Dual-Beam Laser Keyhole Welding for End-Crack Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-strength metals and metal alloys are prone to cracking at the termination of laser welds due to thermal and mechanical stress, leading to potential catastrophic failures, as existing solutions like rapid power ramp-down or beam lifting are insufficient for these materials.
Innovation Solution
A method involving a focused center beam and a concentric focused annular beam is used for laser welding, where the annular beam is ramped down and the center beam is ramped up and then down in a controlled manner to reduce the melt zone and keyhole dimensions, minimizing residual stress and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rapid power ramp-down or beam lifting is used at weld termination, then cracking is reduced for many materials, but high-strength alloys and high thermal conductivity metals remain prone to cracking
Solution Approach 1:
The laser beam is divided into two separate beams: a center beam and an annular beam. The center beam continues to provide localized heating at the weld termination point while the annular beam ramps down to reduce overall heat input. This segmentation allows independent control of each beam's power profile, enabling the center beam to prevent cracking while the annular beam controls total thermal energy input.
Solution Approach 2:
Different regions of the weld zone receive different heating profiles through the dual-beam approach. The center beam provides concentrated local heating at the termination point to prevent stress-induced cracking, while the annular beam provides broader regional heating control. This local quality differentiation allows precise control over the thermal history of different zones within the weld.
2Productivity
If higher laser power is used to maintain weld speed and quality, then productivity is improved, but thermal stress and cracking risk increase at weld termination
Solution Approach 1:
The laser power profile is made dynamic through independent temporal control of the center and annular beams. During normal welding, both beams operate at full power for high productivity. At weld termination, the annular beam ramps down while the center beam maintains or increases power, creating a dynamic power distribution that adapts to the changing thermal conditions and prevents stress-induced cracking.
Solution Approach 2:
The annular beam is ramped down in advance before the center beam is fully reduced, preparing the thermal field for termination. This preliminary action of reducing overall heat input while maintaining localized center beam heating allows the material to cool more uniformly and reduces thermal gradients that would otherwise cause stress and cracking at the weld end.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach prevents cracking and defects at the weld termination by controlling the cooling rate and annealing the solidified material, maintaining weld quality and speed while reducing the risk of premature failure.
Implementation Method 1
delivering a focused beam of laser-radiation to the workpiece
Implementation Method 2
Absorbed laser power heats the irradiated material, melting material in each part to be joined
Implementation Method 3
higher power densities that are sufficient to vaporize some of the irradiated material. Pressure of the vaporized material on surrounding melted material opens a channel through the melted material
Implementation Method 4
The annular beam is ramped down from the annular processing power to an off-power over a ramping-down time when the focus reaches the stop location. The center beam is ramped up from the center processing power over a first time duration, then the center beam is ramped down to an off-power over a second time duration
Implementation Method 5
melting material in each part to be joined, which flows, mixes, and then solidifies
Data Source
AI summary
A method for laser keyhole welding of metal alloys is disclosed. The method independently adjusts power in a focused center beam and power in a concentric focused annular beam. At the termination of a weld, the power in the center beam is initially ramped up and then ramped down, while the power in the annular beam is ramped down. Increasing the power in the center beam enables a controlled and prolonged contraction of the keyhole and melt pool, thereby preventing undesirable cracking.