Circumferential Laser Welding With Post-Weld Strain Correction
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Solution Overview
Problem
Laser welding methods face challenges in suppressing welding falling deformation in cylindrical bodies due to the lack of multiple welding passes, which are inherent in traditional laser welding processes that irradiate the groove portion over its entire circumference once.
Innovation Solution
A laser welding method and apparatus that includes a welding process followed by a strain correction process, where the groove portion is irradiated with a laser beam over the entire circumference after welding, with a heat input amount per unit area reduced in the strain correction process to apply heat and correct deformation, and the focal point distance and irradiation width are adjusted to manage heat input effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser welding is performed by irradiating the groove portion over the entire circumference once, then welding efficiency is improved, but welding falling deformation increases
Solution Approach 1:
The welding process is divided into multiple passes (first pass, second pass, third pass) instead of performing the entire welding in a single pass. Each pass welds a portion of the groove portion, distributing the heat input over time and reducing cumulative deformation while maintaining overall welding efficiency.
Solution Approach 2:
The laser beam is applied periodically in multiple passes with intervals between them, allowing the workpiece to cool and partially relax between heating cycles. This periodic heating approach reduces thermal accumulation and associated deformation compared to continuous single-pass welding.
2Manufacturing precision
If multiple welding passes are performed, then welding falling deformation is suppressed, but welding time increases
Solution Approach 1:
Each welding pass applies heat to only a portion of the groove portion rather than the entire circumference, using partial action to reduce heat input per pass. This allows multiple passes to be performed with controlled deformation while the cumulative effect achieves complete welding.
Solution Approach 2:
The laser beam parameters (power, speed, focal position) are optimized to achieve efficient welding in each pass. By carefully controlling these parameters, the welding process achieves high efficiency in each individual pass, reducing the total time required for multiple passes compared to traditional approaches.
3Productivity
If high heat input is applied in laser welding, then welding speed is improved, but welding falling deformation increases
Solution Approach 1:
The total heat input required for welding is segmented across multiple passes, with each pass applying a controlled portion of the total heat. This segmentation allows maintaining adequate welding speed in each pass while preventing excessive cumulative heat input that causes deformation.
Solution Approach 2:
The periodic application of heat in multiple passes with cooling intervals allows each heating cycle to be performed at high intensity for efficiency, while the intervals prevent thermal accumulation. This periodic action reconciles high welding speed with controlled deformation.
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 effectively reduces welding falling deformation by applying targeted heat to the groove portion post-welding, allowing for the suppression of deformation and residual stress in cylindrical bodies, thereby improving the stability and accuracy of the welding process.
Implementation Method 1
welding is performed by irradiating with a laser beam the groove portion formed by butting the axial end portions of the cylindrical bodies together
Implementation Method 2
a strain correction process of irradiating the groove portion with the laser beam over the entire circumference
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A laser welding method of the present invention is a laser welding method for irradiating with a laser beam a groove portion 6 formed along a circumferential direction by butting axial end portions of cylindrical bodies 5a, 5b together to weld the groove portion, the method comprising: a welding process S2 of irradiating the groove portion 6 with the laser beam over the entire circumference to weld the groove portion; and a strain correction process S4 of irradiating the groove portion 6 with the laser beam over the entire circumference, the laser beam having a heat input amount smaller than a heat input amount per unit area of the laser beam emitted in the welding process S2.