Scarf-Joint Laser Butt Welding for Thin Steel Sheets
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Solution Overview
Problem
Conventional laser beam welding methods struggle to produce high-quality butt-weld joints in thin steel sheets with small thickness and large width, often resulting in gaps, burn-through, and reduced mechanical strength due to inaccurate cut surfaces and inappropriate inclination angles.
Innovation Solution
The method involves forming cut surfaces of steel sheets with precise inclination angles between 20° and 60° relative to the sheet surface, using a scarf joint, and weaving the laser beam in a spiral pattern to ensure complete melting and uniform heat input, with a minimum melting width of 0.7 times the cut surface width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mechanical shearing is used to cut steel sheets, then cutting speed is high, but cut surface straightness and quality deteriorate
Solution Approach 1:
The patent replaces mechanical shearing with laser beam cutting to form cut surfaces. The laser beam melts and vaporizes the material to create precise, straight cut surfaces with controlled inclination angles, eliminating the burr and shear drop problems associated with mechanical cutting while maintaining high cutting speed.
Solution Approach 2:
The patent changes the cutting method from mechanical contact to optical-thermal processing. By controlling laser beam parameters (power, focus position, scanning speed) and cut surface inclination angles (20°-60°), the process achieves both high cutting speed and precise cut surface quality suitable for butt welding.
2Productivity
If conventional laser beam welding is used on thin steel sheets, then welding speed is high, but burn-through and unmelted portions occur
Solution Approach 1:
The patent creates local quality variations by forming cut surfaces with specific inclination angles (20°-60°) on each steel sheet. This asymmetric geometry concentrates the laser beam energy distribution, ensuring complete melting at the root while preventing burn-through at the surface, thereby achieving reliable weld joints in thin steel sheets.
Solution Approach 2:
The patent performs preliminary action by pre-forming the cut surfaces with appropriate inclination angles before welding. This preparation ensures that when the laser beam irradiates the butted joint, the heat distribution is optimized from the start, preventing both burn-through and unmelted portions during the welding process.
3Ease of operation
If gap between butted steel sheets is large or varies, then alignment is easier, but weld joint mechanical strength deteriorates
Solution Approach 1:
The patent uses asymmetric cut surface geometry with inclination angles of 20°-60° on each sheet. This asymmetry creates a scarf joint configuration where the overlapping geometry compensates for gaps and misalignments, allowing the laser beam to maintain consistent energy distribution across the joint while achieving strong, defect-free welds even when gaps vary.
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 prevents burn-through and unmelted portions, ensuring high-quality welds with improved mechanical strength, reducing re-welding time and enhancing productivity in continuous processing lines.
Implementation Method 1
emitting a laser beam onto the butted part so as to melt the filler and the steel sheets
Implementation Method 2
melt the filler and the steel sheets
Data Source
AI summary
A laser-beam butt welding method is provided in which cut surfaces of two steel sheets each having a sheet thickness t of 0.1 to 3.0 mm are placed in contact with each other and butted together, and then the two steel sheets are welded together by feeding a filler to the butted part and emitting a laser beam onto the butted part so as to melt the filler and the steel sheets. In this method, the cut surfaces of the two steel sheets are formed by laser cutting so as to have inclination angles θ exceeding 20° but not exceeding 60° in the same direction relative to a plane perpendicular to surfaces of the steel sheets, and to have a width a of 3.0 mm or less in a steel-sheet longitudinal direction, and then the cut surfaces of the two steel sheets are butted together in a state of a scarf joint and welded together. Thus, a high-quality butt-weld joint can be produced even in thin steel sheets having a small sheet thickness and a large width.