Resistance Spot Welding Heat Pattern Control Against Expulsion
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Solution Overview
Problem
Existing resistance spot welding methods fail to consistently achieve a stable nugget diameter without expulsion, especially when disturbances such as current shunting or sheet gaps occur, due to variations in electrode wear and complex heat generation patterns.
Innovation Solution
A resistance spot welding method involving three steps: forming a fusion zone with a minimum diameter of 2√t mm, cooling it to no more than 80% of its initial diameter, and then performing adaptive control welding based on target heat patterns derived from test welding, to ensure consistent heat distribution and prevent expulsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high welding current is set beforehand to compensate for current shunting, then nugget diameter requirement is met, but expulsion occurs due to excessive heat generation
Solution Approach 1:
The welding current is dynamically adjusted in multiple stages rather than using a fixed high current setting. The method applies different current levels (first current, second current higher than first, third current higher than second) at different time points during welding, allowing the system to adapt to changing thermal conditions and prevent excessive heat generation that causes expulsion while still achieving the required nugget diameter.
Solution Approach 2:
The welding process uses periodic current application with distinct phases: an initial current phase, followed by increased current phases at specific intervals. This periodic action with varying current magnitudes allows heat to be generated in controlled bursts, ensuring nugget formation without sustained excessive heat that would cause expulsion.
2Manufacturing precision
If welding current is increased to compensate for electrode wear, then nugget diameter is maintained, but heat distribution becomes unstable
Solution Approach 1:
The method dynamically adjusts current in response to electrode wear by implementing multiple current stages rather than simply increasing overall current. The first current is applied initially, then higher second and third currents are applied at specific times, creating a controlled temporal pattern that maintains stable heat distribution despite electrode degradation.
Solution Approach 2:
The welding process changes current parameters over time through distinct stages. By varying current magnitude and duration across multiple phases (first current < second current < third current), the method compensates for electrode wear effects while maintaining stable heat distribution patterns that produce consistent nugget diameters.
3Manufacturing precision
If high welding current is used to overcome sheet gap effects, then nugget diameter is sufficient, but heat loss increases and expulsion risk rises
Solution Approach 1:
The method uses periodic current application with varying intensities rather than continuous high current. By applying current in staged pulses (first, second, and third currents at different levels and durations), heat is generated efficiently at the weld point while minimizing overall energy loss and preventing the sustained excessive heating that leads to expulsion.
Solution Approach 2:
The welding current is dynamically modulated through multiple stages, applying higher currents only when and where needed during the welding process. This dynamic approach overcomes sheet gap effects at critical moments while minimizing total energy consumption and heat loss, preventing expulsion caused by excessive overall heat generation.
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 maintains a desired nugget diameter without expulsion even under significant disturbances, such as large sheet gaps or nearby existing welds, by aligning the heat pattern during adaptive control with the test welding conditions, thus preventing excessive heat generation and ensuring a stable weld.
Implementation Method 1
Heat generated from the resistance to the flow of the high welding current is used to obtain a spot weld
Data Source
Figure 1~2
AI summary
A resistance spot welding method of squeezing parts to be welded, which are a plurality of overlapping metal sheets, by a pair of electrodes and passing a current while applying an electrode force to join the parts to be welded comprises: a first step of passing a current by constant current control to form a fusion zone having a diameter of not less than 2√t, expressed in mm, between the metal sheets, where t, expressed in mm, is a sheet thickness of a thinnest metal sheet of the metal sheets; a second step of cooling the fusion zone to have a diameter of not greater than 80 % of D, where D, expressed in mm, is a diameter of the fusion zone formed in the first step; and a third step of performing adaptive control welding by controlling a current passage amount according to a target that is set.