Pulse Arc Welding Wire Feed Control for Spatter and Undercut
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Solution Overview
Problem
Conventional pulse arc welding methods face challenges in suppressing spattering and undercut during high-speed welding of mild steel, as they often result in high short-circuit currents and inadequate molten metal distribution, leading to poor weld quality.
Innovation Solution
The method involves controlling the feeding speed of the welding wire in synchronization with the switching between peak and base currents to maintain a constant arc length, reducing spattering by ensuring molten droplet transfer occurs in a spray state rather than short-circuit transfer, and adjusting the feeding speed to prevent undercut by maintaining a stable molten pool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If short-circuit transfer is used to enable high-speed welding, then welding speed is improved, but spattering increases due to high short-circuit current
Solution Approach 1:
The patent applies periodic pulse current with alternating peak and base periods to control molten droplet transfer. During the peak period, current increases to promote droplet detachment, and during the base period, current decreases to allow droplet formation. This periodic action enables controlled spray transfer at high welding speeds while preventing excessive short-circuit current and spattering.
Solution Approach 2:
The patent dynamically changes current parameters (peak current Ib1, base current Ib2, pulse frequency f) to maintain stable arc length and control droplet transfer mode. By adjusting these parameters, the system achieves spray transfer at high welding speeds without generating harmful spattering, resolving the contradiction between productivity and harmful factors.
2Manufacturing precision
If welding voltage is lowered and arc length is shortened to suppress undercut, then undercut is reduced, but short-circuit current increases leading to more spattering
Solution Approach 1:
The patent uses periodic pulse current to maintain short arc length for undercut suppression while controlling droplet detachment timing. The regular oscillation between peak and base currents ensures consistent arc length and prevents both undercut and spattering by avoiding uncontrolled short-circuit current spikes.
Solution Approach 2:
The patent employs feedback control to detect constriction (neck) formation in the molten droplet and adjusts current accordingly. When constriction is detected during the rising phase of short-circuit current, the system reduces current to prevent spattering while maintaining the short arc length necessary for undercut suppression.
3Object-generated harmful factors
If constriction control is applied to reduce spattering by sharply reducing current, then spattering is suppressed, but welding speed decreases
Solution Approach 1:
The patent implements periodic pulse current where the peak period promotes rapid droplet detachment and the base period allows controlled constriction formation. This regular cycling maintains high welding speed by ensuring frequent droplet transfer while suppressing spattering through controlled current reduction at appropriate moments in the cycle.
Solution Approach 2:
The patent performs preliminary droplet detachment during the peak current period before the base period begins. By detaching droplets in advance during the high-current phase, the system maintains high welding speed while the subsequent base period naturally reduces current to suppress spattering without requiring abrupt current interruptions.
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 effectively reduces spattering and suppresses undercut, achieving improved weld quality with a consistent arc length and stable molten pool, even at high welding speeds.
Implementation Method 1
generating an arc between the welding wire and the object by causing a welding current to flow through the welding wire
Implementation Method 2
melting the welding wire to form a molten droplet at a tip of the welding wire
Data Source
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AI summary
A pulse arc welding device is controlled so as to alternately repeat a peak current period in which a welding current is a peak current and a base current period in which the welding current is a base current smaller than the peak current, feed a welding wire to an object at a feeding speed while the welding current flows through the welding wire, generate an arc between the welding wire and the object, and weld the object. So as to keep an arc length of the arc to be constant, in the base current period, the feeding speed is set to a first feeding speed and, in the peak current period, the feeding speed is set to a second feeding speed which is larger than the first feeding speed and corresponds to the first feeding speed. By this method, good welding quality with reduced spattering and suppressed undercut can be obtained.