Meaning
High energy density welding creates a narrow and deep fusion zone through the direct vaporization of the base material. Operating in keyhole mode involves a laser or electron beam that bores into the metal to form a stable vapor capillary. This geometry allows for high aspect ratio welds that join thick battery busbars with minimal heat input to the surrounding area.
Depth Control
Penetration depends on the balance between the vapor pressure inside the hole and the surface tension of the liquid metal. If the power density drops, the keyhole mode collapses and the process reverts to a shallower melting profile.
Porosity Risk
Entrapment of shielding gas or metal vapor during the solidification of the weld pool creates internal voids. Because the keyhole mode moves at high speeds, the liquid trailing the beam must flow quickly to fill the cavity. Unstable capillaries can pinch off at the root and leave behind spherical gas pockets.
These defects reduce the effective cross section of the joint and increase the risk of mechanical failure. Maintaining a steady travel speed and constant power output is the primary defense against such inconsistencies.
Power Density
Focused energy must exceed a specific threshold to overcome the thermal losses from conduction. The transition to keyhole mode is marked by a sharp increase in the absorption of laser light.
