In the context of visual testing, what signifies lack of fusion in weldments?

Lack of fusion in weldments refers to a failure of the welding process to completely bond the materials being joined. This is most commonly identified by improperly fused materials, where there is an insufficient connection between the weld metal and the base material or between layers of weld metal. This incomplete fusion can lead to weak points in the weld, which can significantly affect the structural integrity and performance of the welded component.

Improper fusion may arise from various factors, including incorrect welding parameters, lack of proper joint preparation, or improper technique during the welding process. When materials do not properly merge at the interface, it creates a potential for defects, which can compromise the strength and overall quality of the weld.

Other factors like excessive heat treatment, surface porosity, and inadequate material thickness can contribute to welding issues but do not specifically signify lack of fusion. Excessive heat treatment could pertain to changes in material properties, while surface porosity relates to gas entrapment that can weaken a weld, and inadequate material thickness affects the weld's ability to withstand stresses, but these do not directly indicate a failure of fusion. Therefore, recognizing improperly fused materials directly highlights the concern of lack of fusion in welded structures.