Laser Lap Welding End-Point Scanning to Prevent Solidification Cracks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional laser lap welding methods often result in the formation of solidification cracks at the welding end point due to uneven metal solidification and tensile stress, leading to decreased joint strength and formation of sinks or holes.
Innovation Solution
The method involves linear laser scanning with controlled power reduction before the welding end point, followed by circular scanning around the axis extending in the depth direction of the workpieces to fluidize and mix the melted metal, preventing the concentration of tensile stress and formation of deep V groove-shaped sinks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If laser power is maintained constant during linear scanning from welding start point to welding end point, then laser power efficiency is enhanced, but a sink is formed at the welding end point and joint strength decreases
Solution Approach 1:
The patent applies dynamics by transitioning from constant laser power to dynamically adjusted power. The laser power is gradually reduced as the scanning approaches the welding end point, and the scanning speed is adjusted accordingly. This dynamic adjustment prevents the formation of sinks and solidification cracks at the welding end point while maintaining efficient energy utilization throughout the welding process.
Solution Approach 2:
The patent implements parameter changes by modifying both laser power and scanning speed parameters during the welding process. Specifically, as the laser beam approaches the welding end point, the power parameter is gradually reduced and the scanning speed parameter is adjusted to ensure proper solidification of the molten metal, thereby preventing defects and maintaining joint strength.
2Manufacturing precision
If laser power is gradually decreased before welding end point, then formation of holes at welding end point is reduced, but a long and thin welding bead is formed and solidification crack occurs
Solution Approach 1:
The patent applies periodic action through circular scanning at the welding end point. After completing the linear scan, the laser beam performs circular scanning movements around the welding end point area. This periodic circular action redistributes the molten metal uniformly, prevents the formation of long thin beads, and eliminates solidification cracks by ensuring even cooling and solidification throughout the weld zone.
3Productivity
If linear laser scanning is performed with constant power, then welding efficiency is maintained, but tensile stress concentrates and solidification crack forms at welding end point
Solution Approach 1:
The patent maintains welding efficiency through dynamic parameter adjustment. By gradually reducing laser power and adjusting scanning speed as the welding end point is approached, the process prevents solidification cracks while maintaining high productivity. The transition to circular scanning at the end point ensures reliable crack-free welding without significantly extending the overall welding time.
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 enhances joint strength by reducing the frequency of through-hole formation and prevents solidification cracks by uniformizing tensile stress during solidification, resulting in a stronger weld without deep V groove-shaped cracks.
Implementation Method 1
one side surface 3 of overlapped two workpieces (i.e., steel plates) 1 and 2 is linearly irradiated (scanned) with a laser beam L using a laser head 4
Implementation Method 2
locally melting the metal of the workpiece 1 (i.e., forming a melted metal 5a)
Implementation Method 3
The melted metal 5a adheres to the workpiece 2 through a gap d between the two workpieces 1 and 2
Implementation Method 4
the melted metal 5a pushed to the sink 6 sequentially solidifies from the outer part thereof
Implementation Method 5
circular laser scanning using the laser beam is performed around an axis extending in the depth direction of the workpieces through the welding end point using the laser beam to circularly melt and fluidize a portion of the workpieces around the welding end point
Implementation Method 6
circularly melt and fluidize a portion of the workpieces around the welding end point
Data Source
AI summary
A laser lap welding method is provided. The laser lap welding method includes linearly scanning one side surface of overlapped plural workpieces with a laser beam in a linear scanning range of from a welding start point of the one side surface to a welding end point thereof to weld the plural workpieces; controlling a power of the laser beam to gradually decrease until the laser beam reaches the welding end point when the laser beam reaches a laser power control point in the linear scanning range a predetermined time before the laser beam reaches the welding end point; and performing circular laser scanning using the laser beam around an axis extending in a depth direction of the plural workpieces through the welding end point after the laser beam reaches the welding end point to circularly melt and fluidize a portion of the plural workpieces around the welding end point.