Copyright Goodheart-Willcox Co., Inc. Chapter 18 Weld Inspection and Repair 279 usually as a result of a travel speed that is too slow. The slow travel speed creates a wide weld pool with insuffi cient heat at the edges. Those edges solidify before they can melt and fuse with the base metal. Since the extent of the overlap cannot be determined by NDT, remove the entire area by grinding or routing. Use extreme care when grinding into lap joints to prevent grinding into adjacent metal and creating more problems. When the overlap material has been removed, perform a penetrant test to determine if the defect is entirely gone. Continue removing material until the penetrant test is satisfactory. If weld repair is required to satisfy crown height requirements, use low currents and suffi cient wire to match the crown with adjoining material. • Incomplete penetration on the root side of butt welds. Other types of defects can also occur on the root side of the weld, such as concave root surface, cracks, porosity, melt- through, etc. See Figure 18-31. Remove all of these areas by grinding or routing. To ensure complete removal of all defects, perform a penetrant test before repairing the weld. Since oxides form in this area during welding, clean the repair area to bright metal before rewelding. Use stringer beads and add only enough wire to build a small crown. Internal Defect Repairs Internal defects, Figure 18-32, may or may not extend to the surface and might not be found by surface inspection. They are generally found by radio- graphic and ultrasonic testing. Once the defect has been located by a radiographic test, the defect can be marked on the X-ray fi lm. The fi lm is aligned over the weld, and a punch can be used to indent the area over the defect. The next step is to determine the depth of the defect from the top and root surface using ultra- sonic testing. Routing or grinding is done from the surface nearest to the defect. Finding the defect in the weld by grinding or routing requires both skill and patience. Porosity and large areas exhibiting lack of fusion are generally easy to locate and remove. Cracks and small areas with incomplete fusion are more diffi cult to locate. The following is a suggested procedure for repairing an internal defect in a groove weld: 1. If the defect depth is known, remove metal to within approximately 1/16″ (1.6 mm) from the defect. During the metal-removal process, use a magnifying glass to inspect the ground area. If the crack is in the right plane, a light blue surface will sometimes be found at the edge of the crack. Cold lap Cold lap Incomplete fusion Incomplete fusion Figure 18-30. Fillet weld cold laps are usually located on the bottom side of the weld. Butt weld cold laps can occur on either side of the weld crown. Concave root surface Incomplete penetration Porosity, cracks Melt-through Figure 18-31. The defects shown occur on the root side of a weld.