Trapezoidal Current Waveform for Arc Welding Slag Control
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Solution Overview
Problem
Arc start failures occur during gas shielded arc welding due to the formation of insulating slag at the end of the welding wire, which impedes the flow of short circuit current and prevents successful reinitiation of the arc.
Innovation Solution
The implementation of a trapezoidal waveform for the welding current during the termination step, which includes a first period of linear increase, a second period of constant current, and a third period of linear decrease, helps in positioning the slag away from the wire-end, preventing arc start failures by ensuring proper conduction when welding is resumed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding is terminated using conventional current control, then welding process is stopped, but slag concentrates at the end of the welding wire forming an insulating film that causes arc start failure
Solution Approach 1:
The patent applies preliminary action by implementing a specific current waveform (trapezoidal wave with linear increase, constant current, and linear decrease phases) during the welding termination step. This controlled current application before actual termination prevents slag from concentrating at the wire end, thereby eliminating the insulating film that would cause arc start failure when welding is restarted.
Solution Approach 2:
The patent changes the electrical parameter (welding current waveform) during termination from conventional constant or decaying current to a specific trapezoidal waveform with controlled rise and fall phases. This parameter change modifies the solidification behavior of the molten droplet, preventing slag segregation to the wire end and maintaining electrical conductivity for reliable arc restart.
2Productivity
If welding current is stopped immediately, then welding terminates quickly, but slag forms insulating film on wire end causing arc start failure
Solution Approach 1:
The patent implements preliminary action by applying a controlled current waveform during the termination phase that prevents slag concentration before the welding actually stops. The trapezoidal waveform with its specific time phases (linear increase, constant, linear decrease) ensures proper slag distribution while maintaining productivity through efficient termination.
Solution Approach 2:
The patent uses periodic action through the trapezoidal current waveform that cycles through distinct phases (current increase, constant current maintenance, current decrease) during termination. This structured temporal pattern ensures slag is properly positioned away from the wire end while maintaining controlled termination speed.
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 suppresses arc start failures by ensuring the slag is positioned away from the welding wire, allowing for consistent and reliable reinitiation of the arc, thereby improving the quality and productivity of the welding process.
Implementation Method 1
generating an arc with the welding current
Implementation Method 2
a droplet formed at an end of the welding wire is cooled and solidified
Implementation Method 3
a slag component and a solution component contained in the droplet are partly oxidized, and slag (metal oxide), which is an insulator, is formed
Data Source
AI summary
In an arc welding method of performing welding by employing CO2 gas as shield gas, supplying a welding current to flow between a welding wire and a workpiece to be welded while feeding the welding wire toward the workpiece, and generating an arc with the welding current, the arc welding method includes a welding step of performing the welding of the workpiece while executing control to adjust the welding current, and a welding termination step of executing control to apply the welding current having a trapezoidal waveform when the welding of the workpiece is terminated.