Laser Welding Scan Pattern for Low-Spatter Metal Pin Pairs
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Solution Overview
Problem
Existing laser welding techniques for metal pin pairs, such as hairpins and I-pins in stators, suffer from spatter and void formation, which reduce the quality and conductivity of the weld nugget.
Innovation Solution
A method involving a time-dependent laser scan pattern and energy input, where a first path is traced at a higher energy rate to form a melt pool, and a second path is traced at a lower energy rate within the first path to minimize spatter and maximize the weld nugget's depth and area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If keyhole welding is used to achieve deep penetration and strong welds, then weld depth and strength are improved, but spatter and void formation increase
Solution Approach 1:
The welding process is divided into multiple passes with different energy densities. The first pass creates the keyhole for deep penetration, while subsequent passes at lower energy density fill voids and reduce spatter, effectively segmenting the welding function to resolve the contradiction between depth and quality
Solution Approach 2:
The laser applies periodic pulsing with varying power levels during welding. High-power pulses create keyhole penetration while lower-power pulses between them allow vapor escape and reduce spatter, using temporal periodicity to balance deep welding with reduced harmful effects
2Length of stationary object
If higher laser power density is applied to maximize weld nugget depth, then weld nugget depth is improved, but spatter increases reducing weld quality
Solution Approach 1:
The laser power density is dynamically adjusted during the welding process rather than maintained at a constant high level. The system transitions from high power density for keyhole formation to lower power density for consolidation, using dynamic control to achieve both depth and quality
3Length of stationary object
If continuous high energy input is used to form deep weld nuggets, then weld nugget depth is improved, but void formation increases impeding electrical conduction
Solution Approach 1:
The first welding pass preliminarily creates the keyhole and initial melt pool at high energy density, preparing the structure for subsequent passes. This preliminary action enables the second pass to effectively fill voids and consolidate the weld, achieving both depth and electrical conductivity
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 effectively minimizes spatter and void formation, resulting in a deeper and larger weld nugget with improved electrical conductivity between the metal pins.
Implementation Method 1
Laser welding uses a continuous or pulsed laser beam as a concentrated heat source to locally melt and join two parts
Implementation Method 2
Keyhole welding occurs at higher laser powers and higher laser 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. This channel, known in the art as a keyhole
Implementation Method 3
Pressure of the vaporized material on surrounding melted material opens a channel through the melted material
Implementation Method 4
The present method applies a time-dependent laser scan pattern and energy input to resolve these issues
Data Source
AI summary
A method for laser welding a pair of metal pins delivers a laser beam to a work-side of the pair of metal pins where a respective pair of surfaces of the metal pins are adjacent to each other and face in the same direction. The laser beam first traces a first path on the work-side to form a melt pool by keyhole welding. The first path crosses an interface between the metal pins. After tracing the first path, the laser beam is switched to trace a second path on the work-side with the laser beam at a delivered rate of energy per unit path length that is less than the one used for the first path. The second path crosses the interface and is within the first path. The method is well-suited for welding of hairpin and I-pin stators.