Welded Steel Blank Preparation for Low-Aluminum Laser Joints
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Solution Overview
Problem
Existing methods for manufacturing welded steel parts with aluminum pre-coatings face challenges such as intermetallic compound formation and reduced mechanical strength due to aluminum dilution during laser beam welding, leading to difficulties in achieving precise joint tracking and maintaining high corrosion resistance.
Innovation Solution
A method involving simultaneous peripheral removal of the metallic aluminum layer by pulsed laser ablation with a controlled clearance between sheets, followed by immediate welding, to prevent aluminum flow and ensure precise welding without the need for costly cleaning operations, while maintaining the intermetallic alloy layer for corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser beam welding is used to join pre-coated steel sheets, then welding speed and productivity are improved, but aluminum dilution occurs in the molten zone leading to intermetallic compound formation and reduced mechanical strength
Solution Approach 1:
The patent applies preliminary action by removing the aluminum pre-coating from the periphery of steel sheets before welding. This preventive measure eliminates the source of aluminum dilution before the welding process begins, thereby avoiding intermetallic compound formation and maintaining high mechanical strength in the welded joint while preserving fast welding speeds
2Strength
If the aluminum pre-coating is completely removed before welding, then aluminum dilution and intermetallic compound formation are prevented, but corrosion resistance is reduced
Solution Approach 1:
The patent applies local quality by selectively removing the aluminum pre-coating only from the peripheral areas where welding occurs, while preserving the pre-coating on the main surfaces of the steel sheets. This localized approach ensures that the welded joint has high mechanical strength free of intermetallic compounds, while the preserved pre-coating maintains corrosion resistance on the visible and structurally critical surfaces
3Ease of manufacture
If the metallic alloy layer is removed by laser beam impact, then the aluminum layer is eliminated, but aluminum flows onto the secondary face requiring costly cleaning operations
Solution Approach 1:
The patent applies periodic action by using pulsed laser beam impact to remove the metallic alloy layer. The pulsed delivery of energy allows controlled ablation of the aluminum layer without excessive melting and flow onto the secondary face. This periodic action achieves effective preparation for welding while minimizing aluminum contamination that would require cleaning operations
4Manufacturing precision
If the pre-coating is removed to prevent aluminum dilution, then welding quality is improved, but the cost of the manufacturing process increases due to additional cleaning operations
Solution Approach 1:
The patent applies preliminary action by performing selective removal of the metallic alloy layer from the periphery before welding. This preliminary preparation ensures high welding quality by preventing aluminum dilution in the molten zone, while the selective nature of the removal minimizes waste material and eliminates or reduces the need for subsequent cleaning operations, thereby controlling manufacturing costs
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 results in welded joints with improved mechanical strength, reduced aluminum content, and enhanced precision in joint tracking, enabling the production of high-strength, corrosion-resistant structural parts for the automotive industry.
Implementation Method 1
the metallic layer is removed simultaneously on peripheral portions of the opposite sheets by a process comprising melting and vaporization, in particular by the impact of a laser beam
Implementation Method 2
the metallic layer is removed simultaneously on peripheral portions of the opposite sheets by a process comprising melting and vaporization
Implementation Method 3
the metallic layer is removed simultaneously on peripheral portions of the opposite sheets by a process comprising melting and vaporization
Implementation Method 4
at least one source for obtaining a laser beam for welding the sheets in the area where the metallic layer is removed
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates to a method for preparing sheets (11, 12) for the manufacture of a welded steel blank, comprising the successive steps in which: at least one first (11) and one second (12) pre-coated steel sheets are supplied, consisting of a steel substrate (25, 26) and a pre-coating (15, 16) consisting of a layer of intermetallic alloy (17, 18) in contact with said steel substrate, surmounted by a metallic layer of aluminum or aluminum alloy or aluminum-based material (19, 20), the sheet (11) comprising a main face (111), an opposite main face (112), and at least one secondary face (71), the sheet (12) comprising a main face (121), an opposite main face (122), and at least one secondary face (72), then the first (11) and second (12) are brought together (12) sheet metal, leaving a gap (31) between 0.02 and 2 mm between the opposing secondary faces (71) and (72),the joining of the first (11) and second sheet (12) defining a median plane (51) perpendicular to the main faces of the sheets (11) and (12), then the metallic alloy layer (19) in a peripheral zone (61) of the sheet (11), and the metallic alloy layer (20) in a peripheral zone (62) of the sheet (12) are simultaneously removed by melting and vaporization from the main face (111) and the main face (121), the peripheral zones (61) and (62) being the zones of the main faces (111) and (121) closest to said median plane (51) located on either side of it.