Twin-Wire MIG Welding with Pulse Current for Arc Stability
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Solution Overview
Problem
Existing MIG welding methods face challenges in stabilizing the arc without requiring high currents, while also addressing issues of cost and welding quality, particularly when using 100% argon gas as the shield gas.
Innovation Solution
A MIG welding method utilizing a pair of MIG electrodes with individually variable currents, where a pulse current is passed through one electrode to generate a cathode spot in front of the molten pool for cleaning and then increasing the current through the other electrode to concentrate the cathode spot within the molten pool, allowing for stable and efficient welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 100% argon gas is used as shield gas with welding wire as positive electrode, then welding cost is reduced and welding quality is improved, but the cathode spot position becomes unstable and arc stability deteriorates
Solution Approach 1:
The patent applies periodic pulse current to the welding wire electrode, creating cyclic variations in current intensity. During the pulse peak, the cathode spot is attracted to and fixed on oxide inclusions on the wire surface, stabilizing the arc. During the pulse base period, the cathode spot detaches and moves to the workpiece surface, enabling cleaning action. This periodic modulation resolves the contradiction by making cathode spot position controllable and stable during welding while maintaining the benefits of 100% argon shielding.
Solution Approach 2:
The patent changes the electrical parameter by introducing pulse current with specific peak current values and duty cycles. By adjusting the pulse current parameters, the cathode spot behavior is controlled - at peak current the cathode spot stabilizes on wire surface oxides, while at base current it moves to clean the workpiece. This parameter change enables arc stability with 100% argon without requiring alternative gases or electrode configurations.
2Stability of the object's composition
If reverse polarity is used with oxide-forming element on welding wire, then cathode spot position is fixed and arc is stabilized, but welding wire cost increases
Solution Approach 1:
Instead of modifying the welding wire with oxide-forming elements (as in conventional reverse polarity methods), the patent creates a virtual oxide layer effect by applying pulse current to the unmodified wire. The pulse current causes temporary oxide formation or activates existing surface oxides only during the pulse peak, allowing cathode spot stabilization without permanent wire modification. This copying approach achieves the same effect as oxide-coated wires but without the additional material cost.
Solution Approach 2:
The patent extracts the oxide-forming function from the welding wire material itself and transfers it to the power supply system through pulse current control. Rather than incorporating oxide-forming elements into the wire composition, the system uses electrical parameters to create the necessary oxide layer temporarily during welding, eliminating the need for specialized expensive wires while maintaining arc stability.
3Stability of the object's composition
If reverse polarity is used to stabilize arc, then cathode spot is fixed, but metal penetration becomes insufficient and welding bead is shallow
Solution Approach 1:
The pulse current creates periodic cycles where during the peak current phase, the cathode spot is fixed on the wire for stable arc attachment and deep penetration welding. During the base current phase, the cathode spot moves to the workpiece for cleaning. This periodic action allows the system to achieve both deep penetration (when cathode is on wire) and surface cleaning (when cathode is on workpiece), resolving the contradiction between arc stability and penetration depth.
Solution Approach 2:
The patent makes the cathode spot position dynamic rather than fixed - it moves between wire surface and workpiece surface according to the pulse current cycle. During the pulse peak, the cathode spot is dynamically positioned on the wire for deep penetration; during the base period, it dynamically moves to the workpiece for cleaning. This dynamic positioning resolves the contradiction by providing both stable arc attachment and adequate penetration depth.
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 stabilizes the arc without needing high currents, achieves low-cost, high-quality, and highly wettable welding, and ensures efficient droplet transfer using consumable electrodes.
Implementation Method 1
an arc of a first MIG electrode of the pair of MIG electrodes generates a cathode spot in front of the molten pool in a moving direction, and the arc removes an oxide on a surface of the metal member to be welded
Implementation Method 2
passing a pulse current having a higher current value than that of the first MIG electrode through a second MIG electrode of the pair of MIG electrodes, so that cathode spots are each generated within the molten pool to newly form a molten pool
Data Source
AI summary
Two welding wires whose current values are individually variable are placed along a groove of steel plates, and two operations are repeated, the first operation including: passing substantially the same current through both welding wires; generating a cathode spot in front of a molten pool by one welding wire's arc on a welding-direction forward side; and cleaning the steel plates' surfaces by the arc, and the second operation including: passing a pulse current having a higher value than that of the welding wire through the other welding wire, so that a cathode spot is generated in the molten pool by each welding wire's arc to newly form a molten pool; and advancing both welding wires in the welding direction to move the cathode spot to the newly-formed molten pool, and at the same time performing welding within an area where oxides on the steel plates' surfaces are removed.