In steel rolling production, rolling mill roll bearings are used to support rotating rolls and transmit rolling loads to the mill stand. As one of the most critical components in a rolling mill, roll bearings play a decisive role in operational stability, rolling accuracy, and equipment service life. Due to the demanding nature of steel rolling, roll bearings operate under highly specialized and severe conditions.
1. Heavy Loads Under Strict Space Constraints
During steel rolling, roll bearings are subjected to extremely high rolling forces and torque, often combined with impact loads. At the same time, mill design requirements usually limit the outer dimensions of the bearing housing, which must be smaller than the minimum roll body diameter. This structural constraint results in high unit load levels, placing stringent demands on the bearing’s load-carrying capacity and reliability.
2. Wide Range of Operating Speeds
Rolling mills operate across a broad speed spectrum, from low-speed roughing mills to high-speed finishing mills. In reversible rolling mills, roll bearings must also withstand frequent changes in rotational direction. As a result, bearings used in different rolling mills must be carefully selected according to operating speed, dynamic load conditions, and rotational characteristics to ensure stable performance.
3. Harsh Working Environment
In hot rolling and certain cold rolling processes, industrial lubricants such as emulsions or rolling oils are used to lubricate and cool the rolls and rolled products. Under high temperature and high-pressure conditions, these media may penetrate the bearing area. Therefore, rolling mill roll bearings must be designed with effective sealing and lubrication systems to maintain reliable operation in contaminated and thermally demanding environments.
Main Types of Roll Bearings Used in Rolling Mills
Based on their working principles, roll bearings used in steel rolling can be broadly classified into rolling bearings and plain bearings, each suited to specific rolling mill applications.
1. Rolling Bearings in Steel Rolling
Common rolling bearings used on rolling mill rolls include double-row spherical roller bearings, four-row tapered roller bearings, and multi-row cylindrical roller bearings. In special cases, needle roller bearings may be applied on work rolls.
Rolling bearings are characterized by high rigidity and relatively low friction, making them suitable for applications with significant load variations. However, their larger overall dimensions limit their use in certain compact mill designs. They are widely applied in strip rolling mills and billet continuous rolling mills where stable load transmission and operational reliability are required.
2. Plain Bearings and Their Applications
Plain bearings used in rolling mills can be divided into semi-dry friction bearings and hydrodynamic or hydrostatic bearings.
Semi-dry friction plain bearings, typically open-type resin composite bearings, are commonly used in section mills, billet mills, and roughing mills. In some small rolling mills, copper alloy or polymer bearings may also be applied. For stacked thin plate rolling mills, copper bearings are often used, with solid lubricants selected to accommodate high roll operating temperatures.
Hydrodynamic, hydrostatic, and hybrid hydrostatic–hydrodynamic bearings operate under full fluid-film lubrication. These bearings feature low friction coefficients, high operating speeds, and good stiffness, enabling high rolling accuracy. They are widely used on backup rolls in modern hot and cold strip rolling mills, as well as in other high-speed rolling mill applications.
