Root sag of the weld metal
The weld root overhang is the distance between the edge of the weld metal and the actual weld edge. Excessive overhang can cause stresses that may lead to cracking.
Physical-Chemical Mechanism of Action
The root gap is the area of the weld joint that is not directly covered by the weld. This area remains unchanged and can absorb stresses when the weld metal expands or contracts differently.
Metallurgical Relevance & Welding Risks
A large root gap can lead to stress concentrations that may cause cracking in the weld. This is especially dangerous with stiff steels or under high mechanical loads. The stresses can also promote corrosion.
Workshop Practice & Instructions
To minimize the root gap, position the workpieces so that the gap edges are in direct contact with the weld edges. This can be achieved by proper positioning and clamping. For special applications or high-tensile steels, it's advisable to keep the root gap to less than 2 mm.