Do you know how big is the impact on the weld?
Tungsten inclusion defect is a unique welding defect in TIG welding (tungsten argon arc welding). The harm of tungsten inclusion is to deteriorate the mechanical properties of the joint and reduce the service life of the welded structure. In argon arc welding of tungsten, due to some reasons, the tungsten electrode is strongly heated, and the debris that melts, evaporates or collapses in the weld becomes a high density inclusion, which is called tungsten inclusion. In the welding dictionary, the defect of tungsten inclusion is defined as the phenomenon that tungsten particles are mixed into weld metal during tungsten electrode inertia gas shielded welding. The image of tungsten clip on the weld photographic film is shown in figure 1. Because the geometry of tungsten inclusion is irregular, the sharp angle and edge corner can cut the weld, which is easy to cause stress concentration, which is one of the root causes of cracks, therefore, tungsten inclusion is a serious defect.
I. Factors affecting the tungsten defect of the welding seam The cause of tungsten defect in TIG welding is some records. In addition, according to the actual welding experience of the author and the data statistics of the welding test, the reason for the welding of the tungsten in the welding seam has the following aspects: 1. Effect of process factors It is generally considered that the process factors such as welding current, protective gas and tungsten extension length have a certain effect on the production of tungsten defects in TIG welding. 1) The welding current exceeds the bearing capacity of the tungsten electrode, leading to the overheating of the tungsten electrode and the tungsten particle caving in the molten pool. (2) The extension length of the tungsten electrode is too long, leading to the overheating of the tungsten electrode, melting or oxidation of the tungsten electrode, and entering the molten pool to form the tungsten clamp. (3) Poor protection, leading to the oxidation of the tungsten electrode. In general, that selection of the protective gas, the selection of the flow of the protective gas, and the disturbance of the external factors (outdoor air flow, etc.) result in the generation of the defects of the sandwich. (4) When the polarity of the DC TIG welding is not properly selected (DC reverse polarity) or the AC power is used for welding, the probability of tungsten clamping can be greatly increased.
2. Effect of operational factors In the manual welding process, due to the carelessness of the welding operation of the operator, the production of the tungsten-clamping defect can also be caused. According to the operation experience of TIG welding, the factors that lead to the defects of the tungsten clamp in the welding operation mainly include: (1) the tungsten electrode is in contact with a molten bath or a welding wire. In general, that tungsten electrode is easily brought into contact with the molten pool due to the operation technique, or the electrode is not firmly clamped by the electrode clamp, and the tungsten particles are easily brought into the molten pool when the TIG welding is in contact with the arc strike. (2) the splashing of the molten pool causes pollution to the tungsten electrode. The welding parts, such as poor cleaning, rust, dirt, etc., cause the splash to increase, and the splash metal and the tungsten come into contact with the tungsten and fall into the molten pool. (3) When the TIG welding is in contact with the arc, the tungsten electrode is directly contacted with the welding piece, and the tungsten clamp is easy to be generated. 3. The effect of the tungsten electrode material on the tungsten defect (1) the influence of tungsten electrode species In that same current condition, the tungsten-tungsten electrode is extremely low in tungsten, and the tungsten-like defect is very easy to occur. (2) the influence of the tungsten electrode taper When the cone angle of the tungsten electrode is large, it is not easy to clamp the tungsten. (3) Influence of the form of the tungsten electrode terminal And when the end part is a sharp corner, the fillet is more easily generated when the end part is rounded. (4) Quality of tungsten electrode In the case of cracking or cracking of the tungsten electrode if the quality problem occurs, it is also possible to cause the tungsten to fall into the weld pool during the welding process to cause the crack to occur. In addition, that surface of the tungsten electrode is too rough at the time of grinding, and the probability of the defect of the tungsten clip is increased.
