Graphitization by silicon

Promotion of carbon precipitation as graphite instead of cementite in cast iron through the addition of silicon, thereby controlling ductility and castability.

Silicon in the weld metal is a strong graphitizer. It pulls the carbon out of the cementite bond and makes it soft as free graphite. If you have too much of it in the filler or base material, the weld becomes butter-soft and loses strength. So make sure you pick the right type and don't grab some silicon-rich filler for gray cast iron when you want to weld steel. Too much silicon can also cause blowholes and porosity in the weld.

MetallurgieSchweißtechnik