焊接技术 Welding.pdf

Welding Dr. Sunil Jha Introduction Joining Welding, Brazing, Soldering and Adhesive bonding In these process a permanent joint between the parts is formed and cannot be separated easily Assembly usually refers to mechanical methods of fastening the parts together. Some of these methods allow easy disassembly, while others do not 1 Welding Welding is a material joining process in which two or more parts are coalesced (joined together) at their contacting surfaces by a suitable application of heat and/or pressure. In some welding process a filler material is added to facilitate coalescence. Welding is most commonly associated with metallic parts but for plastics also it is used. Types of Welding Processes Solid state welding processes Liquid state welding processes Solid / Liquid state bonding processes 2 Solid State Welding Processes In solid state welding the surfaces to be joined are brought into close proximity by: Heating the surfaces without causing melting and applying normal pressure Providing relative motion between the two surfaces and applying light normal pressure Applying high pressure without heating In these processes the materials remain in solid state and welding is achieved through the application of heat and pressure, or high pressure only Forge Welding Forge welding is the oldest method of welding in the category of solid state welding. Surfaces to be joined are heated till they are red hot and then forced together by hammering. It is a crude method of welding and quality depends upon the skill of the welder. A modern version of this type of welding is manufacture of butt-welded pi