Backside Laser Welding for Low-Porosity Titanium Fillet Joints
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Solution Overview
Problem
Current welding processes, such as EBW and GTAW, face challenges with titanium alloys in aerospace applications due to long processing times, high costs, slow cooling rates, limited access to complex joints, and poor microstructure quality, while laser beam welding often results in porous welds and contamination.
Innovation Solution
A method and system for laser welding metal substrates by applying laser energy to the backside surface, using a fiber laser and a beam delivery system to create a defocused output beam that moves in a predetermined pattern, forming dual fillet welds with uniform hardness, low porosity, and small grain size, suitable for complex joint configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electron beam welding (EBW) is used to achieve deep penetration and blind welding, then welding quality is improved, but processing time increases and cost increases
Solution Approach 1:
The patent replaces electron beam welding (a mechanical/physical process requiring vacuum chambers) with laser beam welding (an optical process). The laser beam delivers high energy density to achieve deep penetration welds without requiring vacuum environments, thereby reducing processing time and equipment complexity while maintaining weld quality.
Solution Approach 2:
The patent changes the energy delivery parameters by using a defocused laser beam with a larger spot size compared to conventional focused laser welding. This parameter change allows for broader heat distribution that achieves deep penetration while reducing the need for precise positioning and repeated passes, thereby improving productivity.
2Manufacturing precision
If electron beam welding (EBW) is used for deep penetration welding, then welding depth is improved, but cooling rate decreases
Solution Approach 1:
The patent substitutes electron beam welding with laser beam welding, which operates in atmospheric conditions allowing for convection-type cooling. This replacement maintains deep penetration capability while significantly improving the cooling rate through air convection, preventing excessive heat accumulation and distortion.
3Reliability
If gas tungsten arc welding (GTAW) is used for welding, then welding is achievable, but processing time increases due to low power density
Solution Approach 1:
The patent replaces gas tungsten arc welding (a thermal process with low power density) with laser beam welding (a high energy density process). The laser beam concentrates energy into a small spot, achieving rapid heating and melting, which dramatically reduces processing time while maintaining reliable weld formation.
Solution Approach 2:
The patent changes the power density parameter by using a defocused laser beam that, while having a larger spot size than focused laser welding, still maintains significantly higher power density compared to arc welding processes. This enables faster heating rates and reduced cycle times while avoiding the excessive heat input problems of conventional arc welding.
4Reliability
If gas metal arc welding (GMAW) or shielded metal arc welding (SMAW) is used, then welding is achievable, but heat input is very high causing poor microstructure and distortion
Solution Approach 1:
The patent replaces arc welding processes (GMAW/SMAW) with laser beam welding. The laser process delivers energy more concentratedly and controllably, achieving welding capability while minimizing total heat input. This prevents excessive thermal diffusion that causes poor microstructure and welding distortion in conventional arc welding.
Solution Approach 2:
The patent optimizes the laser beam parameters (power, spot size, scanning speed, focus position) to achieve a narrow process window with controlled heat input. The defocused beam configuration provides a balance between penetration depth and heat distribution, preventing the excessive heat input and large heat-affected zone characteristic of arc welding processes.
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 enables efficient, high-quality welding of titanium alloys with reduced processing time, improved microstructure, and access to complex joints, producing welds with uniform hardness and low porosity, addressing the limitations of existing methods.
Implementation Method 1
generating an input laser beam from a fiber laser
Implementation Method 2
irradiate a target area on the second planar surface of the first metal substrate with the beam spot
Implementation Method 3
applying laser energy to a backside surface... when in a molten state
Data Source
AI summary
Laser welding of a first metal substrate having a first planar surface and a second planar surface disposed opposite the first planar surface to a second metal substrate is performed by placing an end face of the second metal substrate proximate to the first planar surface. An input laser beam from a fiber laser is generated, and a beam delivery system is provided that is configured to receive the input laser beam and generate an output laser beam having a beam spot that moves in a predetermined pattern along a first and a second axes to irradiate a target area on the second planar surface such that the target area is positioned over an intersection region of the first planar surface where the end face is positioned proximate to the first planar surface.