Bainitic Nodular Cast Iron Roll

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Introduction

Bainitic nodular cast iron roll is a kind of ductile iron roll and is a roll made by spheroidizing the molten iron with magnesium and pouring it into the sand-lined cold type. Due to the spheroidizing treatment, the graphite carbon inside the cast iron is changed from flake to spheroid, which eliminates the phenomenon of graphite tip stress concentration caused by flake graphite, which significantly improves the strength of cast iron, similar to the cast steel roll, but the abrasion resistance is much higher than the cast steel roll. There are three types of nodules of magnesium, cerium, and calcium and magnesium are commonly used. Spheroidal graphite iron roll can be applied in open-rolling mills, roughing mills and casting groove, high strength and excellent wear resistance.

Based on the analysis of the macro and microstructures of conventional Ni-Mo bainite ductile cast iron rolls used in bar finishing mills, we have found that the main cause of the spalling failure of the roll surface layer is the low bainite mass fraction in the roll structure, Irrational distribution of carbide morphology, and non-round graphite morphology.
On this basis, by optimizing the mass fraction of alloying elements of conventional bainite nodular cast iron composite rolls (nickel, copper, niobium composite alloying), the purpose of optimizing the structure and properties of the rolls is achieved. The structure of the improved roll is finer, and its carbide morphology has been significantly improved; meanwhile, the addition of alloying elements has significantly improved the bainite strength in the material, and its impact toughness, deflection, section shrinkage, and elongation after fracture are significantly improved compared with conventional Ni-Mo ductile iron, so it can significantly extend the service life of rolls and effectively reduce the production cost of steel.