Short Arc Welding Feedback Control for Self-Shielded Electrodes
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Solution Overview
Problem
Existing short arc welding processes face instability and contamination issues, particularly in AC welding with cored electrodes, leading to porosity, cracking, and other defects due to atmospheric contaminants, and require external shielding gases which can be impractical in certain environments.
Innovation Solution
A novel short arc welding system and method that uses a feedback loop to control the melting pulse and short circuit timing, combined with a self-shielded flux cored arc welding (FCAW-S) electrode containing barium fluoride, lithium fluoride, and deoxidation agents, which stabilizes the arc at a short length, reducing contamination and eliminating the need for shielding gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If short arc welding is performed with cored electrodes in AC welding, then welding speed and productivity are improved, but arc stability deteriorates leading to porosity and cracking
Solution Approach 1:
The patent applies periodic pulsed current action to the welding process, where current is applied in discrete pulses rather than continuously. This allows the arc to be periodically reignited and controlled, improving stability while maintaining high welding speeds. The pulsed nature enables better control of heat input and arc behavior during AC welding with cored electrodes.
Solution Approach 2:
The patent implements feedback control by monitoring welding parameters and adjusting the pulsed current characteristics in response to detected conditions. This feedback mechanism maintains arc stability by correcting deviations in real-time, preventing porosity and cracking while preserving productivity gains from the pulsed welding approach.
2Reliability
If shielding gas is used to protect the weld pool, then weld quality is improved, but device complexity and cost increase
Solution Approach 1:
The patent employs self-shielding flux cored electrodes that generate their own protective atmosphere through flux decomposition during welding. The flux core releases gases that form a protective envelope around the weld pool, eliminating the need for external shielding gas systems. This self-service approach maintains weld quality while reducing device complexity and removing dependencies on external gas supply infrastructure.
3Ease of operation
If arc length is extended to improve accessibility, then ease of operation is improved, but contamination from atmospheric factors increases
Solution Approach 1:
The patent uses the flux core as an intermediary that creates a protective barrier between the weld pool and atmospheric contaminants. This flux-generated protective atmosphere acts as a mediator, allowing the arc to operate at longer lengths for better accessibility while still preventing contamination. The intermediary flux layer shields the molten metal from direct exposure to atmospheric factors even when arc length is extended.
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
The system achieves stable and strong welds with tensile strengths over 42.2 to 49.2 kg/mm² (60 to 70 ksi) without external shielding, minimizing contamination and enabling thinner pipe welding with improved arc stability and reduced material usage.
Implementation Method 1
the end of a consumable advancing electrode is melted by the heat of the arc during a current pulse
Implementation Method 2
the molten metal forms into a ball by surface tension action
Implementation Method 3
a self-shielded flux cored arc welding (FCAW-S) electrode containing barium fluoride, lithium fluoride, and deoxidation agents, which stabilizes the arc at a short length, reducing contamination and eliminating the need for shielding gas
Data Source
Figure 1~1A
Figure 2~3
Figure 4
AI summary
A welding system is disclosed for performing a short arc welding process between an advancing wire electrode and a workpiece. The system comprises a power source with a controller for creating a current pulse introducing energy into the electrode to melt the end of the electrode and a low current quiescent metal transfer section following the end of the melting pulse during which the melted electrode short circuits against the workpiece; a timer to measure the actual time between the end of the pulse and the short circuit; a device for setting a desired time from the pulse to the short circuit; a circuit to create a corrective signal based upon the difference between the actual time and the desired time; and, a circuit responsive to the corrective signal to control a given parameter of the current pulse. Also disclosed is a strategy for arc welding utilizing a cored electrode that produces welds with low levels of contaminants and which are strong, tough, and durable. The arc welding process generally utilizes an AC waveform. The cored electrode can be a self-shielded flux cored electrode (FCAW-S). Various electrode compositions are described that are particularly beneficial when used in conjunction with an AC waveform.