Root Undercut
A root notch is a narrow groove at the weld root, caused by insufficient filler metal or excessive heat input. It reduces fatigue strength and can lead to cracking.
Physical-Chemical Mechanism of Action
Root notch forms when during welding there is not enough filler material (e.g., steel) available or the heat input is too high. This causes the metal area at the root not to be completely closed and a groove to form.
Metallurgical Relevance & Risks in Welding
Root notches can significantly reduce the fatigue strength of the weld because they act as notches. These notches can lead to cracks and impair the mechanical strength of the joint. Additionally, this can cause uneven load distribution and damage the microstructure around the notch.
Workshop Practice & Instructions
To avoid root notches, it is important to bring the filler material into the weld. This can be achieved by correct setting of the welding machine and welding parameters. Make sure the heat input is not too high and the metal area is completely closed. Regularly check the filler material flow and correct the settings if necessary.