Laser Fillet Welding End-Crater Control for Aluminum Overlap Joints
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Solution Overview
Problem
Laser beam welding of fillet welds often results in end craters and cracks, which weaken the weld and can lead to component failure, especially in materials prone to hot cracking like aluminum alloys.
Innovation Solution
The method involves offsetting the laser beam transversely onto the upper sheet at the end of the fillet weld section, reducing laser power below the deep welding threshold, and continuing the beam movement over an additional distance to ensure even solidification and fill the seam end, preventing hot cracks and end craters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser beam welding is performed with deep penetration to create slim weld geometries, then welding efficiency and penetration depth are improved, but end crater formation and end crater cracks occur due to rapid cooling and material shrinkage
Solution Approach 1:
The method applies preliminary action by continuing the laser beam movement beyond the nominal weld end point into an overweld section. This preliminary extension of the welding process allows the laser beam to gradually reduce power and speed, creating a transition zone that prevents sudden cooling and material shrinkage at the weld end, thereby eliminating end crater formation before it can occur
Solution Approach 2:
The invention implements dynamics by continuously varying the laser beam parameters (power and feeding speed) throughout the welding process, particularly in the approach section and overweld section. The laser power is gradually reduced from the base value to zero, while the feeding speed is adjusted to maintain optimal energy input, creating a dynamic control strategy that adapts to the changing thermal conditions and prevents end crater formation
2Manufacturing precision
If laser power is reduced and welding speed is decreased towards the weld end, then end crater formation is reduced, but welding productivity decreases
Solution Approach 1:
The welding process is segmented into distinct sections: an approach section leading to the weld end, a weld end section where the actual termination occurs, and an overweld section extending beyond the nominal weld end. Each section has optimized laser power and feeding speed parameters, allowing the majority of the weld (the main section) to be completed at high productivity while only a small portion requires reduced parameters for end crater prevention
Solution Approach 2:
The invention applies parameter changes by systematically varying laser power and feeding speed across different welding sections. In the approach section, power is reduced to 50-80% of base value; in the overweld section, power continues to decrease to zero while speed is adjusted to maintain 50-80% of base value. These controlled parameter changes achieve end crater reduction while minimizing impact on overall welding productivity
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 eliminates or significantly reduces end craters and cracks, enhancing the breaking strength of the weld seam without the need for filler materials, particularly suitable for materials susceptible to hot cracking like aluminum alloys.
Implementation Method 1
The laser beam is guided along the joint with a feed motion in one welding direction, where it melts the materials to form a weld pool
Implementation Method 2
which subsequently cools to create a weld seam
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a method for laser welding a front fillet seam with a reduced end crater, wherein a laser beam is guided to generate the front fillet seam (52) with an advancing movement in a welding direction (X) along a join (40) of two components (20, 30) arranged such that they are partially overlapping, in particular components made of aluminium alloys at risk of hot-cracking, wherein a seam end section (54) is formed adjacent to the front fillet seam (52), from which molten material drains into the region of the front fillet seam (52), wherein upon reaching an end point of the front fillet seam (52) to be formed, the laser beam is adjusted transverse to the advancing movement on the upper surface (20) and the advancing movement of the laser beam is continued in the welding direction over an additional section, while the power (P) of the laser beam is reduced to at least below the deep welding threshold. The invention also relates to a weld seam with a reduced end crater and a laser welding device.