Laser Weld Repair with Small-Spot Crack Erasure and Burn-Through Control
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Solution Overview
Problem
Conventional laser welding repair devices face challenges in efficiently erasing cracks in structural members without causing burn-through, especially when operating in a flat position, due to the need for high laser output or slow movement speeds.
Innovation Solution
A laser welding method that uses a spot diameter of less than 3 mm to move the laser light and enlarge the heat input area, ensuring the crack is within the heat input area, while controlling the temperature to avoid burn-through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser light with large spot diameter (φ3 to 7 mm) is used to erase cracks, then the crack can be eliminated, but the required laser output increases and movement speed must be slowed down
Solution Approach 1:
The patent divides the crack elimination process into multiple passes. Instead of attempting to eliminate the entire crack in one pass with a large spot diameter, the laser light is moved along the crack in multiple sequential passes, with each pass covering a portion of the crack. This segmentation allows the use of a smaller spot diameter (φ1 to 2 mm) while maintaining effective crack elimination and enabling faster movement speeds.
Solution Approach 2:
The patent applies partial action by having the laser light cover a region slightly wider than the crack itself. The laser light irradiates a region that includes the crack plus additional surrounding areas, ensuring complete crack elimination while allowing the use of a smaller spot diameter and faster movement speed. This partial excess coverage compensates for the reduced spot size.
2Manufacturing precision
If laser light of large output is used to compensate for decreased energy density, then crack elimination is achieved, but burn through easily occurs during welding in flat position
Solution Approach 1:
The patent fundamentally changes the key parameter of spot diameter from large (φ3 to 7 mm) to small (φ1 to 2 mm). This parameter change increases energy density, allowing crack elimination with lower laser output. The smaller spot diameter concentrates energy more intensely, enabling effective crack removal without requiring high power that would cause burn through in flat position welding.
Solution Approach 2:
The laser light irradiates a region that is slightly wider than the crack itself, covering the crack plus additional surrounding areas. This partial excess coverage ensures complete crack elimination while using a smaller spot diameter and lower laser output, thereby preventing burn through.
3Power
If spot diameter is reduced to less than 3 mm to decrease laser output requirement, then high energy density is achieved, but the movement of laser light increases making it difficult to trace the crack
Solution Approach 1:
The laser light is moved to cover a region that extends beyond the crack boundaries, including the crack plus additional surrounding areas. This partial excess coverage ensures that even with the smaller spot diameter (φ1 to 2 mm), the entire crack is effectively traced and eliminated. The extended coverage compensates for the reduced spot size and makes crack tracing easier.
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 achieves a decrease in required laser output, allows for high-speed operation, and effectively erases cracks without leaving residues or causing burn-through, even in flat position welding.
Implementation Method 1
laser light having a spot diameter of less than 3 mm is moved along the crack... this welding repair portion is molten to erase the crack
Implementation Method 2
When the member is cooled by heat dissipation after operation, at this temperature or less, the yield strength of the structural member recovers
Data Source
AI summary
A laser welding repair device includes a laser oscillator, a laser head that condenses laser light from the laser oscillator to irradiate a repair portion, a temperature sensor that detects a temperature distribution of a steel material irradiated with the laser light, and a control unit. The control unit sets a spot diameter of the laser light to be less than 3 mm, moves the laser head and enlarges a heat input area to check for a crack in the heat input area, the heat input area being formed by irradiating the steel material with the laser light, and controls the laser head to irradiate a region where a temperature detected by the temperature sensor is equal to or less than a mechanical melting temperature of the steel material. Where a welding is performed in a flat position, the crack can be easily and reliably erased without causing burn through.