AC TIG Welding Cycles for Stable Arc and Deeper Penetration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing welding methods using non-consumable electrodes, particularly tungsten electrodes, face issues with arc instability and detachment due to the combination of AC and DC welding cycles, leading to poor welding quality, especially when working with materials prone to oxide formation like aluminum and magnesium alloys.
Innovation Solution
A method involving two alternating AC welding cycles with different parameters, where the polarity of the welding current changes at a welding frequency, with the second cycle having a lower positive polarity and higher negative polarity than the first, to stabilize the arc and improve degassing and penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If AC-DC welding cycles are combined to introduce heat into the workpiece, then heat input is improved, but arc stability deteriorates and electrode detachment occurs
Solution Approach 1:
The patent applies parameter changes by transitioning from AC-DC welding cycles to AC-AC welding cycles with different current amplitudes. The first AC cycle uses higher positive polarity current for oxide removal, while the second AC cycle uses lower positive polarity current and higher negative polarity current for stable heat input and penetration, eliminating the pinch effect and electrode detachment associated with DC cycles
Solution Approach 2:
The patent implements periodic action through alternating AC-AC welding cycles that repeatedly switch between two distinct AC welding modes. This periodic alternation between oxide removal phase (first AC cycle) and penetration phase (second AC cycle) maintains continuous arc stability while achieving both cleaning and heating functions
2Manufacturing precision
If AC welding current is used to break up oxide layer, then cleaning effect is improved, but penetration depth deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the welding process into two distinct AC cycles with different current parameters. The first AC cycle is dedicated to oxide layer removal with higher positive polarity current, while the second AC cycle focuses on penetration with higher negative polarity current, allowing each phase to be optimized independently
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the welding current parameters between the two AC cycles. The system transitions from a first AC cycle configuration optimized for cleaning to a second AC cycle configuration optimized for penetration, adapting the current amplitudes and polarities to match the immediate welding requirements
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 enhances arc stability, reduces pore formation, and achieves deeper penetration while minimizing electrode detachment, resulting in improved welding quality and process stability.
Implementation Method 1
an AC welding cycle is often combined with a DC welding cycle, in which a negatively polarized direct current is applied to the workpiece. This combines alternating polarity phases with phases of negatively polarized direct current.
Implementation Method 2
the arc burns between the end of the non-consumable electrode and the workpiece
Implementation Method 3
the alternating polarity of the welding current can break up the oxide layer
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a method and a device (1) for welding a workpiece (4) with a non-consumable electrode (2), in particular a tungsten electrode, wherein after the ignition of the arc (5) between the non-consumable electrode (2) and the workpiece (4), a welding process is carried out with two alternating welding cycles (Z1, Z2) with different welding parameters, wherein in the first welding cycle (Z1) a welding current (I) alternating in polarity with a predetermined welding frequency (fs1) is introduced between the non-consumable electrode (2) and the workpiece (4), and after a predetermined duration (tz1) of the first welding cycle (Z1) has elapsed, a change is made to the second welding cycle (Z2) for a predetermined duration (tz2).According to the invention, in the second welding cycle (Z2), a welding current (I) alternating in polarity with a welding frequency (fS2) is introduced between the non-consumable electrode (2) and the workpiece (4), wherein the welding current (I2+) with positive polarity in the second welding cycle (Z2) is lower than the welding current (I1+) with positive polarity in the first welding cycle (Z1), and the welding current (I2-) with negative polarity in the second welding cycle (Z2) is higher than the welding current (I1-) with negative polarity in the first welding cycle (Z1).