Local Tungsten Inclusion
Local tungsten inclusions are unmelted tungsten electrode particles in the weld metal, caused by direct contact with the molten pool. On X-ray, they appear as bright spots.
Physical-chemical mechanism of action
Tungsten electrodes consist of tungsten and other metals such as cobalt or nickel. During TIG welding, these electrodes can come into direct contact with the molten pool, leading to unmelted particles. These remain embedded in the weld metal and appear as bright spots under X-ray inspection.
Metallurgical relevance & risks in welding
Local tungsten inclusions can impair the mechanical properties of the weld, especially its toughness and fatigue life. They can also lead to cracks or hot cracks, especially if they are located in critical areas. Furthermore, they can contaminate the microstructure and affect thermal conductivity.
Shop practice & instructions
To avoid local tungsten inclusions, electrodes and the molten pool should be cleaned regularly. Use a clean melt and ensure the correct distance between electrode and workpiece. If inclusions are suspected, perform an X-ray inspection to determine the number and location of the inclusions.