Graphitization Elements
Graphitizing elements like silicon or aluminum in cast iron promote the decomposing of cementite into free carbon (graphite) thermally and improve weldability.
Physical-Chemical Mechanism of Action
Graphitizing elements like silicon or aluminum lower the temperature at which cementite decomposes into free carbon (graphite). This happens by forming melt phases with lower graphite content.
Metallurgical Relevance & Welding Risks
Reducing cementite decomposition leads to a finer structure and improves weldability. However, too high a content of graphitizing elements can result in a too-soft, non-tough cast iron, which impairs mechanical behavior.
Workshop Practice & Action Guidelines
Use silicon or aluminum in cast iron alloys in the range of 0.1 to 0.5% for graphitization. Ensure the melting process is slow and controlled to achieve homogeneous distribution. If the graphitizing element content is too high, the strength of the cast iron can be reduced.