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Effect of tungsten inclusion on weld line

Tungsten inclusion defect is a special defect in TIG welding. The harm of tungsten inclusion is that it deteriorates the mechanical properties of the joint and reduces the service life of the welded structure. Tungsten electrode argon arc welding, due to some reasons, so that the tungsten extremely intense heat, the tungsten extreme melting, evaporation, or tungsten pole collapse debris left in the weld into a high density inclusion, known as tungsten sandwich. The welding dictionary defines the tungsten inclusion defect as the inclusion of tungsten particles into the weld metal during gas tungsten arc welding.

Tungsten is a serious defect because of its irregular geom

etry, sharp angles and edges, which tend to cause stress concentration and are one of the root causes of cracks. Measures to control the defect of tungsten in weld seam

1. Select the welding current strictly according to the type and diameter of tungsten electrode.

Cerium - tungsten electrode is a good choice for low - current welding.

Lanthanum tungsten electrode is suitable for large welding current (I > 100A) and ac power welding selection. Lanthanum tungsten electrode in the case of large temperature difference is not easy to burst.

2. Strictly control the purity of inert protective gas (≥99.9%), and do not use Ar+O2 gas and Ar+CO2 gas for TIG welding.

3. During welding, the extension length of tungsten pole should be controlled. Generally, the extension length of tungsten pole should be kept at 5 ~ 6 mm during butt welding. When welding fillet weld, the tungsten pole length should be 7 ~ 8mm.

4. Dc TIG welding selects dc positive polarity.

5. Select a reasonable gas flow value; Windscreen shall be used for welding in outdoor windy places.

6. When welding, use short arc welding as far as possible to enhance the protection effect.

7. Use special grinding equipment to polish tungsten electrode; When welding with small current, the tungsten electrode is polished to produce small included Angle and sharp Angle. When welding with large current, the Angle should be polished to a large Angle and rounded Angle
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