CO2 Flux-Cored Welding Waveform for Smaller Droplet Transfer
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Solution Overview
Problem
Conventional CO2 gas shielded arc welding processes, such as flux cored arc welding, result in large and chaotic molten metal droplets due to the repulsive force of CO2, leading to operability issues and spatter during the welding process, especially when using a parallel or dual wire configuration.
Innovation Solution
A system and method that involves superimposing pulses of current onto the welding waveform during the CO2 flux cored arc welding process to agitate molten droplets, promoting them to touch the weld pool sooner and preventing them from becoming too large, using a welding power source with a controller and feedback circuit to maintain average voltage and current characteristics, and employing CO2 as a shielding gas to create an upward force on the droplets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional constant voltage power sources and constant speed wire feeders are used in CO2 FCAW, then welding speed and portability are improved, but droplet size becomes large and chaotic leading to spatter
Solution Approach 1:
The patent applies periodic pulsed current superimposed on the base welding current to agitate molten droplets at regular intervals during their growth stage. This periodic action prevents droplets from becoming excessively large by disrupting their coalescence, thereby maintaining smaller, more consistent droplet sizes while preserving high welding speeds enabled by constant voltage power sources.
Solution Approach 2:
The pulsed current creates electromagnetic agitation that vibrates the molten droplets on the wire end. This vibration prevents the droplets from growing too large and chaotic, controlling their size and shape before transfer to the weld pool, thus resolving the contradiction between high productivity and droplet size control.
2Strength
If CO2 shielding gas is used to improve penetration and reduce cost, then welding penetration is improved and gas cost is reduced, but repulsive force pushes back molten droplets causing larger droplet formation
Solution Approach 1:
The pulsed current agitation is applied in advance during the droplet growth stage to counteract the CO2 repulsive force before it can cause excessive droplet enlargement. By agitating the droplets preliminarily, the system prevents the harmful effect of CO2-induced droplet growth, maintaining good penetration while improving droplet transfer control.
Solution Approach 2:
The patent changes the electrical parameters by superimposing pulsed current on the base current, creating time-varying current amplitude and frequency characteristics. This parameter modification alters the electromagnetic forces acting on molten droplets, enabling better control over droplet size and transfer behavior despite the presence of CO2 shielding gas.
3Manufacturing precision
If superimposed current pulses are used to agitate droplets and reduce size, then droplet size is reduced and transfer consistency is improved, but waveform complexity and control system requirements increase
Solution Approach 1:
The patent combines the base welding current and the pulsed agitation current into a single composite waveform generated by the welding power source. This merging of current components simplifies the control architecture compared to using separate systems, as the combined waveform is generated and controlled through the existing power source control circuitry.
Solution Approach 2:
The welding power source is designed to perform multiple functions: providing the base welding current for metal deposition and simultaneously generating the superimposed pulsed waveform for droplet agitation. This multi-functionality eliminates the need for additional dedicated pulse generation equipment, reducing overall system complexity while achieving precise droplet size control.
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 solution results in smaller molten metal droplets being transferred to the weld puddle, reducing spatter and improving the control and efficiency of the welding process by ensuring consistent and timely droplet transfer, thereby enhancing the overall operability and quality of the weld.
Implementation Method 1
The CO2 shielding gas constricts the welding output current as the welding output current leaves an end of a droplet of the molten metal droplets, creating an upward force on the droplet away from the weld puddle.
Implementation Method 2
Each current pulse of the superimposed welding current pulses generates an upward force on a droplet of the molten metal droplets away from the weld puddle.
Data Source
AI summary
An arc welding system providing improved molten metal droplet transfer. The system includes a welding power source having a welding power supply, a welding waveform generator, and a controller. Two fluxed cored welding wire electrodes are connected to the power source and are powered by the same welding output voltage and current produced by the power source. A feedback circuit is connected to the power source to provide an adaptive response to maintain an average welding output voltage. The controller controls the waveform generator and the power supply to superimpose welding current pulses onto a welding waveform of a CV flux cored arc welding process, that uses CO2 as a shielding gas, to generate a modified waveform of a modified CV flux cored arc welding process. The current pulses are superimposed in time to form molten metal droplets between ends of the two electrodes during the modified welding process.