Keyhole Formation
Keyhole formation is the creation of a vapor-filled channel in the weld pool through high-energy beam processes. This allows deep penetration through multiple reflections of the beam energy.
Physical-Chemical Mechanism of Action
Keyhole formation happens when high-energy beams (e.g., laser welding) penetrate the workpiece's weld pool and get reflected multiple times. These reflections focus energy on a small point, leading to deep penetration.
Metallurgical Relevance & Welding Risks
Keyhole formation can produce very deep and precise penetration, useful for fine mechanics or making microstructures. But it also raises the risk of hot cracking, because the steel heats up rapidly in a short time. Cooling too fast can form martensite, making the steel hard and crack-prone.
Shop Practice & Instructions
To use keyhole formation effectively, keep the weld pool well covered to promote reflections. Set the beam energy precisely to get the desired penetration. After welding, controlled cooling is needed to avoid hot cracks. Recommended cooling times vary by material and thickness, but typically should be between 10 and 30 seconds.