Abstract: The mechanism of ultrasonic seam welding of copper plates and tubes for collecting solar energy was investigated. It is concluded that welding seam is formed under the jointly action of three factors： atoms permeating on the welding interface, melt welding between contacting apexes and interlock in the welding seam interface. In addition, effects of welding specimen hardness and parameters on tensile strength of welding were studied by experiments．

Key words: ultrasonic seam welding, friction vibration, atoms permeating