Description of flow of shielding gases through nozzles in MIG/MAG and TIG welding processes

The aim of the paper is to describe some of the characteristics of shielding gas flow in a welding nozzle and at the nozzle outlet. The paper considers welding nozzles used in MIG/MAG and TIG welding processes. First, problems related to shielding gas flow are discussed on the basis of the theory of potential flow which is the first step towards an analysis of flow conditions in the welding nozzle. Some structural design instructions are given related to welding nozzle profiling so that the velocity distribution of the shielding gas is kept as uniform as possible at the nozzle outlet. This prevents the occurrence of vortices and turbulent flow. Turbulent flow strongly disturbs the welding arc, resulting in poor quality of the welded joint. Then follows the calculation of the pressure drop in the welding nozzle. Finally, an analysis is given of an axially symmetric, viscous jet of shielding gas flowing into half space. Findings related to the flow of actual shielding gases, i.e. argon and CO 2 , and the anticipated shape of the outflowing gases are given.