Welding is the process of fabrication that fuses two or more parts together by the application of heat, or pressure, or both, joining as the parts cool. There are different kinds of welding processes. Welding is usually done on metals and thermoplastics. Some of the major welding techniques include forge welding, arc welding, thermochemical welding, resistance welding, and electron-beam welding. Shielded metal arc welding (SMAW) is a type of arc welding technique wherein an electric arc is struck between the metallic electrode and the work piece, and tiny globules of molten metal are transferred from the metal electrode to the weld joint. Thermochemical welding works on the principle of gas welding. In this process, heat is supplied by burning acetylene in oxygen to provide an intense, closely controlled flame. Aluminothermic (thermite) joining is another thermochemical process used for both ferrous and non-ferrous metals. This process is appropriate for joining sections with large, compact cross sections. This book details various researches that have been conducted in relation to welding. Its elaborate content will aid the readers in thoroughly understanding the subject.