Laser Lap Welding Geometry for Corrosion-Resistant Coated Joints
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Solution Overview
Problem
Laser welding of coated components, such as galvanized steel sheets, often results in corrosion issues due to the evaporation and removal of zinc coatings during the process, leading to inadequate degassing and potential corrosion at the weld root, especially when the angular arrangement of components is insufficient for effective coating application.
Innovation Solution
The laser welding process involves directing the laser beam towards the joining zone during lap joint welding, creating a deep, curved weld root that fills the gap between the components, ensuring a sufficient gap width for corrosion coatings, without additional consumables, and maintaining the zinc coating integrity by controlling the energy input and geometry of the joining partners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If angular arrangement of components is used for laser welding, then degassing of coating is improved, but corrosion resistance deteriorates due to insufficient gap width for coating application
Solution Approach 1:
Instead of arranging components at an acute angle to each other (conventional approach), the patent inverts the approach by positioning components substantially parallel to each other with the laser beam incident at an acute angle. This inversion resolves the contradiction by maintaining adequate gap width for coating application while still enabling effective degassing through the gap during welding.
Solution Approach 2:
The patent changes the parameters of component arrangement from acute angle between components to substantial parallelism with angular laser beam incidence. This parameter change allows the gap to maintain sufficient width (enabling coating application) while the laser beam's angular incidence provides the necessary degassing pathway through the gap.
2Reliability
If additional coatings are applied to fill evaporated zinc coating areas, then corrosion resistance is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies preliminary action by ensuring adequate gap width is maintained during the welding setup phase, allowing corrosion protection coatings to be applied to the entire component surface including gap areas. This prevents the need for additional post-welding coating operations, thereby maintaining corrosion resistance without increasing manufacturing costs.
Solution Approach 2:
The patent converts the potential harm of zinc coating evaporation during welding into a benefit by designing the welding geometry (parallel component arrangement with angular laser incidence) to maintain adequate gap width. This allows the coating to be applied in advance to areas that would otherwise become uncoatable, turning a potential corrosion problem into an opportunity for comprehensive corrosion protection.
3Length of stationary object
If laser beam is directed at joining zone, then welding depth is improved, but zinc coating evaporation increases leading to corrosion
Solution Approach 1:
The patent applies local quality by directing the laser beam at an acute angle to the joining zone, concentrating energy locally to achieve deep weld penetration while the angular incidence and parallel component arrangement create a gap pathway that allows vapor escape. This localized energy application with controlled vapor discharge reduces zinc coating evaporation damage compared to perpendicular incidence.
Solution Approach 2:
The patent introduces a dimensional change by transitioning from perpendicular laser incidence to acute angle incidence, and from acute angle component arrangement to parallel arrangement. This dimensional change in beam geometry and component positioning enables deep welding while creating a three-dimensional gap pathway for vapor escape, reducing harmful zinc evaporation.
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 produces a homogeneous, deep weld that fills the gap, ensuring a minimum width of 0.2 mm for effective corrosion coating application, enhancing the corrosion resistance and reducing costs by eliminating the need for additional coatings and welding consumables, while maintaining the integrity of the zinc coating.
Implementation Method 1
A laser beam (7) is used to melt the joint to bond the two parts together
Implementation Method 2
The heat introduced by the laser beam into the joint of the joining flange of the first joining partner melts it section by section, thereby providing the melt introduced into the gap by the joint
Implementation Method 3
the zinc coating evaporates and is carried away in the area of the weld
Implementation Method 4
A laser beam is then used to melt the joint to bond the two parts together
Data Source
Figure 1~3
Figure 4a~4b
Figure 5a
AI summary
The invention relates to a method for the laser welding of two parts to be joined (1d, 2d), which are held against each other in a lap joint and are made of a metal material, the first part to be joined (1d) having a joining flange (3) with an end face, and the second part to be joined (2d) having a joining zone (6d) on a flat side, wherein, for the laser welding process, a side of the joining flange (3d) of the first part to be joined (1d) is held in contact with the joining zone (6d) of the second part to be joined (2d), there being a gap (10d) between the two parts to be joined (1d, 2d) which widens in the direction away from the side to which the laser is applied, and the laser beam (7) is directed, at an angle α of 1° to 45° to the plane of the joining zone (6d), into the throat formed by the joining zone (6d) and the joining flange (3d), and the welding is carried out such that the weld seam (12) which is formed extends into the gap (10d) and thus a gap bottom (SB) which spaces the mutually opposite surfaces of the parts to be joined (1d, 2d) is formed in the gap (10d).