Laser Welding of Coated Steel Sheets Without Weld Bubbles
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Solution Overview
Problem
In laser welding of galvanized steel sheets, the vaporization of the cover material by the laser beam leads to bubble formation within the base materials, causing defects and requiring additional processing steps to remove the vapor.
Innovation Solution
A method where a laser beam is used to heat the cover material between two galvanized steel sheets to a temperature above its boiling point but below the melting point of the steel, creating a gap and allowing the vaporized cover material to be discharged outside, preventing it from mixing with the molten steel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the cover material is vaporized by laser beam heat, then the cover material is removed from the base material interface, but bubbles are formed inside the base materials due to vapor mixing
Solution Approach 1:
The patent applies preliminary action by heating the cover material to its boiling point and discharging the vapor through a gap formed between the base materials before the base materials are melted and welded. This sequence prevents the cover material vapor from mixing with the molten base materials, thereby avoiding bubble formation while ensuring complete removal of the cover material.
2Loss of substance
If a through hole is formed in the base materials to discharge vapor, then the vapor can be removed, but the welding process becomes more complex
Solution Approach 1:
The patent extracts the harmful vapor discharge function from the base materials by forming a gap between them. This gap serves as a dedicated discharge path for the cover material vapor, eliminating the need to create through holes in the base materials themselves. The vapor is discharged through this separately formed gap while the base materials remain intact for welding.
3Strength
If the laser beam heats the base material to melting point, then welding occurs, but the cover material vapor mixes with the molten base material causing defects
Solution Approach 1:
The patent applies preliminary action by completing the cover material vapor discharge through the gap before initiating the base material melting and welding process. This temporal sequencing ensures that when the base materials are heated to melting point for welding, the cover material vapor has already been removed from the interface region, preventing vapor mixing and bubble formation while maintaining weld strength.
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 effectively prevents bubble formation in the weld area, simplifies the welding process by eliminating the need for pre-drilled holes for vapor discharge, and ensures a cleaner weld by removing the cover material before the steel melts.
Implementation Method 1
heating a mating surface area of the first workpiece and the second workpiece, which corresponds to a heating area, to a temperature being equal to or higher than a boiling point of the cover material and lower than a melting point of the base material of the first workpiece; forming a gap between the first workpiece and the second workpiece by vaporizing the cover material in the mating surface area by the heating
Implementation Method 2
melting and welding the base materials of the first workpiece and the second workpiece to each other in the welding location by irradiating the welding location with the laser beam
Data Source
AI summary
In a method for laser welding of workpieces W1 and W2, a laser beam is generated and a workpiece W1 is irradiated. An irradiation point of the laser beam is swung within a predetermined heating area on the workpiece W1 encompassing a welding location where laser welding is to be executed, heating the mating surface area of the workpieces W1 and W2 corresponding to the heating area to a temperature higher than or equal to the boiling point of the coating material of the workpiece W2 and lower than the melting point of the base material of the workpiece W1, forming a gap between the workpieces W1 and W2 by vaporizing the coating material by the heating, discharging the coating material through the gap to the outside of the mating surface area, and melting and welding together the welding location of the base materials of the workpieces W1 and W2.