Unacceptable cap undercut
Excessive cap undercut is a narrow, deep groove in the base metal right at the top edge line of the cap, acting like a notch. It can cause cracks and distortion.
Physicochemical Mechanism of Action
Insufficient root penetration occurs due to the lack or inadequate removal of contaminants (such as oxygen, carbon) before the actual welding process begins. This leads to a greatly reduced melting time and incomplete cooling of the weld.
Metallurgical Relevance & Welding Risks
Insufficient root penetration can lead to cracks, deformation, and reduced toughness of the weld metal. The notch can also increase stress concentration in the joint and lead to further defects such as hot cracks or shear cracks.
Workshop Practice & Instructions
To avoid insufficient root penetration, it is crucial to clean and degrease the base material thoroughly before welding. Use a high-quality cleaning fluid and ensure that all contaminants are completely removed. Also, make sure the welding process is carried out at the correct temperatures and times.