The physical properties of welding materials can impact weldability.
Material composition is a factor in the ability for the K-TIG Welding System to be able to open and sustain a keyhole weld. For example, high sulphur (S) levels have a destabilising effect on the weld.
Refer to your material data sheets and ensure that the S value for corrosive materials is <0.008% S, and for non-corrosive materials <0.003% S.