Thin Overlap Laser Welding With Controlled Keyhole Depth
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Solution Overview
Problem
Laser welding of thin workpieces faces challenges such as spatter, pore formation, irregular weld depth, and mechanical instability, particularly in deep penetration welding, while heat conduction welding offers low feed rate and thermal distortion.
Innovation Solution
A method that transitions between heat conduction and deep penetration welding by overlapping two workpieces with thicknesses of 400 μm or less, where the laser beam melts the first workpiece fully and the second workpiece partially, generating a vapor capillary that extends to a capillary depth between 0.33 and 0.67 times the total weld depth, achieving a balanced weld depth and high feed rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If deep penetration welding is used, then feed rate and weld depth are improved, but spatter, pore formation, and weld seam instability occur
Solution Approach 1:
The patent applies parameter changes by precisely controlling the laser beam power and welding speed to maintain a specific relationship between vapor capillary depth and workpiece thickness. By adjusting these parameters within defined ranges, the welding process transitions from unstable deep penetration mode to a controlled mode that achieves both high feed rate and reliable weld quality without spatter or pores
Solution Approach 2:
The patent utilizes phase transitions by controlling the formation and collapse of the vapor capillary (keyhole) in the workpiece material. The laser beam induces localized melting and vaporization, creating a dynamic phase transition that enables deep penetration while maintaining weld stability through controlled capillary collapse and material backfilling
2Manufacturing precision
If heat conduction welding is used, then weld seam quality and thermal distortion are improved, but feed rate and weld depth are reduced
Solution Approach 1:
The patent applies dynamics by creating a dynamic welding process that adapts between heat conduction and vaporization mechanisms. The laser beam parameters are dynamically adjusted during welding to maintain optimal capillary depth relative to workpiece thickness, enabling the process to achieve both precise depth control and high feed rate by transitioning between different heating regimes
3Length of stationary object
If laser beam power is increased for deep penetration welding, then weld depth is improved, but spatter and pore formation increase
Solution Approach 1:
The patent applies partial action by using just enough laser power to create the required vapor capillary depth without excessive energy input. The method determines the minimum necessary power to achieve the target weld depth while avoiding the harmful effects of over-penetration, such as spatter and pore formation, by maintaining the capillary depth within 0.1 to 0.5 times the workpiece thickness
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 results in a high-quality weld seam with accurate weld depth, ensuring gastight and conductive connections while maintaining a high feed rate, minimizing thermal distortion and melt bath dynamics.
Implementation Method 1
melting, using a laser beam guided along the weld seam, a material of the first workpiece over an entirety of the thickness D1 and a material of the second workpiece over only a partial thickness TD of the thickness D2 in the region of overlap
Implementation Method 2
As a result of multiple reflections of the laser beam at the walls of the vapor capillary, the absorption in the workpiece material is increased
Implementation Method 3
the laser beam generates a pronounced vapor capillary (keyhole) in the workpiece material, said vapor capillary extending along the beam direction into the workpiece material
Implementation Method 4
As a result of multiple reflections of the laser beam at the walls of the vapor capillary, the absorption in the workpiece material is increased
Data Source
AI summary
A method for laser welding two workpieces includes arranging a first workpiece of a thickness D1 and a second workpiece of a thickness D2 on top of one another so that the first workpiece and the second workpiece overlap in a region of overlap. Each of D1 and D2 is 400 μm or less. The method further includes melting, using a laser beam guided along a weld seam, a material of the first workpiece over an entirety of the thickness D1 and a material of the second workpiece over only a partial thickness TD of the thickness D2 in the region of overlap, from a side of the first workpiece. The laser beam generates a vapor capillary that extends to a capillary depth KT into the first workpiece or into the first workpiece and the second workpiece, where 0.33*EST≤KT≤0.67*EST, with EST being a weld depth EST=D1+TD.