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Friction welding is a solid state bonding welding process, in which two pieces to be welded move or rotate relative to each other and butt under pressure. Heat is generated by friction of the contact surface, which makes the materials of the weldment penetrate each other plastically and fuse from the contact surface. This process does not require filler, welding wire and shielding gas. Friction welding technology, characterized by energy saving, material saving, high-quality, efficient and pollution-free technology, has been increasingly applied in aerospace, weapons, oil drilling, shipbuilding, automobile and machine manufacturing. Institutions.