Laser Welded Piston Components with Segmented Power Density
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Solution Overview
Problem
The existing laser welding process for joining piston components in internal combustion engines often results in structural defects, such as cracks, due to incomplete welds at the start and end of circumferential laser weld seams, where power density is initially low and then reduced, leading to inadequate penetration and thermal stress during cooling.
Innovation Solution
A method combining deep welding and heat conduction welding, where the power density is gradually increased and decreased to create a deep weld seam, followed by heat conduction welding to ensure complete penetration and reduce thermal stress, thereby avoiding structural defects by using a locally limited heat conduction process to re-melt and solidify the material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous laser welding is used for joining piston components, then welding speed and productivity are improved, but structural defects such as cracks occur at the start and end areas due to insufficient power density during ramp-up and ramp-down
Solution Approach 1:
The continuous laser welding process is segmented into three distinct phases: a heat conduction weld phase at the start with lower power density to avoid defects, a deep penetration weld phase in the middle with high power density for efficient joining, and a heat conduction weld phase at the end with reduced power density. This segmentation allows each phase to be optimized independently, preventing structural defects while maintaining high welding speed in the critical middle section.
Solution Approach 2:
The laser power density is dynamically adjusted during the welding process rather than maintaining a constant value. The power density increases during the transition from heat conduction weld to deep penetration weld, then decreases during the transition to the final heat conduction weld. This dynamic adjustment prevents insufficient penetration at the start and end while maintaining high productivity in the intermediate section.
2Manufacturing precision
If high power density is used throughout the entire circumferential laser weld, then complete penetration is achieved, but thermal stress and structural defects increase due to excessive heat input at the start and end areas
Solution Approach 1:
Different power densities are applied to different sections of the weld path. The start and end areas receive lower power density (heat conduction welding) appropriate for their specific requirements, while the intermediate areas receive high power density (deep penetration welding) to ensure complete penetration. This local differentiation of welding parameters eliminates thermal stress and structural defects in the start/end zones while maintaining penetration quality in the critical intermediate sections.
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 the formation of structural defects, ensuring a strong and uniform laser weld seam that withstands thermal stress, and can be easily integrated into existing production processes without altering pre- or post-processing steps.
Implementation Method 1
activating a laser set up for a deep penetration welding process and aligning the laser beam generated by the laser to a defined starting point
Implementation Method 2
the material of the components is heated so intensely along the joining surfaces that the temperature in this area exceeds the vaporization temperature of the materials. This creates a vapor capillary surrounded by molten material
Implementation Method 3
In heat conduction welding, the materials of the components to be joined melt in the area of the joining surfaces exclusively by heat conduction, i.e., by absorption of the laser beam's energy solely in the area of the component surfaces
Implementation Method 4
After solidification, the molten material of both components joins them together
Data Source
Figure 1
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Figure 3~5
AI summary
The present invention relates to a method for producing a piston (10, 110) for an internal combustion engine having at least two piston components (11, 18; 111, 118), wherein at least two piston components (11, 18; 111, 118) are connected to each other along their corresponding abutting surfaces (23a, 24a, 23b, 24b) by at least one radially or axially circumferential laser weld seam (21, 22; 121, 122), said method having the following method steps: a) aligning the at least two piston components (11, 18; 111, 118) along their corresponding abutting surfaces (23a, 24a, 23b, 24b); b) activating a laser (25, 27) designed for a deep-welding method and aligning the laser beam (26, 28) emitted by the laser (25, 27) with a defined starting point (SP) in the region of the corresponding abutting surfaces (23a, 24a, 23b, 24b); c) increasing the power density (ramp-up) of the laser beam (26, 28) starting at the defined starting point (SP) for a defined length (S1) along the corresponding abutting surfaces (23a, 24a, 23b, 24b) to produce a ramp-up welding seam (31) with increasing welding seam depth; d) peripheral, complete welding along the corresponding abutting surfaces (23a, 24a, 23b, 24b) by means of deep welding to produce a deep welding seam (32) having a substantially constant welding seam depth up to the defined end point (EP); e) reducing the power density (ramping down) of the laser beam (26, 28) for a defined length (S2) to produce a ramp-down welding seam (33) with decreasing welding seam depth; f) welding at least a portion of the defined length (S1, S2) by means of heat conduction welding using a laser designed for a heat conduction welding method such that at least one heat conduction welding seam (34) is produced.