Como escolher os parâmetros de soldagem Tig?

How to choose Tig welding parameters?

1. Welding current types and size

Generally, the type of welding current is selected based on the workpiece material. The size of the welding current is the most important parameter that determines the depth of weld penetration.

It is selected primarily based on factors such as workpiece material, thickness, joint shape, welding position, and sometimes even the skill level of the welder (when using tungsten inert gas welding).

2. Diameter and final shape of the tungsten electrode

The final shape of the tungsten electrode is an important process parameter. Different end shapes are chosen according to the type of welding current used.

The size of the tip angle α affects the allowable tungsten electrode current, arc initiation, and arc stability.

Table 1 lists the recommended current range for different tungsten electrode tip sizes.

Tungsten electrode diameter mm Tip diameter mm Tip angle
(°)		 Current/A
Constant current Pulse current
1.0 0.125 12 2-15 2-25
1.0 0.25 20 5-30 5~60
1.6 0.5 25 8-50 8-100
1.6 0.8 30 10-70 10-140
24 0.8 35 12-90 12-180
24 1.1 45 15-150 15-250
3.2 1.1 60 20-200 20-300
3.2 1.5 90 25~250 25-350

When welding with low current, using a tungsten electrode with a small diameter and a small cone angle can make the arc easy to ignite and stable.

When welding with high current, increasing the cone angle can prevent tip overheating and melting, reduce loss, and prevent the arc from extending upward and affecting the stability of the cathode point.

The angle of the tungsten electrode tip also has a certain influence on the depth and width of the weld. Reducing the cone angle reduces the depth of the weld and increases the width and vice versa.

3. Gas flow rate and nozzle diameter

Under certain conditions, there is an optimal range for gas flow rate and nozzle diameter that provides the best gas shielding and the largest effective shielding zone.

If the gas flow rate is too low, the air flow force will be weak and the ability to exclude the surrounding air will be weak, resulting in poor protection. If the flow rate is too high, it can easily become turbulent, causing air to enter and reducing the protection effect.

Similarly, when the flow rate is fixed, if the nozzle diameter is too small, the protection range is small and turbulence is formed due to the high speed of the gas flow.

However, if the nozzle is too large, it will not only obstruct the welder's observation, but also have low gas flow velocity, low resistance and poor protective effect. Therefore, the gas flow rate and nozzle diameter must be coordinated.

Refer to Table 2 for selection of portable gas tungsten arc welding nozzle opening and shielding gas flow rate.

Welding current
/A		 DC direct connection Direct reverse connection
Nozzle opening
mm		 flow rate
L/min		 Nozzle opening
mm		 flow rate
L/min
10-100 4~9.5 4-5 8-9.5 6-8
101-150 4~9.5 4-7 9.5-11 7-10
151-200 6-13 6-8 11-13 7-10
201~300 8~13 8-9 13-16 8-15
301-500 13-16 9-12 16-19 8-15

4. Welding speed

The selection of welding speed is mainly determined by the thickness of the workpiece and coordinated with the welding current, preheating temperature, etc. to ensure the required melting depth and width.

In automatic high-speed welding, the effect of welding speed on gas and shielding must also be considered. If the welding speed is too high, the shielding gas flow will be seriously delayed and the tungsten electrode tip, arc column and weld pool may be exposed to air.

Therefore, corresponding measures must be taken, such as increasing the shielding gas flow rate or tilting the welding torch forward at a certain angle, to maintain good protection.

5. Distance from nozzle to work

The greater the distance, the worse the gas protection effect. However, if the distance is too close, it may affect the welder's line of sight and easily cause the tungsten electrode to come into contact with the weld pool, resulting in the inclusion of tungsten.

Generally, the distance between the nozzle end and the workpiece is between 8 and 14 mm.

Table 3 lists reference welding parameters for tungsten inert gas welding of various materials.

Board thickness
mm		 Number of welding layers Tungsten electrode diameter mm Welding wire diameter mm Welding current A Argon flow rate
L/min		 Nozzle opening
mm		 Wire feed speed
cm/min
1 1 1.5-2 1.6 120-160 5-6 8-10 –
two 1 3 1.6-2 180-220 12-14 8-10 108-117
3 1-2 4 two 220-240 14-18 10-14 108-117
4 1-2 5 2-3 240-280 14-18 10-14 117-125
5 two 5 2-3 280-320 16-20 12-16 117-125
6-8 2-3 5-6 3 280~320 18-24 14-18 125-133
8-12 2-3 6 3-4 300-340 18-24 14-18 133-142

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