The slag density is significantly less than the metal density, in the radiographic picture slag inclusions look like relatively dark irregular-shaped sections. However, several coated welding electrodes form slags approximately of the same density as the metal density. Expectedly, in case of slag inclusions which are formed as a result of use of such electrodes it is highly difficult to detect them by means of radiography.
Tungsten inclusions are almost always formed as a result of TIG welding when a tungsten electrode is used for generation of arc. If the tungsten electrode comes into contact with molten weld pool, the arc can go out and molten metal is solidified at the stump ofelectrode. In the course of removal, the stump of electrode can get broken off and remain in metal of the completed weld if it cannot be removed by means of grinding.
The tungsten inclusions are also formed provided that the value of arc welding current, which is used at TIG welding, exceeds the recommended value for electrodes of this diameter. In this case the current density can be so high that the electrode begins to break down, and its fragments may get into the weld metal. A similar situation happens, when the welder has not ground the tungsten electrode tip thoroughly enough.
The tungsten inclusions are seldom detected at the weld surface, unless the welding inspector checks intermediate layers after ingress of tungsten. Main way of detection of tungsten inclusions consists in use of radiography method. Due to the fact that the density of tungsten significantly exceeds the density of steel and aluminium, tungsten will be shown in radiographic film in the form of a neatly-defined clear area.