Peak current in Gas Tungsten Arc Welding (GTAW), also known as TIG welding, refers to the maximum amount of electrical current used during the welding process. This parameter is critical as it directly impacts the heat input, penetration, and weld bead width, making it a crucial consideration for achieving high-quality welds.
Understanding Peak Current in Pulsed GTAW
When using a pulsed GTAW process, the peak current is one of the four key welding parameters, along with background current, pulse width (duty cycle), and pulse frequency. The peak current is the maximum amperage during the pulse, while the background current is the minimum amperage between pulses. The pulse width is the percentage of time spent on the peak current, and the pulse frequency is the number of pulses per second.
Peak-to-Background Current Ratio
The peak-to-background current ratio is typically in the range of 2:1 to 5:1, and this ratio can be used to improve weld quality and output. A good starting point is to use a 3:1 ratio and then adjust the other parameters to see if any benefits can be gained.
Pulse Frequency and Pulse Width
The pulse frequency depends on the required spot overlap, with a good starting parameter being 75 percent spot overlap. The pulse width is dependent on the heat sensitivity of the material, with standard pulse widths ranging from 20 to 50 percent. A good starting point is to set a pulse width of 35 percent.
Impact of Peak Current on Welding Characteristics
Increasing the peak amperage increases the heat input, while increasing the pulse frequency narrows and concentrates the arc cone, increasing penetration and reducing the heat input. Pulsing can have the following effects:
| Characteristic | Improvement |
|---|---|
| Bead Width | Reduced by up to 52% |
| Penetration | Increased by up to 34% |
| Heat Input | Reduced by up to 60% |
High-speed pulsed GTAW also reduces the width of the heat-affected zone and provides more directional control over the weld, promoting better weld quality.
Optimizing Peak Current for Improved Welding
By understanding the relationship between peak current, background current, pulse width, and pulse frequency, welders can optimize their welding process to improve weld quality, increase weld speed, and reduce scrap and rework costs. This involves experimenting with different parameter combinations to find the optimal settings for the specific application and material being welded.
Conclusion
Peak current is a critical parameter in GTAW welding that significantly impacts the welding process and the resulting weld quality. By mastering the use of peak current and its relationship with other pulsed GTAW parameters, welders can unlock the full potential of this versatile welding technique and produce high-quality, efficient welds.
References
- Juggling the variables of GTAW – The Fabricator (https://www.thefabricator.com/thefabricator/article/arcwelding/juggling-the-variables-of-gtaw)
- TIG DC pulse settings – WeldingWeb (https://weldingweb.com/vbb/threads/30820-TIG-DC-pulse-settings)
- Determining parameters for GTAW Starting points for success – Pro-Fusion Online (http://www.pro-fusiononline.com/feedback/pwt-aug99.htm)
- Pulsed GTAW for stainless steel – The Fabricator (https://www.thefabricator.com/tubepipejournal/article/arcwelding/pulsed-gtaw-for-stainless-steel)
- GTAW pulse frequency and amplitude – American Welding Society Forum (https://app.aws.org/forum/topic_show.pl?tid=28597)
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