Graphite Rosette Morphology

Graphite rosettes are not something you need to worry about when welding normal steel. That belongs to the area of cast iron with spheroidal graphite, and it's about the structure in the base material, not the weld seam. When welding cast iron, the main problem is that the heat input can lead to hard, crack-prone zones. You should preheat the part and let it cool slowly to avoid stresses. If you're unsure which structure you have, ask before you start welding.