Globular Graphite Nucleation

The targeted formation of spherulitic carbon particles in cast iron melts through the addition of specific active nucleation elements to avoid lamellar shapes.

Nodular graphite forms when you add nucleating agents like silicon to the melt before casting. These ensure that the carbon precipitates as round nodules rather than as flakes. This makes the cast iron stronger and tougher. When welding, the problem is that the heat can destroy the microstructure again. If nucleation isn't right, you get hard, brittle spots or cracks. So when welding ductile iron, you must be careful and control cooling to prevent the graphite from reverting to the unfavorable flake form.

MetallurgieSchweißtechnik