Backing strip welding

Backing strip welding is single-sided welding done over a permanent or temporary backing bar placed under the joint root, which supports the molten pool and guarantees full root fusion without back-gouging the second side. A steel backing strip is often left in place on non-critical structure; a ceramic or copper backing is removed after the pass. The method suits situations where the underside is inaccessible, such as closing seams in erected hull blocks. Class quality standards limit its use in fatigue-sensitive details because the unfused interface between strip and plate acts as a stress raiser at the weld root.