Why is the welded joint the weak link in the welded structure?

Welded joints are the weakest link in welded structures. The main causes include the following six factors:

Microstructural changes in the heat-affected zone

High welding temperatures can cause grain coarsening in the adjacent areas of the parent material, resulting in decreased plasticity and toughness.

Residual stress

Tensile stresses generated during welding are difficult to completely eliminate, reducing the load-bearing capacity of the joint.

Geometric discontinuities

Sudden cross-sectional changes at the weld toe and weld root can easily lead to stress concentrations.

Risk of process defects

Defects such as porosity, slag inclusions, lack of fusion, and cracks may occur during welding, directly weakening the structural strength.

Dissimilar material joining issues

Electrochemical corrosion-sensitive areas may form at the joints of dissimilar materials, reducing the durability of the joint.

Different strength matching

The weld metal strength may not match that of the parent material, affecting the overall structure's ability to deform in a coordinated manner.