Heat Transfer in Arc Welding

Abstract

Arc welding uses an arc plasma between two metal electrodes to transfer concentrated energy to one of the electrodes, the workpiece, which consists of the metal components to be joined. This leads to partial melting of the workpiece, forming a weld pool. Heat transfer in arc welding is complex, involving four phases of matter (plasma, gas, liquid, and solid) and their interactions. After a brief introduction to the different types of arc welding, the chapter focuses on two of the most important: metal inert-gas/metal active-gas (MIG/MAG) welding and tungsten inert-gas (TIG) welding. Heat transfer in the arc column, between the arc and the electrodes, by droplets of molten metal from the upper electrode, in the molten metal weld pool, and in the solid metal are all considered in detail. The efficiency of the arc welding process is also analyzed. Throughout the chapter, the equations describing the heat transfer processes are presented, and their physical significance is discussed. Detailed consideration is given to the influence of different welding gases and the presence of metal vapor on the heat transfer in the arc column.