Operation Taboos for Tungsten Inert Gas Welding

Avoid using the DC reverse polarity welding method

In argon arc welding, most metals (except aluminum, MAGnesium, and their alloys) are recommended to use direct current positive welding, where the workpiece is connected to the output  (+) and the tungsten electrode is connected to output  (-). This is because when the DC is connected in a positive direction, the heat generated by the anode (workpiece) is much greater than that of the cathode (tungsten electrode), making the tungsten electrode less prone to overheating and able to withstand larger welding currents, thereby achieving deep penetration welding and improving production efficiency. On the contrary, during DC reverse welding, the tungsten electrode becomes the anode, causing a significant increase in heat generation, which can easily lead to overheating and burn damage. Therefore, it is generally not recommended to use it.

Avoid using sharp conical tungsten electrodes

When the welding current is high, if a tungsten electrode with a small diameter and a sharp conical end is used, it will cause excessive current density, and the end of the tungsten electrode will melt due to overheating, increasing the risk of burning. At the same time, the arc spot will also extend to the conical surface at the end of the tungsten electrode, causing the arc column to expand and drift unstably, affecting the formation of the weld seam. Therefore, when welding with high current, a tungsten electrode with a thicker diameter should be selected, and its end should be ground into a blunt cone angle or a flat cone shape to maintain the stability of the arc and the quality of the weld.

Avoid using excessive welding speed

The welding speed is mainly determined by the thickness of the workpiece and is coordinated with parameters such as welding current and preheating temperature to ensure the desired depth and width of fusion. However, during high-speed automatic welding, if the welding speed is too high, it can cause severe backward deviation of the protective airflow, which may expose the tungsten electrode end, arc column, and molten pool to the air, thereby affecting the protection effect and reducing the quality of the weld. Therefore, when choosing welding speed, it is necessary to consider its impact on the gas protection effect and avoid using excessive welding speed.

Do not use airflow arbitrarily

The welding shielding gas for argon arc welding is argon, with a purity of 99.99%. When the welding current is 50~150A, the argon flow rate is 8~10L/min. When the current is 150~250A, the argon flow rate is 12~15L/min.

Under certain conditions, there is an optimal range of coordination between gas flow rate and nozzle diameter. For manual argon arc welding, when the flow rate is 5-25L/min, the corresponding nozzle diameter is 5-20mm. Beyond this range, if the airflow is too small or the nozzle diameter is too large, it will cause poor airflow stiffness, weak ability to remove surrounding air, and poor protection effect; If the airflow is too large or the nozzle diameter is too small, turbulent flow will be formed due to high airflow velocity, which not only reduces the protection range but also causes air to be drawn in, reducing the protection effect.

Avoid nozzle to workpiece distance being too large or too small

The distance from the nozzle to the workpiece directly determines the size of the arc cone ground and the state of gas protection. If the distance is too large, the effectiveness of gas protection will be greatly reduced, and the weld seam is easily invaded by air, thereby affecting the welding quality; If the distance is too small, it will not only obstruct the operating line of sight and increase the difficulty of operation, but also easily cause contact between the tungsten wire and the molten pool, resulting in tungsten inclusion defects and seriously damaging the performance of the weld. Therefore, in practical operation, it is necessary to strictly control the distance between the nozzle and the workpiece, and achieve the best gas protection effect as much as possible while ensuring good visibility and operational flexibility. Generally speaking, it is recommended to keep the distance between the nozzle top and the workpiece between 8-14mm, and not exceed 15mm, to ensure the stability of the welding process and the high quality of the weld seam.

Do not use the welding gun for exercise without permission

Flat welding is a relatively easy to master welding position, suitable for both manual and automatic welding. During welding, the position of the tungsten electrode and the workpiece should be accurate, the angle of the welding gun should be appropriate, and special attention should be paid to the stability of the arc and the uniformity of the welding gun movement speed to ensure that the penetration depth and width of the weld are uniform and consistent. When welding manually, it is advisable to use the left-hand welding method, and the welding gun should move uniformly in a straight line. In order to obtain a certain melting width, the welding gun is allowed to swing laterally, but should not jump. The diameter of the filling wire generally does not exceed 3mm