On the electron beam (EB) welding process for thick plates, crater treatment to avoid weld defects at the end part of weld bead is one of the most important and very difficult technical problem to overcome.
Generally the crater treatment in EB welding is done by the gradual decrease of the beam current, but in a plate of the thickness more than 50 mm, weld defects such as porosities tend to remain at the crater treatment area, where the electron beam does not penetrate through out the plate thickness.
This type of defects appears mostly at the tip of the penetration, because, in this area evaporated metal gas cannot be discharged due to the insufficient flow of molten metal.
Authors studied various methods of crater treatment of EB welding process for 100mm thick steel plates for pressure vessels.
It was confirmed through the studies that porosities can be prevented by the application of double electron beam oscillations (circular and linear direction) with cirtain frequencies and amplitudes.
