Al Alloy Remote Laser Welding Without Filler Wire
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Solution Overview
Problem
Aluminium alloys in the AA6XXX series are sensitive to cracking during laser welding, particularly causing critical cracks in the welded bead, and existing solutions fail to provide monolithic sheets with mechanical, formability, and corrosion characteristics comparable to those used in the automobile industry without the use of filler wires.
Innovation Solution
Development of aluminium alloy sheets with specific chemical compositions, including Si: 2.5-14%, Fe: 0.05-0.80%, Cu: ≤0.20%, Mg: 0.05-0.8%, Mn: ≤0.70%, Cr: ≤0.35%, Ti: 0.02-0.30%, and Sr up to 500 ppm, for remote laser welding without filler wire, optimizing weldability and formability while maintaining mechanical strength and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If aluminium alloys in the AA6XXX series are used for laser welding, then mechanical strength and formability are improved, but cracking sensitivity during welding increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the aluminium alloy, specifically limiting Si to 2.5-14%, Fe to 0.05-0.80%, Cu to ≤0.20%, Mg to 0.05-0.8%, and adding Ti (0.02-0.30%) and Sr (up to 500 ppm). This compositional parameter optimization resolves the contradiction by creating an alloy that maintains high mechanical strength while significantly reducing cracking sensitivity during laser welding, achieving weld quality comparable to traditionally used AA6XXX family alloys.
2Reliability
If filler wire is used during laser welding to reduce cracking, then weldability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies the extraction principle by removing the filler wire from the welding process entirely. Through optimized base metal composition (specifically the controlled Si, Fe, Cu, Mg content and added Ti, Sr), the alloy achieves inherent crack resistance that eliminates the need for external filler materials. This simplifies the manufacturing process, reduces complexity, and lowers cost while maintaining excellent weldability and reducing cracking during laser welding.
3Reliability
If silicon content is increased above 2% to reduce cracking sensitivity, then weldability is improved, but mechanical strength and formability deteriorate
Solution Approach 1:
The patent applies parameter changes by establishing an optimal silicon content range of 2.5-14%, with a preferred sub-range of 2.7-5.0%. This precise parameter control, combined with limiting other alloying elements (Fe: 0.05-0.80%, Cu: ≤0.20%, Mg: 0.05-0.8%) and adding Ti (0.02-0.30%) and Sr (up to 500 ppm), resolves the contradiction by achieving crack resistance without sacrificing mechanical strength and formability, unlike conventional approaches that simply increase Si above 2%.
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 proposed solution significantly reduces the tendency for cracking during laser welding, maintains mechanical strength and formability, and ensures corrosion resistance, achieving weld quality and properties comparable to traditionally used alloys in the AA6XXX family.
Implementation Method 1
The invention relates to the domain of parts formed by stamping or extrusion for automobiles, particularly parts assembled by remote laser welding without filler wire
Data Source
AI summary
The invention relates to a method for the laser welding of monolithic semi-finished products made from aluminium alloy, without filler wire, known to the person skilled in the art as “remote laser welding”, comprising the following steps: supplying at least two aluminium alloy semi-finished products, of which at least one is a rolled sheet of composition (wt.-%): Si: 2.5-14, preferably 2.7-5.0; Fe: 0.05-0.80, preferably 0.15-0.60; Cu: ≥0.20, preferably ≥0.10, also <0.05, and even <200, also 100 ppm; Mg: 0.05-0.80, preferably 0.20-0.40; Mn: ≥0.70, preferably ≥0.30; Cr: <0.35; Ti: 0.02-0.30; Sr up to 500 ppm; Na up to 200 ppm; Sb up to 0.15%, other elements <0.05 each and <0.15 total, remainder aluminium, on the condition that A: 5.2 Fe+1.95 Si−0.5 Cu−Mg≥7.0; and welding semi-finished products made from aluminium alloy, without filler wire, a method known the person skilled in the art as “remote laser welding”.