Energy efficiency in thermal joining processes

Abstract

Rising energy costs make energy efficiency a key topic of the future for different industrial production processes. Thermal joining is widely used in the production process and causes a lot of energy lost. Both weld seam and filler material have to be heated to temperatures higher than the melting point. During the process a high amount of heat conducts into the work piece. Process efficiency and decrease of the energy consumption can be achieved through decreasing of the process temperature and the weld metal volume, respectively. To achieve these goals, material and process developments have to be carried out. These can result energy savings up to 40% are established in laser and arc welding processes. Nanotechnology is an innovative means to reduce required energy for joining processes. High energy which is necessary in the joining area can be generated in milliseconds only by using nanostructured reactive foils. Furthermore, the process velocity can reach several m/s. Due to the size effect the melting temperature of nanoparticles decreases inversely proportional to the radius. Therefore Ag nanoparticles with a diameter of 10 nm melt at about 200°C which has to be compared to micro, meso or macro sized Ag particles melting at 960°C. Filler material manufacture based on this effect allows producing metallurgical joints at very low temperatures. After the joining process the size effect disappears. This means that the reflow temperature is equal to the macroscopic melting temperature. Material and process developments offer a wide variety of opportunities to reduce the energy consumption in thermal joining processes. Especially taking advantage of nano effects to decrease the process temperature and increase the process velocity has great potential for future applications.