The document discusses several advanced welding techniques: friction welding, explosive welding, laser beam welding, plasma arc welding, resistance welding, and thermite welding. Friction welding uses mechanical friction to generate heat and join metals without filler. Explosive welding accelerates one metal at high speed into another. Laser beam welding uses a concentrated laser heat source to make narrow, deep welds. Plasma arc welding uses an electric arc and constricted plasma to reach very high temperatures. Resistance welding generates heat through electrical resistance to join metal sheets. Thermite welding uses a thermite reaction to melt and join metals. These techniques are used in automotive, shipbuilding, aerospace and other industries.