Root face
Root face height is the unchanged, right-angled part of the joint face directly at the root. It prevents weld pool burn-through and mechanically stabilizes the root pass.
Physical-chemical mechanism of action
The root face forms a protective cavity between the root edge and the weld pool. This prevents the hot weld pool from directly hitting the root and burning through there. The mechanical stability ensures that the root remains stable during welding and no deformation or shifting occurs.
Metallurgical relevance & risks during welding
A root face that is too low can cause the weld pool to directly reach the root and burn through. This can lead to hot cracks or uneven distortion of the joint. A root face that is too high increases the risk of porosity and can impair mechanical stability.
Workshop practice & action instructions
The root face should be between 1.5 and 2 mm. For metals with high toughness or at high stress levels, a higher root face of 3 to 4 mm is recommended. Make sure the joint face is straight and unchanged to ensure optimal weld quality.