Backup Rolls

Backup rolls are essential components in industrial metal rolling mills, particularly in four-high and cluster mill configurations. Positioned behind the smaller work rolls, these large-diameter rolls provide structural support to prevent work roll deflection under high rolling pressures. They transfer rolling forces from the work rolls to the mill housing while maintaining precise roll gap geometry, ensuring consistent product thickness and surface quality across the entire strip width.

Backup rolls are typically made from forged alloy steel or cast steel, with material grades such as 70Cr3Mo referenced in standards like GB/T 15547. They are available in a range of sizes and specifications to suit different mill applications. For instance, roll diameters typically range from 600 to 1600 mm, roll body lengths from 1500 to 3500 mm, and roll weights from 5 to 60 tons. Hardness values are usually between 50 and 90 HSD, and surface roughness is maintained between 0.2 and 0.8 μm Ra. Roundness and cylindricity tolerances are critical, typically 0.01–0.05 mm and 0.02–0.08 mm respectively, to ensure uniform rolling. Neck diameters range from 300 to 800 mm to fit bearing assemblies, with MORGOIL bearings commonly used. Maximum operating temperature is typically 200–300°C, and maximum rolling force capacity is 10–50 MN.

These parameters are reference ranges and must be verified for the specific model and application with the legal manufacturer or supplier. Backup rolls are selected based on mill configuration, strip width, rolling force requirements, and desired product quality. Proper maintenance and monitoring of wear, surface condition, and dimensional accuracy are essential to prevent failures and ensure consistent performance.

Backup rolls operate by counteracting the bending forces applied to work rolls during metal deformation. As the work rolls compress and shape the metal strip, they experience significant deflection forces. The backup rolls, being larger and more rigid, absorb these forces through their contact with the work rolls, maintaining proper roll alignment and preventing work roll bending. This mechanical support enables higher rolling pressures and wider strip processing without compromising dimensional accuracy.