Seam Welding Cycle Control for Crack Suppression
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Solution Overview
Problem
Existing seam-welding methods face challenges in increasing welding speed without causing cracks or spatter, as higher speeds risk molten portions solidifying inadequately or excessively cooling, leading to suboptimal product quality.
Innovation Solution
A seam-welding method that includes a melting period, a heating period with a current smaller than the melting current to solidify the molten portion, and an interruption period, allowing the molten portion to solidify under adequate pressure and temperature control, thereby increasing the solidification period proportion within the cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the relative speed of movement of the roller electrodes is increased to increase welding speed, then productivity is improved, but the roller electrodes may become separated from the molten portion before adequate solidification, causing cracks
Solution Approach 1:
The welding cycle is segmented into distinct phases: an energizing period for melting, an interruption period for solidification under pressure, and a heating period for temperature control. This segmentation allows each phase to be optimized independently, ensuring adequate solidification time even at high welding speeds.
Solution Approach 2:
The welding process uses periodic interruption of current supply to create cycles of melting and solidification. By intermittently stopping current during the interruption period, the molten portion solidifies under roller electrode pressure before the rollers move away, preventing cracks while maintaining high welding speed.
2Reliability
If the proportion of the interruption period is increased to hasten solidification, then crack formation is reduced, but the stacked assembly is subjected to excessive cooling, decreasing electrical resistance and requiring greater melting current
Solution Approach 1:
The heating period introduces a parameter change by applying a heating current after the interruption period to raise the temperature of the stacked assembly. This compensates for excessive cooling, maintains electrical resistance at appropriate levels, and reduces the melting current required in subsequent cycles.
Solution Approach 2:
The heating period ensures continuous temperature management by preventing excessive cooling of the stacked assembly. This maintains the material in an optimal temperature range for subsequent melting operations, ensuring process continuity and efficiency.
3Speed
If cooling water is used to cool the molten portion for prompt solidification, then solidification speed is improved, but additional cooling equipment and piping are required, increasing device complexity
Solution Approach 1:
The system uses self-service cooling by utilizing the stacked assembly itself and the roller electrodes as cooling elements. During the interruption period, the pressure applied by the roller electrodes and the natural heat dissipation to the stacked assembly provide sufficient cooling for solidification, eliminating the need for external cooling water systems.
Solution Approach 2:
The invention extracts the cooling function from external cooling water systems and integrates it into the welding process itself. The interruption period creates a natural cooling phase where heat is dissipated through the stacked assembly and roller electrodes, removing the need for separate cooling equipment.
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 enables high-quality seam welding at increased speeds by ensuring the molten portion solidifies under sufficient pressure and avoids excessive cooling, reducing spatter and cracking, without the need for additional cooling equipment.
Implementation Method 1
During the energizing period, resistance heating (Joule heat) is generated in the vicinity of contact surfaces of the workpieces that are pressed by the roller electrodes, and a molten portion is formed therein.
Implementation Method 2
during the interruption period, a location of the stacked assembly where the molten portion has been formed is cooled while being pressed by the roller electrodes, whereby the molten portion becomes solidified to form a nugget
Data Source
AI summary
This seam-welding device carries out seam welding while repeating one cycle comprising a melting period, an interruption period, and a heating period implemented either before or after the interruption period. A welding current is applied between a pair of roller electrodes so as to form a welded part between workpieces during the melting period, the application of the current between the roller electrode pair is interrupted so as to solidify the welded part during the interruption period, and a heating current smaller than the welding current is applied between the roller electrode pair so as to heat the laminated body within a solidification temperature range of the welded part during the heating period. Consequently, even when the welding speed is increased, formation of cracks and spatter is effectively suppressed such that a high-quality joined product is obtained.