制造技术(中英文课件16).ppt

Resistance welding（电阻焊） Welding design（焊接设计） Lesson 16 Welding design（焊接设计） Heat input（热输入） The main function of the heat that would be input into the welding joint is to melt the base metal and filler metal (if used). Bead-on-plate（堆焊焊缝） Ar: representing the area of the filler metal melted Am :representing the area of the base metal In arc welding: P=V I V ：the potential of the power source in Volts. I ： the current in Amperes Welding design（焊接设计） Though the net heat as calculated above reaches the weld joint, all of it cannot be utilised for melting since part of it would be conducted away from the joint by the base metal as reflected in the heat affected zone (HAZ) . Welding design（焊接设计） Heat flow（热流向） Heat transfer in a welded joint is a complex phenomenon involving the three dimensional movement of a heat source. ①Heat from the weld zone is transferred more to the other parts of the base metal by means of conduction（传导）. ② Similarly heat is also lost to surroundings by convection（对流） from the surface. ③ Radiation（辐射） component being relatively small except near the weld pool. Welding design（焊接设计） Distortions（变形） Angular distortion without restraint （拘束） Welding design（焊接设计） Restraining the workpieces in butt joint Control of distortion ①The most generally preferred method in the industry is using restraint. Restrained joint Welding design（焊接设计） ②One of the important ways to control the distortions is a good design of the product with minimum number of joints. ③Another method available for reducing the distortions is the preheating of the members of the weldment. ④ Welding design（焊接设计） Defects in welding（焊接缺陷） Undercut （咬边）This is generally attributed to the improper welding technique or excessive welding current. This is mainly caused by the incorrect manipulation of the