Technical Parameters in Argon-arc Welding

1. welding current’s type and value

    Welding current’s type is chosen mainly according to the workpiece’s material. The value of welding current will affect the depth of welding seam. In general, the value of welding current is related to the workpieces’ material, thickness, joint type, welding position, even the technology of welder (especially in tungsten argon-arc welding)

2. Tungsten electrode diameter and end shape

    The extreme shape of tungsten is an important technical parameter. Choose different end shapes based on the type of welding current used. The size of the tip angle α will affect the allowable current, arc initiation, and arc stability performance of the tungsten electrode in argon-arc welding.

Table 1 lists the recommended current ranges for different tip sizes of tungsten electrodes in argon-arc welding.

When welding with low current, using small diameter tungsten electrodes and small cone angles can make the arc easy to ignite and stable; During high current welding, increasing the cone angle can prevent the tip from overheating and melting, reduce losses, and prevent the arc from expanding upwards and affecting the stability of the cathode spot.   

The angle of the tungsten electrode tip also has a certain impact on the weld depth and width. Reducing the cone angle results in a decrease in weld depth and an increase in weld width. Conversely, reducing the cone angle leads to an increase in weld depth and a decrease in weld width.  

3. Gas flow rate and nozzle diameter

    Under certain conditions, there is an optimal range for gas flow rate and nozzle diameter, at which point the gas protection effect is optimal and the effective protection area is maximized.

    If the gas flow rate is too low, the stiffness of the airflow is poor, the ability to remove surrounding air is weak, and the protective effect is not good; Excessive flow can easily turn into turbulence, causing air to be drawn in and reducing the protective effect.

   Similarly, when the flow rate is sub timed, the nozzle diameter is too small, the protection range is limited, and turbulence is formed due to high airflow velocity; The nozzle is too large, which not only hinders the welder's observation, but also the airflow velocity is too low, the stiffness is small, and the protective effect is not good. So, there needs to be a certain coordination between gas flow rate and nozzle diameter.

   The selection of nozzle aperture and protective gas flow rate for manual argon arc welding is shown in Table 2.

4. Welding speed

    The value of welding speed is decided by the workpieces’ thickness and welding current, pre-heat temperature to guarantee the needed molten depth and width in argon-arc welding.

    In the hi-speed automatic argon-arc welding, the result of welding speed to gas and protection efficiency should be taken into consideration, too. If the welding speed is too high, protection gas flows too late, the end of tungsten, arc pillar and molten pool may be in the air. Therefore, relevant measures should be taken to increase the flow of protection gas or raise the torch to a certain angle.

5 Distance between nozzle and workpiece

    The greater the distance, the worse the gas protection effect. However, if the distance is too close, it will affect the welder's line of sight and easily cause a short circuit between the tungsten electrode and the molten pool, resulting in tungsten inclusions. Generally, the distance between the nozzle end and the workpiece is between 8-14mm.

    Table 3: Reference welding conditions for tungsten argon-arc welding of several materials.