk head, half countersunk head and conical head. Rivets offer almost no stress on the workpiece due to the absence of heat and hence require almost no skill but require high amounts of cover place to support the rivet. Hence comes the end of the quick revision of joining processes. Finally, it's time for this episode's question. What do you mean by coalescence? Also, it's time to answer our last episode's question. What are MTMs? MTMs or multi-tasking machines are CNC machines with many axes that combine turning, milling, grinding and material handling into one highly automated machine tool. So like, subscribe and comment with your feedback to help us make better videos. Thanks for watching. In the next episode of Mechanical Engineering in Cedars, find out what powder metallurgy is.