Dual-Laser Dissimilar Metal Joining to Prevent Weld Cracking
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Solution Overview
Problem
Laser welding of dissimilar metal materials, such as iron and copper, often results in solidification cracking and a decrease in joint strength due to differences in melting point and thermal conductivity, leading to defects like segregation and the formation of intermetallic compounds.
Innovation Solution
A method involving the use of a first laser beam to melt the metals and a second laser beam with a larger diameter and lower power density to stir the metal structure near the joint, controlling the metal composition and preventing solidification cracking and intermetallic compound formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If laser welding is performed on dissimilar metal materials (e.g., iron and copper), then joining of the two metals is achieved, but solidification cracking occurs due to segregation of copper in the welded portion
Solution Approach 1:
The welding process is divided into two distinct stages: a first laser beam performs the primary welding to join the dissimilar metals, while a second laser beam performs subsequent stirring of the molten pool. This segmentation of functions allows each laser beam to be optimized for its specific task, preventing solidification cracking while achieving strong joints
Solution Approach 2:
The first laser beam performs preliminary welding to create the joint between dissimilar metals. After this preliminary joining is established, the second laser beam then stirs the molten pool to prevent segregation and solidification cracking. This sequential approach ensures the joint is already formed before the stirring action begins
2Strength
If laser welding is performed on dissimilar metal materials, then the metals are joined, but intermetallic compounds form that decrease joint strength
Solution Approach 1:
The welding process transitions from a static single-beam approach to a dynamic two-beam system where the second laser beam continuously stirs the molten pool during solidification. This dynamic stirring action prevents the formation of unstable intermetallic compounds by maintaining homogeneous metal composition throughout the welding process
Solution Approach 2:
The invention changes the parameters of the laser processing system by introducing a second laser beam with specific characteristics (larger beam diameter, lower power density) that differ from the first laser beam. This parameter change enables the stirring function that prevents intermetallic compound formation while maintaining the joining function
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 effectively prevents solidification cracking and the formation of intermetallic compounds, resulting in a stronger joint by reducing the concentration of metals at the weld interface and promoting a stable solid solution.
Implementation Method 1
forming a joint in which the first metal and the second metal are melted by performing scanning with a first laser beam
Implementation Method 2
stirring a metal structure near the joint by performing scanning, on a rear side in a scanning direction of the first laser beam, with a second laser beam
Data Source
AI summary
A laser machining method is a laser machining method for joining a first member containing a first metal and a second member containing a second metal different from the first metal, the method including a first step of forming a joint in which the first metal and the second metal are melted by performing scanning with a first laser beam, and a second step of stirring a metal structure near the joint by performing scanning, on a rear side in a scanning direction of the first laser beam, with a second laser beam having a beam diameter larger than a bean diameter of the first laser beam and having a lower power density than a power density of the first laser beam.