Root Concavity Formation
Root fillet formation is a slightly recessed underside of the root pass, caused by pressure or shrinkage. It is allowed up to defined depths as long as the minimum cross-section is maintained.
Physical-Chemical Effect Mechanism
The root face forms due to the pressure of the welding arc or the shrinkage of the metal during cooling. This leads to a slightly concave underside of the root pass.
Metallurgical Relevance & Risks in Welding
Excessive root face can affect the microstructure and increase hardness, which may lead to cracks or wear issues. It is important that the minimum cross-section is not reduced to ensure a sound weld.
Workshop Practice & Instructions
The root face should be allowed up to a maximum depth of 0.5 mm. The minimum cross-section of the weld must be maintained during and after welding. If necessary, the formation can be reduced by careful cooling or suitable heat treatment.