Resistance to Thermal Cracking
Strength and resistance to thermal cracking are the primary requirements for roughing rolls; the work rolls of small 20-high mills weigh only about 100 grams, whereas the backup rolls of wide, heavy-plate mills can exceed 200 tons. When selecting rolls, the base material capable of safely bearing the load (such as various grades of cast iron, cast steel, or forged steel) is chosen first based on the mill's fundamental strength requirements.
Hardness
In contrast, finishing rolls operate at higher speeds and must ensure specific surface quality for the final product; consequently, hardness and wear resistance are the primary requirements for them. Wear resistance is then considered. Because the wear mechanism of rolls is complex-involving mechanical stress, thermal effects during rolling, cooling effects, the chemical action of lubricants, and other factors-there is no single, unified metric for comprehensively evaluating roll wear resistance. However, since hardness is easily measured and can reflect wear resistance under certain conditions, a radial hardness profile is commonly used to approximate the roll's wear resistance characteristics.
Impact Resistance
Additionally, there are specific requirements for rolls; for instance, when heavy reductions are involved, the rolls must possess strong "bite" capability and high impact resistance.
Surface Finish
When rolling thin-gauge products, requirements regarding roll rigidity, uniformity of microstructure and properties, machining precision, and surface finish are particularly stringent.
Machinability
When rolling sections with complex profiles, the machinability of the roll body's working layer must also be taken into account.
