Excessive Penetration Drop-Through
Weld sagging occurs when too much weld metal melts through and the weld gets too thin. This can be caused by excessive heat input or wrong welding parameters.
Physico-chemical mechanism of action
During welding, a weld pool is formed where the metal melts. If the heat input is too high or the weld metal volume is too large, the weld pool can spread downward. This causes excess weld metal to flow out, resulting in an undercut.
Metallurgical relevance & welding risks
An undercut can lead to several problems: the weld becomes thin and loses its mechanical properties, which can lead to cracks or failure in service. Additionally, a severe undercut can increase the hardness of the weld, which may cause hot cracking.
Workshop practice & action instructions
To avoid undercut, take the following measures:
• Reduce heat input by optimizing travel speed and adjusting the inductance.
• Use a wire with a suitable diameter—not too large.
• Control the temperature of the weld pool and ensure even evaporation.