Temper Carbon Rosette

Temper carbon rosettes form when white cast iron is annealed and the carbon in the structure clumps into spherical or rosette-shaped accumulations. When welding malleable cast iron, this is a problem because the heat input can destroy this structure. The danger is that you locally get white cast iron again, which is hard and brittle and prone to cracking. If you must weld malleable cast iron, keep the heat input low and let the part cool slowly to avoid forming a hard, brittle structure.