Thermal Plasma Instability
Thermal plasma instability is an unwanted fluctuation in the arc plasma, triggered by pressure or gas flow changes, leading to uneven penetration. This can cause weld defects like distortion or porosity.
Physicochemical mechanism of action
The arc plasma has a high temperature and is unstable against small fluctuations in pressure or gas flow. These fluctuations can change the temperature distribution in the plasma, which in turn leads to uneven penetration.
Metallurgical relevance & welding risks
Uneven penetration can lead to distortion of the weld and to the formation of pores. These pores can impair the strength and toughness of the material, which can be particularly dangerous in highly stressed applications.
Workshop practice & action instructions
To avoid thermal plasma instability, pressure and gas flow must be kept constant. Regulation of the gas supply and precise control of the pressure in the welding tube are essential. If signs of uneven penetration occur, the gas supply and pressure should be carefully checked and adjusted.