Steel Rolls 'as-cast' without heat treatment are not suitable for rolling. Dendritic structure, coarse grain, non-homogeneity and internal stresses make it poor in mechanical properties. So these rolls are subjected to precisely Comentite / Ferrite more evenly while retaining the basic Pearlitic structure so important to Alloy Steel Rolls.
Such rolls have higher strength at cost of hardness decrease compared to Chill or S G iron Rolls, making them suitable for heavier passes and severe stress in the roughing & intermediate stands. Nodular pearlitic rolls are widely used for hot rolling applications in different type of Roughing and Intermediate group stands. The material consists of graphite and carbides in pearlitic matrix.
Depending on the primary requirements (whether thermal shocks / cracks, crack penatrations or wear resisitance etc. ..) there are variety of Cr, Ni, Mo alloyed grades used considering the rolling mill operational conditions and groove / caliber design. The carbide content is relatively higher in alloyed grades compared with standard grades. Heat treatment improves the resistance to thermal cracks as well.
Nodular acicular rolls are widely used for hot rolling applications in different type of intermediate, prefinishing and finishing group stands. The material consists of nodular graphite and carbides in martensitic and bainitic matrix. SGAC rolls are more wear resistant than nodular pearlitic rolls.
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