Fillet weld convexity
The convexity of a fillet weld is the bulge of the weld surface beyond the direct line connecting the weld toes. Excessive convexity leads to unfavorable notch stresses and increases the risk of cracking.
Physicochemical mechanism of action
The fillet weld is formed by welding processes such as TIG or MIG. Convexity occurs when the weld pool takes a certain shape and bulges beyond the direct line connecting the weld toes. This can be caused by non-uniform heat input or excessive stresses during cooling.
Metallurgical relevance & risks during welding
Excessive convexity of the fillet weld can lead to increased notch stresses. These can cause cracks at the transition from the weld to the base material, especially when stresses exceed the elastic limit of the material. This can lead to hot cracks or root cracks, impairing the mechanical strength of the joint.
Workshop practice & instructions
To achieve optimal convexity, the weld should be made flat or slightly concave. This can be achieved by careful control of the heat source and cooling process. In TIG welding, it is important to ensure even heating and minimize stresses during cooling. In MIG welding, convexity can be influenced by careful selection of shielding gas and heat input. The final convexity should be between 0.1 mm and 0.3 mm to ensure a good stress balance.