The process for welding metals using ultrasonic energy is simple. The primary reason metals do not stick together is because they are covered with an oxide as a result of exposure to the atmosphere. Aluminum, for example, forms a tough oxide within microseconds when exposed to oxygen. Further complicating the joining process are normal surface contaminates such as oil or other materials. (See Figure 6.) If it were not for oxides, dirt and oil most machinery would cease to function because mating surfaces will have welded together.
Employing vibration, force and time, an ultrasonic welder forms a weld by pressing the parts to be joined together and scrubbing them against one another to break up and disperse the surface oxides and contaminates. (See Figure 7.) The resultant clean base metal surfaces are held tightly together. Crystal boundaries are brought within atomic distance of one another allowing the strong attraction of atoms across the interface to create a metallurgical bond without reaching the melt temperature of the metals being joined. (See Figure 8a and 8b.) Since ultrasonic metal welding does not depend on achieving a melt of the metals to be joined their melt temperatures and their thermal conductivity are not process factors. The entire welding process is accomplished in approximately 250 ms.
The process for welding metals using ultrasonic energy is simple. The primary reason metals do not stick together is because they are covered with an oxide as a result of exposure to the atmosphere. Aluminum, for example, forms a tough oxide within microseconds when exposed to oxygen. Further complicating the joining process are normal surface contaminates such as oil or other materials. (See Figure 6.) If it were not for oxides, dirt and oil most machinery would cease to function because mating surfaces will have welded together. 
Employing vibration, force and time, an ultrasonic welder forms a weld by pressing the parts to be joined together and scrubbing them against one another to break up and disperse the surface oxides and contaminates. (See Figure 7.) The resultant clean base metal surfaces are held tightly together. Crystal boundaries are brought within atomic distance of one another allowing the strong attraction of atoms across the interface to create a metallurgical bond without reaching the melt temperature of the metals being joined. (See Figure 8a and 8b.) Since ultrasonic metal welding does not depend on achieving a melt of the metals to be joined their melt temperatures and their thermal conductivity are not process factors. The entire welding process is accomplished in approximately 250 ms. 
