Arc Welding Polarity Switching for Thin-Sheet Gap Filling
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Solution Overview
Problem
Conventional welding methods struggle to achieve high-quality welding of thin sheets with a relatively large gap in the weld joint, particularly in forming a bead with a small dilution ratio.
Innovation Solution
An arc welding control method that involves switching to electrode-negative polarity during the first arc period or at a delayed time from its start, with polarity switching occurring during the short-circuit period and controlling the welding wire feed direction to alternate between forward and backward, combined with specific current and voltage control strategies to manage heat input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional welding methods are used to weld thin sheets with a large gap, then the welding process can be performed, but the dilution ratio becomes large and penetration portion increases, resulting in poor welding quality
Solution Approach 1:
The patent applies periodic action by alternating between electrode-positive polarity and electrode-negative polarity in a cyclic manner. During electrode-negative polarity periods, the wire feeds backward to form larger droplets that fill the gap without excessive penetration. During electrode-positive polarity periods, the wire feeds forward to maintain arc stability. This periodic polarity switching enables high-quality welding of thin sheets with large gaps by controlling the dilution ratio.
Solution Approach 2:
The patent employs dynamics by making the wire feeding direction dynamic - switching between forward feeding and backward feeding based on the polarity state. The wire feeding speed and direction are adjusted in real-time according to the polarity switching, allowing the system to adapt to different welding conditions and maintain optimal droplet formation for gap filling with minimal penetration.
2Manufacturing precision
If high current is applied to form a bead with large reinforcement portion, then the gap can be filled, but heat input to the base material increases, causing poor welding quality on thin sheets
Solution Approach 1:
The patent uses periodic action by switching between electrode-positive polarity (higher heat input) and electrode-negative polarity (lower heat input) in controlled cycles. The electrode-negative polarity periods are extended to increase the time ratio, thereby reducing average heat input to the base material while still achieving adequate gap filling through the larger droplet formation characteristic of electrode-negative polarity.
Solution Approach 2:
The patent applies parameter changes by modifying the polarity switching frequency and the duration of each polarity period. By adjusting the time ratio between electrode-positive and electrode-negative polarity periods, the average heat input is controlled to an appropriate level for thin sheet welding, while the electrode-negative polarity periods enable larger droplet formation for effective gap filling.
3Productivity
If polarity switching is performed during the arc period, then the welding process continues, but arc instability occurs and spatter increases
Solution Approach 1:
The patent applies periodic action by switching polarity during the short-circuit period rather than during the arc period. This timing strategy allows the arc to remain stable during each polarity state, avoiding arc instability and spatter that would result from polarity switching during the arc period. The periodic switching during the short-circuit period maintains welding continuity while eliminating harmful spatter.
4Stability of the object's composition
If the wire is fed forward continuously to maintain arc stability, then the arc remains stable, but the droplet size is small and cannot fill large gaps
Solution Approach 1:
The patent employs dynamics by making the wire feeding direction variable - feeding backward during electrode-negative polarity periods to form larger droplets for gap filling, and feeding forward during electrode-positive polarity periods to maintain arc stability. This dynamic adjustment of wire feeding direction allows the system to achieve both large droplet formation and arc stability, which cannot be accomplished with continuous forward feeding alone.
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
Enables high-quality welding of thin sheets with a large gap by forming a larger droplet to fill the gap with low heat input, reducing spatter and ensuring smooth polarity switching.
Implementation Method 1
a short circuit stage with the welding wire and a base material being short-circuited
Implementation Method 2
a short circuit stage with the welding wire and a base material being short-circuited
Implementation Method 3
an arc stage with an arc being generated between the wire and the material
Implementation Method 4
switching to the electrode-negative polarity is made at a start of the first arc period or at a delayed time from the start of the first arc period
Implementation Method 5
repeating a cycle of applying a peak current and a base current during an electrode-positive polarity period
Data Source
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AI summary
An arc welding control method includes: feeding a welding wire (1); and repeating a short-circuit period and an arc period, where the arc period includes a first arc period and a second arc period following the first arc period. A welding current (lw) is applied using constant current control during the first arc period, and the welding current (lw) is applied using constant voltage control during the second arc period. The first arc period is set to an electrode-negative polarity, and a period other than the first arc period is set to an electrode-positive polarity.