Tungsten Inclusion is the most occurring weld imperfection, mainly caused by the absorption of tungsten fragments in weld puddle. This problem is associated with tungsten inert gas welding process where an erroneous weld attempt with defected electrode may result in tungsten entrapment. Parameters like voltage, welding current, shield gas composition and even the welding modes must be rectified in order to achieve inclusion free welds. Because TIG is the most strenuous arc process and that is why, high level of skills are required to perform with. Below is the exposition of common reasons for weld tungsten inclusion and their practicable solutions.
- Holding the gun at a distance so that electrode may not have contact with weld puddle.
- The electrode must be away from the weld pool.
- Using high-frequency start-up mode, to fulfill the requirement and condition of above two steps.
Selection of gas composition for shielding is the foremost element in attaining quality welds. Gas shield prevents the entrapment of atmospheric gases that may react with the weld metal. Gas supplies not only protection but also helps to keep the arc stable. Normally inert gases argon, helium and argon-helium mixture are being used for their best results. Other compositions with other gases may also be applied but they don’t give such satisfactory results as compared to the inert gases. In order to achieve best quality results, it is recommended to adjust suitable composition of gases depending on the weldable material.
A nonfunctional electrode may also result in the entrapment of tungsten particles into the weld metal. The electrode cannot work effectively if it is not properly coupled with the torch. Same is the case when a damage electrode is inserted. Before fixing the electrode in torch, following are the points that must be considered;
- Make sure electrode has no fissure and small gaps on it.
- Electrode is properly ground
- Clamp the electrode tightly in the electrode.
Choice of electrode size for the specific job is chiefly dependent on welding current. Too higher the current for a given size of electrode, may induce problems. For this correct adjustment of current is recommended for given electrode size. Moreover too high stick-out can heat up the electrode and influence the outcome. So an electrode must be extended out at specified distance from the torch collet, according to the requirements.
- Tungsten Inclusion is typically caused due to manual mistakes by a welder.
- Welding inspector must check related points during qualification.
- Retrain the welder if not working well.
- Adjust the allowable welding current for specific electrode size.
- Ensure the correct placement of electrode in gun.
- Prevent any contact with electrode tip and avoid contamination.