Laser Weld Structure with Center Heating to Prevent Solidification Cracks
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Solution Overview
Problem
Laser welding methods often result in cracks in solidified weld sections due to uneven solidification rates, particularly in aluminum alloys, where heat dissipation from the periphery to the center causes premature solidification shrinkage at the center, leading to crack generation and extension.
Innovation Solution
A laser welding method involving a first laser beam to form a molten pool and a second laser beam that circles or focuses on the center of the molten pool to delay solidification, promoting uniform solidification and reducing crack formation by controlling the solidification rate and crystal structure growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a laser beam is projected onto the weld region to melt workpieces, then welding reliability is improved, but crack generation in the solidified section occurs due to uneven solidification rates
Solution Approach 1:
The patent applies periodic action by using a second laser beam that irradiates the weld region in a periodic or continuous manner during the solidification phase. This periodic thermal input prevents uniform cooling and maintains liquid state at critical locations, allowing liquid flow to compensate for solidification shrinkage and prevent crack formation while preserving the benefits of initial laser welding
Solution Approach 2:
The patent implements preliminary anti-action by applying a second laser beam before cracks can form during solidification. This preemptive thermal intervention counteracts the harmful solidification shrinkage effects by maintaining localized melting and enabling liquid flow compensation, thereby preventing crack generation in the first place
2Manufacturing precision
If the laser beam scans to circle around the weld region center, then uniform heat distribution is achieved, but heat dissipation from periphery causes faster solidification at center leading to cracks
Solution Approach 1:
The patent applies inversion by reversing the expected solidification pattern. Instead of allowing natural periphery-to-center solidification progression, the second laser beam selectively maintains melting at the periphery or provides continuous thermal input, inverting the solidification sequence to prevent center crack formation while preserving uniform heat distribution benefits
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 method effectively reduces crack generation and extension in weld sections by ensuring uniform solidification and crystal growth, resulting in a more reliable and crack-resistant weld structure.
Implementation Method 1
forming a melted section in which plural metallic workpieces within a weld region are melted by projecting a first laser beam onto the weld region
Implementation Method 2
projecting a second laser beam while the melted section is being solidified such that the second laser beam circles around center of the melted section
Implementation Method 3
heat is more likely to be dissipated from a periphery of a melted section (a molten pool) that has been melted rather than the center of the melted section, and thus solidification of the melted section starts from the periphery of the melted section and progresses toward the center
Data Source
AI summary
A laser welding method includes: forming a melted section in which plural metallic workpieces within a weld region are melted by projecting a first laser beam onto said weld region with parts of the workpieces being set as the weld region when the workpieces are welded; and projecting a second laser beam while the melted section is being solidified or after a solidified section in which the melted section is solidified is formed such that the second laser beam circles around center of the melted section or the solidified section from an irradiation start position deviated from said center toward said center or such that the second laser beam is focused to the center of the melted section or the solidified section from an irradiation start region that includes the center and a periphery thereof.