In the fields of industrial manufacturing and automated welding, TIG Welding (Gas Tungsten Arc Welding) is widely utilized due to its exceptional weld quality. However, in practical operations, failure to strictly adhere to process specifications can easily lead to welding defects such as tungsten inclusions, porosity, and incomplete penetration. Below, we review the top ten core taboos in TIG welding operations to help you standardize your process flow and elevate your weld seam quality.
1. Strictly Avoid Direct Current Electrode Positive (DCEP)
In DC TIG welding, the heat at the anode is significantly higher than at the cathode. If DCEP (workpiece connected to the negative pole) is used, the tungsten electrode will suffer severe burn-off due to extreme overheating, resulting in an unstable arc and exceptionally shallow penetration. With the exception of welding aluminum, magnesium, and their alloys, the vast majority of metal materials should utilize Direct Current Electrode Negative (DCEN).
2. Square Wave AC Welding: Do Not Prolong the Negative Half-Wave Duration
Square wave AC TIG welding controls the cathode cleaning effect by adjusting the time ratio of the positive and negative half-waves. If the negative half-wave (cleaning action) ratio is too large, it can remove the oxide film but will exacerbate tungsten electrode burn-off and make the molten pool shallower and wider. It is recommended to use the minimum possible negative half-wave ratio while ensuring adequate cleaning effects.
3. Avoid Using Sharp, Thin Tungsten Electrodes for High-Current Welding
When the welding current is high, using an excessively thin or sharply pointed tungsten electrode causes the current density at the tip to be too high. This not only leads to the electrode tip melting and falling off (tungsten inclusion) but also causes arc wandering. For high-current operations, you must select a thicker tungsten electrode and grind its tip into a blunt taper or a flat top.
4. Shielding Gas Flow and Nozzle Diameter Must Be Properly Matched
Argon gas shielding is not “the higher the flow, the better.” If the flow is too high or the nozzle too small, the gas flow will change from laminar to turbulent, drawing air into the shielding zone and causing weld seam oxidation. Conversely, a flow that is too low results in inadequate shielding. Generally, the flow rate for manual TIG welding should be controlled at 5-25 L/min, corresponding to a nozzle diameter of 5-20 mm.
5. Beware of Excessively Fast Travel Speeds
Excessively fast welding travel speeds cause the argon shielding gas envelope to lag severely, leaving the high-temperature tungsten electrode, arc, and molten pool directly exposed to the air, thus losing the gas shielding effect. When configuring automated welding equipment or welding robots, special attention must be paid to matching an appropriate travel speed.
6. Precisely Control the Nozzle-to-Workpiece Distance
If the nozzle is too far from the workpiece, the effectiveness of the gas shielding is weakened; if it is too close, it obstructs the welder’s line of sight and makes it extremely easy for the tungsten electrode to touch the molten pool, causing short circuits and tungsten inclusions. It is generally recommended to keep the distance between the nozzle face and the workpiece at 8-14 mm (stand-off distance).
7. Strictly Avoid Scratch Arc Starting
Contact (scratch) arc starting directly contaminates the weld seam and severely burns the tungsten electrode. High-quality TIG welding should always employ a High-Frequency (HF) oscillator or high-voltage pulse arc strike to ensure maximum purity and stability at the moment of arc ignition.
8. Reject Oversimplified and Rough Welding Sequences
Standard TIG welding must include a complete sequence control loop: pre-flow, HF arc start, current up-slope, normal welding, current down-slope, and post-flow. The absence of preliminary argon shielding and current down-slope for crater filling makes the weld highly susceptible to porosity and crater cracks at the arc ignition and termination points.
9. Avoid Jumping Movements in Flat Position Welding
During flat position welding operations, the welding torch should maintain a uniform and smooth forward linear movement. Slight transverse weaving can be applied if necessary, but jumping or erratic movements are strictly prohibited. Jumping torch manipulation disrupts gas flow stability, resulting in highly uneven penetration depth and weld width.
10. Avoid Aluminum and Copper Filler Wires in Hot Wire TIG Welding
Due to the extremely low electrical resistivity of aluminum and copper materials, using them as filler wires in hot wire TIG welding requires a massive heating power source. This generates a severe magnetic arc blow phenomenon, leading to uneven melting of the base metal and seriously disrupting the stability of the welding process.
To learn more about the physical characteristics of tungsten electrodes, please refer to Baidu Baike: TIG Welding.