Tungsten Electrodes Tip Shapes and Welding Current

Tungsten electrodes tip shapes can be flat, sharpened or rounded. Flat tip is cut by grinding wheel, molybdenum wire or machining. Sharpening is much more difficult. And both shapes and welding current will influence the life time of electrodes.

The grinding method of W electrode has an important influence on the stability of the arc, the life time of the electrode, and the shape of the weld. There are two methods: grinding in vertical and horizontal direction. The effect of horizontal grinding is better than that of vertical grinding, which is mainly reflected in the fact that horizontal grinding can prolong the life time of electrode and improve the quality of arc ignition to obtain a stable arc.

In addition to the influence of the texture of the W electrode tip on welding, the shape of the electrode tip is also an important process parameter of argon tungsten arc welding, which should be selected according to the type of current used. The angle of the tip of the electrode will affect its allowable current, arc ignition and arc stabilization performance. When welding with low current, the small diameter and cone angle of the tungsten electrode can make the arc start easy and the arc stable. When welding with high current, increasing the cone angle can avoid overheating and melting of the tip, reduce loss, and prevent the arc from expanding upward and affecting the stability of the cathode spot. The tip angle of the tungsten electrode also has an effect on the weld penetration depth and penetration width. Decreasing the taper angle will increase the penetration depth and decrease the penetration width. On the contrary, the penetration depth will decrease and the penetration width will increase.

The tip angle of the tungsten electrodes has the following regular practices:

1.0 Direct current welding below 200A, the front end angle of the electrode is 30~50 degrees, the arc blowing force is the strongest, and the penetration depth is the largest.

2.0 If the current exceeds 200A, the electrode temperature will be higher, and the arc blowing force will increase, and the protection status will deteriorate. The tip of the electrode forms an umbrella shape, but it can still maintain stable welding. The next welding needs to be re-ground and replaced.

3.0 When the current exceeds 250A, the front end of the electrode will produce melting loss. Before welding, the front end of the electrode will be ground out of a certain size platform.

4.0 The heat input of the tungsten electrode is large during DC reverse polarity and AC welding, and the current is not concentrated in a certain area of ​​the anode. At this time, it is most appropriate to grind the shape of the electrode tip into a round shape.

Besides the tip shapes, the suitable current can also influence the lifetime of electrodes. In argon tungsten arc welding, tungsten of a certain diameter has a certain range of welding current. Excessive current will cause the tungsten electrode to burn too quickly, and cause problems such as arc instability and tungsten in the weld. If the current is too small, the arc will be unstable, and defects such as incomplete penetration and lack of fusion will easily occur. The current carrying capacity of tungsten electrode is not only related to their chemical composition, but also affected by many other factors, such as welding torch type, electrode chuck polarity, electrode diameter, power source type, electrode length from the welding torch, welding position , Protect other properties, etc. The commonly used current can refer to the following table:

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