焊接科学与工程专业英语 教学课件 ppt 作者 吴志生 柏艳红 黎穗琼 主编第4章.ppt

4.Other Welding Methods 其他焊接方法 　　 Refractory metals such as tungsten are often conduction welded in electronic assemblies, but require higher power than other materials. Dissimilar metal joints are commonly encountered in conduction welds where the twisting of conductors forms a mechanical support that minimizes bending of potentially brittle joints. 4.3.4 Machines CO2 laser In the case of the CO2 laser, where the resonator is filled with a N2-CO2-He gas mixture, transfer their vibrational energy to the carbon dioxide. During the transition to the lower energy level, CO2 molecules emit a radiation with a wavelength of 10.6 μm. The helium atoms, finally, lead the CO2 molecules back to their energy level. The efficiency of up to 15% is relatively high ,and the high dissipation component is the heat . 4.Other Welding Methods 其他焊接方法 　　 In dependence of the type of gas transport, laser systems are classified into longitudinal-flow and trans-verse-flow laser systems, Figures 4.25 and 4.26. With transverse-flow laser systems t than those achievable with longitudinal-flow systems he beam quality, however, is worse . Figure 4.25 Axial flow CO2 laser Figure 4.26 Cross flow CO2 laser 4.Other Welding Methods 其他焊接方法 　　 2) YAG laser In the case of solid state laser, the normally cylindrical rod serves only the purpose to pick up the laser active ions, Figure 4.27. The achieved efficiency is below 4%. Whereas the CO2 laser application is restricted, as its necessary complex mirror systems may cause radiation losses. Figure 4.27 YAG laser 4.Other Welding Methods 其他焊接方法 　　 3) Diode lasers The semiconductor or diode lasers are characterised by their mechanical robustness, high efficiency and compact design, Figure 4.28. High performance diode lasers allow the welding of metals . In material processing they are therefore particularly suitable for welding thin sheets. Figure 4.28 Diode laser 4.Other Welding Methods 其他焊接方法 　　 4.3.5 Parameters and Technol