Dual-Beam Laser Keyhole Welding for Crack-Free Weld Termination
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Solution Overview
Problem
High-strength metal alloys are prone to cracking at the termination of laser welds due to thermal and mechanical stress, leading to unreliable welds and potential catastrophic failures, as existing methods fail to maintain uniform weld cross-sections and are insufficient for materials with high thermal conductivity.
Innovation Solution
A method involving a focused center beam and a concentric focused annular beam is used for laser welding, where the power of the annular beam is gradually reduced and then increased, while the center beam power is adjusted to maintain a stable keyhole and control solidification, preventing cracks by ensuring uniform heating and cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power of the annular beam is ramped down and center beam power is ramped up as the focused laser beam approaches the end of a line weld, then defects at the termination of the weld are prevented, but the weld width becomes non-uniform with a gradual taper
Solution Approach 1:
The laser beam is segmented into two distinct components: a center beam and an annular beam. This segmentation allows independent power control of each beam component, enabling the center beam power to be ramped up while the annular beam power is ramped down during the welding process, thereby preventing defects at weld termination while maintaining uniform weld width through coordinated power adjustment of the two segments.
2Productivity
If the focused laser beam is moved laterally across the workpiece surface during power changes, then the welding process continues, but a gradual taper in weld width is produced
Solution Approach 1:
The laser beam power distribution is made dynamic during the welding process. As the focused beam approaches the weld end, the system dynamically adjusts the power of the center and annular beams in real-time, ramping up the center beam power while ramping down the annular beam power. This dynamic power adjustment maintains welding continuity while compensating for the natural taper effect, preserving uniform weld cross-section.
3Reliability
If rapid power reduction or beam lifting is used at weld termination, then defects are mitigated for many materials, but high-strength metal alloys with high thermal conductivity remain prone to cracking
Solution Approach 1:
The welding method applies local quality control by differentiating the power adjustment strategy for different beam components. The center beam receives increased power while the annular beam has its power reduced, creating a localized power distribution that is optimized for high-strength metal alloys with high thermal conductivity. This localized power quality adjustment prevents cracking in these difficult-to-weld materials while maintaining overall process reliability.
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 method produces welds with uniform cross-sections, minimizing cracking and maintaining weld quality, speed, and precision, even in high-strength metal alloys, by controlling the power and movement of the laser beams to prevent defects and ensure symmetrical solidification.
Implementation Method 1
Conduction welding occurs at lower laser powers and lower power densities. Absorbed laser power heats the irradiated material, melting material in each part to be joined, which flows, mixes, and then solidifies.
Implementation Method 2
Keyhole welding occurs at higher laser powers and 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
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
A method for laser keyhole welding is disclosed to weld two pieces together made of a metal alloy. 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 of the annular beam (PA) is reduced, motion of the focused beams is stopped, the power of the center beam (Pc) is increased, and the power of both beams is initially ramped down rapidly and then ramped down slowly. Increasing the power of the center beam equalizes the temperature of both pieces prior to solidification and cooling at the termination of the weld. An additional pulse of power may be applied to prevent the formation of defects or to erase any defects.