Composite Laser Beam Welding for Uniform Penetration Control
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Solution Overview
Problem
Laser welding methods face challenges with irregular weld seams due to varying penetration of the laser beam along the weld seam, leading to poor weld quality, particularly when using one-micrometer waveband laser beams with oxygen assist gas on mild steel sheets, which cause unnecessary melt width and self-burning.
Innovation Solution
A composite laser beam configuration comprising a circular center beam and an annular ring beam, generated by a fiber laser and fiber-coupled laser devices, with a wavelength difference of at least 10 nanometers or a spectrum width of at least 10 nanometers, is used to improve weld quality by stabilizing penetration depth and reducing spatter and porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a one-micrometer waveband laser beam with Gaussian beam profile is used with oxygen assist gas to cut mild steel sheet, then high optical energy intensity and absorbance is achieved, but the melt width on the top face widens unnecessarily and self-burning occurs which deteriorates cutting quality
Solution Approach 1:
The patent applies local quality by using a ring-shaped beam profile instead of a Gaussian beam, concentrating energy in an annular region rather than at the center. This creates a localized intensity distribution that prevents excessive melting at the beam center while maintaining high energy density in the ring region, thereby controlling kerf width and preventing self-burning during cutting of mild steel sheets
Solution Approach 2:
The patent changes the beam profile parameter from Gaussian to ring-shaped, and also utilizes wavelength tuning within the one-micrometer waveband to optimize absorption characteristics. By adjusting these parameters, the system achieves high optical energy intensity while controlling melt width and preventing harmful effects like self-burning
2Device complexity
If conventional single-mode laser beam welding is used, then welding process is simple, but penetration varies along the weld seam resulting in irregular or rough weld seam
Solution Approach 1:
The patent segments the laser beam into multiple modes, specifically combining fundamental mode and higher-order modes to create a composite beam profile. This segmentation allows different parts of the beam to contribute differently to the welding process, with the fundamental mode providing stable penetration and higher-order modes shaping the energy distribution, resulting in uniform penetration depth and regular weld seams while maintaining manageable system complexity
Solution Approach 2:
The patent uses a composite laser beam composed of multiple modes (fundamental mode and higher-order modes) combined in specific proportions. This composite beam structure leverages the advantages of each mode to achieve consistent penetration depth and high-quality weld seams, analogous to using composite materials to combine properties of different materials
3Productivity
If ring-shaped laser beam is used instead of conventional beam profiles, then cutting can be performed at much lower power levels improving cutting speed and quality, but device complexity increases
Solution Approach 1:
The patent employs dynamic control of the laser beam by adjusting the ratio of fundamental mode to higher-order mode power in real-time based on cutting conditions. This dynamic adaptation allows the system to optimize cutting performance for different materials and thicknesses while using a relatively simple fiber laser source, achieving high cutting speed and quality without excessive device complexity
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
The composite laser beam configuration achieves deeper and more uniform penetration, reduces spatter, and enhances weld seam quality by minimizing porosity and avoiding deformation during welding, especially for aluminum alloys.
Implementation Method 1
the laser beam is typically condensed through a condenser lens into a spot of 100-500 μm to increase energy density and instantaneously heat the workpiece to a temperature of 1500° C. or over so that the workpiece melts
Implementation Method 2
the second output laser beam comprises a first wavelength and a second wavelength having difference of at least 10 nanometers, or the second output laser beam has spectrum width of least 10 nanometers
Data Source
AI summary
The invention concerns an apparatus and its use for laser welding. A laser welding apparatus comprise at least one first laser device, each providing at least one first optical feed fiber with a first laser beam; at least one second laser device, each providing at least one second optical feed fiber with a second laser beam; means for generating a composite laser beam comprising a first output laser beam and a second output laser beam for welding a workpiece; wherein the first output laser beam has a circular cross-section and the second output laser beam has an annular shape concentric to the first output laser beam. The second laser device is a fiber laser device or a fiber-coupled laser device. The apparatus is configured to form the second output laser beam at least on the basis of the second laser beam, and the second output laser beam comprises a first wavelength and a second wavelength having difference of at least 10 nanometers, or the second output laser beam has spectrum width of least 10 nanometers.