Two-Step Laser Welding for Deep, Hot-Crack-Free Weld Seams
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Laser welding without welding material addition often results in hot cracks in weld seams when achieving depths greater than the critical welding-in depth, particularly in high-strength materials like high-strength steel and special aluminum alloys, due to tensile stresses that prevent complete solidification of the hardening melt.
Innovation Solution
A two-step laser welding method where the initial weld seam is formed to the target depth and then partially re-melted to the critical welding-in depth in a subsequent step, using either one or two laser heads with varying energy densities to heal cracks and reduce the welding-in depth, thereby eliminating hot cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If laser welding is performed without welding material addition to achieve deep weld seams, then welding-in depth is improved, but hot cracks form in the weld seam
Solution Approach 1:
The welding process is divided into multiple passes: a first welding pass creates the deep weld seam to the target welding-in depth, and subsequent welding passes treat the same region to heal hot cracks. This segmentation allows the process to achieve both deep penetration and crack-free weld seams by separating the melting function from the healing function.
2Reliability
If welding parameters are optimized to avoid hot cracks, then weld seam quality is improved, but welding-in depth is reduced below target depth
Solution Approach 1:
The first welding pass is performed with parameters optimized for deep penetration, accepting that hot cracks may form. Subsequent welding passes then apply different parameters optimized for healing these cracks. This preliminary action approach allows each pass to be optimized for its specific function rather than compromising both functions in a single pass.
3Reliability
If multiple weld tests are conducted to ensure crack-free weld seams, then weld seam quality is improved, but production time increases
Solution Approach 1:
The welding process itself performs the quality assurance function through multiple welding passes. The subsequent passes automatically heal the hot cracks created in earlier passes, eliminating the need for separate testing and rework operations. The process self-corrects defects rather than requiring external detection and repair.
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 allows for deeper welds without hot cracks, providing greater freedom in choosing welding parameters and maintaining productivity, ensuring weld seams are free of defects even in materials prone to hot cracking.
Implementation Method 1
the laser beam produced in the joint a weld seam with a target welding-in depth
Implementation Method 2
material in the joint is melted with the laser beam down to the target welding-in depth
Implementation Method 3
the weld seam produced in the first step is melted once again down to a welding-in depth which, as a maximum, corresponds to the critical welding-in depth
Implementation Method 4
the produced weld seam is melted once again
Data Source
AI summary
A description is given of a method for the laser welding of two parts to be joined (1) that are positioned in relation to one another, in which method the laser head, with the laser beam (9) emitted from it, and the two parts to be joined (1), with the joint (3) thereof, are moved in relation to one another in a feeding direction along the longitudinal extent of the joint (3) and the laser beam (9) produces in the joint (3) a weld seam with a target welding-in depth (8) which is deeper than the critical welding-in depth of the parts to be joined (1), wherein the welding method is performed in two steps and, to form the weld seam connecting the two parts to be joined (1), in a first step material in the joint (3) is melted by the laser beam (9) down to the target welding-in depth (8) and wherein, in a subsequent step, the weld seam produced by the first step is melted once again down to a welding-in depth which, as a maximum, corresponds to the critical welding-in depth of the parts to be joined (1). A description is also given of a welded construction (11) produced by this method.