Laser Lap Welding of Aluminum Castings With Molten Pool Stirring
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Solution Overview
Problem
Lap welding of aluminum alloy castings using a laser beam often results in large blow holes due to gas bubbles, degrading the quality of the welding part, and existing methods to prevent this reduce productivity.
Innovation Solution
A laser welding method that uses a first laser beam to form a molten pool and a second laser beam with a higher scanning speed to stir and miniaturize bubbles, preventing large blow holes without the need for extended bubble discharge time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a laser beam is used to weld aluminum alloy castings, then welding speed and productivity are improved, but large blow holes are generated due to gas bubbles in the molten pool
Solution Approach 1:
The patent applies vibration to the laser beam or welding process to disrupt the molten pool and break up gas bubbles. This mechanical vibration prevents large bubbles from forming and becoming trapped, thereby eliminating blow holes while maintaining high welding speed and productivity
Solution Approach 2:
The patent modifies welding parameters such as laser power, scanning speed, and focus position to optimize the welding process. By carefully controlling these parameters, the molten pool dynamics are adjusted to promote bubble escape and prevent blow hole formation while maintaining high productivity
2Productivity
If the laser beam scanning speed is increased to improve productivity, then welding efficiency is improved, but bubbles cannot be discharged from the molten pool in time
Solution Approach 1:
Vibration is applied to the laser beam or welding system to create turbulent flow in the molten pool. This turbulence accelerates bubble rise and discharge, allowing bubbles to be expelled even at high welding speeds where the molten pool exists for a very short duration
Solution Approach 2:
The patent employs periodic vibration or pulsing of the laser beam to create cyclical disturbances in the molten pool. This periodic action enhances bubble detachment and discharge, enabling efficient bubble removal during rapid welding processes
3Manufacturing precision
If arc welding is combined with laser welding to prevent blow holes, then welding quality is improved, but device complexity and process complexity increase
Solution Approach 1:
The patent extracts or removes the need for arc welding by using an improved laser welding process alone. By eliminating the arc welding component and relying on vibration-assisted laser welding, the system achieves blow hole prevention with simpler equipment and a single welding method
Solution Approach 2:
The patent introduces vibration as an intermediary element that mediates between the laser beam and the molten pool. This vibration mechanism enables bubble control and blow hole prevention without requiring the addition of arc welding, thus avoiding the complexity of combining multiple 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 method effectively reduces the generation of large blow holes in the welding part, maintaining the strength of the weld while minimizing productivity losses.
Implementation Method 1
a melting step of scanning and irradiating circularly a superimposed part made by superimposing the plurality of metal plates with a first laser beam so as to form a molten pool made from the plurality of molten metal plates
Implementation Method 2
a stirring step of scanning and irradiating circularly the molten pool with a second laser beam having a scanning speed faster than a scanning speed of the first laser beam so as to stir the molten pool, wherein the second laser beam is emitted outside a laser scanning area of the first laser beam
Data Source
Figure 1~1(b)
Figure 2~2(b)
Figure 3~4
AI summary
In a laser welding method, generation of relatively large blow holes in a welding part is prevented while decrease in productivity is reduced. The laser welding method for lap welding, using a laser beam LB, of a plurality of metal plates and including an aluminum alloy cast plate includes: a melting path of scanning and irradiating circularly a superimposed part of the aluminum alloy plate and the aluminum alloy cast plate with a first laser beam LB1 to form a molten pool of the molten aluminum alloy plate and the molten aluminum alloy cast plate; and a stirring path of scanning and irradiating circularly the molten pool with a second laser beam LB2 having a scanning speed V2 faster than a scanning speed Vi of the first laser beam LB1 to stir the molten pool.